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Sample records for chinese loess plateau

  1. Loess magnetic properties in the Ili Basin and their correlation with the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    NAOTO; Ishikawa

    2010-01-01

    Over the past two decades, magnetoclimatological studies of loess-paleosol sequences in the Chinese Loess Plateau (CLP) have made outstanding achievements, which greatly promote the understanding of East Asian paleomonsoon evolution, inland aridification of Asia, and past global climate changes. Loess magnetic properties of the CLP have been well studied. In contrast, loess magnetic properties from outside the CLP in China have not been fully understood. We have little knowledge about the magnetic properties of loess in the Ili Basin, an intermontane depression of the Tianshan (or Tien Shan) Mountains. Here, we present the results of rock magnetic measurements of the Ili loess including mass magnetic susceptibility (χ) and anhysteretic remanent magnetization (ARM), high/low temperature dependence of susceptibility (TDS) and hysteresis, as well as X-ray diffraction (XRD) for mineral analysis. Based on the comparison with loess-paleosol sequences in the CLP (hereafter referred to as the Chinese loess), we discuss the possible magnetic susceptibility enhancement mechanism of the Ili loess. The results show that 1) the total magnetic mineral concentration of the Ili loess is far lower than that of the Chinese loess, though they have similar magnetic mineral compositions. The ferrimagnetic minerals in the Ili loess are magnetite and maghemite, and the antiferromagnetic mineral is hematite; XRD analysis also identifies the presence of ilmenite. The ratio of maghemite is lower in the Ili loess than in the Chinese loess, but the ratios of magnetite and hematite are higher in the Ili loess than in the Chinese loess. 2) The granularity of magnetic minerals in the Ili loess, dominated by pseudo-single domain (PSD) and multi-domain (MD) grains, is generally much coarser than that of the Chinese loess. Ultrafine pedogenically-produced magnetic grains have a very limited contribution to the susceptibility enhancement. Rather, PSD and MD particles of magnetite and maghemite are

  2. Transformation relationship among different magnetic minerals within loess-paleosol sediments of the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The dominant magnetic minerals and carriers of magnetic signals within the Chinese Loess Plateau are magnetite, maghemite, hematite, and goethite. In this study, we investigated the provenance and evo- lution of magnetic minerals during loess pedogenesis, using X-ray diffraction (XRD) and optical and electron microscopy, including field emission scanning electron microscopy (FESEM) and high- resolution transmission electron microscopy (HRTEM). Our results reveal that single- and multiphase mineral assemblages among magnetic minerals in the loess-paleosol sequence have been formed. Partial oxidation of coarse eolian magnetite has occurred in the desert source area and the oxidation degree is enhanced after deposition of the dust upon the Chinese Loess Plateau. This mode of origin resulted in a microtexture consisting of an inner magnetite core surrounded by a hematite rim, and strongly affected the magnetic characteristics of the loess. Goethite coexists with hematite in the loess and paleosol, and nanometer-scale hematite is formed upon goethite rims via dehydration. Our study provides direct mineralogical evidence of the magnetic record and paleoclimatic implications of the loess–paleosol sequence of the Chinese Loess Plateau.

  3. Transformation relationship among different masnetic minerals within loess-paleosol sediments of the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    XIE QiaoQin; CHEN TianHu; XU XiaoChun; QING ChengSong; XU HuiFang; SUN YuBing; JI JunFeng

    2009-01-01

    The dominant magnetic minerals and carriers of magnetic signals within the Chinese Loess Plateau are magnetite,maghemite,hematite,and goethite.In this study,we investigated the provenance and evolution of magnetic minerals during loess pedogenesis,using X-ray diffraction (XRD) and optical and electron microscopy,including field emission scanning electron microscopy (FESEM) and highresolution transmission electron microscopy (HRTEM).Our results reveal that single-and multiphase mineral assemblages among magnetic minerals in the Ioess-paleosol sequence have been formed.Partial oxidation of coarse eolian magnetite has occurred in the desert source area and the oxidation degree is enhanced after deposition of the dust upon the Chinese Loess Plateau.This mode of origin resulted in a microtexture consisting of an inner magnetite core surrounded by a hematite rim,and strongly affected the magnetic characteristics of the loess.Goethite coexists with hematite in the loess and paleosol,and nanometer-scale hematite is formed upon goethite rims via dehydration.Our study provides direct mineralogical evidence of the magnetic record and paleoclimatic implications of the Ioess-paleosol sequence of the Chinese Loess Plateau.

  4. Reworked loess and Yellow River sediment as the main sources of the Chinese Loess Plateau

    Science.gov (United States)

    Licht, Alexis; Pullen, Alex; Kapp, Paul; Abell, jordan; Giesler, Dominique

    2016-04-01

    The Quaternary aeolian dust deposits of the Chinese Loess Plateau have been attributed to spring and winter monsoonal storms sweeping clastic material from the deserts of the Asian interior into central China. Recent U-Pb geochronological studies of aeolian zircons have emphasized the existence of two major wind pathways: from the north, throughout the Tengger, and Mu Us deserts during interglacials, and from the west, through the Qaidam Basin during glacials. Others have emphasized the importance of Yellow River supply in the Loess Plateau sediment budget. However, tracking dust source regions through U-Pb dating is particularly complex, given the paucity of data in many potential sources regions and the similar ages peak in the age probability distributions of western and Northern deserts in central China. Here, we present an extended dataset of U-Pb ages covering all the potential provenance areas for the aeolian dust in central Asia and including 2400 new ages from loess, paleosols, modern sand dunes and fluvial deposits. We then propose a new mixture modeling technique to statistically address the contribution of these different sources to the Loess Plateau sedimentary budget. Our contribution estimates indicate that aeolian supply is dominated (60-70 %) by reworking of Yellow River sediment. Moreover, evidence of Qaidam Basin sourced zircons (15-20 %) in both loess (glacial) and paleosols (interglacial) layers corroborates the existence of an erosive wind pathway from the west during glacials and implies that a substantial portion of the interglacial dust is recycled from older glacial loess. We propose that sediment reworking of Yellow River sediment and older loesses by wind homogenizes aeolian zircon populations on the Chinese Loess Plateau toward a glacial provenance due to higher dust accumulation rates during glacials. These findings indicate that the Loess Plateau has evolved as a more dynamic landform than previous thought where wind deflation

  5. Magnetic properties of Jiaxian red clay sequences from northern Chinese Loess Plateau and its paleoclimatic significance

    Institute of Scientific and Technical Information of China (English)

    QIANG; Xiaoke; AN; Zhisheng; LI; Huamei; CHANG; Hong

    2005-01-01

    Detailed rock magnetism investigation of the Jiaxian red clay sequences indicated that there are common magnetic mineralogy properties in red clay and loess-paleosol sequences from the Chinese Loess Plateau as well as the marked properties of themselves, magnetic minerals mainly with magnetite, maghemite, hematite, and possibly limonite/goethite contributing to the magnetic behavior. Meanwhile, it is found that the strong paleosol in red clay sequences has a lower coercivity and higher content of ultra-fine ferrimagnetic grains than that of the weak paleosol, which is similar to loess and paleosol in upper Wucheng Loess sequences, and indicates that humid conditions and relatively strong pedogenesis play a significant role in the increase of ultra-fine magnetic minerals and transformation of the magnetic minerals. This suggests that, like Quaternary loess-paleosols, the change of characteristics of paleoclimatic conditions of the late Tertiary red clay deposits is fluctuant. In addition, the results of magnetic hysteresis properties show that the applied saturated field for samples from the Jiaxian red clay sequences is higher than that of the samples from eastern and southern Chinese Loess Plateau. It is obviously shown that there exist more hard magnetic minerals and relatively weak biochemical processes in the Jiaxian red clay sequences on northern Chinese Loess Plateau. We conclude that the paleoclimatic environment is different between northern and eastern/southern Chinese Loess Plateau, and it should be more arid in northern Chinese Loess Plateau.

  6. Consequences of hyperconcentrated flow for process-based soil erosion modelling on the Chinese Loess Plateau

    NARCIS (Netherlands)

    Hessel, R.

    2006-01-01

    High sediment concentrations in runoff are a characteristic feature of the Chinese Loess Plateau, and are probably caused by factors such as the occurrence of erodible materials on steep slopes, the characteristics of the loess and the harsh climate that results in low plant cover. When sediment con

  7. Rock magnetic properties of a loess-paleosol couple along an N-S transect in the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We have conducted detailed rock magnetic experiments on samples from loess unit 8(L8) and paleosol unit 8 (S8) in Jingbian, Yichuan and Duanjiapo loess sections along an N-S transect in the Chinese Loess Plateau. Major rock magnetic results are as follows: ( i ) An increase of high field susceptibility (χh) in the same level of loess or paleosol from north to south is observed, suggesting an enhancement of pedogenesis. (ii) The Iow field susceptibility (χL) in loess unit L8 is almost the same in three sections. In contrast, the χL of paleosol unit S8 in Yichuan is highest, and the χL of Duanjiapo is lower than that in Yichuan section, suggesting that there is not correlation between the χL and the degree of pedogenesis in loess-paleosols. (iii) With the increasing of χL, both the contents of the superparamagnetic (SP) and the ferrimagnetic grains in Ioess-paleosol increase, however, the enhancement of magnetic susceptibility is probably dependent more on the increase of the ferrimagnetic concentration than on a change in the grain size. (iv) The content of the maghemite in loess unit 8 increases from the northern to the southern part of the Chinese Loess Plateau, and is positively correlated with the pedogenesis of the loess.

  8. The dominance of loess weathering on water and sediment chemistry within the Daihai Lake catchment, northeastern Chinese Loess Plateau

    International Nuclear Information System (INIS)

    Highlights: • Firstly highlight the importance of loess weathering in a semi-arid lake. • Loess weathering controls sediment compositions in loess-covered area. • Loess weathering results in similar water chemistry of rivers and groundwater. • Water draining loess areas has distinct Mg/Ca and 87Sr/86Sr from global rivers. - Abstract: This study investigated modern loess weathering and its control on the chemistry of surface water and sediment within the Daihai Lake catchment. The mineral types and the abundances of major and trace elements in loess, sediments and bedrocks were determined to ascertain the provenance of river sediment. The major cation compositions and Sr isotopic ratios of surface and subsurface waters were measured to distinguish the contributions of dissolved loads from various parent materials. The data show that mineralogical characteristics and elemental abundances of the river sediments are almost identical with those of the loess, but are different from the bedrocks, indicating that river sediments are predominantly derived from loess. River waters feeding Daihai Lake show a similar range in 87Sr/86Sr ratios as those of HOAc-soluble carbonate minerals in loess from the Chinese Loess Plateau. The slightly lower 87Sr/86Sr of river waters in the southern catchment relative to other rivers reflect potential weathering of large areas of outcropping basalt. These results imply that (1) surface processes are dominated by weathering of loess which only accounts for 18% of the total catchment area, and (2) loess weathering but not basalt controls the river Sr isotopic signature, although the latter covers a larger catchment area. For groundwater, 87Sr/86Sr ratios indicate that subsurface processes might be controlled by interactions with ambient lithology and hydrological flowpaths. Comparing the rivers draining the Chinese Loess Plateau with global rivers, both Mg/Ca and 87Sr/86Sr in the Daihai surprisingly agree well with those in the upper

  9. Tetraether biomarker records from a loess-paleosol sequence in the western Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    Guodong eJia

    2013-07-01

    Full Text Available The ubiquitous occurrence of glycerol dialkyl glycerol tetraethers (GDGTs in soils and their ability to record temperature and environmental changes offer the prospect of independently reconstructing continental paleotemperature and paleoenvironment from the loess-paleosol sequences (LPS from the Chinese Loess Plateau (CLP. In this study we present records of GDGT-derived proxies for the last 70 kyr from the Yuanbao LPS, western CLP. Temperature record reconstructed from the cyclization and methylation index of branched tetraethers (MBT-CBT displays that the onset of deglacial warming at ~20 kyr before present (BP precedes the strengthening of summer monsoon at ~15 kyr BP, which is in agreement in timing with previous MBT-CBT temperature records from the southeastern CLP. The maximal deglacial warming of ~10 °C is slightly higher than those in the southeastern CLP, perhaps due to the higher latitude and farther inland of the study site. The Branched and Isoprenoid Tetraether (BIT index shows higher values (0.87–0.96 range, 0.93 average in the glacial loess and lower values (0.76–0.91 range, 0.83 average in the Holocene paleosols, with a steady decreasing trend since the early Holocene. The decreasing trend could suggest enhanced Thaumarchaeota relative to GDGT producing bacteria activity since the early Holocene, but other possibilities, such as preferential degradation of isoprenoid GDGTs or upward increase in living archaea relative to bacteria in the paleosol profile, cannot be fully excluded. Our results thus demonstrate the need of future study on microbial community structure in soil column and differential degradation of GDGT molecules.

  10. A comparison of heavy mineral assemblage between the loess and the Red Clay sequences on the Chinese Loess Plateau

    Science.gov (United States)

    Peng, Wenbin; Wang, Zhao; Song, Yougui; Pfaff, Katharina; Luo, Zeng; Nie, Junsheng; Chen, Wenhan

    2016-06-01

    QEMSCAN-based (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) heavy mineral analysis has recently been demonstrated an efficient way to allow a rapid extraction of provenance information from sediments. However, one key issue to correctly obtain a provenance signal using this technique is to clearly separate effects of diagenetic alteration on heavy minerals in sediments, especially in fine-grained loess. Here we compare heavy mineral assemblages of bottom Quaternary loess (L33) and upper Pliocene Red Clay of three sites on the Chinese Loess Plateau (CLP). Two sites (Chaona and Luochuan) with similar modern climate conditions show similar heavy mineral assemblages but contain much less of the unstable heavy mineral amphibole than the drier Xifeng site. This result provides strong evidence supporting that climate-caused diagenesis is an important factor controlling heavy mineral assemblages of fine-grained loess. However, heavy mineral assemblages are similar for loess and paleosol layers deposited after 0.5 Ma on the Chinese Loess Plateau regardless of climate differences, suggesting that time is also a factor controlling heavy mineral assemblages of loess and Red Clay. Our high resolution sampling of the upper Miocene-Pliocene Chaona Red Clay sequence reveals similar heavy mineral compositions with a minor amphibole content, different from the drier Xifeng site results of the same age. This result indicates that the monsoonal climate pattern might have been maintained since the late Miocene. Furthermore, it indicates that the heavy mineral method is promising in tracing provenance for sites northwest of the Xifeng site on the Loess Plateau.

  11. Red Clay Sediment in the Central Chinese Loess Plateau and Its Implication for the Uplift of the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    SONG Yougui; LI Jijun; FANG Xiaomin; XIA Fei; DONG Hongmei

    2005-01-01

    The widely distributed red clay sediment underlying the Chinese Loess Plateau truly records the Neogene environmental evolution, and its genesis and development are intrinsically related to the uplift processes of the Tibetan Plateau and the evolution of East Asia monsoon system. In this paper, a detailed magnetostratigraphy of a loess-red clay section (107°13′E, 35°02′N) from the central Loess Plateau is reported. The loess-red clay sequence is composed of 175 m Quaternary loess-paleosol sequence and 128 m Neogene red clay sediments. Based on the correlation with the standard geomagnetic polarity time scale, the paleomagnetic results indicate that the age of Chaona red clay sequence extends to 8.1Ma, which is the older red clay deposition in the central Chinese Loess Plateau. The commencement of red clay at ~8.1 Ma may imply that the Ordos planation surface was broken by the movement of the Haiyuan-Liupanshan Faults, which was related to the uplift of the Tibetan Plateau induced by the collision of India Plate and Eurasian Plate. And the western part adjacent to the Tibetan Plateau was uplifted to form the embryo of the Liupan Shan (Mts.) and the eastern part was down-faulted to receive red clay deposition. We link this faulting to an initial uplift of the Tibetan Plateau. The undulating nature of the broken Ordos planation surface may explain the chronological differences and depth discrepancies among various cross-sections of red clay.

  12. Magnetostratigraphic age and monsoonal evolution recorded by the thickest Quaternary loess deposit of the Lanzhou region, western Chinese Loess Plateau

    Science.gov (United States)

    Zhang, Jun; Li, Jijun; Guo, Benhong; Ma, Zhenhua; Li, Xiaomiao; Ye, Xiyan; Yu, Hao; Liu, Jia; Yang, Cheng; Zhang, Shengda; Song, Chunhui; Hui, Zhengchuang; Peng, Tingjiang

    2016-05-01

    The loess-paleosol sequences of the Chinese Loess Plateau (CLP) are major paleoclimatic archives which document the evolution of the East Asian Monsoon (EAM) and changes in the Northern Hemisphere ice sheets during the Quaternary glacial-interglacial cycles. However, the mechanisms regulating the trend of EAM variations on a tectonic scale are unclear. The loess deposits of the western CLP, which have a close relationship with tectonics and climate, are much better-suited to exploring these mechanisms than those of the central CLP. However, studies of long-term EAM evolution from the western CLP have been hindered by the lack of long, accurately-dated sequences with high sediment accumulation rates. Here, we address this problem via high resolution magnetostratigraphic, magnetic susceptibility and grain-size analyses of a 416.2 m-long drill core located at Xijin Village, near Lanzhou. Paleomagnetic dating indicates that the basal age of the Xijin loess is ∼2.2 Ma. The χ and grain-size records reveal that the East Asian Summer Monsoon (EASM) and East Asian Winter Monsoon (EAWM) strengthened synchronously at ∼1.24 Ma. Subsequently, during interglacial periods, the EASM began to penetrate, and then dominate, in the Lanzhou region. This was followed by two stepwise uptrends, commencing at ∼0.87 and ∼0.62 Ma, which resulted in an increasingly moist interglacial climate in the region. We suggest that the uplift of the Tibetan Plateau was largely responsible for these three stepwise enhancements of the EASM. Overall, however, the long-term trend of strengthening in EAWM in the area may have been primarily caused by long-term global cooling from the Late Pliocene onwards.

  13. A 1.5 Ma sporopollen record of paleoecologic environment evolution in the central Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    WU Fuli; FANG Xiaomin; MA Yuzhen; AN Zhisheng; LI Jijun

    2004-01-01

    A 1.5 Ma sporopollen record was obtained from a continuous loess-paleosol sequence at Chaona in the central Chinese Loess Plateau. It shows that (1) arid herbs of largely Artemisia and Chenopodiaceae and arbors of mainly Pinus, Betula and Quercus dominate loess and paleosol, respectively, reflecting cycles of cold-dry and warm-humid conditions of glaciation and interglaciation; (2) that similar vegetation pattern and cold-dry condition were found in times of unusual thick and coarse loesses L9 and L15, which have been regarded as two extremely cold and dry times as indicated by inorganic climatic proxies; and (3) that shifts of vegetations from earlier forest-steppe to open-forest and steppe and then to steppe were found at 0.95 and 0.5 Ma, implying a stepwise of drying of the Loess Plateau in the Quaternary.

  14. Reassessment of soil erosion on the Chinese loess plateau: were rates overestimated?

    Science.gov (United States)

    Zhao, Jianlin; Govers, Gerard

    2014-05-01

    Several studies have estimated regional soil erosion rates (rill and interrill erosion) on the Chinese loess plateau using an erosion model such as the RUSLE (e.g. Fu et al., 2011; Sun et al., 2013). However, the question may be asked whether such estimates are realistic: studies have shown that the use of models for large areas may lead to significant overestimations (Quinton et al., 2010). In this study, soil erosion rates on the Chinese loess plateau were reevaluated by using field measured soil erosion data from erosion plots (216 plots and 1380 plot years) in combination with a careful extrapolation procedure. Data analysis showed that the relationship between slope and erosion rate on arable land could be well described by erosion-slope relationships reported in the literature (Nearing, 1997). The increase of average erosion rate with slope length was clearly degressive, as could be expected from earlier research. However, for plots with permanent vegetation (grassland, shrub, forest) no relationship was found between erosion rates and slope gradient and/or slope length. This is important, as it implies that spatial variations of erosion on permanently vegetated areas cannot be modeled using topographical functions derived from observations on arable land. Application of relationships developed for arable land will lead to a significant overestimation of soil erosion rates. Based on our analysis we estimate the total soil erosion rate in the Chinese Loess plateau averages ca. 6.78 t ha-1 yr-1 for the whole loess plateau, resulting in a total sediment mobilisation of ca. 0.38 Gt yr-1. Erosion rates on arable land average ca. 15.10 t ha-1 yr-1. These estimates are 2 to 3 times lower than previously published estimates. The main reason why previous estimates are likely to be too high is that the values of (R)USLE parameters such as K, P and LS factor were overestimated. Overestimations of the K factor are due to the reliance of nomograph calculations, resulting

  15. Preliminary study of mollusk fossils in the Qinan Miocene loess-soil sequence in western Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    LI Fengjiang; WU Naiqin; Denis-Didier Rousseau

    2006-01-01

    The first near continuous mollusk fossil record from the Qinan Miocene loess-soil sequence is presented. Results show that mollusk species are abundant in the QA-Ⅰ section between 22 and 6.2 Ma, and both loess layers and soil layers yield mollusk fossil individuals. All mollusk species are terrestrial and well preserved in the section. Most species are identical to those identified in the Quaternary loess-soil sequence of the Loess Plateau. The thermo-humidiphilous group generally is distributed in soil layers, whereas cold-aridiphilous group can be observed in loess layers. From the Miocene to Quaternary, the occurrence and divergence of new species of Metodontia and Cathaica correspond to the crucial periods of regional and global environmental changes, indicating that mollusk species are sensitive to environmental variations. Preliminary study on the QA-Ⅰ mollusk record indicates that the Qinan Miocene loess-soil sequence may have a similar sedimentary environment to the Quaternary loess-soil sequence of the Loess Plateau.

  16. Vegetation evolution on the central Chinese Loess Plateau since late Quaternary evidenced by elemental carbon isotopic composition

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bin; SHEN ChengDe; ZHENG HongBo; ZHAO MeiXun; SUN YanMin

    2009-01-01

    There are many controversial issues in loess studies such as natural vegetation types on the Chinese Loess Plateau during the historical periods and the spatial and temporal evolution of C3/C4 plants.Elemental carbon isotopic composition (δ13Cec) in the loess section may offer new evidence for these problems. Elemental carbon (EC) is produced by incomplete combustion of vegetation, and its carbon isotopic composition has a very small difference from that of the formal vegetation, then δ13Cec can be used as a record to recover the changes of vegetation. Elemental carbon was extracted by applying the oxidation method from the loess-paleosol sequence in the central Chinese Loess Plateau, and its carbon isotope composition was analyzed by the isotope mass spectrometer. The results showed that the vegetation in this region was a mixed type of C3 and C4 plants, dominated with C3 plants in most of the time. Since late Quaternary, C3/C4 plants may not follow a simple glacial-interglacial cycle mode on the Chinese Loess Plateau, but showing fluctuations. C3 plants increased gradually in L4 period, and more C3 plants occurred during S3 period, and C4 plants increased again during L3-L2 periods, after that, C3plants dominated again during S1-S0 periods. During periods of paleosol development, C3 plants were abundant in S3 and S1, and there were more C4 plants in S2 and S0. During periods of loess sedimentation, there were more C3 plants in L4 and L1, and there were more C4 plants in L3 and L2. On the orbital timescale, the vegetation variations revealed by δ13Cec record are consistent with the results of pollen data and also similar to the results obtained by organic carbon isotopic composition since the last glacial period.

  17. Evidence of a humid mid-Holocene in the western part of Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    AN Chengbang; FENG Zhaodong; TANG Lingyu

    2003-01-01

    Field works show that the wetland/swamp layers were distributed ubiquitously in the western part of the Chinese Loess Plateau. Universality of the wetland/swampy layer and the consistency of the age reveal that the layer was developed under the humid climatic condition. Dated between 9 and 3.8 kaBP, the wetland/swampy layer is full of aquatic mollusks and has the highest tree and shrub pollen, indicating a humid mid-Holocene. Variations of grain size suggest that winter monsoon weakened during 9-3.8 kaBP while climate change to humid and vegetation cover increased from 9 kaBP onward. After 5.9 kaBP, the humidity declined gradually. In 3.8 kaBP, summer monsoon sharply retreated, and the climate changed to dry.

  18. Holocene pedogenic change and the emergence and decline of rain-fed cereal agriculture on the Chinese Loess Plateau

    Science.gov (United States)

    Huang, Chun Chang; Pang, Jiangli; Zhou, Qunying; Chen, Shu'e.

    2004-12-01

    Multi-disciplinary investigations were carried out in a Holocene eolian loess-soil profile in the centre of the Chinese Loess Plateau at the transition between the arid Mongolian steppe and the semi-arid mixed forest, and also the transitional zone between nomadism and the rain-fed cereal agriculture in history. The cultural remains of an earliest rain-fed cereal agriculture, and also the remains of a Bronze Age nomadic community identified in the profile indicate that the regional emergence and decline of the rain-fed cereal agriculture was closely connected with the change in dust accumulation and soil formation. The climatic proxies derived from the profile show that monsoonal climatic variation, especially precipitation behind the pedogenic change, was ultimately responsible for the cultural and land-use change over the Loess Plateau. Increased precipitation brought on by southeast monsoon, conditioned the domestication and cultivation of millets in the southern part of the region during 8000-7000 a BP at the beginning of the Holocene climatic optimum. Sufficient precipitation and the well-developed fertile soils facilitated the expansion of millets cultivation to the northern Loess Plateau and the southern Mongolian Plateau between 7000 a BP and 3600 a BP. Reduced precipitation and deteriorated land-use conditions because of intensified northwest monsoon at the end of the Holocene climatic optimum caused a regional desertion by the arable farming communities and the invasion of the nomads in the northern part of the Loess Plateau from ca. 3600 a BP during the Bronze Age. Monsoonal climatic change and the resultant pedogenic change dramatically affected the cultural development over the Loess Plateau during the Holocene.

  19. An 8.1Ma calcite record of Asian summer monsoon evolution on the Chinese central Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Carbonates in loess-red clay sequences consist mainly of calcite and dolomite. The EDTA analysis of carbonates in different size fractions and magnetic susceptibility reveal that calcite is a sensitive index of summer monsoon. The chemical analysis of carbonates and calcite from an 8.1 Ma loess-red clay sequence at Chaona on the Chinese central Loess Plateau shows that the evolution of the Asian summer monsoon experienced four stages, namely 8.1―5.5 Ma, 5.5―2.8 Ma, 2.8―1.5 Ma and 1.5―0 Ma, with increasing intensification and fluctuation, suggesting a possible combining impacts of uplift of the Tibetan Plateau and global changes on the Asian summer monsoon.

  20. Statistical determination of rainfall-runoff erosivity indices for single storms in the Chinese Loess Plateau.

    Science.gov (United States)

    Zheng, Mingguo; Chen, Xiaoan

    2015-01-01

    Correlation analysis is popular in erosion- or earth-related studies, however, few studies compare correlations on a basis of statistical testing, which should be conducted to determine the statistical significance of the observed sample difference. This study aims to statistically determine the erosivity index of single storms, which requires comparison of a large number of dependent correlations between rainfall-runoff factors and soil loss, in the Chinese Loess Plateau. Data observed at four gauging stations and five runoff experimental plots were presented. Based on the Meng's tests, which is widely used for comparing correlations between a dependent variable and a set of independent variables, two methods were proposed. The first method removes factors that are poorly correlated with soil loss from consideration in a stepwise way, while the second method performs pairwise comparisons that are adjusted using the Bonferroni correction. Among 12 rainfall factors, I30 (the maximum 30-minute rainfall intensity) has been suggested for use as the rainfall erosivity index, although I30 is equally correlated with soil loss as factors of I20, EI10 (the product of the rainfall kinetic energy, E, and I10), EI20 and EI30 are. Runoff depth (total runoff volume normalized to drainage area) is more correlated with soil loss than all other examined rainfall-runoff factors, including I30, peak discharge and many combined factors. Moreover, sediment concentrations of major sediment-producing events are independent of all examined rainfall-runoff factors. As a result, introducing additional factors adds little to the prediction accuracy of the single factor of runoff depth. Hence, runoff depth should be the best erosivity index at scales from plots to watersheds. Our findings can facilitate predictions of soil erosion in the Loess Plateau. Our methods provide a valuable tool while determining the predictor among a number of variables in terms of correlations.

  1. Seven million year iron geochemistry record from a thick eolian red clay-loess sequence in Chinese Loess Plateau and the implications for paleomonsoon evolution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Recently, the Tertiary red clay sequence underlying Pleistoceneloess has attracted much attention. The remarkable progress is the recognition that the Tertiary red clay sequence is also wind-blown in origin, thus providing a good opportunity to reconstruct long-term monsoon changes. In contrast to the loess deposits, the magnetic susceptibility and the pedogenic characteristics are almost independent of each other in the red clay, thus challenging the validity of the readily measurable magnetic susceptibility in describing the monsoon history recorded by the red clay. With the objective to address the long-term East Asia summer monsoon evolution, the free to total Fe2O3 ratios were calculated in a continuous eolian red clay-loess sequence at Lingtai, the Chinese Loess Plateau, which has a thickness of 305 m and a basal age of 7.0 Ma. The seven million year Fe2O3 ratio record from the red clay-loess sequence indicates that (ⅰ) variations of the free to total Fe2O3 ratios of the loess can correlate generally with the alternations of the loess and paleosol horizons; (ⅱ) the East Asia summer monsoon was stronger as a whole in Neogene than that in Quaternary; (ⅲ) the strongest East Asia summer monsoon may occur between 4.0 and 4.8 Ma. The relatively small ice volume and high global temperature may be responsible for the strong summer monsoon during the early Pliocene.

  2. Chronofunctions of Heilu soil developed from Loess in Luochuan, on the chinese Loess plateau

    Directory of Open Access Journals (Sweden)

    Gang Liu

    2011-08-01

    Full Text Available Soil chronofunctions are an alternative for the quantification of soil-forming processes and underlie the modeling of soil genesis. To establish soil chronofunctions of a Heilu soil profile on Loess in Luochuan, selected soil properties and the 14C ages in the Holocene were studied. Linear, logarithmic, and third-order polynomial functions were selected to fit the relationships between soil properties and ages. The results indicated that third-order polynomial function fit best for the relationships between clay (< 0.002 mm, silt (0.002-0.02 mm, sand (0.02-2 mm and soil ages, and a trend of an Ah horizon ocurrence in the profile. The logarithmic function indicated mainly variations of soil organic carbon and pH with time (soil age. The variation in CaCO3 content, Mn/Zr, Fe/Zr, K/Zr, Mg/Zr, Ca/Zr, P/Zr, and Na/Zr ratios with soil age were best described by three-order polynomial functions, in which the trend line showed migration of CaCO3 and some elements.

  3. Land rehabilitation, erosion and C sequestration in soils of the Chinese Loess Plateau

    Science.gov (United States)

    Li, Yong; Van Oost, Kristof; Quine, Tim; Govers, Gerard

    2013-04-01

    Once the cradle of Chinese civilization, the Chinese loess plateau is now one of the most degraded ecosystems in the world and a wide range of ecological rehabilitation programs have been implemented since the 1950s that aim at facilitating synergies between soil conservation, food production and socio-economic welfare. More recently, the scope of vegetation restoration programs has been extended to include sequestration of C by soils and the reconversion of 4.8 million ha of cropland to forest and grassland has re-sequestered a substantial amount of C in soils between 2000 and 2008. Although this appears to represent a significant win-win, these estimates are associated with considerable uncertainty both due to the extrapolation and, significantly, because of the assumptions made about the pre-restoration state. Here, we argue that a full assessment of the C sequestration benefit of land rehabilitation programs requires quantification not only of the C uptake in vegetation and plants under the new land use regime (as has been undertaken), but also of the soil atmosphere C exchange associated with the elevated erosion rates that typify the pre-restoration state. We present the results of an intensive measurement campaign to characterize the erosional control on vertical carbon fluxes from degraded land, typical of the pre-restoration state. We report year-round soil respiration (in the absence of vegetation) measurements with high temporal resolution along an erosion gradient on cultivated sloping land in the Chinese Loess Plateau. At 14 sites along an eroding cultivated slope, we quantified the temporal dynamics of soil CO2 fluxes using an Automated Soil CO2 Flux System. This resulted in 13296 respiration measurements between April 2007 and September 2008. We investigate the factors controlling in-situ soil respiration, including soil temperature, moisture, soil erosion and SOC stock and quality. Soil and, by inference, C erosion and deposition since 1954 were

  4. Impacts of Re-Vegetation on Surface Soil Moisture over the Chinese Loess Plateau Based on Remote Sensing Datasets

    OpenAIRE

    Qiao Jiao; Rui Li; Fei Wang; Xingmin Mu; Pengfei Li; Chunchun An

    2016-01-01

    A large-scale re-vegetation supported by the Grain for Green Project (GGP) has greatly changed local eco-hydrological systems, with an impact on soil moisture conditions for the Chinese Loess Plateau. It is important to know how, exactly, re-vegetation influences soil moisture conditions, which not only crucially constrain growth and distribution of vegetation, and hence, further re-vegetation, but also determine the degree of soil desiccation and, thus, erosion risk in the region. In this st...

  5. Quantification of magnetic nanoparticles with broadband-frequency magnetic susceptibility measurements: High-resolution climatic records from an upper loess-paleosol succession at Luochuan, Chinese Loess Plateau

    Science.gov (United States)

    Kodama, K.; An, Z.; Chang, H.; Qiang, X.

    2013-12-01

    Broadband magnetic susceptibility (MS) measurement, a novel magnetic method capable of quantifying a narrow grain size distribution (GSD) of superparamagnetic (SP) particles, has been tested in a loess/paleosol section at Luochuan in the Chinese Loess Plateau. The studied succession consists of sequences from the latest paleosol unit (S0) to the upper part of the loess unit (L2), spanning the last glacial-interglacial cycle. Reconstructed GSDs consist of volume fractions on the order of 10-24 m3, and the mean GSDs are modal but with distinctive skewness among the loess, the weakly developed paleosols (weak paleosols), and the mature paleosols. This indicates that the mean volume of SP particles in this loess/paleosol sequence tends to increase during the transition from loess → weak paleosol → paleosol, an indication of grain growth as pedogenesis progresses. Total frequency dependence (TFD), the difference between two MSs at the lowest (130 Hz) and the highest (500 kHz) frequencies, is judged to be a more suitable index than previous frequency dependence parameters for the concentration of SP particles. TFD (%), the TFD normalized to χ130 (MS at 130 Hz), has a strong correlation with χ130, showing a continuous 'growth curve' with the rate of increase being highest for the loess, moderate for the weak paleosols, and saturated for the paleosols. The characteristic curve suggests that smaller SP particles are preferentially formed in the earlier stage of pedogenesis rather than the later phase when even larger particles are formed in mature paleosols. A profile of another index for the proportion of finer SP particle fractions to the total SP concentration shows high-frequency fluctuations that resemble the oxygen isotope records from cave stalagmites in southeastern China and from the Greenland ice cores for the last glacial-interglacial cycle. These results demonstrate that the broadband MS measurement method will be useful for the quantitative assessment of

  6. Quantification of magnetic nanoparticles with broad-band-frequency magnetic susceptibility measurements: a case study of an upper loess/palaeosol succession at Luochuan, Chinese Loess Plateau

    Science.gov (United States)

    Kodama, Kazuto; An, Zhisheng; Chang, Hong; Qiang, Xiaoke

    2014-11-01

    Broad-band magnetic susceptibility (MS) measurement, a novel magnetic method capable of quantifying a narrow grain size distribution (GSD) of superparamagnetic (SP) particles by measuring low-field MS at a number of frequency steps spanning four orders of magnitude, has been tested in a loess/palaeosol section at Luochuan in the Chinese Loess Plateau. The studied succession consists of sequences from the latest palaeosol unit (S0) to the upper part of the loess unit (L2), spanning the last glacial-interglacial cycle. Reconstructed GSDs consist of volume fractions on the order of 10-24 m3, and the mean GSDs are modal but with distinctive skewness among the loess, the weakly developed palaeosols (weak palaeosols), and the mature palaeosols. This indicates that the mean volume of SP particles in this loess/palaeosol sequence tends to increase during the transition from loess → weak palaeosol → palaeosol, an indication of grain growth as pedogenesis progresses. Total frequency dependence, or TFD(per cent), the difference between χ130 at the lowest (130 Hz) and χ500k at the highest (500 kHz) frequencies normalized to χ130, is judged to be a more suitable index than previous frequency dependence parameters for the concentration of SP particles. TFD(per cent) has a strong correlation with χ130, showing a continuous `growth curve' with the rate of increase being highest for the loess, moderate for the weak palaeosols, and saturated for the palaeosols. The characteristic curve suggests that smaller SP particles are preferentially formed in the earlier stage of pedogenesis rather than the later phase when even larger particles are formed in mature palaeosols. These results demonstrate that the broad-band MS measurement method will be useful for the quantitative assessment of magnetic nanoparticles in soils and sediments.

  7. Spatiotemporal variations of vegetation cover on the Chinese Loess Plateau(1981―2006):Impacts of climate changes and human activities

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Spatiotemporal variations of Chinese Loess Plateau vegetation cover during 1981-2006 have been investigated using GIMMS and SPOT VGT NDVI data and the cause of vegetation cover changes has been analyzed, considering the climate changes and human activities. Vegetation cover changes on the Loess Plateau have experienced four stages as follows: (1) vegetation cover showed a continued increasing phase during 1981―1989; (2) vegetation cover changes came into a relative steady phase with small fluctuations during 1990―1998; (3) vegetation cover declined rapidly during 1999―2001; and (4) vegetation cover increased rapidly during 2002―2006. The vegetation cover changes of the Loess Plateau show a notable spatial difference. The vegetation cover has obviously increased in the Inner Mongolia and Ningxia plain along the Yellow River and the ecological rehabilitated region of Ordos Plateau, however the vegetation cover evidently decreased in the hilly and gully areas of Loess Plateau, Liupan Mountains region and the northern hillside of Qinling Mountains. The response of NDVI to climate changes varied with different vegetation types. NDVI of sandy land vegetation, grassland and cultivated land show a significant increasing trend, but forest shows a decreasing trend. The results obtained in this study show that the spatiotemporal variations of vegetation cover are the outcome of climate changes and human activities. Temperature is a control factor of the seasonal change of vegetation growth. The increased temperature makes soil drier and unfavors vegetation growth in summer, but it favors vegetation growth in spring and autumn because of a longer growing period. There is a significant correlation between vegetation cover and precipitation and thus, the change in precipitation is an important factor for vegetation variation. The improved agricultural production has resulted in an increase of NDVI in the farmland, and the implementation of large-scale vegetation

  8. Spatiotemporal variations of vegetation cover on the Chinese Loess Plateau (1981―2006): Impacts of climate changes and human activities

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Spatiotemporal variations of Chinese Loess Plateau vegetation cover during 1981-2006 have been investigated using GIMMS and SPOT VGT NDVI data and the cause of vegetation cover changes has been analyzed, considering the climate changes and human activities. Vegetation cover changes on the Loess Plateau have experienced four stages as follows: (1) vegetation cover showed a continued increasing phase during 1981-1989; (2) vegetation cover changes came into a relative steady phase with small fluctuations during 1990-1998; (3) vegetation cover declined rapidly during 1999-2001; and (4) vegetation cover increased rapidly during 2002-2006. The vegetation cover changes of the Loess Plateau show a notable spatial difference. The vegetation cover has obviously increased in the Inner Mongolia and Ningxia plain along the Yellow River and the ecological rehabilitated region of Ordos Plateau, however the vegetation cover evidently decreased in the hilly and gully areas of Loess Plateau, Liupan Mountains region and the northern hillside of Qinling Mountains. The response of NDVI to climate changes varied with different vegetation types. NDVI of sandy land vegetation, grassland and cultivated land show a significant increasing trend, but forest shows a decreasing trend. The results obtained in this study show that the spatiotemporal variations of vegetation cover are the outcome of climate changes and human activities. Temperature is a control factor of the seasonal change of vegetation growth. The increased temperature makes soil drier and unfavors vegetation growth in summer, but it favors vegetation growth in spring and autumn because of a longer growing period. There is a significant correlation between vegetation cover and precipitation and thus, the change in precipitation is an important factor for vegetation variation. The improved agricultural production has resulted in an increase of NDVI in the farmland, and the implementation of large-scale vegetation construction has

  9. Contrasting behavior of hematite and goethite within paleosol S5 of the Luochuan profile, Chinese Loess Plateau

    Science.gov (United States)

    Liu, Qingsong; Bloemendal, Jan; Torrent, Jose; Deng, Chenglong

    2006-10-01

    The Chinese loess/paleosol sequence provides an excellent record of long-term variations in the East Asian paleomonsoon. For representative loess profiles, paleosol units have enhanced magnetic properties compared to loess units. However, at some depth intervals with special paleoenvironmental conditions, selective depletion of antiferromagnetic (AFM) minerals (hematite and goethite) could occur, resulting in complexities in accurately linking variations in magnetic properties to long-term fluctuations in paleoclimate. To resolve this problem, we directly measured the mass concentrations of these AFM minerals using second-order diffuse reflectance spectroscopy (DRS), and then correlated the DRS results to high-field isothermal remanent magnetization (HIRM) from paleosol unit S5 at the Luochuan profile, central Chinese Loess Plateau. Our results suggest that a low HIRM anomaly just below the sub-paleosol unit S5S1 is caused by fluctuations specifically in goethite content, while the hematite concentration exhibits a maximum over the same depth interval. This appears to rule out significant loss of hematite to reductive dissolution and further indicates that hematite and goethite may respond differently to changes in the paleoclimate conditions.

  10. A review of recent advances in red-clay environmental magnetism and paleoclimate history on the Chinese Loess Plateau

    Science.gov (United States)

    Nie, Junsheng; Song, Yougui; King, John

    2016-03-01

    The red-clay sequence on the Chinese Loess Plateau (CLP) was deposited during the late Miocene-Pliocene and is encoded with important information of past climate changes. However, it has received much less study in comparison to the overlying Pleistocene loess-paleosol sequence. In this paper, we review recent progress in characterizing the environmental magnetic parameter-based paleoclimate history recorded by the red-clay sequence. Several key conclusions are as follows. 1) the red clay and the loess-paleosol sequences have similar magnetic enhancement mechanisms but magnetic minerals in the red clay sequence have experienced a higher degree of oxidation than in the loess-paleosol sequence. 2) The CLP experienced a cooling and wetting trend from 4.5 to 2.7 Ma, caused by ice sheet expansion and East Asian summer monsoon intensification, respectively. 3) The above conclusions benefit from backfield remanence curve unmixing and comparison of magnetic grain size/concentration records, which are particularly useful in separating the temperature from the precipitation signal. A clear need in future studies is to explore the concentration and the grain size variations of hematite and goethite in the red-clay sequence and their formation mechanisms. The payback would be a clear understanding of climate history during the late Miocene-Pliocene, a possible analog for future warmer climate.

  11. Impacts of Re-Vegetation on Surface Soil Moisture over the Chinese Loess Plateau Based on Remote Sensing Datasets

    Directory of Open Access Journals (Sweden)

    Qiao Jiao

    2016-02-01

    Full Text Available A large-scale re-vegetation supported by the Grain for Green Project (GGP has greatly changed local eco-hydrological systems, with an impact on soil moisture conditions for the Chinese Loess Plateau. It is important to know how, exactly, re-vegetation influences soil moisture conditions, which not only crucially constrain growth and distribution of vegetation, and hence, further re-vegetation, but also determine the degree of soil desiccation and, thus, erosion risk in the region. In this study, three eco-environmental factors, which are Soil Water Index (SWI, the Normalized Difference Vegetation Index (NDVI, and precipitation, were used to investigate the response of soil moisture in the one-meter layer of top soil to the re-vegetation during the GGP. SWI was estimated based on the backscatter coefficient produced by the European Remote Sensing Satellite (ERS-1/2 and Meteorological Operational satellite program (MetOp, while NDVI was derived from SPOT imageries. Two separate periods, which are 1998–2000 and 2008–2010, were selected to examine the spatiotemporal pattern of the chosen eco-environmental factors. It has been shown that the amount of precipitation in 1998–2000 was close to that of 2008–2010 (the difference being 13.10 mm. From 1998–2000 to 2008–2010, the average annual NDVI increased for 80.99%, while the SWI decreased for 72.64% of the area on the Loess Plateau. The average NDVI over the Loess Plateau increased rapidly by 17.76% after the 10-year GGP project. However, the average SWI decreased by 4.37% for two-thirds of the area. More specifically, 57.65% of the area on the Loess Plateau experienced an increased NDVI and decreased SWI, 23.34% of the area had an increased NDVI and SWI. NDVI and SWI decreased simultaneously for 14.99% of the area, and the decreased NDVI and increased SWI occurred at the same time for 4.02% of the area. These results indicate that re-vegetation, human activities, and climate change have

  12. Actual daily evapotranspiration estimated from MERIS and AATSR data over the Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    R. Liu

    2009-02-01

    Full Text Available The Loess Plateau is located in north of China and has a significant impact on the climate and ecosystem evolvement over the East Asian continent. Based on the land surface energy balance theory, the potential of using Medium Resolution Imaging Spectrometer (onboard sensor of the Environmental Satellite remote sensing data on 7, 11 and 27 June 2005 is explored. The "split-window" algorithm is used to retrieve surface temperature from the Advanced the Along-Track Scanning Radiometer, another onboard senor of the Environmental Satellite. Then the near surface net radiation, sensible heat flux and soil heat flux are estimated by using the developed algorithm. We introduce a simple algorithm to predict the heat flux partitioning between the soil and vegetation. Combining the sunshine hours, air temperature, sunshine duration and wind speed measured by weather stations, a model for estimating daily ET is proposed. The instantaneous ET is also converted to daily value. Comparison of latent heats flux retrieved by remote sensing data with ground observation from eddy covariance flux system during Loess Plateau land surface process field Experiment, the maximum and minimum error of this approach are 10.96% and 4.80% respectively, the cause of the bias is also explored and discussed.

  13. Time-Transgressive Nature of the Magnetic Susceptibility Record across the Chinese Loess Plateau at the Pleistocene/Holocene Transition.

    Directory of Open Access Journals (Sweden)

    Yajie Dong

    Full Text Available The loess stratigraphic boundary at the Pleistocene/Holocene transition defined by the magnetic susceptibility (MS has previously been assumed to be synchronous with the Marine Isotope Stage (MIS 2/1 boundary, and approximately time-synchronous at different sections across the Chinese Loess Plateau (CLP. However, although this assumption has been used as a basis for proxy-age model of Chinese loess deposits, it has rarely been tested by using absolute dating methods. In this study, we applied a single-aliquot regenerative-dose (SAR protocol to the 45-63 μm quartz grain-size fraction to derive luminescence ages for the last glacial and Holocene sections of three loess sections on a transect from southeast to northwest across the CLP. Based on the 33 closely spaced optically stimulated luminescence (OSL samples from the three sections, OSL chronologies were established using a polynomial curve fit at each section. Based on the OSL chronology, the timing of the Pleistocene/Holocene boundary, as defined by rapid changes in MS values, is dated at ~10.5 ka, 8.5 ka and 7.5 ka in the Yaoxian section, Jingchuan and Huanxian sections respectively. These results are clearly inconsistent with the MIS 2/1 boundary age of 12.05 ka, and therefore we conclude that the automatic correlation of the Pleistocene/Holocene transition, as inferred from the MS record, with the MIS 2/1 boundary is incorrect. The results clearly demonstrate that the marked changes in MS along the southeast to northwest transect are time-transgressive among the different sites, with the timing of significant paleosol development as indicated by the MS record being delayed by 3-4 ka in the northwest compared to the southeast. Our results suggest that this asynchronous paleosol development during the last deglacial was caused by the delayed arrival of the summer monsoon in the northwest CLP compared to the southeast.

  14. Mass accumulation rate and monsoon records from Xifeng, Chinese Loess Plateau, based on a luminescence age model

    DEFF Research Database (Denmark)

    Stevens, Thomas; Buylaert, Jan-Pieter; Lu, Huayu;

    2016-01-01

    in many other OSL‐dated Loess Plateau sites. East Asian monsoon grain‐size and magnetic susceptibility records also show several differences between independently dated loess sites. This complicates our understanding of any lag between insolation forcing and monsoon response. Nevertheless, the Xifeng...

  15. Agricultural vulnerability over the Chinese Loess Plateau in response to climate change: Exposure, sensitivity, and adaptive capacity.

    Science.gov (United States)

    Li, Xueling; Philp, Joshua; Cremades, Roger; Roberts, Anna; He, Liang; Li, Longhui; Yu, Qiang

    2016-04-01

    Understanding how the vulnerability of agricultural production to climate change can differ spatially has practical significance to sustainable management of agricultural systems worldwide. Accordingly, this study developed a conceptual framework to assess the agricultural vulnerability of 243 rural counties on the Chinese Loess Plateau. Indicators representing the climate/agriculture interface were selected to describe exposure and sensitivity, while stocks of certain capitals were used to describe adaptive capacity. A vulnerability index for each county was calculated and the spatial distribution was mapped. Results showed that exposure, sensitivity, and adaptive capacity occur independently, with most contributing indicator values concentrated in a narrow range after normalization. Within the 49 most vulnerable counties, which together encompass 81 % of the vulnerability index range, 42 were characterized by high exposure and sensitivity but low adaptive capacity. The most vulnerable area was found to be located in the central northeast-southwest belt of Loess Plateau. Adaptation measures for both ecological restoration and economic development are needed and potential adaptation options need further investigation.

  16. A comparison of zircon U-Pb age results of the Red Clay sequence on the central Chinese Loess Plateau

    Science.gov (United States)

    Gong, Hujun; Nie, Junsheng; Wang, Zhao; Peng, Wenbin; Zhang, Rui; Zhang, Yunxiang

    2016-08-01

    Single grain zircon U-Pb geochronology has demonstrated great potentials in extracting tectonic and atmospheric circulation signal carried by aeolian, fluvial, and fluviolacustrine sediments. A routine in this sort of studies is analyzing 100-150 grains and then compares zircon U-Pb age spectra between the measured sample and the potential sources. Here we compared the zircon U-Pb age results of the late Miocene-Pliocene Red Clay sequence of two neighboring sites from the Chinese Loess Plateau where similar provenance signal is expected. Although the results from the 5.5 Ma sediment support this prediction, the results from the 3 Ma sediment at these two sites differ from each other significantly. These results emphasize the importance of increasing analysis number per sample and combining the zircon U-Pb geochronology with other provenance tools in order to get reliable provenance information.

  17. IRSL and post-IR IRSL residual doses recorded in modern dust samples from the Chinese Loess Plateau

    DEFF Research Database (Denmark)

    Buylaert, Jan-Pieter; Thiel, Christine; Murray, Andrew S.;

    2011-01-01

    Using a set of modern/young (0 to about 200 years old) dust samples collected from the Chinese Loess Plateau the bleachability of IRSL measured at 50°C (IR50) and post-IR50 elevated temperature IRSL (measured at 225°C and at 290°C) is investigated by measuring the apparent (residual) doses recorded...... by these signals. Doses recorded by quartz OSL are used as a reference. Allowing for differences in dose rates it seems that both IRSL and post-IR IRSL signals yield residual doses that are significantly larger than the doses measured in quartz. These residual doses can be largely explained by thermal transfer...

  18. [Analysis of sap flow characteristics of the Chinese pine in typical Loess Plateau Region of China].

    Science.gov (United States)

    Zhang, Han-dan; Wei, Wei; Chen, Li-ding; Yu, Yang; Yang, Lei; Jia, Fu-yan

    2015-01-01

    Transpiration is one of the major processes of water consumption. It is significant for nutrients transportation, plant development, drought stress alleviation and micro-climate amelioration. In this study, the artificially planted Chinese pine (Pinus tabuliformis) was selected as an example to explore its transpiration characteristics, water-use strategies and the adaptability of the living environment in a typical loess hilly area of China. The results showed that: the sap flow rates of Chinese pine varied obviously in different seasons. The minimum sap flow rate occurred in April, followed by October, September and August, which was 0.024, 0.057, 0.062 and 0.071 mL x (cm2 x min)(-1), respectively. The rule of the diurnal variation of sap flow rate was regular, higher in daytime than at night. The flow rate was low during nighttime, but not zero. In rainfall events, the proportion of sap flow during nighttime was significantly increased, which was 3.9 times of that on sunny days, with 31.8% decrease in daytime. Chinese pine had great adaptability to unexpected climates. The variation trend of flow rate in the clod was similar to that on rainy days. The sap flow velocity was in great relevance with meteorological factors, with a declining order of solar radiation, vapor pressure deficit, relative humidity, and atmospheric temperature.

  19. Variations of organic carbon isotopic composition and its environmental significance during the last glacial on western Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    CHEN Fahu; RAO Zhiguo; ZHANG Jiawu; JIN Ming; MA Jianying

    2006-01-01

    A high-resolution loess section in the western Chinese Loess Plateau, Yuanbao Section,was sampled for organic carbon isotopic analyses.The soil organic carbon isotope (δ13Corg) varied between -22.6‰ and -27.5‰ during the last glacial at the section. During the last interstadial, the δ13Corg values were more negative than those in both early and late periods of the last glacial by 4‰. The isotopic composition indicates a coupled response of the pure C3 plants to the temperature, precipitation and the concentration of atmospheric CO2. Decrease in temperature and the atmospheric CO2 concentration from the last interstadial to Last Glaicial Maximum (LGM) caused the organic carbon isotopes to become positive by 1.5‰-2.0‰. The amplitude of 4‰in the δ13Corg variation during the last glacial should be mainly caused by the precipitation change.Therefore, the δ13Corg variations of the Yuanbao Section during the last glacial period documented the large-amplitude fluctuation of the monsoon precipitation, which is estimated to be 250-310 mm more during the last interstadial than that in the LGM, and 100 mm more than that during early last glacial. The rapid changes of the monsoon precipitation on millennial scale during the last glacial have also been recorded in the isotopic variations in Yuanbao loess section. As the isotopic composition varies complicatedly as shown in the Ioess-paleosol sequence, it cannot be simply attributed to the abundances of C3and C4 plants or be used as an indicator of the summer monsoon variations.

  20. Chronology of the Holocene loess-paleosol section and its deposition and pedogenesis on the south of Chinese Loess Plateau%黄土高原南部全新世古土壤的沉积序列

    Institute of Scientific and Technical Information of China (English)

    贾耀锋; 黄春长; 庞奖励; 牛俊杰

    2008-01-01

    Optically stimulated luminescence (OSL) dating for polymineral fine-grained loess samples, collected in Laoguantai (LGT) section on the south of the Chinese Loess Plateau,was made by application of single-aliquot regenerative-dose (SAR) protocol. A 'Double-SAR'procedure in which aliquots are subjected to both infrared (IR) and blue stimulations was used,and two sets of equivalent dose (Ds) determinations were produced and assumed to rela tepredominantly to feldspathic and quartz fine grain populations respectively. The OSL ages estimated from IRSL signals are smaller than those estimated from [post-IR] OSL signals due to the anomalous fading of feldspar IR signals, based on fading experiment. The young ages of the samples near ground surface may be originated from the post-depositlonal disturbance by the intensifying humanity's cultivation since 3.0 ka BP in the Guanzhong Basin, south of the Chinese Loess Plateau. Based on OSL dating, as well as field observations and stratlgraphic correlation, we determine the chronology of the LGT Ioess-paleosol sequence. In combination with climate proxy records, It is indicated that aeolian loess deposition and pedogenesis underwent polyphase changes during the Holocene, likely to have been driven by shifts in the East Asian monsoon. This suggests that aeolian loess deposition is episodic and highly variable, with contributions from non-aeolian processes such as alluvial deposition found in the area.

  1. Variations in vegetation cover and topography control gully density and sediment production on the Chinese Loess Plateau

    Science.gov (United States)

    Zhao, Jianlin; Govers, Gerard

    2016-04-01

    The factors controlling topsoil erosion rates are relatively well understood. This explains why topsoil erosion rates on the Chinese loess plateau (CLP) can be relatively accurately estimated using a combination of empirical data and relatively simple models (Zhao et al., in press). This is, however, not the case for non-topsoil erosion (sediment production by gullying and landslides): while it is well known that these processes produce significant amounts of sediment, the factors controlling their intensity on the CLP are far less understood. In this study, the contribution of non-topsoil erosion to total sediment production on the CLP was investigated. We estimated non-topsoil erosion rates (ENT) by making the difference between measured total sediment yield and the estimated topsoil erosion in 46 gauged catchments on the CLP for the period 1950-1970, when soil conservation measures were mostly absent in the area. We tested an extensive set of environmental variables related to topography, climate and the impact of land use for correlation Our results showed that the average catchment erosion rate (E) and ENT between 1950 and 1970 were 68.29 tha-1yr-1 and 58.02 tha-1yr-1 respectively. The sediment contribution of non-topsoil erosion to total sediment production ranged between 0 and 97% with a mean of 70%. Both E and ENT were significantly related with river slope, land use, NDVI, and gully density. However, gully density was the only variable explaining a major part of the variance in both E (60%) and ENT (57%). Gully density itself was significantly related to topography and vegetation cover but not to precipitation. Importantly, gully density was not only related to overall slope steepness, but also the river gradients and the hypsometric integral, suggesting that not only land cover disturbance but also tectonic uplift may control gully density and erosion rates. The absence of a clear climate signal, both with respect to the variation in gully density and in

  2. Rock magnetic properties of a loess-paleosol couple along an N-S transect in the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    GUO; Bin

    2001-01-01

    [1]Jiao Jiujiu, Grey hydrogeologic system analysis and time series model, Survey Science and Technology (in Chinese), 1987,(10): 39-43.[2]Li Shuwen, Wang Baolai, Xiao Guoqiang, A compound model of grey and periodic scrape and its application in groundwater prediction, Journal of Hebei Institute of Architectural Science & Technology (in Chinese), 1992, (3): 246-251.[3]Wang Qingyin, Li Shuwen, Grey distributed parameter model and groundwater analog, Journal of Hebei Institute of Architectural Science & Technology (in Chinese), 1992, (3): 66-70.[4]Guo Chunqing, Xia Riyuan, Liu Zhenglin, Gray Systematic Theory and Methodological Study of Krast Groundwater Resources Evaluation (in Chinese), Beijing: Geological Publishing House, 1993, 3-60.[5]Wang Qingyin, Liu Kaidi, The Mathematical Method of Grey Systematic Theory and Its Application (in Chinese), Chengdu: Publishing House of Southwestern China University of Communication, 1990, 23-27.[6]Wang Qingyin, Wu Heqing, The concept of grey number and its property, in Proceedings of NAFIPS98, USA, 1998,45-49.[7]Givoli, D., Doukhovni, I., Finite element programming approach for contact problems with geometrical nonlinearity, Computers and Structures, 1996, (8): 31-41.[8]Li Shuwen, Wang Zhiqiang, Wu Qiang, The superiority of storage-centered finite element method in solving seepage problem, Coal Geology and Exploration (in Chinese), 1999, (5): 46-49.

  3. Sap flow in response to rainfall pulses for two shrub species in the semiarid Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    Jian Shengqi

    2016-06-01

    Full Text Available Rainfall pulses can significantly drive the evolution of the structure and function of semiarid ecosystems, and understanding the mechanisms that underlie the response of semiarid plants to rainfall is the key to understanding the responses of semi–arid ecosystems to global climatic change. We measured sap flow in the branches and stems of shrubs (Caragana korshinskii Kom. and Hippophae rhamnoides Linn. using sap flow gauges, and studied the response of sap flow density to rainfall pulses using the “threshold–delay” model in the Chinese Loess Plateau. The results showed that the sap flow began about 1 h earlier, and increased twofold after rainfall, compared to its pre-rainfall value. The sap flow increased significantly with increasing rainfall classes, then gradually decreased. The response of sap flow was different among rainfall, species, position (branch and stem during the pulse period, and the interactive effects also differed significantly (P < 0.0001. The response pattern followed the threshold–delay model, with lower rainfall thresholds of 5.2, 5.5 mm and 0.7, 0.8 mm of stem and branch for C. korshinskii and H. rhamnoides, demonstrating the importance of small rainfall events for plant growth and survival in semi–arid regions.

  4. Soil Microbial and Enzymatic Activities Across a Chronosequence of Chinese Pine Plantation Development on the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    YUAN Bing-Cheng; YUE Dong-Xia

    2012-01-01

    Successional and seasonal effects on soil microbial and enzymatic properties were studied in Chinese pine (Pinus tabulaeformis) plantations in an age sequence of 3-,7-,13-,21- and 28-year-old in northern Ziwuling region in the middle of Loess Plateau,China. The results indicated that plantation age and season affected soil microbial and enzymatic parameters significantly.Soil organic C,total N,microbial biomass C,microbial quotient,basal respiration,dehydrogenase,N-α-benzoyl-L-argininamide (BAA)-protease,urease and β-glucosidase increased quickly and tended to be highest at PF21 (21-year plantation),thereafter they remained nearly at a constant level,whereas the metabolic quotient (qCO2) showed an initial increase and then decreased gradually.Measures of these soil properties showed significant seasonal fluctuations except for organic C and total N,which were found to be relatively stable throughout the study period,and the seasonal distributions were autumn > spring > summer > winter for microbial biomass C,microbial quotient,dehydrogenase,and β-glucosidase; autumn > summer > spring > winter for BAA-protease and urease; and summer > autumn > spring > winter for basal respiration and qCO2.Significant season × age interaction was observed for biomass C,basal respiration,dehydrogenase and BAA-protease.

  5. The Transformation of Agricultural Development towards a Sustainable Future from an Evolutionary View on the Chinese Loess Plateau: A Case Study of Fuxian County

    OpenAIRE

    Yanjun Guo; Yansui Liu; Qi Wen; Yurui Li

    2014-01-01

    The Loess Plateau in China receives lots of attention from around the world. The expansion of bad agricultural practices for hundreds of years aggravated the soil erosion on the Loess Plateau, however, and a lot of efforts were and are being made to reduce the serious soil erosion as well as regional poverty. Agricultural development of the Loess Plateau is still confronted with intricate challenges such as food concerns, environment concerns, and regional poverty. The strategy of developmen...

  6. Spatio-temporal variation of erosion-type non-point source pollution in a small watershed of hilly and gully region, Chinese Loess Plateau.

    Science.gov (United States)

    Wu, Lei; Liu, Xia; Ma, Xiao-Yi

    2016-06-01

    Loss of nitrogen and phosphorus in the hilly and gully region of Chinese Loess Plateau not only decreases the utilization rate of fertilizer but also is a potential threat to aquatic environments. In order to explore the process of erosion-type non-point source (NPS) pollution in Majiagou watershed of Loess Plateau, a distributed, dynamic, and integrated NPS pollution model was established to investigate impacts of returning farmland on erosion-type NPS pollution load from 1995 to 2012. Results indicate that (1) the integrated model proposed in this study was verified to be reasonable; the general methodology is universal and can be applicable to the hilly and gully region, Loess Plateau; (2) the erosion-type NPS total nitrogen (TN) and total phosphorus (TP) load showed an overall decreasing trend; the average nitrogen and phosphorus load modulus in the last four years (2009-2012) were 1.23 and 1.63 t/km(2) · a, respectively, which were both decreased by about 35.4 % compared with the initial treatment period (1995-1998); and (3) The spatial variations of NPS pollution are closely related to spatial characteristics of rainfall, topography, and soil and land use types; the peak regions of TN and TP loss mainly occurred along the main river banks of the Yanhe River watershed from northeast to southeast, and gradually decreased with the increase of distance to the left and right river banks, respectively. Results may provide scientific basis for the watershed-scale NPS pollution control of the Loess Plateau.

  7. Spatio-temporal variation of erosion-type non-point source pollution in a small watershed of hilly and gully region, Chinese Loess Plateau.

    Science.gov (United States)

    Wu, Lei; Liu, Xia; Ma, Xiao-Yi

    2016-06-01

    Loss of nitrogen and phosphorus in the hilly and gully region of Chinese Loess Plateau not only decreases the utilization rate of fertilizer but also is a potential threat to aquatic environments. In order to explore the process of erosion-type non-point source (NPS) pollution in Majiagou watershed of Loess Plateau, a distributed, dynamic, and integrated NPS pollution model was established to investigate impacts of returning farmland on erosion-type NPS pollution load from 1995 to 2012. Results indicate that (1) the integrated model proposed in this study was verified to be reasonable; the general methodology is universal and can be applicable to the hilly and gully region, Loess Plateau; (2) the erosion-type NPS total nitrogen (TN) and total phosphorus (TP) load showed an overall decreasing trend; the average nitrogen and phosphorus load modulus in the last four years (2009-2012) were 1.23 and 1.63 t/km(2) · a, respectively, which were both decreased by about 35.4 % compared with the initial treatment period (1995-1998); and (3) The spatial variations of NPS pollution are closely related to spatial characteristics of rainfall, topography, and soil and land use types; the peak regions of TN and TP loss mainly occurred along the main river banks of the Yanhe River watershed from northeast to southeast, and gradually decreased with the increase of distance to the left and right river banks, respectively. Results may provide scientific basis for the watershed-scale NPS pollution control of the Loess Plateau. PMID:26898934

  8. An approach for detecting five typical vegetation types on the Chinese Loess Plateau using Landsat TM data.

    Science.gov (United States)

    Wang, Zhi-Jie; Jiao, Ju-Ying; Lei, Bo; Su, Yuan

    2015-09-01

    Remote sensing can provide large-scale spatial data for the detection of vegetation types. In this study, two shortwave infrared spectral bands (TM5 and TM7) and one visible spectral band (TM3) of Landsat 5 TM data were used to detect five typical vegetation types (communities dominated by Bothriochloa ischaemum, Artemisia gmelinii, Hippophae rhamnoides, Robinia pseudoacacia, and Quercus liaotungensis) using 270 field survey data in the Yanhe watershed on the Loess Plateau. The relationships between 200 field data points and their corresponding radiance reflectance were analyzed, and the equation termed the vegetation type index (VTI) was generated. The VTI values of five vegetation types were calculated, and the accuracy was tested using the remaining 70 field data points. The applicability of VTI was also tested by the distribution of vegetation type of two small watersheds in the Yanhe watershed and field sample data collected from other regions (Ziwuling Region, Huangling County, and Luochuan County) on the Loess Plateau. The results showed that the VTI can effectively detect the five vegetation types with an average accuracy exceeding 80 % and a representativeness above 85 %. As a new approach for monitoring vegetation types using remote sensing at a larger regional scale, VTI can play an important role in the assessment of vegetation restoration and in the investigation of the spatial distribution and community diversity of vegetation on the Loess Plateau.

  9. Pollen records of Holocene vegetation and climate changes in the Longzhong Basin of the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Pollen records with an average time resolution of 20200 years from Holocene loess sections at Dingxi,Qin'an,and other localities of Gansu Province reveal a detailed history of vegetation and climate changes in the western Loess Plateau.For most time of the Holocene,the landscape was dominated by grasslands or forest steppes.However,during the middle Holocene(7.5-5.8 ka BP),relatively dense forests developed,and the endemic vegetation flourished,suggesting a much warmer and more humid climate condition than the present.Superimposed upon this general pattern are several dry intervals marked by the episodic expansion of grasslands or forest steppe.Xeric vegetation expanded after 3.8 ka BP,indicating a trend towards dry conditions.

  10. Germinable soil seed banks and the restoration potential of abandoned cropland on the Chinese hilly-gullied loess plateau.

    Science.gov (United States)

    Wang, Ning; Jiao, Ju-Ying; Jia, Yan-Feng; Bai, Wen-Juan; Zhang, Zhen-Guo

    2010-09-01

    Poor vegetation cover is generally considered to be a major factor causing soil erosion on the Loess Plateau in China. It has been argued that tree planting restoration is ineffective, and natural re-vegetation is an alternative ecological solution for restoring abandoned cropland and controlling soil erosion. The aims of this study were to investigate the characteristics of soil seed banks and to assess the natural restoration potential of abandoned cropland in the hilly-gullied Loess Plateau. The soil seed bank was identified by the germination method with the soil samples, which were collected at four sampling times (April, August, and October 2005 and August 2006) from 12 plots abandoned 3-30 years prior to sampling. The seed bank densities of all of the samples in the 0-10 cm soil layer varied from 1,067 ± 225 to 14,967 ± 1,606 seeds m(-2). Fifty-one species (24 annual and 27 perennial species) belonging to 18 families were identified, and 39% of these species belonged to the families Compositae and Gramineae. The pioneer species Artemisia scoparia dominated the seed bank, with an average seed density of 3,722 seeds m(-2), and accounted for 74.4% of the seeds in the bank. The local dominant species (such as Lespedeza davurica, Artemisia gmelinii, Bothriochloa ischaemun and Stipa bungeana) of the later succession stages also existed at densities varying from 17 to 1, 383 seeds m(-2). The combination of soil seed bank characteristics, reproductive traits of the species, the specific landscape conditions indicates that the potential to restoring the abandoned croplands in the hilly-gullied Loess Plateau via natural re-vegetation could be substantial. PMID:20694556

  11. Paleoenvironments indicated by the fossil mammalian assemblages from red clay-loess sequence in the Chinese Loess Plateau since 8.0 Ma B.P.

    Institute of Scientific and Technical Information of China (English)

    XUE; Xiangxu; ZHANG; Yunxiang; YUE; Leping

    2006-01-01

    Information from eleven profiles of eolian earthy red silty clay and loess of the middle of the Late Miocene to Holocene age have been studied and correlated. A complete summary profile with projected isotopic ages and fossil-bearing beds has been assembled. The profile is subdivided into 12 stratigraphic units proceeding from the lower (older) to the upper (younger) one. The character of mammalian assemblages contained in each unit was analyzed and the corresponding paleo-climatic environments were deduced. The environmental character of each period and the change from the middle of the Late Miocene at about 8.0 Ma B.P. up to the Holocene progressed from the hot semiarid and semi-moist, warmer-moist, warm-moister of the Late Miocene. To slightly less warm moist, cool-dry, slight-warmer-moister of the Pliocene; later the cool to cold dry periods alternated frequently with the mild semiarid and semi-moist periods of the Quaternary. Vegetation progressed from the grasslands with sparse woods, wooded shrub-grasslands and subtropical forest-grasslands of the Late Miocene age to sparse grasslands and dry grasslands of the Pliocene; and to sparse grasslands, dry grasslands and tundras of the Quaternary. The climate changes in the Neogene were of low-amplitute in a generally warm-humid background. Those of the Quaternary were of higher amplitude with a longer phase. Cool or cold dry and slightly warm semiarid and semi-moist climates alternated on a generally cool-dry background. The tendency since the start of the Quaternary was the change to more northern and western shift in the Loess Plateau, with progressively cooler and dryer conditions. The dramatic uplift of the Qinghai-Xizang (Tibet) Plateau and the forming and expansion of the Arctic ice sheet might be the main reasons of the more pronounced changes in the Quaternary.

  12. History and variability of Asian interior aridity recorded by eolian flux in the Chinese Loess Plateau during the past 7 Ma

    Institute of Scientific and Technical Information of China (English)

    孙有斌; 安芷生

    2002-01-01

    Eolian flux in the Chinese Loess Plateau was reconstructed by measuring the dry bulk density and CaCO3 content of the late Cenozoic loess-paleosol-red clay sequences in the Lingtai profile. Comparison of eolian flux variation between the Lingtai profile and the ODP sites 885/886 in the North Pacific shows a significant wet-dry variability in addition to a gradual drying trend in the dust source regions in interior Asia. Especially, the increase of eolian fluxes from both continental and pelagic eolian sediments indicates a sharp drying of the dust source regions between 3.6 and 2.6 MaBP, which might be attributed to the tectonic uplift of the Tibetan Plateau, which cut down the moisture input to the interior Asia. The average value and variability of eolian flux are higher after 2.6 MaBP than before, which may be related to the Quaternary climatic fluctuations on the glacial-interglacial timescale after the commencement of major Northern Hemisphere Glaciations. The eolian fluxes of the Lingtai profile and Core V21-146 in northwest Pacific show a synchronous variation on the 104-105 a timescale, indicating that the flux variations from both continental and marine records are closely correlated to the Quaternary climatic fluctuation forced by the ice volume changes on a global scale.

  13. Soil erosion and management on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Loess Plateau is well known to the world for its intense soil erosion. The root cause for river sedimentation of Yellow River (Huanghe) and its resultant "hanging river" in certain section is soil and water loss on the Loess Plateau. The Loess Plateau has a long cultivation history, hence population growth, vegetation degeneration and plugging constitute the chief reason for serious soil and water loss on Loess Plateau. This paper analyses several successful cases and failures in soil conservation, presents practical soil conservation technique and related benefit analysis, and discusses some effective methods adopted in China in soil erosion control, research directions and future perspectives on Loess Plateau.

  14. Eolian evidence from the Chinese Loess Plateau: the onset of the Late Cenozoic Great Glaciation in the Northern Hemisphere and Qinghai-Xizang Plateau uplift forcing

    Institute of Scientific and Technical Information of China (English)

    安芷生; 王苏民; 吴锡浩; 陈明扬; 孙东怀; 刘秀铭; 王富葆; 李力; 孙有斌; 周卫健; 周杰; 刘晓东; 鹿化煜; 张云翔; 董光荣; 强小科

    1999-01-01

    On the basis of a newly-constructed record of magnetic susceptibility (SUS) and the depositional rate change of eolian loess-red clay sequences in the last 7.2 Ma BP from the Loess Plateau, together with a comparison of a record of δ18O values from the equatorial East Pacific Ocean and eolian Quartz flux variations from the North Pacific Ocean, the evolutionary process of the Late Cenozoic Great Glaciation in the Northern Hemisphere can be divided into three stages: the arrival stage around 7.2—3.4 Ma BP, the initial stage at about 3.4—2.6 Ma BP, and the Great Ice Age since 2.6 Ma BP. The evolution of the East Asian monsoon is characterized by paired winter and summer monsoons, and it is basically composed of the initial stage of weak winter and summer monsoons, the transitional stage of simuhaneous increase in intensity of winter and summer monsoons, and the prevailing stage of strong winter and weak summer monsoons, or weak winter and strong summer monsoons. The Late Cenozoic global tectonic upl

  15. Changes in grain-size and sedimentation rate of the Neogene Red Clay deposits along the Chinese Loess Plateau and implications for the palaeowind system

    Institute of Scientific and Technical Information of China (English)

    WEN Lingjuan; LU Huayu; QIANG Xiaoke

    2005-01-01

    The wind system responsible for transporting dust onto the Chinese Loess Plateau during the late Miocene and Pliocene is still unknown and recent investigations highlight many controversies. This report aims to investigate spatiotemporal changes in grain-size and sedimentation rate of the Neogene Red Clay deposits in north China and to explore palaeoclimatic changes during the late Miocene and Pliocene, in particular the palaeowind system that transported dust. Samples were collected from eight Red Clay sections on the Loess Plateau. Measurement and analysis show that there is a clear southward decrease in the mean grain-size index and in the coarse particle fraction (>20 μm). At Jiaxian site on the northern Loess Plateau, the average mean grain-size is around 20 μm, while at Lantian site in the south, the mean is around 9 μm. The coarse particle fraction >20 μm makes up 24.4% and 5.6%, at the two sites respectively. This distinct diversity of grain-size in the aeolian Red Clay deposit between the north and south indicate that the palaeodust was transported mainly by northerly low-level winds. The grain-size variations in the Red Clay deposits can also be divided into three stages (the lower, the middle and the upper interval): grain-size of the lower stage is significantly coarser than that of the middle stage, but finer than that of the upper stage. As a consequence, the intensity of palaeowind and desiccation of the dust source region during the late Miocene and Pliocene can be divided into three stages: 6.2-5.4 Ma, 5.4-3.5 Ma and 3.5-2.6 Ma. Strength of the palaeowind during the middle stage (5.4-3.5 Ma) is weaker than that of the previous and subsequent stages and the intensity of palaeowind during the latest stage (3.5-2.6 Ma) is stronger than that of the early time (6.2-5.4 Ma). Variations in the sedimentation rate of the Red Clay deposit can also be divided into three stages: the earlier, the middle and the later interval. The sedimentation rate of the

  16. Dynamic analysis of eco-environmental changes based on remote sensing and geographic information system: an example in Longdong region of the Chinese Loess Plateau

    Science.gov (United States)

    Liu, L. C.; Dong, X. F.; Wang, J. H.

    2007-11-01

    The Chinese Loess Plateau is suffering from severe soil erosion. The eco-environmental changes of the plateau are believed to have an important influence on global eco-environmental sustainability; hence, this problem has attracted considerable attention from scientists around the world. This study has two purposes; application of remote sensing (RS) and geographic information system (GIS) techniques in the dynamic analysis of eco-environmental changes in the semiarid zone; and using the Longdong region of the Chinese Loess Plateau as an example, to make dynamic analysis of the eco-environmental changes of the region during the 1986 2004 period and identify controlling factors. Landsat Thematic Mapper (TM) data at a spatial resolution of 30 m were used for analysis. Two training areas were selected in Jingning and Qingcheng counties for analysis using 10-m resolution SPOT and Landsat TM data. The satellite RS images were obtained from the Institute of Remote Sensing Application (IRSA), Chinese Academy of Sciences (CAS). Each images was rectified by Albers Equal Area Conic projection based on 1:50,000 scale topographic maps after spectrum preparation of the images. To make the precision within 1 or 2 pixels, the accurate coordinative control points of the two systems were identified. Then the interpretation key was established based on the land use/cover survey in the study area. The images were classified into six primary environmental types (farmland, forest, grassland, water, construction area, and desert) and 25 sub-types using a visual image interactive interpretation method to obtain vector and attribute data. The resultant accuracy of the land use/cover classification reached 95%. Finally, the transformation areas and ratios of various eco-environmental types in the region were calculated to obtain the transition matrixes of eco-environmental types in the two training areas, Jingning and Qingcheng. This study demonstrates that satellite RS and GIS techniques

  17. 西宁黄土碎屑锆石年龄特征及其对黄土高原黄土物源的指示意义%ZIRCON AGES OF XINING LOESS: IMPLICATION FOR THE PROVENANCE OF THE LOESS ON CHINESE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    李高军; 车旭东; 肖国桥; 陈忠

    2013-01-01

    Deciphering the provenance of atmospheric dust is critical to understand the paleo-proxies archived in the eolian deposits on Chinese Loess Plateau.While most of evidences indicate major dust sources from the arid lands to the north and northwest of Chinese Loess Plateau,a recent research based on U-Pb geochronology of zircon renewed the hypothesis that the dust transported by westerly winds from north Tibetan Plateau and the Qaidam Basin might be the dominant eolian sources to Chinese Loess Plateau during glacial times.Here we test this hypothesis by analyzing ages of zircon in Xining loess.Xining ( 36.65°N, 101.74°E) is on the hypothetical pass way of dust transportation from north Tibetan Plateau to Chinese Loess Plateau.Compared with the loess on Chinese Loess Plateau, loess in Xining lacks zircon population with age around 360Ma and < 100Ma.In contrast, the materials eroded from Central Asian Orogenic Belt have large population of zircon aged ca.360Ma and <100Ma.Although the major peaks of the zircon age distribution of Xining loess are very similar to that of the loess on CLP,the materials from north Tibetan Plateau could also be transported northwardly to the Alxa arid lands on the northwest of CLP.We thus conclude that loess on CLP is mainly sourced from the Alxa arid lands where materials are received from both north Tibetan Plateau ( Qilian Mountains) in the south and the Central Asian Orogenic Belt (Gobi Altay Mountains) in the north.%物源研究是理解黄土高原风成沉积物中古环境记录的关键一环.众多证据表明,黄土高原西北部的阿拉善高原及其周边广袤干旱地区是黄土高原黄土的主要风尘源区.但是,基于锆石U-Pb同位素地质年代学的证据对此提出了质疑.黄土高原黄土与青藏高原北部物质中的锆石具有相似的年龄分布,预示黄土高原风尘主要以西风搬运的方式来自青藏高原北部,特别是柴达木盆地.本研究通过分析西宁黄土的锆石年

  18. Dependence of the cyclization of branched tetraethers (CBT on soil moisture in the Chinese Loess Plateau and the adjacent areas: implications for palaeorainfall reconstructions

    Directory of Open Access Journals (Sweden)

    H. Wang

    2014-06-01

    Full Text Available Branched glycerol dialkyl glycerol tetraethers (bGDGTs have been show promising for continental paleotemperature studies in loess-paleosol sequences (LPSs. Thus far, however, little is known about the effect of soil moisture on their distributions on the Chinese Loess Plateau (CLP. In this study, the relationships between environmental variables and the cyclization of bGDGTs (the so called CBT index were investigated in a comprehensive set of surface soils in the CLP and its adjacent arid/semi-arid areas. We find that CBT correlates best with soil water content (SWC or mean annual precipitation (MAP for the total sample set. Particularly for the CLP soils, there is a significant positive relationship between CBT and MAP (CBT = −0.0021 · MAP + 1.7, n = 37, R2 = 0.87; MAP range: 210–680 mm. This indicates that CBT is mainly controlled by soil moisture in the alkalescent soils (pH > 7 in arid/semi-arid regions, where it is not sensitive to soil pH. Therefore, we suggest that CBT can potentially be used as a palaeorainfall proxy on the CLP. According to the preliminary CBT–MAP relationship for modern CLP soils, palaeorainfall history was reconstructed from three LPSs (Yuanbao, Lantian, and Mangshan with published bGDGT data spanning the past 70 ka. The CBT-derived MAP records of the three sites consistently show precession-driven variations resembling the speleothem δ18O monsoon record, and are also in general accord with the fluctuations of the respective magnetic susceptibility (MS record, supporting CBT as a reasonable proxy for palaeorainfall reconstruction in LPS studies. Moreover, the comparison of CBT-derived MAP and bGDGT-derived temperature may enable us to further assess the relative timing and magnitude of hydrological and thermal changes on the CLP, independent of chronology.

  19. Dependence of the cyclization of branched tetraethers (CBT) on soil moisture in the Chinese Loess Plateau and the adjacent areas: implications for palaeorainfall reconstructions

    Science.gov (United States)

    Wang, H.; Liu, W.; Zhang, C. L.

    2014-06-01

    Branched glycerol dialkyl glycerol tetraethers (bGDGTs) have been show promising for continental paleotemperature studies in loess-paleosol sequences (LPSs). Thus far, however, little is known about the effect of soil moisture on their distributions on the Chinese Loess Plateau (CLP). In this study, the relationships between environmental variables and the cyclization of bGDGTs (the so called CBT index) were investigated in a comprehensive set of surface soils in the CLP and its adjacent arid/semi-arid areas. We find that CBT correlates best with soil water content (SWC) or mean annual precipitation (MAP) for the total sample set. Particularly for the CLP soils, there is a significant positive relationship between CBT and MAP (CBT = -0.0021 · MAP + 1.7, n = 37, R2 = 0.87; MAP range: 210-680 mm). This indicates that CBT is mainly controlled by soil moisture in the alkalescent soils (pH > 7) in arid/semi-arid regions, where it is not sensitive to soil pH. Therefore, we suggest that CBT can potentially be used as a palaeorainfall proxy on the CLP. According to the preliminary CBT-MAP relationship for modern CLP soils, palaeorainfall history was reconstructed from three LPSs (Yuanbao, Lantian, and Mangshan) with published bGDGT data spanning the past 70 ka. The CBT-derived MAP records of the three sites consistently show precession-driven variations resembling the speleothem δ18O monsoon record, and are also in general accord with the fluctuations of the respective magnetic susceptibility (MS) record, supporting CBT as a reasonable proxy for palaeorainfall reconstruction in LPS studies. Moreover, the comparison of CBT-derived MAP and bGDGT-derived temperature may enable us to further assess the relative timing and magnitude of hydrological and thermal changes on the CLP, independent of chronology.

  20. On the relationship between environmental aridization of the Loess Plateau and soil water in loess

    Institute of Scientific and Technical Information of China (English)

    杨文治; 邵明安; 彭新德; 夏卫生

    1999-01-01

    The similarity between loess palaeo-environment and geographic distribution of modern bioclimatic zones is taken as a starting point; the relationship between the environmental aridization and soil water in loess is discussed from the point view of the soil water energy status and their soil water physical characteristics of modern loessial soils on the Loess Plateau. The soil water content becomes less and less from southeast to northwest, which not only provides favorable conditions for dust production by wind of loess origin, but also reveals that there is obviously a directional change in the environmental drought intensity of the Loess Plateau.

  1. Spatiotemporal variations of Zr/Rb ratio in three last interglacial paleosol profiles across the Chinese Loess Plateau and its implications for climatic interpretation

    Institute of Scientific and Technical Information of China (English)

    WANG HaiBin; LIU LianYou; FENG ZhaoDong

    2008-01-01

    The ratio of Zirconium to Rubidium (Zr/Rb) is suggested to be a better proxy for the East Asian winter monsoon strength than the widely-used grain size distribution. The rationale for the Zr/Rb proxy relies on the following assumptions: (1) Grain size fractionating characteristics during eolian dust transport should be archived in the Zr/Rb ratio records and this assumption is based on the premise that Zr is preferentially enriched in coarser grain size fraction while Rb tend to be enriched in finer grain size fraction; and (2) post-depositional weathering does not change the Zr/Rb ratio due to the immobility of these two elements. To examine these two assumptions, three last interglacial paleosols (S1) from Dingxi, Tianshui and Lantian, along a NW-SE transect across the Chinese Loess Plateau, were geo-chemically investigated. Our results show that the Rb concentration exhibits an increasing trend along the NW-SE transect both in the paleosol (S1) and the measured portions of the loess units (L1 and L2), being supportive to the assumption that Rb is enriched in the fine particles. But we also found that Rb loss did occur to some extent in the three profiles, contradicting to the presumption of Rb immobility during pedogenic processes. The Zr concentration exhibits an expected decreasing trend in the measured portions of the loess units and an unexpected increasing trend in the paleosol along the NW-SE transect. Moreover, the ratios of Zirconium to Hafnium (Zr/Hf) show different variation patterns between interglacial and glacial, implying that Zr-bearing minerals and their resident grain size frac-tions are probably not identical during interglacial and glacial. Thus, the assumption that Zr is enriched in coarse grain size fraction can no longer hold. We conclude that the final Zr/Rb value is not only de-pendent on grain size sorting processes but also on post-depositional alteration and source prove-nance. Under enhanced chemical weathering, especially when

  2. Violet stimulated luminescence dating of quartz from Luochuan (Chinese loess plateau): Agreement with independent chronology up to ∼600 ka

    DEFF Research Database (Denmark)

    Ankjærgaard, C.; Guralnik, B.; Buylaert, Jan-Pieter;

    2016-01-01

    Luminescence dating at the Luochuan loess type (China) section is at present limited to ∼0.1 Ma using quartz blue light stimulated luminescence (BLSL), but can be extended back in time to ∼0.5 Ma by resorting to the more developmental post-infrared infrared stimulated luminescence (post-IR IRSL) ......-1800 Gy) would correspond to the ability to date sediment up to ∼1 Ma back in time, offering a remarkable advance over existing methods.......Luminescence dating at the Luochuan loess type (China) section is at present limited to ∼0.1 Ma using quartz blue light stimulated luminescence (BLSL), but can be extended back in time to ∼0.5 Ma by resorting to the more developmental post-infrared infrared stimulated luminescence (post-IR IRSL...... demonstrate that the Multi-Aliquot Additive-Dose (MAAD) protocol produces a VSL chronology at Luochuan which is in agreement with independent ages up to ∼0.6 Ma. For a more representative environmental dose rate of ∼2 Gy/ka (∼35% lower than at Luochuan), the documented range of MAAD-VSL sensitivity (200...

  3. Research on the slope spectrum of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new concept dealing with digital analysis of loess terrain,slope spectrum,is presented and discussed in this paper,by introducing its characteristic,represen-tation and extracting method from DEMs. Using 48 geomorphological units in dif-ferent parts of the loess as test areas and 5 m-resolution DEMs as original test data,the quantitative depiction and spatial distribution of slope spectrum in China’s Loess Plateau have been studied on the basis of a series of carefully-designed experiments. In addition,initial experiment indicates a strong relationship between the slope spectrum and the loess landform types,displaying a potential importance of the slope spectrum in geomorphological studies. Based on the slope spectrums derived from the 25 m-resolution DEM data in whole loess terrain in northern part of Shaanxi,13 slope spectrum indices were extracted and integrated into a compre-hensive layer with image integration method. Based on that,a series of unsuper-vised classifications was applied in order to make a landform classification in northern Shaanxi Loess Plateau. Experimental results show that the slope spec-trum analysis is an effective method in revealing the macro landform features. A continuous change of slope spectrum from south to north in northern Shaanxi Loess Plateau shows an obvious spatial distribution of different loess landforms. This also proves the great significance of the slope spectrum method in describing the terrain roughness and landform evolution as well as a further understanding on landform genesis and spatial distribution rule of different landforms in the Loess Plateau.

  4. Provenance of Chinese Loess: Evidence from Stable Lead Isotope

    Directory of Open Access Journals (Sweden)

    Feng Wu

    2011-01-01

    Full Text Available Twenty-seven samples of typical loess and paleosol strata collected in nine different regions of the Chinese Loess Plateau (CLP were fractionated into PM1.0, PM2.5, PM10 and Total Suspended Particulates (TSP (particulate matter with aerodynamic diameters less than 1.0, 2.5, 10 and ~30 _ respectively by a resuspension chamber at the Desert Research Institute (DRI; Reno, NV, United States. The amounts and isotope ratios of lead (Pb were quantified in the loess samples. Our size-segregated analysis demonstrated that the Pb isotopic composition in the loess-paleosol deposits was preserved after grain-size sorting and that therefore the isotope ratio can serve as a proxy for source tracing. A similar pattern of Pb isotope ratios was observed for sediment collected from potential source regions and the loess samples suggested that the Gobi and deserts in southern Mongolia and northern China are major sources for the deposits in the CLP. No significant deviation of Pb isotope amount was found between the nine samples of loess and paleosol strata, implying the stability of loess sources during the glacial and interglacial regime.

  5. Dilemmas of Ecological Modernization in China: The Case of the Loess Plateau Watershed Rehabilitation Project

    OpenAIRE

    Wei GUO

    2016-01-01

    Inspired by research on rural sustainability and development in China, this thesis presents a case study on The Loess Plateau Watershed Rehabilitation Project (LPP), a state-led, World Bank-funded environmental improvement and development project in northwestern China initiated in 1994. The focus of the study is on ecological modernization in the Chinese context, seeking to develop a better understanding of the Chinese discourse of sustainable development. Qualitative research methods were em...

  6. Nutrient Lossed in Soils on Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    PENGLIN; WANGJI-ZENG; 等

    1995-01-01

    The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plots and systematical determination of soil nutrients both in sediments and runoff.The results show that the amounts of nutrient losses depended on the amounts of ersoion sediments.Along with sediment,11-197kg nitrogen/hectare and 9-174kg phosphorus/hectare were lost,accounting for 92.46-99.47 percent of the total amount of nitrogen loss and 99.85-99.99 percent of the total amount of phosphorus loss respectively.The nutrient losses,very small in runoff,were mainly attributed to erosion of a few rainstorms during a year.The nutrient level in sediment was mostly higher than that in the original soil.Planting grass evidently redued the losses of soil nutrients.The N level was lower in runoff than in rainfall so that the N loss from runoff could be made up by rainfall.Fertilizer application to crops raised the nutrient level in runoff.

  7. Improving soil enzyme activities and related quality properties of reclaimed soil by applying weathered coal in opencast-mining areas of the Chinese loess plateau

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hua [College of Environment and Resources, Shanxi University, Taiyuan (China); CAS/Shandong Provincial Key Laboratory of Coastal Environmental Process, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Yantai (China); Shao, Hongbo [CAS/Shandong Provincial Key Laboratory of Coastal Environmental Process, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Yantai (China); Institute for Life Sciences, Qingdao University of Science and Technology (QUST), Qingdao (China); Li, Weixiang; Bi, Rutian [Shanxi Agricultural University, Taigu (China); Bai, Zhongke [Department of Land Science Technology, University of Geosciences, Beijing (China)

    2012-03-15

    There are many problems for the reclaimed soil in opencast-mining areas of the Loess Plateau of China such as poor soil structure and extreme poverty in soil nutrients and so on. For the sake of finding a better way to improve soil quality, the current study was to apply the weathered coal for repairing soil media and investigate the physicochemical properties of the reclaimed soil and the changes in enzyme activities after planting Robinia pseucdoacacia. The results showed that the application of the weathered coal significantly improved the quality of soil aggregates, increased the content of water stable aggregates, and the organic matter, humus, and the cation exchange capacity of topsoil were significantly improved, but it did not have a significant effect on soil pH. Planting R. pseucdoacacia significantly enhanced the activities of soil catalase, urease, and invertase, but the application of the weathered coal inhibited the activity of catalase. Although the application of appropriate weathered coal was able to significantly increase urease activity, the activities of catalase, urease, or invertase had a close link with the soil profile levels and time. This study suggests that applying weathered coals could improve the physicochemical properties and soil enzyme activities of the reclaimed soil in opencast-mining areas of the Loess Plateau of China and the optimum applied amount of the weathered coal for reclaimed soil remediation is about 27 000 kg hm{sup -2}. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Influence of intra-event-based flood regime on sediment flow behavior from a typical agro-catchment of the Chinese Loess Plateau

    Science.gov (United States)

    Zhang, Le-Tao; Li, Zhan-Bin; Wang, He; Xiao, Jun-Bo

    2016-07-01

    The pluvial erosion process is significantly affected by tempo-spatial patterns of flood flows. However, despite their importance, only a few studies have investigated the sediment flow behavior that is driven by different flood regimes. The study aims to investigate the effect of intra-event-based flood regimes on the dynamics of sediment exports at Tuanshangou catchment, a typical agricultural catchment (unmanaged) in the hilly loess region on the Chinese Loess Plateau. Measurements of 193 flood events and 158 sediment-producing events were collected from Tuanshangou station between 1961 and 1969. The combined methods of hierarchical clustering approach, discriminant analysis and One-Way ANOVA were used to classify the flood events in terms of their event-based flood characteristics, including flood duration, peak discharge, and event flood runoff depth. The 193 flood events were classified into five regimes, and the mean statistical features of each regime significantly differed. Regime A includes flood events with the shortest duration (76 min), minimum flood crest (0.045 m s-1), least runoff depth (0.2 mm), and highest frequency. Regime B includes flood events with a medium duration (274 min), medium flood crest (0.206 m s-1), and minor runoff depth (0.7 mm). Regime C includes flood events with the longest duration (822 min), medium flood crest (0.236 m s-1), and medium runoff depth (1.7 mm). Regime D includes flood events with a medium duration (239 min), large flood crest (4.21 m s-1), and large runoff depth (10 mm). Regime E includes flood events with a medium duration (304 min), maximum flood crest (8.62 m s-1), and largest runoff depth (25.9 mm). The sediment yield by different flood regimes is ranked as follows: Regime E > Regime D > Regime B > Regime C > Regime A. In terms of event-based average and maximum suspended sediment concentration, these regimes are ordered as follows: Regime E > Regime D > Regime C > Regime B > Regime A. Regimes D and E

  9. Moderate topsoil erosion rates constrain the magnitude of the erosion-induced carbon sink and agricultural productivity losses on the Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    J. Zhao

    2015-09-01

    Full Text Available Despite a multitude of studies, erosion rates as well as the contribution of different processes on Chinese Loess Plateau (CLP remain uncertain. This makes it impossible to correctly assess the impact of conservation programs and the magnitude of the erosion-induced carbon sink. We used a novel approach, based on field evidence, to reassess erosion rates on the CLP before and after conservation measures were implemented. Our results show that the current average topsoil erosion rate is 3–9 times lower than earlier estimates suggested: most sediments are mobilised by gully erosion and/or landsliding. Under 2005 conditions, the combination of topsoil erosion, gully erosion and landslides mobilised 0.81 ± 0.23 Gt yr−1 of sediments and 4.77 ± 1.96 Tg yr−1 of soil organic carbon (SOC: the latter number sets the maximum magnitude of the erosion-induced carbon sink, which is ca. 4 times lower than other recent estimates suggest. The sediment fluxes we calculate are consistent with sediment yields measured in the Yellow River. The conservation programs implemented from the 1950s onwards reduced topsoil erosion from 0.51 ± 0.13 to 0.30 ± 0.08 Gt yr−1 while SOC mobilisation was reduced from 7.63 ± 3.52 to 4.77 ± 1.96 Tg C. Prior to 1950, a geomorphological equilibrium existed whereby the amount of sediment and carbon exported to the Bohai sea was similar to the amount of sediment eroded on the CLP, so that the erosion-induced carbon sink nearly equalled the amount of mobilised SOC. Conservation efforts and reservoir construction have disrupted this equilibrium and most eroded sediments and carbon are now stored on land where part of the SOC may decompose, thereby potentially lowering the strength of the erosion-induced carbon sink. Despite the fact that average topsoil losses on the CLP are still relatively high, the current level of topsoil erosion on the CLP is no major threat to the agricultural productivity of the area, mainly because

  10. Comparing the effect of naturally restored forest and grassland on carbon sequestration and its vertical distribution in the Chinese Loess Plateau.

    Directory of Open Access Journals (Sweden)

    Jie Wei

    Full Text Available Vegetation restoration has been conducted in the Chinese Loess Plateau (CLP since the 1950s, and large areas of farmland have been converted to forest and grassland, which largely results in SOC change. However, there has been little comparative research on SOC sequestration and distribution between secondary forest and restored grassland. Therefore, we selected typical secondary forest (SF-1 and SF-2 and restored grassland (RG-1 and RG-2 sites and determined the SOC storage. Moreover, to illustrate the factors resulting in possible variance in SOC sequestration, we measured the soil δ(13C value. The average SOC content was 6.8, 9.9, 17.9 and 20.4 g kg(-1 at sites SF-1, SF-2, RG-1 and RG-2, respectively. Compared with 0-100 cm depth, the percentage of SOC content in the top 20 cm was 55.1%, 55.3%, 23.1%, and 30.6% at sites SF-1, SF-2, RG-1 and RG-2, suggesting a higher SOC content in shallow layers in secondary forest and in deeper layers in restored grassland. The variation of soil δ(13C values with depth in this study might be attributed to the mixing of new and old carbon and kinetic fractionation during the decomposition of SOM by microbes, whereas the impact of the Suess effect (the decline of (13C atmospheric CO(2 values with the burning of fossil fuel since the Industrial Revolution was minimal. The soil δ(13C value increased sharply in the top 20 cm, which then increased slightly in deeper layers in secondary forest, indicating a main carbon source of surface litter. However the soil δ(13C values exhibited slow increases in the whole profile in the restored grasslands, suggesting that the contribution of roots to soil carbon in deeper layers played an important role. We suggest that naturally restored grassland would be a more effective vegetation type for SOC sequestration due to higher carbon input from roots in the CLP.

  11. Moderate topsoil erosion rates constrain the magnitude of the erosion-induced carbon sink and agricultural productivity losses on the Chinese Loess Plateau

    Science.gov (United States)

    Zhao, Jianlin; Van Oost, Kristof; Chen, Longqian; Govers, Gerard

    2016-08-01

    Despite a multitude of studies, overall erosion rates as well as the contribution of different erosion processes on Chinese Loess Plateau (CLP) remain uncertain, which hampers a correct assessment of the impact of soil erosion on carbon and nutrient cycling as well as on crop productivity. In this paper we used a novel approach, based on field evidence, to reassess erosion rates on the CLP before and after conservation measures were implemented (1950 vs. 2005). We found that current average topsoil erosion rates are 3 to 9 times lower than earlier estimates suggested. Under 2005 conditions, more sediment was produced by non-topsoil erosion (gully erosion (0.23 ± 0.28 Gt yr-1) and landsliding (0.28 ± 0.23 Gt yr-1) combined) than by topsoil erosion (ca. 0.30 ± 0.08 Gt yr-1). Overall, these erosion processes mobilized ca. 4.77 ± 1.96 Tg yr-1 of soil organic carbon (SOC): the latter number sets the maximum magnitude of the erosion-induced carbon sink, which is ca. 4 times lower than one other recent estimate suggests. The programs implemented from the 1950s onwards reduced topsoil erosion from 0.51 ± 0.13 to 0.30 ± 0.08 Gt yr-1 while SOC mobilization was reduced from 7.63 ± 3.52 to 4.77 ± 1.96 Tg C yr-1. Conservation efforts and reservoir construction have disrupted the equilibrium that previously existed between sediment and SOC mobilization on the one hand and sediment and SOC export to the Bohai sea on the other hand: nowadays, most eroded sediments and carbon are stored on land. Despite the fact that average topsoil losses on the CLP are still relatively high, a major increase in agricultural productivity has occurred since 1980. Fertilizer application rates nowadays more than compensate for the nutrient losses by (topsoil) erosion: this was likely not the case before the dramatic rise of fertilizer use that started around 1980. Hence, erosion is currently not a direct threat to agricultural productivity on the CLP but the long-term effects of erosion on

  12. The Oldest Red Clay in the Chinese Loess Plateau and Its Geological Significance%黄土高原最老红粘土的发现及其地质意义

    Institute of Scientific and Technical Information of China (English)

    宋友桂; 李吉均; 方小敏

    2001-01-01

    黄土高原红粘土的形成演化与青藏高原隆起、亚洲季风形成演化等有着十分密切的关系。黄土高原中部厚达303m的朝那黄土-红粘土剖面的古地磁年代学表明红粘土形成于8.1Ma,是目前黄土高原上发现的最老的红粘土沉积。这个事实表明大约在8.1Ma本区构造活动频繁,断裂十分发育,使得鄂尔多斯夷平面解体,六盘山地区呈断块上升,而六盘山以东地区下沉接受红粘土沉积。这可能指示了毗邻的青藏高原有一次显著的构造隆升。%The widely distributed red clay sediments underlying the ChineseLoess Plateau record truly Neogene environmental evolution, and the initiation and development of red clay sedimentation are intrinsically related to the uplift processes of the Tibetan Plateau and the evolution of East Asia monsoon system. The red clay is regarded as a focal proxy on past global changes. In this paper, the magnetostratigraphy of a new loess_red clay section, which was found recently, and its geological significance are reported. The new section is located at Chaona of Lingtai county(107.2°E, 35.1°N) in the central Loess Plateau. The loess_red clay deposit at Chaona is about 303 m thick.It consists of a complete Quaternary Loess_soil sequence with a thickness of about 175m and 128 m of Late Tertiary red clay deposits. About 400 orientated block samples and 3600 bag samples were collected from this section. The magnetic remanence was measured at the Paleomagnetism Laboratory, both Lanzhou institute of Geology, CAS and institute of Geophysics and Geology, CAS. Based on the correlation with the standard geomagnetic polarity time scale, the magnetostratigraphic results indicate that the age of Chaona red clay extends to 8.1 Ma, which is at least 0.5 Ma older than previously reported, and it is the oldest red clay deposition in the Loess Plateau. The commencement of red clay at ~8.1 Ma may imply that the Ordos planation surface

  13. The Transformation of Agricultural Development towards a Sustainable Future from an Evolutionary View on the Chinese Loess Plateau: A Case Study of Fuxian County

    Directory of Open Access Journals (Sweden)

    Yanjun Guo

    2014-06-01

    Full Text Available The Loess Plateau in China receives lots of attention from around the world. The expansion of bad agricultural practices for hundreds of years aggravated the soil erosion on the Loess Plateau, however, and a lot of efforts were and are being made to reduce the serious soil erosion as well as regional poverty. Agricultural development of the Loess Plateau is still confronted with intricate challenges such as food concerns, environment concerns, and regional poverty. The strategy of development towards sustainability offers a possible and important way to face the challenges. This study tried to develop a holistic “variation-selection-replication-retention” model to analyze the transformation of agricultural development from an evolutionary view which is generally integrative. It is indicated that policies should be lively and vibrant organisms full of innovations owning to ever-changing environment in the evolutionary view. Under this analytical framework, one possible path from serious soil erosion region to region with sustainable agriculture could be recognized in the case study of Fuxian County: serious soil erosion regions → regions with poor production conditions → production-optimized regions → regions with developed agriculture → regions with sustainable agriculture. Diversified integrative development is suggested due to regional differences and the possible developing order in Fuxian County. State-subsidized “Grain for Green” policy and diversified land use are necessary for the transformation of serious soil erosion regions which are usually trapped in regional poverty. To the transformation of regions with poor production conditions, a state-subsidized “production optimization” policy and diversified land use deserve to be considered, due to regional poverty in regions with poor production conditions. Agricultural scale operation is priority for the transformation of production-optimized regions towards

  14. 黄土高原风成沉积物磁化率各向异性研究%ANISOTROPY OF MAGNETIC SUSCEPTIBILITY OF EOLIAN SEDIMENTS IN THE CHINESE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    张睿; 岳乐平; 弓虎军; 张云翔; 李建星

    2012-01-01

    The magnetic susceptibility of the Chinese loess-paleosol sequence in the Northwest China represents a proxy climate index related to the East Asian summer monsoon intensity. In contrast to the loess deposits, the magnetic susceptibility is almost independent of each other in the red clay, thus challenging the validity of the readily measurable magnetic susceptibility in describing the monsoon evolution history recorded by the red clay. Concentration variation of pedogenic magnetite and maghemite produced during pedogenesis is considered as the main reason for variation of magnetic susceptibility of the loess-red clay sediments. However no identical view on formation of magnetite and maghemite via inorganic precipitation or organic process was proved,the latter including the mediation of Fe-reducing bacteria which may be termed a ' Biologically Induced Mineralisation' ( BIM ) process and magnetotactic bacteria process called a ' Biologically Organised Mineralisation ' ( BOM ) process. The organic matter content and morphological characteristics of magnetic mineral in the eolian sediments have great potential for the study of magnetic minerals genesis and variation of magnetic susceptibility. In this paper,the Zhaojiachuan section (35°45'N, 107°49'E) in Xifeng town is selected for this study. This section is located in the centre of Dongzhiyuan which is the largest Yuan in the Chinese Loess Plateau, Gansu Province. The present day mean annual temperature is about 8. 7℃ with a range of -22. 4 ~35. 1℃ ,and the mean annual precipitation is 555mm in this region. The profile contains an upper about 170m alternating loess-paleosol sequence and a lower red clay with a thickness of about 55m. The loess-paleosol sequence is traditionally subdivided into five major stratigraphic units. From the surface downward these are; Holocene Black Loam ( S0 ) , late Pleistocene Malan Loess(L1 ) , Middle Pleistocene Upper Lishi Loess ( S1-L9) and Lower Lishi Loess ( S9 ~ L15

  15. Natural vegetation of geological and historical periods in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The study of natural vegetation of geological and historical periods in the Loess Plateau is an important scientific and practical issue for the development of northwestern China. However, interpretation of the natural vegetation before human reclamation is still controversial. The paper aims to analyze the potential factors that cause the difference in knowledge of Holocene natural vegetation developing in different topographies of the Loess Plateau. The distribution of paleovegetation in this region shows significant difference among rocky mountains, valleys, and Yuan lands (the plain area), i.e. it does not follow the natural vegetation zonation, as that in eastern China does. The Yuan lands with thick loess accumulation were never covered by a vast of dense forests during the Holocene. Forests (or open forests) developed preferably in valleys in the southern part of the Plateau and rocky mountains on the Plateau during the warm period of the Holocene. Some of local vegetation outside of the Loess Plateau are more subjected to the control of geomorphology and ground water.

  16. Organic carbon isotope and molecular fossil records of vegetation evolution in central Loess Plateau since 450 kyr

    NARCIS (Netherlands)

    Zhou, Bin; Wali, Guzalnur; Peterse, Francien; Bird, Michael I.

    2016-01-01

    Significant uncertainties remain regarding the temporal evolution of natural vegetation during the Quaternary, and drivers of past vegetation change, on the Chinese Loess Plateau (CLP). This study presents analyses of total organic carbon isotopic composition (TOC) and n-alkane ratios (C31/C27) from

  17. Autumn Daily Characteristics of Land Surface Heat and Water Exchange over the Loess Plateau Mesa in China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Loess Plateau, located in northern China, has a significant impact on the climate and ecosystem evolvement over the East Asian continent. In this paper, the preliminary autumn daily characteristics of land surface energy and water exchange over the Chinese Loess Plateau mesa region are evaluated by using data collected during the Loess Plateau land-atmosphere interaction pilot experiment (LOPEX04), which was conducted from 25 August to 12 September 2004 near Pingliang city, Gansu Province of China. The experiment was carried out in a region with a typical landscape of the Chinese Loess Plateau, known as "loess mesa". The experiment's field land utilizations were cornfield and fallow farmland, with the fallow field later used for rotating winter wheat. The autumn daily characteristics of heat and water exchange evidently differed between the mesa cornfield and fallow, and the imbalance term of the surface energy was large. This is discussed in terms of sampling errors in the flux observations footprint; energy storage terms of soil and vegetation layers; contribution from air advections; and low and high frequency loss of turbulent fluxes and instruments bias. Comparison of energy components between the mesa cornfield and the lowland cornfield did not reveal any obvious difference. Inadequacies of the field observation equipment and experimental design emerged during the study, and some new research topics have emerged from this pilot experiment for future investigation.

  18. Review of Digital Elevation Model (DEM) Based Research on China Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Tang Guo'an; Ge Shanshan; Li Fayuan; Zhou Jieyu

    2005-01-01

    The Loess Plateau is one of the hot research areas for its specific geographical features. In resent years, with the establishment of national multi-scale DEMs and the perfection of DEM based digital terrain analysis methods, new thoughts and methodologies have been constructed for the Loess Plateau research. This paper introduces the characteristics of DEM data, analyses the development stages of DEM applied in the Loess Plateau research, and discusses its further possible research direction. More discussions are focused on slope spectrum and its concept, as well as the significance in the Loess Plateau research.

  19. An erosional hiatus in Chinese loess sequences revealed by closely spaced optical dating

    Institute of Scientific and Technical Information of China (English)

    LU Huayu; Thomas Stevens; YI Shuangwen; SUN Xuefeng

    2006-01-01

    Chinese loess deposits are some of the best continental records of palaeoclimatic and palaeoenvironmental changes in the late Cenozoic. Many investigations have shown that the long-time climate variations recorded by the loess-paleosol sequences can be correlated with global environmental changes. However, there are still some foundational questions concerning loess deposition that are not well answered, casting uncertainty on many previous conclusions, especially high-resolu- tion palaeoclimatic records. In this study, three typical loess-paleosol sections spanning the last glacial cycle were closely sampled for optically stimulated luminescence (OSL) dating and palaeoclimate interpretation along a northwest-southeast transect in Chinese Loess Plateau. Results show that there is a 4-5 ka hiatus in the typical loess deposits, and as a consequence suggests that the loess record is not continuous over millennial time scales. As such, previous conclusions on climatic and environmental changes at millennial-centennial time scale, reconstructed through the loess record, should be reinvestigated. The erosional hiatus may be forced by a period with strengthened East Asian winter monsoon and the less vegetation cover in the investigated sites.

  20. Climate as the dominant control on C3 and C4 plant abundance in the Loess Plateau: Organic carbon isotope evidence from the last glacial-interglacial loess-soil sequences

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Abundance of C3 and C4 photosynthesis plants can be inferred relatively from stable carbon isotopic composition of organic matter in soils. The samples from five sequences of the last glacial-interglacial loess-soil in the Chinese Loess Plateau have been measured for organic carbon isotopic ratios (? 13Corg). The organic carbon isotope data show that relative abundance (or biomass) of C4 plants was increased ca. 40% for each sampling site from the last glacial maximum (LGM) to Holocene optimum, and increased southeastward on the Loess Plateau during both periods of LGM and Holocene. Statistic analyses on the steady maximumδ 13Corg values of Holocene soils and modern climatic data from the Loess Plateau and Inner Mongolia indicate that the C4 plant abundance increases with increasing temperature and decreasing precipitation. The C4 plant abundance is related much closer with mean April temperature and precipitation than annual. These results lead us to deduce following conclusions. First, temperature is the major factor for control on variations in C4 plant abundance in the Loess Plateau from the last glacial to interglacial. In the absence of favorable temperature condition, both of low moisture and low atmospheric CO2 concentration are insufficient to drive an expansion of the C4 plants in the plateau. Second, ? 13Corg in the loess-paleosol sequences, as a proxy of the relative abundance of C4 plants in the Loess Plateau, could not be used as an indicator of changes in the summer monsoon intensity unless the temperature had changed without great amplitude. Since all C4 plants are grasses, finally, the increase of the C4 plants supports that forest has not been dominant in the ecosystem on the Loess Plateau during Holocene although precipitation and atmospheric CO2 were largely increased relative to those during LGM.

  1. A mathematical model of soil moisture spatial distribution on the hill slopes of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    FU; Bojie

    2001-01-01

    in China, Ser. B, 1995, 38(2): 238-244.[14]Zhu, R. X., Zhou, L. P., Laj, C. et al., The Blake geomagnetic polarity episode recorded in Chinese Loess, Geophys. Res. Lett., 1994, 21(8): 697-700.[15]Kligfield, R., Channel, J. E. T., Widespread remagnetization of Helvetic limestones, J. Geophys. Res., 1981, 86: 1888-1900.[16]Maher, B. A., Thompson, R., Zhou, L. P., Spatial and temporal reconstruction of changes in the Asian paleomonsoon: A new mineral magnetic approach, Earth Planet Sci. Lett., 1994, 125: 461-471.[17]Liu, X. M., Rolph, T., Bloemendal, J. et al., Quantitative estimates of paleoprecipitation at Xifeng in the Loess Plateau of China, Palaeogeogr. Palaeoclim. Palaeoecol., 1995, 113: 243-248.[18]Thompson, R., Maher, B. A., Age models, sediment fluxes and paleoclimatic reconstructions for the Chinese loess and paleosol sequences, Geophys. J. Int., 1995, 123: 611-622.[19]Liu, T. S., Guo, Z. T., Liu, J. Q. et al., Variations of eastern Asian monsoon over the last 140000 years, Bull. Soc. Geol. France, 1995, 166: 221-229.[20]Guo, Z. T., Liu, T. S., Guiot, J. et al., High frequency pulses of East Asian monsoon climate in the last two glaciations: link with the North Atlatic, Climate Dynamics, 1996, 12: 701-709.[21]Han, J. M., Lü, H. Y., Wu, N. Q. et al., The magnetic susceptibility of modern soils in China and its uses for paleocli-mate reconstruction, Studia Geoph et Geod., 1996, 40: 262-275.[22]Zhu, R. X., History of anisotropy of the magnetic susceptibility and its implications: Preliminary results along an E-W transect of the Chinese Loess Plateau, Geophys. Res. Abs., 2000, 2: 226.

  2. RECENT ADVANCES IN RED CLAY ENVIRONMENTAL MAGNETISM ON THE CHINESE LOESS PLATEAU%中国黄土高原红粘土环境磁学研究进展

    Institute of Scientific and Technical Information of China (English)

    聂军胜; 昝金波; 宋友桂

    2012-01-01

    The Late Miocene-Pliocene deposited red-clay sequence on the Chinese Loess Plateau is encoded with important information of past climate changes. However, in comparison to the overlying Pleistocene loess-paleosol sequence,it has received much less study. In this paper, we review recent progress in environmental magnetic studies of the red-clay sequence. Past studies reveal that there is no major difference in terms of magnetic enhancement mechanisms; I. E, magnetic enhancement in both the loess-paleosol sequence and the red-clay sequence are mainly caused by< 100 nm magnetite or maghemite grains produced during pedogenesis. However, much is unknown about concentration variations and their formation mechanisms and magnetic transform routes of weakly magnetic minerals hematite and goethite in the red-clay sequence. Two contrasting formation mechanisms of hematite have been proposed. Classic viewpoints argue that the hematite forms by dehydrating ferrihydrites and thus high temperature and dry climate favor formation of hematite; whereas some authors propose that production of hematite results from aging of maghemite grains which are in turn produced by aging of ferrihydrites. In terms of paleoclimate implications, magnetic data suggest that during the Late Pliocene, the East Asian summer monsoon (EASM)was stronger than Early Pliocene periods. If future studies support this conclusion, then many proxies used to indicate the intensity of the EASM might be invalid. Obviously, future studies need to put more effort into understanding concentration variations of hematite and goethite in the red-clay sequence and their formation mechanisms. The paybacks would be a clear understanding of climate history during the Pliocene period,a possible analog for future warmer climate.%黄土高原地区的红粘土沉积序列蕴含着晚新生代气候变化和高原隆升的信息.最近的研究表明,红粘土与上覆的黄土-古土壤序列具有相似的磁学性质,用环境

  3. ORGANIC MATTER RECORD OF XIFENG EOLIAN DEPOSITS AND ITS DECIPHERMENT FOR THE PALEOCLIMATIC PROXY OF MAGNETIC SUSCEPTIBILITY OF THE LOESS-RED CLAY SEQUENCES IN CHINESE LOESS PLATEAU%西峰黄土-红粘土序列有机质记录及其对磁化率古气候意义启示

    Institute of Scientific and Technical Information of China (English)

    谢巧勤; 陈天虎; 徐晓春; 孙玉兵

    2012-01-01

    大量研究证实成壤磁铁矿和磁赤铁矿是黄土-红粘土磁化率变化主要原因,但是对这些磁性矿物起源于无机沉淀还是生物作用尚需深入研究.为此,本文选择黄土高原200余米厚的西峰黄土-红粘土序列为主要研究对象,采用化学分析和透射电镜手段,对其中有机质含量和磁性矿物成因进行研究,结果表明:S5以来的沉积层有机质含量相对较高,集中在0.25% ~0.50%之间,有机质含量变化与黄土和古土壤层磁化率变化基本一致,即有机质高值对应磁化率高值,有机质与磁化率值成正相关;S5以下至午城黄土底部不仅有机质含量降低而且变化幅度减小;红粘土沉积层中,虽然不能完全遵循磁化率高值对应有机质高值,但基本符合峰-峰和谷-谷对应规律.有机质和磁化率的相关性以及透射电镜研究表明,生物成因磁性矿物是风尘序列磁化率变化的主要原因,有机质含量高低反映风尘序列成壤过程中生物地球化学强度变化,生物将磁化率和古气候密切联系起来.黄土和红粘土磁化率古气候意义相似,但是由于黄土和红粘土形成于不同气候背景下,不能仅仅利用二者磁化率大小对比反演古气候,利用表土磁化率重建古气候要考虑气候载体形成的气候背景差异.%It has been confirmed that the aeolian loess-red clay sequence on the Chinese Loess Plateau( CLP) records the evolutionary information of East Asian Monsoon, which is still debated by various different views even with the same paleoclimatic indicators, such as the hematite content. Previous research on soil explores that the content of hematite is closely sensitive to humidity fluctuation,and has close relevance with the environmental evolution. However,there are conflicting views on the paleoclimatic significance of hematite proxy. The trace hematite concentration in loess-paleosol samples could be detected through the analysis of

  4. Remote mineral aerosols in Westerlies and their contributions to the Chinese loess

    Institute of Scientific and Technical Information of China (English)

    张小曳; 沈志宝; 张光宇; 陈拓; 柳海燕

    1996-01-01

    The concentrations of 28 trace and rare earth elements in the aerosol particle samples were determined for a site at 4800m above the sea level on the Qinghai-Xizang Plateau. The mass of the particulate materials in the mid-troposphere atmosphere over this site is dominated by local dust particles (70%) and remote ones in Westerlies (25%). On the basis of the main dust-derived elements (Al, Fe, Mg and Sc) and corresponding data from the Chinese deserts, an elemental tracer system has been established to proportion the dust input to the loess deposited on the center of the Loess Plateau during the last glacial cyde, which suggests that the contribution of the remote dust in Westerlies is much smaller than that of the Chinese deserts.

  5. [Soil moisture dynamics in forest land and wasteland of Loess Plateau].

    Science.gov (United States)

    Sun, C; Huang, B; Liu, S; Chen, H

    2000-08-01

    The dynamics of soil moisture stored in a wasteland and in a forest land in the sub-humid climate region of the Loess Plateau was measured with neutron moisture meter for three successive years. Within the depth of 0-320 cm, the increment of soil water in the test 3 years was respectively -165.7 mm, -15.2 mm and -115.2 mm at the upper and lower position on north slopes and the lower position on south slope of the wasteland. Soil water increased by 17.2 mm at the upper position on north slope of the Chinese pine forest land, after > 380 mm water was consumed yearly by tree transpiration. It is suggested that forest land is essentially different from wasteland in soil water income/expense. The necessity of conducting the approaches for gaining available water of forest land was put forward. PMID:11767669

  6. Last glacial aeolian dynamics at the Titel loess plateau (Vojvodina, Serbia)

    Science.gov (United States)

    Marković, S. B.; Bokhorst, M. P.; Machalett, B.; Štrbac, D.; Hambach, U.; Basarin, B.; Svirčev, Z.; Stevens, T.; Frechen, M.; Vandenberghe, J.

    2009-04-01

    The Titel loess plateau (Vojvodina, Serbia) is situated at the confluence of the rivers Danube and Tisa, in the southeastern part of the Bačka subregion. Various phases of fluvial erosion have shaped the ellipsoid form of the plateau, which is characterized by steep slopes on the margins. The Titel loess plateau is a unique geomorphologic feature, further emphasising the wide diversity of the loess landforms. The plateau is an island of loess with a maximum length of about 16 km and a maximum width of 7.2 km. Thick loess deposits of between 35 and 55 m are intercalated by 5 main pedocomplexes likely deposited thought the last 5 glacial/interglacial cycles. Steep loess cliffs expose several important sections for understanding climatic and environmental change during the middle and late Pleistocene in the region. The succession of palaeosols through the sequence strongly suggests a transition from humid interglacial climates in the middle Pleistocene, to drier interglacial climates in the late Pleistocene. Past aeolian dynamics have been reconstructed using magnetic susceptibility, grain size, geochemical and malacological investigations by depth in the thick last glacial unit. Luminescence dating and magnetic susceptibility inter-profile correlation provide the chronological framework. Lower last glacial loess unit V-L1L2 is loosely cemented porous sandy loess, with occasional fine laminations and thin, fine sand beds. Identified malacofauna indicates very dry climatic conditions and poor steppic vegetation. It is hypothesized that while the last glacial vegetation cover is extremely sparse, significant sedimentation rates during the lower last glacial can be explained by the presence of a cyanobacterial crust. Protection of loess sediments from deflation by the presence of a cyanobacterial crust is observed at present in loess quarries (Ruma, Crvenka, Petrovaradin). The middle glacial was warmer and relatively moist, as indicated by an increase in clay content

  7. Monthly Water Budget of Small Basin in Northern of Loess Plateau,China

    Institute of Scientific and Technical Information of China (English)

    HUANG Jinbai; HINOKIDANI Osamu; YASUDA Hiroshi; Kimura Reiji; ZHENG Jiyong

    2010-01-01

    The objective of this study was to analyze the water budget of a small basin in the northern of Loess Plateau. A small basin, Liudaogou in the northern Loess Plateau was chosen as the study area. The numerical calculation of surface runoff was applied to results of the field survey, and components of monthly water budget were estimated. The unit area of 1 km was selected as the index area for the estimation. A component of habitant water consumption was added to the water budget to consider the contribution of human activity. Results indicated that the water storage was negative in May, June and July while the annual amount was approximately 0.0. Evaportanspiration attained maximum in August and its annual total accounted for 74.2% of annual precipitation. Results of this study are significant for the sustainable water conservation and utilization in the northern of Loess Plateau where annual water resources are relatively deficient.

  8. Desert-steppe migration on the Loess Plateau at about 450 kaBP

    Institute of Scientific and Technical Information of China (English)

    ZHAOJingbo

    2005-01-01

    According to the field investigation, observation by an electronic microscope and x-ray identification and chemical analysis, desert-steppe migration in the Loess Plateau at about 450 kaBP was studied. The data show that gypsum illuvial horizon indicating the desert-steppe environment developed in the early stage of the formation of the fifth layer loess in Shaoling tableland in Chang'an and Bailu tableland in Xran of Shaanxi are situated in the southern Loess Plateau. This indicates that remarkable drying occurred, a large-scope migration of desert steppe took place toward south and the climate zone migrated 5 degrees in latitude to south which is the largest migration range indicated by geochemical indexes. The desert-steppe and more wild environment distributed widely on the Loess Plateau at that time. The development of gypsum also indicates that the climate changed at 450 kaBP from monsoon climate to nonmonsoon climate in the Loess Plateau, and the region was not affected by summer monsoon and was in the cold and dry environment of nonmonsoon climate. Annual mean nrecinitation was about 200 rnm. 400 mm less at that time than at oresent.

  9. Variation Characteristics of Sunshine Hours and Its Reason Analysis over Loess Plateau of Shaanxi

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] By using the climate tendency rate,climate trend coefficient and linear correlation,the temporal and spatial variation characteristics of sunshine hours in Loess Plateau of Shaanxi in recent 50 years were analyzed.Moreover,the main reason for inducing variation of sunshine hours in the zone was discussed.[Result] In recent 50 years,the variation of annual sunshine hours...

  10. A Probe into the Dynamic Change of Land Use in the Southern Loess Plateau

    OpenAIRE

    Guo, Bin; ZHANG Li

    2013-01-01

    In order to reveal the characteristics of land use change in the south loess plateau, this paper tentatively divided Loess Plateau into North and South under the support of GIS, and then introduced land use spatial temporal dynamic model, analyzed land use dynamic change in provincial scale. The results showed: during the 25 years, construction land area increased from 3 555.99 km2 to 4 794.28 km2, unused land decreased by 0.02 percentage points, forest land area increased from 51 011.31 km2 ...

  11. Differences in hydrological responses for different vegetation types on a steep slope on the Loess Plateau, China

    Science.gov (United States)

    Duan, Liangxia; Huang, Mingbin; Zhang, Luodan

    2016-06-01

    Extensive vegetation restoration practices have been implemented to control soil erosion on the Loess Plateau, China. However, no strict guidelines are available to determine the most suitable plant species for vegetation restoration within a given area. The objective of this study was to quantify the changes of each component (soil water storage, surface runoff, and actual evapotranspiration) of a water balance model and soil loss over time under eight different vegetation types, and to further determine the optimal vegetation type for soil and water conservation and sustainable ecological restoration on the steep slopes (>25°) on the Loess Plateau. The results indicated that vegetation type substantially affected soil water storage and that the greatest soil water storage in both the shallow (0-2 m) and the deep soil layers (2-5 m) occurred under Bothriochloa ischaemum L. (BOI). Vegetation type also affected surface runoff and soil losses. The most effective vegetation types for reducing soil erosion were BOI and Sea-buckthorn (Hippophae rhamnoides L.), while Chinese pine (Pinus tabulaeformis Carr.) and Chinese pine + Black locust (Robinia pseudoacacia L.) were the most ineffective types. Soil water dynamics and evapotranspiration varied considerably among the different vegetation types. A soil water surplus was only found under BOI, while insufficient water replenishment existed under the other seven vegetation types. The higher water consumption rates of the seven vegetation types could result in soil desiccation, which could lead to severe water stresses that would adversely affect plant growth. This study suggested that both vegetation type and its effect on controlling soil erosion should be considered when implementing vegetation restoration and that BOI should be highly recommended for vegetation restoration on the steep slopes of the Loess Plateau. A similar approach to the one used in this study could be applied to other regions of the world confronted

  12. Two pedogenic models for paleoclimatic records of magnetic susceptibility from Chinese and Siberian loess

    Institute of Scientific and Technical Information of China (English)

    LIU XiuMing; LIU TungSheng; Paul HESSE; XIA DunSheng; Jiri CHLACHULA; WANG Guan

    2008-01-01

    The magnetic susceptibility (MS) of Chinese loess showing a general proportional relationship to pedogenic grade has been widely recognized and used for reconstruction of paleoclimate by Quaternary scientists. The in-situ pedogenic enhancement of ferrimagnetic content is normally believed to be the main reason for the increase of susceptibility in soil units. However, this pattern of high magnetic susceptibility in palaeosols, and low values in loess, are not replicated in some loess deposits. Siberian loess deposits display a completely opposite susceptibility behavior: high values in loess and low values in palaeosols. This inverse relationship has been explained by the idea that magnetic susceptibility is reflecting the magnitude of an aeolian ferrimagnetic component of consistent mineralogy, the grain size of which is related to average wind velocity. Our magnetic study of Siberian samples in this paper suggests that there are notable differences in magnetic properties between Siberian loess and developed palaeosols, not only in magnetic grain-size and concentration but also in magnetic mineralogy. This evidence is difficult to explain fully through variation in wind strength alone, but implies that the low magnetic susceptibility values in the Siberian paleosol units are a reflection, at least in part, of the alteration of the ferrimagnetic content by post-depositional processes. The Loess Plateau is a very arid area where potential evaporation is always higher than precipitation; pedogenesis occurs under dry oxidising conditions. The Siberian Kurtak region is located on the edge of the tundra where it is always wet and saturation during interglacials will lead to a reducing pedogenic environment. Ferrimagnetic minerals under this condition will be destroyed, resulting in lower magnetic susceptibility.Therefore, great care should be taken when using susceptibility values for paleoclimatic reconstruction.

  13. Discharge and sediment measurements at the outlet of a watershed on the Loess plateau of China

    NARCIS (Netherlands)

    Elsen, van den H.G.M.; Hessel, R.; Liu Baoyuan,; Trouwborst, K.O.; Stolte, J.; Ritsema, C.J.; Blijenberg, H.

    2003-01-01

    A dam and weir system was constructed to measure the discharge of water and sediment from a selected small catchment on the Loess plateau in China. The aim of the system described here was to collect data on discharge and sediment content during occasional summer storms. These data can be used for c

  14. Potential productivity of the Miscanthus energy crop in the Loess Plateau of China under climate change

    International Nuclear Information System (INIS)

    With a vast area of marginal land, the Loess Plateau of China is a promising region for large-scale production of second-generation energy crops. However, it remains unknown whether such production is sustainable in the long run, especially under climate change. Using a regional climate change model, PRECIS, we analyzed the impact of climate change on Miscanthus production in the Loess Plateau. Under three emission scenarios, A2, B2, and A1B, both the average yield and total area capable of supporting Miscanthus production would increase continuously in the future period (2011–2099). As a result, the total yield potential in the region would increase by about 20% in this future period from the baseline period (1961–1990). This was explained primarily by predicted increases in temperature and precipitation across the Loess Plateau, which improved the yield of the perennial C4 plants relying exclusively on rainfed production. The areas that are currently too dry or too cold to support Miscanthus production could be turned into energy crop fields, especially along the arid–semiarid transition zone. Thus the Loess Plateau would become increasingly desirable for growing second-generation energy crops in this century, which could in turn contribute to soil improvement and ecological restoration of the region. (letter)

  15. Paleo-environmental study on the growth of magnetotactic bacteria and precipitation of magnetosomes in Chinese loess-paleosol sequences

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    405 samples were collected from L5-S5-L6 in consideration of obvious variations in susceptibility of the geological sections, which are section Xifeng in Gansu Province and section Duanjiapo in Shaanxi Province for study of magnetotactic bacteria (MB) and magnetosomes (MS)in Chinese loess-paleosol sequences. MB in each sample were observed by TEM after being cultured under 8-18℃, room temperature (RT), 25℃, 26℃ and 30℃ conditions. In general, MB are distributed widely in loess-paleosol sequences, fewer in loess layers with predomination of vibriod in shape. However, there are more MB in paleosol layers with morphological varieties such as roddish, vibriod and occasionally approximately coccus. The magnetosomes (MS) in MB of paleosol are usually arranged in chains along the cells. It was also found that MB growth and MS formation are associated with the environment in which MB live. It can be inferred from the distributions of MB and MS that the paleoclimates fluctuated during the formation of loess-paleosol sequences in the Chinese Loess Plateau. The climate became gradually warmer but displayed more frequent fluctuations from the northwest to the southeast of the Plateau.

  16. Heavy-mineral analysis and provenance of Yellow River sediments around the China Loess Plateau

    Science.gov (United States)

    Pan, Baotian; Pang, Hongli; Gao, Hongshan; Garzanti, Eduardo; Zou, Yu; Liu, Xiaopeng; Li, Fuqiang; Jia, Yunxia

    2016-09-01

    In its upper-middle reaches the Yellow River has high sand contents after traversing through large areas of desert and the China Loess Plateau. Understanding riverbed sediment composition in the channel is critical for the interpretation of the potential provenance, aeolian sand transport and the linkage between the Loess Plateau and the Yellow River. To address these issues, we collected 52 samples from the modern riverbed, proximal deserts, and major tributaries and used analyses of grain size, grain morphology, and heavy-mineral compositions, to establish the spatial distribution and characteristics of source regions and riverbed sediments. The heavy-mineral assemblages demonstrate significant variations for the different sections of the Yellow River. The riverbed samples from the upper reach are dominated by opaque minerals (limonite and magnetite), amphibole and epidote, with minor zircon, tourmaline and rutile. Riverbed sediments from the middle reach are garnet-rich, reflecting the widespread distribution of Mesozoic sandstones. This variability closely reflects the source regions. Our data show that seasonal tributaries (the "Ten Great Gullies") carrying detritus from the Ordos Plateau may account for the localized high garnet concentrations in the Inner Mongolia section of the upper reach. Scanning electron microscope (SEM) imaging of quartz grains show that the river sediments are characterized by composite microtextures acquired in both fluvial and eolian environments of the Hedong, Ulan Buh and Kubuq Deserts. The mineralogical composition in the upper reach (Lanzhou-Yinchuan) is similar to that of sediments in the Loess Plateau and Northeast Tibet Plateau (Western Lanzhou). However, the composition differs markedly from that in the Inner Mongolia section of the upper and middle reaches. This variation indicates that in the upper reach the Northeast Tibet Plateau contributes significant volumes of sediment to the Yellow River and Loess Plateau, but

  17. Simulation for Artificial Forest Succession in Hilly-gully Area of Loess Plateau, China

    Science.gov (United States)

    Zhao, J., Jr.; Zhao, Z.; Yang, Y.

    2015-12-01

    The wide and large afforestation caused the great changes of surface albedo, water cycles, soil compositions and regional climate conditions on the Loess Plateau. There was increasing evidence showed that many problems had been occurred since ecological protection program began. Whether the artificial forest would adapt to environmental conditions on Loess Plateau is still controversial. In this paper, LANDIS-II, a spatially explicit model which included extension modules such as succession, disturbance, seed propagation, forest management, carbon dynamics and climate change, was applied to simulate dynamic natural succession of forests for coming 300 years in hilly-gully area of Loess Plateau. The results showed that (1) During the advancement of succession, the study area was occupied by different communities and appeared different succession stage successively under the condition of without considering the disturbance; (2) The current artificial forest has changed from 93.31% of Robinia pseudoacacia to exit the forest community in 50 years; (3) Platycladus oriental was the dominant species of coniferous trees and Populus davidiana was the dominant species of deciduous trees; (4)During the late succession stage, Platycladus oriental replaced Pinus tabulaeformis becoming the largest areal proportion of dominant tree species. The simulating of the natural succession in hilly-gully area of Loess Plateau forests at large space and long term scales, could provide a scientific basis for rational allocation of forest resources and forest management. In addition, our work clarifies the challenges and opportunities for the application of the model in the artificial forest and in hilly-gully area of Loess Plateau, China.

  18. Optimizing water and nitrogen inputs for winter wheat cropping system on the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    QiuPing FU; QuanJiu WANG; XinLei SHEN; Jun FAN

    2014-01-01

    Optimal use of water and fertilizers can enhance winter wheat yield and increase the efficiencies of water and fertilizer usage in dryland agricultural systems. In order to optimize water and nitrogen (N) management for winter wheat, we conducted field experiments from 2006 to 2008 at the Changwu Agro-ecological Experimental Station of the Chinese Academy of Sciences on the Loess Plateau, China. Regression models of wheat yield and evapotranspiration (ET) were established in this study to evaluate the water and fertilizer coupling effects and to determine the optimal coupling domain. The results showed that there was a positive effect of water and N fertilizer on crop yield, and optimal irrigation and N inputs can significantly increase the yield of winter wheat. In the drought year (2006-2007), the maximum yield (Ymax) of winter wheat was 9.211 t/hm2 for the treatment with 324 mm irriga-tion and 310 kg/hm2 N input, and the highest water use efficiency (WUE) of 16.335 kg/(hm2⋅mm) was achieved with 198 mm irrigation and 274 kg/hm2 N input. While in the normal year (2007-2008), the maximum winter wheat yield of 10.715 t/hm2 was achieved by applying 318 mm irrigation and 291 kg/hm2 N, and the highest WUE was 18.69 kg/(hm2⋅mm) with 107 mm irrigation and 256 kg/hm2 N input. Crop yield and ET response to irrigation and N inputs followed a quadratic and a line function, respectively. The optimal coupling domain was determined using the elas-ticity index (EI) and its expression in the water-N dimensions, and was represented by an ellipse, such that the global maximum WUE (WUEmax) and Ymax values corresponded to the left and right end points of the long axis, respectively. Considering the aim to get the greatest profit in practice, the optimal coupling domain was represented by the lower half of the ellipse, with the Ymax and WUEmax on the two end points of the long axis. Overall, we found that the total amount of irrigation for winter wheat should not exceed 324 mm. In

  19. Human-Induced Landcover Changes Drive a Diminution of Land Surface Albedo in the Loess Plateau (China)

    OpenAIRE

    Jun Zhai; Ronggao Liu; Jiyuan Liu; Lin Huang; Yuanwei Qin

    2015-01-01

    A large decrease in the land surface albedo of the Loess Plateau was observed from 2000 to 2010, as measured using satellite imagery. In particular, ecological restoration program regions experienced a decrease in peak season land surface albedo exceeding 0.05. In this study, we examined the spatial and temporal patterns of variation during the peak season albedo in the Loess Plateau and analyzed its relationships with changes of anthropogenic and natural factors at the pixel level. Our analy...

  20. A Probe into the Dynamic Change of Land Use in the Southern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Bin; GUO; Li; ZHANG

    2013-01-01

    In order to reveal the characteristics of land use change in the south loess plateau,this paper tentatively divided Loess Plateau into North and South under the support of GIS,and then introduced land use spatial temporal dynamic model,analyzed land use dynamic change in provincial scale. The results showed: during the 25 years,construction land area increased from 3 555. 99 km2 to 4 794. 28 km2,unused land decreased by 0. 02 percentage points,forest land area increased from 51 011. 31 km2 to 51 066. 79 km2,waters increased of 0. 01 percentage points,farmland area decreased to 98 561. 57 km2 from 100 004. 79 km2,grassland area increased by 0.08 percentage points. Land use change important values in province scale on each were not identical,showed obvious regional differences.

  1. Loess Plateau check dams can potentially sequester eroded soil organic carbon

    Science.gov (United States)

    Zhang, Haicheng; Liu, Shuguang; Yuan, Wenping; Dong, Wenjie; Xia, Jiangzhou; Cao, Yaojun; Jia, Yanwei

    2016-06-01

    Check dams are special soil and water conservation structures in the Loess Plateau, China. They play an important role in intercepting sediments and soil organic carbon (SOC). However, the decomposition of intercepted SOC and the environmental regulations at check dams have not been investigated. We conducted several paired field experiments at both check dams and slope lands in the Yanhe Watershed of the Loess Plateau to examine the characteristics of SOC decomposition at check dams. On average, the SOC mineralization rate in slope lands was approximately three times higher than in check dams. Increased soil moisture and compaction in check dams can constrain carbon mineralization by limiting the oxygen availability of SOC and can isolate substrate carbon from heterotrophic microorganisms. Our results indicate that check dams display a considerable potential for eroded SOC sequestration via reducing the soil respiration rate and highlight the important implications of lateral carbon redistribution and human engineering projects when estimating regional or global ecosystem carbon cycles.

  2. Agriculture sustainability in a sensitive environment--a case analysis of Loess Plateau in China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Loess Plateau, an arid and semi-arid region in Northwest China, is well-known for its most serious soil erosion in terms of sediment yield each year. Soil erosion, which is intensified by agricultural activities, is the major factor influencing sustainable agriculture development in this region. It reduces productivity by removing nutrients and especially reducing water availability that is essential for crop production in the area. It also brings about off-site costs by demanding more efforts for maintenance of banks and dams along Yellow River through raising the riverbed with sediment. Climate is capricious and extreme weather conditions occur frequently, which impairs normal agricultural production with erosion and also decrease of water availability. Extensive way of farming still dominates on the Loess Plateau, which cannot produce satisfying economic results and needs to be improved or altered. Conventional agricultural production pattern needs to be reconsidered for husbandry has not been granted its due position. Agriculture is the backbone of economy. Poor agricultural production impedes economic development and vice versa, backward economy also influences the advancement of agriculture. Besides a large population, education status of farmers is another threshold that requires being resolved for a sustainable agriculture.Although conventional agriculture has been practiced there for more than 5000 years, now it cannot meet the demand for food and fiber by the increasing population and some of its farming practices are contributing to environmental degradation directly or indirectly and can sustain no longer. Agriculture on Loess Plateau needs to find its own way of sustainability. To work toward a sustainable agriculture, chances and challenges both indwell on Loess Plateau.

  3. Spatial variations of shallow and deep soil moisture in the semi-arid Loess Plateau, China

    OpenAIRE

    Yang, L; Wei, W.; Chen, L.; Jia, F.; B. Mo

    2012-01-01

    Soil moisture in deep soil layers is an important relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the spatial variations of deep soil moisture with respect to the topographic conditions has significant importance for vegetation restoration. In this study, we focused on analyzing the spatial variations and factors influencing soil moisture content (SMC) in shallow (0–2 m) and deep (2–8 m) soil layers, based on soil moisture observa...

  4. Soil moisture and evapotranspiration of different land cover types in the Loess Plateau, China

    OpenAIRE

    Wang, S.(Institute of Physics, Academia Sinica, Taipei, Taiwan); B. J. Fu; Gao, G. Y.; X. L. Yao; Zhou, J.

    2012-01-01

    We studied the impacts of re-vegetation on soil moisture dynamics and evapotranspiration (ET) of five land cover types in the Loess Plateau in northern China. Soil moisture and temperature variations under grass (Andropogon), subshrub (Artemisia scoparia), shrub (Spiraea pubescens), plantation forest (Robinia pseudoacacia), and crop (Zea mays) vegetation were continuously monitored during the growin...

  5. Evapotranspiration measurement and crop coefficient estimation over a spring wheat Farmland ecosystem in the Loess Plateau.

    Science.gov (United States)

    Yang, Fulin; Zhang, Qiang; Wang, Runyuan; Zhou, Jing

    2014-01-01

    Evapotranspiration (ET) is an important component of the surface energy balance and hydrological cycle. In this study, the eddy covariance technique was used to measure ET of the semi-arid farmland ecosystem in the Loess Plateau during 2010 growing season (April to September). The characteristics and environmental regulations of ET and crop coefficient (Kc) were investigated. The results showed that the diurnal variation of latent heat flux (LE) was similar to single-peak shape for each month, with the largest peak value of LE occurring in August (151.4 W m(-2)). The daily ET rate of the semi-arid farmland in the Loess Plateau also showed clear seasonal variation, with the maximum daily ET rate of 4.69 mm day(-1). Cumulative ET during 2010 growing season was 252.4 mm, and lower than precipitation. Radiation was the main driver of farmland ET in the Loess Plateau, which explained 88% of the variances in daily ET (p<0.001). The farmland Kc values showed the obvious seasonal fluctuation, with the average of 0.46. The correlation analysis between daily Kc and its major environmental factors indicated that wind speed (Ws), relative humidity (RH), soil water content (SWC), and atmospheric vapor pressure deficit (VPD) were the major environmental regulations of daily Kc. The regression analysis results showed that Kc exponentially decreased with Ws increase, an exponentially increased with RH, SWC increase, and a linearly decreased with VPD increase. An experiential Kc model for the semi-arid farmland in the Loess Plateau, driven by Ws, RH, SWC and VPD, was developed, showing a good consistency between the simulated and the measured Kc values.

  6. Analysis of Sediment Source of Watershed in Western Shanxi of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    LIUHuifang; WEITianxing; ZHUQingke

    2004-01-01

    The paper analyzes the sediment source of watershed by means of studying watershed in westem Shanxi of the Losses Plateau. On the basis of watersheds classification, 7 typical watersheds were chosen and observed for 11 years. The result shows that the sediment at the small watershed mainly comes from gullies, which is 60% of the total sediment. Erosion modulus of valley (including gully head, gully bed, valley side) is 1.28-2.48 times as that of the area between channels(including hill slope and mound of the Loess Plateau). The main sediment source of slope erosion is cultivated land on slope without water and soil conservation measures.

  7. Soil Microbial Community Composition During Natural Recovery in the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    XIAO Lie; LIU Guo-bin; XUE Sha; ZHANG Chao

    2013-01-01

    This study aimed to determine the characteristics of soil microbial community composition and its relationship with soil chemical properties during natural recovery in the Loess Plateau. The soil microbial community composition was analyzed by comparing the soil microbial phospholipid fatty acids (PLFAs) of eight croplands abandoned for 1, 3, 5, 10, 13, 15, 20, and 30 yr in the Dunshan watershed, northern Loess Plateau, China. The results showed that soil organic carbon, total nitrogen, soil microbial biomass carbon, and soil microbial biomass nitrogen signiifcantly increased with the abandonment duration, whereas the metabolic quotient signiifcantly decreased. The Shannon richness and Shannon evenness of PLFAs signiifcantly increased after 10 yr of abandonment. Gram-negative, Gram-positive, bacterial, fungal, and total PLFAs linearly increased with increased abandonment duration. Redundancy analysis showed that the abandonment duration was the most important environmental factor in determining the PLFA microbial community composition. The soil microbial PLFAs changed from anteiso-to iso-, unsaturated to saturated, and short-to long-chain during natural recovery. Therefore, in the Loess Plateau, cropland abandonment for natural recovery resulted in the increase of the soil microbial PLFA biomass and microbial PLFA species and changed the microbial from chemolithotrophic to a more heterotrophic community.

  8. Decay characteristics and erosion-related transport of glyphosate in Chinese loess soil under field conditions

    NARCIS (Netherlands)

    Yang, X.; Wang, Fei; Martins Bento, Celia; Meng, L.; Dam, van R.C.J.; Mol, J.G.J.; Liu, Guobin; Ritsema, C.J.; Geissen, V.

    2015-01-01

    The decay characteristics and erosion-related transport of glyphosate and aminomethylphosphonic acid (AMPA) were monitored for 35 d at different slope gradients and rates of application in plots with loess soil on the Loess Plateau, China. The initial glyphosate decayed rapidly (half-life of 3.5 d)

  9. The impacts of urbanization on soil erosion in the Loess Plateau region

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The accelerated urbanization has resulted in new soil erosion inthe Loess Plateau region since the 1980s. A concept of urban erosion and its impacts on environment are discussed. The experimental studies and field investigations show that those loose silt and earth piles formed by urban construction can be eroded seriously: Under stormy rain, the amount of sediment from steep man-dumped slope is 10.8-12.2 times that of from uncovered slope land; the result of experiments with the wind tunnel also shows that the damage to the surface structure of dry loess can cause serious soil erosion by wind in some cities of the region. Even if in the urban built-up area, there are many loose sandy soil, mud and silt, which are washed into rivers by city's ground flow in the rainy season.So, anthropogenically induced soil erosion has made soil erosion more serious around the urban areas.And the urban eroded environment has several characteristics such as fragility, complexity,seasonality and quick variability. Urban areas witness a quick economic growth and have more construction projects than rural areas, which brings more intensive changes of environments during a short period of time or adds some new elements to the erosion system. Therefore erosion has experienced more intensive impact by human activities. So, the possible impact of urbanization on erosion environment must be taken into consideration when designing or planning to exploit natural rsources or to develop urban areas in the Loess Plateau.

  10. Spatial analysis of Budovar stream catchment (Srem Loess Plateau, Serbia) in a tectonically active region

    Science.gov (United States)

    Jovanovic, Mladjen; Rvovic, Ivan; Sorak, Rada; Petrovic, Milos

    2016-04-01

    Budovar is the far longest stream on Srem Loess Plateau, with a length of a 52 km, and catchment area of 245 km2. Budovar stream drains a quite complex landscape in terms of generally flat loess plateau, with elevations decreasing gradually southeastward - from 213 m at slopes of Fru\\vska Gora Mountain to 70,9 m at the confluence with Danube river. The youngest (Pleistocene/Holocene) sedimentary formations in the catchment vary from slope loess on Fru\\vska Gora Mtn. in upper part, through typical plateau loess in middle part, and the finest bog-sediments in tectonic depressions in lower part. These deposits lie over the bog-lake-terrestrial sediments with thickness over 100 m. According the geodetic measurements, uplift of Fru\\vska Gora Mtn., which has been the strongest during the Middle Pleistocene, is still present, with rates of up to 1 mm/y in contrast of general uplift of the area, subsidence is recorded in two distinct parts of the catchment. Spatial analysis is done using a DEM, generated in ArcGIS 10.0 from the elevation points, 10 m contours and stream coverage available in 1:25.000 topographical maps. Both longitudinal and cross-section profiles of the valley reflect the influence of tectonic distortions and climatic fluctuations. Valleys in Budovar catchment have composite character - the valleys cross-sections vary from deep incised V-shape, reversed trapezoid shape and completely flat valleys in tectonic depressions. Moreover, there is almost no correlation between the shape of cross-sectional profiles and the direction of curvature of the main valley's long axis (left/right or straight), suggesting that the tectonic activity has the key role in shaping. The width of valleys in Budovar catchment area is in sharp contrast with present stream discharge, which suggests strong climate fluctuations since Upper Pleistocene. The longitudinal profiles also shows signs of kickpoints and some short reaches with increasing elevation in the flow direction. Key

  11. 典型黄土区油松树干液流变化特征分析%Analysis of Sap Flow Characteristics of the Chinese Pine in Typical Loess Plateau Region of China

    Institute of Scientific and Technical Information of China (English)

    张涵丹; 卫伟; 陈利顶; 于洋; 杨磊; 贾福岩

    2015-01-01

    蒸腾耗水是植被水分利用的重要方式和重要过程之一,对植物养分输送﹑生长发育﹑应对和缓解干旱胁迫以及改善区域微气候等都具有重要意义.研究以半干旱黄土区的油松植被为例,基于四针式热扩散探针法监测树干液流的动态变化,探讨其蒸腾耗水规律,分析油松树种的水分利用方式及对生存环境的适应能力.结果表明,油松的液流速率具有明显的季节性差异,不同月份的液流速率以4月最低,其次为10月﹑9月和8月,分别为0.024﹑0.057﹑0.062和0.071 mL•( cm2•min)-1.液流速率的日变化在各个时期都呈现昼高夜低趋势,夜间液流速率较低,但不为零.在降雨事件影响下,夜间液流量在日液流总量中的比重明显增加,是晴朗天气的3.9倍,而白天液流量所占比重下降31.8%.寒潮期间液流速率表现出相似的变化趋势,对突变环境具有较强的适应能力.油松液流速率与气象因子显著相关,对液流速率影响的大小顺序为:太阳辐射﹥水汽压亏缺﹥相对湿度﹥大气温度.%Transpiration is one of the major processes of water consumption. It is significant for nutrients transportation, plant development, drought stress alleviation and micro-climate amelioration. In this study, the artificially planted Chinese pine ( Pinus tabuliformis) was selected as an example to explore its transpiration characteristics, water-use strategies and the adaptability of the living environment in a typical loess hilly area of China. The results showed that:the sap flow rates of Chinese pine varied obviously in different seasons. The minimum sap flow rate occurred in April, followed by October, September and August, which was 0. 024, 0. 057, 0. 062 and 0. 071 mL•(cm2•min) -1, respectively. The rule of the diurnal variation of sap flow rate was regular, higher in daytime than at night. The flow rate was low during nighttime, but not zero

  12. An applied research on remote sensing classification in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Due to complex terrain of the Loess Plateau, the classification accuracy is unsatisfactory when a single supervised classification is used in the remote sensing investigation of the sloping field. Taking the loess hill and gully area of northern Shaanxi Province as a test area, a research was conducted to extract sloping field and other land use categories by applying an integrated classification. Based on an integration of supervised classification and unsupervised classification, sampling method is remarkably improved. The results show that the classification accuracy is satisfactory by the method and is of critical significance in obtaining up-to-date information of the sloping field, which should be helpful in the state key project of converting fiumland to forest and grassland on slope land in this area. This research sought to improve the appfication accuracy of image classification in complex terrain areas.

  13. PREDICTION OF SEDIMENT REDUCING BENEFIT UNDER DIFFERENT RAINFALL CONDITIONS AND CONTROL DEGREES ON THE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    JIAO Ju-ying; WANG Wan-zhong

    2003-01-01

    Based on the distribution of hydrological stations and zoning of types of soil erosion, the Loess Plateau(310 × 103km2) is divided into 292 erosion units. And taking the erosion modulus > 5000t/km2 as a criterion, the empha-sis control area (149 × 103km2) of the Loess Plateau is demarked, and is divided into 10 control regions. The control-lable area and the location of control measures are conformed. Level terraces are mainly collocated on the 3°- 15°slopes, woodland and grassland are collocated on the > 15° slopes, and the proportion of woodland to grassland is 8:2 inthe forest belt, 5:5 in the forest steppe belt, and 2:8 in the steppe belt. The 9000 combinations of soil-water conserva-tion measures in different rainfall conditions are obtained by the permutation and combination method, according to the 9rainfall frequencies and the controllable areas of level terrace, woodland and grassland at 10% of control progress rate.The quality standards of level terrace, woodland and grassland are ascertained. The evaluation indexes of soil-water conserva-tion benefits of level terrace, woodland and grassland are established respectively in the condition that rainfall index ishigher than that of erosive index of sloping field. Based on the results above, the sediment reducing benefit and soil ero-sion modulus in the different rainfall conditions and control degrees are analyzed, which could provide a decision-makingbasis for soil-water loss control on the Loess Plateau.

  14. Changes in Ecosystem Service Values on the Loess Plateau in Northern Shaanxi Province, China

    Institute of Scientific and Technical Information of China (English)

    LI Jing; REN Zhi-yuan

    2008-01-01

    The Loess Plateau in northern Shaanxi Province of China covers Yulin, Yan'an, and Tongchuan cities mainly. The kind of physiognomy is complicated and various, including the transitional region of the sand and wind, the hilly-gully fragile region, the pimple mound region from North to South. Large-scale land reclamation projects that are severely affecting these ecosystems have been implemented. In this paper, we reported an investigation to the changes in land use and ecosystem services on the Loess Plateau in northern Shaanxi Province from 1978 to 2000. We used three LANDSAT TM and/or ETM data sets to estimate the changes in the size of five land-cover/land-use categories, and we also used previously published value coefficients to estimate the changes in the value of ecosystem services delivered by each land category. Finally, we ranked the contribution of various ecosystem functions to the overall value of the ecosystem services, we have estimated that the annual value of the ecosystem services is 56.95 billon RMB yuan in the Loess Plateau in northern Shaanxi Province in 2000. In the region, from 1978 to 2000, the economic value of the fixing carbon was higher,the economic value of water conservation was the lowest, but the economic value of the NPP, fixing carbon, and supplying oxygen accounted for above ninety percent of the total value, obviously the vegetation created the biggest ecosystem service value. We can conclude that future land-use policy formulation should give precedence to the conservation of these ecosystems over uncontrolled reclamation, and that further land reclamation should be based on rigorous environmental impact analyses.

  15. Correlating check dam sedimentation and rainstorm characteristics on the Loess Plateau, China

    Science.gov (United States)

    Li, Xungui; Wei, Xia; Wei, Ning

    2016-07-01

    On the Loess Plateau, China, check dams are necessary for soil and water conservation. In this study, the relationships between check dam sedimentation and storm characteristics were investigated, and rainstorm events for an area of data scarcity were reconstructed using optimal regression models. Four typical check dams of the Loess Plateau (the Shipanmao, Hualiang, No. 3 Guandigou, and No. 4 Guandigou dams) were selected for case studies. Soil profiles behind the four dams were divided into 21, 25, 31, and 31 layers, respectively. The one-to-one link between sediment layers and corresponding storm characteristics were considered based on the peak fallout of 137Cs and on the principle that higher flow corresponds to higher sediment deposition volume. Analysis showed that the layered sediment volume (V) was closely related to rainfall erosivity (R), and to the maximum rainfall intensity over 30 min (I30). A statistically significant power regression model between V and R was observed, along with an exponential regression model between V and I30. Based on the power regression model between V and R, a new approach was developed in order to reconstruct rainfall erosivity in rainfall data-scarcity areas. Different hysteresis patterns (counterclockwise, clockwise, and hybrid) at the single storm scale were observed between V and R for the Shipanmao dam deposition wedge (depositional area behind a dam), and these impacted differently on the scale reconstruction results. However, the distance between the reconstructed dams and the known dams had an even stronger influence. The scale method developed in this study was shown to perform well and was able to reconstruct rainstorm events for adjacent regions with similar climatic and geomorphological conditions. Furthermore, the results of this study have improved our understanding of single rainstorm dynamics and soil erosion mechanisms on the Loess Plateau.

  16. Spatial and temporal changes of summer monsoon on the Loess Plateau of Central China during the last 130 ka inferred from Rb/Sr ratios

    Institute of Scientific and Technical Information of China (English)

    陈旸; 陈骏; 刘连文; 季峻峰; 张建新

    2003-01-01

    The Rb/Sr ratios for samples from six loess-paleosol sections on the Chinese Loess Plateau during the last glacial-interglacial cycle, and for samplesfrom 18 modern surface soils, have been analyzed. The six sections are along north-south and west-east transects respectively. The results show that the spatial distribution of Rb/Sr is characterized by a remarkable increase from north to south while Rb/Sr ratio changes little from west to east, whose latitude indicates shift of summer monsoon intensity. A regression equation between Rb/Sr ratiosand mean annual precipitation(MAP) has been constructed through statistical analysis for the modern surface soils. Paleorainfall during the last 130 ka is estimated for the six sections based on the regression equation. It is evident thatprecipitation increased remarkably during marine isotope stages 3 and 5, exhibiting the high and similar gradients of variation with latitude. This demonstrates that the environmental effect is more prominent in the south of the Loess Plateau than in the north during the dominance of summer monsoon.

  17. Magnetic Field Gradient Differentiation of Pedogenic Iron Oxide Minerals From Chinese Loess and Paleosols

    Science.gov (United States)

    Wagoner, L.; Roth, A.; Singer, M. J.; Verosub, K.

    2003-12-01

    The correlation between paleosols and enhanced magnetic susceptibility on the Chinese Loess Plateau is by now well established. However, scant effort has focussed on the interpretation of paleoclimate via the specific iron oxide mineral assemblages contributing to the enhanced magnetic susceptibility signal. This paper focuses on the separation and identification of the pedogenic (minerals from selected loess and paleosol layers of the Loess Plateau. Heretofore, it has been difficult if not impossible to isolate mixed iron oxide mineral phases due to their very similar physical and magnetic properties. Chinese loess and paleosol samples were chosen to illustrate the utility of the technique to natural soil systems. In the following method, initial size separation of mineral particles at 0.5 micron or less by gravity and centrifugation reduces the problem of overlapping magnetic susceptibilities due to mixed grain sizes. The submicron mineral fraction is then subjected to a series of high field gradient (HFG) magnetic separations utilizing a new design. Although HFG magnetic separation methods have been used before, the new design is able to differentiate submicron iron oxide mineral phases from bulk earth material. The design includes a Franz Isodynamic Separator fitted with a custom-made flow cell. A recirculating liquid is used to suspend the mineral particles between the poles of the electromagnet. By varying the strength of the field gradient, recirculation time, and flow velocity, step-wise separation of ferrimagnetic from antiferromagnetic minerals is possible. Because of the tendency for particles to aggregate during recirculation, some mixing of the oxide mineralogy has been unavoidable. Although theoretical arguments favor a narrow grain size distribution (about 50-100 nm) for stable single domain magnetite, in soil environments, and particularly for nanoscale materials, discrete particles are the exception rather than the rule. Therefore it is likely that

  18. Assessing the hydrological effect of the check dams in the Loess Plateau, China by model simulations

    Directory of Open Access Journals (Sweden)

    Y. D. Xu

    2012-12-01

    Full Text Available Check dams are commonly used for soil conservation. In the Loess Plateau of China, check dams have been widely constructed as the principal means to retain floodwater and intercept soil sediments since the 1970s. However, little research has been done to quantify the hydrological effects of the check dams.

    In this research, the SWAT model (Soil and Water Assessment Tool was applied to simulate the runoff and sediment in the Yanhe watershed in the Loess Plateau. We treated the 1950s to 1960s as "reference period" since there were very few check dams during the period. The model was first calibrated and validated in the "reference period". The calibrated model was then used in the later periods to simulate the hydrological effects of the check dams.

    The results showed that the check dams had a regulation effect on runoff and a retention effect on sediment. From 1984 to 1987, the runoff in rainy season (from May to October decreased by 14.7 to 25.9% due to the check dams, while in dry season (from November to the following April, runoff increased by 60.5 to 101.2%; the sediment in rainy season decreased by 34.6 to 48.0%. From 2006 to 2008, the runoff in rainy season decreased by 15.5 to 28.9%, and the runoff in dry season increased by 20.1 to 46.4%; the sediment in rainy season decreased by 79.4 to 85.5%.

    Construction of the large number of in the Loess Plateau has enhanced the region's capacity to control the runoff and sediment. In the Yanhe watershed, the annual runoff was reduced by less than 14.3% due to the check dams; and the sediment in rainy season was blocked by up to 85.5%. Thus, check dams are effective measures for soil erosion control in the Loess Plateau.

  19. Measurement Principles of TRIME-TDR System and its Application in Caijiachuan Watershed, the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    LIXiaoyin; BIHuaxing; ZHANGJianjun

    2004-01-01

    Time domain reflectometry (TDR) is a highly accurate and automatic method for determination of porous media water content and electrical conductivity. This paper focuses on the basic principle of TDR technology and its application in Caijiachuan watershed, the Loess Plateau, China, the composition and structure of a set of TDR-TRIME. The installation, measurement and calibration of TRIME-TDR in the Loess Plateau has been introduced. The factors that can influence the veracity of the measurement by TDR have also been analyzed in the article.

  20. Study on the Climate Changes Characteristics in the Hilly Region of the Loess Plateau and Its Influence on Agricultural Production

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The aim was to study the climate changes characteristics in the hilly region of the loess plateau and its influence on agricultural production.[Method] Taking Yan'an City as an example,and by dint of temperature and precipitation in nine meteorological stations from 1957 to 2007 and accumulated anomaly curve,linear regression and relevant analysis,the climate changes characteristics in 51 years in Yan'an were expounded.The climate changes in the hilly region of the loess plateau were studied and...

  1. Soil Insect Diversity and Abundance Following Different Fertilizer Treatments on the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    LIN Ying-hua; LU Ping; YANG Xue-yun; ZHANG Fu-dao

    2013-01-01

    The presence of abundant and diverse communities of macro-arthropods is considered an indicator of sustainability in agroecosystems. This study was designed to investigate the effects of different fertilizer treatments on abundance and diversity of insects of arable loess soil on the Loess Plateau of China. These regimes included a control with no fertilizer addition or manure, treatments with application of mineral fertilizers (N, NK, NP, PK, NPK), treatments with NPK in combination with organic materials such as wheat straw or maize stalk, treatments with two rates of organic manure application;and different crop rotations (Rot.1:winter wheat summer maize;Rot.2:winter wheat summer maize soybean intercropping;and Rot.3:winter wheat or rapeseed summer maize soybean intercropping). Soil macro-arthropods were collected from the plough layer (0-20 cm) and sorted by hand after each harvest in June and October 2001 and 2002. A total of 3 132 individuals were collected, from 7 orders and 55 families, dominated by Formicidae (61.72%) and Staphylinidae (14.24%). The results showed that individuals and groups were significantly influenced by sampling dates, while groups were significantly influenced by the fertilization treatments. Soil insect biodiversity, as determined by the Shannon index, was significantly influenced by fertilization and sampling dates. The abundance of soil insects was positively and significantly correlated with soil moisture content in October 2002. Nitrogen, phosphorus and potassium fertilizers and incorporation of organic materials were favorable factors for abundance and diversity in arable loess soil.

  2. Demonstration Research into Eco-environment Rehabilitation on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Xu Mingxiang; Liu Guobin

    2002-01-01

    @@ As part of the "Action Plan for the Development of Western China," the project is conducted by the Institute of Soil & Water Conservation under CAS and the Ministry of Water Resources. It focuses on the rehabilitation of the regional eco-environment, such as a large-scale afforestation drive on enclosed hillsides, efforts to turn the reclaimed farmland on steep mountain slopes into woodland and pastureland, the greening of mountainous areas and speeding up the restoration tempo of the original vegetation on the Loess Plateau. An experiment & demonstration zone has been co-established by the CAS Institute and the provincial Government of Shaanxi. Located in a hillygully region sprawling in the heartland of the Plateau,the zone includes nine townships, covering 707 square kilometers in total area. Since its start in 2000, the project has scored remarkable progress:

  3. CARBON-OXYGEN ISOTOPE RECORDS OF PEDOGENIC CARBONATE FROM THE EARLY MIOCENE-PLEISTOCENE LOESS-RED CLAY IN THE VICINITY OF THE LIUPANSHAN REGION AND ITS IMPLICATIONS FOR THE EARLY ORIGIN OF C4 PLANTS IN THE CHINESE LOESS PLATEAU%中新世以来六盘山邻区黄土-红粘土成土碳酸盐碳氧同位素记录及其对C4植物早期扩张的指示

    Institute of Scientific and Technical Information of China (English)

    张瑜; 熊尚发; 丁仲礼; 卢海建; 姜文英

    2011-01-01

    sites in the world have revealed that the timing of C4 plants origin and expansion was not globally synchronous, and different proxy records documented different timing features of C4 expansion. The history of C4 plants in Asia is an important component in reconstructing the globally geographical patterns of C4 expansion. Records from South Asia indicate C4 plants expanded abruptly during ca. 8 ~4Ma,and several localities in the Chinese Loess Plateau document a δ13C peak at ca. 6Ma,3Ma and from 1 Ma,respectively. Previous studies have demonstrated that during ca. 7 ~ 4Ma,soil carbonate records ( δ13Csc) in the Chinese Loess Plateau display a southern-ward negative trend, indicative of a southern-ward expansion of C4 plants during the Late Miocene and the Early Pliocene. It is remained unclear, however, that if the C4 plants expansion over the Chinese Loess Plateau occurred earlier than during the Late Miocene.Here we report a study based on δ13Csc of loess-red clay sequence from the Baishui and Zhuanglang sections near the Liupanshan region,and the result shows that C4 plants expansion may have initiated as early as at ca. 20Ma with C4 component up to 15% -40% during the Miocene. The Baishui section(35°24'10"N,106°54'43"E) is located in the southeastern part of the Liupanshan region,Central Loess Plateau. This section contains an upper 214m loess-paleosol sequence and a lower 82m red clay deposit. The Zhuanglang section ( 35°13'34"N, 106°4'11"E) lies at the southwestern part of the Liupanshan region,ca.80km to the Baishui section,and consists of 183. 4m red clay deposit. A total 2729 paleomagnetic samples (1026 samples for the Baishui section, 1703 for the Zhuanglang section) were analyzed by using thermal demagnetization at the Laboratory of Piaeomagnetism of the Institute of Geology and Geophysics, Chinese Academy of Sciences and at Lanzhou University. The specimens that exhibit stable component two vectors (91% for the Baishui section and 83.5% for the

  4. Quantitative analysis of soil pores under natural vegetation successions on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Soil pore is a key attribute of the soil structure that affects soil reservoir under natural vegetation recovery on the Loess Plateau.This study is to quantitatively analyze soil pore parameters,measured with Computed Tomography(CT) at 15-57 mm depths under five different vegetation succession stages using a concept of substituting "space" for "time" in the Ziwuling Forest Region of the Loess Plateau.The results showed that the soil pore parameters,such as pore number,porosity,circularity,and fractal dimension,increased significantly under the natural vegetation successions and varied with the pattern climax community stage>pioneering arbor community stage>scrub community stage>herbaceous community stage>abandoned farmland stage,indicating that natural vegetation recovery could remarkably improve soil pore characteristics.With the vegetation succession,this positive effect will be strengthened gradually,which means that the soil pore parameters may appear to be best at the climax community stage.Soil organic matter content increased linearly with the soil pore parameters(P<0.001).Increased organic matter accumulation was one of the major reasons for the changes in soil pore characteristics in natural vegetation succession.

  5. Effects of different vegetation restoration models on soil microbial biomass in eroded hilly Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    XUE Sha; LIU Guobin; DAI Quanhou; LAN Xue; YU Na

    2007-01-01

    Vegetation restoration is a key measure to improve the eco-environment in Loess Plateau,China.In order to find the effect of soil microbial biomass under different vegetation restoration models in this region,six trial sites located in Zhifanggou watershed were selected in this study.Results showed that soil microbial biomass,microbial respiration and physical and chemical properties increased apparently.After 30 years of vegetation restoration,soil microbial biomass C,N,P(SMBC,SMBN,SMBP)and microbial respiration,increased by 109.01%-144.22%,34.17%-117.09%,31.79%-79.94% and 26.78%-87.59% respectively,as compared with the farmland.However,metabolic quotient declined dramatically by 57.45%-77.49%.Effects of different models of vegetation restoration are different on improving the properties of soil.In general,mixed stands of Pinus tabulaeformisAmorpha fruticosa and Robinia pseudoacacia-A,fruticosa had the most remarkable effect,followed by R.pseudoacacia and Caragana korshinkii,fallow land and P.tabulaeformis was the lowest.Restoration of mixed forest had greater effective than pure forest in eroded Hilly Loess Plateau.The significant relationships were observed among SMBC,SMBP,microbial respiration,and physical and chemical properties of soil.It was concluded that microbial biomass can be used as indicators of soil quality.

  6. Review and proposals on vegetation restoration in the Loess Plateau, Northwest China

    Institute of Scientific and Technical Information of China (English)

    Wenhui ZHANG; Guobin LIU

    2008-01-01

    A group of scientists conducted a comprehen-sive investigation on ecological safety and water and soil erosion in the Northwest Loess Plateau, Northwest China. The data gathered was analyzed in terms of achievement, existing problems, and strategy and mea-sures on vegetation restoration in the area. Since the policies of conversion from cropland to forest (CCF) and forbid grazing and cutting (FGC) were carried out, vegetation quality and coverage rate increased quickly in the Loess Plateau area, strengthening the concept of eco-environment protection. Environment harness measure-ments were optimized. The multiform investments on eco-environment and urbanization development in China will benefit vegetation restoration. However, there have been some persisting problems, such as the shortage of investment, instability of government policy, expectation of extravagant economic benefit, larger rate of planta-tion, and scarce technologies supporting vegetation restoration. Many key theories and practice problems require an urgent resolution. In the future, short-, mid-,and long-term goals for vegetation restoration should be clear, achievement should be expanded, and the natural restoration area should be increased. The benefit for the contractor on vegetation restoration should be ensured. Investment on vegetation building research work should be increased.

  7. Evapotranspiration Trend and Its Relationship with Precipitation over the Loess Plateau during the Last Three Decades

    Directory of Open Access Journals (Sweden)

    Zesu Yang

    2016-01-01

    Full Text Available There have been few studies conducted on the changes in actual ET over the Loess Plateau, due to the lack of reliable ET data. Based on ET data simulated by the Community Land Model, the present study analyzed the changes in ET over the Loess Plateau. The results showed the domain-average ET to have decreased in the past 31 years, at a rate of 0.78 mm year−1. ET fluctuated much more strongly in the 1990s than in the 1980s and 2000s, and, apart from in autumn, ET decreased in all seasons. In particular, ET in summer comprised about half of the annual ET trend and had the sharpest trend, dominating the interannual decline. ET also decreased more sharply in the semiarid than semihumid regions. The declining trend of ET was attributed to declining precipitation and air humidity. Locally, the ET trend was closely related to local mean annual precipitation: in areas with precipitation less than 400 mm, ET showed a decreasing trend; in areas with precipitation larger than 600 mm, ET showed an increasing trend; and in areas with precipitation in the range of 400–600 mm could be classified as a transitional zone.

  8. Development stage threshold of watershed landforms in Loess Plateau and separation of erosion mechanism

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Threshold is a limit and marginal point when a qualitative change takes place. Since threshold principle was firstly used in landform research by S.A.Schumm in the 1970s, the quantitative research on watershed landform development stage has come true. Davis proposed a three-stage model on landform evolution: young, mature and old stages. Thereafter Strahler quantified this model by hypsometric analysis method. The authors thought that the material movement stage cannot be expressed by hypsometric method in watershed landform at development stage, because of the uncertainty on stage delimitation. To meet this shortcoming, this paper presents an integral erosion value method. A clear delimitation on landform development stage in the Loess Plateau region has been tested by this method. The result shows that gullied loessial hilly area is at the mature stage, and gullied loessial tableland area is at the young stage. It is estimated that from the point of erosion related sediment yield, natural erosion accounts for 70% of the total erosion amount, and artificial accelerating erosion is 30%. Therefore soil and water conservation is very crucial for the Loess Plateau.

  9. Turbulence intensity and turbulent kinetic energy parameters over a heterogeneous terrain of Loess Plateau

    Science.gov (United States)

    Yue, Ping; Zhang, Qiang; Wang, Runyuan; Li, Yaohui; Wang, Sheng

    2015-09-01

    A deep understanding of turbulence structure is important for investigating the characteristics of the atmospheric boundary layer, especially over heterogeneous terrain. In the present study, turbulence intensity and turbulent kinetic energy (TKE) parameters are analyzed for different conditions with respect to stability, wind direction and wind speed over a valley region of the Loess Plateau of China during December 2003 and January 2004. The purpose of the study is to examine whether the observed turbulence intensity and TKE parameters satisfy Monin-Obukhov similarity theory (MOST), and analyze the wind shear effect on, and thermal buoyancy function of, the TKE, despite the terrain heterogeneity. The results demonstrate that the normalized intensity of turbulence follows MOST for all stability in the horizontal and vertical directions, as well as the normalized TKE in the horizontal direction. The shear effect of the wind speed in the Loess Plateau region is strong in winter and could enhance turbulence for all stability conditions. During daytime, the buoyancy and shear effect together constitute the generation of TKE under unstable conditions. At night, the contribution of buoyancy to TKE is relatively small, and mechanical shearing is the main production form of turbulence.

  10. The WEPP Model Application in a Small Watershed in the Loess Plateau.

    Directory of Open Access Journals (Sweden)

    Fengpeng Han

    Full Text Available In the Loess Plateau, soil erosion has not only caused serious ecological and environmental problems but has also impacted downstream areas. Therefore, a model is needed to guide the comprehensive control of soil erosion. In this study, we introduced the WEPP model to simulate soil erosion both at the slope and watershed scales. Our analyses showed that: the simulated values at the slope scale were very close to the measured. However, both the runoff and soil erosion simulated values at the watershed scale were higher than the measured. At the slope scale, under different coverage, the simulated erosion was slightly higher than the measured. When the coverage is 40%, the simulated results of both runoff and erosion are the best. At the watershed scale, the actual annual runoff of the Liudaogou watershed is 83 m(3; sediment content is 0.097 t/m(3, annual erosion sediment 8.057 t and erosion intensity 0.288 t ha(-1 yr(-1. Both the simulated values of soil erosion and runoff are higher than the measured, especially the runoff. But the simulated erosion trend is relatively accurate after the farmland is returned to grassland. We concluded that the WEPP model can be used to establish a reasonable vegetation restoration model and guide the vegetation restoration of the Loess Plateau.

  11. The WEPP Model Application in a Small Watershed in the Loess Plateau.

    Science.gov (United States)

    Han, Fengpeng; Ren, Lulu; Zhang, Xingchang; Li, Zhanbin

    2016-01-01

    In the Loess Plateau, soil erosion has not only caused serious ecological and environmental problems but has also impacted downstream areas. Therefore, a model is needed to guide the comprehensive control of soil erosion. In this study, we introduced the WEPP model to simulate soil erosion both at the slope and watershed scales. Our analyses showed that: the simulated values at the slope scale were very close to the measured. However, both the runoff and soil erosion simulated values at the watershed scale were higher than the measured. At the slope scale, under different coverage, the simulated erosion was slightly higher than the measured. When the coverage is 40%, the simulated results of both runoff and erosion are the best. At the watershed scale, the actual annual runoff of the Liudaogou watershed is 83 m(3); sediment content is 0.097 t/m(3), annual erosion sediment 8.057 t and erosion intensity 0.288 t ha(-1) yr(-1). Both the simulated values of soil erosion and runoff are higher than the measured, especially the runoff. But the simulated erosion trend is relatively accurate after the farmland is returned to grassland. We concluded that the WEPP model can be used to establish a reasonable vegetation restoration model and guide the vegetation restoration of the Loess Plateau.

  12. Soil water depletion depth by planted vegetation on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    WANG ZhiQiang; LIU BaoYuan; LIU Gang; ZHANG YongXuan

    2009-01-01

    Evapotranspiration of much planted vegetation exceeds precipitation,and this can deplete soil water and cause a deep dry layer in the soil profile,which is a serious obstacle to sustainable land use on the Loess Plateau,China.This study aimed to determine water depletion depth of planted grassland,shrub,and forest in a semiarid area on the Loess Plateau.Soil moisture of five vegetation types was measured to >20 m in depth.The vegetation types were crop,natural grasse,seven-year-old planted alfalfa (Medicago sativa L.),23-year-old planted caragana (Caragana microphylla Lam.) shrub,and 23-year-old planted pine (Pinus tabulaeformis L) forest land.Through comparing moisture of planted alfalfa grass,caragana shrub,and pine forest to crop and natural grassland,the depth and amount of soil water consumed by grassland,caragana brush and pine forest was determined.The depth of soil water de-pleted by alfalfa,caragana brush,and pine forest reached 15.5,22.4 and 21.5 m,respectively.

  13. Soil water depletion depth by planted vegetation on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Evapotranspiration of much planted vegetation exceeds precipitation, and this can deplete soil water and cause a deep dry layer in the soil profile, which is a serious obstacle to sustainable land use on the Loess Plateau, China. This study aimed to determine water depletion depth of planted grassland, shrub, and forest in a semiarid area on the Loess Plateau. Soil moisture of five vegetation types was measured to >20 m in depth. The vegetation types were crop, natural grasse, seven-year-old planted alfalfa (Medicago sativa L.), 23-year-old planted caragana (Caragana microphylla Lam.) shrub, and 23-year-old planted pine (Pinus tabulaeformis L) forest land. Through comparing moisture of planted alfalfa grass, caragana shrub, and pine forest to crop and natural grassland, the depth and amount of soil water consumed by grassland, caragana brush and pine forest was determined. The depth of soil water depleted by alfalfa, caragana brush, and pine forest reached 15.5, 22.4 and 21.5 m, respectively.

  14. Application of SCS Model in Estimation of Runoff from Small Watershed in Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    LIU Xianzhao; LI Jiazhu

    2008-01-01

    Soil Conservation Service (SCS) model,developed by U.S.Soil Conservation Service in 1972,has been widely applied in the estimation of runoff from an small watershed.In this paper,based on the remote sensing geo-information data of land use and soil classification all obtained from Landsat images in 1996 and 1997 and conventional data of hydrology and meteorology,the SCS model was investigated for simulating the surface runoff for single rainstorm in Wangdonggou watershed,a typical small watershed in the Loess Plateau,located in Changwu County of Shaanxi Province of China.Wangdonggou watershed was compartmentalized into 28 sub-units according to natural draining division,and the table of curve number (CN) values fitting for Wangdonggou watershed was also presented.During the flood period from 1996 to 1997,the hydrograph of calculated runoff process using the SCS model and the hydrograph of observed runoff process coincided very well in height as well as shape,and the model was of high precision above 75%.It is indicated that the SCS model is legitimate and can be successfully used to simulate the runoff generation and the runoff process of typical small watershed based on the remote sensing geo-information in the Loess Plateau.

  15. Quantitative Study on the Relationship between Arable Land and Its Influencing Factors in Southern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Bin; GUO; Lin; PEI

    2015-01-01

    With the Southern Loess Plateau as the object of study,we select the nonbiological factors( physical factors),biological factors and human factors that affect the landscape of arable land to build indicator system. Using GIS,we perform the visualization expression and hierarchical storage of influencing factors to build 1 km × 1 km integrated vector and raster database of arable land landscape pattern and its influencing factors. Using spatial regression analysis,we determine the quantitative relationship between arable land landscape and its influencing factors. The results show that the arable land in the Southern Loess Plateau is mainly distributed in the regions with high temperature,great average annual precipitation,high altitude,high soil N content,small slope,GDP per unit area of land,low ≥10℃ accumulated temperature,and short distance away from the rivers and roads. The study provides a scientific basis for clarifying the relationship between arable land landscape and its influencing factors.

  16. An Overview of the Semi-arid Climate and Environment Research Observatory over the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    HUANG Jianping; ZHANG Seidou; WANG Guoyin; FENG Guanghong; YUAN Jiuyi; ZHANG Lei; ZUO Hongchao; WANG Shigong; FU Congbin; CHOU Jifan; ZHANG Wu; ZUO Jinqing; BI Jianrong; SHI Jinsen; WANG Xin; CHANG Zhoulin; HUANG Zhongwei; YANG Su

    2008-01-01

    Arid and semi-arid areas comprise about 30% of the earth's surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) was established in 2005. SACOL consists of a large set of instruments and focuses on: (1) monitoring of long term tendencies in semiarid climate changes; (2) monitoring of the aerosol effect on the water cycle; (3) studies of interaction between land surface and the atmosphere; (4) improving the land surface and climate models; and (5) validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.

  17. Intercropping competition between apple trees and crops in agroforestry systems on the Loess Plateau of China.

    Science.gov (United States)

    Gao, Lubo; Xu, Huasen; Bi, Huaxing; Xi, Weimin; Bao, Biao; Wang, Xiaoyan; Bi, Chao; Chang, Yifang

    2013-01-01

    Agroforestry has been widely practiced in the Loess Plateau region of China because of its prominent effects in reducing soil and water losses, improving land-use efficiency and increasing economic returns. However, the agroforestry practices may lead to competition between crops and trees for underground soil moisture and nutrients, and the trees on the canopy layer may also lead to shortage of light for crops. In order to minimize interspecific competition and maximize the benefits of tree-based intercropping systems, we studied photosynthesis, growth and yield of soybean (Glycine max L. Merr.) and peanut (Arachis hypogaea L.) by measuring photosynthetically active radiation, net photosynthetic rate, soil moisture and soil nutrients in a plantation of apple (Malus pumila M.) at a spacing of 4 m × 5 m on the Loess Plateau of China. The results showed that for both intercropping systems in the study region, soil moisture was the primary factor affecting the crop yields followed by light. Deficiency of the soil nutrients also had a significant impact on crop yields. Compared with soybean, peanut was more suitable for intercropping with apple trees to obtain economic benefits in the region. We concluded that apple-soybean and apple-peanut intercropping systems can be practical and beneficial in the region. However, the distance between crops and tree rows should be adjusted to minimize interspecies competition. Agronomic measures such as regular canopy pruning, root barriers, additional irrigation and fertilization also should be applied in the intercropping systems.

  18. An experimental method to verify soil conservation by check dams on the Loess Plateau, China.

    Science.gov (United States)

    Xu, X Z; Zhang, H W; Wang, G Q; Chen, S C; Dang, W Q

    2009-12-01

    A successful experiment with a physical model requires necessary conditions of similarity. This study presents an experimental method with a semi-scale physical model. The model is used to monitor and verify soil conservation by check dams in a small watershed on the Loess Plateau of China. During experiments, the model-prototype ratio of geomorphic variables was kept constant under each rainfall event. Consequently, experimental data are available for verification of soil erosion processes in the field and for predicting soil loss in a model watershed with check dams. Thus, it can predict the amount of soil loss in a catchment. This study also mentions four criteria: similarities of watershed geometry, grain size and bare land, Froude number (Fr) for rainfall event, and soil erosion in downscaled models. The efficacy of the proposed method was confirmed using these criteria in two different downscaled model experiments. The B-Model, a large scale model, simulates watershed prototype. The two small scale models, D(a) and D(b), have different erosion rates, but are the same size. These two models simulate hydraulic processes in the B-Model. Experiment results show that while soil loss in the small scale models was converted by multiplying the soil loss scale number, it was very close to that of the B-Model. Obviously, with a semi-scale physical model, experiments are available to verify and predict soil loss in a small watershed area with check dam system on the Loess Plateau, China. PMID:19067210

  19. Effects of Accelerated Soil Erosion on Soil Nutrient Loss After Deforestation on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHENG Fen-Li

    2005-01-01

    Soil erosion and nutrient losses on newly-deforested lands in the Ziwuling Region on the Loess Plateau of China were monitored to quantitatively evaluate the effects of accelerated soil erosion, caused by deforestation, on organic matter,nitrogen and phosphorus losses. Eight natural runoff plots were established on the loessial hill slopes representing different erosion patterns of dominant erosion processes including sheet, rill and shallow gully (similar to ephemeral gully). Sediment samples were collected after each erosive rainfall event. Results showed that soil nutrients losses increased with an increase of erosion intensity. Linear relations between the losses of organic matter, total N, NH4-N, and available P and erosion intensity were found. Nutrient content per unit amount of eroded sediment decreased from the sheet to the shallow gully erosion zones, whereas total nutrient loss increased. Compared with topsoil, nutrients in eroded sediment were enriched,especially available P and NH4-N. The intensity of soil nutrient losses was also closely related to soil erosion intensity and pattern with the most severe soil erosion and nutrient loss occurring in the shallow gully channels on loessial hill slopes.These research findings will help to improve the understanding of the relation between accelerated erosion process after deforestation and soil quality degradation and to design better eco-environmental rehabilitation schemes for the Loess Plateau.

  20. Effect of Vegetation Changes on Soil Erosion on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHENG Fen-Li

    2006-01-01

    Vegetation is one of the key factors affecting soil erosion on the Loess Plateau. The effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from long-term field runoff plots established on the eastern slope of the Ziwuling secondary forest region, China and a field survey. The results showed that before the secondary vegetation restoration period (before about 1866-1872), soil erosion in the Ziwuling region of the Loess Plateau was similar to the current erosion conditions in neighboring regions, where the soil erosion rate now is 8 000 to 10 000t km-2 year-1. After the secondary vegetation restoration, soil erosion was very low; influences of rainfall and slope gradient on soil erosion were small; the vegetation effect on soil erosion was predominant; shallow gully and gully erosion ceased; and sediment deposition occurred in shallow gully and gully channels. In modern times when human activities destroyed secondary forests, soil erosion increased markedly, and erosion rates in the deforested lands reached 10 000 to24 000 t km-2 year-1, which was 797 to 1682 times greater than those in the forested land prior to deforestation. Rainfall intensity and landform greatly affected the soil erosion process after deforestation. These results showed that accelerated erosion caused by vegetation destruction played a key role in soil degradation and eco-environmental deterioration in deforested regions.

  1. Bacterial Community Responses to Soils along a Latitudinal and Vegetation Gradient on the Loess Plateau, China.

    Science.gov (United States)

    Zeng, Quanchao; Dong, Yanghong; An, Shaoshan

    2016-01-01

    Soil bacterial communities play an important role in nutrient recycling and storage in terrestrial ecosystems. Loess soils are one of the most important soil resources for maintaining the stability of vegetation ecosystems and are mainly distributed in northwest China. Estimating the distributions and affecting factors of soil bacterial communities associated with various types of vegetation will inform our understanding of the effect of vegetation restoration and climate change on these processes. In this study, we collected soil samples from 15 sites from north to south on the Loess Plateau of China that represent different ecosystem types and analyzed the distributions of soil bacterial communities by high-throughput 454 pyrosequencing. The results showed that the 142444 sequences were grouped into 36816 operational taxonomic units (OTUs) based on 97% similarity. The results of the analysis showed that the dominant taxonomic phyla observed in all samples were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes. Actinobacteria and Proteobacteria were the two most abundant groups in all samples. The relative abundance of Actinobacteria increased from 14.73% to 40.22% as the ecosystem changed from forest to sandy, while the relative abundance of Proteobacteria decreased from 35.35% to 21.40%. Actinobacteria and Proteobacteria had significant correlations with mean annual precipitation (MAP), pH, and soil moisture and nutrients. MAP was significantly correlated with soil chemical and physical properties. The relative abundance of Actinobacteria, Proteobacteria and Planctomycetes correlated significantly with MAP, suggesting that MAP was a key factor that affected the soil bacterial community composition. However, along with the MAP gradient, Chloroflexi, Bacteroidetes and Cyanobacteria had narrow ranges that did not significantly vary with the soil and environmental factors. Overall, we conclude that the edaphic properties and/or vegetation

  2. Effect of rainfall regime and slope on runoff in a gullied loess region on the Loess Plateau in China.

    Science.gov (United States)

    Fang, H Y; Cai, Q G; Chen, H; Li, Q Y

    2008-09-01

    Runoff was measured from seven plots with different slopes nested in Tuanshangou catchment on the Loess Plateau to study effect of slopes on runoff in relation to rainfall regimes. Based on nine years of field observation and K-mean clusters, 84 rainfall events were grouped into three rainfall regimes. Rainfall regime A is the group of events with strong rainfall intensity, high frequency, and short duration. Rainfall regime C consists of events with low intensity, long duration, and infrequent occurrence. Rainfall regime B is the aggregation of events of medium intensity and medium duration, and less frequent occurrence. The following results were found: (1) Different from traditional studies, runoff coefficient neither decreased nor increased, but presented peak value on the slope surfaces; (2) For individual plot, runoff coefficients induced by rainfall regime A were the highest, and those induced by rainfall regime C were the lowest; Downslope, the runoff coefficients induced by three rainfall regimes presented the same changing trend, although the peak value induced by regime A occurred on a shorter slope length compared to those by regime B and C; (3) Scale effect on runoff induced by rainfall regime A was the least, and that induced by rainfall regime C was the largest. These results can be explained by the interactions of crusting, soil moisture content, slope length and gradient, and erosion units, etc., in the context of different rainfall regimes.

  3. Conservation Tillage on the Loess Plateau, China: Food security, Yes; Carbon sequestration, No?

    Science.gov (United States)

    Kuhn, Nikolaus; Hu, Yaxian; Xiao, Liangang; Greenwood, Phil; Bloemertz, Lena

    2015-04-01

    Climate change is expected to affect food security globally and increase the variability in food supply. At the same time, agricultural practices offer a great potential for mitigating and adapting to climate change. In China, food security has increased in the last decades with the number of undernourished people declining from 21% in 1990 to 12% today. However, the limited relative amount of arable land and scarce water supplies will remain a challenge. The Loess Plateau of China, located in the mid-upper reaches of the Yellow River and has an area of some 630000 km2 with a high agricultural potential. However, due to heavy summer rainstorms, steep slopes, low vegetation cover, and highly erodible soils, the Loess Plateau has become one of the most severely eroded areas in the world. Up to 70% of arable land is affected by an annual soil loss of 20-25 ton ha-1, far exceeding the threshold for sustainable use (10 ton ha-1). Rainfed farming systems are dominant on the Loess Plateau, and the farmers in this area have been exposed to a steadily increasing temperature as well as an erratic, but slightly decreasing rainfall since 1970. Therefore, adaptation of the regional agriculture is required to adapt to climate change and may be even engaged in mitigation. This study analyzed the potential contribution of conservation tillage to adaptation and mitigation of climate change on the Loess Plateau. In total, 15 papers published in English were reviewed, comparing two tillage practices, conventional tillage (CT) and conservation tillage typically represented by no-tillage (NT). Soil organic carbon (SOC) stock across soil depths as well yields and the inter-annual variations with regards to and their annual rainfall precipitation were compared for NT and CT. Our results show that: 1) The benefit of NT compared to CT in terms of increasing total SOC stocks diminishes with soil depth, questioning the use of average SOC stocks observed in topsoil to estimate the potential

  4. Long-Term Monitoring of Rainfed Wheat Yield and Soil Water at the Loess Plateau Reveals Low Water Use Efficiency

    NARCIS (Netherlands)

    Qin, W.; Chi, B.L.; Oenema, O.

    2013-01-01

    Increasing crop yield and water use efficiency (WUE) in dryland farming requires a quantitative understanding of relationships between crop yield and the water balance over many years. Here, we report on a long-term dryland monitoring site at the Loess Plateau, Shanxi, China, where winter wheat was

  5. Soil water infiltration impacted by maize (zea mays) growth on sloping agricultural land of the loess plateau

    Science.gov (United States)

    Increasing infiltration rates of sloping agricultural land from arid and semiarid regions not only affects water supply and precipitation transformations in soil directly, but also impacts erosion intensity. This is extremely important to the Loess Plateau regions of Northwest China, where a majorit...

  6. The role of climatic and anthropogenic stresses on long-term runoff reduction from the Loess Plateau, China.

    Science.gov (United States)

    Feng, Xiaoming; Cheng, Wei; Fu, Bojie; Lü, Yihe

    2016-11-15

    Human intervention has strongly altered patterns of river runoff. Yet, few studies have addressed the complexity and nonlinearity of the anthropogenic stresses on runoff or their interaction with climate. We study the Loess Plateau in China, whose river runoff contributes 65% of the discharge to the middle reach of the Yellow River; this landscape has been shaped by human activity and is intensively managed. Our purpose is to characterize the interactive roles of climate and human activities in defining river runoff from the Loess Plateau. Applying a transient analysis to discover the time-varying runoff trend and impact factors, we found that the average runoff in the Loess Plateau decreased continuously during the period 1961-2009 (average rate of -0.9mmyear(-1), Panthropogenic transition, causing a 56% reduction in available freshwater resources during the period 1961-2009. These findings highlight the need for studies that address the dynamic and nonlinear processes controlling the availability of freshwater resources in the light of anthropogenic influences applied under a changing climate. Such studies are essential if we are to meet the human water demand in the Loess Plateau region. PMID:27422727

  7. Mineral Composition of Loess—Paleosol Samples from the Loess Plateau of China and Its Environmental Significance

    Institute of Scientific and Technical Information of China (English)

    郑洪汉; B.K.G.THENG; 等

    1994-01-01

    34samples of loess-paleosol from the Luochuan and Xifeng sections in the Loess Plateau,northern China were eparated into sand,silt and clay fractions and analyzed for their mineral compositions.The results indicate that there is almost no difference between loess and paleosol in mineral composition.Major mineral species are quartz,mica,feldspar and chlorite,accounting for about 88-92% of the total;other minerals are kandite,smectite,vermiculite and a few heavy minerals.The calcite,magnetite and hematite were not taken into consideration because of their removal in the process of sample preparation.The main difference with respect to the mineral composition of samples collected from different sections and different statigraphic levels lies in the amount and grain size of minerals hosted.Comparisons between the Luochuan section and the Xifeng section,between paleosol and loess and between the upper part and the lower part of some paleosol layers show that the formers contain less feldspar but more mica and vermiculite and are finer in grain size,indicating the co-occurrence of both biochemical weathering process responsible for mineral change and physical weathering process leading to grain-size change during the soil-forming processes.This result favours such an explanation of the soil-forming mechanism that loess deposition and paleosol development occurred synchronously,though the rate of soil formation was greater than that of loess deposition,thus leading to soil development.

  8. Quartz red TL SAR equivalent dose overestimation for Chinese loess

    DEFF Research Database (Denmark)

    Lai, Z.P.; Murray, A.S.; Bailey, R.M.;

    2006-01-01

    For the red TL of quartz extracted from Chinese loess, the single-aliquot regenerative-dose (SAR) procedure overestimates the known laboratory doses in dose recovery test. The overestimation is the result of the first heating during the measurement of natural TL signal causing a sensitivity...... reduction, which is not corrected for using a SAR protocol. The SARA procedure was used to measure the sensitivity change. Using this as a correction factor is tested by comparison with the quartz optically stimulated luminiscence (OSL) equivalent dose. SARA is also employed to determine the residual level...... of red TL, which is found to be more than 100 Gy. (c) 2005 Elsevier Ltd. All rights reserved....

  9. Ways to Improve Low-Benefit Black Locust Forests in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Guo Xiao-ping; Zhu Jin-zhao; Yu Xin-xiao; Luo Jing

    2005-01-01

    This paper presents a general standard for the low-benefit black locust (Robinia pseudoacacia L.) forests in Loess Plateau based on defining the concept of "tri-low forest", and emphasizes the major factors which result in low-benefit black locust,such as, lack of soil moisture of forest and nutrient, breaching the principle of matching tree species to sites, and high density of forests. Based on different characteristics of low-benefit forests, following the principle of "adjusting measures to local conditions, giving priority to ecological benefits, assisting with economic benefits", the authors put forward some technical ways to reform low-benefit black locust forests, for example, taking measurements of collecting runoff and storing water, lowering the forest density,introducing mixed forests and transforming species, directive breeding and so on.

  10. RUNOFF GENERATION CHARACTERISTICS IN TYPICAL EROSION REGIONS ON THE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    Li CHEN; Qingquan LIU; Jiachun LI

    2001-01-01

    This paper presents a process-based model for runoff generation on slopes. One dimensional kinematic wave theory combined with the revised Green-Ampt infiltration formula is applied in the model. According to the characteristics of soil and rainfall in the Loess Plateau area, six types of storm are defined, and among them three typical erosion zones that have different values of representative parameters are chosen to simulate the runoff generation processes. The primary hydraulic characteristics of the runoff generation, such as unit discharge, runoff depth, flow velocity, shear stress and ratio of runoff generation, are obtained and analyzed. The results demonstrate that the different erosion characteristics are related to different runoff generation zones.

  11. Water and Energy Conservation of Rainwater Harvesting System in the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhi-yun; LI Xiao-yan; MA Yu-jun

    2013-01-01

    Water is the source of all the creatures on the earth and energy is the main factor driving the world. With the increasing population and global change, water and energy conservation have become worldwide focal issues, particularly in the water-stressed and energy-limited regions. Rainwater harvesting, based on the collection and storage of rainfall runoff, has been widely used for domestic use and agricultural production in arid and semiarid regions. It has advantages of simple operation, high adaption, low cost and less energy consumption. This study reviewed rainwater harvesting systems adopted in the Loess Plateau of China and analyzed water use efficiency (WUE) for various rainwater harvesting techniques. Supplemental irrigation using harvested rainwater could increase crop yield by more than 30%, and WUE ranged from 0.7 to 5.7 kg m-3 for spring wheat, corn and flax, and 30-40 kg m-3 for vegetables. Moreover, energy consumption for rainwater harvesting based on single family was compared with traditional water supply in the city of the Loess Plateau using the life cycle assessment (LCA) method. Results showed that energy consumption yielded per unit harvested rainwater was 25.96 MJ m-3 yr-1 which was much less than 62.25 MJ m-3 yr-1 for main water supply in Baoji City, Shanxi Province, meaning that rainwater harvesting saved energy by 139.8%as compared to the main water supply system. This study highlights the importance and potential of rainwater harvesting for water and energy conservation in the near future.

  12. A model for vertical distribution of fine roots in Robinia pseudoacacia plantations on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiangrong; ZHAO Zhong; GUO Mancai; WANG Dihai; YUAN Zhifa

    2007-01-01

    Based on a detailed investigation of vertical distributions of fine roots in Robinia pseudoacacia plantations at the Ansai Soil and Water Conservation Station,Shaanxi Province,a model was developed for the deep distribution of fine roots of R.pseudoacacia,which reflects the growth of fine roots affected by the mixed process of infiltration water and deep soil water.The maximum depth of the distribution hmax and the depth of the highest fine root density (FRD) hp were determined and the maximum depth of infiltration water supplied for fine root growth hq could also be calculated,hq was considered as the approximate boundary between infiltration water and deep soil water in support of the growth of fine roots.According to the model,the soil water of R.pseudoacacia woodland in the profile could be classified into three layers:the first layer from the soil surface to hp was the active water exchange layer,very much affected by precipitation;the second was the soil water attenuation layer,between hp and hq and largely affected by the vertical distribution of fine roots;.the third was the relatively stable soil water layer below hq,below which soil water did not change much.The percentage of infiltration water supplied for the growth of fine roots reached a level of 88.32% on the shaded slopes and 85.21% on sunny slopes.This indicated infiltration of precipitation played a crucial role in the growth of R.pseudoacacia in the gully region of the Loess Plateau.The research of interaction between the distribution of fine roots and soil water in the profile will help to explain the reasons for the complete drying out of soils and provide a theoretical basis for continuing the policy of matching tree species with sites on the Loess Plateau.

  13. 黄土高原发展过程中的五大转折%The five major changes in the evolution of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    赵景波

    2005-01-01

    On the basis of the geomorphology, paleosol, paleoclimate and loess age, major changes of the Loess Plateau were studied. There are five major changes in the evolution of the Loess Plateau in China. Among them, the first, second, third and fourth major changes have taken place since the formation of the Loess Plateau, and the fifth major change will happen in 100 years. The first major change, which occurred at about 2.50 Ma BP, was a transition from red earth plateau to the Loess Plateau, and reflects the climate from the warm-sub-humid to the alteration between cold-and-dry and warm-and-humid. The driving force of this first major change was climate. The second major change,which took place at about 1.60 Ma BP, was a vital transition of the main rivers in this area from non-existence to existence, and represented an important change on the Loess Plateau's neotectonic uplift from the slow rising to periodically accelerated rising, and making the river's erosion go from feeble to strong. The driving force of the second major change is tectonic uplift. The third major change which occurred at about 150 ka, was a great transition of the Yellow River's inpouring from a lake outlet to a sea outlet. At that time, the Yellow River cut the Sanmen Gorge. The transition led to the transformation of loess material from internal transportation to external transportation. The driving force of the third major change was running water erosion. The fourth one that occurred at about 1.1 ka was a change of the Loess Plateau from natural erosion to erosion accelerated by human influences.The driving force of the fourth major change is mainly human activities. The fifth major change,which is the opposite change to the fourth one, in which the motive power is human activity, too.

  14. Effects of Stubble Management on Soil Fertility and Crop Yield of Rainfed Area in Western Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    G. B. Huang

    2012-01-01

    Full Text Available The combination of continuous cereal cropping, tillage and stubble removal reduces soil fertility and increases soil erosion on sloping land. The objective of the present study was to assessment soil fertility changes under stubble removal and stubble retention in the Loess Plateau where soil is prone to severe erosion. It was indicated that soil N increased a lot for and two stubble retention treatments had the higher N balance at the end of two rotations. Soil K balance performed that soil K was in deficient for all treatments and two stubble retention treatments had lower deficit K. The treatments with stubble retention produced higher grain yields than the stubble removal treatments. It was concluded that stubble retention should be conducted to increase crops productivity, improve soil fertility as well as agriculture sustainability in the Loess plateau, China.

  15. NDVI Variation and Its Responses to Climate Change on the Northern Loess Plateau of China from 1998 to 2012

    OpenAIRE

    Tingting Ning; Wenzhao Liu; Wen Lin; Xiaoqiang Song

    2015-01-01

    This study analyzed temporal and spatial changes of normalized difference vegetation index (NDVI) on the northern Loess Plateau and their correlation with climatic factors from 1998 to 2012. The possible impacts of human activities on the NDVI changes were also explored. The results showed that (1) the annual maximum NDVI showed an upward trend. The significantly increased NDVI and decreasing severe desertification areas demonstrate that the vegetation condition improved in this area. (2) Ove...

  16. Evaluating Sustainability of Cropland Use in Yuanzhou County of the Loess Plateau, China Using an Emergy-Based Ecological Footprint

    OpenAIRE

    Bai, Xiaomei; Wen, Zhongming; An, Shaoshan; Li, Bicheng

    2015-01-01

    Evaluating the sustainability of cropland use is essential for guaranteeing a secure food supply and accomplishing agriculture sustainable development. This study was conducted in the ecologically vulnerable Loess Plateau region of China to evaluate the sustainability of cropland use based on an ecological footprint model that integrates emergy analysis. One modified method proposed in 2005 is known as the emergetic ecological footprint (EEF). We enhanced the method by accounting for both the...

  17. A Policy-Driven Large Scale Ecological Restoration: Quantifying Ecosystem Services Changes in the Loess Plateau of China

    OpenAIRE

    Lü, Yihe; Fu, Bojie; Feng, Xiaoming; Zeng, Yuan; Liu, Yu; Chang, Ruiying; Sun, Ge; Wu, Bingfang

    2012-01-01

    As one of the key tools for regulating human-ecosystem relations, environmental conservation policies can promote ecological rehabilitation across a variety of spatiotemporal scales. However, quantifying the ecological effects of such policies at the regional level is difficult. A case study was conducted at the regional level in the ecologically vulnerable region of the Loess Plateau, China, through the use of several methods including the Universal Soil Loss Equation (USLE), hydrological mo...

  18. Changes in extreme temperature and precipitation events in the Loess Plateau (China) during 1960-2013 under global warming

    Science.gov (United States)

    Sun, Wenyi; Mu, Xingmin; Song, Xiaoyan; Wu, Dan; Cheng, Aifang; Qiu, Bing

    2016-02-01

    In recent decades, extreme climatic events have been a major issue worldwide. Regional assessments on various climates and geographic regions are needed for understanding uncertainties in extreme events' responses to global warming. The objective of this study was to assess the annual and decadal trends in 12 extreme temperature and 10 extreme precipitation indices in terms of intensity, frequency, and duration over the Loess Plateau during 1960-2013. The results indicated that the regionally averaged trends in temperature extremes were consistent with global warming. The occurrence of warm extremes, including summer days (SU), tropical nights (TR), warm days (TX90), and nights (TN90) and a warm spell duration indicator (WSDI), increased by 2.76 (P duration indicator (CSDI) exhibited decreases of - 3.22 (P intensity (SDII) exhibited significant decreases (- 0.14 mm/day/decade, P = 0.0158), whereas consecutive dry days (CDD) significantly increased (1.96 days/decade, P = 0.0001) during 1960-2013. Most of stations with significant changes in SDII and CDD occurred in central and southeastern Loess Plateau. However, the changes in days of erosive rainfall, heavy rain, rainstorm, maximum 5-day precipitation, and very-wet-day and extremely wet-day precipitation were not significant. Large-scale atmospheric circulation indices, such as the Western Pacific Subtropical High Intensity Index (WPSHII) and Arctic Oscillation (AO), strongly influences warm/cold extremes and contributes significantly to climate changes in the Loess Plateau. The enhanced geopotential height over the Eurasian continent and increase in water vapor divergence in the rainy season have contributed to the changes of the rapid warming and consecutive drying in the Loess Plateau.

  19. ECO-ENVIRONMENT CHANGE AND SOIL EROSION PROCESS IN THE RECLAIMED FORESTLAND OF THE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    ZHA Xiao-chun; TANG Ke-li

    2003-01-01

    Serious soil erosion has made the eco-environment fragile in the Loess Plateau. Based on the 10-year da-ta observed from 1989 to 1998 in the Ziwuling Survey Station in loess hilly region, the eco-environment change and soil erosion process in reclaimed forestland were studied in this paper. The results showed that the intensity of man-made soil erosion caused by forestland reclamation was 1000 times more than that of the natural erosion. From the analysis of soil physical and mechanical properties, in the 10th year after forestland was reclaimed, the clay content and physical clay content decreased 2.74 percentage point and 3.01 percentage point respectively, the >0.25mm water-stable aggregate content decreased 31.59 percentage point, the soil bulk density increased and soil shear strength de-creased, all of which were easier to cause soil erosion. The correlation analysis showed that >0.25mm waterstable ag-gregate content was the key factor affecting soil erosion, and the secondary factors were soil coarse grain and soil shear strength. The relation between the >0.25mm waterstable aggregate content, the soil sheer strength and the soil erosion intensity were analyzed, which showed that the first year and the seventh erosion year were the turn years of the soil erosion intensity after the forestland was reclaimed, revealed that the change ofeco-environment was the main cause to accelerate soil erosion, and the worse environment caused soil erosion to be serious rapidly.

  20. Characteristics and mechanisms of Ni(Ⅱ) removal from aqueous solution by Chinese loess

    Institute of Scientific and Technical Information of China (English)

    王艳; 唐晓武; 王恒宇

    2015-01-01

    Nickel is a toxic heavy metal among trace elements which has a detrimental impact on living organisms. There is growing need of finding an economic and effective solution for Ni(Ⅱ) immobilization in environments. Chinese loess was selected as adsorbent to remove Ni(Ⅱ) from aqueous solution. Adsorbent dosage, reaction time, solute concentration, temperature, and solution p H also have influences on efficiency of Ni(Ⅱ) removal. The monolayer adsorption capacity of loess towards Ni(Ⅱ) is determined to be about 15.61 mg/g. High temperature and p H favor the removal of Ni(Ⅱ) using Chinese loess soil and the optimal dosage of loess is determined to be 10 g/L. The kinetics and adsorption isotherms of the adsorption process can be best-fitted with the pseudo second order kinetics and Langmuir isothermal model, respectively. The thermodynamic analysis reveals that the adsorption process is spontaneous, endothermic and the system disorder increases with duration. Nickel ions can be removed with the removal efficiency of 98.5% at p H greater than or equal to 9.7. Further studies on loess and Ni(Ⅱ) laden loess(using X-Ray diffraction, Fourier transform infrared spectroscopy) and Ni(Ⅱ) species distribution at various p H have been conducted to discuss the adsorption mechanism. Loess soils in China have proven to be a potential adsorbent for Ni(Ⅱ) removal from aqueous solutions.

  1. Characteristics and mechanisms of Ni(II) removal from aqueous solution by Chinese loess

    Institute of Scientific and Technical Information of China (English)

    王艳; 唐晓武; 王恒宇

    2015-01-01

    Nickel is a toxic heavy metal among trace elements which has a detrimental impact on living organisms. There is growing need of finding an economic and effective solution for Ni(II) immobilization in environments. Chinese loess was selected as adsorbent to remove Ni(II) from aqueous solution. Adsorbent dosage, reaction time, solute concentration, temperature, and solution pH also have influences on efficiency of Ni(II) removal. The monolayer adsorption capacity of loess towards Ni(II) is determined to be about 15.61 mg/g. High temperature and pH favor the removal of Ni(II) using Chinese loess soil and the optimal dosage of loess is determined to be 10 g/L. The kinetics and adsorption isotherms of the adsorption process can be best-fitted with the pseudo second order kinetics and Langmuir isothermal model, respectively. The thermodynamic analysis reveals that the adsorption process is spontaneous, endothermic and the system disorder increases with duration. Nickel ions can be removed with the removal efficiency of 98.5% at pH greater than or equal to 9.7. Further studies on loess and Ni(II) laden loess (using X-Ray diffraction, Fourier transform infrared spectroscopy) and Ni(II) species distribution at various pH have been conducted to discuss the adsorption mechanism. Loess soils in China have proven to be a potential adsorbent for Ni(II) removal from aqueous solutions.

  2. Effects of soil drought on seedling growth and water metabolism of three common shrubs in Loess Plateau, Northwest China

    Institute of Scientific and Technical Information of China (English)

    AN Yuyan; LIANG Zongsuo; HAN Ruilian; LIU Guobin

    2007-01-01

    The growth and water metabolism of three common shrubs on the Loess Plateau were studied under soil with different water contents.Results showed that water consumption of those species decreased with the increase in drought stress,and water consumptions of these shrubs were different:Forsythia suspensa was the greatest,and Syringa oblata was the lowest.The growth rate of new branches and leaf area of three species were the fastest under adequate soil water conditions,and were the lowest under severe drought.Under the same water conditions,the growth ofF.suspensa was the fastest while that ofS.oblata was the slowest.The water content,proline and chlorophyll content of different species changed with the increase in soil water stress.The leaf water content of Periploca sepium and F.suspensa was obviously higher than that of S.oblata,while the leaf proline content of F.suspensa and S.oblata was lower than that ofP sepium.The ratio leaf chlorophyll a:b of F.suspensa and S.oblata decreased with the decrease in soil water content.Although these three shrubs had different mechanisms in response to drought stress,they all had higher drought resistance and could adapt to the drought condition on the Loess Plateau.This paper provided some bases for choosing tree species on the Loess Plateau.

  3. Monitoring vegetation phenology and their response to climate change on Chinese Loess Plateau based on remote sensing%基于遥感的黄土高原植被物候监测及其对气候变化的响应

    Institute of Scientific and Technical Information of China (English)

    谢宝妮; 秦占飞; 王洋; 常庆瑞

    2015-01-01

    It is crucial to understand vegetation phenology changes and their relationship with climate change at biome-level when projecting regional ecosystem carbon exchange and climate-biosphere interactions. To further understand the relationship between vegetation growth and climatic factors, in this study, we investigated the variation in vegetation phenology and its linkage with climate change on the Chinese Loess Plateau through analyzing the Land Long Term Data Record (LTDR) NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) and concurrent temperature and precipitation during 1982-2011. Firstly, the maximum value composite (MVC) method was used to composite the 10 d LTDR NDVI dataset in order to reduce effects of atmospheric and cloud noise. The Harmonic Analysis of Time Series (HANTS) method of HANTS software was used to filter points which were still affected by cloud noise after the MVC was used composite and reconstruct the NDVI time series datasets. Secondly, the 30-year average seasonal NDVI curves for the whole study area and each vegetation type were calculated. Pixels with yearly mean values below 0.1 were excluded from the analysis to ensure the inclusion of sparsely vegetated areas in the analysis. The relative change ratio of NDVI was then calculated from the 30-year average NDVI seasonal curves. We then used the maximum and minimum values for relative change ratio of NDVI as the threshold for the onset dates of vegetation green-up (the beginning of growing season, BGS) and dormancy (the end of growing season, EGS). Finally, linear least square regression was employed to estimate the trends of phenology. Partial correlation analysis was performed between the EGS/ BGS and mean monthly temperature and total monthly precipitation. The results showed that vegetation phenology in the study area generally commenced on Julian day 96-150 for natural vegetation and 72-112 for artificial vegetation. The vegetation dormancy usually began on Julian day 283

  4. MACROPORE FLOW AND MASS WASTING OF GULLIES IN THE LOESS PLATEAU, CHINA

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Due to the extensive gullying from historically excessive erosion in the loess plateau of China, much of this region is being converted to native grass and shrub vegetation. Tunnel scour and mass wasting are important gully erosion processes resulting from preferential flow through macropores ( pores > 1 mm diameter). The objective of this study is to assess the changes with time in macropore flow characteristics of soils on the Loess Plateau following conversion to grass vegetation and the associated degree of mass wasting of gully faces. Ridge areas that had been revegetated for 1 year, 6 years, and > 15 years following tilling, and for 6 years following contour-ditching and the adjacent gully faces were characterized for their macropore and soil matrix properties on a 50 cm by 50 cm area. The total number of macropores increased from 11.6/m2 to 39.6/m2 from 1 to 6 years and to 51.6/m2 after 15 years of revegetation following tillage. The macroporosity increased from 0.0008 m3/m3 to 0.0018 m3/m3 from 1 to 6 years of revegetation following tillage but the lowest macroporosity (0.0005 m3/m3) was 6 years of revegetation following contour-ditching. The contour-ditched area had the lowest infiltration rate (95 m/d) through the soil matrix (areas without macropores) with the tilled areas having similar infiltration rates regardless of the number of years of revegetation (averaged 146 m/d). Due to tunnel scour erosion of macropores during infiltration into the area revegetated for 1 year, pore diameters enlarged by more than 200% resulting in this condition having the highest individual macropore infiltration rates (7967 m/d). Macropores in all other areas were stable with no tunnel scour erosion of macropores. The total capacity for infiltration through macropores increased significantly with time following revegetation. The number of macropores on the gully faces was triple (92.8/m2) and the macroporosity quadruple (0.004 m3/m3) that of the ridge surfaces. The upper

  5. Regional effects of vegetation restoration on water yield across the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    X. M. Feng

    2012-08-01

    Full Text Available The general relationships between vegetation and water yield under different climatic regimes are well established at a small watershed scale in the past century. However, applications of these basic theories to evaluate the regional effects of land cover change on water resources remain challenging due to the complex interactions of vegetation and climatic variability and hydrologic processes at the large scale. The objective of this study was to explore ways to examine the spatial and temporal effects of a large ecological restoration project on water yield across the Loess Plateau region in northern China. We estimated annual water yield as the difference between precipitation input and modelled actual evapotranspiration (ET output. We constructed a monthly ET model using published ET data derived from eddy flux measurements and watershed streamflow data. We validated the ET models at a watershed and regional levels. The model was then applied to examine regional water yield under land cover change and climatic variability during the implementation of the Grain-for-Green (GFG project during 1999–2007. We found that water yield in 38% of the Loess Plateau area might have decreased (1–48 mm per year as a result of land cover change alone. However, combined with climatic variability, 37% of the study area might have seen a decrease in water yield with a range of 1–54 mm per year, and 35% of the study area might have seen an increase with a range of 1–10 mm per year. Across the study region, climate variability masked or strengthened the water yield response to vegetation restoration. The absolute annual water yield change due to vegetation restoration varied with precipitation regimes with the highest in wet years, but the relative water yield changes were most pronounced in dry years. We concluded that the effects of land cover change associated with ecological restoration varied greatly over time and space and were strongly influenced

  6. Hydrologic feasibility of artificial forestation in the semi-arid Loess Plateau of China

    Directory of Open Access Journals (Sweden)

    T. T. Jin

    2011-08-01

    Full Text Available Hydrologic viability, in terms of moisture availability, is fundamental to ecosystem sustainability in arid and semi-arid regions. In this study, we examine the spatial distribution and after-planting variations of soil moisture content (SMC in black locust tree (Robinia pseudoacacia L. plantings in the Loess Plateau of China at a regional scale. Thirty sites (5 to 45 yr old were selected, spanning an area of 300 km by 190 km in the northern region of the Shaanxi Province. The SMC was measured to a depth of 100 cm at intervals of 10 cm. Geographical, topographic and vegetation information was recorded, and soil organic matter was evaluated. The results show that, at the regional scale, SMC spatial variability was most highly correlated with rainfall. The negative relationship between the SMC at a depth of 20–50 cm and the stand age was stronger than at other depths, although this relationship was not significant at a 5 % level. Watershed analysis shows that the after-planting SMC variation differed depending upon precipitation. The SMC of plantings in areas receiving sufficient precipitation (e.g., mean annual precipitation (MAP of 617 mm may increase with stand age due to improvements in soil water-holding capacity and water-retention abilities after planting. For areas experiencing water shortages (e.g., MAP = 509 mm, evapotranspiration may cause planting soils to dry within the first 20 yr of growth. It is expected that, as arid and semi-arid plantings age, evapotranspiration will decrease, and the soil profile may gradually recover. In extremely dry areas (e.g., MAP = 352 mm, the variation in after-planting SMC with stand age was found to be negligible. The MAP can be used as an index to divide the study area into different ecological regions. Afforestation may sequentially exert positive, negative and negligible effects on SMCs with a decrease in the MAP. Therefore, future restoration measures should correspond to the local climate

  7. Dynamics of CO2 fluxes and environmental responses in the rain-fed winter wheat ecosystem of the Loess Plateau, China.

    Science.gov (United States)

    Wang, Wen; Liao, Yuncheng; Wen, Xiaoxia; Guo, Qiang

    2013-09-01

    Chinese Loess Plateau plays an important role in carbon balance of terrestrial ecosystems. Continuous measurement of CO2 fluxes in cropland ecosystem is of great significance to accurately evaluate the carbon sequestration potential and to better explain the carbon cycle process in this region. By using the eddy covariance system we conducted a long-term (from Sep 2009 to Jun 2010) CO2 fluxes measurement in the rain-fed winter wheat field of the Chinese Loess Plateau and elaborated the responses of CO2 fluxes to environmental factors. The results show that the winter wheat ecosystem has distinct seasonal dynamics of CO2 fluxes. The total net ecosystem CO2 exchange (NEE) of -218.9±11.5 gC m(-2) in the growing season, however, after considering the harvested grain, the agro-ecosystem turned into a weak carbon sink (-36.2 gC m(-2)). On the other hand, the responses of CO2 fluxes to environmental factors depended on different growth stages of winter wheat and different ranges of environmental variables, suggesting that the variations in CO2 exchange were sensitive to the changes in controlling factors. Particularly, we found the pulse response of ecosystem respiration (Reco) to a large rainfall event, and the strong fluctuations of CO2 fluxes usually appeared after effective rainfall events (daily precipitation > 5 mm) during middle growing season. Such phenomenon also occurred in the case of the drastic changes in air temperature and within 5 days after field management (e.g. tillage and plough). PMID:23712111

  8. Land use and land cover change processes in China's eastern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    JinChang Li; HaiXia Liu; Yong Liu; ZhiZhu Su; ZiQiang Du

    2015-01-01

    Using Landsat remote sensing images, we analyzed changes in each land use type and transitions among different land use types during land use and land cover change (LUCC) in Ningwu County, located in the eastern Loess Plateau of China, from 1990 to 2010. We found that grassland, woodland, and farmland were the main land use types in the study area, and the area of each type changed slightly from 1990 to 2010, whereas the area of water, construction land, and unused land increased greatly. For the whole area, the net change and total change were insignificant due to weak human activity intensity in most of the study area, and the LUCC was dominated by quasi-balanced two-way transitions from 1990 to 2010. The insignificant overall amount of LUCC appears to have resulted from offsetting of rapid increases in population, economic growth, and the im-plementation of a program to return farmland to woodland and grassland in 2000. This program converted more farmland into woodland and grassland from 2000 to 2010 than from 1990 to 2000, but reclamation of woodland and grassland for use as farmland continued from 2000 to 2010, and is a cause for concern to the local government.

  9. Soil erosion and sediment transport in the gullied Loess Plateau:Scale effects and their mechanisms

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Scale effects exist in the whole process of rainfall―runoff―soil erosion―sediment transport in river basins.The differences of hydrographs and sediment graphs in different positions in a river basin are treated as basic scale effects,which are more complex in the gullied Loess Plateau,a region notorious for high intensity soil erosion and hyper-concentrated sediment-laden flow.The up-scaling method of direct extrapolation that maintains dynamical mechanism effective in large scale application was cho-sen as the methodology of this paper.Firstly,scale effects of hydrographs and sediment graphs were analyzed by using field data,and key sub-processes and their mechanisms contributing to scale effects were clearly defined.Then,the Digital Yellow River Model that integrates sub-models for the sub-processes was used with high resolution to simulate rainfall―runoff―soil erosion―sediment transport response in Chabagou watershed,and the distributed results representing scale effects were obtained.Finally,analysis on the simulation results was carried out.It was shown that gravitational erosion and hyper-concentrated flow contribute most to the spatial variation of hydrographs and sediment graphs in the spatial scale.Different spatial scale distributions and superposition of different sub-processes are the mechanisms of scale effects.

  10. Characterizing changes in ecosystem service values in China's eastern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    JinChang Li; HaiXia Liu; ZhiZhu Su; Yong Liu; YongGang Yang

    2015-01-01

    Human activities such as the implementation of ecological protection projects and expansion of construction land can cause complex land use changes that affect ecosystem service values (ESV). In this study, we investigated changes in ESV in response to land use changes in Ningwu County, in eastern Loess Plateau of China. Our aim is to provide guidance for sustainable land use planning in this region. We used remote sensing to evaluate land use changes, and applied a fast, proxy-based method for evaluating ESV at three points in time:1990, 2000, and 2010. More than 89%of the total ESV in Ningwu County was attributable to woodland and grassland. The ESV in western mountain areas show the greatest increase from 1990 to 2010, but ESV decreased the most in the low-elevation northeastern area of flat terrain. These tradeoffs led to a slight net decrease (1.0%) in Ningwu County's total ESV. Although the decline in ESV was relatively low compared to the rate of economic growth, total ESV was much lower than global and national average levels at the end of the study period.

  11. Land degradation, government subsidy, and smallholders' conservation decision: the case of the loess plateau in China

    Institute of Scientific and Technical Information of China (English)

    石敏俊; CHENKevin

    2004-01-01

    Land degradation is one of the severe environmental problems in China. In order to combat land degradation, a soil conservation program was introduced since 2000 to reduce soil erosion by converting slope-cultivated land into forestry and pasture. This paper represents the first systematic attempt to investigate the impact of the soil conservation program on land degradation in the loess plateau. The results indicate that the soil conservation program to convert slope fields into forest or pasture is an effective way to combat soil erosion. However, a subsidy that is higher than profit of land use activity of slope fields before their conversion into forest and pasture is needed to encourage farmers to join the conservation program. A policy measure to encourage and assist farmers to develop sedentary livestock by using crops produced from fields as well as fodder and forage grass from the converted slope fields might contribute to combat soil erosion. Increase in off-farm job opportunities may encourage households to reduce cultivation in slope fields. That implies a policy measure to encourage rural urbanization might contribute to combat soil erosion.

  12. Relationship Between Agriculture and Ecological Deterioration, Restoration and Reconstruction in Loess Plateau Areas of Northwest China

    Institute of Scientific and Technical Information of China (English)

    CHENG Xu

    2002-01-01

    A comprehensive analysis was conducted on the current situation as well as historic succession process of agriculture and ecological conditions in Northwest China, in particular in the Loess Plateau, by means of a inter-disciplinary approach of ecology, agro-geohistory, and agronomy. It was concluded that the fundamental causes responsible for the ecological deterioration, signed by the poor agro-productivity and serious soil erosion, had been the extensive cropping system by ever-increasing reclamation on semi-drought slope land, where initiated a natural vegetation of brushy grasses with sparse trees, thus suitable only for animal husbandry. Based on an identification of specific actual status of China, several countermeasures of correctly dealing with the relationship between agricultural development and the ecological restoration and reconstruction were proposed, including to get breakthrough first in the transection area by means of the rational use of resources and the raising of agro-system productivity, to promoting "water conservancy-type ecological agriculture" through the radical shift of traditional production pattern, and the adoption of a policy of proper degree of grain self-reliance, as well as to construct livestock industry base in Northwest China.

  13. Land degradation, government subsidy, and smallholders' conservation decision: the case of the loess plateau in China.

    Science.gov (United States)

    Shi, Min-Jun; Chen, Kevin

    2004-12-01

    Land degradation is one of the severe environmental problems in China. In order to combat land degradation, a soil conservation program was introduced since 2000 to reduce soil erosion by converting slope-cultivated land into forestry and pasture. This paper represents the first systematic attempt to investigate the impact of the soil conservation program on land degradation in the loess plateau. The results indicate that the soil conservation program to convert slope fields into forest or pasture is an effective way to combat soil erosion. However, a subsidy that is higher than profit of land use activity of slope fields before their conversion into forest and pasture is needed to encourage farmers to join the conservation program. A policy measure to encourage and assist farmers to develop sedentary livestock by using crops produced from fields as well as fodder and forage grass from the converted slope fields might contribute to combat soil erosion. Increase in off-farm job opportunities may encourage households to reduce cultivation in slope fields. That implies a policy measure to encourage rural urbanization might contribute to combat soil erosion. PMID:15547961

  14. Study on Maize-water Model for Supplemental Irrigation in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Xing LI; Mangmang GOU

    2015-01-01

    The Loess Plateau has a typical semi-arid climate, and the area suffers from very harsh ecological environment, severe soil erosion and water runoff, and uneven distributed precipitation. Due to the relatively low holding capacity, current rainwater-col ecting and conservation facilities can only supplement a maximum of 18 mm of water for crop production in each irrigation. In this study, mathematical models were constructed to identify the water requirement critical period of maize crop by evaluating response of each individual developmental stage to supplemen-tal irrigation with harvested rainwater. In the transformed Jensen model, ETmin/Eta was used as the index of relative evapotranspiration. The use of relative yield and relative crop evapotranspiration was able to eliminate influences from unintended en-vironmental factors. A BP neural network crop-water model for extreme water deficit condition was constructed using the index of relative evapotranspiration as the input and the index of relative yield as the output after iterative training and adjustment of weight values. Comparison of measured maize yields to those predicted by the two models confirmed that the BP neural network crop-water model is more accu-rate than the transformed Jensen model in predicting the sensitivity index to water-deficit at various growth stages and maize yield when provided with supplemen-tal irrigation with harvested rainwater.

  15. Spatial Variability of Soil Organic Carbon in a Watershed on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    WANG Yun-Qiang; ZHANG Xing-Chang; ZHANG Jing-Li; LI Shun-Ji

    2009-01-01

    Soil organic carbon (SOC) has great impacts on global warming,land degradation and food security.Classic statistical and geostatistical methods were used to characterize and compare the spatial heterogeneity of SOC and related factors,such as topography,soil type and land use,in the Liudaogou watershed on the Loess Plateau of North China.SOC concentrations followed a log-normal distribution with an arithmetic and geometric means of 23.4 and 21.3 g kg-1,respectively,were moderately variable (CV=75.9%),and demonstrated a moderate spatial dependence according to the nugget ratio (34.7%).The experimental variogram of SOC was best-fitted by a spherical model,after the spatial outliers had been detected and subsequently eliminated.Lower SOC concentrations were associated with higher elevations.Warp soils and farmland had the highest SOC concentrations,while aeolian sand soil and shrublands had the lowest SOC values.The geostatistical characteristics of SOC for the different soil and land use types were different.These patterns were closely related to the spatial structure of topography,and soil and land use types.

  16. A study of scale effect on specific sediment yield in the Loess Plateau,China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on data from 148 hydrometric stations in the Yellow River Basin, an analysis of regional scale relationship, or the relationship between specific sediment yield and drainage basin area, has been undertaken in the study area of the Loess Plateau. For different regions, scale relationship in log-log ordinate can be fitted by two types of lines: straight and parabola, and for each line, a function was fitted using regression analysis. The different scale relationships have been explained in terms of the difference in surface material distribution and landforms. To offset the scale-induced influence, calcu-lation has been done based on the fitted functions, in order to adjust the data of specific sediment yield to a common standard area. Based on the scaled data, a map of specific sediment yield was con-structed using Kriging interpolation. For comparison, a map based on the un-scaled data of specific sediment yield was also constructed using the same method. The two maps show that the basic pattern of specific sediment yield was basically the same. The severely eroded areas (Ys >10000 t km-2a-1) were at the same locations from Hekouzhen to Longmen in the middle Yellow River Basin. However, after the adjustment to a common standard area, the very severely eroded area (Ys >20000 t km-2a-1) became much enlarged because after the adjustment, all the values of Ys in the lower river basin in those regions became much larger than before.

  17. Soil erosion and sediment transport in the gullied Loess Plateau: Scale effects and their mechanisms

    Institute of Scientific and Technical Information of China (English)

    LI TieJian; WANG GuangQian; XUE Hai; WANG Kai

    2009-01-01

    Scale effects exist in the whole process of rainfall--runoff--soil erosion--sediment transport in river basins. The differences of hydrographa and sediment graphs in different positions in a river basin are treated as basic scale effects, which are more complex in the gullied Loess Plateau, a region notorious for high intensity soil erosion and hyper-concentrated sediment-laden flow. The up-scaling method of direct extrapolation that maintains dynamical mechanism effective in large scale application was cho-sen as the methodology of this paper. Firstly, scale effects of hydrographa and sediment graphs were analyzed by using field data, and key sub-processes and their mechanisms contributing to scale effects were clearly defined. Then, the Digital Yellow River Model that integrates sub-models for the sub-processes was used with high resolution to simulate rainfall--runoff--soil erosion--sediment transport response in Chabagou watershed, and the distributed results representing scale effects were obtained.Finally, analysis on the simulation results was carried out. It was shown that gravitational erosion and hyper-concentrated flow contribute most to the spatial variation of hydrographs and sediment graphs in the spatial scale. Different spatial scale distributions and superposition of different sub-processes are the mechanisms of scale effects.

  18. A study of scale effect on specific sediment yield in the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    YAN YunXia; XU JiongXin

    2007-01-01

    Based on data from 148 hydrometric stations in the Yellow River Basin, an analysis of regional scale relationship, or the relationship between specific sediment yield and drainage basin area, has been undertaken in the study area of the Loess Plateau. For different regions, scale relationship in log-log ordinate can be fitted by two types of lines: straight and parabola, and for each line, a function was fitted using regression analysis. The different scale relationships have been explained in terms of the difference in surface material distribution and landforms. To offset the scale-induced influence, calculation has been done based on the fitted functions, in order to adjust the data of specific sediment yield to a common standard area. Based on the scaled data, a map of specific sediment yield was constructed using Kriging interpolation. For comparison, a map based on the un-scaled data of specific sediment yield was also constructed using the same method. The two maps show that the basic pattern of specific sediment yield was basically the same. The severely eroded areas (Ys >10000 t km-2a-1) were at the same locations from Hekouzhen to Longmen in the middle Yellow River Basin. However, after the adjustment to a common standard area, the very severely eroded area (Ys >20000 t km-2a-1) became much enlarged because after the adjustment, all the values of Ys in the lower river basin in those regions became much larger than before.

  19. [Characteristics of seed rain on abandoned slopes in the hilly-gullied Loess Plateau, Northwest China].

    Science.gov (United States)

    Yu, Wei-jie; Chen, Yu; Jiao, Ju-ying; Wang, Dong-li; Wang, Zhi-jie; Wei, Yan-hong; Kou, Meng; Yin, Qiu-long

    2015-02-01

    The objective of this study was to analyze the dynamic characteristics of seed rain on abandoned slopes in the hilly-gullied Loess Plateau region and identify the relationship between seed rain and standing vegetation. Three abandoned slopes were chosen as sampling sites in Zhifanggou watershed. Thirty traps were installed at each site to collect seed rain from October 2010 to April 2013. Standing vegetation was surveyed to identify dominant species in August 2011 and 2012, respectively. Thirty-seven species belonging to seventeen families were identified in the seed rain, and the dominant species, i.e., Lespedeza davurica, Astragalus scaberrimus, Setaria viridis, Cleistogenes squarrosa, Stipa bungeana, Bothriochloa ischcemum, Artemisia scoparia, A. gmelinii, and Heteropappus altaicus, took up to 95.8% of the total seed rain. Three species in seed rain were not found in the standing vegetation. The Sorensen similarity index between seed rain and standing vegetation was 0.77. Seed rain densities were 3737 and 6449 seeds · m(-2) in May 2011-April 2012 and May 2012-April 2013, respectively, and alternate bearing existed. During the study period, seed rain from different positions varied from 3853 to 37923 seeds · m(-2) and belonged to 7-15 species. The results indicated the space limitation of seed dispersal. Seed rain densities were in the middle of the pack compared with similar ecosystems in other studies. High temporal and spatial heterogeneity of seed rain was observed because of rainfall, microtopography and so on. PMID:26094452

  20. Estimating Loess Plateau Average Annual Precipitation with Multiple Linear Regression Kriging and Geographically Weighted Regression Kriging

    Directory of Open Access Journals (Sweden)

    Qiutong Jin

    2016-06-01

    Full Text Available Estimating the spatial distribution of precipitation is an important and challenging task in hydrology, climatology, ecology, and environmental science. In order to generate a highly accurate distribution map of average annual precipitation for the Loess Plateau in China, multiple linear regression Kriging (MLRK and geographically weighted regression Kriging (GWRK methods were employed using precipitation data from the period 1980–2010 from 435 meteorological stations. The predictors in regression Kriging were selected by stepwise regression analysis from many auxiliary environmental factors, such as elevation (DEM, normalized difference vegetation index (NDVI, solar radiation, slope, and aspect. All predictor distribution maps had a 500 m spatial resolution. Validation precipitation data from 130 hydrometeorological stations were used to assess the prediction accuracies of the MLRK and GWRK approaches. Results showed that both prediction maps with a 500 m spatial resolution interpolated by MLRK and GWRK had a high accuracy and captured detailed spatial distribution data; however, MLRK produced a lower prediction error and a higher variance explanation than GWRK, although the differences were small, in contrast to conclusions from similar studies.

  1. Orbital forcing of the East Asian summer monsoon based on quantitative paleorainfall records from Chinese Loess using 10Be

    Science.gov (United States)

    Beck, W.; White, L.; Cheng, L.; Wu, Z.; zhou, W.; Kong, X.

    2013-12-01

    Here we outline a method for deriving quantitative records of paleoprecipitation using meteoric 10Be flux as recorded in Quaternary loess sediments, and apply this method to derive a ~500ka rainfall record from Chinese loess. The method involves measuring loess 10Be concentration by AMS, then applying corrections for radioactive decay, recycled 10Be in reaerosolized dust, and for variations in geomagnetic field to correct for atmospheric 10Be production rate variations. 10Be flux is calculated by multiplying the corrected 10Be concentrations with loess accumulation rate, where the later is derived from a (non-orbitally tuned) timescale determined from correlating variations in loess magnetic susceptibility with U/Th dated Chinese speleothem δ18O records. The dependence of 10Be flux on rainfall rate is determined using modern observations of 7Be flux in rainfall, and atmospheric 10Be/7Be cosmogenic nuclide production ratios. Modern rainfall on the Chinese Loess Plateau has been shown to be primarily a function of East Asian Summer Monsoon (EASM) intensity. Our 10Be rainfall proxy shows that glacial to peak interglacial rainfall rates in this region have varied by about a factor of two over the last 0.5 Ma. Our results suggests EASM intensity during interglacials MIS11, MIS 9c and MIS13 were all comparable (~850 mm/yr), but slightly less (by ~8%) than for MIS1, and about 15% less than for MIS5e, which is similar to the high latitude ice volume pattern of response except for MIS11. We note that the 10Be rainfall record of MIS13 differs from typical Chinese loess magnetic susceptibility records that suggest MIS13 was the strongest EASM of the last 6 interglacials. Our record instead indicates a relative subdued MIS13 EASM, more consistent with the Antarctic EPICA ice core deuterium or marine δ18O records. We correlate our results with orbital forced solar insolation variations at high and low latitudes as well as with interhemispheric insolation gradients. We find

  2. Loess in Kunlun Mountains and its implications on desert development and Tibetan Plateau uplift in west China

    Institute of Scientific and Technical Information of China (English)

    FANG; Xiaomin(方小敏); Lü; Lianqing(吕连清); YANG; Shengli(杨胜利); LI; Jijun(李吉均); AN; Zhisheng(安芷生); JIANG; Pingan(蒋平安); CHEN; Xiuling(陈秀玲)

    2002-01-01

    Loess on the northern slope of Kunlun Mountains is the synchronous deposition of the Taklimakan Desert. The paleomagnetism and climatic records of an over 80 m loess-paleosol sequence on the highest river terrace at the foot of Kunlun Mountains show that the loess formed at ~ 880 ka B.P., suggesting a roughly synchronous occurrence of the present-like air circulation and extremely dry climate and the initial desert. The uplift of the Tibetan-Pamir Plateau and Tian-shan Mountains may initiate these events. The rise of the plateau and adjacent mountains caused the drying and desertification of China inland and Tarim Basin, which was dramatically enhanced at ~ 500 ka B.P., leading the desert to expand to its present scale. Global change just overprints this drying trend. Local climate response to global change both in long-term evolution and glacial-interglacial cycles manifests that the stronger the westerlies, the more the precipitation. But the heat-moisture pattern seems still similar to that in the Asian monsoon region.

  3. Dried earth layers of artificial forestland in the Loess Plateau of Shaanxi Province%陕西黄土高原人工林土壤干层及形成原因

    Institute of Scientific and Technical Information of China (English)

    赵景波; 杜娟; 陈宝群

    2007-01-01

    By determining the earth moisture content of artificial forestland between 0 and 6 m deep in the Loess Plateau of Shaanxi province, the vertical change of moisture content,distribution and formation causes of a dried earth layer are researched. The results show that the average moisture content is 9.3%-9.5% between 2 and 4 m under artificial forest of over 10 year's growth in Guanzhong Plain, and chronic weak dried earth layers are developed which show that the dried earth layers are distributed extensively on the Loess Plateau. The southern boundary of the dried earth layer has reached the northern foot of the Qinling Mountains. When precipitation reaches 600 mm, there are weak dried earth layers between 2 and 4 m under artificial forest of more than 10 years old. When the precipitation is between 400 and 500 mm, there are moderate dried earth layers. When precipitation is above 800 mm,there are no dried earth layers. There are no dried earth layers under meadow land, corn land and less than 5 years old of artificial forestland in central and southern parts of the Loess Plateau. The development of dried earth layers under cypress forest is weaker than broad-leaved forest. Under the same climatic conditions, the development of dried earth layers under the loess tableland is nearly at the same level as the 2nd and 3rd river terrace.Dried earth layers developed in membrane water zone, and the buried depth is small and motion velocity is slow in the Loess Plateau, which is the direct water factor of the formation of the dried earth layer, while differences of tree age and tree species are the plant factors that consumed much moisture. From the depth of the gravity water and the membrane water in Guanzhong Plain, it is clear that the formation cause of dried earth layers is mainly due to natural factors. The dried layers generally develop in middle-aged artificial forestland that consumed too much moisture, which is the general character of earth moisture in subhumid

  4. Effect of Fertilization on Soil Fertility and Wheat Yield of Dryland in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    HAO Ming-De; FAN Jun; WEI Xiao-Rong; PEN Lin-Fa; LAI Lu

    2005-01-01

    Long-term fertility experiments have become an important tool for investigating the sustainability of cropping systems.Therefore, a long-term (18-year) fertilization experiment was conducted in Changwu County, Shaanxi Province, China,to ascertain the effect of the long-term application of chemical fertilizers and manure on wheat yield and soil fertility in the Loess Plateau, so as to provide a scientific basis for sustainable land management. The experiment consisted of nine fertilizer treatments with three replicates arranged in a completely randomized design: 1) CK (no fertilizer); 2) N (N 120 kg ha-i); 3) P (P 26.2 kg ha-1); 4) NP (N 120, P 26.2 kg ha-1); 5) M (manure 75 t ha-1); 6) NM (N 120 kg ha-1,manure 75 t ha-1); 7) PM (P 26.2 kg ha-1, manure 75 t ha-1); 8) NPM (N 120, P 26.2 kg ha-1, manure 75 t ha-1);and 9) fallow (no fertilizer, no crop). N fertilizer was applied in the form of urea and P was applied as calcium super phosphate. The results showed that precipitation had a large effect on the response of wheat yield to fertilization. Manure (M), NP, PM, NM, and NPM treatments significantly increased (P < 0.05) average yield. In the NP, PM, NM and NPM treatments, the percentage increases in yield due to fertilization were highest in normal years, and lowest in the drought years. Long-term P application enhanced soil available P markedly, and manure applications contributed more to soil fertility than chemical fertilizers alone. Chemical fertilizers applied together with manure distinctly improved soil fertility.The results also showed that the soil nutrient concentration changed mainly in the 0-60 cm layers and fertilization and planting only slightly affected soil nutrients below the 100 cm layers.

  5. The Effect of Integrated Grasses in Controlling Soil, Nutrient and Organic Matter in Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    Honest Augustine Mosha

    2013-01-01

    Full Text Available Soil and nutrient loss is one of a serious problem in Loess plateau china. The eroded materials are directly transported to the lakes and rivers specifically yellow river in China, this might lead to eutrophication if no prevention measures will be taken. The experiment was conducted on soil, and nutrient loss from 5º slope. Individual grasses plots for rye grass(Lolium, white clover(Trifolium repens and integrated grass (rye + white clover plots were prepared with a percentage cover of 25, 50, 80 and 100 in each treatment. Bare land was used as a reference plot. The results show that, the sediment loss in a bare land reported to be 1.5, 3, 2.7 and 1.3, 2.1, 1.9 in 100 % and 80 % cover plots. The runoff rate as compared to bare land, shown to be about 2 times less for white clover and rye grass plots, while more than 2 times less for integrated grasses plots. The total nitrogen and organic matter loss the results were in the order bare land white clover rye grasses and integrated grasses in which 100 %, 80 % and 50 % vegetative cover shown to perform better. On average enrichment ratio range was 40 % to 90 % for nutrient loss, and 50 % to 85 % for organic matter for all plots in comparison with soil origin. The enrichment ration significantly shown to be high from bare land> rye and white clover plots> integrated grasses plot. It has been concluded that integrated grasses is more effective measure over others in controlling both soil, nutrient and organic matter loss in the soil. This study contributed some information on the erosion modeling and improvement of soil and grassland conservation techniques for better land use for sustainable development

  6. Prehistoric land use in southern Loess Plateau reconstructed from archeological data by a new developed model

    Science.gov (United States)

    Yu, Y.; Wu, H.; Guo, Z.

    2014-12-01

    Estimation of land use during the Holocene is crucial to understand impacts of human activity on climate change in preindustrial period. Until now it is still a key issue to reconstruct amount and spatial distribution of prehistoric land use due to lack of data. Most reconstructions are simply extrapolations of population, cleared land amount per person and land suitability for agriculture. In this study, a new quantitative prehistoric land use model (PLUM) is developed based on semi-quantitative predictive models of archeological sites. The PLUM is driven by environmental and social parameters of archeological sites, which are objective evidences of prehistoric human activity, and produces realistic patterns of land use. After successful validations of the model with modern observed data, the PLUM was applied to reconstruct land use from 8 to 4 ka B.P. in Yiluo and Wei valleys, southern Loess Plateau. Both of them are the most important agriculture origin centers in northern China. Results reveal that about 9% of land areas in both valleys have been used by human activity from 8 to 4 ka B.P., expanding from gentle slopes along the river to hinterlands of the valleys. The land cover was affected by increasing agricultural land use during the middle Holocene. The extensive spreads of land use since 7 ka B.P. in both valleys were driven by the combined impacts of population increase and agriculture development, which was further favored by wet and warm climate conditions during middle Holocene; while the decreasing rates of land use expansions after 5 ka B.P. were mainly induced by improved agriculture technology. With the scaling up of PLUM to larger regional or global levels by a greater use of archeological data, the impact of human land use on global change can be studied more accurately.

  7. Effect of apple production base on regional water cycle in Weibei upland of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Weibei upland, located in southern part of the Loess Plateau, is a commercial apple production base in China. The enlargement of apple-planting area has a great impact on the regional water cycle. The effects of different land use on hydrological parameters are compared and studied in this paper. The main results are as follows: (1) The initial and steady infiltration rates in apple orchard are higher than those in other land use types such as grassland, idle land and farmland. Their initial rates of infiltration are 0.823 cm/min, 0.215 cm/min, 0.534 cm/min and 0.586 cm/min in apple orchard, grassland, idle land and farmland respectively. Their steady infiltration rates are 0.45 cm/min, 0.038 cm/min, 0.191 cm/min and 0.155 cm/min respectively. (2) There is no runoff generated in plot of apple orchard in all 8 storm events in observed natural rainfalls, while runoff is generated in winter wheat plot, com plot and alfalfa plot with runoff coefficients of 2.39%, 1.58% and 0.31% respectively. (3) The transpiration of apple trees is strong and thus soil moisture is gradually depleted. The average soil water contents in 3-9 m soil profile in Changwu plots with apple trees of 14 and 32 years in age are 11.77% and 11.59% and in Luochuan plots with those of 15 and 28 years in age are 11.7% and 11.59% respectively, which are nearly 9.0% of wilting moisture of Changwu soil and 8.6% of wilting moisture of Luochuan soil. The pathway of rainfall percolating to groundwater is hindered by dry soil profile.

  8. Soil moisture and evapotranspiration of different land cover types in the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    S. Wang

    2012-08-01

    Full Text Available We studied the impacts of re-vegetation on soil moisture dynamics and evapotranspiration (ET of five land cover types in the Loess Plateau in northern China. Soil moisture and temperature variations under grass (Andropogon, subshrub (Artemisia scoparia, shrub (Spiraea pubescens, plantation forest (Robinia pseudoacacia, and crop (Zea mays vegetation were continuously monitored during the growing season of 2011. There were more than 10 soil moisture pulses during the period of data collection. Surface soil moisture of all of the land cover types showed an increasing trend in the rainy season. Soil moisture under the corn crop was consistently higher than the other surfaces. Grass and subshrubs showed an intermediate moisture level. Grass had slightly higher readings than those of subshrub most of the time. Shrubs and plantation forests were characterized by lower soil moisture readings, with the shrub levels consistently being slightly higher than those of the forests. Despite the greater post-rainfall loss of moisture under subshrub and grass vegetation than forests and shrubs, subshrub and grass sites exhibit a higher soil moisture content due to their greater soil retention capacity in the dry period. The daily ET trends of the forests and shrub sites were similar and were more stable than those of the other types. Soils under subshrubs acquired and retained soil moisture resources more efficiently than the other cover types, with a competitive advantage in the long term, representing an adaptive vegetation type in the study watershed. The interactions between vegetation and soil moisture dynamics contribute to structure and function of the ecosystems studied.

  9. Relationship between seedling and mature vegetation on the hilly-gullied Loess Plateau.

    Science.gov (United States)

    Jia, Yan-Feng; Jiao, Ju-Ying; Wang, Ning

    2013-01-01

    Seedling is an indispensable stage in plant cycle life, and seedling survival is important during natural vegetation restoration, especially on the Loess Plateau. In 2007, we selected 4 plots of Artemisia scoparia communities (ASC) and 4 plots of Artemisia gmelinii + Artemisia giraldii communities (AGC), examined seedling richness, diversity during the rainy season, and examined mature vegetation richness, coverage, and frequency in August. The results showed that seedlings density of ASC were 29 n m(-2), 33 n m(-2), 20 n m(-2) and 31 n m(-2) in July to October respectively, and that of AGC were 14 n m(-2), 12 n m(-2), 6 n m(-2) and 9 n m(-2) respectively; A. scoparia seedlings represented 53.2% of the total seedlings in ASC, the dominant species in AGC only account for less than 5% of the total seedlings. Most of the seedlings found were belonged to Compositae, Leguminoseae and Gramineae; 80% of seedlings in ASC were mainly comprised of A. scoparia and Lespedeza davurica, while in AGC that consisted of more than 6 species, such as L. davurica, Sophora viciifolia, Dracocephalum moldavicaand, A. gmelinii, Patrinia heterophylla, Heteropappus altaicus so on. Sørensen similarity index between monthly seedlings was approximately 0.47 in ASC and 0.35 in AGC; Sørensen similarity index between seedlings and mature vegetation ranged from 0.18 to 0.34 in ASC, and varied from 0.26 to 0.39 in AGC. These results suggested that seedling establishment would be a bottleneck for natural vegetation restoration when seed supply and seedling emergence were possible. PMID:24701385

  10. Rapid changes of soil properties following Caragana korshinski plantations in the hilly-gully Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    AN Shaoshan; HUANG Yimei

    2006-01-01

    In the semi-arid area of the Loess Plateau,Caragana korshinski,a leguminous shrub,is the dominant plant species widely used in vegetation rehabilitation programs.We collected soil samples in 8- and 18-year-old C.korshinski plantations to assess the effects of the shrub on the physical and chemical properties of the soil as well as enzyme activities.Soil samples were taken from two depths (0-20 and 20-40 cm) under the shrub canopy between shrubs.Results showed that shrub rehabilitation and development enhanced accumulation of organic C and total N.Carbon and nitrogen concentrations increased significantly with plantation age and had increased by 15.3-20.5-fold and 11.1-13.6-fold at 0-20 cm depth at the 18-year-old plantation compared with farmland soil.It was found that C.korshinski contributed significant enrichment of C and N contents under their canopies compared with farmland.The content of water stable aggregates in 18-year-old shrub land soil is higher than the 8-year-old shrub land,and the big aggregates (>5 mm) increased for the most part,by 67.4% and 59.0% in different layers,respectively.The contents of aggregates of over 0.25 mm in two shrub land soils in the upper layer (0-20 cm) increased by 4.6% and 14.1% compared with farmland.It indicates that C.korshinski afforestation can increase the content of aggregates.C.korshinski plantation can accelerate the increase of soil urea activity and invertase activity,respectively,especially in the upper layer.

  11. Yield responses of wheat to mulching practices in dryland farming on the Loess Plateau.

    Directory of Open Access Journals (Sweden)

    Li-fang Wang

    Full Text Available Improving farming practices of soil and water conservation has profound effects on the yield of wheat (Triticum aestivum L. in dryland farming regions of the Loess Plateau in China. Mulching has proven to be an effective practice to increase crop yield, and possibly contribute to replenishing groundwater. This evaluation study collected and analyzed the data of 1849 observations published in 38 papers using meta-analysis to investigate effects of the mulching practices on wheat yield in terms of different rainfall and regions in comparison with conventional tillage. The main results of the study follow. The effects of the mulching practices were ranked in the order of RFM (ridge-furrow mulching > MTMC (mulching with two materials combined > MOM (mulching with other materials > WSM (wheat straw mulching > FM (flat mulching. The effects of the mulching practices at the different levels of rainfall during the wheat growing season were in the order: ( (> 250 mm > (150-250 mm. The effects of the mulching practices in the different regions were in the order of Henan > Shanxi > Shaanxi > Gansu. WSM, MTMC and FM performed better in improving wheat yield for rainfall of 250 mm during the growing season, respectively. The wheat yield with FM, MTMC, MOM and MOM was higher than those with the other mulching practices in Shaanxi, Gansu, Henan and Shanxi. The wheat yield with RFM was 27.4% higher than that with FM, indicating that RFM was the most effective practice to improve wheat yield among all the practices. These findings have important implications for choosing appropriate crop field management to improve wheat yield.

  12. Study on constructive system of green cave dwelling in Loess Plateau-Interpretation with the "regional gene" theory

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This article reveals the inherent evolution adjusting mechanism of regional architecture by means of considering the concept and method of "regional gene" as the research approach of regional architecture construction system, and in the meanwhile establishes the "gene database" of regional architecture and optimum technology, on the basis of the principle of sustainable development and scientific evaluation system. In addition, this article chooses the planning of model villages of cave dwellings in Loess Plateau and the construction of ecological cave dwellings for case study to prove the feasibility of the research approach.

  13. Study on Rural Domestic Waste Treatment in Loess Plateau Region——Taking Longfang Town in Shaanxi Province as Example

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    With the continuous development of economy and changes in people's lifestyle,rural domestic waste brought about serious harm to water,air,human health,ecological landscape and so forth.In this paper,taking Longfang Town in Loess Plateau region as example,the source,amount and harms of rural domestic waste were analyzed firstly,as well as the current situation and existing problems of treatment,and then a suitable waste disposal technology for the town was chosen,finally the reasonable treatment methods comb...

  14. Nitrogen isotopic composition of plant-soil in the Loess Plateau and its responding to environmental chanse

    Institute of Scientific and Technical Information of China (English)

    LIU WeiGuo; WANG Zheng

    2009-01-01

    The nitrogen isotope of soil is of emerging significance as an indicator of climatic change and bio-geochemical cycle of nitrogen in nature systems. In this paper, the nitrogen content and isotopic composition of modern ecosystems from arid and semiarid Loess Plateau in northwestern China, in-cluding plant roots and surface soil, were determined to investigate trends in δ15N variation of plant roots and soil along a precipitation and temperature gradient in northwestern China under the East Asian Monsoon climate condition. The δ15N values of surface soil from the study area vary from -1.2‰to 5.8‰, but from -5.1‰ to 1.9‰ in the plant roots. Our results indicate that (1) although the isotopic compositions of both plant roots and surface soil change with a similar trend along the climate gradient,the apparent nitrogen difference between plant roots and soil existed, with △δ15N values ranging from 0.3‰ to 7.2‰ with average of 4.1‰; and (2) mean annual precipitation (MAP) is the dominant factor for isotopic composition of plant-soil nitrogen in the Loess Plateau, and the δ15.N values are less correlated with MAT; we suggest that nitrogen isotopic composition of soil is a potential tracer for environmental changes.

  15. GIS-Based Synthetic Measurement of Sustainable Development in Loess Plateau Ecologically Fragile Area—Case of Qingyang, China

    Directory of Open Access Journals (Sweden)

    Chenyu Lu

    2015-02-01

    Full Text Available Synthetic measurement of regional sustainable development has been one of the key issues in the research field of sustainability. In this paper, Qingyang City located in the Loess Plateau ecologically fragile area of Northwest China is used for a case study, and the present study aims to investigate the degree of sustainable development by conducting temporal- and spatial-scale based analysis, with the assessment index system, assessment model and GIS approach well integrated. The results show that the development pattern of Qingyang generally fits the mode of unsustainable development, even in the presence of certain levels of spatial differences. The sustainable development state in ecologically fragile area of China’s Loess Plateau is non-optimistic, which is an uncoordinated status among subsystems of regional sustainable development. Although the level and tendency of regional sustainable development keeps increasing, such enhancement is abnormal. With the rapid deterioration of environmental and natural resources, their inhibitory effect on the economy and society would expand, eventually leading to the slow development rate or the recession of the entire system. The only solution is to change the traditional mode of economic development, to follow the guide of ecological economic conception so that the goal of achieving regional sustainable development strategies could be met ultimately. Meanwhile, the characteristics of different regions should be taken into account in order to achieve optimal spatial structure.

  16. Fractal features of soil particle size distribution in layered sediments behind two check dams: Implications for the Loess Plateau, China

    Science.gov (United States)

    Wei, Xia; Li, Xungui; Wei, Ning

    2016-08-01

    The layered sediment deposited behind a check dam can provide useful information about soil erosion processes in the dam-controlled area. This study aims to evaluate the possible fractal nature of layered sediments behind check dams, assessing whether fractal dimension can serve as a feasible index for evaluating the impact of land use types on the area controlled by the check dam. Fractal dimension measurement was employed to analyze the features of soil particle size distribution (PSD) for different layered sediments of the Shipanmao and Zhangshan check dams in the Dalihe River Basin of the Loess Plateau, China. Results show that the predominant soil particle sizes of the sediment layers behind the Shipanmao and Zhangshan dams are silt-clay (land use changes between 1972 and 1979 for the dam-controlled area of the Shipanmao dam. The total increment of C during 1972-1979 was 0.021 and the soil erosion amount per rainfall erosivity was smaller in 1972 than in 1979, indicating desertification in the dam-controlled area. In addition, the land use types prevalent in 1979 were more prone to soil loss than those in 1972. Dm is a useful parameter to assess land use types and soil degradation processes in dam-controlled areas of the Loess Plateau.

  17. Human-Induced Landcover Changes Drive a Diminution of Land Surface Albedo in the Loess Plateau (China

    Directory of Open Access Journals (Sweden)

    Jun Zhai

    2015-03-01

    Full Text Available A large decrease in the land surface albedo of the Loess Plateau was observed from 2000 to 2010, as measured using satellite imagery. In particular, ecological restoration program regions experienced a decrease in peak season land surface albedo exceeding 0.05. In this study, we examined the spatial and temporal patterns of variation during the peak season albedo in the Loess Plateau and analyzed its relationships with changes of anthropogenic and natural factors at the pixel level. Our analysis revealed that increasing grassland coverage due to returning rangeland to grassland could lead to a maximum albedo decrease of 0.030 in peak season. This result highlighted the human-induced land use change in driving the decreasing albedo on an annual scale. There was no significant correlation between precipitation change and albedo reduction. Precipitation could influence the spatial pattern of albedo in drought years by influencing the natural vegetation water requirement. However, the role of precipitation was not obvious in the ecological restoration program regions. This article demonstrates the substantial role that land use change could play in regional-scale albedo change and climate. Finally, some implications for the radiative forcing of land use change are discussed.

  18. Impact of gully on soil moisture of shrubland in wind-water erosion crisscross region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    HUO Zhu; SHAO Ming-An; LISI

    2008-01-01

    The most serious erosion on the Loess Plateau of China exists in the wind-water erosion crisscross region where the annual precipitation is about 400 ram,the ecological environment is very fragile,and water is the key limiting factor for improving the environment.In this study,changes of soil moisture content for Caragana korshinskii Kom.shrubland in the gully bank of the Loess Plateau were studied using the methods of soil sampling and neutron probe.A typical gully (75 m long,28 m wide,and 10 m deep) was selected,and six neutron probe access tubes (6 m long) were installed at points 50,100,200,300,400,and 500 cm from the gully border for obtaining soil moisture data from July to October 2004 at approximately 10 d intervals.Soil samplings were simultaneously carried out for moisture determination at the six points.Results showed that the soil moisture of the shrubland in the gully bank significantly varied between 300 and 400 cm in the horizontal direction and up to 600 cm in vertical direction of the gully.Seasonal changes in soil moisture revealed a curve with a single peak that occurred at the end of August or early September.A linear regression equation was fit for soil water storage and the distance from the gully border,with coefficients depending on rainfall characteristics,sampling point,and time of measurement.

  19. Spatial patterns and stability of soil water content in forested slope and terraced area on the Loess Plateau, China

    Science.gov (United States)

    Xu, Guoce; Li, Zhanbin; Li, Peng

    2016-04-01

    Soil water content (SWC) plays a vital role in hydrological and vegetation restoration processes. It is the principal limiting factor for vegetation restoration on the Loess Plateau of China. This study aimed to analyze the spatial patterns and stability of SWC in a terraced area containing jujube trees (Ziziphus jujuba Mill.) and a forested slope with Chinese pine (Pinus tabulaeformis Carr.) following rainfall. The SWCs in nine soil layers at intervals of 0.2 m down to a depth of 1.8 m were measured at 21 locations both in the terraces and in the forested slope from July 19 to September 3 in 2014. The results showed that the SWCs at different soil depths were normally distributed. The SWC in terraces and forestland at each soil depth all had strong temporal stability. The temporal stability of SWC was lower in the 0-0.4 m soil layer than at the deeper soil depths. The representative locations for SWC were depth-dependent and the number of representative locations was not constant. The mean SWC was largest in the lower terrace slopes. The lowest mean SWC in the forested slope was at the mid-slope point due to the highest root distribution. The 0.4-0.6 m soil depth was generally the wettest in both terraces and forestland. The driest soil depth in terraces was 1.0-1.2 m while the driest soil depth in forestland was 0.8-1.0 m. The SWC had a significant positive correlation with clay and silt content. Moerover, the SWC had a significant positive correlation with SOC and did not have a significant correlation with root conten in the terraced area. But in the forested slope, the SWC had a significant negative correlation with roots and did not have a significant correlation with SOC. Although it is feasible to use the representative locations of SWC to represent the mean SWC of a hillslope over a period of time, the cumulative absolute error increases with the cumulative number of days. In conclusion, the SWC at different soil depths and locations showed strong spatial

  20. Comparison of different landform classification methods for digital landform and soil mapping of the Iranian loess plateau

    Science.gov (United States)

    Hoffmeister, Dirk; Kramm, Tanja; Curdt, Constanze; Maleki, Sedigheh; Khormali, Farhad; Kehl, Martin

    2016-04-01

    The Iranian loess plateau is covered by loess deposits, up to 70 m thick. Tectonic uplift triggered deep erosion and valley incision into the loess and underlying marine deposits. Soil development strongly relates to the aspect of these incised slopes, because on northern slopes vegetation protects the soil surface against erosion and facilitates formation and preservation of a Cambisol, whereas on south-facing slopes soils were probably eroded and weakly developed Entisols formed. While the whole area is intensively stocked with sheep and goat, rain-fed cropping of winter wheat is practiced on the valley floors. Most time of the year, the soil surface is unprotected against rainfall, which is one of the factors promoting soil erosion and serious flooding. However, little information is available on soil distribution, plant cover and the geomorphological evolution of the plateau, as well as on potentials and problems in land use. Thus, digital landform and soil mapping is needed. As a requirement of digital landform and soil mapping, four different landform classification methods were compared and evaluated. These geomorphometric classifications were run on two different scales. On the whole area an ASTER GDEM and SRTM dataset (30 m pixel resolution) was used. Likewise, two high-resolution digital elevation models were derived from Pléiades satellite stereo-imagery (58%. For the 30 m resolution datasets is the achieved accuracy approximately 40%, as several small scale features are not recognizable in this resolution. Thus, for an accurate differentiation between different important landform types, high-resolution datasets are necessary for this strongly shaped area. One major problem of this approach are the different classes derived by each method and the various class annotations. The result of this evaluation will be regarded for the derivation of landform and soil maps.

  1. Geomagnetic field intensity and quantitative paleorainfall reconstruction from Chinese loess using 10Be and magnetic susceptibility

    Science.gov (United States)

    Beck, W.; zhou, W.; Li, C.; Wu, Z.; White, L.; Xian, F.

    2011-12-01

    7Be is produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols, usually encapsulated in rain or snow. Numerous studies have shown that its flux to the ground is proportional to rainfall amount. Unfortunately, with a half life of only a few weeks, this observation has little relevance for reconstruction past rainfall amounts in paleosoils. Fortunately, 7Be has a long-lived sister isotope (10Be) with a half life of ~1.5 Ma which can be used for such purposes. There are a number of complications, however. First, 10Be atmospheric production rate changes when the geomagnetic field intensity changes. Secondly, 10Be half life is long enough that 10Be which fell to the ground attached to dust some time in the past can become resuspended, meaning that there are two sources of 10Be, one meteoric, and the other recycled aeolian dust. Fortunately, we have found a method to deconvolute this knotty situation and have applied it to soils of the Chinese Loess Plateau, allowing us to reconstruct records of both geomagnetic field intensity and paleorainfall. To do so, we use the additional parameters magnetic susceptibility and coercivity to help define the inherited amount of each component, and to define what fraction of the variations in 10Be are associated with magnetic field fluctuations, versus that linked to rainfall variations. We also use a sediment age/depth model to convert 10Be concentration to 10Be flux, and finally, we use the modern 7Be vs. rainfall relationship and 10Be/7Be atmospheric production rate ratio to calculate quantitative paleorainfall rates. We have used these techniques to generate several such records ranging from the Holocene to MIS13 (Circa 525 ka BP), and will compare some of these to U-series dated speleothem records of δ18O.

  2. Spatiotemporal analysis of multiscalar drought characteristics across the Loess Plateau of China

    Science.gov (United States)

    Liu, Zhipeng; Wang, Yunqiang; Shao, Mingan; Jia, Xiaoxu; Li, Xuelin

    2016-03-01

    Drought is the most widespread and destructive hazard in arid and semiarid regions, with behaviors that become more complicated under climate change. To provide an overall view of drought conditions across the Loess Plateau of China, two multiscalar drought indices, the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), were used to identify the regional spatiotemporal characteristics of drought conditions from 1957 to 2012. Climatic data from 54 meteorological stations across the region were used to calculate the SPI and SPEI time series at 1-, 3-, 6-, 12- and 24-month time scales. Subregions with independent drought characteristics and the corresponding representative meteorological stations were identified by principal component analysis to facilitate regional drought monitoring. A temporal trend of drought severity over a 12-month time scale, as detected by the Mann-Kendall test, was mapped for the entire region. The intensity of the increasing trend of drought severity based on the SPEI was weaker than that based on the SPI. The area with a significant increasing trend of drought severity based on the SPEI was only found in the southwest of the region and was much smaller than that based on the SPI. The temporal behavior of drought frequency from January to December differed over different time scales and levels of drought severity. The regional distributions of the drought frequency were mapped for different months. Generally, the drought frequency spatially decreased from southeast to northwest and was higher in the middle of the winter, late spring and early summer. While the drought-hit area also changed with time, it was generally within the central and northwest areas of the region. Drought behaviors identified by the SPI and SPEI also changed with different time scales. Clear differences were also found among the drought characteristics identified by SPI, SPEI and the self-calibrated Palmer Drought

  3. Soil organic carbon dynamics following afforestation in the Loess Plateau of China

    Directory of Open Access Journals (Sweden)

    N. Lu

    2013-07-01

    Full Text Available Soil organic carbon (SOC is the largest terrestrial carbon pool and sensitive to land use and cover change; its dynamics is critical for carbon cycling in terrestrial ecosystems and the atmosphere. In this study, we combined a modeling approach and field measurements to examine the temporal dynamics of SOC following afforestation of former arable land at six sites under different climatic conditions in the Loess Plateau during 1980–2010. The results showed that the measured mean SOC increased to levels higher than before afforestation when taking the last measurements (i.e., at age 25 to 30 yr, although it decreased in the first few years at the wetter sites. The accumulation rates of SOC were 1.58 to 6.22% yr–1 in the upper 20 cm and 1.62 to 5.15% yr–1 in the upper 40 cm of soil. The simulations reproduced the basic characteristics of measured SOC dynamics, suggesting that litter input and climatic factors (temperature and precipitation were the major causes for SOC dynamics and the differences among the sites. They explained 88–96, 48–86 and 57–74% of the variations in annual SOC changes at the soil depths of 0–20, 0–40, and 0–100 cm, respectively. Notably, the simulated SOC decreased during the first few years at all the sites, although the magnitudes of decreases were small at the drier sites. This suggested that the modeling may be advantageous in capturing SOC changes at finer time scale. The discrepancy between the simulation and measurement was a result of uncertainties in model structure, data input, and sampling design. Our findings indicated that afforestation promoted soil carbon sequestration at the study sites, which is favorable for further restoration of the vegetation and environment. Afforestation activities should decrease soil disturbances to reduce carbon release in the early stage. The long-term strategy for carbon fixation capability of the plantations should also consider the climate and site conditions

  4. Ectomycorrhizal fungal communities associated with Populus simonii and Pinus tabuliformis in the hilly-gully region of the Loess Plateau, China

    Science.gov (United States)

    Long, Dongfeng; Liu, Jianjun; Han, Qisheng; Wang, Xiaobing; Huang, Jian

    2016-01-01

    The Loess Plateau region of northwestern China has unique geological and dry/semi-dry climate characteristics. However, knowledge about ectomycorrhizal fungal (EMF) communities in the Loess Plateau is limited. In this study, we investigated EMF communities in Populus simonii and Pinus tabuliformis patches within the forest-steppe zone, in pine forests within the forest zone, and the transitional zone between them. We revealed high species richness (115 operational taxonomic units [OTUs]) of indigenous EMF resources at the Loess Plateau, of which Tomentella (35 OTUs), Inocybe (16), Sebacina (16), and Geopora (7) were the most OTU-rich lineages. EMF richness within the forest-steppe zone and the transitional zone was limited, while the natural pine forest maintained diverse EMF communities in the forest zone. The changes of EMF community richness and composition along arid eco-zones were highlighted for the complex factors including precipitation, soil factors, host, DBH, and altitude. Indicator analysis revealed that some EMF showed clear host preference and some taxa, i.e., genera Geopora and Inocybe, were dominant in drought and alkaline-saline conditions attributed to their environmental preference. This study revealed that EMF communities were quite limited in the forest-steppe zone, while the forest region contained diverse EMF communities in the Loess Plateau. PMID:27063338

  5. Ectomycorrhizal fungal communities associated with Populus simonii and Pinus tabuliformis in the hilly-gully region of the Loess Plateau, China.

    Science.gov (United States)

    Long, Dongfeng; Liu, Jianjun; Han, Qisheng; Wang, Xiaobing; Huang, Jian

    2016-01-01

    The Loess Plateau region of northwestern China has unique geological and dry/semi-dry climate characteristics. However, knowledge about ectomycorrhizal fungal (EMF) communities in the Loess Plateau is limited. In this study, we investigated EMF communities in Populus simonii and Pinus tabuliformis patches within the forest-steppe zone, in pine forests within the forest zone, and the transitional zone between them. We revealed high species richness (115 operational taxonomic units [OTUs]) of indigenous EMF resources at the Loess Plateau, of which Tomentella (35 OTUs), Inocybe (16), Sebacina (16), and Geopora (7) were the most OTU-rich lineages. EMF richness within the forest-steppe zone and the transitional zone was limited, while the natural pine forest maintained diverse EMF communities in the forest zone. The changes of EMF community richness and composition along arid eco-zones were highlighted for the complex factors including precipitation, soil factors, host, DBH, and altitude. Indicator analysis revealed that some EMF showed clear host preference and some taxa, i.e., genera Geopora and Inocybe, were dominant in drought and alkaline-saline conditions attributed to their environmental preference. This study revealed that EMF communities were quite limited in the forest-steppe zone, while the forest region contained diverse EMF communities in the Loess Plateau. PMID:27063338

  6. Cultivation and Management Techniques of Agaricus bisporus in U-loess Cave Dwelling of Loess Plateau Region%黄土高原地区U型土窑洞双孢蘑菇栽培管理技术

    Institute of Scientific and Technical Information of China (English)

    张玉萍; 孟丽君; 王芳; 鹿有贵; 贾静

    2014-01-01

    Using U-loess cave dwelling cultivating Agaricus bisporus is a unique edible fungus production mode in loess plateau region. technical essential of this mode in production management were introduced so as to provide the reference for the cultivators.%利用U型土窑洞栽培双孢蘑菇是黄土高原地区独特的食用菌生产模式。文章介绍了该模式在生产管理方面的技术要点,以期对栽培者提供参考。

  7. Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain-size fractions and chemical forms. Results show that Rb is quite rich in the fraction of less than 2 m m, and exits only in the residual phase, while Sr is distributed in sand and silt fractions, occurring in the residual and carbonate phases. Therefore, variations of the concentrations of Rb and Sr in loess and palaeosols are closely related not only to dustfall compositions depending on winter monsoon wind strength but also to summer monsoon-induced pedogenic intensity. This indicates that variations of Rb/Sr ratio in Chinese loess sequences represent cyclic alternations of East Asian summer and winter monsoon climates on the orbital time-scale. Variations in Sr concentrations along the sequence bear a high similarity to the oxygen isotope record of the deep sea sediments over the past 2.5 Ma, whereas variations in Rb concentrations are in good agreement with the record of magnetic susceptibility determined with the duplicated samples from the same profile. This suggests that (1) the high-latitude ice volume is responsible for East Asian monsoon variations and (2) the signal of magnetic susceptibility depends dominantly on pedogenesis in Chinese loess sequences.

  8. Assessment of Holocene soil erosion rates on the loess plateau in East Poland using sedimentary archives from closed depressions

    Science.gov (United States)

    Kołodyńska-Gawrysiak, Renata; Poesen, Jean; Gawrysiak, Leszek

    2016-04-01

    Closed depressions (CDs) are typical geomorphological features of the European loess belt. They are closed sedimentation basins that enable the estimation of long-term soil erosion rates for different land use environments. This study was conducted in eastern Poland (Nałęczów Plateau). In this region CDs are rather small landforms and the area of 70% of all CDs does not exceed 1500 m2. The study objective was to assess Holocene soil erosion rates in the loess plateau based on a quantitative analysis of colluvial sediments deposited in CDs. Two representative CDs were selected for this study: one CD is located in an old (long-term) forest and the other is situated in a long-term agricultural land. The maximum depth of the CD in the forest, the mean slope gradient and area of the corresponding catchment are 4.9 m, 3.410 and 7568 m² respectively. For the CD in agricultural land these values are 3.2 m, 2.760 and 5156 m² respectively. In both CDs several dozen of drillings and two trenches (2 m long, 1m wide, 2 m deep) were made in the deepest point of the CDs. Mean long-term soil erosion rates were calculated based on the stratigraphy of the soil-sediment sequence infilling the CDs. C-14 and OSL datings of soils and colluvial sediments within the CDs were obtained. For the long-term agricultural used catchment of the CD it was calculated that since 6.31 ± 0.35 ka BP the mean annual soil loss due to water and tillage erosion is 0.63-0.7 t/ha/year or 279.3 mm. In the prehistoric period since 6.31 ± 0.35 ka BP until 1026-1162 AD the mean annual soil erosion rate amounted to 0,10-0.11 t/ha/year or 41.5 mm. During the last ca. 1000 years mean soil erosion rates increased to 3.99-4.63 t/ha/year or 249.2 mm. Results of long-term soil erosion rates (calculated using colluvial sediment sequences in CDs) from agricultural catchments in the loess regions of eastern Poland (this study) and Central Belgium (Gillijns et al. 2005) are quite similar. For the forested catchment

  9. Regional Evaluation of Wind Erosion of the Loess Plateau in Pengyang County, Ningxia Hui Autonomous Region, China

    Institute of Scientific and Technical Information of China (English)

    Sun Baoping; Ding Guodong; Li Yubao

    2003-01-01

    The loess plateau in China is well-known for its severe water erosion. A nationwide soil erosion survey discovered that wind erosion of the loess land is also greatly concerned. The severity of wind erosion for each land use in Pengyang County of Ningxia Hui Autonomous Region, China, was evaluated according to the national standard of soil erosion classification. The evaluation system includes a GIS database, an evaluation indicator system and a classification system for land and land use. The erodible nature of soil and annual soil loss of the most erodible land were obtained as follows: (1) Croplands plowed and harrowed in late autumn were the most erodible land,with an erosion intensity of medium grade and an erodible proportion of 46%; (2) The erodible proportion of natural grasslands was between 19.3% and 21.5%, whose erosion intensity was of mostly tolerable grade; (3) When it came to the whole county, there was 21.3% of the total area in tolerable grade in terms of wind erosion intensity, 42.1% slight and 34.8% medium.

  10. Palaeoenvironmental and chronological constraints on the Early Pleistocene mammal fauna from loess deposits in the Linxia Basin, NE Tibetan Plateau

    Science.gov (United States)

    Zan, Jinbo; Fang, Xiaomin; Zhang, Weilin; Yan, Maodu; Zhang, Tao

    2016-09-01

    The Longdan mammal fauna from the central part of Linxia Basin, NE Tibetan Plateau, is the first Early Pleistocene fauna in China in which the fossils are derived loess deposits, and it provides an excellent opportunity to document mammalian and environmental evolution in Asia. However, the precise age and palaeoenvironmental setting of the fauna are controversial due to the poor exposure of the outcrop section. In the present study, a 105-m-long drill core was obtained from Longdan village and used for detailed magnetostratigraphic dating. The results demonstrate that the late Pliocene- Pleistocene loess deposits in the Longdan section deposited since ca. 3 Ma and that the Longdan fauna has an age range of 2.5-2.2 Ma. In addition, the results of lithological and rock magnetic analyses demonstrate that paleosols are weakly developed throughout the whole core and that in the lower and middle parts the core the magnetic susceptibility and its frequency dependence are relatively low and uniform. These observations, combined with the ecological characteristics of the Longdan fauna, indicate that during the Early Pleistocene the climate in the Longdan area, and even in the Linxia Basin, was sub-humid and that the aeolian dust was frequently subjected to post-depositional reworking by water.

  11. Land-use changes in the small watershed of the Loess Plateau, hilly-gully region, China

    Institute of Scientific and Technical Information of China (English)

    Yini Han; Jianzhi Niu; Feizhou Wu

    2015-01-01

    As more and more farmland is converted to forestry, the need for effective decision support regarding the use of land in the fragile ecological environment of the Loess Plateau hilly-gully area. The Luoyugou watershed was chosen as the study area to calculate the single dynamic degree, integrated dynamic degree, and change indexes of land use, as well as the land-use type transition matrix. This was done by interpreting the TM and SPOT images of the Luoyugou watershed in 1986, 1995, and 2004 and making statistical analysis. The results of our statistical analysis show that the conversion of slope farm land to terrace and forest land plays a dominant role in land-use changes in the Luoyugou watershed from 1986 to 2004. The land-use changes are mainly driven by popula-tion growth, socio-economic development, consumer spending, and investment in forest ecology.

  12. Yield Potential of Soil Water and Its Sustainability for Dryland Spring Maize with Plastic Film Mulch on the Loess Plateau

    Science.gov (United States)

    Lin, Wen; Liu, Wenzhao

    2016-04-01

    Plastic film mulch(PM) is an agronomic measure widely used in the dryland spring maize production system on the Loess Plateau of China. The measure can greatly increase yield of dryland maize due to its significant effects on soil water conservation. Few researches have been done to investigate how the yield potential is impacted by PM. The yield-water use (ET) boundary equation raised by French and Schultz provides a simple approach to calculate crop water limited yield potential and gives a benchmark for farmers in managing their crops. However, method used in building the equation is somewhat arbitrary and has no strict principle, which leads to the uncertainty of equation when it is applied. Though using PM can increase crop yield, it increases soil temperature, promotes crop growth and increases the water transpired by crop, which further leads to high water consumption as compared with crops without PM. This means that PM may lead to the overuse of soil water and hence is unsustainable in a long run. This research is mainly focused on the yield potential and sustainability of PMing for spring maize on the Loess Plateau. A principle that may be utilized by any other researchers was proposed based on French & Schultz's boundary equation and on part of quantile regression theory. We used a data set built by collecting the experimental data from published papers and analyzed the water-limited yield potential of spring maize on the Loess Plateau. Moreover, maize yield and soil water dynamics under PM were investigated by a long-term site field experiment. Results show that on the Loess Plateau, the water limited yield potential can be calculated using the boundary equation y = 60.5×(x - 50), with a platform yield of 15954 kghm-2 after the water use exceeds 314 mm. Without PMing, the water limited yield potential can be estimated by the boundary equation y = 47.5×(x - 62.3) , with a platform yield of 12840 kghm-2 when the water use exceeds 325 mm, which

  13. Millennial-scale climate change since the last glaciation recorded by grain sizes of loess deposits on the northeastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    Lü Lianqing; FANG Xiaomin; LU Huayu; HAN Yongxiang; YANG Shengli; LI Jijun; AN Zhisheng

    2004-01-01

    Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution loess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 104 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at ~36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43-36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.

  14. Correlation and interpretation of paleosols and loess across European Russia and Asia over the last interglacial-glacial cycle

    Science.gov (United States)

    Rutter, Nathaniel W.; Rokosh, Dean; Evans, Michael E.; Little, Edward C.; Chlachula, Jiri; Velichko, Andrei

    2003-07-01

    Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle.

  15. Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chao; LIU Guo-bin; XUE Sha; and XIAO Lie

    2013-01-01

    The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows:two natural grassland (Artemisia capillaries and Heteropappus altaicus), two artificial grassland (Astragalus adsurgens and Panicum virgatum), and two artificial shrubland (Caragana korshinskii and Hippophae rhamnoides) species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids (PLFAs) and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative (G-) bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive (G+) bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal:bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.

  16. Adaptation of potato production to climate change by optimizing sowing date in the Loess Plateau of central Gansu, China

    Institute of Scientific and Technical Information of China (English)

    WANG Chun-ling; SHEN Shuang-he; ZHANG Shu-yu; LI Qiao-zhen; YAO Yu-bi

    2015-01-01

    Potato grows in most part of China, it achieves higher yield and better quality in Gansu Province than in others. With global warming, its growth duration has been prolonged and sowing date become earlier than before. Therefore, to regulate its sowing date and growing period is of great signiifcance for better harvest. In this study, experiments were conducted with six sowing-date treatments of potato in Dingxi, which is in the Loess Plateau of central Gansu Province in Northwest China in 2010. The growth period, morphological index and change in yield and their relationships with temperature, precipitation, and other climatic factors were investigated for each treatment. Results show that the crop with different sowing dates experienced different climate conditions, leading to distinct growth duration, plant height, and leaf area index. The growth duration was shortened due to a delay in sowing date. For each 15-day delay in sowing, the growth duration was reduced by 12 days on average. A signiifcant linear relationship was found between numbers of days either from seeding to emergence or from lfowering to harvest and mean temperature over the corresponding period. Dry matter accumulation, tuber fresh weight, and ifnal yield were al decreased because of insufifcient cumulative temperature over the shorter growing periods. Marked differences in tuber yield were discovered among the six treatments of sowing date, the potato planted on May 27 giving the highest yield. The potato planted either earlier or later would produce invariably lower yield than the treatment of May 27. Late May therefore can be taken as the optimum sowing time of potato in this region because the crop can ful y utilize thermal resource. We conclude that to postpone sowing time is a good practice for potato production to adapt to climate warming in the Loess Plateau of central Gansu, China.

  17. The effect of modification of pedon on distribution of soil moisture, plant growth and yield in loess plateau (E Poland)

    Science.gov (United States)

    rejman, jerzy

    2013-04-01

    Long-term tillage and water erosion in loess areas resulted in modification of pedon structure and redistribution of soils within the fields. The changes are more significant in the areas of largely differentiated past micro-relief of relatively small differences in height. The effect of soil redistribution on soil moisture content, plant growth, and yield was studied within a small field (0.72 ha) located in the loess plateau (Lublin Upland, E Poland) in the years 2006-08. Structure of Haplic Luvisol, soil properties, and yield of spring barley (Hordeum vulgaris L.) were determined in a grid 10x10 m, and plant growth in sites located along the transect. Studies showed that after about 180 years of agricultural land use of the experimental site, small micro-relief forms as depressions and hills were partly or completely leveled by tillage and water erosion. In the effect of relief transformation, soils of eroded profiles represented 47.2, depositional soils 34.7 and non-eroded soils 18.1% of total number of studied pedons. Soil thickness, clay, silt and SOC were spatially correlated with a range of autocorrelation from 28 to 35 m. Soil redistribution affected the soil water content during vegetation season. Significantly higher water content at near soil surface was found on sites with depositional and non-eroded soils in April-May, while on eroded soils in June-July. As antecedent moisture conditions affect the water erosion process, various parts of field area could be responsible for quicker formation of runoff in different seasons of the year. Relation between crop and soil was complex and varied with precipitation during growing seasons. The more rainfall was close to the normal, the more significant positive correlations between the yield and soil thickness, silt and SOC, and negative with clay were found. The relations were reversed in a dry year, when yields were much lower. Results of the studies showed that loess plateau was significantly transformed

  18. Multiproxy biomarker, isotopic and pollen reconstructions of the middle to late Holocene paleoclimate of the Loess Plateau in centre China

    Science.gov (United States)

    Sun, H.; Seki, O.; Zhou, A.; Chen, F.; Schouten, S.; Toney, J. L.; Bendle, J.

    2011-12-01

    The Asian monsoon is a key component of the earth's climate system that directly affects the livelihood of 50 million people on the loess plateau of central China. At the far edge of monsoonal influence, this region is especially vulnerable to future changes in temperature and evaporation / precipitation. Therefore, paleoclimatic information on the natural sensitivity of the region to changes in monsoon driven aridity are crucial. Despite the need for multiproxy records of Holocene climate from this region, reconstructions are rare, because of the low resolution of loess deposits and the scarcity of other paleoclimate archives (e.g. natural lakes, speleothems). Here we present multiple proxy records from Tianchi lake, one of the few nature lakes on the loess plateau and central China. The chronology is well constrained by a high-resolution (20 AMS 14C dates) radiocarbon age-model, spanning the past 6200 years. Here we present pollen, Glycerol dibiphytanyl glycerol tetraethers (GDGTs), lake macrophyte and higher plant-wax biomarkers to reconstruct regional climate change during the middle to late Holocene. Evidence from pollen data suggest that deciduous trees decreased from 6200 cal yr BP and then more rapidly from 1000 yr BP. Modern and downcore molecular distribution patterns of n-alkanes and n-alkanoic acids, especially n-alkane Paq values, suggest increasing relative abundance of macrophytes over this time, which we interpret (based on lake morphology) as decreasing lake-level. Using the recent Sun et al (2011) regional calibration we derive mean annual GDGT based temperatures (MBT/CBT-MATs) with reasonable ranges. Our temperature reconstruction closely correlates on millennial to centennial timescales with the independent D/H measurements on C28 fatty acid methyl esters (C28 FAMEs), whose signal is assumed to derive primarily from terrestrial plant waxes and the δD values to reflect local changes in relative humidity. Comparisons of our independent GDGT

  19. The Formation of Barrier Winds East of the Loess Plateau and Their Effects on Dispersion Conditions in the North China Plains

    Science.gov (United States)

    Hu, Xiao-Ming; Li, Xingliang; Xue, Ming; Wu, Dui; Fuentes, Jose D.

    2016-10-01

    The North China Plain (NCP) to the east of the Loess Plateau is one of the most heavily polluted areas in the world. Weak surface flow in the western part of the NCP exacerbates the air pollution in this region. Deceleration of low-level flow when approaching the Loess Plateau, together with enhanced roughness associated with large cities, were previously ascribed as the causes for low wind speeds in the NCP. Using numerical simulations with a one-layer dispersion model, we identify that dynamic modification of airflow by the Loess Plateau (not just simple deceleration due to mountain blocking) plays an important role in reducing the wind speed over the NCP. Dynamically-induced northerly barrier winds, superimposed on the prevailing southerly/south-easterly flow, reduce the wind speed in a 50-100 km wide region to the east of the Plateau, partially explaining the weak winds in the western part of the NCP. Poor dispersion conditions due to weak horizontal winds likely contribute to the accumulation of pollutants in this region.

  20. Carbonate isotopic records of paleoclimate changes in Chinese loess

    Institute of Scientific and Technical Information of China (English)

    韩家懋; 姜文英; 刘东生; 吕厚远; 郭正堂; 吴乃琴

    1996-01-01

    Oxygen and carbon isotopes of carbonate in concretion and bulk samples collected from Xifeng. Luochuan and Weinan loess sections, China, have been analyzed. It has been found that carbon and oxygen isotopic ratios of concretion in paleosol, as useful paleodimatic indicators, recorded temperature and humidity variation during their formation. Comparison of isotopic data from different locations may offer a spatial picture of past environmental changes. Isotopic data from carbonate of bulk sample also include useful environmental information. Carbon and oxygen isotopic curves of past 150ka in Weinan completely reflect the fluctuations of the paleodimate with different stratigraphical units. The curves can correlate well with those of other dimatic proxies and of the deep sea sediments.

  1. The estimation of basic experimental parameters in the fine-grained quartz multiple-aliquot regenerative-dose OSL dating of Chinese loess

    International Nuclear Information System (INIS)

    The sensitivity-corrected multiple-aliquot regenerative-dose (MAR) protocol provides a reliable approach for fine-grained quartz optically stimulated luminescence (OSL) dating. For reliable estimation of the equivalent dose (De), we investigated certain basic experimental parameters in the fine-grained quartz MAR OSL dating of Chinese loess. (1) For suitable bleaching of the natural OSL signal of the regenerative-dose aliquots, the effect of bleaching duration using sunlight, SOL2 and blue LEDs on De was studied, and it is found that the appropriate method is a short-duration SOL2 (e.g. 5 min) or blue LEDs (e.g. 60 s) bleaching. (2) To select the appropriate test dose, the relationship between the test dose and De was investigated based on three samples having De values of approximately 11, 31 and 137 Gy respectively. It is suggested that the test dose for sensitivity correction may be limited to less than approximately 10–20 Gy. (3) Three commonly used fitting modes for quartz OSL growth curve were compared at three regenerative-dose scales. The results indicate that the mode of two saturating exponential functions plus a constant is appropriate and universal. (4) The comparison of De values derived using OSL approach with those obtained using the recuperated OSL (ReOSL) protocol shows that the reliable De estimation in the fine-grained quartz MAR OSL dating of Chinese loess may be limited to less than approximately 300 Gy. (5) The comparison of growth curves for 18 samples from the Weinan, Xifeng and Jingyuan sites shows that it is feasible to construct a standardized growth curve (SGC) for fine-grained quartz OSL signal in the Chinese Loess Plateau (CLP).

  2. Evapotranspiration and Soil Moisture Balance for Vegetative Restoration in a Gully Catchment on the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    HUANG Yi-Long; CHEN Li-Ding; FU Bo-Jie; ZHANG Li-Ping; WANG Yan-Lin

    2005-01-01

    Evapotranspiration, soil moisture balance and the dynamics in a gully catchment of the Loess Plateau in China were determined with 6 land use treatments including natural grassland, shrubs (Caragana microphylla), two woodlands (Prunus armeniaca var. ansu and Pinus tabulaeformis), cultivated fallow, and farmland (Triticum aestivum L.) in order to obtain a better understanding of soil moisture balance principles and to improve vegetation restoration efficiency for ecological rebuilding on the plateau. Average runoff from cultivated fallow was very high, reaching 10.3% of the seasonal rainfall. Evapotranspiration under T. aestivum was not significantly different from natural grasslands. Compared with natural grass, evapotranspiration was significantly greater (P < 0.05) in 2002 and there was an increase in soil moisture depleted in the 1-3 m soil under P. armeniaca, P. tabulaeformis and C. microphylla. During the two years of the study the average soil moisture (0-100 cm soil profile) of T. aestivum was generally the highest, with P. armeniaca, P. tabulaeformis and C. microphylla usually the lowest. Thus, according to the soil moisture balance principle for this area the planned reforestation project was not ecologically reasonable. Reducing human disturbance and restoration with grass could be more effective.

  3. Spatial heterogeneity of surface roughness during different erosive stages of tilled loess slopes under a rainfall intensity of 1.5 mm min-1

    Science.gov (United States)

    The loess tilled slope is the main place for soil erosion in Chinese Loess Plateau, and studies about its spatial heterogeneity (SH) of surface roughness (SR) has been one of the most important problems in the field of soil erosion. The objective of this study was to reveal the SH of SR of 4 typical...

  4. An Indicator System for Assessing Soil Erosion in the Loess Plateau Gully Regions:A Case Study in the Wangdonggou Watershed, China

    Institute of Scientific and Technical Information of China (English)

    NI Shao-Xiang; MA Guo-Bin; WEI Yu-Chun; JIANG Hai-Fu

    2004-01-01

    The Wangdonggou Watershed on the Loess Plateau in China was selected as the study area to develop a model for soil erosion assessments. Using the data collected at 20 sampling sites all tentatively selected indicators were assessed against their corresponding erosion intensity through a correlation analysis. Eight highly correlated indicators were then chosen for the soil erosion assessment. In addition, threshold limits to delineate the class size for these indicators and weights to rank them were determined. Next, a grading model incorporating the selected indicators class rating and their associated weights was developed and verified by an on site evaluation of the soil erosion intensity in the study area. Results of the verification showed that the overall accuracy of the indicator system for assessing soil erosion in the Loess Plateau gully regions could reach 85%.

  5. Spatial Heterogeneity of Soil Moisture and the Scale Variability of Its Influencing Factors: A Case Study in the Loess Plateau of China

    OpenAIRE

    Mingyue Zhao; Lina Zhong; Yang Qiu; Qiang Feng; Wenwu Zhao

    2013-01-01

    Soil moisture is an important factor for vegetation restoration and ecosystem sustainability in the Loess Plateau of China. The strong spatial heterogeneity of soil moisture is controlled by many environmental factors, including topography and land use. Moreover, the spatial patterns and soil hydrological processes depend on the scale of the site being investigated, which creates a challenge for soil moisture forecasts. This study was conducted at two scales: watershed and small watershed. Th...

  6. Seed Dormancy, Seedling Establishment and Dynamics of the Soil Seed Bank of Stipa bungeana (Poaceae) on the Loess Plateau of Northwestern China

    OpenAIRE

    Hu, Xiao Wen; Wu, Yan Pei; Ding, Xing Yu; Zhang, Rui; Wang, Yan Rong; Baskin, Jerry M.; Carol C. Baskin

    2014-01-01

    Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after m...

  7. Patterns of taxonomic, phylogenetic diversity during a long-term succession of forest on the Loess Plateau, China: insights into assembly process

    OpenAIRE

    Yongfu Chai; Ming Yue; Xiao Liu; Yaoxin Guo; Mao Wang; Jinshi Xu; Chenguang Zhang; Yu Chen; Lixia Zhang; Ruichang Zhang

    2016-01-01

    Quantifying the drivers underlying the distribution of biodiversity during succession is a critical issue in ecology and conservation, and also can provide insights into the mechanisms of community assembly. Ninety plots were established in the Loess Plateau region of northern Shaanxi in China. The taxonomic and phylogenetic (alpha and beta) diversity were quantified within six succession stages. Null models were used to test whether phylogenetic distance observed differed from random expecta...

  8. The study of the geomagnetic excursions and the relative intensities from Chinese loess 10Be over the past 130 ka

    Science.gov (United States)

    Zhou, W.; Xian, F.; Beck, J.; An, Z.; Wu, Z.; Liu, M.; Chen, M.; Priller, A.; Kutschera, W.; Jull, A. T.; Yu, H.; Song, S.; Cheng, P.; Kong, X.

    2009-12-01

    Chinese loess is well-known archive for the paleogeomagnetic and paleoclimatic studies [Zhou et al., 1990; An et al., 1990; Zhu et al., 2007]. However, earlier efforts to extract weak geomagnetic excursion signals from Chinese loess 10Be were always unsuccessful due to the complexities of loess 10Be, which results in the fact that loess 10Be was only used as a climatic proxy [Shen et al., 1992; Beer et al.,1993; Gu et al.,1996]. Meanwhile, knowledge on the precise stratigraphic horizons of geomagnetic excursions with a reliable dating [Channell, 2006], on whether the short-lived excursions such as Blake can not be recorded in paleosol unit are still controversial. Here, we present the reconstructed past 130ka geomagnetic excursions and relative paleointensities for the first time from 10Be records in two Chinese loess sections. Results are comparative with those of independent geomagnetic research on Atlantic and Pacific sediments. The derived Laschamp and Blake events lie in the loess-paleosol (L1SS1 and S1SS3) corresponding to mid MIS 3 and 5e respectively. Our studies prove the potential application of the complex loess 10Be for long-term geomagnetic tracing and provide new evidence to answer the long-existing debates on the precise stratigraphic horizon of geomagnetic excursions. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary. References 1. Zhou, L. P., F. Oldfield, A. G. Wintle, S. G. Robinson, and J. T. Wang (1990), Partly pedogenic origin of magnetic variations in Chinese loess, Nature, 346, 737-739. 2. An, Z. S., T. S. Liu, Y. C. Lu, S. C. Porter, G. Kukla, X. H. Wu, and Y. M. Hua (1990), The long-term paleomonsoon variation recorded by the loess-paleosol sequence in Central China, Quat. Int., 7-8, 91-95. 3. Zhu, R. X., R. Zhang, C. L. Deng, Y. X. Pan, Q. S. Liu, and Y. B. Sun (2007), Are Chinese loess deposits essentially continuous?, Geophys. Res. Lett

  9. [Responses of plant functional traits to micro-topographical changes in hilly and gully region of the Loess Plateau, China].

    Science.gov (United States)

    Yang, Shi-suo; Wen, Zhong-ming; Miao, Lian-peng; Qi, De-hui; Hua, Dong-wen

    2014-12-01

    Plant functional traits are closely tied to the performance of plants in specific microenvironments, and reflect their ability to adapt to those microenvironments. In areas with complex topography, analyzing the responses of plant functional traits to microtopographical changes is crucial to understanding the adaptive strategies of plants in diverse environments. This paper analyzed fluctuations in soil nutrients as well as correlations between plant functional traits and changes in topography at the family and community levels in selected natural vegetation communities in the foreststeppe zone of the loess hilly and gully region in Loess Plateau of China. Significant differences in plant functional traits were primarily driven by the phylogenetic background or species composition of the community. Slope aspect exerted less impact while slope positions had no significant effect on plant traits at the community level. No significant changes in plant functional traits were observed with changes in topography at the community level. However, leaf nitrogen and root nitrogen contents of Leguminous and Compositae species differed significantly With slope positions. The root tissue density of Graminaceous species differed significantly with slope positions. Root density exhibited significant positive correlations with soil nutrient and carbon contents at the community level. Both leaf nitrogen and root nitrogen contents of Leguminous species were positively correlated with soil phosphorus content, while leaf nitrogen and root nitrogen contents of both Graminaceous and Compositae species were significantly positively related to soil nitrogen content. The results demonstrate the different responses of species of different families to changes in micro-topography and their distinctive adaptive strategies to the environment.

  10. Effects of legume species introduction on vegetation and soil nutrient development on abandoned croplands in a semi-arid environment on the Loess Plateau, China.

    Science.gov (United States)

    Yuan, Zi-Qiang; Yu, Kai-Liang; Epstein, Howard; Fang, Chao; Li, Jun-Ting; Liu, Qian-Qian; Liu, Xue-Wei; Gao, Wen-Juan; Li, Feng-Min

    2016-01-15

    Revegetation facilitated by legume species introduction has been used for soil erosion control on the Loess Plateau, China. However, it is still unclear how vegetation and soil resources develop during this restoration process, especially over the longer term. In this study, we investigated the changes of plant aboveground biomass, vegetation cover, species richness and density of all individuals, and soil total nitrogen, mineral nitrogen, total phosphorus and available phosphorus over 11 years from 2003 to 2013 in three treatments (natural revegetation, Medicago sativa L. introduction and Melilotus suaveolens L. introduction) on the semi-arid Loess Plateau. Medicago significantly increased aboveground biomass and vegetation cover, and soil total nitrogen and mineral nitrogen contents. The Medicago treatment had lower species richness and density of all individuals, lower soil moisture in the deep soil (i.e., 1.4-5m), and lower soil available phosphorus. Melilotus introduction significantly increased aboveground biomass in only the first two years, and it was not an effective approach to improve vegetation biomass and cover, and soil nutrients, especially in later stages of revegetation. Overall, our study suggests that M. sativa can be the preferred plant species for revegetation of degraded ecosystems on the Loess Plateau, although phosphorus fertilizer should be applied for the sustainability of the revegetation.

  11. Optically stimulated luminescence dating as a tool for calculating sedimentation rates in Chinese loess: comparisons with grain-size records

    DEFF Research Database (Denmark)

    Stevens, Thomas; Lu, HY

    2009-01-01

    ; this limits interpretation of the environmental changes revealed by the loess record. In particular, while the Quaternary/Neogene Chinese loess and Red Clay sequences have the potential to provide detailed records of past sedimentation and climate change, there is great uncertainty concerning: (i......Understanding loess sedimentation rates is crucial for constraining past atmospheric dust dynamics, regional climatic change and local depositional environments. However, the derivation of loess sedimentation rates is complicated by the lack of available methods for independent calculation......) the influences on sediment grain-size and accumulation; and (ii) their relationship through time and across the depositional region. This uncertainty has led to the widespread use of assumptions concerning the relationship between sedimentation rate and grain-size in order to derive age models and climate...

  12. Fractal features of soil particle size distribution in layered sediments behind two check dams: Implications for the Loess Plateau, China

    Science.gov (United States)

    Wei, Xia; Li, Xungui; Wei, Ning

    2016-08-01

    The layered sediment deposited behind a check dam can provide useful information about soil erosion processes in the dam-controlled area. This study aims to evaluate the possible fractal nature of layered sediments behind check dams, assessing whether fractal dimension can serve as a feasible index for evaluating the impact of land use types on the area controlled by the check dam. Fractal dimension measurement was employed to analyze the features of soil particle size distribution (PSD) for different layered sediments of the Shipanmao and Zhangshan check dams in the Dalihe River Basin of the Loess Plateau, China. Results show that the predominant soil particle sizes of the sediment layers behind the Shipanmao and Zhangshan dams are silt-clay (soil particle sizes coincide with larger CV values. The fractal dimension (Dm) of the PSD ranges from 2.111 to 2.219, and 2.144 to 2.447 for Shipanmao and Zhangshan, respectively. The Dm values tend to increase and decrease for the layered sediments from top to bottom with some turning points. The turning points of Dm are related to the trends of the soil PSDs in the adjacent sediment layers. Although Dm has significant positive and negative correlations with the silt-clay and the fine sand size fractions, respectively, no correlation with the coarse sand fraction was observed. Soil PSD is a more dominant factor affecting Dm than the time lag between soil erosion and sediment deposition. Overall, Dm decreased for Shipanmao during the deposition period (1972-1979). The total increment of the C factor in the universal soil loss equation and the soil erosion amount per rainfall erosivity were applied to analyze land use changes between 1972 and 1979 for the dam-controlled area of the Shipanmao dam. The total increment of C during 1972-1979 was 0.021 and the soil erosion amount per rainfall erosivity was smaller in 1972 than in 1979, indicating desertification in the dam-controlled area. In addition, the land use types prevalent

  13. Canopy transpiration of two black locust (Robinia pseudoacacia) plantations with different ages in semi-arid Loess Plateau, China

    Science.gov (United States)

    Jiao, L.

    2015-12-01

    Black locust (Robinia pseudoacacia) was widely planted to control soil erosion and restore degraded ecosystem in Loess Plateau. The water use of the plantations was concerned due to its potential effects on hydrological cycle and regional water resource. Although some studies estimated canopy transpiration (Ec) of the mature black locust plantation, variation in Ec in plantations with different ages was not clear. In this study, we selected two plantations with different ages (12 years and 27 years, denoted as young stand and mature stand, respectively) in similar topographical conditions in Yangjuangou catchment in the central of Loess Plateau. Sap flux density (Fd) and tree biometrics were measured in each stand during the growing season in 2014. Soil water content (SWC) in each plot and meteorological variables in the catchment were simultaneously monitored. Tree transpiration (Et) was derived from Fd and tree sapwood area (As). Canopy transpiration (Ec) was estimated by a product of mean stand sap flux density (Js) and stand total sapwood area (AST). The mean Fd of mature trees was 2-fold larger than that of young trees.However, tree-to-tree variation in Fd among sampled trees within mature stand was evident compared to that within young stand. Mean Et in mature stand was higher than that in young stand. Ec in mature stand was significant higher than that in young stand,with cumulative value of 54 mm and 27 mm respectively. This is attributed to higher Js in mature stand although AST in young is slightly higher than that in mature stand. The patterns of daily Ec during the growing season were similar in both stands during the study period. A exponential saturation model can explain the responses of Ec to vapor deficit pressure (VPD) and solar radiation (Rs) in both stands.The relationship between Ec and SWC was not detected. Our finding suggested that stand age should be taken into consideration when estimated vegetation water use in this region. Further

  14. Ecosystem health assessment on the hill and gully area of Loess Plateau in Inner Mongolia,China

    Institute of Scientific and Technical Information of China (English)

    HUANG Heping; YANG Jie; SONG Bingyu; BAO Tiejun

    2006-01-01

    Maintenance of ecosystem health is the primary focus of a sound ecological restoration.Yet methods involved in quantifying and assessing the health level remain a challenge to the ecological community.In this study,we selected the hill and gully area of Loess Plateau,Inner Mongolia,China,as our study area.The soil and water erosions in this area continue to be responsible for many environmental problems in northern China because of its fragility and long disturbance history.In this study,we developed an assessment method of indicator system(AMIS)based on analytical hierarchy process(AHP),fuzzy mathematics.and the theory of net-hierarchy.At ecosystem or catchment scale,three sample areas,that is(1)intact vegetation(i.e., Aguimiao Natural Reserve,110°45'E,39°28'N),(2)reconstructed vegetation(Wufendigou Soil and Water Conservation Experimental Area,111°07'E 39°45'N),and (3)severely degraded vegetation(Yangquangou Catchment,111°06'E,39°45'N)in the hill and gully area of Loess Plateau in Inner Mongolia.China.were selected to examine ecosystem vigor,organizational structure,service function,and soil healm.We applied the AMIS for all three landscapes by categorizing each ecosystem into five health levels.Wle found that the health index for reconstructed vegetation were at levels of Ⅳ,Ⅱ,Ⅳ,and Ⅲ,while those of degraded vegetation were ranked at Ⅴ,Ⅳ,Ⅴ,and Ⅳ.Overall.the comprehensive ecosystem health index of reconstmcted vegetation was lower than that of intact vegetation but higher than that of degraded vegetation.The health index for reconstructed vegetation was at level Ⅲ.and that of degraded vegetation was still at level Ⅳ.The contributing values were:organization structure>soil health>vigor>service function.Based on our results and assessments,we proposed several management recommendations and methods for restoring the regional ecosystems.

  15. Spatial-temporal patterns of water use efficiency and climate controls in China's Loess Plateau during 2000-2010.

    Science.gov (United States)

    Zhang, Tian; Peng, Jian; Liang, Wei; Yang, Yuting; Liu, Yanxu

    2016-09-15

    Accurate assessments of spatial-temporal variations in water use efficiency (WUE) are important for evaluation of carbon and water balances. In this study, the spatial and temporal patterns of WUE and associated climate controls in China's Loess Plateau are investigated over 2000-2010 by utilizing remote sensing data and multiple statistical methods; which provides a greater understanding about how WUE changed after the Grain to Green Program (GTGP) launched. Carbon sequestration (i.e., net primary productivity, NPP) is estimated with the CASA model and water consumption (i.e., evapotranspiration, ET) is obtained from the MODIS product (i.e., MOD16). Our results identify an increasing trend in the regional mean NPP that amounted to 7.593gC/m(2)·yr with an average value of 310.035gC/m(2)·yr. Changes in ET are segmented into three stages, the growth (2000-2003), decline (2004-2006) and stable (2007-2010) stages. Regional WUE is measured at 0.915gC/mm·m(2) and shows an upward trend at a rate of 0.027gC/mm·m(2)·yr. Spatially, significant regional heterogeneity is found in both NPP and WUE with gradients decreasing from the southeast to the northwest, but sharp rises detected in northern Shaanxi. At the biome level, the annual average WUE of the four groups decrease in the order of grasslands>woodlands>shrublands>croplands. Moreover, all biomes in the grassland ecosystems exhibit a growth in WUE as does the arid desert zone in the northwestern region, suggesting that vegetation in moderately water-deficient areas may have a higher tolerance to drought. Among different meteorological factors, precipitation and drought severity index (DSI) in the Loess Plateau show a latitudinal zonality and influences the WUE, which indicated that the moisture rather than temperature would be the major control factor of the regional WUE. Finally, significant variation in vegetation WUE sensitivity in response to meteorological factors is noted. Temperature is found to be the

  16. 大气生成宇宙成因核素10Be在中国黄土中的应用研究进展%Review on the application of the atmospheric produced10Be in Chinese loess

    Institute of Scientific and Technical Information of China (English)

    孔祥辉; 周卫健; 武振坤; 杜雅娟; 赵国庆; 谢兴俊

    2016-01-01

    中国黄土10Be研究大体上经历了三个阶段:(1)地球化学行为研究:10Be主要吸附于细颗粒及粘土颗粒,在黄土中保存性好,不会发生明显的化学迁移过程;(2)古气候代用指标应用:10Be在黄土和古土壤层中的浓度变化与代表气候变化的深海氧同位素曲线变化一致,且可借此进行黄土年代标尺的建立;(3)地球环境示踪研究:示踪地磁场倒转及漂移事件,恢复古地磁场相对强度变化,以及定量重建黄土高原地区古降水变化历史等。由于近年来黄土10Be环境示踪研究取得了可喜的成果,笔者认为有必要从以上三个方面对中国黄土10Be研究历史进行较为系统的梳理回顾,总结当前最新研究进展,展望未来黄土10Be在环境示踪中的研究方向,希望能使读者在短时间内了解中国黄土10Be研究的发展脉络。%Background, aim, and scope The history of Chinese loess10Be studies can be recognized as three stages. (1) The geochemical behavior of10Be in Chinese loess: it is preferred to be absorbed on the small size particles and the clay minerals, it can be preserved well after it deposited and would not be leached by the raillfall; (2) as a paleoclimatic proxy: the variation of10Be concentration in the loess and paleosol correlated well with the marine isotope stages and with the correlation between these two proxies, it can be used to establish the chronology of Chinese loess-paleosol sequences; (3) tracing earth’s environmental changes: recovering the variations of geomagnetic ifeld intensity, tracing the geomagnetic polarity reversals/excursions and reconstructing the paleorainfall over the Chinese Loess Plateau. Since very signiifcant progress has been made about the third one recently, it is necessary to make a comprehensive review on the application of cosmogenic10Be in Chinese loess, and by doing this to discuss the future work about the Chinese loess10Be

  17. Seasonal and Annual Variations of CO2 Fluxes in Rain-Fed Winter Wheat Agro-Ecosystem of Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    WANG Wen; LIAO Yun-cheng; GUO Qiang

    2013-01-01

    To accurately evaluate the carbon sequestration potential and better elucidate the relationship between the carbon cycle and regional climate change, using eddy covariance system, we conducted a long-term measurement of CO2 fluxes in the rain-fed winter wheat field of the Chinese Loess Plateau. The results showed that the annual net ecosystem CO2 exchange (NEE) was (-71.6±5.7) and (-65.3±5.3) gCm-2y-1 for 2008-2009 and 2009-2010 crop years, respectively, suggesting that the agro-ecosystem was a carbon sink (117.4-126. 2gCm-2yr-1). However, after considering the harvested grain, the agro-ecosystem turned into a moderate carbon source. The variations in NEE and ecosystem respiration (Reco) were sensitive to changes in soil water content (SWC). When SWC ranged form 0.15 to 0.21 m3 m-3, we found a highly significant relationship between NEE and photosynthetically active radiation (PAR), and a highly significant relationship between Reco and soil temperature (Ts). However, the highly significant relationships were not observed when SWC was outside the range of 0.15-0.21 m3 m-3. Further, in spring, the Reco instantly responded to a rapid increase in SWC after effective rainfall events, which could induce 2 to 4-fold increase in daily Reco, whereas the Reco was also inhibited by heavy summer rainfall when soils were saturated. Accumulated Reco in summer fallow period decreased carbon fixed in growing season by 16-25%, indicating that the period imposed negative impacts on annual carbon sequestration.

  18. Afforestation using micro-catchment water harvesting system with microphytic crust treatment on semi-arid Loess Plateau: A preliminary result

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-hui; WANG Ke-qin; WANG Bin-rui; YU Chun-tang

    2005-01-01

    Water harvesting is one of main measures to solve water shortage resulting from less precipitation and erratically seasonal distribution in arid and semi-arid areas. Different types of anti-infiltration treatments including mechanical and chemical to micro-catchment and their runoff efficiencies had been reported. This paper, through 5 years experiment from 1992 to 1996, is aimed at studying the impacts of microcatchment water-harvesting system (MCWHS) with microphytic crust treatment on afforestation on semi-arid Loess Plateau. The results showed that after 3 years of crust inoculation, crust had covered majority of MCWHS and the function of water harvesting had also been demonstrated partially, there were significant difference in soil moisture of shallow soil layer in three typical spring stages between crust cover and control treatments (0.05 level), and about 0.9%-6.04% increase of monthly mean soil moisture within 1m soil layer in spring of late 3 years. The impact of severe spring drought can be alleviated effectively. In the meanwhile, as crust developed on the treated surface, there are significant differences (0.05 level) for tree height (H), diameter at breast height (DBH) and diameter at ground level (DGL) at the end of the study period (1996) with the increases by 22.38%, 17.34%, and 20.49% respectively compared with the control treatment. Microphytic crust, as one of biological infiltration-proof materials, may become the optimized option for revegetation in Chinese Great West Development Strategy due to its self-propagation, non-pollution to water qualities, long use duration and relatively cost effective. Further work should be focused on the selection of endemic crust species and their batch-culture in arid environment.

  19. Carbon Storage Patterns of Caragana korshinskii in Areas of Reduced Environmental Moisture on the Loess Plateau, China.

    Science.gov (United States)

    Gong, Chunmei; Bai, Juan; Wang, Junhui; Zhou, Yulu; Kang, Tai; Wang, Jiajia; Hu, Congxia; Guo, Hongbo; Chen, Peilei; Xie, Pei; Li, Yuanfeng

    2016-01-01

    Precipitation patterns are influenced by climate change and profoundly alter the carbon sequestration potential of ecosystems. Carbon uptake by shrubbery alone accounts for approximately one-third of the total carbon sink; however, whether such uptake is altered by reduced precipitation is unclear. In this study, five experimental sites characterised by gradual reductions in precipitation from south to north across the Loess Plateau were used to evaluate the Caragana korshinskii's functional and physiological features, particularly its carbon fixation capacity, as well as the relationships among these features. We found the improved net CO2 assimilation rates and inhibited transpiration at the north leaf were caused by lower canopy stomatal conductance, which enhanced the instantaneous water use efficiency and promoted plant biomass as well as carbon accumulation. Regional-scale precipitation reductions over a certain range triggered a distinct increase in the shrub's organic carbon storage with an inevitable decrease in the soil's organic carbon storage. Our results confirm C. korshinskii is the optimal dominant species for the reconstruction of fragile dryland ecosystems. The patterns of organic carbon storage associated with this shrub occurred mostly in the soil at wetter sites, and in the branches and leaves at drier sites across the arid and semi-arid region. PMID:27412432

  20. Linking the soil moisture distribution pattern to dynamic processes along slope transects in the Loess Plateau, China.

    Science.gov (United States)

    Wang, Shuai; Fu, Bojie; Gao, Guangyao; Zhou, Ji; Jiao, Lei; Liu, Jianbo

    2015-12-01

    Soil moisture pulses are a prerequisite for other land surface pulses at various spatiotemporal scales in arid and semi-arid areas. The temporal dynamics and profile variability of soil moisture in relation to land cover combinations were studied along five slopes transect on the Loess Plateau during the rainy season of 2011. Within the 3 months of the growing season coupled with the rainy season, all of the soil moisture was replenished in the area, proving that a type stability exists between different land cover soil moisture levels. Land cover combinations disturbed the trend determined by topography and increased soil moisture variability in space and time. The stability of soil moisture resulting from the dynamic processes could produce stable patterns on the slopes. The relationships between the mean soil moisture and vertical standard deviation (SD) and coefficient of variation (CV) were more complex, largely due to the fact that different land cover types had distinctive vertical patterns of soil moisture. The spatial SD of each layer had a positive correlation and the spatial CV exhibited a negative correlation with the increase in mean soil moisture. The soil moisture stability implies that sampling comparisons in this area can be conducted at different times to accurately compare different land use types. PMID:26620951

  1. Factors Affecting Distribution of Vegetation Types on Abandoned Cropland in the Hilly-Gullied Loess Plateau Region of China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A study was conducted in the forest-steppe region of the Loess Plateau to provide insight into the factors affecting the process of vegetation establishment,and to provide recommendations for the selection of indigenous species in order to speed up the succession process and to allow the establishment of vegetation more resistant to soil erosion.Four distinctive vegetation types were identified,and their distribution was affected not only by the time since abandonment but also by other environmental factors,mainly soil water and total P in the upper soil layers.One of the vegetation types,dominated by Artemisia scoparia,formed the early successional stage after abandonment while the other three types formed later successional stages with their distribution determined by the soil water content and total P.It can be concluded that the selection of appropriate species for introduction to accelerate succession should be determined by the local conditions and especially the total P concentration and soil water content.

  2. Linking the soil moisture distribution pattern to dynamic processes along slope transects in the Loess Plateau, China.

    Science.gov (United States)

    Wang, Shuai; Fu, Bojie; Gao, Guangyao; Zhou, Ji; Jiao, Lei; Liu, Jianbo

    2015-12-01

    Soil moisture pulses are a prerequisite for other land surface pulses at various spatiotemporal scales in arid and semi-arid areas. The temporal dynamics and profile variability of soil moisture in relation to land cover combinations were studied along five slopes transect on the Loess Plateau during the rainy season of 2011. Within the 3 months of the growing season coupled with the rainy season, all of the soil moisture was replenished in the area, proving that a type stability exists between different land cover soil moisture levels. Land cover combinations disturbed the trend determined by topography and increased soil moisture variability in space and time. The stability of soil moisture resulting from the dynamic processes could produce stable patterns on the slopes. The relationships between the mean soil moisture and vertical standard deviation (SD) and coefficient of variation (CV) were more complex, largely due to the fact that different land cover types had distinctive vertical patterns of soil moisture. The spatial SD of each layer had a positive correlation and the spatial CV exhibited a negative correlation with the increase in mean soil moisture. The soil moisture stability implies that sampling comparisons in this area can be conducted at different times to accurately compare different land use types.

  3. Land degradation, government subsidy, and smallholders' conservation decision:the case of the loess plateau in China

    Institute of Scientific and Technical Information of China (English)

    SHI Min-jun(石敏俊); CHEN Kevin

    2004-01-01

    Land degradation is one of the severe environmental problems in China. In order to combat land degradation, a soil conservation program was introduced since 2000 to reduce soil erosion by converting slope-cultivated land into forestry and pasture. This paper represents the first systematic attempt to investigate the impact of the soil conservation program on land degradation in the loess plateau. The results indicate that the soil conservation program to convert slope fields into forest or pasture is an effective way to combat soil erosion. However, a subsidy that is higher than profit of land use activity of slope fields before their conversion into forest and pasture is needed to encourage farmers to join the conservation program. A policy measure to encourage and assist farmers to develop sedentary livestock by using crops produced from fields as well as fodder and forage grass from the converted slope fields might contribute to combat soil erosion. Increase in off-farm job opportunities may encourage households to reduce cultivation in slope fields. That implies a policy measure to encourage rural urbanization might contribute to combat soil erosion.

  4. Evaluating sustainability of cropland use in Yuanzhou county of the Loess plateau, China using an emergy-based ecological footprint.

    Science.gov (United States)

    Bai, Xiaomei; Wen, Zhongming; An, Shaoshan; Li, Bicheng

    2015-01-01

    Evaluating the sustainability of cropland use is essential for guaranteeing a secure food supply and accomplishing agriculture sustainable development. This study was conducted in the ecologically vulnerable Loess Plateau region of China to evaluate the sustainability of cropland use based on an ecological footprint model that integrates emergy analysis. One modified method proposed in 2005 is known as the emergetic ecological footprint (EEF). We enhanced the method by accounting for both the surface soil energy in the carrying capacity calculation and the net topsoil loss for human consumption in the EF calculation. This paper evaluates whether the cropland of the study area was overloaded or sustainably managed during the period from 1981 to 2009. Toward this end, the final results obtained from EEF were compared to conventional EF and previous methods. The results showed that the cropland of Yuanzhou County has not been used sustainably since 1983, and the conventional EF analysis provided similar results. In contrast, a deficit did not appear during this time period when previous calculation methods of others were used. Additionally, the ecological sustainable index (ESI) from three models indicated that the recently used cropland system is unlikely to be unsustainable. PMID:25738289

  5. Evaluating sustainability of cropland use in Yuanzhou county of the Loess plateau, China using an emergy-based ecological footprint.

    Directory of Open Access Journals (Sweden)

    Xiaomei Bai

    Full Text Available Evaluating the sustainability of cropland use is essential for guaranteeing a secure food supply and accomplishing agriculture sustainable development. This study was conducted in the ecologically vulnerable Loess Plateau region of China to evaluate the sustainability of cropland use based on an ecological footprint model that integrates emergy analysis. One modified method proposed in 2005 is known as the emergetic ecological footprint (EEF. We enhanced the method by accounting for both the surface soil energy in the carrying capacity calculation and the net topsoil loss for human consumption in the EF calculation. This paper evaluates whether the cropland of the study area was overloaded or sustainably managed during the period from 1981 to 2009. Toward this end, the final results obtained from EEF were compared to conventional EF and previous methods. The results showed that the cropland of Yuanzhou County has not been used sustainably since 1983, and the conventional EF analysis provided similar results. In contrast, a deficit did not appear during this time period when previous calculation methods of others were used. Additionally, the ecological sustainable index (ESI from three models indicated that the recently used cropland system is unlikely to be unsustainable.

  6. Carbon Storage Patterns of Caragana korshinskii in Areas of Reduced Environmental Moisture on the Loess Plateau, China

    Science.gov (United States)

    Gong, Chunmei; Bai, Juan; Wang, Junhui; Zhou, Yulu; Kang, Tai; Wang, Jiajia; Hu, Congxia; Guo, Hongbo; Chen, Peilei; Xie, Pei; Li, Yuanfeng

    2016-07-01

    Precipitation patterns are influenced by climate change and profoundly alter the carbon sequestration potential of ecosystems. Carbon uptake by shrubbery alone accounts for approximately one-third of the total carbon sink; however, whether such uptake is altered by reduced precipitation is unclear. In this study, five experimental sites characterised by gradual reductions in precipitation from south to north across the Loess Plateau were used to evaluate the Caragana korshinskii’s functional and physiological features, particularly its carbon fixation capacity, as well as the relationships among these features. We found the improved net CO2 assimilation rates and inhibited transpiration at the north leaf were caused by lower canopy stomatal conductance, which enhanced the instantaneous water use efficiency and promoted plant biomass as well as carbon accumulation. Regional-scale precipitation reductions over a certain range triggered a distinct increase in the shrub’s organic carbon storage with an inevitable decrease in the soil’s organic carbon storage. Our results confirm C. korshinskii is the optimal dominant species for the reconstruction of fragile dryland ecosystems. The patterns of organic carbon storage associated with this shrub occurred mostly in the soil at wetter sites, and in the branches and leaves at drier sites across the arid and semi-arid region.

  7. Soil moisture influenced the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau

    Directory of Open Access Journals (Sweden)

    Y. Zhang

    2015-01-01

    Full Text Available Temperature sensitivity of SOC mineralization (Q10 determines how strong the feedback from global warming may be on the atmospheric CO2 concentration, thus understanding the factors influencing the interannual variation in Q10 is important to accurately estimate the local soil carbon cycle. In situ SOC mineralization was measured using an automated CO2 flux system (Li-8100 in long-term bare fallow soil in the Loess Plateau (35° 12' N, 107° 40' E in Changwu, Shaanxi, China form 2008 to 2013. The results showed that the annual cumulative SOC mineralization ranged from 226 to 298 g C m−2 y−1 (mean =253 g C m−2 y−1; CV =13%, annual Q10 ranged from 1.48 to 1.94 (mean =1.70; CV =10%, and annual soil moisture content ranged from 38.6 to 50.7% WFPS (mean =43.8% WFPS; CV =11%, which were mainly affected by the frequency and distribution of precipitation. Annual Q10 showed a negative quadratic correlation with soil moisture. In conclusion, understanding of the relationships between interannual variation in Q10 of SOC mineralization, soil moisture and precipitation is important to accurately estimate the local carbon cycle, especially under the changing climate.

  8. Wheat Grain Yield and Yield Stability in a Long-Term Fertilization Experiment on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    HAO Ming-De; FAN Jun; WANG Quan-Jiu; DANG Ting-Hui; GUO Sheng-Li; WANG Ji-Jun

    2007-01-01

    To provide a scientific basis for sustainable land management,a 20-year fertility experiment Was conducted in Changwu County,Shaanxi Province,China to investigate the effects of long-term application of chemical fertilizers on wheat grain yield and yield stability on the Loess Plateau using regression and stability analysis.The experiment consisted of 17fertilizer treatments.containing the combinations of different N and P levels,with three replications arranged in a randomized complete block design.Nitrogen fertilizer was applied as urea,and P was applied as calcium superphosphate.Fertilizer rates had a large effect on the response of wheat yield to fertilization.Phosphorus,combined with N,increased yield significantly(P≤0.01).In the unfertilized control and the N or P sole application treatments,wheat yield had a declining trend although it was not statistically significant.Stability analysis combined with the trend analysis indicated that integrated use of fertilizer N and P was better than their sole application in increasing and sustaining the productivity of rainfed winter wheat.

  9. Long-term effects of fertilizer on soil enzymatic activity of wheat field soil in Loess Plateau, China.

    Science.gov (United States)

    Hu, Weigang; Jiao, Zhifang; Wu, Fasi; Liu, Yongjun; Dong, Maoxing; Ma, Xiaojun; Fan, Tinglu; An, Lizhe; Feng, Huyuan

    2014-12-01

    The effects of long-term (29 years) fertilization on local agro-ecosystems in the Loess Plateau of northwest China, containing a single or combinations of inorganic (Nitrogen, N; Phosphate, P) and organic (Mature, M Straw, S) fertilizer, including N, NP, SNP, M, MNP, and a control. The soil enzymes, including dehydrogenase, urease, alkaline phosphatase, invertase and glomalin, were investigated in three physiological stages (Jointing, Dough, and Maturity) of wheat growth at three depths of the soil profile (0-15, 16-30, 31-45 cm). We found that the application of farmyard manure and straw produced the highest values of soil enzymatic activity, especially a balanced applied treatment of MNP. Enzymatic activity was lowest in the control. Values were generally highest at dough, followed by the jointing and maturity stages, and declined with soil profile depth. The activities of the enzymes investigated here are significantly correlated with each other and are correlated with soil nutrients, in particular with soil organic carbon. Our results suggest that a balanced application of fertilizer nutrients and organic manure (especially those containing P) has positive effects on multiple soil chemical parameters, which in turn enhances enzyme activity. We emphasize the role of organic manure in maintaining soil organic matter and promoting biological activity, as its application can result in a substantial increase in agricultural production and can be sustainable for many years.

  10. [Characteristics of evapotranspiration and crop coefficient of agroecosystems in semi-arid area of Loess Plateau, Northwest China].

    Science.gov (United States)

    Yang, Fu-Lin; Zhang, Qiang; Wang, Run-Yuan; Wang, Sheng; Yue, Ping; Wang, He-Ling; Zhao, Hong

    2013-05-01

    Evapotranspiration (ET) is an important component of ground surface energy balance and water balance, and closely related to water cycle. By using eddy covariance technique, this paper studied the ET characteristics of agroecosystems in the semi-arid area of Loess Plateau in growth season (from April to September), 2010, and analyzed the relationships between crop coefficient and environmental factors. During the observation period, the diurnal variation of latent heat flux (LE) in each month was similar to single-peak curve, and the peak value (151.4 W x m(-2)) occurred in August. The daytime energy partitioning manner showed a significant seasonal variation, with LE/R(n) heat flux) from April to June, and LE/R(n) > H/R(n) from July to September. The daily ET rate also showed a significant seasonal variation, with the maximum of 4.69 mm x d(-1). The wind speed (W(s)), relative humidity (RH), soil water content (theta), and atmospheric vapor pressure deficit (D) were the major factors affecting the crop coefficient K(c) which was exponentially decreased with increasing W(s), exponentially increased with increasing RH and theta, and linearly decreased with increasing D.

  11. [Impact of micro-landform on grassland plant comniunity structure and function in the hilly Loess Plateau region, China].

    Science.gov (United States)

    Ru, Hai-li; Zhang, Hai-dong; Jiao, Feng; Xue, Chao-yu; Guo, Mei-li

    2016-01-01

    In order to analyze the impact of micro-landform on grassland plant community structure and function, species composition, aboveground and belowground biomass, and annual fine root production at different slope aspects (sunny slope and shady slope) and different slope positions (top, upper, middle and lower) were investigated in the hilly Loess Plateau region. The results showed that grassland communities were mainly composed of plants species belonging to Compositae, Poaceae and Leguminosae. The aboveground and belowground biomass and annual fine root production of community were 164.12 g · m⁻², 1044.87 g · m⁻² and 731.77 g · m⁻² · a⁻¹, respectively. Aboveground biomass, belowground biomass and annual fine root production of community were in the order of shady slope > sunny slope > top slope. In shady slope, the biomass of community under different positions were in the order of lower > middle > upper > top, but it exhibited different orders in the sunny slope compared with shady slope. Fine root mainly concentrated in the 0-20 cm top soil layer and decreased with soil depth. The average turnover time of root was 0.75 a⁻¹ and changed with soil layers and micro-landform. PMID:27228589

  12. Long-term monitoring of rainfed wheat yield and soil water at the loess plateau reveals low water use efficiency.

    Directory of Open Access Journals (Sweden)

    Wei Qin

    Full Text Available Increasing crop yield and water use efficiency (WUE in dryland farming requires a quantitative understanding of relationships between crop yield and the water balance over many years. Here, we report on a long-term dryland monitoring site at the Loess Plateau, Shanxi, China, where winter wheat was grown for 30 consecutive years and soil water content (0-200 cm was measured every 10 days. The monitoring data were used to calibrate the AquaCrop model and then to analyse the components of the water balance. There was a strong positive relationship between total available water and mean cereal yield. However, only one-third of the available water was actually used by the winter wheat for crop transpiration. The remaining two-thirds were lost by soil evaporation, of which 40 and 60% was lost during the growing and fallow seasons, respectively. Wheat yields ranged from 0.6 to 3.9 ton/ha and WUE from 0.3 to 0.9 kg/m(3. Results of model experiments suggest that minimizing soil evaporation via straw mulch or plastic film covers could potentially double wheat yields and WUE. We conclude that the relatively low wheat yields and low WUE were mainly related to (i limited rainfall, (ii low soil water storage during fallow season due to large soil evaporation, and (iii poor synchronisation of the wheat growing season to the rain season. The model experiments suggest significant potential for increased yields and WUE.

  13. Long-term monitoring of rainfed wheat yield and soil water at the loess plateau reveals low water use efficiency.

    Science.gov (United States)

    Qin, Wei; Chi, Baoliang; Oenema, Oene

    2013-01-01

    Increasing crop yield and water use efficiency (WUE) in dryland farming requires a quantitative understanding of relationships between crop yield and the water balance over many years. Here, we report on a long-term dryland monitoring site at the Loess Plateau, Shanxi, China, where winter wheat was grown for 30 consecutive years and soil water content (0-200 cm) was measured every 10 days. The monitoring data were used to calibrate the AquaCrop model and then to analyse the components of the water balance. There was a strong positive relationship between total available water and mean cereal yield. However, only one-third of the available water was actually used by the winter wheat for crop transpiration. The remaining two-thirds were lost by soil evaporation, of which 40 and 60% was lost during the growing and fallow seasons, respectively. Wheat yields ranged from 0.6 to 3.9 ton/ha and WUE from 0.3 to 0.9 kg/m(3). Results of model experiments suggest that minimizing soil evaporation via straw mulch or plastic film covers could potentially double wheat yields and WUE. We conclude that the relatively low wheat yields and low WUE were mainly related to (i) limited rainfall, (ii) low soil water storage during fallow season due to large soil evaporation, and (iii) poor synchronisation of the wheat growing season to the rain season. The model experiments suggest significant potential for increased yields and WUE.

  14. Hydrologic Responses to Land Use Change in the Loess Plateau: Case Study in the Upper Fenhe River Watershed

    Directory of Open Access Journals (Sweden)

    Zhixiang Lu

    2015-01-01

    Full Text Available We applied an integrated approach to investigate the impacts of land use and land cover (LULC changes on hydrology at different scales in the Loess Plateau of China. Hydrological modeling was conducted for the LULC maps from remote sensing images at two times in the Upper Fenhe River watershed using the SWAT model. The main LULC changes in this watershed from 1995 to 2010 were the transformation of farmland into forests, grassland, and built-up land. The simulation results showed that forested land contributed more than any other LULC class to water yield, but built-up land had most impact due to small initial loss and infiltration. At basin scale, a comparison of the simulated hydrological components of two LULC maps showed that there were slight increases in average annual potential evapotranspiration, actual evapotranspiration, and water yield, but soil water decreased, between the two intervals. In subbasins, obvious LULC changes did not have clear impacts on hydrology, and the impacts may be affected by precipitation conditions. By linking a hydrological model to remote sensing image analysis, our approach of quantifying the impacts of LULC changes on hydrology at different scales provide quantitative information for stakeholders in making decisions for land and water resource management.

  15. Vertical Atmospheric Structure of the Late Summer Clear Days over the East Gansu Loess Plateau in China

    Institute of Scientific and Technical Information of China (English)

    WEI Zhigang; WEN Jun; LI Zhenchao

    2009-01-01

    In this paper, by using the sounding data collected in LOPEX05, we have analyzed the vertical atmospheric structure and boundary layer characteristics of temperature and humidity in the late summer over the east Gansu loess plateau. The results show that the bottom of the stratosphere is at about 16 500 m and varies between 14 000 m and 18 000 m above the ground. The center of the westerly jet is located between 8300 m and 14 300 m above the ground and its direction moves between 260° and 305°. There is an inverse humidity layer at about 3000 m height above the ground. The maximum of the air temperature occurs at 1700 LST in the layer below 800 m above the ground. The inversion layer is relatively thick. The time that the maximum of the vapor occurs is not the same for different layers. The depth of the atmospheric boundary layer can reach about 1000 m and the depth of the stable boundary layer can be 650 m.

  16. Relation between Growth and Vertical Distribution of Fine Roots and Soil Density in the Weibei Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhong; Li Peng; Xue Wenpeng; Guo Shengwu

    2006-01-01

    The influence of woodland soil bulk density on the growth and distribution of fine root system of main planting tree species in the Weibei Loess Plateau was investigated by means of pot culture and field survey.Results indicated that in the woodland of Pinus tabulaeformis,soil bulk density increased with the depth at different sites,while in the woodland of Robinia pseudoacacia,soil bulk density was higher than that in P.tabulaeformis,and there was no clear difference across the profile.Further analysis implied that there existed negative correlations between soil bulk density and fine root length in the woodland of P.tabulaeformis.Results from pot culture indicated that although the effects of pot culture media on the free root growth and development of different tree species seedlings were different,all treated seedlings grew better in the soil matter with medium bulk density and porosity and with the biggest biomass.Bulk density of pot culture media had clear effects on the growth and development of P.tabulaeformis and R.pseudoacacia seedling roots,especially on the former,whereas it had little effect on that of Platycladus orientalis and Prunus armeniaca var.ansu,whose fine root biomass changed little in different pot culture media.

  17. Diurnal Course of Gas Exchange and Water Use Efficiency of Platycladus orientalis in the Semiarid Region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Tian Jinghui; He Kangning; Wang Baitian; Guo Jianghong; Zhang Weiqiang; Yin Jing

    2006-01-01

    The daily gas exchange,stomatal conductance,and water use efficiency of Platycladus orientalis in the test field of Fangshan county of Shanxi Province in the semiarid region of the Loess Plateau were measured with portable Li-6200 gas analysis system in natural conditions.The results showed that the diurnal course of net photosynthetic rate displayed a two-peak pattern,that of stomatal conductance displayed a hollow pattern,and that of transpiration rate displayed a signal-peak pattern.Water use efficiency culminated in the early morning.On the basis of two criteria of stomatal limitation of photosynthesis suggested by Farquhar and Sharkey,the predominant limiting factor of photosynthesis was the stomatal conductance of stomatal limitation in the morning (10:00-12:00).However,the midday depression of photosynthesis at noon (12:00-14:00) and the decrease in photosynthesis in the afternoon (16:00-18:00) were the results of nonstomatal limitation,such as low carboxylation capacity of the leaf mesophyll.

  18. Impact of the Loess Plateau on the atmospheric boundary layer structure and air quality in the North China Plain: A case study

    International Nuclear Information System (INIS)

    The North China Plain (NCP), to the east of the Loess Plateau, experiences severe regional air pollution. During the daytime in the summer, the Loess Plateau acts as an elevated heat source. The impacts of such a thermal effect on meteorological phenomena (e.g., waves, precipitation) in this region have been discussed. However, its impacts on the atmospheric boundary layer structure and air quality have not been reported. It is hypothesized that the thermal effect of the Plateau likely modulates the boundary layer structure and ambient concentrations of pollutants over the NCP under certain meteorological conditions. Thus, this study investigates such effect and its impacts using measurements and three-dimensional model simulations. It is found that in the presence of daytime westerly wind in the lower troposphere (∼ 1 km above the NCP), warmer air above the Loess Plateau was transported over the NCP and imposed a thermal inversion above the mixed boundary layer, which acted as a lid and suppressed the mixed layer growth. As a result, pollutants accumulated in the shallow mixed layer and ozone was efficiently produced. The downward branch of the thermally-induced Mountain-Plains Solenoid circulation over the NCP contributed to enhancing the capping inversion and exacerbating air pollution. Previous studies have reported that low mixed layer, a factor for elevated pollution in the NCP, may be caused by aerosol scattering and absorption of solar radiation, frontal inversion, and large scale subsidence. The present study revealed a different mechanism (i.e., westerly warm advection) for the suppression of the mixed layer in summer NCP, which caused severe O3 pollution. This study has important implications for understanding the essential meteorological factors for pollution episodes in this region and forecasting these severe events. - Highlights: • Low mixed layer exacerbates air pollution over the North China Plain (NCP) • Warm advection from the Loess Plateau

  19. Impact of the Loess Plateau on the atmospheric boundary layer structure and air quality in the North China Plain: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiao-Ming, E-mail: xhu@ou.edu [Center for Analysis and Prediction of Storms, and School of Meteorology, University of Oklahoma, Norman, OK 73072 (United States); Ma, ZhiQiang, E-mail: zqma@ium.cn [Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089 (China); Lin, Weili [Key Laboratory for Atmospheric Chemistry, Center for Atmospheric Watch and Services, Chinese Academy of Meteorological Sciences, Beijing, 100081 (China); Zhang, Hongliang; Hu, Jianlin [Department of Civil and Environmental Engineering, University of California, Davis, CA 95616 (United States); Wang, Ying; Xu, Xiaobin [Key Laboratory for Atmospheric Chemistry, Center for Atmospheric Watch and Services, Chinese Academy of Meteorological Sciences, Beijing, 100081 (China); Fuentes, Jose D. [Department of Meteorology, Pennsylvania State University, University Park, PA 16802 (United States); Xue, Ming [Center for Analysis and Prediction of Storms, and School of Meteorology, University of Oklahoma, Norman, OK 73072 (United States)

    2014-11-15

    The North China Plain (NCP), to the east of the Loess Plateau, experiences severe regional air pollution. During the daytime in the summer, the Loess Plateau acts as an elevated heat source. The impacts of such a thermal effect on meteorological phenomena (e.g., waves, precipitation) in this region have been discussed. However, its impacts on the atmospheric boundary layer structure and air quality have not been reported. It is hypothesized that the thermal effect of the Plateau likely modulates the boundary layer structure and ambient concentrations of pollutants over the NCP under certain meteorological conditions. Thus, this study investigates such effect and its impacts using measurements and three-dimensional model simulations. It is found that in the presence of daytime westerly wind in the lower troposphere (∼ 1 km above the NCP), warmer air above the Loess Plateau was transported over the NCP and imposed a thermal inversion above the mixed boundary layer, which acted as a lid and suppressed the mixed layer growth. As a result, pollutants accumulated in the shallow mixed layer and ozone was efficiently produced. The downward branch of the thermally-induced Mountain-Plains Solenoid circulation over the NCP contributed to enhancing the capping inversion and exacerbating air pollution. Previous studies have reported that low mixed layer, a factor for elevated pollution in the NCP, may be caused by aerosol scattering and absorption of solar radiation, frontal inversion, and large scale subsidence. The present study revealed a different mechanism (i.e., westerly warm advection) for the suppression of the mixed layer in summer NCP, which caused severe O{sub 3} pollution. This study has important implications for understanding the essential meteorological factors for pollution episodes in this region and forecasting these severe events. - Highlights: • Low mixed layer exacerbates air pollution over the North China Plain (NCP) • Warm advection from the Loess

  20. Spatial variability of soil hydraulic properties on a steep slope in the loess plateau of China Variabilidade espacial de propriedades hídricas do solo de uma encosta do "Loess Plateau" da China

    Directory of Open Access Journals (Sweden)

    Wei Hu

    2008-01-01

    Full Text Available The understanding of the structure of the spatial variability of soil surface hydraulic properties on steep slopes is important for modeling infiltration and runoff processes. The objective of this study was to investigate the spatial variability of these properties on a steep slope of the Loess Plateau in northwest China. A 9600 m² area was systematically sampled in a grid of 106 points spaced 10 m x 10 m. Hydraulic properties were determined with a disc infiltrometer under multiple pressure heads (-15, -9, -6, -3, 0 cm at each sample point. Classical and geo-statistical methods were used for data analysis. The results indicated that the variation of Gardner's a and hydraulic conductivities at all applied pressure heads was moderate and the heterogeneity for hydraulic conductivities increased as the applied pressure head increased. Along the slope, hydraulic conductivities generally decreased downwards, while the Gardner's a fluctuated slightly. The Gardner's a of the shaded aspect of the slope was greater than that of the sunny aspect. The hydraulic conductivities of the shaded aspect were greater at higher pressure heads as compared to the sunny aspect, but lower than those of the sunny aspect at lower pressure heads. Correlation analysis showed a negative correlation between hydraulic conductivity and soil organic matter and clay (A compreensão da estrutura da variabilidade especial das propriedades hidráulicas do solo de encostas íngremes é importante na modelagem dos processos de infiltração e de escoamento superficial da água. O objetivo deste estudo foi investigar a variabilidade destas propriedades em uma encosta íngreme do "Loess Plateau" do noroeste da China. Uma área de 9600 m² foi sistematicamente amostrada em um grid de 106 pontos espaçados de 10 m x 10 m. As propriedades hídricas foram determinadas com um infiltrômetro de disco operando sob múltiplas cargas hidráulicas (-15, -9, -6, -3, 0 cm em cada ponto de

  1. An applied research on remote sensing classification in the Loess Plateau%黄土高原遥感分类应用研究

    Institute of Scientific and Technical Information of China (English)

    刘咏梅; 汤国安; 李天文

    2003-01-01

    Due to complex terrain of the Loess Plateau, the classification accuracy is unsatisfactory when a single supervised classification is used in the remote sensing investigation of the sloping field. Taking the loess hill and gully area of northern Shaanxi Province as a test area, a research was conducted to extract sloping field and other land use categories by applying an integrated classification. Based on an integration of supervised classification and unsupervised classification,sampling method is remarkably improved. The results show that the classification accuracy is satisfactory by the method and is of critical significance in obtaining up-to-date information of the sloping field, which should be helpful in the state key project of converting farmland to forest and grassland on slope land in this area. This research sought to improve the application accuracy of image classification in complex terrain areas.

  2. Dust storms and loess accumulation on the Tibetan Plateau:A case study of dust event on 4 March 2003 in Lhasa

    Institute of Scientific and Technical Information of China (English)

    FANG Xiaomin; HAN Yongxiang; MA Jinghui; SONG Lianchun; YANG Shengli; ZHANG Xiaoye

    2004-01-01

    Whether the Tibetan Plateau is a significant dust source area is of great importance, because this is related to the understanding of sources, accumulation and environmental effects of dusts on the Tibetan Plateau and in the Far East-Pacific Ocean regions as well as to the evolution of coupling of the Tibetan Plateau and atmosphere-ocean continent exchange. Synoptic dynamics and remote sensing tracing of a dust storm on 3 to 5 March, 2003 in Lhasa on South Tibet demonstrate that the Tibetan Plateau possesses all factors and conditions of generating dust storms. Accom panied with this dust storm is a strong ascending stream on the Plateau which has raised various sizes of dust particles into different levels. The lifted coarse particles were largely fallen down and accumulated as loess on the eastern Tibetan Plateau, and the fine particles were translated by the west erly jet and subsided in the northern Pacific Ocean. The spatial-temporal distribution of dust-storms between years 1961 and 2000 on the Plateau shows that dust-storms mainly occur in winter and early spring with high frequency, and the path of dust storm moves gradually from south to north, which is closely coupled with the northward moving of the westerly jet from winter to spring over the Tibetan Plateau. Compared with other twelve dust source areas in China, the Tibetan Plateau is one of the key dust source areas for the long-distance transport because its high occurring frequency and elevation cause fine particles easily to be lifted into the zone of the westerly jet.

  3. Assessing the effects of changes in land use and climate on runoff and sediment yields from a watershed in the Loess Plateau of China.

    Science.gov (United States)

    Zuo, Depeng; Xu, Zongxue; Yao, Wenyi; Jin, Shuangyan; Xiao, Peiqing; Ran, Dachuan

    2016-02-15

    The changes in runoff and sediment load in the Loess Plateau of China have received considerable attention owing to their dramatic decline during recent decades. In this paper, the impacts of land-use and climate changes on water and sediment yields in the Huangfuchuan River basin (HFCRB) of the Loess Plateau are investigated by combined usage of statistical tests, hydrological modeling, and land-use maps. The temporal trends and abrupt changes in runoff and sediment loads during 1954-2012 are detected by using non-parametric Mann-Kendall and Pettitt tests. The land-use changes between 1980 and 2005 are determined by using transition matrix analysis, and the effects of land-use and climate changes on water and sediment yields are assessed by using the Soil and Water Assessment Tool (SWAT) hydrological model and four scenarios, respectively. The results show significant decreasing trends in both annual runoff and sediment loads, whereas slightly decreasing and significantly increasing trends are detected for annual precipitation and air temperature, respectively. 1984 is identified as the dividing year of the study period. The land-use changes between 1980 and 2005 show significant effects of the Grain for Green Project in China. Both land-use change and climate change have greater impact on the reduction of sediment yield than that of water. Water and sediment yields in the upstream region show more significant decreases than those in the downstream region under different effects. The results obtained in this study can provide useful information for water resource planning and management as well as soil and water conservation in the Loess Plateau region. PMID:26657370

  4. Land-Use Conversion Changes the Multifractal Features of Particle-Size Distribution on the Loess Plateau of China.

    Science.gov (United States)

    Sun, Caili; Liu, Guobin; Xue, Sha

    2016-01-01

    Analyzing the dynamics of soil particle-size distributions (PSDs), soil nutrients, and erodibility are very important for understanding the changes of soil structure and quality after long-term land-use conversion. We applied multifractal Rényi spectra (Dq) and singularity spectra (f(α)) to characterize PSDs 35 years after conversions from cropland to shrubland with Caragana microphylla (shrubland I), shrubland with Hippophae rhamnoides (shrubland II), forested land, and grassland on the Loess Plateau of China. Multifractal parameters (capacity dimension (D₀), entropy dimension (D₁), D₁/D₀, correlation dimension (D₂), and Hölder exponent of order zero (α₀)) were used to analyze the changes of PSDs. Dq and f(α) characterized the PSDs well and sensitively represented the changes in PSDs after conversion. All types of land-use conversion significantly improved the properties of the topsoil (0-10 cm), but the effect of shrubland I and even forested land decreased with depth. All types of land-use conversion significantly increased D₁ and D₂ in the topsoil, and D₁ and D₂ in the 10-50 cm layers of shrubland II, forested land, and grassland and D₁ in the 50-100 cm layers of shrubland II were significantly higher relative to the control. Both D₁ and D₂ were positively correlated with the contents of soil nutrients and fine particles and were negatively correlated with soil erosion, indicating that D₁ and D₂ were potential indices for quantifying changes in soil properties and erosion. In conclusion, all types of land-use conversion significantly improved the conditions of the topsoil, but conversion from cropland to shrubland II, forested land, and grassland, especially shrubland II and grassland, were more effective for improving soil conditions in deeper layers. PMID:27527201

  5. Land-Use Conversion Changes the Multifractal Features of Particle-Size Distribution on the Loess Plateau of China.

    Science.gov (United States)

    Sun, Caili; Liu, Guobin; Xue, Sha

    2016-01-01

    Analyzing the dynamics of soil particle-size distributions (PSDs), soil nutrients, and erodibility are very important for understanding the changes of soil structure and quality after long-term land-use conversion. We applied multifractal Rényi spectra (Dq) and singularity spectra (f(α)) to characterize PSDs 35 years after conversions from cropland to shrubland with Caragana microphylla (shrubland I), shrubland with Hippophae rhamnoides (shrubland II), forested land, and grassland on the Loess Plateau of China. Multifractal parameters (capacity dimension (D₀), entropy dimension (D₁), D₁/D₀, correlation dimension (D₂), and Hölder exponent of order zero (α₀)) were used to analyze the changes of PSDs. Dq and f(α) characterized the PSDs well and sensitively represented the changes in PSDs after conversion. All types of land-use conversion significantly improved the properties of the topsoil (0-10 cm), but the effect of shrubland I and even forested land decreased with depth. All types of land-use conversion significantly increased D₁ and D₂ in the topsoil, and D₁ and D₂ in the 10-50 cm layers of shrubland II, forested land, and grassland and D₁ in the 50-100 cm layers of shrubland II were significantly higher relative to the control. Both D₁ and D₂ were positively correlated with the contents of soil nutrients and fine particles and were negatively correlated with soil erosion, indicating that D₁ and D₂ were potential indices for quantifying changes in soil properties and erosion. In conclusion, all types of land-use conversion significantly improved the conditions of the topsoil, but conversion from cropland to shrubland II, forested land, and grassland, especially shrubland II and grassland, were more effective for improving soil conditions in deeper layers.

  6. Pollen record from red clay sequence in the central Loess Plateau between 8.10 and 2.60 Ma

    Institute of Scientific and Technical Information of China (English)

    MA Yuzhen; WU Fuli; FANG Xiaomin; LI Jijun; AN Zhisheng; WANG Wei

    2005-01-01

    The Late Miocene and Pliocene are the key periods for understanding the origin and development of the present Asian monsoon circulations and ecologic environments. Here we present a pollen record from Chaona Red Clay section located in the central Loess Plateau in attempt to establish the histories of vegetation and associated climate changes between 8.10 and 2.60 Ma. Our results show that Gramineae-dominated woodland-grasslands developed in this region with Cedrus- and Pinus-characterized montane coniferous forests distributing in higher elevations from 8.10 to 6.73 Ma, probably suggesting a semi-humid climate in a warm-temperate zone. A subsequent expansion of Ulmus- dominated deciduous forests and a synchronous increase of Gramineae-dominated grassland reflect a warmer and more humid climate between 6.73 and 5.67 Ma. The vegetation changed to an Artemisia- and Gramineae-characterized steppe in lower elevations and to a coniferous forest in higher elevations from 5.67 to 3.71 Ma, implying probably a warm and semiarid climate in lowland and hill, and a colder and moister climate in mountain. During this period, a considerable warmer and more humid climate occurred between 4.61 and 4.07 Ma as indicated by pollen assemblages. The period between 3.71 and 2.58 Ma was characterized by the disappearance of Cedrus and Tsuga and also by an abrupt expansion of Cupressaceae, reflecting a drastic enhancement of monsoon-related climatic seasonality.

  7. Sustained high magnitude erosional forcing generates an organic carbon sink: Test and implications in the Loess Plateau, China

    Science.gov (United States)

    Li, Y.; Quine, T. A.; Yu, H. Q.; Govers, G.; Six, J.; Gong, D. Z.; Wang, Z.; Zhang, Y. Z.; Van Oost, K.

    2015-02-01

    Humans are now the most important geomorphic agent on the planet and accelerated erosion in agricultural landscapes results in high magnitude lateral organic carbon (OC) fluxes and significant perturbation of the land-ocean carbon flux. Nevertheless, the net effect of these lateral carbon fluxes on the C cycle is poorly constrained and there is no consensus as to whether they drive a net source or net sink of atmospheric CO2. Here, we test the hypothesis that, under sustained erosional forcing, soil carbon stocks on hillslopes reach a new equilibrium state in which all carbon exported with erosion is replaced; and, therefore, erosion results in a net sink for atmospheric CO2 at the scale of eroding hillslopes. The evidence from our study site, in the Loess Plateau of China, is consistent with this hypothesis. Despite net export of OC equivalent to ca. 10% NPP, we found that all of the eroded OC was replaced and, therefore, that the sink strength was equal to the C export rate. This sets the upper limit of the erosion-induced sink term at the scale of whole watershed. The fate of the exported carbon in reservoirs, floodplains, riverbeds and the ocean ultimately controls the watershed-scale sink strength. Nevertheless, the full replacement observed here suggests that erosion does not induce a C source, irrespective of the fate of the exported carbon, at least for high-input agricultural systems. Finally, we propose that assessment of the C cycle perturbation associated with erosion-induced lateral C fluxes must be made an integral part of accounting mechanisms for climate change mitigation strategies that are based on land use change and C sequestration in terrestrial environments.

  8. The effects of land use and its patterns on soil properties in a small catchment of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Due to relatively strong human activities in the hilly area of Loess Plateau, the natural vegetation has been destroyed, and landscapepattern based on agricultural land matrix was land use mosaic composing of shrub land, grassland, woodland and orchard.This pattern has animportant effect on soil moisture and soil nutrients.The Danangou catchment, a typical small catchment, was selected to study the effects ofland use and its patterns on soil moisture and nutrients in this paper.The results are as follows: The comparisons of soil moisture among sevenland uses for wet year and dry year were performed: (1) the average of soil moisture content for whole catchment was 12.11% in wet year,while it was 9.37% in dry year; (2) soil moisture among seven land uses was significantly different in dry year, but not in wet year; (3) fromwet year to dry year, the profile type of soil moisture changed from decreasing type to fluctuation-type and from fluctuant type to increasingtype; (4) the increasing trend in soil moisture from the top to foot of hillslope occurred in simple land use along slope, while complicateddistribution of soil moisture was observed in multiple land uses along slope.The relationships between soil nutrients and land uses and landscapepositions were analysed: ( 1 ) five nutrient contents of soil organic matter (SOM), total N (TN), available N (AN), total P (TP) andavailable P (AP) in hilly area were lower than that in other areas.SOM content was less than 1%, TN content less than 0.07%, and TPcontent between 0.05% and 0.06%; (2) SOM and TN contents in woodland, shrub land and grassland were significantly higher than that infallow land and cropland, and higher level in soil fertility was found in crop-fruit intercropping land among croplands; (3) soil nutrientdistribution and responses to landscape positions were variable depending on slope and the location of land use types.

  9. A case study of spatial heterogeneity of soil moisture in the Loess Plateau,western China:A geostatistical approach

    Institute of Scientific and Technical Information of China (English)

    BI Huaxing; LI Xiaoyin; LIU Xin; GUO Mengxia; LI Jun

    2009-01-01

    Soil moisture distribution shows highly variation both spatially and temporally.This study assesses the spatial heterogeneity of soil moisture on a hill-slope scale in the Loess Plateau in West China by using a geostatistical approach.Soil moisture was measured by time-domain reflectometry (TDR) in 313 samples.Two kinds of sampling scales were used (2 × 2 m and 20 × 20m) at two soil layers (0-30 cm and 30-450 cm).The general characteristics of soil moisture were analyzed by a classical statistics method,and the spatial heterogeneity of soil moisture was analyzed using a geostatistical approach.The results showed that the spherical model is the best-fit model to simulate soil moisture on the experimental hill-slope.The parameters of this model indicated that the spatial dependence of soil moisture in the selected hill-slope was moderate.Even the 2 × 2 m sampling scale was too coarse to show the detailed spatial variances of soil moisture in this area.The dependent distance increased from 27.4 m to 494.16 m as the sampling scale became coarse (from 2 ×2 m to 20 × 20 m).A map of soil moisture was generated by using original soil moisture data and interpolated values determined by the Kriging method.The average soil moisture (area weighted) in the different layers of soil was calculated on the basis of this map (10.94% for the 0-30 cm soil layer,11.88% for the 30-60 em soil layer).This average soil moisture is lower than the corresponding average effective soil moisture,which suggests that the soil moisture is not sufficient to support vegetation in this area.

  10. Effects of low-temperature oxidation on natural remanent magnetization of Chinese loess

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and 200℃, (1) Hc and Hcr significantly decrease while Mrs and Ms remain stable; (2) concentration of the multi-domain (MD) grains increases while that of superparamagnetic (SP) grains decreases; and (3) there exists the abnormal behavior of the thermal demagnetization in the natural remanent magnetization (NRM). In addition, the corresponding changes in all these parameters are gradually muted with the increase of the pedogenesis degree. The results indicate that the observed alteration probably relates to reducing processes caused by the burning of the organic matter in samples. Before the thermal treatment, the MD grains in loess samples had been partially altered in nature by low-temperature oxidization (LTO). This CRM can be sufficiently attenuated or even removed by the reducing process between 100 and 200℃ during the thermal treatment and has no apparent harmful effects on the characteristic remanent magnetization (ChRM) between 300 and 500℃.

  11. Production Performance of Root Systems of Four Forage Legume Species and Their Development Characteristics in Loess Plateau,China

    Institute of Scientific and Technical Information of China (English)

    Zhang; Jianquan; Zhang; Jiyu; Wang; Yanrong; Xie; Wengang; Li; Juncheng

    2014-01-01

    Production performance of four forage legumes species of Medicago sativa,Onobrychis viciifolia,Lotus corniculatus and Galega officinalis were determined,including plant height,above-ground biomass per unit area,tillers per unit area,fertile tillers per unit area,shoot /leaf ratio and fresh /dry matter weight ratio,and the distribution characteristics of their root systems in 0- 100 cm soil layers with 10 cm interval were studied. Results showed that the average aboveground fresh biomass(4 a and 5 a) of four forage legumes species successively were L. corniculatus > M. sativa > O. viciifolia > G. officinalis. The average plant heights in two years successively were O. viciifolia > M. sativa > G. officinalis > L. corniculatus. Tillers per unit area of four forage legume species in two years successively were M. sativa > L. corniculatus > O. viciifolia > G. officinalis. Fertile tillers per unit area in two years were O. viciifolia > M. sativa > L. corniculatus > G. officinalis. Average shoot /leaf ratio in two years were G. officinalis > M. sativa > O. viciifolia > L. corniculatus. Average moisture contents of four forage legume species in two years successively were G. officinalis > L. corniculatus > M. sativa = O. viciifolia. The distribution characteristics of root systems of four forage legumes species in 0- 100 cm soil layers were as follows: the root weights of M. sativa in 0- 40 cm soil layers accounted for about 98. 3% of total root weight,that of O. viciifolia in 0- 30 cm soil layers was 85. 8%,that of L. corniculatus in 0- 10 cm soil layers was 80%,and that of G. officinalis in 0- 40 cm soil layers was 81. 4%. The results suggested that L. corniculatus was suited to plant in slighter degraded pasture to control water and soil erosion in early stage,G. officinalis with strong lateral roots was adapted to degraded grassland in the Loess Plateau where soil nutrient was poor,while O. viciifolia and M. sativa with potentially strong main root were fit for water

  12. Desert-steppe migration on the Loess Plateau at about 450 kaBP%黄土高原450kaBP前后荒漠草原大迁移研究

    Institute of Scientific and Technical Information of China (English)

    赵景波

    2005-01-01

    According to the field investigation, observation by an electronic microscope and x-ray identification and chemical analysis, desert-steppe migration in the Loess Plateau at about 450 kaBP was studied. The data show that gypsum illuvial horizon indicating the desert-steppe environment developed in the early stage of the formation of the fifth layer loess in Shaoling tableland in Chang'an and Bailu tableland in Xi'an of Shaanxi are situated in the southern Loess Plateau. This indicates that remarkable drying occurred, a large-scope migration of desert steppe took place toward south and the climate zone migrated 5 degrees in latitude to south which is the largest migration range indicated by geochemical indexes. The desert-steppe and more wild environment distributed widely on the Loess Plateau at that time. The development of gypsum also indicates that the climate changed at 450 kaBP from monsoon climate to nonmonsoon climate in the Loess Plateau, and the region was not affected by summer monsoon and was in the cold and dry environment of nonmonsoon climate. Annual mean precipitation was about 200 mm, 400 mm less at that time than at present.

  13. Geological hazards in loess terrain, with particular reference to the loess regions of China

    Science.gov (United States)

    Derbyshire, Edward

    2001-06-01

    The considerable morphodynamic energy provided by the continuing tectonic evolution of Asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt. Many of these environments are hazardous, threatening human occupation, health and livelihood, especially in regions of dense population such as the loess lands of north China. Dry loess can sustain nearly vertical slopes, being perennially under-saturated. However, when locally saturated, it disaggregates instantaneously. Such hydrocompaction is a key process in many slope failures, made worse by an underlying mountainous terrain of low-porosity rocks. Gully erosion of loess may yield very high sediment concentrations (>60% by weight). Characteristic vertical jointing in loess influences the hydrology. Enlarged joints develop into natural sub-surface piping systems, which on collapse, produce a "loess karst" terrain. Collapsible loess up to 20 m thick is common on the western Loess Plateau. Foundation collapse and cracked walls are common, many rapid events following periods of unusually heavy monsoonal rain. Slope failure is a major engineering problem in thick loess terrain, flow-slide and spread types being common. The results are often devastating in both urban and rural areas. An associated hazard is the damming of streams by landslides. The human population increases the landslide risk in China, notably through imprudent land-use practices including careless water management. A number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters, including fluorosis, cretinism, Kaschin-Beck Disease, Keshan Disease and goitre. The Chinese desert margins also have a major atmospheric dust problem. The effect of such dust upon human health in these extensive regions, including many large cities, has yet to be evaluated, but pneumoconiosis is thought to affect several

  14. A detailed post-IR IRSL chronology for the last interglacial soil at the Jingbian loess site (northern China)

    DEFF Research Database (Denmark)

    Buylaert, Jan-Pieter; Yeo, Eun-Young; Thiel, Christine;

    2015-01-01

    The chronology of dust deposition and climate during the last interglacial is poorly known on the Chinese Loess Plateau. Here, 51 samples were taken from the ~5 m S1 palaeosol (MIS5) at the desert marginal Jingbian site to develop what is currently the most detailed S1 chronology on the Plateau...... for S1 is ~150 g m-2 a-1, considerably higher than at many other sites but within the overall range of Loess Plateau estimates. The remarkably stable sediment accumulation at the site contrasts with a more complex record of environmental and monsoonal change recorded in grain-size and magnetic...

  15. Soil temperature and moisture sensitivities of soil C02 efflux before and after tillage in a wheat field of Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    Hongxing Zhang; Xiaoke Wang; Zongwei Feng; Junzhu Pang; Fei Lu; Zhiyun Ouyang; Hua Zheng; Wenzhao Liu; Dafeng Hui

    2011-01-01

    As a conventional farming practice, tillage has lasted for thousands of years in Loess Plateau, China.Although recent studies show that tillage is a prominent culprit to soil carbon loss in croplands, few studies have investigated the influences of tillage on the responses of soil CO2 effiux (SCE) to soil temperature and moisture.Using a multi-channel automated CO2 effiux chamber system, we measured SCE in situ continuously before and after the conventional tillage in a rain fed wheat field of Loess Plateau, China.The changes in soil temperature and moisture sensitivities of SCE, denoted by the Q10 value and linear regression slope respectively, were compared in the same range of soil temperature and moisture before and after the tillage.The results showed that, after the tillage, SCE increased by 1.2-2.2 times; the soil temperature sensitivity increased by 36.1%-37.5%; and the soil moisture sensitivity increased by 140%-166%.Thus, the tiUage-induced increase in SCE might partially be attributed to the increases in temperature and moisture sensitivity of SCE.

  16. Changes in Soil Hot-Water Extractable C, N and P Fractions During Vegetative Restoration in Zhifanggou Watershed on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    XUE Sha; LIPeng; LIU Guo-bin; LI Zhan-bin; ZHANG Chao

    2013-01-01

    The study was conducted in Zhifanggou Watershed, Shaanxi Province, China, to evaluate the effect of different vegetation types on hot-water extractable C, N and P fractions, with the aim to determine whether hot-water extractable fractions could be used as indicators of soil quality change in Loess Plateau. The six vegetation types established in 1975 were (i)Robinia pseudoacacia L., (ii)Caragana korshinkiiKom., (iii)Pinus tabulaeformis Carr., (iv)P. tabulaeformis-Amorpha fruticosaL., (v)R. pseudoacacia-A. fruticosa, and (vi) grassland. A cropped hillslope plot and aPlatycladus orientalis L. native forest plot were used as references. The results indicated that the conversion of native forest to cropland resulted in a signiifcant decline in the hot-water extractable C, N and P fractions. Hot-water extractable C, N, and P increased when cultivated land was revegetated, but after 30 years the amount of hot-water extractable C, N, and P in revegetated ifelds was still much lower compared to native forest. Hot-water extractable fractions increased more under mixed-forest than under pure-forest stands. Furthermore, there was a signiifcant correlation between the hot-water extractable fractions and soil chemical and microbiological properties. The results showed that hot-water extractable fractions could be used as indicators of soil quality change on the Loess Plateau.

  17. Performance of soil particle-size distribution models for describing deposited soils adjacent to constructed dams in the China Loess Plateau

    Science.gov (United States)

    Zhao, Pei; Shao, Ming-an; Horton, Robert

    2011-02-01

    Soil particle-size distributions (PSD) have been used to estimate soil hydraulic properties. Various parametric PSD models have been proposed to describe the soil PSD from sparse experimental data. It is important to determine which PSD model best represents specific soils. Fourteen PSD models were examined in order to determine the best model for representing the deposited soils adjacent to dams in the China Loess Plateau; these were: Skaggs (S-1, S-2, and S-3), fractal (FR), Jaky (J), Lima and Silva (LS), Morgan (M), Gompertz (G), logarithm (L), exponential (E), log-exponential (LE), Weibull (W), van Genuchten type (VG) as well as Fredlund (F) models. Four-hundred and eighty samples were obtained from soils deposited in the Liudaogou catchment. The coefficient of determination (R 2), the Akaike's information criterion (AIC), and the modified AIC (mAIC) were used. Based upon R 2 and AIC, the three- and four-parameter models were both good at describing the PSDs of deposited soils, and the LE, FR, and E models were the poorest. However, the mAIC in conjunction with R 2 and AIC results indicated that the W model was optimum for describing PSD of the deposited soils for emphasizing the effect of parameter number. This analysis was also helpful for finding out which model is the best one. Our results are applicable to the China Loess Plateau.

  18. Runoff and Sediment Yield Variations in Response to Precipitation Changes: A Case Study of Xichuan Watershed in the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    Tianhong Li

    2015-10-01

    Full Text Available The impacts of climate change on hydrological cycles and water resource distribution is particularly concerned with environmentally vulnerable areas, such as the Loess Plateau, where precipitation scarcity leads to or intensifies serious water related problems including water resource shortages, land degradation, and serious soil erosion. Based on a geographical information system (GIS, and using gauged hydrological data from 2001 to 2010, digital land-use and soil maps from 2005, a Soil and Water Assessment Tool (SWAT model was applied to the Xichuan Watershed, a typical hilly-gullied area in the Loess Plateau, China. The relative error, coefficient of determination, and Nash-Sutcliffe coefficient were used to analyze the accuracy of runoffs and sediment yields simulated by the model. Runoff and sediment yield variations were analyzed under different precipitation scenarios. The increases in runoff and sediment with increased precipitation were greater than their decreases with reduced precipitation, and runoff was more sensitive to the variations of precipitation than was sediment yield. The coefficients of variation (CVs of the runoff and sediment yield increased with increasing precipitation, and the CV of the sediment yield was more sensitive to small rainfall. The annual runoff and sediment yield fluctuated greatly, and their variation ranges and CVs were large when precipitation increased by 20%. The results provide local decision makers with scientific references for water resource utilization and soil and water conservation.

  19. 黄土高原水面蒸发量初步估算%A Preliminary Estimation of Water Surface Evaporation in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    贾莲莲; 王小江

    2013-01-01

    为了估算黄土高原的水面蒸发量,明确黄土高原干燥度指数的空间分异规律,收集了黄土高原及其周边地区共154站水面蒸发实测资料和216站降水资料,采用克里格插值法,对黄土高原的水面蒸发、干燥度指数进行了分析.结果显示:黄土高原多年平均水面蒸发量变化于1 107~3 308 mm,由东南至西北递增;遥感提取的黄土高原水体面积为1 326.48 km2,占黄土高原总面积的0.21%,黄土高原水体的年总蒸发量为26.28亿m3,占该区多年平均降水量的0.90%;黄土高原半湿润带、半干旱带以及干旱带所占面积比例分别为26.18%,53.73%和20.09%.研究结果对黄土高原水资源利用具有一定的参考价值.%In order to estimate the water surface evaporation and the spatial variation of drought index on the Loess Plateau,the data of 154 evaporation stations and 216 precipitation stations were collected across the Loess Plateau and the adjacent areas.The surface evaporation,drought index of the Loess Plateau were analyzed by using the Kriging interpolation method.The result show that annual average surface evaporation ranges from 1 107 mm to 3 308 mm,increases from southeast to the northwest by turns; water body area is 1 326.48 km2,accounting for 0.21% of total area,the total average annual water surface evaporation of water body was estimated to be 2.628× 109 m3 in Loess Plateau combining the evaporation data,accounting for 0.90% of the total annual average rainfall; the percentages of subhumid zone,semi-arid zone and arid zone are 26.18%,53.73% and 20.09%,respectively.The research result has an important reference for water resources utilization on the Loess Plateau.

  20. 黄土高原及周边地区土壤有机质对现代土壤磁化率的影响%Impact of soil organic matter on modern soil magnetic susceptibility in Loess Plateau and its surrounding areas

    Institute of Scientific and Technical Information of China (English)

    张博; 刘卫国

    2016-01-01

    Background, aim, and scope Magnetic susceptibility of soils can provide paleoclimatic information. In Chinese Loess Plateau, susceptibility enhancement is usually considered as a proxy of monsoon intensity. Several hypotheses were used to explain variations of this proxy. Here, we present a study on how soil magnetic susceptibility is related with soil organic matters. We analyzed magnetic susceptibility, organic carbon content, organic carbon isotopic composition, and C/N ratio of modern soils from Chinese Loess Plateau, in order to obtain the relationship between soil magnetic susceptibility and other parameters, as well as how soil organic matters affect soil magnetic susceptibility. Materials and methods Fifty modern soil samples were collected from the Loess Platform, forest areas at the Huangling and Huanglong Mount, and loess-desert area near the Tengger Desert. These soil samples represent modern soil types in the Loess Plateau. Samples were collected 2—3 cm below the surface. The sampling sites are at least 40 km away from any industrialized centers that could generate artificial, air-borne magnetic material. In this way, we minimized the effect of human and livestock activity. We tested magnetic susceptibility (χlf), organic carbon isotopic composition (δ13C), and organic carbon and nitrogen contents of these samples. Results The magnetic susceptibility varied from 26.6×10−8 m3∙kg−1 to 61.4×10−8 m3∙kg−1 for soils from the loess platform, and from 68.6×10−8 m3∙kg−1 to 107.5×10−8 m3∙kg−1 for soils from forest areas. The value of soil from forest areas is apparently higher than that from the loess platform. The magnetic susceptibility of soil samples from loess-desert area varied from 8.5×10−8 m3∙kg−1 to 44.4×10−8 m3∙kg−1.δ13C values of soil samples from the loess platform varied from−22‰to−24.4‰.δ13C values of soil samples from loess-desert area varied from−20.66‰to−24.69‰, whose range is

  1. Variations of deep soil moisture under different vegetation types and influencing factors in a watershed of the Loess Plateau, China

    Science.gov (United States)

    Fang, Xuening; Zhao, Wenwu; Wang, Lixin; Feng, Qiang; Ding, Jingyi; Liu, Yuanxin; Zhang, Xiao

    2016-08-01

    Soil moisture in deep soil layers is a relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the variations in deep soil moisture and its influencing factors at a moderate watershed scale is important to ensure the sustainability of vegetation restoration efforts. In this study, we focus on analyzing the variations and factors that influence the deep soil moisture (DSM) in 80-500 cm soil layers based on a soil moisture survey of the Ansai watershed in Yan'an in Shanxi Province. Our results can be divided into four main findings. (1) At the watershed scale, higher variations in the DSM occurred at 120-140 and 480-500 cm in the vertical direction. At the comparable depths, the variation in the DSM under native vegetation was much lower than that in human-managed vegetation and introduced vegetation. (2) The DSM in native vegetation and human-managed vegetation was significantly higher than that in introduced vegetation, and different degrees of soil desiccation occurred under all the introduced vegetation types. Caragana korshinskii and black locust caused the most serious desiccation. (3) Taking the DSM conditions of native vegetation as a reference, the DSM in this watershed could be divided into three layers: (i) a rainfall transpiration layer (80-220 cm); (ii) a transition layer (220-400 cm); and (iii) a stable layer (400-500 cm). (4) The factors influencing DSM at the watershed scale varied with vegetation types. The main local controls of the DSM variations were the soil particle composition and mean annual rainfall; human agricultural management measures can alter the soil bulk density, which contributes to higher DSM in farmland and apple orchards. The plant growth conditions, planting density, and litter water holding capacity of introduced vegetation showed significant relationships with the DSM. The results of this study are of practical significance for vegetation restoration strategies, especially

  2. Effect of Rotational Tillage on Soil Aggregates, Organic Carbon and Nitrogen in the Loess Plateau Area of China

    Institute of Scientific and Technical Information of China (English)

    HOU Xian-Qing; LI Rong; JIA Zhi-Kuan; HAN Qing-Fang

    2013-01-01

    In rain-fed semi-arid agroecosystems,continuous conventional tillage can cause serious problems in soil quality and crop production,whereas rotational tillage (no-tillage and subsoiling) could decrease soil bulk density,and increase soil aggregates and organic carbon in the 0-40 cm soil layer.A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon (SOC),total nitrogen (TN),water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia.Three tillage treatments were tested:no-tillage in year 1,subsoiling in year 2,and no-tillage in year 3 (NT-ST-NT); subsoiling in year 1,no-tillage in year 2,and subsoiling in year 3 (ST-NT-ST); and conventional tillage over years 1-3 (CT).Mean values of soil bulk density in 0-40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%,respectively,compared with CT,while soil total porosity was greatly improved.Rotational tillage increased SOC,TN,and water-stable aggregates in the 0-40 cm soil,with the greatest effect under ST-NT-ST.In 0-20 and 20-40 cm soils,the tillage effect was confined to the 2-0.25 mm size fraction of soil aggregates,and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage.No significant differences were detected in SOC and TN contents in the > 2 mm and < 0.25 mm aggregates among all treatments.In conclusion,rotational tillage practices could significantly increase SOC and TN levels,due to a fundamental change in soil structure,and maintain agroecosystem sustainability in the Loess Plateau area of China.

  3. Timing and Spatial Distribution of Loess in Xinjiang, NW China.

    Directory of Open Access Journals (Sweden)

    Yun Li

    Full Text Available Central Asia is one of the most significant loess regions on Earth, with an important role in understanding Quaternary climate and environmental change. However, in contrast to the widely investigated loess deposits in the Chinese Loess Plateau, the Central Asian loess-paleosol sequences are still insufficiently known and poorly understood. Through field investigation and review of the previous literature, the authors have investigated the distribution, thickness and age of the Xinjiang loess, and analyzed factors that control these parameters in the Xinjiang in northwest China, Central Asia. The loess sediments cover river terraces, low uplands, the margins of deserts and the slopes of the Tianshan Mountains and Kunlun Mountains and are also present in the Ili Basin. The thickness of the Xinjiang loess deposits varies from several meters to 670 m. The variation trend of the sand fraction (>63 μm grain-size contour can indicate the local major wind directions, so we conclude that the NW and NE winds are the main wind directions in the North and South Xinjiang, and the westerly wind mainly transport dust into the Ili basin. We consider persistent drying, adequate regional wind energy and well-developed river terraces to be the main factors controlling the distribution, thickness and formation age of the Xinjiang loess. The well-outcropped loess sections have mainly developed since the middle Pleistocene in Xinjiang, reflecting the appearance of the persistent drying and the present air circulation system. However, the oldest loess deposits are as old as the beginning of the Pliocene in the Tarim Basin, which suggests that earlier aridification occurred in the Tarim Basin rather than in the Ili Basin and the Junggar Basin.

  4. No apparent lock-in depth of the Laschamp geomagnetic excursion: Evidence from the Malan loess

    Institute of Scientific and Technical Information of China (English)

    ZHU Rixiang; LIU Qingsong; PAN Yongxin; DENG Chenglong; ZHANG Rui; WANG Xianfeng

    2006-01-01

    The first-order chronological framework of the long-term Chinese loess/paleosol sequences was based mainly on magnetostratigraphy. However, there remain arguments on the lock-in ages of the major geomagnetic reversals. This study systematically compared the stratigraphic locations of the Laschamp excursion and Henrich events (H4 at~39 ka and H5 at~48 ka) recorded by the Luochuan loess profile in the central Chinese Loess Plateau. Results show that the Lascchamp excursion is bracketed well by these two cold events, and the corresponding estimated age is between about 41.7-43.7 ka, which is close to the widely accepted age of ~40-41 ka for the excursion.Therefore, our new results do not suggest apparent lock-in effects in the last glacial Malan loess.

  5. Changes in soil organic carbon and total nitrogen in croplands converted to walnut-based agroforestry systems and orchards in southeastern Loess Plateau of China.

    Science.gov (United States)

    Lu, Sen; Meng, Ping; Zhang, Jinsong; Yin, Changjun; Sun, Shiyou

    2015-11-01

    Limited information is available on the effects of agroforestry system practices on soil properties in the Loess Plateau of China. Over the last decade, a vegetation restoration project has been conducted in this area by converting cropland into tree-based agroforestry systems and orchards to combat soil erosion and degradation. The objective of the present study was to determine the effects of land use conversion on soil organic carbon and total nitrogen in southeastern Loess Plateau. The experiment included three treatments: walnut intercropping system (AF), walnut orchard (WO), and traditional cropland (CR). After 7 years of continual management, soil samples were collected at 0-10, 10-30, and 30-50-cm depths for three treatments, and soil organic carbon (SOC) and total nitrogen (TN) were measured. Results showed that compared with the CR and AF treatments, WO treatment decreased both SOC and TN concentrations in the 0-50-cm soil profile. However, similar patterns of SOC and TN concentrations were observed in the AF and CR treatments across the entire profile. The SOC stocks at 0-50-cm depth were 5.42, 5.52, and 4.67 kg m(-2) for CR, AF, and WO treatments, respectively. The calculated TN stocks at 0-50-cm depth were 0.63, 0.62, and 0.57 kg m(-2) for CR, AF, and WO treatments, respectively. This result demonstrated that the stocks of SOC and TN in WO were clearly lower than those of AF and CR and that the walnut-based agroforestry system was more beneficial than walnut monoculture in terms of SOC and TN sequestration. Owing to the short-term intercropping practice, the changes in SOC and TN stocks were slight in AF compared with those in CR. However, a significant decrease in SOC and TN stocks was observed during the conversion of cropland to walnut orchard after 7 years of management. We also found that land use types had no significant effect on soil C/N ratio. These findings demonstrated that intercropping between walnut rows can potentially maintain

  6. Cold surges and dust events: Establishing the link between the East Asian Winter Monsoon and the Chinese loess record

    Science.gov (United States)

    Wyrwoll, Karl-Heinz; Wei, Junhong; Lin, Zhaohui; Shao, Yaping; He, Feng

    2016-10-01

    The Chinese loess/palaeosol succession is one of the most comprehensive and intensively studied archives of Neogene and Quaternary global palaeoclimate events. Its stratigraphic details are widely recognised to indicate close links to the history and function of the East Asian Winter Monsoon (EAWM) - one of the most active components of the Earth's climate system. But the formal meteorological links between the EAWM and dust emission, both in the present day and in the past, have not been established and with it, the veracity of the loess record as an indicator of the EAWM questioned. Here we show that present day major dust events over northern China, while largely occurring during spring, are nevertheless 'conditioned' by the strength of the preceding EAWM. We also demonstrate, for the first time, a close link between the occurrence of dust events and the strength of the EAWM. From these findings, linked to global-scale climate model simulations, we conclude that the Chinese loess succession provides a convincing proxy record of the strength of the East Asian Winter Monsoon.

  7. A Late Quaternary Climate Record Based on Multi-Proxies Analysis from the Jiaochang Loess Section in the Eastern Tibetan Plateau, China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We compared the stable carbon isotopic records from a loess transect of the Jiaochang in the eastern Tibetan Plateau, spanning the last ~21,000 years, with multiproxy data for pedogenesis,including magnetic susceptibility, clay fraction, Fed/Fet ratio, carbonate and total organic carbon content, in order to probe the mechanisms of δ13C values of organic matter and Late Quaternary climate variations in the eastern Tibetan Plateau. Our results indicate that there is no simple relationship between δ13C of organic matter and summer monsoon variations. The change in δ13C values of organic matter (in accordance with the ratios of C3 to C4 plants) results from the interaction among temperature, aridity and atmospheric pCO2 level. Drier climate and lower atmospheric pCO2 level contribute to positive carbon isotopic excursion, while negative carbon isotopic excursion is the result of lower temperature and increased atmospheric pCO2 level. Additionally, our results imply that the Tibetan monsoon may play an important role in climate system in the eastern Tibet Plateau,which specifically reflects frequently changing climate in that area. The results provide new insights into the forcing mechanisms on both the δ13C values of organic matter and the local climate system.

  8. Migration of 99Tc in unsaturated Chinese loess under artificial rainfall condition: an in situ test

    International Nuclear Information System (INIS)

    The migration of 99Tc in unsaturated Chinese loess under artificial rainfall condition was investigated in situ. Water suckers were buried at different depths under the bottom of an experimental pit of 2 m x 2 m x 1 m (deep). Quartz containing 3H and 99Tc was introduced into the experimental pit to an area of 40 cm x 40 cm and the pit was backfilled to a thickness of 30 cm. An artificial rainfall of 5 mm/h was applied to the experimental pit 4 h a day for 3 months. Moisture water samples were sucked with the help of a vacuum pumping system and the activity of 3H and 99Tc in the samples was determined. Breakthrough curves of 3H and 99Tc indicated that 99Tc was slightly retarded. The calculated average apparent distribution coefficient of 99Tc in the medium was (1.98 ± 0.42) x 10-2 ml/g. (orig.)

  9. Identification of the deposited layers in landslides reservoir and investigation of the sediment yields during the later sixteenth century on the Hill Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    LONG Yi; ZHANG XinBao; LI Min; LI Mian; ZHANG YunQi

    2008-01-01

    There are many sediment trapping reservoirs in the Hill Loess Plateau. The Huangtuwa small catchment is selected as a research field where samples were collected in a sediment deposit profile with a vertical length of 12.73 m. By the variation of fine particle content and pollen concentration, 54 flood couples were identified. Taking the freeze-thawing disturbed texture as the sign of the latest flood couple in a year, it is ascertained that those 54 floods should happen in 31 years. Using pyramid volume calculation formula, the sediment yields of flood ranged between 716-30376 t. km-2. The average the Huaining River, the erosion rate in the Huangtuwa region 450 years ago was similar to the modern erosion rate. In the period from the 27th year to the 31st year, the average annual sediment yield incatchment since the landslide disaster, where vegetation had rehabilitated already, caused very severe soil erosion in the catchment.

  10. Vertical profiles of soil water content as influenced by environmental factors in a small catchment on the hilly-gully Loess Plateau.

    Directory of Open Access Journals (Sweden)

    Bing Wang

    Full Text Available Characterization of soil water content (SWC profiles at catchment scale has profound implications for understanding hydrological processes of the terrestrial water cycle, thereby contributing to sustainable water management and ecological restoration in arid and semi-arid regions. This study described the vertical profiles of SWC at the small catchment scale on the hilly and gully Loess Plateau in Northeast China, and evaluated the influences of selected environmental factors (land-use type, topography and landform on average SWC within 300 cm depth. Soils were sampled from 101 points across a small catchment before and after the rainy season. Cluster analysis showed that soil profiles with high-level SWC in a stable trend (from top to bottom were most commonly present in the catchment, especially in the gully related to terrace. Woodland soil profiles had low-level SWC with vertical variations in a descending or stable trend. Most abandoned farmland and grassland soil profiles had medium-level SWC with vertical variations in varying trends. No soil profiles had low-level SWC with vertical variations in an ascending trend. Multi-regression analysis showed that average SWC was significantly affected by land-use type in different soil layers (0-20, 20-160, and 160-300 cm, generally in descending order of terrace, abandoned farmland, grassland, and woodland. There was a significant negative correlation between average SWC and gradient along the whole profile (P<0.05. Landform significantly affected SWC in the surface soil layer (0-20 cm before the rainy season but throughout the whole profile after the rainy season, with lower levels on the ridge than in the gully. Altitude only strongly affected SWC after the rainy season. The results indicated that land-use type, gradient, landform, and altitude should be considered in spatial SWC estimation and sustainable water management in these small catchments on the Loess Plateau as well as in other

  11. Seasonal and interannual variation of radiation and energy fluxes over a rain-fed cropland in the semi-arid area of Loess Plateau, northwestern China

    Science.gov (United States)

    Chen, Xing; Yu, Ye; Chen, Jinbei; Zhang, Tangtang; Li, Zhenchao

    2016-07-01

    Understanding the land-atmosphere interactions over the semi-arid area of Loess Plateau is important due to its special climate and unique underlying surface. In this study, two years' micrometeorological and energy flux observations from the Pingliang Land Surface Process & Severe Weather Research Station, CAS were used to investigate the seasonal and interannual variations of radiation budget and energy fluxes over a rain-fed cropland in the semi-arid area of Loess Plateau, with an emphasis on the influence of rain, soil moisture and agricultural production activities (such as crop type and harvest time) on the energy partitioning as well as the surface energy balance. The results revealed large annual variations in the seasonal distribution of precipitation, which gave rise to significant seasonal and interannual variations in soil moisture. Soil moisture was the main factor affecting radiation budget and energy partitioning. There was a negatively linear relationship between the albedo and the soil moisture. The main consumer of available energy varied among months and years with an apparent water stress threshold value of ca. 0.12 m3 m- 3, and the evapotranspiration was suppressed especially during the growing season. On an annual scale, the largest consumer of midday net radiation was sensible heat flux in 2010-2011, while it was latent heat flux in 2011-2012, which accounted for about 35% and 40% of the net radiation, respectively. The agricultural activity altered the sensitivity and variability of albedo to soil moisture, as well as energy partitioning patterns. The surface energy budget closures during Dec. 2010-Nov. 2011 and Dec. 2011-Nov. 2012 were 77.6% and 73.3%, respectively, after considering the soil heat storage. The closure was comparable to other sites in ChinaFLUX (49% to 81% of 8 sites). The patterns of energy partitioning and the water stress threshold found in the semi-arid cropland could be used to evaluate and improve land surface models.

  12. Evaluating the eco-hydrologic impacts of soil and water conservation in the Jinghe River Basin of Loess Plateau, China, using an eco-hydrologic model

    Science.gov (United States)

    Peng, Hui; Jia, Yangwen; Tague, Christina; Slaughter, Peter

    2016-04-01

    Since the 1950s, soil and water conservation has been widely applied in the Loess Plateau in China. We examine the eco-hydrologic responses to soil and water conservation in the Jinghe River Basin of Loess Plateau in two scales - catchment scale and basin scale, using Regional Hydro-Ecologic Simulation System (RHESSys). In the catchment scale, we apply the model to disentangle the relative roles played by inter-annual variation and longer-term trends in climate drivers and re-growth following reforestation. Our model-based analysis of trends in forest water use highlights the differences in the response of control and reforested catchments to similar declines in annual precipitation in this region over the past decades. Model estimates show that while reforestation does increase vegetation water use, the impacts on streamflow are small relative to the impact of precipitation trends on streamflow, and forest water use. Results also show that the greatest impact of reforestation is likely to be on groundwater recharge but also suggest that evaporation rather than transpiration is a significant contributor to hydrologic change. In the basin scales, we applied the modified model to evaluate the impacts of soil and water conservation measures on streamflow. Results demonstrate that the soil and water conservation decreased annual streamflow by 8% (0.1 billion m3), with the largest decrease occurring in the 2000s. Model estimates also suggest that soil and water conservation engineering has greater impacts than vegetation recovery. This study offers scientific support for soil and water conservation planning and management in this region.

  13. Holocene environmental change inferred from the loess-palaeosol sequences adjacent to the floodplain of the Yellow River, China

    Science.gov (United States)

    Huang, Chun Chang; Pang, Jiangli; Su, Hongxia; Li, Shengli; Ge, Benwei

    2009-12-01

    Chinese loess deposits are generally considered to be the product of dust storms and dust falls from the central Asia arid zones that were transported across China by the northwesterly continental monsoon. In contrast, the Zhengzhou Loess found southeast of the Loess Plateau, adjacent to the floodplain of the Yellow River, records a different eolian regime and dust source. The Zhengzhou Loess was investigated by field observations, measurements of magnetic susceptibility, particle-size distribution, loss-on-ignition, CaCO 3 and chemical contents. Both field observations and the laboratory results indicate that, during the last glacial, the Zhengzhou Loess was supplied by two different eolian regimes and dust sources, one was from the fresh flood deposits of the Yellow River driven by the northeast winds from the low-lying floodplain, and the other was from the dust storms and dust falls that traveled across the Loess Plateau driven by the northwesterly continental monsoon from the central Asian arid lands. The early Holocene, 11,500-8500 a BP, was a transition during the change in eolian regime and dust source because of the weakened northwesterly monsoon along with the global climatic amelioration. Following the retreat of the northwesterly monsoon from the onset of the mid-Holocene Climatic Optimum at 8500 a BP, dust supply from the drifting sand zone on the Yellow River floodplain became dominant because of the intensified strength of the northeast winds from the Bohai Sea. From 3100 a BP onwards, climatic aridity and extensive human disturbance have resulted in intensive eolian processes causing the incursion of the drifting sand into the Zhengzhou Loess zone. These results show that loess accumulation is more complex than traditionally assumed. The origin of loess deposits elsewhere outside the Loess Plateau may be related to dust sources derived from alluvial sediments of major river systems.

  14. Helium isotope investigation on magnetic reversal boundaries of loess-paleosol sequence at Luochuan, central Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Extraterrestrial particles have higher 3He/4He ratios than those of terrestrial sediments ( > 100 Ra versus < 0.03 Ra, where Ra is the 3He/4He ratio normalized to the atmospheric value of 1.4×10-6). The interplanetary dust particles (IDPs), which are very rich in 3He, continuously bombard the Earth and can accumulate in deposits. IDPs sedimentation rate changes can significantly influence 3He concentration in the Earth surface sediments. Since IDPs are not easy to detect in terrestrial deposits, measuring helium isotopes is a helpful approach to examine changes in IDPs. Helium concentration and helium isotopic composition magnetic substances and the quartz particles were examined for helium concentration and helium isotopic ratio. Results show that the 3He/4He ratio and the 3He concentrations of the magnetic substances are clearly higher than those of the bulk samples and the quartz particles, and, the 3He/4He ratio of the extracted magnetic substances is also higher than that of the average level of the Earth's crust. The higher helium content in the magnetic fractions can be explained by an influx of IDPs.

  15. 黄土高原西部红粘土岩石磁学性质及其指示的亚洲内陆中中新世气候变化特征%MID-MIOCENE CLIMATE IN THE ASIAN INTERIOR ,BASED ON THE MINERAL-MAGNETIC RECORD OF THE RED CLAY SEQUENCE ON THE WESTERN CHINESE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    赵辉; 强小科; 敖红; 徐新文; 孙玉芳; 陈艇

    2012-01-01

    对黄土高原西部庄浪红粘土进行详细岩石磁学分析表明,沉积物磁性由磁铁矿和赤铁矿主导,并且含有一定量的磁赤铁矿.中中新世大暖期红粘土中磁铁矿、磁赤铁矿含量显著升高;中中新世大暖期前后红粘土中的磁铁矿含量相对较低,赤铁矿相对含量较高,但并未显示较强的磁赤铁矿信息.磁性矿物的整体粒径表现为以SP,SD和PSD颗粒为主,MD颗粒较少.庄浪红粘土磁化率在16.5 ~ 13.8Ma出现峰值,与当时的夏季风强盛、降水丰富、成壤作用较强造成的亚铁磁性矿物相对含量增加密切相关.在全球气候变暖的中中新世大暖期,综合庄浪岩石磁学特征以及陆地和海洋的其他证据可以推测当时东亚冬、夏季风可能同时增强.%Heqing Basin(26°27' - 26°46'N, 100°08' ~ 100°17'E) is a Late Cenozoic north-south oriented pull-apart basin near the northwestern margin of the Yunnan-Guizhou Plateau. The Basin is located at the southeastern margin of the Tibetan Plateau and belongs to the terminal of Hengduan Mountains. The local climate is dominated by Indian monsoon. Therefore,the continuous and thick sediments in the basin make it a perfect continental record for evolution of Indian summer monsoon. The Heqing drill core was obtained in the centre of the Heqing Basin. Using the internal lining method, recovery of the HQ drill core (26°33'43. 1"N, 100°10'14. 2"E;2200m) which has an accumulative depth of 665. 83m reaches up to 96. 7%. The lake sediments mainly consist of horizontally laminated greyish-green calcareous clay and silty clay with thin-bedded silt and fine sand layers, except two intervals of sand layers with fine gravels. With the equal interval of 50cm, we obtained 1368 samples from the drill core and chose 108 from different depositional units for detailed rock magnetic measurements. Based on detailed rock magnetic measurements like magnetic susceptibility versus high/low temperature curves

  16. 黄土高原0.8Ma以来地面抬升的时空特征研究%The Spatial and Temporal Features of Surface Uplift in Loess Plateau Since 0.8 Ma

    Institute of Scientific and Technical Information of China (English)

    胡春生; 潘保田; 苏怀

    2012-01-01

    The river terrace is one of the direct geomorphic evidences of the surface uplift. By analyzing the characteristics of the Yellow River terraces in Loess Plateau, it is presented that the terraces are mainly tectonic genesis, and formed after the Yellow River reached a quasi-equilibrium state. It is reasonable to use the Yellow River terraces for representing the surface uplift of the Loess Plateau. In the Lanzhou Basin, two fourth terrac- es of the Yellow River are selected as the study sections, namely the Zaoshugou terrace and the Wuyishan ter- race. At the Zaoshugou terrace, the altitude of gravel stratum is 80 m higher than the river level. The top of the gravel stratum is overlain by at least 64 m eolian loess, and the paleosol S8 is at the bottom of the eolian loess. At the Wuyishan terrace, the altitude of gravel stratum is 140 m higher than the river level. The top of the grav- el stratum is overlain by at least 100 m eolian loess, and the paleosol S8 is at the bottom of the eolian loess. The optically stimulated luminescence (OSL) dating result indicates that the age of the upper part of paleosol S, at the Zaoshugou terrace is 70.44-7.6 ka. The results of paleomagnetic dating, optically stimulated luminescence dating and loess-paleosol sequence matching indicate that the two terraces have the same age, and both were formed at about 0.865Ma. Therefore this paper advances that there is the Yellow River terraces at 0.8Ma in the Lanzhou Basin, and the fourth terrace of the Yellow River may be a geomorphic response to the event of the surface uplift at 0.8Ma around the Qinghai-Tibetan Plateau. According to the research on the Yellow River ter- races at 0.8Ma in the Loess Plateau and the correlative literature, this paper verifies that there was a large-scale surface uplift at about 0.8Ma in the Loess Plateau, and the surface uplift resulted in river incision and terrace formation. Lanzhou, Heishan Canyon, Shanxi-Shaanxi Canyon and Sanmenxia were also

  17. Landform-derived placement of electrical resistivity prospecting for paleotopography reconstruction in the loess landforms of China

    Science.gov (United States)

    Xiong, Li-Yang; Tang, Guo-An; Zhu, A.-Xing; Li, Ji-Long; Duan, Jia-Zhen; Qian, Ye-Qing

    2016-08-01

    The paleotopography of loess landform represents the initial surface before the evolution of the Aeolian depositional process. This paleotopography served as an indicator of the paleo-geography and erosion base that restrained the evolution of the current landform. In this case study, a landform-derived placement method involving electrical resistivity prospecting is proposed for paleotopography reconstruction. The method consists of extracting terrain feature knowledge and terrain feature-based paleotopography prospecting and reconstruction. The field experiment is validated and used in three typical loess landform areas in the Chinese Loess Plateau. These typical loess landforms include loess hill, loess ridge, and loess tableland. Terrain features considered include peaks, saddles, ridges, and gullies. The results show significant electrical resistivity difference between the paleotopography and loess strata. The electrical resistivity method could effectively detect the paleotopography and different loess layers. The reconstructed paleotopography using the feature-based method could effectively represent the morphology of the paleosurface compared to the result of the interpolation method. The reconstructed paleotopography also appears as a coincident terrain relief compared to modern topography; such a relief demonstrates significant landform inheritance between modern terrain and paleotopography. In the loess hill and ridge landform areas, the relative elevation difference of paleotopography is approximately 50 m whereas that of the modern terrain is roughly 150 m, indicating that the loess deposition process increased the topographic relief from paleotopography to modern terrain by approximately 100 m. Similar altitude of the paleotopographic peaks (roughly 10 m height difference) appears in the two nearby loess ridge and hill areas. The results indicate that paleo-geography of this area should be a landform of peneplain and almost a planation surface.

  18. Effects of Revegetation on Soil Organic Carbon Storage and Erosion-Induced Carbon Loss under Extreme Rainstorms in the Hill and Gully Region of the Loess Plateau

    Directory of Open Access Journals (Sweden)

    Yujin Li

    2016-04-01

    Full Text Available Background: The Loess Plateau, an ecologically vulnerable region, has long been suffering from serious soil erosion. Revegetation has been implemented to control soil erosion and improve ecosystems in the Loess Plateau region through a series of ecological recovery programs. However, the increasing atmospheric CO2 as a result of human intervention is affecting the climate by global warming, resulting in the greater frequency and intensity of extreme weather events, such as storms that may weaken the effectiveness of revegetation and cause severe soil erosion. Most research to date has evaluated the effectiveness of revegetation on soil properties and soil erosion of different land use or vegetation types. Here, we study the effect of revegetation on soil organic carbon (SOC storage and erosion-induced carbon loss related to different plant communities, particularly under extreme rainstorm events. Materials and methods: The erosion-pin method was used to quantify soil erosion, and soil samples were taken at soil depths of 0–5 cm, 5–10 cm and 10–20 cm to determine the SOC content for 13 typical hillside revegetation communities in the year of 2013, which had the highest rainfall with broad range, long duration and high intensity since 1945, in the Yanhe watershed. Results and discussion: The SOC concentrations of all plant communities increased with soil depth when compared with slope cropland, and significant increases (p < 0.05 were observed for most shrub and forest communities, particularly for natural ones. Taking the natural secondary forest community as reference (i.e., soil loss and SOC loss were both 1.0, the relative soil loss and SOC loss of the other 12 plant communities in 2013 ranged from 1.5 to 9.4 and 0.30 to 1.73, respectively. Natural shrub and forest communities showed greater resistance to rainstorm erosion than grassland communities. The natural grassland communities with lower SOC content produced lower SOC loss even

  19. Effects of Vegetation Succession on Soil Fertility Within Farming-Plantation Ecotone in Ziwuling Mountains of the Loess Plateau in China

    Institute of Scientific and Technical Information of China (English)

    LIANG Jian; WANG Xiao-an; YU Zhong-dong; DONG Zhong-min; WANG Jin-cheng

    2010-01-01

    To further understand the relationship between vegetation succession and soil fertility within farming-plantation ecotone in Ziwuling Mountains of the Loess Plateau,nine kinds of widely distributed communities at different succession stages were selected,and the effects of vegetation succession on soil fertility were studied through the methods of comparing two hierarchical clustering(similarity index: B)and other multivariate analysis.The results showed that:(ⅰ)the similarity in clustering pattern of nine communities which classified by plant species and soil nutrients respectively showed a trend of(B)overall plant-soil 0-10>(B)overall plant-soil 10-20cm>(B)overall plant-soil 20-40cm,and for the top soil,it showed a trend of(B)grass-soil 0-10cm>(B)shrub-soil 0-10cm>(B)tress-soil 0-10cm;(ⅱ)soil fertility increased during the succession process from abandoned land to forest community,and the soil fertility of forest community showed an increased order of coniferous forest→mixed forest →broadleaf forest;(ⅲ)during the process of vegetation succession,the variation of topsoil fertility was higher than that of the subsurface soil(coefficient of variation: CV0-10cm> CV10-20cm> CV20-40cm),and when the succession developed into the stages of shrub and forest communities,the top soil fertility had been improved significantly; and(ⅳ)for the subsurface soil of the communities at the advanced succession stages,the soil fertility also increased to some extent.Our results suggested that the method of comparing two hierarchical clustering reflected the similarity level of different cluster patterns,therefore,it was helpful to study the relationship between vegetation succession and soil fertility,There was a corresponding relationship between the change process of soil fertility from the top soil to subsurface soil and the process of vegetation succession from the early stages to the advanced stage.The differentiations of soil fertility in vertical space and

  20. Integrating a mini catchment with mulching for soil water management in a sloping jujube orchard on the semiarid Loess Plateau of China

    Science.gov (United States)

    Li, Hongchen; Zhao, Xining; Gao, Xiaodong

    2015-04-01

    Conserving more soil water is of great importance to the success of arid and semiarid orchards. On the hilly areas of the Loess Plateau of China, mini catchments, named fish-scale pits, are widely used in orchards for collecting surface runoff to infiltrate more soil water. However, the flat surface inside fish-scale pits would increase soil evaporation during non-rainfall periods. Here we integrated fish-scale pits with mulching, a popular meanings to reduce soil evaporation, to test whether this integration could improve soil water conservation. To this end, we observed soil water in the 0-180 cm in a typical rain fed jujube orchard in the hilly region of the Loess Plateau. Four different treatments with three replicates of each were established including fish-scale pit with branch mulching (FB), fish-scale pit with straw mulching (FS), fish-scale pit without mulching (F) and no fish-scale pit and no mulching (CK). The results showed that the treatments FB, FS, and F increased soil water storages (SWS) in the 0-180 cm by 14.23%, 9.35% and 4.82%, respectively, compared to the CK during the growing season. It is noteworthy that the increases of SWS were mainly in the 0-100cm indicating relatively low levels of water was supplied by rainfall infiltration beneath. During the dry season (June), an apparent soil water deficit was observed for all treatments. Throughout the wet season (July and August) soil water was greatly compensated. However, soil water deficit occurred again in the dry month of September. An index was used to represent the soil water supply from rainfall infiltration denoted WS. During the growing season the FB and FS treatments showed positive WS in the whole profile while the F treatment showed positive values only in the 0-100 cm. However, positive WS values were only found in the 0-40 cm for the CK treatment. In conclusion, integrating fish-scale pits with branch/straw mulching could conserve significantly more soil water by increasing

  1. Loess 10Be evidence for an asynchronous Brunhes-Matuyama magnetic polarity reversal

    Science.gov (United States)

    Zhou, W.; Beck, W.; Kong, X.; An, Z.; Qiang, X.; Wu, Z.; Xian, F.; Ao, H.

    2015-12-01

    In Chinese loess the Brunhes-Matuyama (B-M) geomagnetic reversal appears to occur about 25 ka prior to the established axial dipole reversal age found in many marine sediments, i.e., in Chinese loess this magnetic reversal boundary is found in glacial loess unit L8 which is thought to be correlated with Marine Isotope Stage 20 (MIS 20), in marine sediment records, however, this boundary is commonly found in interglacial period of MIS 19[1-2], leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments[3-5]. Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity [6]. This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out both the 10Be studies and paleogeomagnetic measurements in Luochuan and Xifeng sections in Chinese Loess Plateau. Both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7 corresponding to MIS 19, proving that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records [1]. These results reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the paleogeomagnetic measurements, which show that the B-M boundary is in L8 in these two Chinese loess-paleosol sequences, demonstrating that loess magnetic overprinting has occurred. 1.Tauxe, L., et al., 1996, EARTH PLANET SC LETT, 140, 133-1462.Zhou, L.P., and Shackleton, 1999

  2. Mapping and Evaluation of NDVI Trends from Synthetic Time Series Obtained by Blending Landsat and MODIS Data around a Coalfield on the Loess Plateau

    Directory of Open Access Journals (Sweden)

    Kun Wang

    2013-09-01

    Full Text Available The increasingly intensive and extensive coal mining activities on the Loess Plateau pose a threat to the fragile local ecosystems. Quantifying the effects of coal mining activities on environmental conditions is of great interest for restoring and managing the local ecosystems and resources. This paper generates dense NDVI (Normalized Difference Vegetation Index time series between 2000 and 2011 at a spatial resolution of 30 m by blending Landsat and MODIS (Moderate Resolution Imaging Spectroradiometer data using the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM and further evaluates its capability for mapping vegetation trends around a typical coalfield on the Loss Plateau. Synthetic NDVI images were generated using (1 STARFM-generated NIR (near infrared and red band reflectance data (scheme 1 and (2 Landsat and MODIS NDVI images directly as inputs for STARFM (scheme 2. By comparing the synthetic NDVI images with the corresponding Landsat NDVI, we found that scheme 2 consistently generated better results (0.70 < R2 < 0.76 than scheme 1 (0.56 < R2 < 0.70 in this study area. Trend analysis was then performed with the synthetic dense NDVI time series and the annual maximum NDVI (NDVImax time series. The accuracy of these trends was evaluated by comparing to those from the corresponding MODIS time series, and it was concluded that both the trends from synthetic/MODIS NDVI dense time series and synthetic/MODIS NDVImax time series (2000–2011 were highly consistent. Compared to trends from MODIS time series, trends from synthetic time series are better able to capture fine scale vegetation changes. STARFM-generated synthetic NDVI time series could be used to quantify the effects of mining activities on vegetation, but the test areas should be selected with caution, as the trends derived from synthetic and MODIS time series may be significantly different in some areas.

  3. The control of soil polarization in Populus simonii and Quercus liaotungensis forests by forage litter on the Loess Plateau, P. R. China

    Institute of Scientific and Technical Information of China (English)

    Nhu Trung Luc; Zengwen Liu; Yuanhao Bing; Xiaoxi Zhang; Thi Huong Nguyen

    2015-01-01

    Soil polarization in pure forest stands affects the stability and sustainable development of the ecosystem. The most effective approaches to the prevention of soil polarization may be the use of forage litter as fertilizer or the direct establishment of tree-grass communities. We investigated monospecific plantations of Populus simonii and Quercus liaotungensis. Such plantations have been established throughout the Loess Plateau of China. A 120-day decomposition incubation experiment with forest humus soil mixed with 7 common leguminous forage litter species was performed to study the uses of forage litter in controlling soil polarization in pure forests. The addition of forage litter of Astragalus adsurgens, Lespedeza bicolor, and Vicia villosa to the soil of pure P. simonii forest clearly improved the soil quality, these forage species are suitable for planting with P. simonii, whereas Melilotus officinalis, Medicago sativa, and Onobrychis viciifolia litter produced obvious deterioration, thus these forages should not be planted with P. simonii. Coronilla varia litter showed no significant influence. The addition of forage litter of M. sativa to the soil of pure Q. liaotungensis forest clearly improved the soil quality, and C. varia and V. villosa also yielded improvements but were slightly less effective than M. sativa litter, these forages are suitable to be planted with Q. liaotungensis. However, L. bicolor showed obvious deterioration, followed by O. viciifolia and A. adsurgens, and M. officinalis had no significant influence. These spe-cies should not be planted with Q. liaotungensis.

  4. Impacts of mixed litter decomposition from Robinia pseudoacacia and other tree species on C loss and nutrient release in the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    Xiaoxi Zhang; Zengwen Liu; Bochao Zhu; Yuanhao Bing; Nhu Trung Luc; Liangzhen Du; Zhenhua Zhu

    2016-01-01

    The productivity of Robinia pseudoacacia (R.p.) pure forest usually declines at the late growth stage, and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags (R.p. ? each other species) and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotun-gensis (Q.l.). But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree.

  5. Vegetation Response to Hydro-thermal Condition in Loess Plateau%黄土高原植被对水热状况的响应研究

    Institute of Scientific and Technical Information of China (English)

    李小燕

    2013-01-01

    EOF (Empirical Orthogonal Functions),SVD (Singular Value Decomposition) and lag cross-correlation were applied to analyze temporal and spatial response characteristics of vegetation cover to the variation of hydro-thermal condition,and distinguish the spatial-temporal correlation between vegetation index and climate factors.The results indicated that the hydro-thermal conditions have more principal components and worse regularity as well as minor variance contributes.The variation of hydro-thermal condition depends on monsoon climate,latitude,underlaying surface and so on,which is very complicated and changeable.But there are obvious characters in vegetation cover.The maximum based on lag cross-correlation method shows that the speed of wheat response of southern Loess Plateau to hydro-thermal condition is faster than forest,warm vegetation,cold-halophytic-drought plants and strong drought plants,and the lag-time is about 0-30 days,so more precipitation have stronger impact on vegetation growth than temperature.However,the minimum coeffi cient reflects that there is significant negative correlation between vegetation cover and double-cropping winter wheat and minor cereals in South Loess Plateau.Singular value decomposition illustrates that vegetation cover is in accordance with hydro-thermal condition in the same area,but there is still obvious negative correlation.Negative correlation is caused by crop-cutting and soil corrosion due to crop rotation system and climate type.It is the best condition for vegetation cover in southeast region of Loess Plateau.More precipitation will be the advantage for vegetation cover,including the hydrological effect of the Yellow River,but when the temperature is higher than one threshold value it won't be an advantage for vegetation cover in arid and semi-arid region.Higher temperature makes plants grow well where there is sufficient moisture in arid region.The vegetation cover has close relations to hydro-thermal condition in

  6. Comparison of drip, pipe and surge spring root irrigation for Jujube (Ziziphus jujuba Mill. fruit quality in the Loess plateau of China.

    Directory of Open Access Journals (Sweden)

    Qing-Han Gao

    Full Text Available Loess Plateau is a typical rain-fed farming region, facing the threat of drought. Irrigation method is among the most important factors affecting jujube quality. This study investigated the response of Ziziphus jujuba Mill. cv. Lizao quality to three different irrigation methods (drip-, pipe- and surge spring root irrigation combining two water levels (20 m(3/hm(2 and 120 m(3/hm(2. The effects of the trials were evaluated by taking into account the physical-chemical characteristics of jujubes and the antioxidant activity. Concomitant to this, the concentration of some taste-related (viz. glucose, fructose, TSS and malic acid and health-related compounds/parameters (viz. catechin and epicatechin were generally much greater in jujube fruit treated with drip irrigation (120 m(3/hm(2. Different irrigation treatments had no significant effects on antioxidant capacity, total phenolics and proanthocyanidins (except for pipe irrigation 20 m(3/hm(2. The best compromise between quality and irrigation of jujube fruit was achieved with drip irrigation (120 m(3/hm(2.

  7. Artemisia dominant species succession relating to the soil moisture decrease in abandoned land of the Loess Plateau (China): comparative study of drought-adaptive characteristics.

    Science.gov (United States)

    Wang, Yong; Yu, Jing; Xia, Pengguo; He, Shaoxuan; Zhou, Ziyun; Han, Ruilian; Liang, Zongsuo

    2016-01-01

    Artemisia scoparia, Artemisia sacrorum and Artemisia giraldii were three dominant Artemisia species which successive grew in the secondary succession on abandoned land of the Loess Plateau. The succession accompanied the soil moisture steady decrease with field age after their abandonment. To elucidate the relationship between the Artemisia species succession and their drought-adaptation, three dominant species and a contrastive species Artemisia annua (mesophyte), were selected to compare their drought-resistant characteristics, including morphological and anatomical traits of leaf and root. Then physiological responses were investigated in mature plants after drought treatment. The results indicated that three dominant species leaf presented drought-adaptive structures, such as bushy trichomes, transitional or isolateral leaf cells, thick cuticles and epidermal cells. However, A. annua had no leaf traits involved in drought-adaptation. In addition, A. sacrorum and A. giraldii contained large root systems, while A. scoparia and A. annua utilized succulent roots. The physiological responses to drought suggested that A. giraldii had strong regulation in water using strategy, growth, as well as superoxide dismutase and catalase activity. A. sacrorum and A. giraldii could maintain high ascorbate peroxidase activity and malondialdehyde content, while A. scoparia and A. giraldii presented higher peroxidase activity, ascorbate and soluble sugar content. A. annua exhibited high proline and carotenoid contents under drought. The drought-resistant of the four Artemisia species presented the order of A. giraldii > A. sacrorum > A. scoparia > A. annua, which was consistent with their succession on abandoned land.

  8. Microcalorimetric study of the effects of long-term fertilization on soil microbial activity in a wheat field on the Loess Plateau.

    Science.gov (United States)

    Zhang, Qi; Liu, Xiaomei; Ma, Xiaojun; Fang, Jian; Fan, Tinglu; Wu, Fasi; An, Lizhe; Feng, Huyuan

    2014-12-01

    The effects of the long-term inorganic (nitrogen, N; phosphate, P) and organic (manure, M; straw, S) fertilizers/managemenet individually and in combinations (N, NP, SNP, M, and MNP) on soil microbial activity were investigated in a wheat field on the Loess Plateau, China. Microcalorimetry was used to determine microbial activity under different treatments. Nearly 30 years of consecutive fertilization has altered the culturable population of soil bacteria and fungi, the highest ones were detected in the treatments of manure and MNP, followed by the NP and SNP treatments. The microbial growth rate constant (μ/h(-1)) was significantly greater in the MNP treatment than all the other treatments. The total heat exchange values (Q/J) were the highest in the MNP and NP treatments, which were significantly different from the N and M treatments. The peak height (P(t)/μW) were significantly higher in MNP and NP treatments than in the remaining treatments. The peak time values (t(p)/h) among the MNP, NP, SNP and M, N and CK treatments were significantly different. In general, comparing with control, soil microbial activity was much higher in MNP, NP and SNP treatments, all including the phosphate fertilizer. Our results showed that the application of inorganic fertilizer and organic manure have positive effects on multiple soil chemical parameters, soil microorganism abundance and activity, and hence crop yield.

  9. Evaluation of the AquaCrop model for simulating yield response of winter wheat to water on the southern Loess Plateau of China.

    Science.gov (United States)

    Zhang, Wanhong; Liu, Wenzhao; Xue, Qingwu; Chen, Jie; Han, Xiaoyang

    2013-01-01

    The objective of this study was to evaluate the performance of the FAO-AquaCrop model in winter wheat in the southern Loess Plateau of China. Multi-year field experimental data from 2004 and 2011 were used to calibrate and validate the model for simulating biomass, canopy cover (CC), soil water content, and grain yield under rainfed conditions. The model performance was evaluated using root mean square error (RMSE) and Willmott index of agreement (d) as criteria. The RMSE ranged from 0.16 to 0.38 t/ha for simulating aboveground biomass, 1.87 to 4.15% for CC, 0.50 to 1.44 t/ha for grain yield, and 5.70 to 22.56 mm for soil water content. The d ranged from 0.22 to 0.89, 0.25 to 0.43, 0.36 to 0.62 and 0.95 to 0.98 for aboveground biomass, CC, soil water content and grain yield, respectively. Generally, the model performed better for simulating CC and yield than biomass and soil water content. The results further indicated that AquaCrop is capable of simulating winter wheat yield under rainfed conditions. Further improvement may be needed to capture the variation of different management practices such as fertility and irrigation levels in this region.

  10. Spatial and temporal variations of ecosystem service values in relation to land use pattern in the Loess Plateau of China at town scale.

    Directory of Open Access Journals (Sweden)

    Xuan Fang

    Full Text Available Understanding the relationship between land use change and ecosystem service values (ESVs is the key for improving ecosystem health and sustainability. This study estimated the spatial and temporal variations of ESVs at town scale in relation to land use change in the Loess Plateau which is characterized by its environmental vulnerability, then analyzed and discussed the relationship between ESVs and land use pattern. The result showed that ESVs increased with land use change from 1982 to 2008. The total ESVs increased by 16.17% from US$ 6.315 million at 1982 to US$ 7.336 million at 2002 before the start of the Grain to Green project, while increased significantly thereafter by 67.61% to US$ 11.275 million at 2008 along with the project progressed. Areas with high ESVs appeared mainly in the center and the east where largely distributing orchard and forestland, while those with low ESVs occurred mainly in the north and the south where largely distributing cropland. Correlation and regression analysis showed that land use pattern was significantly positively related with ESVs. The proportion of forestland had a positive effect on ESVs, however, that of cropland had a negative effect. Diversification, fragmentation and interspersion of landscape positively affected ESVs, while land use intensity showed a negative effect. It is concluded that continuing the Grain to Green project and encouraging diversified agriculture benefit to improve the ecosystem service.

  11. Spatial and temporal variations of ecosystem service values in relation to land use pattern in the Loess Plateau of China at town scale.

    Science.gov (United States)

    Fang, Xuan; Tang, Guoan; Li, Bicheng; Han, Ruiming

    2014-01-01

    Understanding the relationship between land use change and ecosystem service values (ESVs) is the key for improving ecosystem health and sustainability. This study estimated the spatial and temporal variations of ESVs at town scale in relation to land use change in the Loess Plateau which is characterized by its environmental vulnerability, then analyzed and discussed the relationship between ESVs and land use pattern. The result showed that ESVs increased with land use change from 1982 to 2008. The total ESVs increased by 16.17% from US$ 6.315 million at 1982 to US$ 7.336 million at 2002 before the start of the Grain to Green project, while increased significantly thereafter by 67.61% to US$ 11.275 million at 2008 along with the project progressed. Areas with high ESVs appeared mainly in the center and the east where largely distributing orchard and forestland, while those with low ESVs occurred mainly in the north and the south where largely distributing cropland. Correlation and regression analysis showed that land use pattern was significantly positively related with ESVs. The proportion of forestland had a positive effect on ESVs, however, that of cropland had a negative effect. Diversification, fragmentation and interspersion of landscape positively affected ESVs, while land use intensity showed a negative effect. It is concluded that continuing the Grain to Green project and encouraging diversified agriculture benefit to improve the ecosystem service. PMID:25329311

  12. Integrating a mini catchment with mulching for soil water management in a sloping jujube orchard on the semiarid Loess Plateau of China

    Directory of Open Access Journals (Sweden)

    H. C. Li

    2015-11-01

    Full Text Available Conserving more soil water is of great importance to the success of arid and semiarid orchards. On the hilly areas of the Loess Plateau of China, mini catchments, named fish-scale pits, are widely used in orchards for collecting surface runoff to infiltrate more soil water. However, the flat surface inside fish-scale pits would increase soil evaporation during non-rainfall periods. Therefore, we integrated fish-scale pits with mulching, a popular meaning to reduce soil evaporation, to test whether this integration could improve soil water conservation. The results showed that soil water deficit was observed for all treatments. However, soil water deficit was further intensified in the dry month. An index was used to represent the soil water supply from rainfall infiltration denoted WS. For the fish-scale pit with branch mulching treatment in the entire soil profile, the compensation degree of SWS were greater than 0. However, the CK treatment showed negative values in the 40–180 cm. In conclusion, integrating fish-scale pits with mulching could conserve significantly more soil water by increasing infiltration and decreasing evaporation compared to fish-scale pits alone. Since the mulching branches were trimmed jujube branches, the integration of fish-scale pit with branch mulching is recommended in jujube orchards in order to both preserve more soil water and reduce the cost of mulching materials.

  13. [Effects of Nitrogen Fertilization on Soil Respiration and Temperature Sensitivity in Spring Maize Field in Semi-Arid Regions on Loess Plateau].

    Science.gov (United States)

    Jiang, Ji-shao; Guo, Sheng-li; Wang, Rui; Liu, Qing-fang; Wang, Zhi-qi; Zhang, Yan-jun; Li, Na-na; Li, Ru-jian; Wu, De-feng; Sun, Qi-qi

    2015-05-01

    Understanding the effects of nitrogen fertilization on soil respiration rate and its temperature sensitivity (Q10) is of critical importance to predict the variability of soil respiration in cropland. A field experiment was established in a rain-fed spring maize cropland (Zea mays L. ) in the State Key Agro-Ecological Experimental Station in the Loess Plateau in Changwu County, Shaanxi Province, China. The experiment comprised of two treatments: no N-fertilizer application ( CK) and N-fertilizer application with 160 kg N · hm(-2) (N). Soil respiration rate, soil temperature, soil moisture, yields, aboveground biomass and root biomass were measured in two continuous spring maize growing seasons from April 2013 to September 2014. The cumulative soil CO2 emissions were increased by 35% in 2013 and 54% in 2014 in N treatment as compared to CK treatment. Though nitrogen fertilization significantly increased the cumulative soil CO2 emissions (P soil respiration (P Nitrogen fertilization significantly increased the maize yields, aboveground biomass and root biomass (P Nitrogen fertilization had no marked influence on soil temperature or moisture. Root biomass was a critical biotical factor for variation of soil respiration under nitrogen fertilization.

  14. Patterns of taxonomic, phylogenetic diversity during a long-term succession of forest on the Loess Plateau, China: insights into assembly process.

    Science.gov (United States)

    Chai, Yongfu; Yue, Ming; Liu, Xiao; Guo, Yaoxin; Wang, Mao; Xu, Jinshi; Zhang, Chenguang; Chen, Yu; Zhang, Lixia; Zhang, Ruichang

    2016-01-01

    Quantifying the drivers underlying the distribution of biodiversity during succession is a critical issue in ecology and conservation, and also can provide insights into the mechanisms of community assembly. Ninety plots were established in the Loess Plateau region of northern Shaanxi in China. The taxonomic and phylogenetic (alpha and beta) diversity were quantified within six succession stages. Null models were used to test whether phylogenetic distance observed differed from random expectations. Taxonomic beta diversity did not show a regular pattern, while phylogenetic beta diversity decreased throughout succession. The shrub stage occurred as a transition from phylogenetic overdispersion to clustering either for NRI (Net Relatedness Index) or betaNRI. The betaNTI (Nearest Taxon Index) values for early stages were on average phylogenetically random, but for the betaNRI analyses, these stages were phylogenetically overdispersed. Assembly of woody plants differed from that of herbaceous plants during late community succession. We suggest that deterministic and stochastic processes respectively play a role in different aspects of community phylogenetic structure for early succession stage, and that community composition of late succession stage is governed by a deterministic process. In conclusion, the long-lasting evolutionary imprints on the present-day composition of communities arrayed along the succession gradient. PMID:27272407

  15. Characteristics of Caragana korshinskii and Hippophae rhamnoides stemflow and their significance in soil moisture enhancement in Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    ShengQi JIAN; ChuanYan ZHAO; ShuMin FANG; Kai YU

    2014-01-01

    Stemflow of xerophytic shrubs represents a significant component of water replenishment to the soil-root system and influences water utilization of plant roots at the stand scale, especially in water-scarce semi-arid ecosystems. The stemflow of two semi-arid shrubs (Caragana korshinskii and Hippophae rhamnoides) and its effect on soil moisture enhancement were evaluated during the growing season of 2011 in the semi-arid loess region of China. The results indicated that stemflow averaged 12.3%and 8.4%of the bulk precipitation for C. korshinskii and H. rhamnoides, respectively. Individual stemflow increased in a linear function with increasing rain-fall depth. The relationship between funneling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for both C. korshinskii and H. rhamnoides. Averaged funneling ratios were 156.6±57.1 and 49.5±30.8 for C. korshinskii and H. rhamnoides, respectively, indicating that the canopy architecture of the two shrubs was an effective funnel to channel stemflow to the root area, and C. korshinskii showed a greater potential to use stemflow water in the semi-arid conditions. For individual rainfall events, the wetting front depths were ap-proximately 2 times deeper in the rooting zone around the stems than in the bare area outside canopy for both C. korshinskii and H. rhamnoides. Correspondingly, soil water content was also significantly higher in the root area around the shrub stem than in the area outside the shrub canopy. This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under semi-arid conditions.

  16. Effects of the ecological construction in the hlilly Loess Plateau%黄土丘陵区生态建设效应与农户响应

    Institute of Scientific and Technical Information of China (English)

    吕昌河; 王茜; 马俊飞

    2011-01-01

    The Hilly Loess Plateau in Northwestern China is a key region for the ecological construction program,financially supported by the government to promote the restoration of degraded land by converting slope farmland to forest or grassland.After the implementation in 1999,this program stimulated various changes in the physical environment,food grain production and rural income.In this paper we discussed effects of the program on the above aspects,and identified the awareness and responses of local farmers to the program in the Hilly Loess Plateau with special focuses on Ansai County,based on literature and household survey data.It was found that the ecological construction program markedly promoted the vegetation restoration and an increase of farmer income,and thus received a positive response and active participation of local farmers.Since the converted farmland was mostly steep slope land with low yield,the farmland conversion had no adverse effects on the food grain production,but it promoted an improvement of land inputs and management,adjustment of agricultural structure,and rural labor transfer,and thus the structural change of farmer income.It is suggested that the government should continue the support to the ecological building,to promote the development of high efficient farming systems such as greenhouse vegetation and fruit production to improve farmer income,and to help farmers building terraces to increase the subsistence level of food self-sufficiency.%黄土丘陵区是我国1999年实施的以退耕还林为中心的生态建设工程重点地区之一。文中以文献和农户调查数据为基础,对黄土丘陵区特别是陕北安塞县,生态建设对其植被恢复、粮食生产、农民收入的影响进行了梳理和总结,并分析了农户对生态建设的认知与响应。研究认为,生态建设显著促进了区域的植被恢复,增加了退耕农户的收入,得到了农户的积极响应和参与。由于退耕地多为劣质

  17. Effects of tillage methods, corn residue mulch and n fertilizer levels on the wheat crop productivity under the rain fed condition of loess plateau china

    International Nuclear Information System (INIS)

    A 2 years study was conducted to assess the effects of different tillage methods (Chisel plough tillage, Zero-tillage, Rotary tillage and Mould board plough tillage), two mulch levels (M0 i.e. No corn residue mulch and M1 i.e. Corn residue mulch) and 5 N fertilizer levels (0, 80, 160, 240 and 320 kg N/ha) on the wheat crop productivity under the rain fed condition of Loess Plateau, China. Factorial experiment with three replications, having strip, split-split arrangement, with tillage methods in the main plots, mulch levels in sub- plots and N-fertilizer levels in the sub-sub plots was used for this study. Due to variations in rainfalls, during the year, 2010-11, maximum grain yields i.e. 6.58 t/ha and 6.72 t/ha were recorded in case of Zero tillage planting method and similarly in case of 80 kg N/ha, while during the cropping year 2011-12 equal grain yields were recorded in case of all tillage methods, however maximum grain yield (7.46 t /ha) was recorded in case of 320 kg N/ha, N fertilizer level. On two years average basis, maximum grain yields i.e. 6.75 t/ha and 6.80 t/ha were recorded in case of Zero tillage planting method and similarly in case of 80 kg N/ha as compared with the other tillage methods or N fertilizer levels. Use of mulch reduced > 40% weeds infestation. Economic analysis shows that Zero tillage and minimum use of N fertilizer according to the projected rainfalls along with the use of mulch are both economic and environmental friendly. (author)

  18. [Generation mechanism of woodland runoff and sediment on Loess Plateau under hypo-rainfall--a case study of artificial P. tabulaeformis and secondary natural P. dadidiana stands].

    Science.gov (United States)

    Pan, Chengzhong; Shangguan, Zhouping

    2005-09-01

    Based on the long-term observation and from the viewpoints of water balance and runoff-and sediment generation, this paper studied the generation processes of runoff and sediment on two typical woodlands, artificial P. tabulaeformis and secondary natural P. dadidiana, and uncultivated slope-land in Loess Plateau under hypo-rainfall. The results showed that within the range of 5.0 - 50.0 mm rainfall, the total interception of canopy and litter was 15.45 % - 56.80 % for P. tabulaeformis and 20.56% - 47.81% for P. dadidiana, and decreased with increasing rainfall. Woodlands had a higher soil water infiltration capacity than uncultivated slope-land, especially in 0-20 cm soil layer. Both the two woodlands did not generate runoff under regular rainfall. Under the assumed rainfall of 2.5 mm x min(-1) intensity and 30 min duration, P. dadidiana stand did not produce runoff, but the runoff velocity and sediment-carrying capacity of uncultivated slope-land were 23.5 times, and runoff shearing stress and energy were 8 times as much as P. tabulaeformis stand. The runoff-and sediment generation on P. tabulaeformis stand decreased by 87.6% and 99.4%, respectively, compared with those on uncultivated slopeland, which was well accorded with the average observed value in runoff plots during 1988 - 2000. The theoretical analysis on the generation mechanism of woodland runoff and sediment may be effective to evaluate the benefits of forest in soil and water conservation.

  19. The combined effects of moss-dominated biocrusts and vegetation on erosion and soil moisture and implications for disturbance on the Loess Plateau, China.

    Science.gov (United States)

    Bu, Chongfeng; Wu, Shufang; Han, Fengpeng; Yang, Yongsheng; Meng, Jie

    2015-01-01

    Biological soil crusts (BSCs, or biocrusts) have important positive ecological functions such as erosion control and soil fertility improvement, and they may also have negative effects on soil moisture in some cases. Simultaneous discussions of the two-sided impacts of BSCs are key to the rational use of this resource. This study focused on the contribution of BSCs while combining with specific types of vegetation to erosion reduction and their effects on soil moisture, and it addressed the feasibility of removal or raking disturbance. Twelve plots measuring 4 m × 2 m and six treatments (two plots for each) were established on a 15° slope in a small watershed in the Loess Plateau using BSCs, bare land (as a control, BL), Stipa bungeana Trin. (STBU), Caragana korshinskii Kom. (CAKO), STBU planted with BSCs (STBU+BSCs) and CAKO planted with BSCs (CAKO+BSCs). The runoff, soil loss and soil moisture to a depth of 3 m were measured throughout the rainy season (from June to September) of 2010. The results showed that BSCs significantly reduced runoff by 37.3% and soil loss by 81.0% and increased infiltration by 12.4% in comparison with BL. However, when combined with STBU or CAKO, BSCs only made negligible contributions to erosion control (a runoff reduction of 7.4% and 5.7% and a soil loss reduction of 0.7% and 0.3%). Generally, the soil moisture of the vegetation plots was lower in the upper layer than that of the BL plots, although when accompanied with a higher amount of infiltration, this soil moisture consumption phenomenon was much clearer when combining vegetation with BSCs. Because of the trivial contributions from BSCs to erosion control and the remaining exacerbated consumption of soil water, moderate disturbance by BSCs should be considered in plots with adequate vegetation cover to improve soil moisture levels without a significant erosion increase, which was implied to be necessary and feasible.

  20. The effects of clouds and aerosols on net ecosystem CO2 exchange over semi-arid Loess Plateau of Northwest China

    Directory of Open Access Journals (Sweden)

    H. Yu

    2010-05-01

    Full Text Available The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University site. Daytime (solar elevation angles of larger than 50° NEE of CO2 obtained during the midgrowing season (July–August are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD. Results show a significant impact by clouds and aerosols on the CO2 uptake by the grassland (with smaller LAI values located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in canopy are lower, with a value of about 434.8 W m−2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index, and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions the CO2 uptake decreases with the cloudiness but the light use efficiency is enhanced, due to increase in the fraction of diffuse PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.

  1. Spatial and temporal variations of crop fertilization and soil fertility in the loess plateau in china from the 1970s to the 2000s.

    Science.gov (United States)

    Wang, Xiaoying; Tong, Yanan; Gao, Yimin; Gao, Pengcheng; Liu, Fen; Zhao, Zuoping; Pang, Yan

    2014-01-01

    Increased fertilizer input in agricultural systems during the last few decades has resulted in large yield increases, but also in environmental problems. We used data from published papers and a soil testing and fertilization project in Shaanxi province during the years 2005 to 2009 to analyze chemical fertilizer inputs and yields of wheat (Triticum aestivum L.) and maize (Zea mays L.) on the farmers' level, and soil fertility change from the 1970s to the 2000s in the Loess Plateau in China. The results showed that in different regions of the province, chemical fertilizer NPK inputs and yields of wheat and maize increased. With regard to soil nutrient balance, N and P gradually changed from deficit to surplus levels, while K deficiency became more severe. In addition, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium increased during the same period. The PFP of N, NP and NPK on wheat and maize all decreased from the 1970s to the 2000s as a whole. With the increase in N fertilizer inputs, both soil total nitrogen and alkali-hydrolysis nitrogen increased; P fertilizer increased soil available phosphorus and K fertilizer increased soil available potassium. At the same time, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium all had positive impacts on crop yields. In order to promote food safety and environmental protection, fertilizer requirements should be assessed at the farmers' level. In many cases, farmers should be encouraged to reduce nitrogen and phosphate fertilizer inputs significantly, but increase potassium fertilizer and organic manure on cereal crops as a whole. PMID:25380401

  2. Spatial and temporal variations of crop fertilization and soil fertility in the loess plateau in china from the 1970s to the 2000s.

    Directory of Open Access Journals (Sweden)

    Xiaoying Wang

    Full Text Available Increased fertilizer input in agricultural systems during the last few decades has resulted in large yield increases, but also in environmental problems. We used data from published papers and a soil testing and fertilization project in Shaanxi province during the years 2005 to 2009 to analyze chemical fertilizer inputs and yields of wheat (Triticum aestivum L. and maize (Zea mays L. on the farmers' level, and soil fertility change from the 1970s to the 2000s in the Loess Plateau in China. The results showed that in different regions of the province, chemical fertilizer NPK inputs and yields of wheat and maize increased. With regard to soil nutrient balance, N and P gradually changed from deficit to surplus levels, while K deficiency became more severe. In addition, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium increased during the same period. The PFP of N, NP and NPK on wheat and maize all decreased from the 1970s to the 2000s as a whole. With the increase in N fertilizer inputs, both soil total nitrogen and alkali-hydrolysis nitrogen increased; P fertilizer increased soil available phosphorus and K fertilizer increased soil available potassium. At the same time, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium all had positive impacts on crop yields. In order to promote food safety and environmental protection, fertilizer requirements should be assessed at the farmers' level. In many cases, farmers should be encouraged to reduce nitrogen and phosphate fertilizer inputs significantly, but increase potassium fertilizer and organic manure on cereal crops as a whole.

  3. Quantifying the impacts of climate change and ecological restoration on streamflow changes based on a Budyko hydrological model in China's Loess Plateau

    Science.gov (United States)

    Liang, Wei; Bai, Dan; Wang, Feiyu; Fu, Bojie; Yan, Junping; Wang, Shuai; Yang, Yuting; Long, Di; Feng, Minquan

    2015-08-01

    Understanding hydrological effects of ecological restoration (ER) is fundamental to develop effective measures guiding future ER and to adapt climate change in China's Loess Plateau (LP). Streamflow (Q) is an important indicator of hydrological processes that represents the combined effects of climatic and land surface conditions. Here 14 catchments located in the LP were chosen to explore the Q response to different driving factors during the period 1961-2009 by using elasticity and decomposition methods based on the Budyko framework. Our results show that (1) annual Q exhibited a decreasing trend in all catchments (-0.30 ˜ -1.71 mm yr-2), with an average reduction of -0.87 mm yr-2. The runoff coefficients in flood season and nonflood season were both decreasing between two periods divided by the changing point in annual Q series; (2) the precipitation (P) and potential evapotranspiration (E0) elasticity of Q are 2.75 and -1.75, respectively, indicating that Q is more sensitive to changes in P than that in E0; (3) the two methods consistently demonstrated that, on average, ER (62%) contributing to Q reduction was much larger than that of climate change (38%). In addition, parameter n that entails catchment characteristics in the Budyko framework showed positive correlation with the relative area of ER measures in all catchments (eight of them are statistically significant with p < 0.05). These findings highlight the importance of ER measures on modifying the hydrological partitioning in the region. However, ER actions over the sloping parts of the landscape weakened the impact of those in channels (i.e., check-dams) on Q, especially after the implementation of the Grain-for-Green project in 1999.

  4. Accumulation, transfer, and potential sources of mercury in the soil-wheat system under field conditions over the Loess Plateau, northwest China.

    Science.gov (United States)

    Wang, Shengli; Nan, Zhongren; Prete, Daniel; Ma, Jianmin; Liao, Qin; Zhang, Qian

    2016-10-15

    There is limited information on accumulation, transfer, and source of mercury in wheats under field conditions over the Loess Plateau, northwest China. The present study collected 26 pairs of topsoil and whole wheat samples (roots, stems, leaves, shells, and grains) from Dongdagou stream watershed and upper Xidagou stream watershed, Baiyin City, northwest China. Hg concentrations from these samples were used to identify their relationships with soil properties, interactions with other metals, localization of Hg in the different wheat tissues, bio-concentration and transfer of Hg, and major sources of Hg in wheat. Results show that Hg levels in 11 out of 26 sampled soils (42.3% of soil samples) exceeded Hg limit of grade II soil environmental quality standards in China (1.0mg·kg(-1)). Likewise, it was also found that Hg in over 50% of wheat grain samples reached or exceeded the maximum permissible food safety levels (0.02mg·kg(-1)) according to the General Standard of Contaminants in Food in China (GB 2762-2012). The spatial distribution pattern of Hg in wheats grains was different from that in the sampled soils. Hg concentrations in different wheat tissues were highest in roots, followed by leaves, stalks, shells, and grains, respectively. Bio-concentration factors (BCF) of Hg in almost all grains samples were one or two orders of magnitude lower than that in roots, except for two wheat samples. The translocation factors (TF) of Hg in wheat tissues on average were leaves>stems>shells>grains. The spatial distribution of Hg and its correlation with other heavy metal detected simultaneously in the soil samples suggested that the Hg soil contamination was probably caused by past sewage irrigation practices and atmospheric deposition. Correlation analysis revealed that the principle source of Hg in wheat roots was very likely from Hg contaminated soils. PMID:27300562

  5. Seed dormancy, seedling establishment and dynamics of the soil seed bank of Stipa bungeana (Poaceae) on the Loess Plateau of northwestern China.

    Science.gov (United States)

    Hu, Xiao Wen; Wu, Yan Pei; Ding, Xing Yu; Zhang, Rui; Wang, Yan Rong; Baskin, Jerry M; Baskin, Carol C

    2014-01-01

    Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after mechanical removal of palea and lemma (hulls), chemical scarification and dry storage. Fresh and one-year-stored seeds were sown in the field, and seedling emergence was monitored weekly for 8 weeks. Furthermore, seeds were buried at different soil depths, and then retrieved every 1 or 2 months to determine seed dormancy and seed viability in the laboratory. Fresh seeds (caryopses enclosed by palea and lemma) had non-deep physiological dormancy. Removal of palea and lemma, chemical scarification, dry storage (afterripening), gibberellin (GA3) and potassium nitrate (KNO3) significantly improved germination. Dormancy was completely released by removal of the hulls, but seeds on which hulls were put back to their original position germinated to only 46%. Pretreatment of seeds with a 30% NaOH solution for 60 min increased germination from 25% to 82%. Speed of seedling emergence from fresh seeds was significantly lower than that of seeds stored for 1 year. However, final percentage of seedling emergence did not differ significantly for seeds sown at depths of 0 and 1 cm. Most fresh seeds of S. bungeana buried in the field in early July either had germinated or lost viability by September. All seeds buried at a depth of 5 cm had lost viability after 5 months, whereas 12% and 4% seeds of those sown on the soil surface were viable after 5 and 12 months, respectively. PMID:25396423

  6. Soil Infiltration Characteristics in Agroforestry Systems and Their Relationships with the Temporal Distribution of Rainfall on the Loess Plateau in China.

    Directory of Open Access Journals (Sweden)

    Lai Wang

    Full Text Available Many previous studies have shown that land use patterns are the main factors influencing soil infiltration. Thus, increasing soil infiltration and reducing runoff are crucial for soil and water conservation, especially in semi-arid environments. To explore the effects of agroforestry systems on soil infiltration and associated properties in a semi-arid area of the Loess Plateau in China, we compared three plant systems: a walnut (Juglans regia monoculture system (JRMS, a wheat (Triticum aestivum monoculture system (TAMS, and a walnut-wheat alley cropping system (JTACS over a period of 11 years. Our results showed that the JTACS facilitated infiltration, and its infiltration rate temporal distribution showed a stronger relationship coupled with the rainfall temporal distribution compared with the two monoculture systems during the growing season. However, the effect of JTACS on the infiltration capacity was only significant in shallow soil layer, i.e., the 0-40 cm soil depth. Within JTACS, the speed of the wetting front's downward movement was significantly faster than that in the two monoculture systems when the amount of rainfall and its intensity were higher. The soil infiltration rate was improved, and the two peaks of soil infiltration rate temporal distribution and the rainfall temporal distribution coupled in rainy season in the alley cropping system, which has an important significance in soil and water conservation. The results of this empirical study provide new insights into the sustainability of agroforestry, which may help farmers select rational planting patterns in this region, as well as other regions with similar climatic and environmental characteristics throughout the world.

  7. Artemisia dominant species succession relating to the soil moisture decrease in abandoned land of the Loess Plateau (China): comparative study of drought-adaptive characteristics.

    Science.gov (United States)

    Wang, Yong; Yu, Jing; Xia, Pengguo; He, Shaoxuan; Zhou, Ziyun; Han, Ruilian; Liang, Zongsuo

    2016-01-01

    Artemisia scoparia, Artemisia sacrorum and Artemisia giraldii were three dominant Artemisia species which successive grew in the secondary succession on abandoned land of the Loess Plateau. The succession accompanied the soil moisture steady decrease with field age after their abandonment. To elucidate the relationship between the Artemisia species succession and their drought-adaptation, three dominant species and a contrastive species Artemisia annua (mesophyte), were selected to compare their drought-resistant characteristics, including morphological and anatomical traits of leaf and root. Then physiological responses were investigated in mature plants after drought treatment. The results indicated that three dominant species leaf presented drought-adaptive structures, such as bushy trichomes, transitional or isolateral leaf cells, thick cuticles and epidermal cells. However, A. annua had no leaf traits involved in drought-adaptation. In addition, A. sacrorum and A. giraldii contained large root systems, while A. scoparia and A. annua utilized succulent roots. The physiological responses to drought suggested that A. giraldii had strong regulation in water using strategy, growth, as well as superoxide dismutase and catalase activity. A. sacrorum and A. giraldii could maintain high ascorbate peroxidase activity and malondialdehyde content, while A. scoparia and A. giraldii presented higher peroxidase activity, ascorbate and soluble sugar content. A. annua exhibited high proline and carotenoid contents under drought. The drought-resistant of the four Artemisia species presented the order of A. giraldii > A. sacrorum > A. scoparia > A. annua, which was consistent with their succession on abandoned land. PMID:27398271

  8. Soil Infiltration Characteristics in Agroforestry Systems and Their Relationships with the Temporal Distribution of Rainfall on the Loess Plateau in China.

    Science.gov (United States)

    Wang, Lai; Zhong, Chonggao; Gao, Pengxiang; Xi, Weimin; Zhang, Shuoxin

    2015-01-01

    Many previous studies have shown that land use patterns are the main factors influencing soil infiltration. Thus, increasing soil infiltration and reducing runoff are crucial for soil and water conservation, especially in semi-arid environments. To explore the effects of agroforestry systems on soil infiltration and associated properties in a semi-arid area of the Loess Plateau in China, we compared three plant systems: a walnut (Juglans regia) monoculture system (JRMS), a wheat (Triticum aestivum) monoculture system (TAMS), and a walnut-wheat alley cropping system (JTACS) over a period of 11 years. Our results showed that the JTACS facilitated infiltration, and its infiltration rate temporal distribution showed a stronger relationship coupled with the rainfall temporal distribution compared with the two monoculture systems during the growing season. However, the effect of JTACS on the infiltration capacity was only significant in shallow soil layer, i.e., the 0-40 cm soil depth. Within JTACS, the speed of the wetting front's downward movement was significantly faster than that in the two monoculture systems when the amount of rainfall and its intensity were higher. The soil infiltration rate was improved, and the two peaks of soil infiltration rate temporal distribution and the rainfall temporal distribution coupled in rainy season in the alley cropping system, which has an important significance in soil and water conservation. The results of this empirical study provide new insights into the sustainability of agroforestry, which may help farmers select rational planting patterns in this region, as well as other regions with similar climatic and environmental characteristics throughout the world.

  9. Natural vegetation restoration is more beneficial to soil surface organic and inorganic carbon sequestration than tree plantation on the Loess Plateau of China.

    Science.gov (United States)

    Jin, Zhao; Dong, Yunshe; Wang, Yunqiang; Wei, Xiaorong; Wang, Yafeng; Cui, Buli; Zhou, Weijian

    2014-07-01

    Natural vegetation restoration and tree plantation are the two most important measures for ecosystem restoration on the Loess Plateau of China. However, few studies have compared the effects of the two contrasting measures on soil organic and inorganic carbon (SOC and SIC) sequestration or have further used SOC and SIC isotopes to analyze the inherent sequestration mechanism. This study examined a pair of neighboring small watersheds with similar topographical and geological backgrounds. Since 1954, natural vegetation restoration has been conducted in one of these watersheds, and tree plantation has been conducted in the other. The two watersheds have now formed completely different landscapes (naturally restored grassland and artificial forestland). Differences in soil bulk density, SOC and SIC content and storage, and SOC and SIC δ(13)C values were investigated in the two ecosystems in the upper 1m of the soil. We found that SOC storage was higher in the grassland than in the forestland, with a difference of 14.90 Mg ha(-1). The vertical changes in the δ(13)CSOC value demonstrated that the two ecosystems have different mechanisms of soil surface organic carbon accumulation. The SIC storage in the grassland was lower than that in the forestland, with a difference of 38.99 Mg ha(-1). The δ(13)CSIC values indicated that the grassland generates more secondary carbonate than the forestland and that SIC was most likely transported to the rivers from the grassland as dissolved inorganic carbon (DIC). The biogeochemical characteristics of the grassland were favorable for the formation of bicarbonate. Thus, more DIC derived from the dissolution of root and microbial respired CO2 into soil water could have been transported to the rivers through flood runoff. It is necessary to study further the transportation of DIC from the grassland because this process can produce a large potential carbon sink.

  10. Seed dormancy, seedling establishment and dynamics of the soil seed bank of Stipa bungeana (Poaceae on the Loess Plateau of northwestern China.

    Directory of Open Access Journals (Sweden)

    Xiao Wen Hu

    Full Text Available Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after mechanical removal of palea and lemma (hulls, chemical scarification and dry storage. Fresh and one-year-stored seeds were sown in the field, and seedling emergence was monitored weekly for 8 weeks. Furthermore, seeds were buried at different soil depths, and then retrieved every 1 or 2 months to determine seed dormancy and seed viability in the laboratory. Fresh seeds (caryopses enclosed by palea and lemma had non-deep physiological dormancy. Removal of palea and lemma, chemical scarification, dry storage (afterripening, gibberellin (GA3 and potassium nitrate (KNO3 significantly improved germination. Dormancy was completely released by removal of the hulls, but seeds on which hulls were put back to their original position germinated to only 46%. Pretreatment of seeds with a 30% NaOH solution for 60 min increased germination from 25% to 82%. Speed of seedling emergence from fresh seeds was significantly lower than that of seeds stored for 1 year. However, final percentage of seedling emergence did not differ significantly for seeds sown at depths of 0 and 1 cm. Most fresh seeds of S. bungeana buried in the field in early July either had germinated or lost viability by September. All seeds buried at a depth of 5 cm had lost viability after 5 months, whereas 12% and 4% seeds of those sown on the soil surface were viable after 5 and 12 months, respectively.

  11. On the factors influencing surface-layer energy closure and their seasonal variability over the semi-arid Loess Plateau of Northwest China

    Directory of Open Access Journals (Sweden)

    X. Xiao

    2012-03-01

    Full Text Available The energy observed in the surface layer, when using eddy-covariance techniques to measure turbulent fluxes, is not balanced. Important progress has been made in recent years in identifying potential reasons for this lack of closure in the energy balance, but the problem is not yet resolved. In this paper, long-term data that include output of tower, radiation, surface turbulence flux and soil measurement collected from September 2006 to August 2010 in the Semi-Arid Climate Change and Environment Observatory, Lanzhou University, in the semi-arid Loess Plateau of Northwest China, were analysed, focusing on the seasonal characteristics of the surface energy and the factors that have impact on the energy balance closure (EBC. The analysis shows that (1 the long-term observations are successful; the interaction between the land and the atmosphere in semi-arid climates can be represented by the turbulent transport of energy. In addition, even though the residual is obvious, this suggests that the factors that impact the EBC are stable, and their seasonal variations are identical. The analysis also shows that (2 four factors have obvious impact on the EBC: the diverse schemes for surface soil heat flux, the flux contribution from the target source area, the low-frequency part of the turbulence spectra, and the strength of atmospheric turbulence motion. The impact of these four factors on the EBC are similar in all seasons. Lastly, the results indicate that (3 atmospheric turbulence intensity is a very important factor in terms of its impact on the EBC. The relative turbulence intensity, RIw, characterises the strength of atmospheric turbulence motion, and is found to exert a noticeable impact on the EBC; in all seasons, the EBC is increased when the relative turbulence intensity is enlarged.

  12. Warmer and Wetter Soil Stimulates Assimilation More than Respiration in Rainfed Agricultural Ecosystem on the China Loess Plateau: The Role of Partial Plastic Film Mulching Tillage.

    Directory of Open Access Journals (Sweden)

    Daozhi Gong

    Full Text Available Effects of agricultural practices on ecosystem carbon storage have acquired widespread concern due to its alleviation of rising atmospheric CO2 concentrations. Recently, combining of furrow-ridge with plastic film mulching in spring maize ecosystem was widely applied to boost crop water productivity in the semiarid regions of China. However, there is still limited information about the potentials for increased ecosystem carbon storage of this tillage method. The objective of this study was to quantify and contrast net carbon dioxide exchange, biomass accumulation and carbon budgets of maize (Zea maize L. fields under the traditional non-mulching with flat tillage (CK and partial plastic film mulching with furrow-ridge tillage (MFR on the China Loess Plateau. Half-hourly net ecosystem CO2 exchange (NEE of both treatments were synchronously measured with two eddy covariance systems during the growing seasons of 2011 through 2013. At same time green leaf area index (GLAI and biomass were also measured biweekly. Compared with CK, the warmer and wetter (+1.3°C and +4.3% top soil at MFR accelerated the rates of biomass accumulation, promoted greater green leaf area and thus shortened the growing seasons by an average value of 10.4 days for three years. MFR stimulated assimilation more than respiration during whole growing season, resulting in a higher carbon sequestration in terms of NEE of -79 gC/m2 than CK. However, after considering carbon in harvested grain (or aboveground biomass, there is a slight higher carbon sink (or a stronger carbon source in MFR due to its greater difference of aboveground biomass than that of grain between both treatments. These results demonstrate that partial plastic film mulched furrow-ridge tillage with aboveground biomass exclusive of grain returned to the soil is an effective way to enhance simultaneously carbon sequestration and grain yield of maize in the semiarid regions.

  13. Comparative analysis of land use/cover change trajectories and their driving forces in two small watersheds in the western Loess Plateau of China

    Science.gov (United States)

    Wang, Dongchuan; Gong, Jianhua; Chen, Liding; Zhang, Lihui; Song, Yiquan; Yue, Yujuan

    2013-04-01

    To prevent soil loss and achieve better ecological environments, soil conservation measures have been taken during the past decades in the western Loess Plateau of China. In this paper, a case study was taken in Luoyu valley and Lver valley, two sub-watersheds of Xihe watershed and comparison was carried out between them. The main object of this study is to monitor land use/cover changes in the two similar small watersheds utilizing SPOT5 imageries by object-oriented human-computer interactive classification method, further develop the method of spatio-temporal analysis of land use/cover change by using pattern metrics of change trajectories and relative land use suitability index (R) in smaller watersheds, and make comparisons between the two similar small watersheds, taking water and soil conservation measures into consideration. Results show that combining GIS and RS, this method can be perfectly applied to make comparisons between different small watersheds with similar geographical backgrounds. And land use/cover spatiotemporal dynamic change characteristics can be preferably expressed by pattern metrics of change trajectories and R values based on topographical data. Different emphases have been laid according to their own geological backgrounds in the two watersheds and human activities have different effects on the landscapes of the two watersheds. The main change pattern is from slope farmland to terrace (322, the largest in Luoyu valley) or to economic fruit forest (344, the largest in Lver valley). R value of every slope grade in both of the two watersheds drops with the rising of slope degree on the whole and it shows that there is still much to do for people in the two watersheds in consideration that all the R values are still lower than 0.7.

  14. Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework.

    Science.gov (United States)

    Gao, Guangyao; Fu, Bojie; Wang, Shuai; Liang, Wei; Jiang, Xiaohui

    2016-07-01

    Understanding and quantifying the impacts of land use/cover change and climate variability on hydrological responses are important to the design of water resources and land use management strategies for adaptation to climate change, especially in water-limited areas. The elasticity method was used to detect the responses of streamflow and runoff coefficient to various driving factors in 15 main catchments of the Loess Plateau, China between 1961 and 2009. The elasticity of streamflow (Q) and runoff coefficient (Rc) to precipitation (P), potential evapotranspiration (E0), and catchment characteristics (represented by the parameter m in Fu's equation) were derived based on the Budyko hypothesis. There were two critical values of m=2 and E0/P=1 for the elasticity of Q and Rc. The hydrological responses were mainly affected by catchment characteristics in water-limited regions (E0/P>1), and in humid areas (E0/P2 whereas catchment characteristics had a greater impact for cases of mland use/cover change and P reduction to decreased Q were 64.75% and 41.55%, respectively, while those to decreased Rc were 75.68% and 32.06%, respectively. In contrast, the decreased E0 resulted in 6.30% and 7.73% increase of Q and Rc, respectively. The contribution of land use/cover changes was significantly and positively correlated with the increase in the percentage of the soil and water conservation measures area (p<0.05). The Rc significantly and linearly decreased with the vegetation coverage (p<0.01). Moreover, the Rc linearly decreased with the percentage of measures area in all catchments (eight of them were statistically significant with p<0.05).

  15. An experimental study of land surface condense phenomenon and water budget characteristics over the Loess Plateau%黄土高原陆面水分的凝结现象及收支特征试验研究

    Institute of Scientific and Technical Information of China (English)

    张强; 王胜; 问晓梅; 南玉合; 曾剑

    2012-01-01

    中国黄土高原是全球独特的地理区域,其陆面水分过程比较特殊.利用黄土高原陆面过程试验研究(LOPEX)的陇中黄土高原定西陆面过程综合观测站的资料,分析了陆面水分凝结现象及其出现频率与局地微气象条件的关系,研究了露水(霜)量及其出现频率的季节分布特征以及受降水和天气阴、晴的影响规律.同时,对比分析了降水、露水、雾水和土壤吸附水对陆面水分的贡献率,讨论了涡动相关法、蒸渗计和蒸发皿观测的陆面蒸发量的差别及其与陆面水分来源的年平衡关系,给出了半干旱区陆面水分平衡的日循环特征.发现露水对风速、大气湿度、近地层温度梯度的依赖很强,一般在风速为1.5 m/s、相对湿度大于80%和逆温强度为0.25℃的情况下露水(霜)量最大;刚降水后的晴天露水量比较大;实际蒸散量与蒸发力的差距十分明显,陆面水分平衡特征表现为一个“呼吸”过程.%The Chinese Loess Plateau is a unique area in the world, dominated by a semi-arid climate with unusual land surface hydrology. The previous studies have paid little attention to the non-precipitation land surface hydrological processes, such as dew formation, on the semi-arid Loess Plateau. Therefore, it is important to improve our understanding of the micrometeoro-logical conditions controlling dew formation and the main characteristics of the land surface water balance. Here, we have analysed the observation data on land surface processes, collected at the Dingxi observational station in the LOPEX experimental area, to investigate the relationships between dewfall (or frost) amount and micrometeorological conditions, the characteristics of the seasonal distribution of dewfall (frost) and the influence of precipitation and other weather conditions on dewfall (frost). The fractional contributions of precipitation, dewfall, fog and soil-adsorbed water to the land surface water

  16. Evaluation of the Soil Water Index and Surface Soil Moisture on the Loess Plateau%土壤湿度指数在黄土高原的适宜性评价

    Institute of Scientific and Technical Information of China (English)

    蒋冲; 王飞; 穆兴民; 李锐

    2012-01-01

    In this paper,the capability of the European Remote Sensing Satellite(ERS) scatterometer-derived soil water index(SWI) and surface soil moisture(SSM) data which are retrieved by a change detection method,developed at the Institute of Photogrammetry and Remote Sensing(IPF),Vienna University of Technology(TU-Wien) to disclose soil moisture and precipitation distribution on Loess Plateau is investigated with the help of GIS,remote sensing and correlation analysis.Monthly averaged SWI/SSM data for the years 1992—2000 are analyzed to evaluate the use of the SWI/SSM as an index to monitor soil moisture on Loess Plateau and to investigate whether it can reflects general precipitation distribution characteristics in this area or not.Monthly averaged in situ relative soil moisture and monthly precipitation data from Chinese meteorological gauge stations are employed to perform comparisons with SWI/SSM on point and regional scales.The result is that in different land use,soil texture and topography conditions SWI/SSM correlate well with precipitation and in situ relative soil moisture,most of them reach significant level,they have same change tendency,SWI and precipitation have similar spatial distribution characteristics.Among the seven stations,there is a good correlation between precipitation and soil water content(SWI and in situ relative soil moisture),especially for first 10 cm layer,the correlation between precipitation and SWI is better than that of precipitation and in situ moisture.The results show that SWI/SSM can relative accurately disclose soil moisture variation and spatial distribution characteristic on the Loess Plateau.Furthermore,the freely available 20-yr(1992—2011) time series SWI/SSM data are thus a valuable tool to overcome the scarcity of in situ soil moisture observation,which are usually not available on regional scale.%利用1992—2000年间黄土高原地区逐月降雨量、实测土壤湿度数据,结合GIS遥

  17. Restoring the Ecoenvironment in Conformity to Natural Law-- Some Considerations on the Vegetation Restoration on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Tian Junliang

    2003-01-01

    @@ The fragile eco-environment in the west of China has become a bottleneck in the region' s development. When putting the national strategy of developing the western region into practice, the central authorities list the rehabilitation of the depleted eco-environment as one of the key infrastructure programs for the whole country, urging people to return farmland to its original state of forest or grassland. This move is not only conducive to the development of the western region,but also of far-reaching and vital significance to the sustainable development of the whole country and even to the future survival of the Chinese nation.

  18. Pedogenesis affecting the Matuyama-Brunhes polarity transition recorded in Chinese loess?

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A detailed record of the Matuyama-Brunhes (M-B) transition has been obtained from the loess unit 8 (L8) at Duanjiapo (34.2°N, 109.2°E),Shannxi Province of China. An investigation of the rock magnetic properties using hyste-resis loops, thermomagnetic analyses identifies pseudo- single domain magnetite as the main carrier of the remanence, with a small contribution from maghemite and hematite. The paleo-direction records obtained reveal: (ⅰ) The M-B transition was recorded in the middle and lower part of L8, and comprises of five fast reversals. (ⅱ) The duration of the M-B polarity transition related to the directional change is about 4800 a. (ⅲ) The virtual geomagnetic pole (VGP) path during the transition is confined over Africa, peaked 90° away from the sampling site, in contrast with the results obtained from the Weinan loess section. The different VGPs are probably attributed to the pedogenesis.

  19. Sustainability of Smallholder Agriculture in Semi-Arid Areas under Land Set-aside Programs: A Case Study from China’s Loess Plateau

    Directory of Open Access Journals (Sweden)

    Qirui Li

    2016-04-01

    Full Text Available This article analyzes agricultural sustainability in the context of land degradation, rural poverty and social inequality, taking China’s Loess Hills as an example. The analysis attempts to understand the multi-dimensionality of sustainability at the farm level and its relationship with physical-socio-economic-infrastructural-technological framework conditions in the context of the land set-aside program viz. the Grain for Green Project (GGP. We developed composite indices of sustainability and its environmental, economic and social dimensions using a principal component analysis (PCA-based weighting scheme. Regression analyses were conducted to examine the relationship between the estimated sustainability indicators and the variables representing framework conditions of knowledge, demographics, resource endowment and production techniques. The stated analysis was conducted on a dataset collected by means of household surveys in 2014 in valleys and flood plain areas in Yanhe Township. Findings reveal hidden correlations among the indicators of environmental, economic, and social pillars of sustainability. The ratio of land under the conservation program to actual farmland emerged as a key determinant of overall agricultural sustainability and its social dimension, which reaches the maximum when the ratio is around 0.56 and 0.64, respectively. The results also show that there is need to balance off-farm and on-farm income diversification as well as highlight the role of women in ensuring the sustainability of farming households. The core achievement of the article is the definition of the thresholds for the land set-aside program and the identification of major determinants of agricultural sustainability in the rural Chinese context in particular and in rural farming communities in general.

  20. Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework.

    Science.gov (United States)

    Gao, Guangyao; Fu, Bojie; Wang, Shuai; Liang, Wei; Jiang, Xiaohui

    2016-07-01

    Understanding and quantifying the impacts of land use/cover change and climate variability on hydrological responses are important to the design of water resources and land use management strategies for adaptation to climate change, especially in water-limited areas. The elasticity method was used to detect the responses of streamflow and runoff coefficient to various driving factors in 15 main catchments of the Loess Plateau, China between 1961 and 2009. The elasticity of streamflow (Q) and runoff coefficient (Rc) to precipitation (P), potential evapotranspiration (E0), and catchment characteristics (represented by the parameter m in Fu's equation) were derived based on the Budyko hypothesis. There were two critical values of m=2 and E0/P=1 for the elasticity of Q and Rc. The hydrological responses were mainly affected by catchment characteristics in water-limited regions (E0/P>1), and in humid areas (E0/Pclimate conditions played a more important role for cases of m>2 whereas catchment characteristics had a greater impact for cases of m<2. The annual Q and Rc in 14 of the 15 catchments significantly decreased with average reduction of 0.87mmyr(-1) and 0.18%yr(-1), respectively. The mean elasticities of Q to P, E0 and m were 2.66, -1.66 and -3.17, respectively. The contributions of land use/cover change and P reduction to decreased Q were 64.75% and 41.55%, respectively, while those to decreased Rc were 75.68% and 32.06%, respectively. In contrast, the decreased E0 resulted in 6.30% and 7.73% increase of Q and Rc, respectively. The contribution of land use/cover changes was significantly and positively correlated with the increase in the percentage of the soil and water conservation measures area (p<0.05). The Rc significantly and linearly decreased with the vegetation coverage (p<0.01). Moreover, the Rc linearly decreased with the percentage of measures area in all catchments (eight of them were statistically significant with p<0.05). PMID:27016681

  1. A comparison between soil loss evaluation index and the C-factor of RUSLE: a case study in the Loess Plateau of China

    Directory of Open Access Journals (Sweden)

    W. W. Zhao

    2012-08-01

    Full Text Available Land use and land cover are most important in quantifying soil erosion. Based on the C-factor of the popular soil erosion model, Revised Universal Soil Loss Equation (RUSLE and a scale-pattern-process theory in landscape ecology, we proposed a multi-scale soil loss evaluation index (SL to evaluate the effects of land use patterns on soil erosion. We examined the advantages and shortcomings of SL for small watershed (SLsw by comparing to the C-factor used in RUSLE. We used the Yanhe watershed located on China's Loess Plateau as a case study to demonstrate the utilities of SLsw. The SLsw calculation involves the delineations of the drainage network and sub-watershed boundaries, the calculations of soil loss horizontal distance index, the soil loss vertical distance index, slope steepness, rainfall-runoff erosivity, soil erodibility, and cover and management practice. We used several extensions within the geographic information system (GIS, and AVSWAT2000 hydrological model to derive all the required GIS layers. We compared the SLsw with the C-factor to identify spatial patterns to understand the causes for the differences. The SLsw values for the Yanhe watershed are in the range of 0.15 to 0.45, and there are 593 sub-watersheds with SLsw values that are lower than the C-factor values (LOW and 227 sub-watersheds with SLsw values higher than the C-factor values (HIGH. The HIGH area have greater rainfall-runoff erosivity than LOW area for all land use types. The cultivated land is located on the steeper slope or is closer to the drainage network in the horizontal direction in HIGH area in comparison to LOW area. The results imply that SLsw can be used to identify the effect of land use distribution on soil loss, whereas the C-factor has less power to do it. Both HIGH and LOW areas have similar soil erodibility values for all land use types. The average vertical

  2. Assessing and regulating the impacts of climate change on water resources in the Heihe watershed on the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Climate change can cause considerable changes in water resources and assessing the potential impacts can provide important information for regional sustainable development. The objectives were to evaluate the possible impacts of climate change during 2010-2039 on water resources (runoff, soil water content, and evapotranspiration) in the Heihe watershed on the Loess Plateau of China and to further explore adaptive measures to cope with the changes. Projections of four climate models (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emission scenarios (A2, B2, and GGa) were used to estimate future changes in precipitation, maximum and minimum temperature based on Change Factor method. The Soil and Water Assessment Tool (SWAT) was employed to simulate the hydrologic responses to climate changes. The CA-Markov model was used to develop land use scenarios. Compared with the present climate, the climate models predicted a -2.3% to 7.8% change in annual precipitation, 0.7 to 2.2°C rises in maximum temperature, and 1.2 to 2.8°C rises in minimum temperature. Without consideration of land use change, SWAT predicted a -19.8% to 37.0% change for runoff, -5.5% to 17.2% change for soil water content, and 0.1% to 5.9% increase for evapotranspiration during 2010–2039 under all climate scenarios. Though the change of hydrometeorolocial variables are complex, they would possibly increase with great probability, and the hydrological regime would be influenced such as a decrease in runoff in winter months. With land use changes, the projected land use of 2015 would increase soil water content by 4.0% and surface runoff by 5.7% while slightly decrease evapotranspiration by 0.6% compared with the 2000 land use. This result showed that adjustment of land use patterns was capable of regulating water resources and could be used to mitigate the adverse effects of climate change.

  3. Temporal stability of soil moisture under different land uses/cover in the Loess Plateau based on a finer spatiotemporal scale

    Directory of Open Access Journals (Sweden)

    J. Zhou

    2013-08-01

    Full Text Available The Temporal stability of soil moisture (TSSM is an important factor to evaluate the value of available water resources in a water-controlled ecosystem. In this study we used the evapotranspiration-TSSM (ET-TSSM model and a new sampling design to examine the soil water dynamics and water balance of different land uses/cover types in a hilly landscape of the Loess Plateau under a finer spatiotemporal scale. Our primary focus is to examine the difference among soil water processes, including the wet-to-dry (WTD process triggered by precipitation and the dry-to-wet (DTW process caused by radiation among varied land uses/cover types. Three vegetation types and bare land were selected in the sampling scheme. For each land uses/cover type, four microplots (60 cm × 60cm were established, and the soil moisture was measured at the central point (CP and four ambient points (AP. The results indicated that (1 the bare land (plot1 was sensitive to the influence of rainfall and radiation compared with other land uses types; (2 Andropogon (plot2 and Spiraea pubescens (plot4 more efficiently represented the average soil moisture of the different land uses/cover in the WTD and DTW processes, respectively, in the CP position. In contrast, the bare land and Artemisia coparia (plot3 seemed to be more representative of the average soil water content in the AP position; (3 the ET-TSSM model demonstrated that, in the WTD processes, although Spiraea pubescens land use reached the net deficit of the soil water storage condition was longest, the vegetated land uses have a higher capacity of water consumption than bare land and more easily affected the serious condition of the soil water deficiency at the end of WTD processes. We concluded that a finer spatiotemporal scale in the TSSM study could be a new method to describe the effect of plant on soil moisture dynamics triggered by precipitation or radiation and that the improvement of the application of the TSSM

  4. [Effects of land use change on soil active organic carbon in deep soils in Hilly Loess Plateau region of Northwest China].

    Science.gov (United States)

    Zhang, Shuai; Xu, Ming-Xiang; Zhang, Ya-Feng; Wang, Chao-Hua; Chen, Gai

    2015-02-01

    Response of soil active organic carbon to land-use change has become a hot topic in current soil carbon and nutrient cycling study. Soil active organic carbon distribution characteristics in soil profile under four land-use types were investigated in Ziwuling forest zone of the Hilly Loess Plateau region. The four types of land-use changes included natural woodland converted into artificial woodland, natural woodland converted into cropland, natural shrubland converted into cropland and natural shrubland converted into revegetated grassland. Effects of land-use changes on soil active organic carbon in deep soil layers (60-200 cm) were explored by comparison with the shallow soil layers (0-60 cm). The results showed that: (1) The labile organic carbon ( LOC) and microbial carbon (MBC) content were mainly concentrated in the shallow 0-60 cm soil, which accounted for 49%-66% and 71%-84% of soil active organic carbon in the profile (0-200 cm) under different land-use types. Soil active organic carbon content in shallow soil was significantly varied for the land-use changes types, while no obvious difference was observed in soil active organic carbon in deep soil layer. (2) Land-use changes exerted significant influence on soil active organic carbon, the active organic carbon in shallow soil was more sensitive than that in deep soil. The four types of land-use changes, including natural woodland to planted woodland, natural woodland to cropland, natural shrubland to revegetated grassland and natural shrubland to cropland, LOC in shallow soil was reduced by 10%, 60%, 29%, 40% and LOC in the deep layer was decreased by 9%, 21%, 12%, 1%, respectively. MBC in the shallow soil was reduced by 24% 73%, 23%, 56%, and that in the deep layer was decreased by 25%, 18%, 8% and 11%, respectively. (Land-use changes altered the distribution ratio of active organic carbon in soil profile. The ratio between LOC and SOC in shallow soil increased when natural woodland and shrubland were

  5. Evolution of Chinese mammalian faunal regions and elevation of the Qinghai-Xizang (Tibet) Plateau

    Institute of Scientific and Technical Information of China (English)

    QIU; Zhuding; LI; Chuankui

    2005-01-01

    On the basis of mammal's high evolutionary rates and sensitivity to environment, this paper deals with the evolutionary history of the Chinese Cenozoic mammals and environmental changes, and explores the relationship between the uplift of the Qinghai-Xizang Plateau and the evolution of zoogeographic provinces of China, through studying fossil mammal and the lithological characters of fossil-bearing beds. Evolutionary tendency and distribution of the mammals demonstrate that the uplift of the Qinghai-Xizang region, onset of the Asian monsoon and differentiation of the mammalian distribution probably initiated in Oligocene. The elevation of the Plateau seems to be a gradual and relatively stable process, and the uplift not only has resulted in significant environmental changes in Asia, but also caused distinct regional differentiation of mammals in China since the middle Miocene, and as a consequence the modern zoogeographic provinces gradually took shape.

  6. Decomposition of different plant litters in Loess Plateau of Northwest China%黄土高原不同植物凋落物的分解特性

    Institute of Scientific and Technical Information of China (English)

    李云; 周建斌; 董燕捷; 夏志敏; 陈竹君

    2012-01-01

    Taking the litters of species Hippophae rhamnoides, Medicago sativa, Populus simonii, Robinia pseudoacaci, Salix psammophila, and Stipa bungeana in the Loess Plateau of Northeast China as test objects, and by using mesh bags, this paper studied the dynamic changes of the litters mass, carbon, and nitrogen during decomposition after buried in the field in semiarid region. The litters buried were from one, two, or three of the plant species, and mixed thoroughly with equal proportion of masses. During decomposition, the mass loss rate, total carbon and nitrogen release rates, and total soluble carbon and nitrogen contents of different litters were higher at the early than at the later decomposition stage. After 412 d decomposition, the average mass loss rate of the litters was in the order of mixed litters of three plant species > mixed litters of two plant species > one plant species litter. By the end of this experiment, the average release rates of the litter total carbon and nitrogen ranked as one plant species litter > mixed litters of two plant species > mixed litters of three plant species, the litter soluble organic carbon content was mixed litters of two plant species > mixed litters of three plant species > one plant species litter, while the litter soluble total nitrogen content was mixed litters of three plant species > mixed litters of two plant species > one plant species litter. Correlation analysis showed that the utter mass loss rate had definite correlation with the litter soluble organic matter, especially soluble organic carbon. From the viewpoint of mass loss rate, the mixture of the litters of P. simonii, H. rhamnoide, and M. sativa was the optimum. It was suggested that in the process of returning farmland into forestland and grassland in the gully and valley region of Loess Plateau, it would be required to rationally increase plant species diversity to improve soil fertility.%以黄土高原区典型植物刺槐、小叶杨、沙棘、沙柳

  7. Elemental tracers for Chinese source dust

    Institute of Scientific and Technical Information of China (English)

    张小曳; 张光宇; 朱光华; 张德二; 安芷生; 陈拓; 黄湘萍

    1996-01-01

    The mass-particle size distributions of 10 dust-carrying elements in aerosol particles were determined tor 12 sites in desert regions of northern China. The desert dust is proved to he of origin of eolian loess deposited on the Loess Plateau. Their transport to the loess was mainly attributable to the non-dust storm processes under the interglacial climate condition. The impact ot" dust storm on the accumulation of the loess increased in the glacial stage. On the basis of the signatures of 4 dust elements (Al. Fe, Mg and Sc). Chinese dust is believed to have 3 major desert sources (northwestern deserts, northern high dust deserts and northern low dust deserts). With a chemical element balance model, an elemental tracer system is established to proportion the export of China-source dust.

  8. Sr-Nd isotope geochemistry of eolian dust of the arid-semiarid areas in China: Implications for loess provenance and monsoon evolution

    Institute of Scientific and Technical Information of China (English)

    RAO Wenbo; YANG Jiedong; CHEN Jun; LI Gaojun

    2006-01-01

    Minerals and rocks have distinct 87Sr/86Sr and 143Nd/144Nd ratios, depending on their geological origin and ages, and these isotope ratios are less altered than elemental composition during transport in the atmosphere or after deposition as sediments, thus stable isotopes of Sr and Nd have great potential as tracers for provenance and transport of materials. During the hypergene process, Sr isotope ratios of sediments are controlled by their parent rocks, particle sizes and chemical weathering. In general, the higher the Sr isotope ratios of parent rocks, and/or the more the fine-grained fractions, and/or the stronger the chemical weathering, thus the higher the Sr isotope ratios of sediments. On the contrary, there are lower Sr isotope ratios of sediments. Nd isotope ratios of sediments, independent of their particle sizes and chemical weathering, are only associated with parent rocks. For the provenance of the Chinese Loess Plateau, different reseachers drew discordant and even contradictory conclusions by using the method of Sr-Nd isotopic tracing. From the previous Nd isotope data, it is considered that the Tarim Basin, deserts in the central and west parts of Inner Mongolia and the Tibetan Plateau are the main sources of the Chinese Loess Plateau, and are also manufacturers for eolian dust of the Far East regions, together with the Chinese Loess Plateau. Sr isotope ratios of eolian dust are solely affected by wind sorting and weathering-pedogenesis due to its homogeneous composition in the Chinese Loess Plateau. Wind sorting is related to the East Asian winter monsoon but weathering-pedogenesis is mainly associated with the East Asian summer monsoon. Studies on Sr isotopic compositions of the loess-paleosol sequence suggest that 87Sr/86Sr ratios in acid-soluble materials are an index for chemical weathering intensity of the Chinese Loess Plateau, indicating the East Asian summer monsoon variations, whereas 87Sr/86Sr ratios in acid-insoluble materials are

  9. A comparison of the soil loss evaluation index and the RUSLE Model: a case study in the Loess Plateau of China

    Directory of Open Access Journals (Sweden)

    W. W. Zhao

    2012-02-01

    Full Text Available The development of new methods to examine the influence of land use on soil erosion is currently a popular research topic in contemporary research. The multiscale Soil Loss Evaluation Index is a new, simple soil erosion model that can be used to evaluate the relationship between land use and soil erosion; however, applications of this model have been limited, and a comparison with other soil erosion models is needed.

    In this study, we used the Yanhe watershed in China's Loess Plateau as a case study to calculate the Soil Loss Evaluation Index at the small watershed scale (SLsw, to identify the similarities and differences between results from the Soil Loss Evaluation Index and the Revised Universal Soil Loss Equation (RUSLE, and to determine the key location where land use patterns need to be optimized in the study area.

    The procedure for calculating the SLsw, namely, using the delineation of the drainage network and the sub-watersheds as starting points, includes the calculation of soil loss horizontal distance index, the soil loss vertical distance index, slope steepness factor, rainfall-runoff erosivity factor, soil erodibility factor, and cover and management practices factor. During the calculation procedure, several functions within geographic information system (GIS, especially the spatial analyst function, are used to calculate these factors layers, and many of the data are expressed in grid format. Moreover, The AVSWAT2000 hydrological model and upscaling methods were used to calculate some of the factors in this study.

    When comparing the SLsw with the RUSLE, some similarities and differences were discovered. The similarities of the two models include the following: (1 both use GIS techniques at the watershed scale, (2 the same factors appear in both models, (3 and the resolution of the basic data is closely related to the evaluation results. The differences between the SL

  10. Quantitative measurements on the paleo-weathering intensity of the loess-soil sequences and implication on paleomonsoon

    Institute of Scientific and Technical Information of China (English)

    HAO; Qingzhen

    2001-01-01

    [1]Liu, T. S., Loess and the Environment, Beijing: China Ocean Press, 1985, 1-251.[2]Chen, L. X., Zhu, Q. G., Luo, H. B. et al., East Asian Monsoon, Beijing: China Meteorology Press, 1991, 28-61.[3]An, Z. S., Liu, T. S., Lu, Y. C. et al., The long-term palaeomonsoon variation recorded by the loess-palaeosol sequence in central China, Quaternary International, 1990, (7/8): 91-95.[4]Guo, Z. T., Liu, T. S., Fedoroff, N. et al., Shift of the monsoon intensity on the Loess Plateau at ca. 0.85 MaBP, Chinese Science Bulletin, 1993, 38(2): 586-591.[5]Chen, J., An, Z. S., Wang, Y. J. et al., Distributions of Rb and Sr in the Luochuan loess-paleosol sequence of China during the last 800 ka: Implications for paleomonsoon variations, Science in China, Ser. D, 1999, 42(3): 225-232.[6]Chen, J., Wang, Y. J., Ji, J. F. et al., Rb/Sr variations and its climatic stratigraphical significance of a loess-paleosol profile from Luochuan, Shaanxi Province, Quaternary Sciences (in Chinese), 1999, 19(4): 350-356.[7]Guo, Z. T.,Liu, T. S., Fedoroff, N. et al., Climate extremes in loess of China coupled with the strength of deep-water for-mation in the North Atlantic, Global and Planetary Change, 1998, 18: 113-128.[8]Guo, Z. T., Liu, T. S., An, Z. S., Paleosols of the last 0.15 Ma in the Weinan loess section and their paleoclimate signifi-cance, Quaternary Sciences (in Chinese), 1994, 14(3): 256-269.[9]Guo, Z, T,, Fedoroff, N., Liu, T. S., Micromorphology of the loess-paleosol sequence of the last 130 ka in China and pa-leoclimatic event, Science in China (in Chinese), Ser. D, 1996, 26(3): 392-398.[10]Guo, Z., Liu, T., Guiot, J., et al., High frequency pulses of East Asian monsoon climate in the last two glaciations: Link with the North Atlantic, Climate Dynamics, 1996, 12: 701-709.[11]Guo, Z. T., Peng, S. Z., Wei, L. Y. et al., Weathering signals of Millennial-Scale oscillations of the East Asian Summer monsoon over the last 220 ka, Chinese Science

  11. Effects of land-use pattern change on rainfall-runoff and runoff-sediment relations:a case study in Zichang watershed of the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wen-wu; FU Bo-jie; CHEN Li-ding; ZHANG Qiu-ju; ZHANG Yin-hui

    2004-01-01

    The purpose of this article is to identify the effect of land-use pattern on rainfall-runoff and runoff-sediment relations in Zichang watershed of the Loess Plateau. From 1986 to 1997, many farmlands changed into grassland or woodland, especially the farmland in steep slope positions or far away from the river. The change of land-use pattern altered the rainfall-runoff and runoff-sediment relationships, and led to higher slope of trend curves(STCs) of annual rainfall-runoff mass curve and runoff-sediment mass curve in 1990s than that in 1980s. It is implied that more soil and water loss yielded in 1990s. In order to reduce soil loss, more attentions should be paid to land-use pattern and some grass or other herbaceous filter strips should be built along rivers.

  12. Soil moisture consumption and ecological effects in alfalfa grasslands in Longdong area of Loess Plateau%陇东黄土高原苜蓿草地土壤水分消耗及水分生态效应

    Institute of Scientific and Technical Information of China (English)

    胡守林; 贾志宽; 万素梅

    2009-01-01

    Soil desiccation is the most serious problem, which leads to widespread land degradation in the Loess Plateau of China. Hence, it has important theoretical significance to study the consumption patterns of soil moisture in alfalfa grasslands so as to realize sustainable agricultural development and ecological environment rehabilitation in the entire Loess Plateau. Changes of soil moisture characteristics in 0-1000 cm soil and the effects on ecological environment of soil moisture in alfalfa grasslands were investigated. The results showed that: (1) In 0-1000 cm soil, the grasslands with alfalfa growing for four years, six years had the best soil moisture conditions, while the grasslands with alfalfa growing for twelve years, eighteen years and twenty-six years had the poorest soil moisture conditions. (2) In the Loess Plateau, emerging regional and extent of dry soil layer differed in alfalfa grasslands. (3) The grasslands with alfalfa growing for four years, six years and eight years did not produced unfavorable impacts on ecological environments of soil moisture, but the grasslands with alfalfa growing for twelve years, eighteen years and twenty six years had a profound negative impact on ecological environments of soil moisture. The study considered that in Longdong Loess Plateau, grass-crop rotation should be practiced to recover soil moisture so as continue to raise land productivity, after alfalfa grew for more than six years.%黄土高原地区土壤干化导致林草植被大面积衰退,研究苜蓿草地土壤水分消耗规律对该区农业持续发展及生态环境恢复具有重要的理论意义.该文研究了黄土高原地区不同生长年限苜蓿草地1 000 cm土层土壤水分的变化特征及其对土壤水分生态环境的影响.结果表明:在0~1 000 cm土层,4年、6年生苜蓿草地土壤水分条件最好;12年、18年、26年生苜蓿草地土壤水分条件最差.在黄土高原地区,苜蓿地土壤干层出现的

  13. [Soil anti-erodibility of abandoned lands during different succession stages of plant community in hilly-gullied region of the Loess Plateau: Take Fangta small watershed as an example].

    Science.gov (United States)

    Yan, Fang-chen; Jiao, Ju-ying; Cao, Bin-ting; Yu, Wei-jie; Wei, Yan-hong; Kou, Meng; Hu, Shu

    2016-01-01

    Field survey and laboratory experiment were conducted to study the soil anti-erodibility of abandoned croplands during different vegetation succession stages in hilly-gullied region of the Loess Plateau, based on the analysis of soil particle composition, size distribution and group characteristics, soil aggregate fractal dimensions and stability. The results showed that in the earlier stages of succession from annual to perennial herbs in abandoned croplands, soil size distribution changed a little bit, the fractal dimension of soil particle increased, soil structure improved, fractal dimension and damage percent of soil aggregate structure decreased, soil stability increased, thus soil anti-erodibility increased. Therefore, natural restoration of vegetation is of great significance to improve the soil structure, increase soil erosion resistance, reduce soil erosion and promote sustainable development of regional ecological environment.

  14. 陕北黄土高原蔷薇科药用植物资源及开发利用研究%Study on Resources and Exploitation of Rosaceae Medicinal Plants in Loess Plateau of Northern Shaanxi

    Institute of Scientific and Technical Information of China (English)

    贺游利

    2011-01-01

    24 species of wild medicinal plants of Rosaceae belonging to 16 genera were found in Loess Plateau of Northern Shaanxi, whose roots, flowers or fruits could be used in medicine for curing many diseases. Chemical components of Rosaceae medicinal plants were complicated, mainly containing organic acids, cyanogenic glycosides, polyphenol, alkaloids, flavonoids and triterpenoid compound. The resources species, habitat, biological characteristics, medicinal part and efficacy of Rosaceae medicinal plants in Loess Plateau of Northern Shaanxi were investigated and summarized through field collection, system surveys and consultation on relevant literature. Based on their unique characteristics, some suggestions and strategies were put forward accordingly for further protection and exploration of local medicinal resources of Rosaceae.%陕北黄土高原蔷薇科野生药用植物资源有16个属24种,常以根、花或果实入药,其化学成分复杂,含有有机酸、氰苷、多元酚类、生物碱类、黄酮类和三萜类化合物等多种活性物质,对多种疾病有明显疗效.通过野外采集、系统调查、查阅有关文献资料等方式,对陕北黄土高原地区蔷薇科药用植物资源种类、生境、生物学特征、药用部位及其功效进行了调查研究和归纳总结,并根据当地蔷薇科药用植物的特点提出今后对其资源保护及开发利用的建议和措施.

  15. Spatio-temporal Difference of Economic Growth in the Loess Plateau Region over the Past 20 Years%近20年来黄土高原地区的经济增长时空分异特征

    Institute of Scientific and Technical Information of China (English)

    刘艳华; 徐勇; 刘毅

    2012-01-01

    经济不均衡增长是区域发展的一种常态.分析区域经济增长时空差异及成因,对于认识和加快落后地区的经济发展具有重要的意义.本研究在GIS技术的支持下,对黄土高原地区近20年来以县市为单元的经济增长时空分异特征进行了系统的分析.主要结论有:改革开放以来,黄土高原地区的GDP水平呈现出持续的快速增长态势.近20年来,陕北和内蒙古鄂尔多斯地区增长最为迅速;人均GDP的空间分布整体上呈现出“两高一低”的带状分布格局,且这种格局明显地受到极化增长的扰动和重塑;经济增长表现出显著的极化增长特征,且经济增长极的极化作用与增长极之间地位的调整是同时进行的;与常态化的城市产业集聚推动型经济相比,机遇性的资源开发拉动型经济对人均GDP的拉动速度更快,但可持续性较差.未来,黄土高原地区应走以中心城市带动为主,以能矿产资源开发拉动为辅,两者相互促进,共同带动整个区域经济更快、更好、更可持续地发展的道路.%Economic activities are always located unevenly in a region. Analyzing and detecting the spatio-temporal difference of economic factors, and finding out the underlying reasons would be very useful for undeveloped regions to recognize problems and then seek for a better way to deal with them. Under support of GIS, this essay analyzed the spatio-temporal characteristics of economy growth on the Loess Plat-eau Region over the past 20 years by using data of 284 counties' per capita GDP. And the results included: (1) The level of GDP of the Loess Plateau Region had been growing continuously and rapidly since the Reform and Opening of China. And the Western Development Strategy of China is the main reason for the rapid increase of proportion of GDP of the Loess Plateau Region in that of the whole China since 2000, while energy/resources exploring in Shanxi, Shaanxi and Inner Mongolia Region

  16. Magnetic properties and paleoclimatic implications of loess-paleosol

    Institute of Scientific and Technical Information of China (English)

    ZHU; Rixiang

    2001-01-01

    in China, Ser. B, 1995, 38(2): 238-244.[14]Zhu, R. X., Zhou, L. P., Laj, C. et al., The Blake geomagnetic polarity episode recorded in Chinese Loess, Geophys. Res. Lett., 1994, 21(8): 697-700.[15]Kligfield, R., Channel, J. E. T., Widespread remagnetization of Helvetic limestones, J. Geophys. Res., 1981, 86: 1888-1900.[16]Maher, B. A., Thompson, R., Zhou, L. P., Spatial and temporal reconstruction of changes in the Asian paleomonsoon: A new mineral magnetic approach, Earth Planet Sci. Lett., 1994, 125: 461-471.[17]Liu, X. M., Rolph, T., Bloemendal, J. et al., Quantitative estimates of paleoprecipitation at Xifeng in the Loess Plateau of China, Palaeogeogr. Palaeoclim. Palaeoecol., 1995, 113: 243-248.[18]Thompson, R., Maher, B. A., Age models, sediment fluxes and paleoclimatic reconstructions for the Chinese loess and paleosol sequences, Geophys. J. Int., 1995, 123: 611-622.[19]Liu, T. S., Guo, Z. T., Liu, J. Q. et al., Variations of eastern Asian monsoon over the last 140000 years, Bull. Soc. Geol. France, 1995, 166: 221-229.[20]Guo, Z. T., Liu, T. S., Guiot, J. et al., High frequency pulses of East Asian monsoon climate in the last two glaciations: link with the North Atlatic, Climate Dynamics, 1996, 12: 701-709.[21]Han, J. M., Lü, H. Y., Wu, N. Q. et al., The magnetic susceptibility of modern soils in China and its uses for paleocli-mate reconstruction, Studia Geoph et Geod., 1996, 40: 262-275.[22]Zhu, R. X., History of anisotropy of the magnetic susceptibility and its implications: Preliminary results along an E-W transect of the Chinese Loess Plateau, Geophys. Res. Abs., 2000, 2: 226.

  17. Unmixing hysteresis loops of the late Miocene–early Pleistocene loess-red clay sequence

    Science.gov (United States)

    Zhang, Rui; Necula, Cristian; Heslop, David; Nie, Junsheng

    2016-01-01

    Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals. PMID:27389499

  18. Unmixing hysteresis loops of the late Miocene-early Pleistocene loess-red clay sequence

    Science.gov (United States)

    Zhang, Rui; Necula, Cristian; Heslop, David; Nie, Junsheng

    2016-07-01

    Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals.

  19. Unmixing hysteresis loops of the late Miocene-early Pleistocene loess-red clay sequence.

    Science.gov (United States)

    Zhang, Rui; Necula, Cristian; Heslop, David; Nie, Junsheng

    2016-07-08

    Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals.

  20. MECHANISM OF LARGE-SCALE SLIDE AT EDGE OF LOESS PLATEAU ON NORTH OF WEIHE RIVER IN BAOJI URBAN AREA,SHAANXI PROVINCE%宝鸡渭河北岸黄土塬边大型滑坡成因机制研究

    Institute of Scientific and Technical Information of China (English)

    石菊松; 李滨; 吴树仁; 王涛; 辛鹏

    2013-01-01

    滑坡成因机制是深入认识、合理评价与有效防治滑坡的关键难点,其中黄土滑坡成因机制一直是中国工程地质界的研究热点问题之一。利用DEM,Quick bird影像与地面调查相结合完成了宝鸡市区渭河北岸黄土塬边大型滑坡详细编录与GIS制图,结合典型滑坡的钻探、物探成果,利用第四纪地质的最新成果,重建了渭河河谷构造地貌演化过程、查清了斜坡地层岩性组合、获得了新近系黏土地层工程地质特性参数和活动断裂的特征,初步建立了宝鸡渭河北岸黄土塬边大型黄土滑坡的概化模型。初步研究认为:(1)宝鸡渭河北岸在上新世-早更新世时期古地形由北向南渐低,古地貌由山前冲洪积平原向古三门湖变化,且古三门湖逐渐消亡,早更新世晚期现今渭河形成且主流总体向北偏移,直至全新世偏离北岸,形成现今地貌格局的地貌演化过程。(2)黄土塬边渭河北缘断裂为晚更新世以来的活动正断裂系,其不仅是地下水的导水通道,而且为滑坡后壁和次级滑面的形成提供了可追踪的软弱结构面。(3)渭河北岸黄土塬边古、老滑坡是在渭河侧蚀和地下水作用下,追踪断裂面沿新近系硬黏土界面或硬黏土层内部发生的地堑地垒式多级坡基旋转、坡体平移或复合型滑坡,是受新近系三趾马红土或三门系黏土地层和断裂控制的特殊类型黄土滑坡。%Landslide mechanism is the key of understanding,reasonable assessment,effective prevention and con-trol of landslides.It is quite difficult to achieve.Meanwhile,loess landslide mechanism has been one of the research hotspots in Chinese engineering geological circles over last decades.This study carries out detailed landslide survey and inventory combined with typical large scale slide drilling and geophysical exploration at the edge of loess plateau on north of Weihe river in

  1. Effects of Soil and Water Conservation of Algae Crust in Hilly and Gully Regions on Loess Plateau%黄土高原沟壑区藻类结皮的水土保持效应

    Institute of Scientific and Technical Information of China (English)

    康磊; 孙长忠; 殷丽; 汤志敏; 贺淑霞

    2012-01-01

    The effect of soil and water conservation of algae crust widespread in hilly and gully regions on Loess Plateau had been researched from two aspects which were rainfall infiltration-runoff and evaporation of soil water.The results were as follows: ①Algae crust could increase the 0-10 cm depth soil porosity.The maximum increase of total porosity was 7.4%,and the capillary was 14.2%.Algae crust had no significant effect on the soil porosity of the deeper layer.②In wasterland,mongolian scotch pine and Chinese pine forest,the runoff between the algae crust and non-crust had a significant difference.Compared with the runoff of non-crust,the runoff of algae crust in the three types of vegetation reduced by 28.1%~32.5%,34.4%~43.1% and 30.8%~31.6%.③In the three types vegetation,the amount of soil erosion between algae crust and non-crust had a significant difference.Compared with the amount of soil erosion of non-crust,the amount of soil erosion of algae crust in the three types of vegetation reduced by 58.8%~70.6%,48.9%~62.6% and 38.3%~57.1%.④By stepwise regression analysis,the different regression equations between runoff,soil erosion of algae crust and rainfall factor in different vegetation types could be obtained.⑤The soil moisture of 20-60 cm depth could be affect by algae crust.In this depth the soil moisture of algae crust was significantly higher than non-crust zone.%从降雨径流、水分蒸发两方面探讨黄土高原沟壑区藻类结皮的水土保持效应。结果表明:①藻类结皮可显著增加0-10cm土层内土壤孔隙度,最大增加幅度总孔隙度为7.4%,毛管孔隙度为14.2%;对更深土层的土壤孔隙度无显著影响。②荒草坡、樟子松林和油松林3种植被类型下,有藻类结皮试验区径流量与无结皮对照区有显著差异,径流量分别减少了28.1%~32.5%、34.4%~43.1%和30.8%~31.6%。③3种植被类型下,藻类结皮的土壤侵蚀量与无结皮对照土壤侵蚀量有

  2. 黄土高原沟壑区长武县2009年土地利用结构特征分析%Characteristics of land use structure in 2009 in Changwu County, the Loess Plateau gully region

    Institute of Scientific and Technical Information of China (English)

    张建军; 张晓萍; 陈凤娟; 马芹; 雷泳南; 万龙

    2011-01-01

    选取定量指标并结合GIS技术,基于土地利用结构内涵,对退耕还林背景下黄土高原沟壑区长武县2009年土地利用结构特征进行定量分析.研究表明:目前全县土地利用多样化指数较高,集中化指数则较低,组合类型和洛伦兹曲线体现了全县土地利用较丰富的组合特征,集约化水平较低,各乡(镇)土地利用程度不高.空间分析定量化阐明了各乡(镇)地类区位意义、县域地类斑块空间分布状态.结构分析体现了北部塬面沟坡,南部残塬沟壑2大分区的县域特色.全县土地利用总体特征为:以林地+耕地为景观基质,林地+耕地+园地+未利用地为组合类型,以农用地为主,土地利用程度较低.黄土高原沟壑区塬、坡、沟的地貌格局是土地利用空间格局的自然基础.人口密度与土地利用程度显著相关,居民工矿用地区位优势一定程度上体现了土地利用结构.黄土高原沟壑区土地利用没有直接反映经济水平,有待于进一步调整和优化土地利用现状.%Based on the understanding of connotation of land use structure, by using GIS technology the quantitative indices were selected to study the characteristics of land use structure in 2009 in Changwu County, Shaanxi Province, Loess Plateau gully area. The results showed that in Changwu County, the diversification indices of each town were relatively high, and centralization indices and land use degrees were generally low. The combination of land use types and Lorenz curve of each town showed that combination forms were abundant in the whole county at present. Spatial analysis expressed the location significance of each town and spatial distribution of landuse patches. Structure analysis could reflect the two distribution districts, slope in north and gully in south region. The main characteristics of land use structure in the county could be generalized as: landscape matrix constitute of, arable land and forest land

  3. The population dynamics of apple Lithocolletis ringoniella in Loess Plateau%黄土高原苹果金纹细蛾种群动态

    Institute of Scientific and Technical Information of China (English)

    李鑫; 马丽; 刘玉玉

    2011-01-01

    In order to fully understand the regular pattern of the population dynamics of Lithocolletis ringoniella Matsumura in the apple production region of the Loess Plateau, the distribution pattern and the ecological niche index were determined and the clustering analysis was conducted to describe the dynamic change of L. ringoniella population. The results showed that the leaf insect spot caused by L. ringoniella was visible in June; the number of the insect increased in July, with the damage symptom severe in August; and the quantity of the population number was in surge in September and October. The relative abundance of the temporal sequence was in a strong rising trend since August. Population distribution in the crown was uniform in early July and aggregative after that. The spatial distribution among the vertical positions of the tree crown showed significant difference, population number following the order of lower > middle > upper parts, whereas distribution among horizontal directions had no significant difference. The general distribution within the crown appeared in cluster, with individuals attractive to each other. The ecological niche occupation of this pest in vertical and horizontal directions as well as in temporal sequences are 0.179, 0.371 and 0.594, respectively. The resource utilization rate in the lower part of the crown reached 53.73% and almost nothing utilized in the upper part, indicating a more horizontal expansion potential. Viewing from the four directions, the maximum utilization of resources was in the north and east, up to 27. 90% and 21.66% respectively. The ecological niche overlap index of L. ringoniella with hawthorn spider mite in vertical and horizontal directions reached 92.65 and 64.95,respectively, in addition to temporal sequence to be 66. 36, indicating that hawthorn spider mite is the most intense space-temporal competitor for the limited resources of apple' s crown leaves. The dominance degree index of L. ringoniella in the

  4. The impact of cropland conversion on environmental effect in the Loess Plateau:a pilot study based on the national experimental bases%黄土高原退耕还林(草)及其综合效应研究--以黄土高原国家试验示范区典型小流域为例

    Institute of Scientific and Technical Information of China (English)

    王飞; 李锐; 焦峰

    2005-01-01

    Conversion of cropland to forestry and grassland is an important method to reduce soil erosion and improve the biophysical environment in the Loess Plateau. The feasibility, methods, and environmental effects of cropland conversion were studied based on 11 typical watersheds of national experimental bases instead of different geographic areas of the Loess Plateau. Between 1986 and 2000,cropland, sloping cropland and non-agricultural land decreased by 8%, 92.5% and 8% respectively,while forestry increased by 15.7%. The land use change not only decreased annual soil erosion by 74%, but also increased vegetation coverage by 100% and improved the soil condition and biodiversity. This can be achieved by building basic farmland, increasing capital and scientific input,and planting trees and grasses according to the natural biophysical restrictions.

  5. A sedimentological proxy indicator linking changes in loess and deserts in the Quaternary

    Institute of Scientific and Technical Information of China (English)

    丁仲礼; 孙继敏; 刘东生

    1999-01-01

    From Yulin, which is located in the transitional zone between the Loess Plateau and the Mu Us desert, to Weinan in the southernmost part of the Loess Plateau, 9 loess sections were studied. Grain size analyses show that the advance-retreat changes of the deserts in northern China may be the most important factor controlling changes in the sand particle percentage of the loess-soil sequences during the last glacial-interglacial period. It is thus suggested to use the sand grain content of loess deposits as a proxy indicator of desert variations. Applying this indicator to the last glacial loess deposits in the northwestern part of the Loess Plateau reveals that there were many millennial-scale cycles of the desert environments.

  6. Research of Causes and Control Patterns on Land Desertification in Loess Plateau%黄土高原土地沙漠化成因机制及其治理模式的研究

    Institute of Scientific and Technical Information of China (English)

    田红卫; 高照良

    2013-01-01

    土地沙漠化是一个渐进的过程,但其危害及其产生的灾害却是持久和深远的.它不仅对当代人产生影响,而且还将祸及子孙.据专家测算,中国每年因土地沙化造成的直接经济损失高达540亿元,直接或间接影响近4亿人口的生存、生产和生活.土地沙漠化不仅恶化生态环境,衰退土地生产力,威胁江河安全,而且加剧沙区贫困.本文以系统论和生态经济学为指导,在介绍了黄土高原土地沙漠化的基本概况、特征及危害的基础上,从地表沙源、气候、风沙灾害、水资源和土地利用、开发建设等方面,分析了黄土高原沙漠化的成因;结合黄土高原地区多年来沙漠化治理的经验,提出了生态建设治理、植物、工程、化学治理、沙产业主导、依托线状工程4种沙漠化治理模式.%Though the land desertification is a gradual process, but its hazards and disasters have lasting and far reaching. Not only did it have an impact on contemporary people, but also on penalise children. According to estimating of experts, the direct economic loss reaches to $7.87 billion every year as a result of land desertification. Also, the survival, production and daily life of nearly 400 million people are all affected by land desertification, directly or indirectly. Land desertification not only worsening the ecological environment, declining land productivity, threatening the safe of river, but also intensify poverty of the sandy areas. Using the system theory and ecological economics as a guide, on the basis of introducing a basic overview of the Loess Plateau land desertification, the characteristics as well as the harm of land desertification, analyzing the causes of Loess Plateau desertification though the following aspects, sources of surface sand, climates, disasters of wind and sand, water resources, land uses, developments and constructions, and combined control experience of Loess Plateau desertification over

  7. 黄土高原沟壑区苜蓿生产力及养分特性的研究%Alfalfa productivity and plateau characteristics in a gully region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    折凤霞; 郝明德; 臧逸飞

    2013-01-01

    在长期定位试验的基础上,研究了黄土高原沟壑区粮草轮作中苜蓿产草量及其养分变化特性.结果表明,苜蓿产草量一年生最低,为8 763 kg/hm2,3年生产草量达到最高,为12 020 kg/hm2,4年生产草量为9 665 kg/hm2,开始出现下降.1年生苜蓿对氮、磷、钾的吸收量最低,分别为218 kg/hm2,11 kg/hm2,105 kg/hm2,3年生苜蓿对磷、钾的吸收量最高,分别为23 kg/hm2和185 kg/hm2,比1年生苜蓿吸磷量高109.1%、吸钾量高76.2%;而4年生苜蓿对氮的吸收量最高,为351 kg/hm2,比1年生苜蓿吸氮高61%.土壤有机质、全氮和碱解氮含量逐年增加,有机质由15.60 g/kg增至18.26 g/kg,全氮由1.20 g/kg增至1.50 g/kg,碱解氮由64.74 mg/kg增至88.02mg/kg;土壤全磷、速效磷及速效钾含量逐年下降,全磷由0.86 g/kg降至0.76 g/kg,速效磷由14.00mg/kg降至9.27 mg/kg,速效钾由70.51 mg/kg降至54.35 mg/kg.建议在生产中施适量钾肥满足苜蓿高品质、高产量的需要.%Alfalfa (Medicago sativa) plant yield and nutrient change characteristics of forage crop rotation were studied in a long-term experiment in the gully region of the Loess Plateau. The one-year Medicago yield was 8 763 kg/ha (the lowest) and the three-year Medicago yield was 12 020 kg/ha (the highest) but the four-year yield fell to 9 665 kg/ha. The N, P, K uptake (218, 11, 105 kg/ha respectively) in one-year Medicago was the lowest. The P, K uptake of three-year Medicago was the highest (23 kg/ha and 185 kg/ha respectively) and compared with one-year Medicago, the P uptake was 109. 1% higher and the K uptake was 76, 2% higher. The N uptake of four-year Medicago was the highest, about 351 kg/ha, which was 61% higher than one-year Medicago. Soil organic matter, total nitrogen and alkali solution nitrogen content increased each year, organic matter increased form 15. 60 to 18. 26 g/kg, total nitrogen increased from 1, 20 to 1. 50 g/kg, and alkali solution nitrogen increased from 64

  8. 黄土丘陵沟壑区坡面尺度土壤水分空间变异及影响因子%Spatial patterns of soil moisture at transect scale in the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    姚雪玲; 傅伯杰; 吕一河

    2012-01-01

    Understanding the spatial variability and impact factors of soil moisture is important when modeling the antecedent soil moisture status of a catchment. Soil moisture is a limiting factor of ecosystem development in semi-arid and arid areas. Soil moisture spatial patterns and impact factors are particularly important for ecosystem restoration in the semi-arid areas of the Loess Plateau. This study identifies soil moisture spatial patterns and impact factors (terrain, land use types and wet season) in Yangjuangou catchment in north of the Loess Plateau from the measurement of soil moisture in the top 100 cm soil layer along five different transects on a loess hill before and after the wet season. Statistical analysis revealed that the soil moisture spatial variation in deeper soil ( > 40cm) was more significant than that in upper soil ( planted R. pseudoacacia forest land (8 years) > planted R. pseudoacacia forest land (20 years) > planted Hippophae reamnoides forest land, no matter before or after the wet season. Although the topography of planted forest land has advantageous conditions (shading slope, lower position, smaller gradient or terraces) for retaining soil moisture, the soil in planted land was still found to be have a much lower soil moisture content than the soil in natural grasslands, especially in deeper soil. Thus it is considered that the influence of terrain on soil moisture content is masked by the influence of surface vegetation. Therefore, when modeling hydrological processes in the Loess Plateau, it is recommended that the pattern of vegetation types within the simulated area should be paid special attention. Hydrologic models of the Loess Plateau based only on terrain properties should be used cautiously. The soil moisture content at all sample sites increased after the wet season, however, the spatial patterns of soil moisture was not significantly changed. Sites which had high soil moisture content relative to other sites before the wet

  9. Soil and Water Loss and Coping Mechanism on Loess Plateau in Qing Dynasty%清代黄土高原水土流失及社会应对机制

    Institute of Scientific and Technical Information of China (English)

    李荣华

    2015-01-01

    清代黄土高原水土流失极为严重,直接影响着黄河中下游地区人民的生产生活。面对此问题,中央政府及大部分地方政府没有形成系统、有效的治理机制,只是个别地方官带领民众进行植树造林。民间社会通过植树造林、梯田以及建设拦泥淤地工程、修建沟头防护工程等措施进行应对,他们所采取的许多方法不受官方重视,没有被总结、改良与推广。这一时期的应对机制不够健全,官方与民间社会互动不足,导致黄土高原水土流失问题无法得到有效治理。%Soil and water loss was serious on loess plateau in Qing dynasty and this brought enormous influenceto people's life in the middle and lower reaches of the Yellow River. Facing this problem, the central government and most of the local government did not form systematic and effective govern-ance mechanism and some individual local officials led peopleplant tree only. Folk society carried out coping-style that was tree planting, constructing terrace, and buildingconstruction for sediment retention and farmland-making, gully head protection. Many of these methods had not been paid attention and summarized, improved, extended by the official. Coping mechanisms was not enough healthiness in this time and interaction was not deficient in the official and folk society, these led soil and water loss on loess plateau effectivelycontrol.

  10. Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    Jian Shengqi

    2014-06-01

    Full Text Available In this paper, to evaluate the hydrological effects of Caragana korshinskii Kom., measured data were combined with model-simulated data to assess the C. korshinskii soil water content based on water balance equation. With measured and simulated canopy interception, plant transpiration and soil evaporation, soil water content was modeled with the water balance equation. The monthly variations in the modeled soil water content by measured and simulated components (canopy interception, plant transpiration, soil evaporation were then compared with in situ measured soil water content. Our results shows that the modeled monthly water loss (canopy interception + soil evaporation + plant transpiration by measured and simulated components ranges from 43.78 mm to 113.95 mm and from 47.76 mm to 125.63 mm, respectively, while the monthly input of water (precipitation ranges from 27.30 mm to 108.30 mm. The relative error between soil water content modeled by measured and simulated components was 6.41%. To sum up, the net change in soil water (ΔSW is negative in every month of the growing season. The soil moisture is approaching to wilting coefficient at the end of the growth season, and the soil moisture recovered during the following season.

  11. 黄土丘陵区不同造林模式的土壤效应研究%Soil Effects of Different Afforestation Model in Hilly Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李金花

    2012-01-01

    分析青海黄土丘陵区相同林龄(8年)的5种造林模式土壤的有机质含量、总孔隙度和微生物总量大小,结果为云杉桦树混交〉桦树〉云杉沙棘混交〉云杉〉沙棘〉农田;各造林模式缓解日温变化效应的大小顺序为云杉桦树混交〉桦树〉云杉沙棘混交〉沙棘〉云杉〉农田。%The effects of soil from different afforestation models in hilly loess plateau were analyzed. The results were as follows: mixture of picea crassifolia and birch 〉birch 〉mixture of picea crassifolia and hippophae rhamnoides 〉picea crassifolia 〉hippophae rhamnoides〉farmland. The order of easing temperature changes was as follows: mixture of picea crassifo|ia and birch 〉birch 〉mixture of picea crassifoIia and hippophae rhamnoides ~hippophae rhamnoides 〉picea crassifo|ia 〉 farmland.

  12. Normative Research of Pollination by Osmia Cornifrons on Apple in the Weibei-loess Plateau%渭北高原区苹果壁蜂授粉技术的规范研究

    Institute of Scientific and Technical Information of China (English)

    马志峰; 郭民主; 王荣花; 王智民

    2012-01-01

    In order to standard the pollination technology by Osmia comifivns of orchardist which lived in the Weibei-loess plateau, the effect of Osmia out of cocoon by the different styles, the place of nest boxes and the tube of nest on leaving the cocoon was studied by comparison method. The results showed that stripping the cocoon method was the best way, which had the highest ratio of breaking through and nidification. The height of nest boxes should be 20 cm above ground. The nest ratio of bulrush and paper were higher than that of plastic tube.%为了规范渭北高原苹果产区应用壁蜂授粉技术.通过田间试验研究了壁蜂不同释放方法、巢箱高度、巢材管对壁蜂出茧速度、出茧率、营巢管率等的影响.结果表明:剥茧放蜂法出茧速度最快、出茧率和营巢管率最高.巢箱距地面20cm左右营巢管率最高.纸巢管和芦苇巢管的营巢管率显著高于塑料巢管.

  13. Responses of soil enzyme activities to re-vegetation in gully Loess Plateau of Northwest China%黄土高原沟壑区土壤酶活性对植被恢复的响应

    Institute of Scientific and Technical Information of China (English)

    李林海; 邱莉萍; 梦梦

    2012-01-01

    结合野外调查与室内分析,研究了黄土高原沟壑区小流域自然坡面和不同植被恢复条件下剖面土壤酶活性的分布特征,以及土壤酶活性对植被恢复的响应.结果表明:黄土高原沟壑区小流域坡地土壤的脲酶、蔗糖酶和碱性磷酸酶活性为高度变异指标,过氧化氢酶活性则为弱变异指标.土壤剖面酶活性受植被恢复措施的显著影响,随土层的加深,土壤脲酶、蔗糖酶和碱性磷酸酶活性逐渐降低,过氧化氢酶活性升高.3种水解酶活性之间呈显著正相关,并与土壤物理性质显著负相关,与土壤化学性质显著正相关;过氧化氢酶活性除与含水量和pH正相关外,与其他理化性质呈负相关.土壤水解酶类可以敏感指示植被恢复的土壤效应,植被恢复措施可以改善表层和深层土壤的生物学性质.%In combining field investigation with laboratory analysis, this paper studied the distribution characteristics of soil enzyme activities along the soil profiles and natural slopes with different re-vegetation treatments in gully Loess Plateau, aimed to assess the responses of the soil enzyme activities to re-vegetation. In the study area, the activities of soil urease, invertase and alkaline phos-phatase along natural slopes were highly varied, but the activity of soil catalase was in adverse. The profile distribution of the soil enzyme activities varied significantly with vegetation type, and with increasing soil depth, the activities of soil urease, invertase and alkaline phosphatase decreased while the catalase activity increased. There existed significant positive correlation among the three hydro-lases activities. The activities of the three hydrolases were all significantly negatively correlated with soil physical properties and positively correlated with soil chemical properties, while the soil catalase activity was positively correlated with soil moisture content and pH and negatively correlated

  14. The Spatial Discrepancy Records of Matuyama-Gauss Polarity Reversal in Chinese Loess%中国黄土中松山-高斯极性倒转事件记录的空间对比

    Institute of Scientific and Technical Information of China (English)

    谢兴俊; 周卫健; 鲜锋; 武振坤

    2014-01-01

    前人古地磁学研究表明,中国黄土不同剖面中松山-高斯(M/G)地磁极性转换界线记录层位并不一致,有的记录在黄土中,有的记录在红粘土中,这种不一致现象将可能影响到基于古地磁的黄土年代框架的建立及与全球气候记录的准确对比。针对这一问题,选取目前已有的典型黄土剖面中M/G地磁极性转换研究的结果进行了对比分析,并尝试采用磁化率-深度曲线的空间对比来检验不同剖面M/G界线层位记录的差异,结果表明中国黄土中M/G界线均记录在由磁化率-深度曲线所反映的“黄土L33层”,说明黄土中M/G界线层位记录不一致的现象可能主要是由于地层划分方案的差异所致。根据这一思想,论文尝试对传统的洛川、西峰黄土地层划分方案进行部分修订,并简要介绍了M/G界线记录的海陆对比差异和未来利用宇宙成因核素10 Be 示踪M/G极性倒转事件过程的可能性,以期为研究黄土中地磁极性转换过程和确切层位提供一种新方法。%Previous paleomagnetic studies have shown that the records of Matuyama-Gauss (M/G)re-versal event in Chinese loess are asynchronous,some located in loess,while the others located in red clay.This phenomenon will partially lead to the uncertainties in reconstructing the chronology of loess and correlating loess climatic proxies with marine sediments.To clarify our knowledge on the M/G reversal in loess,some representative section studies on the M/G reversal are carefully analyzed in this paper,using the magnetic susceptibility-depth curve to synthesize the different sections.Comprehensive results show that M/G reversal is generally recorded in loess L33 layer,suggesting that the asynchronous feature of M/G reversal record in loess is possibly attributed to the different loess stratigraphic division schemes.Ac-cording to this idea,the stratigraphic classification scheme of the classic

  15. 长期施用氮肥和磷肥对渭北旱塬土壤中氨氧化古菌多样性的影响%Effects of Long-term Nitrogen and Phosphate Fertilization on Diversity of Ammonia-Oxidizing Archaea in Dry Highland Soil of Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    武传东; 闫倩; 辛亮; 王保莉; 曲东

    2012-01-01

    Ammonia-oxidizing archaea are likely the most abundant ammonia-oxidizing microbes in natural environment and they also play an important role in nitrification. In order to improve nitrogen use efficiency and explicate the indicating function of ammonia-oxidizing ar-chaea( AOA) on changes of soil quality in the Loess Plateau, AOA community structure diversity was studied. The soil samples used in this research derived from Changwu Agro-ecological Experimental Station on the Loess Plateau, Chinese Academy of Sciences, which had received 23 years continuous fertilization treatments, include CK (control, without fertilizers), LD (unplanted, without fertilizers), N(nitrogen input), P(phosphorus input) and NP(combination of nitrogen and phosphorus fertilizers). The soil AOA community structure diversity was analyzed by restriction fragment length polymorphism(PCR-RFLP) and DNA sequence. Positive clones collected randomly from clone libraries were digested by Rsa I and Msp I, respectively. According to the statistics of diversity index, there were 25, 18, 29, 20 and 30 restriction endonuclease types(OTUs), respectively. The a diversity indices indicated that there was a pronounced difference among five fertilizer treatments. The OTUs were the highest in both P treatment and CK treatment, while the lowest in NP treatment. The rescaled distance matrix tree indicated that the different fertilization had weak convergence of AOA community types with the CK treatment soil. Phylogenetic tree of amoA gene amino acid sequences analysis showed all AOA sequences fell within cluster S and cluster M, but the proportions were different. These results indicated that long-term fertilization resulted in change of AOA community diversity; however, different fertilizer alkaline soil had no significant impact on the species composition of dominant AOA.%采用基于氨单加氧酶基因的PCR-RFLP和DNA测序技术,以黄土高原旱地黑垆土为材料,研究长期施用氮肥和磷肥对

  16. 黄土高原不同侵蚀类型区侵蚀产沙强度变化及其治理目标%Variation of Sediment Yield in Different Soil Erosion Areas and Its Control Standards on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    王万忠; 焦菊英; 马丽梅; 穆兴民; 王万忠; 焦菊英

    2012-01-01

    Based on the distribution of hydrological stations,the study area was divided into 98 sections controlled by hydrological stations and then,234 soil erosion units were determined according to the different soil erosion areas.The variation of sediment yield,sediment reduction rate,and the area variation and spatial distribution were analyzed for different degrees of sediment yield in the different soil erosion areas in different control periods.The control standards for the different soil erosion areas on the Loess Plateau in the future 20 years were put forwarded: Soil loss is controlled at 3.6×108 t and soil erosion modulus is less than 1 300 t/(km2·a).For the different soil erosion areas,soil erosion modulus is 3 000 t/(km2·a) in loess Mao hilly and gully region,2 000 t/(km2·a) in loess Liang hilly and gully region,2 000 t/(km2·a) in arid loess hilly and gully region,1 000 t/(km2·a) in loess gentle slope hilly and gully region,1 000 t/(km2·a) in wind and sand loess hilly and gully region,1 000 t/(km2·a) in loess piedmont hilly and gully region,300 t/(km2·a) in forest loess hilly and gully region,1 500 t/(km2·a) in loess tableland hilly and gully region,3 000 t/(km2·a) in loess residual plateau hilly and gully region,500 t/(km2·a) in loess terraces region,500 t/(km2·a) in wind and sand grassland region,and 100 t/(km2·a) in plateau mountain and rock region.The key control areas in the future 20 years are loess Mao hilly and gully region(2.20×104 km2),arid loess hilly and gully region(1.50×104 km2),loess tableland hilly and gully region(8 600 km2),and loess Liang hilly and gully region(4 600 km2).%为了确定黄土高原不同侵蚀类型区的治理目标,采取"水文—地貌法",利用98个水文站控制区和234个侵蚀产沙单元,在分析其不同治理阶段土壤侵蚀产沙变化特征与减沙幅度,不同侵蚀强度面积的变化及其空间分布的基础上,提出了未来20a黄土高原主要流失区的区域治理目

  17. Trait Variations along a Climatic Gradient in Hilly Area of Loess Plateau%黄土丘陵区植物功能性状沿气候梯度的变化规律

    Institute of Scientific and Technical Information of China (English)

    施宇; 温仲明; 龚时慧; 宋光; 郑颖; 丁曼

    2012-01-01

    More than 147 plant species in Yanhe River catchment in hilly area of Loess Plateau were selected and leaf area(LA),leaf length/leaf width(LW),leaf thickness(LT),leaf dry mass(DM),specific leaf area(SLA),leaf tissue density(LTD),leaf nitrogen concentration(LNC),specific root length(SRL),root tissue density(RTD) and root nitrogen concentration(RNC)) of 10 plant traits were determinated.Correlation analyses were used for quantifying relationships between plant traits and site climate.The results showed that:(1) functional traits of all species changed with environmental factors,and preciatation rather than temperature is the main control of trait differences along the gradient.As temperature index increased,LNC becomed higher;(2) large trait differences existed in growth forms.Grasses had higher mean LA,SLA,LNC,RNC,SRL and lower LTD than woody species,reflecting the adaptive differences of growth forms to environment;(3) trait variations of growth forms along a climatic gradient demonstrated an overall adaptation to environment,which were the combination strategies of co-evolution and divergent.The results of this research will provide basis for knowing adaptive mechanisms of plants to environment in hilly area of Loess Plateau.%选取黄土丘陵区延河流域147个物种,对10个与植物形态、生理相关的叶片和细根功能性状(叶大小、叶长宽比、叶厚度、叶干重、比叶面积、叶组织密度、叶氮含量、细根比根长、细根组织密度和细根氮含量)进行了测定,并对功能性状与气候因子的关系进行了分析。结果表明:(1)水热条件是影响研究区植物功能性状的重要因子,其中降雨为主导因子。物种水平上,植物功能性状随着环境的变化而变化,如叶氮含量随着温度指标(最冷月均温、生长季均温、年均温、最热月均温、温度季节变化的增加而增加;(2)不同生长型功

  18. 黄土高原丘陵沟壑区包气带土壤水运移过程%Migration process of soil water in the unsaturated zone of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    杨永刚; 李国琴; 焦文涛; 黄磊

    2016-01-01

    包气带土壤水运移过程是黄土高原生态修复中亟需回答的关键科学问题。环境同位素方法可获取其他方法难以获取的水文过程信息。通过对黄土高原丘陵沟壑区羊圈沟小流域降水、包气带0~150 cm土壤水和绣线菊( Spi⁃raea salicifolia)木质部水等样品的同位素δD和δ18 O进行测定。结果表明:羊圈沟小流域降水同位素组成受蒸发作用影响较大,呈现明显分馏效应。包气带土壤水、降水与木质部水同位素组成存在明显月份变化特征。降水是土壤水的主要补给来源,灌丛的水分利用来源主要为降水和土壤水,符合降水⁃土壤水⁃植被水的运移特征。灌丛木质部水和20~40 cm土壤水δD和δ18 O最为接近,20~40 cm土壤水是灌丛水分利用的主要来源。研究揭示了包气带土壤水运移过程及植物水分利用来源,为土壤水运移过程、模型结构与参数识别等提供科学依据。%The mechanism of soil water migration in the reconstruction and restoration of the Loess Plateau is a key scientific problem that must be solved. Isotopic tracers can provide valuable information associated with complex hydro⁃logical problems and are difficult to obtain by other methods. This study investigated soil water migration in the unsatu⁃rated zone in the hilly and gully region of the Loess Plateau. Samples were collected from the 0—150 cm unsaturated zone, including precipitation, soil water content, plant xylems, and plant roots, and were analysed. The results showed that the isotopic composition of precipitation in the Yangjuangou River basin was affected by evaporation, as indicated by isotopic fractionation phenomena. The δD and δ18 O isotopic profiles of the soil water exhibited monthly variations. The soil water was recharged by precipitation. The soil water and precipitation were taken up by shrubland. Water migration exhibited a transformation pathway from

  19. 黄土高原水平梯田现状及减沙作用分析%The Status and Sediment Reduction Effects of Level Terrace in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    马红斌; 李晶晶; 何兴照; 刘晓燕; 王富贵

    2015-01-01

    Level terrace is one of the most important measures of developing soil and water conservation and efficient agriculture in the Loess Plateau,which has the dual role of agriculture efficiency and ecological restoration. This paper analyzed the level terrace status:including scale,distribution,quality,planting structure and sediment reduction effects,based on remote sensing image of the ZY-3 Satellite and field survey. The results show that there have level terrace 3. 71 million hm2 by the end of 2012,mainly distributed in the Yellow River basin in Gansu Province and adjacent areas and Hekouzhen-Longmen reaches of the Yellow River in Shanxi Province,where the terraced area ac-counts for around 54. 3% of the total terrace area in the Loess Plateau;Level terrace in Weihe River,Jinghe River and Zulihe River has a high quality rank and is dominated by farming,however,there have mainly narrow terraces with width 4-6 m in He-Long reaches,and"Terrace for Farmland" is commonly appearing. In the future,terrace construction in the Yellow River of Gansu Province should give priority to damaged terrace reconstruction,the development space maybe 5% ~15%,however,He-Long reaches has a higher development poten-tial,expect to increase new terrace by as much as 25%. Based on the terrace sediment reduction calculation method,the existing level ter-races in the area upstream Tongguan can reduce sediment about 500 million tons.%水平梯田是黄土高原地区发展水土保持高效农业的重要措施之一,具有农业增效、生态修复的双重功能。基于资源三号卫星遥感影像和实地调查数据,分析了2012年黄土高原地区梯田现状:规模、分布、质量、利用方式及其减沙作用。结果表明:截至2012年底,黄土高原地区现有水平梯田371.29万hm2,主要分布在甘肃省黄河流域及其邻近地区、山西省河龙间支流流域,这些区域水平梯田面积占黄土高原梯田总面积的54.3%;渭河、

  20. 黄土高原汾河流域地表景观演变特征研究%Study on the Surface Landscape Changes in Fenhe River Basin of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    侯志华; 马义娟

    2013-01-01

    黄土高原是中国高度脆弱的生态系统之一,基于2000年和2008年两期TM遥感影像,以黄土高原脆弱区独立的流域单元——汾河流域为例,综合运用GIS和RS技术及景观生态学的基本原理与方法,分析该流域地表景观特征及其变化趋势,同时利用DEM数据,探讨景观演变的空间分异规律,为进一步研究流域景观演变驱动机制提供有价值的信息.结果表明:(1)农田、森林、草地始终是该流域的主要景观构成,但绝对优势景观(农田)所占比例大幅下降;(2)就整体景观尺度而言,形状趋于规则,连通性增强,多样性增大,蔓延度下降,整体景观格局受人为活动的干扰越来越强;(3)流失的农田主要流向了草地、森林和聚落,成为该流域8 a来主要的景观演变类型;(4)农田向聚落景观的演变主要发生在地势平坦、海拔低的中部两大盆地地区,农田向林草景观的演变则主要发生在海拔较高、坡度较大的上游、中游南部以及中下游外围的山地丘陵区.%The Loess Plateau is one of the most ecologically fragile regions in China. A case study was conducted in an independent basin unit in the eco-fragile region of the Fenhe River basin on the Loess Plateau based on Landsat-TM image respectively made in 2000 and 2008 and integrated by the means of the technology of RS and GIS as well as the theory of landscape ecology, the change tendency of landscape pattern was analyzed, and digital elevation model (DEM) was used to discuss the spatial distribution of the major landscape change types to provided valuable information for studying the driving force of the landscape changes. The results showed; (1) farmland, forest and grass were the main landscape types all along. Moreover, although the farmland element had the absolute superiority over the other two, it sharply decreased during the study period; (2) by analyzing the landscape pattern of the whole area, we found that the

  1. 黄土高原坡面刺槐林土壤水分生态位特征分析%Characters of soil moisture niche-fitness of locust forest in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    孟秦倩; 蔡焕杰; 王健; 张青峰

    2009-01-01

    通过定位观测并引入土壤水分生态位适宜度,以刺槐林根系分布作为土壤水分生态位权重,对黄土高原刺槐林不同地理位置、不同坡向和不同时期土壤水分生态位进行了分析.结果表明:由南向北,土壤水分生态位递减,淳化刺槐林土壤水分生态位为97.5%,可满足刺槐生长,米脂刺槐林土壤水分生态位为53.2%,林木生长较大受水分的限制;在不同坡向间刺槐林土壤水分生态位表现为阴坡最高,阳坡最低,在生长季节,刺槐的生长受土壤水分的制约,半阴坡和半阳坡介于二者之间;在年内,春旱及春末旱,导致土壤储水量减少,7月初土壤水分生态位降到最低.随着林龄和林木密度的增加,土壤水分生态位降低,保持适当的林分密度,可实现林木的正常生长.%The soil moisture of locust forest at different period and slope aspect from different geographic locations in the Loess Plateau is analyzed with the help of the model of the moisture niche-fitness. The results show that the value of the soil moisture niche-fitness of locust forest declines gradually from the South(Chunhua County, 97.5%) to the North (Mizhi County, 53.2%) of the Loess Plateau. The growth of the locust forest is affected more by the soil moisture factor. The highest value of the moisture niche-fitness is in the north-slope, while the lowest is in the south-slope. During the growth period in a year, the drought in spring can reduce the soil moisture capacity, and it can even cause the lowest soil moisture niche-fitness at the beginning of July. Along with the increase of the age and thickness of stand, the soil moisture niche-fitness is in a downward trend. So the suitable density of stand can promote the growth of the forest.

  2. Applicable evaluation of crop model AquaCrop for summer maize production in Loess Plateau Region%AquaCrop作物模型在黄土塬区夏玉米生产中的适用性评价

    Institute of Scientific and Technical Information of China (English)

    倪玲; 冯浩; 任小川; 郝志鹏

    2015-01-01

    In order to evaluate its applicability of crop model AquaCrop in Loess Plateau Region,the model parame-ters were revised and validated based on the summer maize parameters recommended by Hsiao et al .The biomass in the maize growing season,the change procedure of evapotranspiration,harvest yield and aboveground biomass in 2003, 2004,2005,2007,2008 and 2010 in Changwu Region of the Shaanxi Province have been simulated,and carried out the comparison and analysis for the simulated with measured data .The results were showed that:In the six years,the adjust-ed determination coefficient Adj .R2 for simulated yield data and measured yield data was 0 .9270,the relative error was between -2 .479 to 1 1 .182 .The Adj .R2 for simulated and measured aboveground biomass was 0 .7842 .In this model, the effect of simulating yield was better than the aboveground biomass .In 2005 and 2008,the Adj .R2 for simulated and measured evapotranspiration were 0 .6229 and 0 .7973,respectively .Therefore,this model has a good simulation effect and important significance for the next optimal water management of summer maize in Loess Plateau Region .%为评价AquaCrop作物模型在黄土塬区的适用性,基于Hsiao等人推荐的玉米参数对模型参数进行调试及验证。在陕西长武地区模拟2003、2004、2005、2007、2008、2010年玉米生育期内生物量、蒸发蒸腾量的变化过程及收获时产量、地上部生物量,将模拟值与收集到的实测值进行对比、分析。结果表明,这6年模拟产量与实测产量间的校正决定系数(Adj)R2为0.9270,相对误差在-2.479至11.182之间;模拟地上部生物量与实测地上部生物量间的Adj .R2为0.7842,模型对产量的模拟效果优于对生物量的模拟;2005年和2008年模拟蒸散量与实测蒸散量间的Adj .R2分别为0.6229和0.7973。模拟效果较好,对黄土塬区夏玉米水分优化管理模拟有重要意义。

  3. Topographic differentiation simulation of crop yield and soil and water loss on the Loess Plateau%黄土高原作物产量及水土流失地形分异模拟

    Institute of Scientific and Technical Information of China (English)

    徐勇; 杨波; 刘国彬; 刘普灵

    2009-01-01

    De-farming slope farmland has been an effective measure in recent years for the improvement of the eco-environment and the mitigation of soil and water loss on the Loess Plateau. This paper, taking the Yangou Basin as a case study and using day-by-day mete- orological data of Yan'an station in 2005, simulated and analyzed the quantitative relation between crop yield, soil and water loss and topographic condition with the aid of WIN-YIELD software. Results show that: 1) topographic gradient has important influence on crop yield. The bigger gradient is, the lower the crop yield. Yields of sorghum and corn decrease by 15.44% and 14.32% respectively at 25° in comparison to the case of 0°. In addition, yields of soya, bean and potato decrease slightly by 5.26%, 4.67% and 3.84%, respectively. The in- fluences of topographic height and slope aspect on crop yield are slight. 2) Under the same topographic condition, different crops' runoff and soil loss show obvious disparity. Topographic gradient has important influence on soil and water loss. In general, the changing trend is that the soil and water loss aggregates with the increase of gradient, and the maximal amount occurs around 20°. The influence of topographic height is slight. Topographic aspect has a certain effect, and the fundamental characteristic is that values are higher at the aspect of south than north. 3) Topographic gradients of 5° and 15° are two important thresholds. The characteristic about soil and water loss with the variation of topographic gradients show that: the slope farmland with gradient less than 5° could remain unchanged, and the slope farm- land more than 15° should be de-farmed as early as possible.

  4. 甘肃黄土高原水热气候异常阶段特征%Analysis of Abnormality of Water and Heat Resources in Gansu Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    郭林; 张凯; 王毅荣; 雷俊

    2013-01-01

    利用1960~ 2004年相关地面实测气象资料,分析甘肃黄土高原地区水热气候异常变化的阶段性特征.结果表明,该地区地表变暖最为突出,夏半年增幅明显大于冬半年,地温随深度加深增温幅度越大;降水日数减少,连阴雨天气时段缩短、过程雨量减少,无雨时段增长,日照出现2次突变、呈现下降趋势;降水日数在1991年后突变减少,最长连续降水日数及过程降水量在1978年后突变减少.%Based on surface meterological data from 34 weather stations in Gansu during 1960-2004,the abnormal variation of water and heat resources on the Gansu loess plateau was analyzed by using weighted average,wavelet analysis and EOF (empirical orthogonal function).Results show that the ground temperature increased obviously after 1983,the increasing amplitude in summer was more than that in winter,and the increasing amplitude of groud temperature was bigger with depth deepening.The rainfall days decreased obviously after 1991,the length of successive raining days shorteued and no rain days extended,the longest continuous rainfall days and procession precipitation decreased after 1978.The sunshine hours also presented decreasing trend.

  5. Characteristics of Land Use and Land Cover Change in the Loess Plateau over the Past 20 Years%近20年黄土高原土地利用/覆被变化特征分析

    Institute of Scientific and Technical Information of China (English)

    周书贵; 邵全琴; 曹巍

    2016-01-01

    本文根据黄土高原地区20世纪80年代末、2000年、2008年3期土地利用/覆被空间数据集,计算2个时段(20世纪80年代末-2000年,2000-2008年)土地利用/覆被转类方向及其幅度、土地利用/覆被转类指数、土地利用/覆被状况指数及其变化率,分析黄土高原地区自20世纪80年代末以来土地利用/覆被时空变化特征以及宏观生态状况的变化趋势。结果显示:黄土高原地区近20年来平均土地利用/覆被状况指数为24.07,其中土石山区生态系统综合功能最好,其次为河谷平原区,最差的为农灌区。20世纪80年代末-2000年,黄土高原地区主要土地利用/覆被转类是森林和草地转为耕地,生态级别由高级向低级转移,2000-2008年主要土地利用/覆被转类是耕地转为林地和草地,低覆盖草地转为中高覆盖草地,生态级别由低级向高级转移。近20年来黄土高原地区地覆被状况指数变化以及土地利用/覆被转类指数表明,该区域的宏观生态状况总体上经历了转差(20世纪80年代末-2000年土地利用/覆被转类指数为-1.08),后转好(2000-2008年土地利用/覆被转类指数为2.66)2个过程。这一变化过程前期受区域气候变化以及人口增长共同驱动,后期则叠加了生态工程的影响。%Based on the three phases of land use and land cover change spatial data sets for the late 1980s, 2000 and 2008 in the Loess Plateau, we calculated the direction and amplitude of land cover change, land cover condition index and land cover change index, and analyzed the temporal and spatial characteristics of land cover and macro-ecological conditions changes in the Loess Plateau since the late 1980s. The results showed that the average land cover condition index of the Loess Plateau was 24.07 in the last 20 years. Land cover condition of the Rocky Mountain Area was the best, the Valley plain area took the second place, and

  6. A study of the parameterization of land-surface processes over the natural vegetation surface of Loess Plateau%黄土高原自然植被下垫面陆面过程参数研究

    Institute of Scientific and Technical Information of China (English)

    李宏宇; 张强; 史晋森; 赵建华; 王胜

    2012-01-01

    Based on the data observed at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) , the physical parameters related to land-surface processes over the natural vegetation surface of Loess Plateau are calculated. The paper studied averaged diurnal variations and the frequency distributions of the bulk transfer coefficients in the different seasons, and analyzed the trend of the surface roughness as well as effects of precipitation on the roughness. Monthly averages of the roughness in a normal year of precipitation have more changes compared with those in a dryer year since precipitation increasing tends to increase the roughness. The roughness in a normal year is 9 ×10-3m, while the roughness in a dryer year decreases to 6×l0-3m. The rainfall raises the roughness by increasing the vegetation cover and height. Relationships a-mong the bulk transfer coefficients and the two factors including surface roughness and the Richardson number are discussed. The role of dynamical transfer in land-atmosphere energy exchange over the Loess Plateau is dominant. Additionally, the neutral bulk transfer coefficient for momentum is close to that over the movable dune at Naiman in Inner Mongolia and the neutral bulk transfer coefficient for sensible heat is close to that over Gobi. We also analyzed effects of solar elevation angle and soil moisture on surface albedo and preliminarily a multiple factorial parameterization formula of surface albedo is suggested. Generally, the albedo over the Loess Plateau is smaller than that over the desert of Dunhuang and larger than that over pine forests in Changbai Mountain. The various vegetation covers and soil types in the three regions lead to differences of albedo. By testing the simulation results of the albedo formula, it is found that the albedo with low solar elevation angles is sensitive to the other factors except soil moisture and solar elevation angle, while soil moisture and solar elevation angle affect

  7. Concurrent and opposed environmental trends during the last glacial cycle between the Carpathian Basin and the Black Sea coast: evidence from high resolution enviromagnetic loess records

    Science.gov (United States)

    Hambach, Ulrich; Zeeden, Christian; Veres, Daniel; Obreht, Igor; Bösken, Janina; Marković, Slobodan B.; Eckmeier, Eileen; Fischer, Peter; Lehmkuhl, Frank

    2015-04-01

    Danube Basin near to the Black Sea (Urluia quarry, Dobrogea, Romania). In order to investigate the potential of Danubian loess in recording millennial-scale palaeoclimate variability, a 22 m deep drill-core from the Titel loess plateau and a more than 15 metres thick LPSS from the Urluia quarry were contiguously sampled. Both sides provide improved insight into past climate evolution of the regions down to MIS 6. The presentation will focus on the down-core/down-section variability of χ and χfd as environmental proxy parameters. Based on these mineral magnetic proxies we can already draw the following conclusions: 1) The dust accumulation rates in both regions were relatively constant over the past c. 130 kyrs, even during full interglacial conditions. 2) In the studied sections, the pedo-complex S1 represents ± the Eemian and not the entire MIS 5, as previously assumed. 3) There are a lot of similarities between the mineral magnetic records of the Titel-Plateau (Vojvodina, South Carpathian Basin) and the Urluia quarry (Dobrogea, Lower Danube Basin) and also between these records and those from the Chinese Loess Plateau, but also fundamental differences. 4) During the early glacial (end of MIS5) we find no evidence for soil formation in the South Carpathian Basin whereas in the Dobrogea near to the Black Sea coast embryonic soils developed. On the contrary, during the younger part of MIS 3 (≤ 40 ka) near to the Black Sea coast soil humidity sharply decreased towards the LGM whereas in the South Carpathian Basin the mineral magnetic proxies indicate a relative maximum in pedogenesis/soil humidity. Sedimentological, geochemical, geochronological and palaeomagnetic investigations are in progress. They will provide further high quality data sets leading to an improved understanding of the Late Pleistocene environmental evolution in the Danube Basin.

  8. Characterization of Argentine Loess and Paleosols by Moessbauer Spectroscopy

    International Nuclear Information System (INIS)

    We have used Moessbauer spectroscopy to investigate iron-bearing mineral samples of loess and paleosols from a geologic section at La Plata, Argentina, 34 deg. 54' 14'' S and 58 deg. 2' W. Hematite is by far the dominant iron-bearing magnetic component in initial loess and paleosol samples. The samples were also subjected to magnetic separation. The magnetically enriched loess fractions show a remarkable increase in the content of magnetite. The enhancement of non-magnetic Fe3+ and a decrease of Fe2+ mineral phases in the paleosol layer seem to be a consequence of the process of pedogenesis which also caused a dissolution of magnetic iron oxides by weathering. The increase of magnetite in the silt fraction suggests that the wind could have been the main carrier of magnetic minerals, causing the major differences in the magnetic parameters between loess and paleosols in the Argentine loess plateau

  9. Loess Hills of Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This coverage outlines the boundary of the Loess Hills in Iowa at 1:100,000 scale. Criteria applied to the delineation of the Loess Hills included drainage density,...

  10. Evaluation on ecotourism suitability in frangile environment of loess plateau based on RS and GIS-exampled on Zhongyang county, Shanxi province%基于RS、GIS的黄土高原环境脆弱区生态旅游适宜度评价——以山西省中阳县为例

    Institute of Scientific and Technical Information of China (English)

    李会琴; 侯林春; 肖拥军; 薛重生

    2009-01-01

    Evaluation on ecotourism suitability is a key to tourism exploitation in loess plateau with fragile environment, which can provide references for ecotourism planning, choosing places, products programming. Consequently, it can reduce the bad impacts on environment effectively. According to the characteristic of ecotourism resources in loess plateau, this paper built some evaluation indexes and model of ecotourism suitability. By RS image, the author picked up indexes information, such as terrain, vegetation and loess physiognomy. Using spatial and buffer analysis methods of GIS, this paper realized quantative evaluation and spatial continuity of ecotourism suitability. Thereby, the author put forward a method in ecotourism suitability evaluation in loess plateau. Finally, taking Zhongyang county in Shanxi province as a case study, they analyzed ecotourism suitability in this county and educed the optimum area, preferable area, medium area and inferior area of ecotourism. Furthermore, the paper brought forward the plans on ecotourism and some problems should be noticed.%生态旅游适宜度评价为黄土高原环境脆弱区旅游开发提供产品开发、项目选址、旅游分区等方面的决策依据,从而有效降低旅游活动对环境的影响.根据黄土高原区域特征及生态旅游资源的特点,论文构建了黄土高原生态旅游适宜度评价因子和模型.并基于RS、GIS空间信息技术,实现了地形、植被、黄土地貌等6个评价因子的信息采集与评价结果的空间显示,提出了黄土高原生态旅游适宜度评价方法.以山西省中阳县为例进行了实证研究,得到了南川河河谷为该县生态旅游最适宜区、吴家峁黄土地貌等为中适宜区以及一般适宜区和不适宜区.根据评价结果,论文最后提出了该县生态旅游的开发方向及应注意的问题.

  11. Study on the characteristics of soil moisture and water potential at the vadose zone in the Loess Plateau of East Gansu%陇东黄土塬区土壤包气带水分水势特征研究

    Institute of Scientific and Technical Information of China (English)

    王云权; 周向阳; 马金珠

    2011-01-01

    选取陇东黄土包气带为研究对象,综合运用数理统计与对比分析相结合的方法,研究黄土地区包气带土壤水分、水势变化特征和土水势构成结构,结果发现,在陇东黄土塬区,坡头荒地等较干旱、沙质土壤中,包气带水分变化呈对数分布特征,而耕作土壤其水分含量特征则不满足这种类型.在土水势构成方面,溶质势所占比例平均约为20%,其中坡头荒地约占15%,耕地中约占25%;基质势所占比例最大,在坡头荒地占近80%,耕地样本的平均比例超过60%.溶质势各分势构成方面,起主导作用的阴离子为HCO,起主导作用的阳离子为Ca.黄土塬区HCO和Ca所占溶质势的比重分别约为50%和25%;Na和Cl各约占10%.%This paper studys soil moisture distribution and composition of soil water energy at unsaturated zone in East Gansu. The results are as follows: Soil water mass content characteristics are logarithmic in the more arid Potou wasteland,sand and non-cultivated soil in the Loess Plateau of East Gansu, while moisture content of the arable soil is affected by its soil texture, displaying quite difference. In the unsaturated zone of the Loess Plateau, the proportion of solute potential is about 15% at Potou wasteland, while it can be up to about 25% in the farmland. Matric potential accounts for nearly 80% in Potou of the arable and is 60% in average content in farmland, which is of the largest proportion of the soil water pertential. HCO3- plays a leading role of anios in the solute potential of the unsaturated zone, and leading cation is Ca2 + in the loess area. Soil solute potential in the weight of the plasma ions is the largest HCO3- and Ca2+ , which is about 50% and 25% respectively of the solute potential in the Loess Plateau, Na+ and Cl- are about 10%.

  12. 区域生态安全动态变化及空间差异定量分析:以陕北黄土高原为例%Quantitative analysis of the dynamic change and spatial differences of the ecological security:a case study of Loess Plateau in northern Shaanxi Province

    Institute of Scientific and Technical Information of China (English)

    李晶; 任志远; 周自翔

    2006-01-01

    Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecological carrying capacity and ecological surplus/loss in 1986-2002 on the Loess Plateau in northern Shaanxi Province. What is more, this paper has put forward the concept of ecological pressure index, set up ecological pressure index models, and ecological security grading systems, and the prediction models of different ecological footprints, ecological carrying capacity, ecological surplus and ecological safety change, and also has assessed the ecological footprint demands of 10,000 yuan GDP.The results of this study are as follows: (1) the ecological carrying capacity in northern Shaanxi shows a decreasing trend, the difference of reducing range is the fastest; (2) the ecological footprint appears an increasing trend; (3) ecological pressure index rose to 0.91 from 0.44 during 1986-2002 on the Loess Plateau of northern Shaanxi with an increase of 47%; and (4) the ecological security in the study area is in a critical state, and the ecological pressure index has been increasing rapidly.

  13. 黄土高原水土保持林对土壤水分的影响%Soil moisture dynamics of water and soil conservation forest on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    张建军; 李慧敏; 徐佳佳

    2011-01-01

    黄土高原植被恢复的限制因素主要是土壤水分,植被与土壤水分关系的研究对黄土高原植被恢复具有重要意义.2008年7月1日至2009年10月31日间采用EnviroSMART土壤水分定位监测系统以每30min监测1次的频度,对晋西黄土区刺槐人工林地、油松人工林地、次生林地的土壤水分变化进行了研究.研究得出:次生林地0-150 cm土层中平均蓄水量为331.95mm,刺槐人工林地为233.85 mm,有整地措施的油松人工林地为314.85mm,刺槐人工林比次生林多消耗的98.10mm土壤水分主要来源于80 cm以下土层.次生林主要消耗0-80 cm土层的水分,而人工林不但对0-80 cm土层水分的消耗量大于次生林,对深层土壤的消耗也较次生林大,这将有可能导致人工林地深层土壤的“干化”.在土壤水分减少期(11-1月)刺槐人工林土壤水分的日均损耗量为0.86mm、油松人工林为0.82 mm、次生林为0.84 mm.土壤水分缓慢恢复期(2-5月)刺槐人工林地土壤水分的恢复速度0.90mm/d,油松人工林地为0.53 mm/d、次生林地为0.79 mm/d.土壤水分剧烈变化期(5-10月)刺槐人工林地土壤水分含量的极差为95.71mm,油松人工林地为179.1mm,次生林地为72.03mm.在干旱少雨的黄土高原进行植被恢复时,应多采取封山育林等方式,依靠自然力量形成能够与当地土壤水资源相协调的次生林,是防止人工植被过度耗水形成“干化层”、保障水土保持植被持续发挥生态服务功能的关键.%Soil moisture was the limiting factor for vegetation rehabilitation on the Loess Plateau in China. Understanding the relationship between vegetation and soil moisture was important to soil and water conservation. During the period of July 1, 2008 and October 31, 2009, we measured soil moisture dynamics of Robinia pseudoacacia plantations, Pinus tabulaeformis plantation and the secondary forests every 30 minutes on the Loess Plateau in western ShanXi Province

  14. Asian summer monsoon precipitation recorded by stalagmite oxygen isotopic composition in the western Loess Plateau during AD1875-2003 and its linkage with ocean-atmosphere system

    Institute of Scientific and Technical Information of China (English)

    LIU JingHua; SANG WenCui; Kathleen R.JOHNSON; ZHANG PingZhong; CHENG Hai; CHEN FaHu; YANG XunLin; ZHANG DeZhong; ZHOU Jing; JIA JiHong; AN ChunLei

    2008-01-01

    Based on 5 high-precision 230Th dates and 103 stable oxygen isotope ratios (δ18O) obtained from the top 16 mm of a stalagmite collected from Wanxiang Cave,Wudu,Gansu,variation of monsoonal precipita- tion in the modern Asian Monsoon (AM) marginal zone over the past 100 years was reconstructed.Comparison of the speleothem δ18O record with instrumental precipitation data at Wudu in the past 50 years indicates a high parallelism between the two curves,suggesting that the speleothem δ18O is a good proxy for the AM strength and associated precipitation,controlled by "amount effect" of the pre-cipitation.Variation of the monsoonal precipitation during the past 100 years can be divided into three stages,increasing from AD 1875 to 1900,then decreasing from AD 1901 to 1946,and increasing again thereafter.This variation is quite similar to that of the Drought/Flooding index archived from Chinese historical documents.This speleothem-derived AM record shows a close association with the Pacific Decadal Oscillation (PDO) between AD 1875 and 1977,with higher monsoonal precipitation corre-sponding to cold PDO phase and vice versa at decadal timescale.The monsoonal precipitation varia- tion is out of phase with the PDO after AD 1977,probably resulting from the decadal climate jump in the north Pacific occurring at around AD 1976/77.These results demonstrate a strong linkage between the AM and associated precipitation and the Pacific Ocean via ocean/atmosphere interaction.This rela-tionship will aid to forecast future hydrological cycle for the AM monsoon region,and to improve forecasting potential of climatic model with observation data from cave.

  15. Effects of conservation tillage on soil aggregates in dry land of loess plateau%黄土高原旱地保护性耕作农田土壤团聚体特性变化研究

    Institute of Scientific and Technical Information of China (English)

    赵如浪; 冯佰利; 蒋树怀; 张小东; 屈洋; 蔡晓青; 朱瑞祥

    2011-01-01

    以春玉米品种沈玉17为材料,设置保护性耕作(NT)、传统耕作+秸秆还田(TS)和传统耕作(CT)3种耕作方式,通过多年定位试验,研究黄土高原旱塬地保护性耕作农田土壤有机质及团聚体特性的变化。结果表明,NT与TS和CT相比能显著提高土壤有机质含量。干筛法分析结果表明,0-30 cm深度,NT处理粒径〉0.25mm的大团聚体含量、平均重量直径(mean weight diameter,MWD)均显著高于TS和CT处理。湿筛法分析结果表明,水稳性团聚体MWD在0-10 cm深度为NT〉TS〉CT,处理间差异显著%The paper studied the effects of conservation tillage on the soil aggegate and organic carbon by years on Loess Plateau.The spring maize cultivars Shenyu17 were used in the test under three farming modes of No tillage(NT),conventional tillage+Straw returning(TS) and conventional tillage(CT).To study the effects,soil organic matter content was measured,and the aggregates composition,size distribution were examined by dry and wet sieving methods.The results showed that,NT significantly increased soil organic matter content compared with TS and CT.Dry sieving results showed that NT was higher in macro-aggregate content(R〉0.25) and mean weight diameter(MWD) than other treatments at 0-30 cm.Wet sieving results showed that the MWD of water-stable aggregates showed the trend:NT〉TS〉CT at 0-10 cm,Their differences reached the significant level of P〈0.05 among the three tillage treatments.At 0~20cm,Destruction rate of aggregate under NT was higher than CT.NT increased the aggregation and the stability of soil aggregates,while due to intense disturbance,the aggregation and stability were decreased under CT.

  16. 陇东旱塬区玉米高产集成技术与示范%Research and Demonstration of Integrated High Yield Corn Cultivation Technology on the Loess Plateau Region of East Gansu

    Institute of Scientific and Technical Information of China (English)

    史聚宝

    2012-01-01

    陇东旱塬区玉米(Zea mays L.)高产集成技术是以全膜覆盖、双垄沟播技术为核心,集成组装测土配方施肥+良种应用+适期早播、宽窄行密植+病虫害监测防控等技术,推出“全膜覆盖玉米(留膜免耕)-冬油菜(留膜免耕)-大豆(高塬夏菜)”两年三熟制种植模式.该技术在甘肃省泾川县经5年推广试验示范,玉米平均增产3 247.5 kg/hm2,增加产值7 306.9元/hm2,较对照(常规种植)增加生产成本1 357.5元/hm2,新增总产值19 641.5万元,新增总纯收益15 941.7万元,产投比5.3∶1,科技投资收益率431%,推广投资收益率4 460%,取得了极显著的社会效益和经济效益.%The core of integrated high yield corn (Zea mays L.) cultivation technology on the Loess plateau region of east Gansu was double ridges with whole plastic film cover. By integrating fertilization according to soil testing, elite seed application, suitable early sowing, reasonable planting dense and pest monitor-control technology, the "mulching corn (film remaining and no-tillage)-winter rape (film remaining and no-tillage)-soybean (high tableland summer vegetable)" with three mature in two years planting model was put forward. Through experiment and demonstration plant for 5 years in Jingchuan of Gansu, the average yield of corn was increased by 3 247.5 kg/hm2, with the output value increasing by 7 306.9 Yuan/hm2 compared with control. The cost of production was increased by 1 357.5 Yuan/hm2; while the total output value was increased by 19 641.5 million yuan, thus the total net income was increased by 15 941.7 million Yuan with the output to input ratio 5.3:1. The return of science and technology investment was 431%; of promotion investment was 4 460%, with remarkable social and economic benefits.

  17. Progress in the Study of Soil Water Balance under Forest and Grassland Covers on the Loess Plateau%黄土高原林草地覆盖土壤水量平衡研究进展

    Institute of Scientific and Technical Information of China (English)

    李海防; 卫伟; 陈利顶; 郭二辉; 黄勇

    2013-01-01

    黄土高原地处干旱半干旱区,水是地区生态环境改善的主要限制因子,严重阻碍了当地的植被恢复和生态重建.黄土高原林草地覆盖土壤蓄水量既有收入,又有支出,始终处于一种动态平衡但相对亏缺的状态.以黄土高原降雨时空变化、林草地土壤水分入渗、土壤水分蒸发蒸腾、土壤干层的形成以及水量平衡模型模拟等几个关键因素为切人点进行详细阐述,对其国内外研究进展进行回顾.提出关于黄土高原土壤水量平衡的研究,应在成熟林草地水源涵养功能及林草地水文生态过程的尺度扩展方面加大力度.%Most parts of the Loess Plateau were located in arid and semi-arid areas, and soil water was a crucial factor influencing vegetation restoration and eco-environrnental reconstruction. Water was transferred continuously between soil, vegetation and atmosphere and kept in a dynamic balance in the soil. Former studies in relation to specific fields such as the spatial and temporal variation of precipitation, water infiltration, evapotranspiration, dried soil layer and modeling on soil water balance under forest and grassland covers were summarized and analyzed systematically. In addition, we suggested that research should focus on the counterbalancing function of water holding capability of vegetation and eco-hydrological process and its scaling up in forest and grass land.

  18. Spatial variation in the storages and age-related dynamics of forest carbon sequestration in different climate zones-evidence from black locust plantations on the Loess Plateau of China.

    Directory of Open Access Journals (Sweden)

    Taijun Li

    Full Text Available Knowledge about the long-term influences of climate change on the amount of potential carbon (C sequestration in forest ecosystems, including age-related dynamics, remains unclear. This study used two similar age-sequences of black locust forests (Robinia pseudoacacia L. in the semi-arid and semi-humid zones of China's Loess Plateau to assess the variation in C stocks and age-related dynamics. Our results demonstrated that black locust forests of the semi-humid zone stored significantly more C than did forests in the semi-arid zone, across the chronosequence (p < 0.001. The C carrying capacity of the plantations was measured at 166.4 Mg C ha-1 (1 Mg = 106 g in the semi-humid zone, while the semi-arid zone had a capacity of only 79.4 Mg C ha-1. Soil organic C (SOC increased continuously with stand age in the semi-arid zone (R2 = 0.84, p = 0.010. However, in the semi-humid zone, SOC declined sharply by 47.8% after the initial stage (5 to 10 y. The C stock in trees increased continuously with stand age in the semi-humid zone (R2 = 0.83, p = 0.011, yet in the semi-arid zone, it decreased dramatically from 43.0 Mg C ha-1 to 28.4 Mg C ha-1 during the old forest stage (38 to 56 y. The shift from being a net C sink to a net C source occurred at the initial stage in the semi-humid zone versus at the old forest stage in the semi-arid zone after reforestation. Surprisingly, with the exception of the initial and later stages (55 y, the patterns of C allocation among trees, soils, understory and litter were not statistically different between the two climate zones. Our results suggest that climate factors can alter the potential amount and age-related dynamics of forest C sequestration.

  19. 藻类结皮对黄土高原地区土壤蒸发过程的影响%Effects of Soil Algae Crust on Soil Evaporation in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    王翠萍; 周欢水; 廖超英; 孙长忠; 韩小红

    2011-01-01

    利用自制的微型蒸发器观测了山西偏关县藻类结皮覆盖土壤和无结皮土壤的蒸发过程,对土壤的蒸发强度、累积蒸发量等进行了对比分析.结果表明:藻类结皮对土壤蒸发过程有一定影响,但其影响机理不是简单的“促进”或“抑制”,而是当土壤含水量较高时,藻类结皮覆盖土壤的蒸发能力明显高于无结皮土壤,当土壤逐渐变干时,结皮封闭了土壤表面,并将水分束缚在土壤中,有效降低了土壤蒸发能力.藻类结皮对雨后土壤蒸发的影响在不同阶段有所不同,降雨发生后的前期阶段,结皮覆盖土壤的蒸发量明显高于无结皮土壤,而后期阶段,结皮覆盖土壤的蒸发量低于无结皮土壤.%Taking the Loess Plateau in Pianguan County, Shanxi Province as the research region, the soil water evaporation process was comparatively studied in the soils with and without algae crust by micro-ly-simeter from the view of evaporation intensity and cumulative evaporation. The results showed that soil algae crust significantly changed evaporation process of the soil. The influence mechanism of algae crust on soil evaporation was not simple promotion or inhibition. When soil water content was higher, soil water e-vaporation on soil with algae crust was higher compared to that without crust. However, when soil was gradually drying, soil algae sealed the soil surface, restrained water in the soil and reduced soil evaporation. Soil algae crust in different stages after rainfall had significantly different effect on soil water evaporation. The earlier stage after rainfall, soil evaporation on soil with algae crust was significantly greater than that on soil without crust, and then lower later phase after rainfall.

  20. THE LOESS FROM ROMANIA IN THE ROMANIAN SPECIALISTS VISION

    Directory of Open Access Journals (Sweden)

    Alina Gherghina

    2006-10-01

    Full Text Available As a lithological formation, the loess was for the first time mentioned in the geological works of the 19 century (the first Romanian describe of the loess deposits was given by Gr. Stefanescu in 1895 and the aeolian origin of the loess was stated for the first time in our country by L. Mrazec, in 1899. According to Em. Protopopescu-Pache et. al (1966, the loess deposits covers an area of 40 000 km2, dispersed on the interfluves and the terrace bridges in the peri-carpathian regions (especially in the Romanian Plain and Dobrogea, at which are added some terraces and some weakly inclined slopes from the sub-carpathian region, Transylvanian Plateau and the intramontanian depression. Both in the first studies (Mrazec L. 1899, Murgoci et al 1908 and in those published between the two World Wars was agreed the aeolian origin of the loess and the fossil soils received a stratigraphyc value. After the two World War, the loess study (as quaternary deposit was approached by researchers from different domains: hydrogeology, pedology and geography, who emitted different assumptions of the loess origin (aeolian, deluvial or alluvial – the loessic features of the material being considered as a result of a postsedimentary diagenesis process and contribute to the knowledge and the characterization of the loess from Romania.

  1. 黄土高原小流域不同地形下土壤有机碳分布特征%The distribution of soil organic carbon as affected by landforms in a small watershed of gully region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李林海; 郜二虎; 梦梦; 魏孝荣

    2013-01-01

    研究了黄土高原小流域尺度塬面、坡地、沟道和梯田4种地形条件下土壤有机碳总量和活性组分的分布、储量及碳库管理指数的差异.结果表明,小流域土壤有机碳和不同活性有机碳的变异系数介于32%-70%之间,表现出中到高度的变异特征.4种地形下各组分有机碳含量和储量以塬面土壤最高,沟道土壤最低,并随土层深度的增加而降低,降低程度随有机碳活性增强而增加.以塬面土壤为对照所获得的碳库管理指数可灵敏指示有机碳对地形条件的响应特征,中活性有机碳库管理指数的指示效果最好.研究结果可部分解释黄土高原土壤有机碳地带性分布特征.%Soil organic carbon plays important role in soil quality changes and terrestrial carbon cycling. However, the relationships between soil organic carbon distribution and landscape positions were not well understood, which are essential for the precisely predication of the spatial distribution of soil organic carbon and for the rational management of soil organic carbon, as well as for the assessment of the dynamics of soil organic carbon at different landscape positions at different landscape scales. China's Loess Plateau is a major region for agricultural production, and an ecological ecotone in northwest China, which suffers serious land degradation and ecologically economic problems due to the soil erosion in the region. The distribution and cycling of soil organic carbon were related not only with the maintaining and improving of soil quality in the region, but also with the response and adaptation of soil ecosystems to the future global climate change, and thus should be carefully assessed. In this study, we investigated the distribution of soil organic carbon and labile organic carbon at various landforms, that is, plateau land, sloping land, gully bottom and terrace land. We also anlyzed the differences of carbon management index at various landscape

  2. Impact of Biological Soil Crust on Soil Physical Properties in the Hilly Loess Plateau Region,China%黄土丘陵区生物结皮对土壤物理属性的影响

    Institute of Scientific and Technical Information of China (English)

    高丽倩; 赵允格; 秦宁强; 张国秀; 杨凯

    2012-01-01

    Biological soil crusts(biocrusts) are ubiquitous living surface covers in many arid and semi-arid regions.It has been demonstrated that the coverage of biocrusts was over 70% in the hilly Loess Plateau region of China and it played many important roles,such as exerting observably impact on soil properties and improving soil antierodibility.But the response of soil physical properties to the development of biocrusts has been unclear so far.The objective of the study was to determine the impact of development of biocrusts(i.e.with variable biomass) on soil physical properties in hilly Loess Plateau region.In this study,soil samples were collected after biocrusts and vegetation coverage survey,and the soil physical properties including soil bulk density,soil porosity,field water holding capacity,cohesion and hardness of biocrusts in different developmental stages were determined.The results showed: 1) Fine particles content increased due to the development of biocrusts.The content of coarse sand decreased by 86% while fine sand increased by 45% with biocrusts developing from cyanobacteria dominated to moss dominated(biomass of moss was 4.31±0.12 g/dm^2).2) With the development of biocrusts,soil bulk density and hardness were reduced while field water holding capacity,soil porosity and cohesion were increased significantly.Along with the development of biocrusts,soil bulk density was dropped by 15%.Soil hardness of biocrusts in later development stage was reduced by 68% compared with the early stage.Field water holding capacity was increased to 57%,adding about 36% compared with the early stage,while soil porosity gone up to 58%,increasing by about 14%.Cohesion of biocrusts was 6 or 7 times as much as that of subsurface soil(0-2 cm).3) Impact of biocrusts on soil physical properties was closely related to biocrusts'biomass.When biomass of moss in biocrusts was to 2.91±0.12 g/dm^2,soil physical properties changed no longer significantly.4

  3. SPRING FESTIVAL ON THE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    亦西; 杨延康

    2005-01-01

    How Spring Festival is celebrated Although the date of the Spring Festival was switched from the beginning of spring to the first day of the first lunar month, the main ways of celebrating it, from bygone days, remain popular.

  4. 黄土高原吕二沟流域不同植被下的坡面径流特征%Characteristics of Slope Runoff under Different Vegetation Conditions in Lvergou Watershed of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    varied because of its different vegetation, soil conditions and roots, etc. Under the same rainfall conditions, the runoff of four plots with different vegetation types showed shrub> mixed> locust> pine. The same law was also exhibited in surface runoff with the performance of shrubs> locust> pine> mixed. While subsurface flow was different from the both above with the performance of mixed > pine> shrub> locust. The main form of slope runoff of locust and shrub runoff plots was surface runoff, which accounted for 95.61% and 91.62% of the total runoff respectively. The main form of slope runoff of mixed runoff plots was subsurface flow, which accounted for 90.86%. The surface runoff and subsurface flow of slope runoff of pine runoff plots accounted for 61.99% and 38.01% respectively. Precipitation, especially for the Loess Plateau which seasonally rains obviously, is the main source of runoff. When the rainfall reaches a certain threshold, runoff process will be produced. The effects of rainfall intensity on surface runoff and subsurface flow were different. Antecedent soil moisture was a very important factor which affected slope producing flow.

  5. 陇东黄土高原农田土壤湿度演变对气候变化的响应%Responses of Soil Moisture Evolution in Cropland to Climate Change on Longdong Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    严丽; 王飞; 蒋冲; 穆兴民

    2012-01-01

    以甘肃省庆阳市西峰区为例,利用近50a气象观测资料和近20a的土壤湿度观测资料,分析全球气候变暖背景下陇东主要气象要素及土壤湿度的变化特征,研究了气候变化对土壤湿度的影响。50a来陇东气温呈波动上升趋势,降水量呈波动减少趋势。1991—2010年陇东各层土壤湿度总体上均呈现出下降趋势,春季是土壤湿度减少最明显的季节,夏季土壤湿度变化趋势与春季具有类似规律,但变化率明显低于春季。秋季浅层土壤湿度呈下降趋势,深层呈上升趋势。就表层土壤湿度而言,各季土壤湿度与该季气温均为负相关,与降水量呈正相关。而对较深层土壤而言,土壤湿度与气温、降水的相关关系因季节而异。潜在蒸散量对土壤湿度的影响月份和年际变化均呈现出反位相的特点,基本呈同步变化趋势。通过对农田土壤水分演变特征及其影响因素进行分析,为进一步理解土壤水分的演变,合理利用气候资源,调整农业生态布局,积极应对气候变化提供决策方面的参考。%In a case study of Xifeng City on the Longdong Loess Plateau,climate change trends and its effects on soil moisture,as well as the evolution of soil moisture were analyzed based on the 50-year climate data and the 20-year observation data of soil moisture.Results show that temperature increased and rainfall decreased in the recent 50 years.From 1991 to 2010,soil moisture in Longdong presented a downward trend on the whole.In spring,soil moisture decreased more severely and in summer,soil moisture had a similar trend,but the rate of change was significantly lower than that in spring.In fall,soil moisture in shallow soil layer showed a downward trend,while the deep soil presented a rise trend.For topsoil,soil moisture in each season was negatively correlated with temperature and positively correlated with precipitation.For deeper soil layer,the correlations of soil

  6. Effect of Forest Gap on Regeneration of Dominant Species in Malan Forest Area on the Loess Plateau%林隙对黄土高原马栏林区优势种更新的影响

    Institute of Scientific and Technical Information of China (English)

    李峰; 王孝安

    2011-01-01

    Forest gap disturbs the forest structure and dynamics of forest. Quercus liaotungensis and Pinus tabu-laeformis are the dominant species in the main community types in Malan forest area on the Loess Plateau. In this paper, the seedlings and saplings of these two species in various-sized forest gaps are measured, and the seedlings and saplings in gaps and under the canopies are compared and analyzed. The results show that these two dominant species have different regeneration strategies, that is, Q. Liaotungensis regenerates its population by relying on its high germination, while P. Tabulaeformis regenerates its population by reducing the mortality rate of its seedlings and saplings. When the gap area is 20 -40 m2, the natural regeneration of P. Tabulaeformis is the best, but the natural regeneration of Q. Liaotungensis in various-sized gaps is more complex. Forest gap disturbance can promote the natural regeneration of these two dominant species. In the future, the dominance of the Q. Liaotungensis and P. Tabulaeformis in the Q. Liaotungensis forest and P. Tabulaeformis forest will not be replaced each other by forest gap disturbance. So Q. Liaotungensis and P. Tabulaeformis in the Q. Liaotungensis forest and P. Tabulaeformis forest will exist for a long period as the succession climax and subclimax in this area.%林隙对森林的结构和动态具有重要的影响.黄土高原马栏林区主要群落类型中,对优势种辽东栎(Quercusliaotungensis)、油松(Pinus tabulaeformis)不同大小林隙内的幼苗和幼树进行统计计算,并与林冠下进行对比分析.结果表明:两个优势种存在不同的更新策略,即辽东栎主要通过高萌发量来维持其种群的更新,而油松则是通过降低幼苗到幼树过程中的死亡率来维持其种群的更新;林隙面积在20~40m2时油松的自然更新情况最好,而辽东栎在不同大小林隙中的自然更新情况较为复杂;适当的林隙干扰总体上促

  7. 历史时期黄土高原生态环境建设分析%Analysis on Eco-environment Construction in Human Period on Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    王飞; 李锐; 谢永生

    2001-01-01

    -environment construction, especially in water engineering, soil improvement and soil and water conservation, was so outstanding that many of them are important today. The experiences in history can be used to accelerate the step of environment harness. Under the historic current chance of development in west area of China, the scientific views and ways on development should be considerated carefully to make Loess Plateau beauty as soon as possible.

  8. 陕北黄土高原刺槐植物功能性状与气象因子的关系%Relationships between Plant Functional Traits of Robinia Pseudoacacia and Meteorological Factors in Loess Plateau, North Shaanxi, China

    Institute of Scientific and Technical Information of China (English)

    宋光; 温仲明; 郑颖; 丁曼

    2013-01-01

    To elucidate the variation in plant functional traits and adaptive strategies of Robinia Pseudoacacia on the Loess Plateau,we measured 10 plant functional traits of Robinia Pseudoacacia in 14 counties along the middle area to the north of Shaanxi province,and analyzed the relationships among these functional traits along environmental gradients.The results showed that leaf nitrogen content (LNC) and root nitrogen content (RNC) have no significant differences among 14 sampling points,while other 8 plant functional traits showed significant differences among sampling points (P < 0.05).Specific leaf area (SLA),leaf thickness (LT),leaf tissue density (LTD) and specific root length (SRL) have significant negative correlations,and root tissue density(RTD) and specific root length(SRL) has the remarkable negative correlation.Different enviromental factors had different impact on plant functional traits.It showed that mean annual precipitation has the greatest impact on plant functional traits of Robinia pseudoacacia,and followed by mean annual temperature and annual sunlight ratio according to the stepwise regression analysis.%为阐明刺槐植物功能性状在黄土高原不同环境下的变异规律,探明刺槐对黄土高原环境的适应策略,对陕西省境内从中部向北的14个县(市、区)的刺槐植物功能性状进行测定与统计分析.研究了不同生境刺槐植物功能性状的种内差异、刺槐功能性状间的相关关系及气象因子对刺槐植物功能性状的影响.结果表明:(1)除叶氮含量(LNC)、根组织密度(RTD)和根氮含量(RNC)在各采样点之间的差异不显著之外,其他8个性状在各采样点之间均表现出显著的差异(P<0.05).(2)刺槐植物功能性状相互之间都有一定的相关关系,比叶面积(SLA)与叶厚度(LT)、叶组织密度(LTD)和比根长(SRL)呈极显著负相关关系,根磷含量(RPC)与叶磷含量(LPC)和比根长(SRL)呈显著正相关关系,根组织密度(RTD)

  9. Stationarity and Change Trend of Streamflows in Forest and Less Forested Watersheds on Loess Plateau%黄土高原森林/非森林流域径流稳定性及其演变趋势对比

    Institute of Scientific and Technical Information of China (English)

    谢名礼; 张晓萍; 刘二佳; 陈妮; 张亭亭; 郭敏杰

    2013-01-01

    The stationarity of streamflows over the past 50 years were investigated for well/poorly forested watersheds in the Beiluohe River basin on the Loess Plateau,using concentration degree and concentration period methods.The change trend and change point were checked with nonparametric M-K,Pettitt and Rank-sum tests.Results show that all the five watersheds studied were characterized by the high fluctuation of annual streamflow and the double peaks of inner-annual hydrograph.Forested ones presented mild slopes and less forested ones,steep shapes.In contrast,the streamflows were better distributed in well forested watersheds where the concentration period was 1 month behind the poorly forested counterpart.Different components of the streamflow in forested watersheds did not show a significant trend or change point,while significant decrease and change points were detected in annual streamflow and the components in summer,fall and flood season for less forested watersheds in the past 50 years.In both annual and inner-annual scales,the streamflow in forested watersheds was considered more stable than that of the less forested,which implies that less forested watersheds still demands a long-term construction and conservation for the eco-environment to recover.%采用集中期、集中度等方法及M-K,Pettitt等非参检验法对比分析了黄土高原北洛河子午岭森林流域与相邻丘陵沟壑区非森林流域近50 a来的径流稳定性差异及演变趋势,为黄土高原地区生态治理的水文效应分析提供参考和借鉴.结果表明,黄土高原子午岭林区和非林区流域径流量年际尺度分布表现出一致的强变异性,年内分布均为双峰型特征,但林区峰型平缓,非林区陡峭.林区流域年内分布较非林区流域均匀,前者径流集中期较后者滞后1个月.近50 a来林区流域径流量无明显变化趋势,而非林区流域年、夏、秋及汛期径流量表现出显著性减少趋势,且有显著的跃

  10. 保护性耕作对黄土高原旱田春玉米生物学效应的影响%Biological Effects of Conservation Tillage on Spring Maize in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    孙平阳; 赵如浪; 刘月仙; 高金锋; 王鹏科; 朱瑞祥; 冯佰利

    2011-01-01

    于2006-2010年,在黄土高原中部高原沟壑区,研究保护性耕作对黄土高原春玉米生物学效应的影响.结果表明,与传统耕作相比,保护性耕作处理下春玉米在各关键生育时期次生根条数、株高、茎粗、穗位叶面积和农田生物量积累均较高,保护性耕作+植保防治处理下春玉米各生育时期均以保护性耕作处理下的BJG处理(保护性耕作+先正达包衣种子+金都尔耕杰植保碎秆浅旋秸秆全程覆盖)最高.耕作模式和植保防护措施对春玉米穗长、行粒数、穗粒数和千粒质量等产量构成指标影响较大,BJG和CC处理(保护性耕作+市售包衣种子+常规植保)与BO处理(保护性耕作+市售包衣种子+无杂草防治)、CK处理(传统耕作+市售包衣种子+无杂草防治)穗长差异极显著(P<0.01),保护性耕作下各处理间穗粒数和千粒质量间差异达极显著水平.保护性耕作增产明显,平均春玉米单株和大田产量增产幅度均高达25.31%,BJG处理春玉米单株和大田产量较BO和CK处理增产幅度分别达36.17%和41.48%.%In order to discover the biological effects of conservation tillage on spring maize in Loess Plateau, this research was carried out from 2006 to 2010. Compared with conventional tillage, spring maize plants treated with conservation tillage have more secondary roots,higher plant height,stem diameter, ear leaf area and farmland biomass accumulation in the key stages; the highest values were detected in the growth stages of spring maize with conservation tillage and BJG treatments. Conservation tillage and plant protection measures have big effects on the spring corn ear length, kernels per row,grain numbers per ear and 1000-grain weight. Ear length was significant different between BJG/ CC and BO/CK treatments,and grain numbers and 1000-grain mass under conservation tillage reachedthe significant different level bet-ween treatments. Significant increase of the yield was detected

  11. Characteristics of woody debris in a natural secondary forest on Loess Plateau, China%黄土高原天然次生林木质残体的基础特征

    Institute of Scientific and Technical Information of China (English)

    顾丽; 屈宏胜; 王广儒; 李卫忠

    2016-01-01

    Woody debris ( WD) plays an indispensable role in ecosystem nutrient cycling and forest development. We studied the characteristics of WD in natural secondary Pinus tabulaeformis mixed stands in Huanglong Mountain, Loess Plateau. Results showed that:(1) the gross reserve of WD of natural mixed forest was 10.73 t•hm-2, with 10.31 t•hm-2(96.09%) from coarse woody debris and 0.42 t•hm-2(13.91%) from fine woody debris. And coarse woody debris was mainly attributed to fallen trees;(2) Ex-ponential models indicated that decomposition density of WD was inversely proportional to decaying level;( 3) Woods at diameter of 20-30 cm and 30-40 cm were the main source of WD reserve in terms of quantity and proportion. To summerize, overall evaluation of WD in natural secondary forest provides insight into structural characteristics of wood in late succession stage of mixed forest de-velopment.%以黄土高原黄龙山林区典型的天然次生林为研究对象,研究油松针阔混交林木质残体的基础特征.结果表明:研究区木质残体的总储量为10.73 t•hm-2,其中粗木质残体的储量为10.31 t•hm-2,占总储量的96.09%;细木质残体的储量为0.42 t•hm-2,占总储量的3.91%;在粗木质残体中,倒木占了绝大部分,其次为枯立木,大枝和树桩贮量很少.采用指数模型来模拟研究区主要树种木质残体的分解密度,曲线拟合度很高.拟合结果表明木质残体密度随着腐烂等级的增加而呈下降趋势;木质残体的径级主要集中在20~30 cm与30~40 cm 2个径级,二者在株数与储量分布中占绝对优势.存在状态主要为中级腐烂状态,干扰与竞争是木质残体产生的主要因素.研究区天然次生油松针阔混交林木质残体的基础特征反映了该林区森林群落演替后期木质残体的结构特征.

  12. 黄土丘陵区生物结皮对土壤可蚀性的影响%Effects of biological soil crust on soil erodibility in Hilly Loess Plateau Region of Northwest China

    Institute of Scientific and Technical Information of China (English)

    高丽倩; 赵允格; 秦宁强; 张国秀

    2013-01-01

    在采样分析生物结皮对土壤理化属性影响的基础上,采用EPIC模型估算与模拟降雨试验相结合的方法,研究了黄土丘陵区不同生物量、不同土壤质地和不同季节的生物结皮对土壤可蚀性(K值)的影响.结果表明:生物结皮显著降低了土壤可蚀性,生物结皮层土壤可蚀性较下层土壤降低17%;土壤可蚀性随生物结皮生物量的增加呈降低趋势,藓结皮土壤可蚀性K值较藻结皮土壤降低21%;生物结皮土壤可蚀性在不同季节因其生物活性不同而存在差异,雨季中显著高于雨季前和雨季末;不同质地土壤上生物结皮对可蚀性的影响不同,可蚀性K值为砂壤>粉壤>砂土;模拟降雨条件下测定表明,生物结皮的发育使土壤可蚀性较对照(下层5~10 cm土壤)降低约90%.%Based on the analysis of the effects of biological soil crust (biocrust) in re-vegetated grasslands on soil physical and chemical properties, and by using EPIC estimation model in combi-ning with simulated rainfall trials, this paper studied the effects of biocrust with different biomass and different soil texture on the soil credibility (K value) in Hilly Loess Plateau Region of North-west China in different seasons. The results showed biocrust could significantly decrease soil erod-ibility, with the K value of biocrust soil decreased by about 17% , compared with subsoil. The soil erodibility decreased with the increasing biomass of biocrust. The K value of moss crust soil de-creased by 21% , compared with cyanobacteria crust soil. The erodibiliy of biocrust soil differed with different seasons, being significantly higher in rainy season than before or after the rainy season due to the differences in the biological activity of the biocrust organisms. The erodibilty of biocrust soil with different texture also varied significantly, with the K value in the order of sandy loam soil > silt soil > sandy soil. The measurement under simulated

  13. 黄土区小流域土壤容重和饱和导水率的时空动态特征%Spatio-temporal characteristics of soil bulk density and saturated hydraulic conductivity at small watershed scale on Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    傅子洹; 王云强; 安芷生

    2015-01-01

    Surface soil bulk density (BD) and saturated hydraulic conductivity are two of important parameters to assess rainfall infiltration, runoff formation and soil erosion. But little research has been done at a watershed scale. On the Loess Plateau of China, investigations on the spatio-temporal changes of BD and saturated hydraulic conductivity at a small watershed scale are essential for regional ecological restoration and may enrich our understanding on the related eco-hydrolgical processes. In this study, we measured BD and saturated hydraulic conductivity in August, September, and October of 2014 at 73 sites that were pre-located by using Global Positioning System in a 50 m × 50 m grid at the LaoYeManQu watershed on the wind-water erosion crisscross region of the Chinese Loess Plateau. Using classical statistical and geostatistical methods, we characterized and compared the spatial and temporal changes of BD and saturated hydraulic conductivity. The semivariograms and kriging method included in the geostatistical method were used to reflect the visual variation among different months from August to October. Results showed that: 1) Among the three months, BD had a normal distribution and exhibited a time stability while saturated hydraulic conductivity had a skewed distribution and varied greatly. BD variation was smaller than that of the saturated hydraulic conductivity at the watershed scale. 2) Semivariograms of BD and saturated hydraulic conductivity from August to October could be best fitted by an isotropic exponential model. Both BD and saturated hydraulic conductivity exhibited a moderate spatial dependence. Distribution maps produced by kriging indicated pronounced spatial patterns of BD and saturated hydraulic conductivity at the small watershed—at the slope top and the western part of the watershed, BD demonstrated an increasing trend while saturated hydraulic conductivity decreased gradually from August to October. 3) Pearson correlation analysis

  14. 基于GIS的水量平衡模型在黄土高原地区土壤水分模拟中的应用%The Application of GIS-based Soil Water Balance Model on Simulating Soil Water Dynamic Conditions in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    邸苏闯; 游松财; 刘喆惠

    2012-01-01

    A continental scale GIS-based soil water balance model is used to simulate the spatial and temporal distribution and the changing trend of soil water in Loess Plateau from 2001 to 2010. Parameters such as soil type and texture, vegetation type, eleva- tion, meteorological factors are taken into account in this model. Temporally, the average soil water in Loess Plateau change trend shows a "sine line", the minimum soil water content appears in June with the value of 36. 9 mm and the maximum in October with the value of 74.3 ram. The soil water descends from October to next June while it ascends from June to October. Spatially, the northwest part of Loess Plateau has limited soil water with the value of 1~40 mm and narrow change range for the less precipitation and high evaporatranspiration, while in the southeast part of Loess Plateau, the soil water changes shows the similar pattern with precipitation temporal and spatial distribution patterns. In late autumn the soil moisture attains the highest value of 200~240 mm, while in early summer, it descends to the lowest point of 60~100mm. Average annual precipitation is 435.8 mm with the descending trend from southeast to northwest, and average annual crop referenced evaporatranspiration is 1 072. 7 mm with higher values in southeast and northwest parts and lower values in southwest and northeast parts.%应用修正后Vrsmarty水量平衡模型对黄土高原地区2001-2010年间的土壤水分变化规律进行模拟。该模型综合考虑了土壤质地、植被类型、蒸发、降水等因素。模拟结果表明:黄土高原地区平均土壤水含量年内呈"正弦"曲线的变化规律,6月份土壤水含量最低为36.9mm,随着雨季到来,10月达到最高为74.3mm,而后逐渐降低。土壤水变化趋势可分为西北和东南两个区。西北区降雨量少,蒸散量大,全年土壤水含量很低,为1~40mm;东南区受降雨和蒸散周期性的变化的影响,土壤水变化

  15. Spatial-temporal change and its driving forces of woodlands in the gully area of Longdong loess plateau over the last 30 years%近30年陇东黄土高原沟壑区林地时空变化及其驱动力分析

    Institute of Scientific and Technical Information of China (English)

    董晓峰; 马如兰; 庞国锦; 李波; 宋翔

    2011-01-01

    通过使用ERDAS和GIS分析工具对陇东地区1978年、1990年、2000年和2007年4期遥感影像进行人工目视解译,得出近30年来陇东黄土高原沟壑区林地的动态变化信息.结果表明,近30年陇东黄土高原沟壑区林地面积总体上呈增加趋势,表现为1978-1990年林地面积减少,1990-2000年林地面积增加,2000-2007年林地面积大幅增加.对林地变化的驱动力分析表明,人类活动是影响林地变化的主要因素;此外,气候变化、虫害等因素对林地时空变化也产生了影响.%Based on four remote sensing images(MSS in 1978 and TM in 1990, ETM+ in 2000 and TM in 2006), the spatial-temporal changes of woodlands inthe Longdong loess plateau area are analyzed with the support of ERDAS and GIS.Over the past 30 years the total area of the woodlands increased, during 1978 to 1990, patchy forest decreased heavily, during 1990 to 2000, patchy forest increased, from 2000 to 2007, forest land was rising substantially.The process responsible for woodlands change in the Longdong loess plateau area could be divided into natural and anthropogenic groups by analyzing the transition matrices.Human activities have been an important factor, at the same time climate change and insect damage also play important roles.

  16. 黄土高原中部秋季干湿的年际和年代际环流异常特征及与海温的多尺度相关性研究%Interannual and interdecadal atmospheric circulation anomalies of autumn dry/wet over the loess plateau and its multi-scalar correlation to SST

    Institute of Scientific and Technical Information of China (English)

    刘晓云; 王劲松; 李栋梁; 岳平; 李耀辉; 姚玉璧

    2013-01-01

    The ecological environment is vulnerable and extremely sensitive to climate change in the loess plateau. The interannual and interdecadal variations of dry/wet index are particularly obvious in this region. Up to now, the analisis of the dry/wet variation in the loess plateau has been basically understood during summer, but the autumn dry/wet evolution of the loess plateau and the atmospheric circulation characteristic are still laking in its knowledge. Based on the monthly mean rainfall and temperature of 589 China weather stations, the NCEP/NCAR reanalysis dataset and NOAA extended reconstructed sea surface temperature (SST) data from 1961 to 2010, using the EOF/REOF, bandpass filtering, wavelet technique and regression methods, the autumn dry/wet evolution of the loess plateau and the atmospheric circulation characteristic associated with them, and the multi-scale relationship between dry/wet index and SST were analyzed on the basis of classification of dry/wet over China region in autumn. The continuous wavelet transform shows that the autumn wet/dry index exists has∼4 a and 8 a period over the loess plateau, and the∼8 year oscillation from 1970-1990 is rather obvious. On the interannual scales, the atmospheric circulation anomalies of 500 hPa associated with the wet years exhibit a‘double-blocking’ in the mid-high latitude, and the westerly jet stream turns to be weakened and the jet axis moves to the north significantly. Japan-Okhotsk Sea is featured with anticyclone, and the east wind at the bottom of the anticyclone provides favorable moisture for the middle Loess plateau. On the interdecadal scales, the atmospheric circulation anomalies associated with the wet years show the negative geopotential height anomaly over East Asian, and the East Asian subtropical westerly jet stream of 200 hPa is weakened and moves north too. The vapour of the middle Loess plateau comes from two paths, one is the westerly water vapor transport in the middle latitude

  17. 黄土高原东缘晚全新世高精度高分辨率石笋古环境记录%An Absolute-dated High-resolution Palaeoclimate Record Between 4 400 and 150 a B.P. from Dragon Cave, Eastern Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    董进国; 沈川洲; 姜修洋

    2012-01-01

    The Dragon Cave (38°46"N, 113°16"E) is located at transition between semi-humid and semi-arid ar- eas in the middle temperature zone of China. Here, mean annual temperature is 8℃. Mean annual rainfall is 530mm and about 87% of annual precipitation falls in May-October. Dragon Cave is 〉600m long with an ele- vation of 1400m on the western slope of Taihang Mountain, near the eastern edge of Chinese Loess Plateau. Stalagmite L1 was collected 200m from the cave entrance in December 2010. It is about 200mm like a candle. A total of 5 sub-samples were measured by an inductively Multi-collection coupled plasma mass spectrometry on a Finnigan-NEPTUNE in the High-precision Mass Spectrometry and Environment Chang Laboratory, De- partment of Geosciences, National Taiwan University. The uncertainty of reported age is + 2σ. A high-resolution oxygen isotope profile established with 190 oxygen isotope data, provides a continuous history of East Asian summer monsoon intensity for the period of 4400-150a B.E (before AD1950). With a relatively stable boundary condition, we interpret the 8^18O of speleothem calcite as most indicative of the amount of summer monsoon precipitation, although temperature and other factors might have some minor im- pact. Comparison of the record with previous published contemporaneous China stalagmite records shows that all 6^18O records, characterized with increasing 8^18O and declining summer monsoon precipitation trends over the late Holoeene, generally follow insolation changes on millennial timescale. This long-term agreement sup- ports that the solar insolation is the primary factor driving Asian summer monsoon. An unusual abrupt weak summer monsoon at 2550-2000a B.E indicates a mega-drought event, supported by historic archives. The spec- tral analysis of δ^18O time series yields a solar activity-related 106-yr periodicity. However, comparing to a weak solar activity at 2.7ka B.P., a 100-200-yr lag of the cave-inferred mega

  18. Charge analysis on lightning discharges to the ground in Chinese inland plateau (close to Tibet

    Directory of Open Access Journals (Sweden)

    X. Qie

    Full Text Available Since the summer of 1996, scientists from China and Japan have conducted a joint observation of natural cloud-to-ground lightning discharges in the Zhongchuan area that is located close to Qinghai-Xizang (Tibet Plateau, China. It has been found that the long-duration of intracloud discharge processes, just before the first return stroke, lasted more than 120 ms for 85% of cloud-to-ground flashes in this area, with a mean duration of 189.7 ms and a maximum of 300 ms. We present the results of charge sources neutralized by four ground flashes and two intracloud discharge processes, just before the first return stroke, by using the data from a 5-site slow antenna network synchronized by GPS with 1 µs time resolution. The result shows that the altitudes of the neutralized negative charge for three negative ground flashes were between 2.7 to 5.4 km above the ground, while that of neutralized positive charges for one positive ground flash and one continuing current process were at about 2.0 km above the ground. The comparison with radar echo showed that the negative discharges initiated in the region greater than 20 dBZ or near the edge of the region with intense echoes greater than 40 dBZ, while positive discharge initiated in the weak echo region.

    Key words: Meterology and atmospheric dynamics (atmospheric electricity; convective processes; lightning

     

  19. [Effects of soil crusts on surface hydrology in the semiarid Loess hilly area].

    Science.gov (United States)

    Wei, Wei; Wen, Zhi; Chen, Li-Ding; Chen, Jin; Wu, Dong-Ping

    2012-11-01

    Soil crusts are distributed extensively in the Chinese Loess Plateau and play key roles in surface hydrological processes. In this study, a typical loess hilly region in Anjiagou catchment, Dingxi city, Gansu province was selected as the study region, and soil crusts in the catchment were investigated. Then, the hydrological effect of soil crusts was studied by using multi-sampling and hydrological monitoring experiments. Several key results were shown as follows. Firstly, compared with bared soil without crust cover, soil crusts can greatly reduce the bulk density, improve the porosity of soil, and raise the holding capacity of soil moisture which ranges from 1.4 to 1.9 times of that of bared soil. Secondly, the role of soil crust on rainfall interception was very significant. Moss crust was found to be strongest on rainfall interception, followed by synantectic crusts and lichen crusts. Bared soil without covering crusts was poorest in resisting rainfall splash. Thirdly, hydrological simulation experiments indicate that soil crusts play a certain positive role in promoting the water infiltration capacity, and the mean infiltration rate of the crusted soil was 2 times higher than that of the no-crust covered soils. While the accumulated infiltrated water amounts was also far higher than that of the bared soil.

  20. Physical mechanisms of plant roots affecting weathering and leaching of loess soil

    Institute of Scientific and Technical Information of China (English)

    LI Yong; ZHANG Qingwen; WAN Guojiang; HUANG Ronggui; PIAO Hechun; BAI Lingyu; LI Lu

    2006-01-01

    Plant roots have potential impacts on soil mineral weathering and leaching. Our objective is to understand the physical mechanisms of plant roots affecting weathering and leaching of loess soil. Root densities were measured through the method of a large-size dug profile, and transport fluxes of soil elements were determined using an undisturbed monolith soil infiltration device on the hilly and gully regions of the Chinese Loess Plateau. The results show that the improvement effects of soil environment by plant roots are mainly controlled by the density and weight of the fibrous roots with the diameters less than 1 mm. Plant roots have the stronger effects on soil physical properties than chemical properties. The principal components analysis (PCA) indicates that soil physical properties by plant roots account for 56.7% of variations in soil environment whereas soil chemical properties and pH contribute about 24.2% of the soil variations. The roles of plant roots in controlling soil weathering and leaching increased in the following order: infiltration enhancement > increase of bioactive substance > stabilization of soil structure. The effects of plant roots on soil mineral weathering and leaching can be quantified using the multiple regression models with the high prediction accuracies developed in this study.

  1. Comparative Study on Growth Process of Main Introduced Tree Species in the Middle Loess Plateau%黄土高原中部主要引进树种生长过程分析

    Institute of Scientific and Technical Information of China (English)

    刘广全; 孙克; 何正祥; 王鸿喆

    2012-01-01

    The introduced 16 species Austrian black pine,ponderosa pine,pinyon,scotch pine,Austrian pine and so on in the middle part of the Loess Plateau,the process of the average individual height growth can be grouped into two categories,the first type represented by Austrian pine,it grows rapidly in the period of seedlings,along with the ages its growth slows down and gradually stabilizes.The other type follows the growth pattern of "show-rapid-slow-stably drop down".Its average annual growth in height is 0.369±0.097m,Ponderosa pine and Austrian pine are the highest(0.535±0.052m),and china hemlock is the lowest(0.251±0.044m).The mean current annual growth in height of the 6 species is 0.387±0.104 m,the black pine is the maximum,the huashan pine is the minimum,the former is 2.63 times of the later.The variation of the average annual growth at breast height of the above-mentioned sixteen species is not appreciable,the highest of the ponderosa pine is 1.595±0.192 cm,the lowest is Wilson spruce with variation of 0.363±0.088cm.The average annual growth at breast height of the native tree species as bunge pine,huashan pine,golden larch,Wilson spruce,china hemlock and mogol scotch pine is 0.6048 cm,compared with the introduced tree species with 0.8488cm,which growth surpass the native tree species.Among the 16 introduced tree species with the mean current annual growth of 0.7056±0.2590 cm,the ponderosa pine is the maximum(1.249±0.350cm),and Wilson spruce is the minimum(0.376±0.241cm),the introduced tree species surpass the native tree species more than 50.0%.%本文对黄土高原中部引进的奥地利黑松、美国黄松、美人松、欧洲赤松、欧洲黑松等16个树种,林分个体树高平均生长量曲线分两种类型,以欧洲黑松为代表的第一种类型,苗期生长较快,随着年龄的增加,树高平均生长量趋于减慢且逐渐稳定,另外一种类型满足正常的"慢—快—缓慢—稳中有降"的生长规

  2. 黄土区次生植被恢复对土壤有机碳官能团的影响%Effect of revegetation on functional groups of soil organic carbon on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李婷; 赵世伟; 张扬; 马帅; 李晓晓

    2011-01-01

    Vegetation succession affects soil physical and chemical properties, including organic carbon functional group species, quantities, and structural changes. Changes in soil organic carbon (SOC) functional groups during the vegetation restoration process could reveal the processes governing changes in the composition and properties of humus. The study was on the Loess Plateau in the Ziwuling forest region of Shaanxi Province, where various stages of secondary forests have developed. At different phases of development, vegetation systems in this region have changed from pioneer herbage species, which initially colonized abandoned croplands, (Bothriochloa isehemum, Artenmisia giradii, Stipa bungeana, Artenmisia sacrornai, Spodiopogen sibiricus, Sophora flavecens,Themeda japonica, and Arundinella anomala) , to secondarv shrubs (Hippophae rhamnoides, Sophora viciifdia, and Ostrjopsis davidiana) , to an early forest community ( Populus davidiana, Betula platyphylla, and Platycladus orientalis with groups of trees and/or shrubs) , and finally to a Liaotungesis community forming the mature forest. The SOC content in the 0-40 cm soil layer increases significantly during the vegetation succession from abandoned cropland to mature Liaotungesis forest. The rate of increase in SOC is different during vegetation succession, and organic carbon functional groups varied among the different plant communities. Recent studies using synchrotron-based C( 1s) near-edge X-ray absorption fine structure (NEXAFS) have shown it to be an effective, non-invasive technique, which can be used to identify and fingerprint the complex structural characteristics of SOC. Consequently it can be used to investigate the impact of management on the composition and biogeochemical cycling of organic C at the molecular level in terrestrial ecosystems. This synchrotron radiation technology has rarely been used to study SOC structure in China before so we used it in this study with the objective of developing a

  3. Discovery of Ice-wedge Casts in the Northern Margin of Loess Plateau and Their Implications%黄土高原北缘中部末次冰期冰楔假型的发现及意义

    Institute of Scientific and Technical Information of China (English)

    王建勇; 张绪教; 何泽新; 赵秋晨; 何祥丽; 盛余应

    2015-01-01

    The ice-wedge casts were considered to be an important indicator on paleoenvironment.The clima-tostratigraphic information in them could implicate the geomorphic evolution.In this paper,the ice-wedge casts were described in detail,which were found in the lower terrace of Huanjiang river in the northern margin of Lo-ess Plateau.Through the field investigation and optically stimulated luminescence (OSL)dating,the age of sandy gravel deposited in the wedges was about (30.0 1 ±3.3 1 )ka B.P.,the fluvial silty sand layer on the up-per of the ice wedges was deposited about (28.64 ±3.13)ka B.P..This finding shows that a cold event oc-curred in the phase of Marine Oxygen Isotope Stage 3 (MIS 3)in the Last Glaciation.Also,the average ground temperature then was estimated to be 17.7 ℃ lower than the temperature nowadays.Besides,the discovery of the ice-wedge casts provided evidence for the phasic variation of the permafrost boundary during the Last Glaci-ation.In addition,the climatostratigraphic position of ice-wedge casts in the river terrace indicated that the flu-vial aggradation occurred slowly and even ended during the freezing period.When the climate was getting warm-er in (28.64 ±3.13)ka B.P.,the river started to undercut and the terrace was forming.This provided a basis for the formation mechanism of river terrace and showed the development of terrace was controlled by the chan-ging climate.%冰楔假型是反映古气候环境的重要标志,其蕴涵的气候地层信息对地貌演化过程具有重要的指示意义。通过对黄土高原北缘中部环江T1阶地上新发现的冰楔假型群特征的研究和光释光(OSL)测年,结果显示这些发育在冲积砂砾石中的冰楔假型的充填砂体的年代为(30.01±3.31)ka B.P.,其上部的河流相粉砂层的年代为(28.64±3.13)ka B.P.。冰楔假型的年代结果和发育地层揭示出晚更新世末次冰期的MIS 3阶段出现的一次寒冷波动事件,并根据冰

  4. Can the magnetic susceptibility record of Chinese Red Clay sequence be used for palaeomonsoon reconstructions?

    Science.gov (United States)

    Zhao, Guoyong; Han, Yan; Liu, Xiuming; Chang, Liao; Lü, Bin; Chen, Qu; Guo, Xuelian; Yan, Junhui; Yan, Jun

    2016-03-01

    Red Clay underlying the loess-palaeosol sequences on the Chinese Loess Plateau is an eolian deposit. There is a controversy over whether magnetic susceptibility (χ) variations in Red Clay sequence can be used as an indicator of summer palaeomonsoon intensity. This study investigates the magnetic mineralogy, magnetic concentration and magnetic grain size distribution of Jiaxian Red Clay with multimagnetic methods. Our results indicate that the magnetic properties of Jiaxian Red Clay are similar to those of the Quaternary loess-palaeosol sequences, and ultrafine ferrimagnetic grains produced during pedogenesis are responsible for an increase in susceptibility, therefore the χ enhancement mechanism of Red Clay is similar to that of the overlying loess-palaeosol sequences. This paper explores χ variations in the Red Clay sequence through spatial and temporal analysis. The susceptibility variation of six sites along a NNE to SSW transect correlate to palaeoclimatic cycles, so χ can be used to trace the summer palaeomonsoon intensity from a spatial perspective. However, a simple loess-derived calibration function cannot be used to quantitative reconstruct the palaeomonsoon intensity variations thought time. An adjusted calibration function for palaeosols from Red Clay sequence needs to be developed, so that χ can be used to quantitative reconstruct palaeomonsoon intensity. Further study is necessary to develop such a transfer function.

  5. Geochemical study of boron isotopes in the process of loess weathering

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Zhiqi; (

    2003-01-01

    ., Atmospheric carbon dioxide concentrations over the past 60 million years, Nature, 2000, 406: 695-699.[25]Liu Tungsheng, Loess and Environment (in Chinese), Beijing: Science Press, 1985, 191-302.[26]Gu Zhaoyan, Lal, D., Guo Zhengtang et al., 10Be geochemical characteristics of loess and redclay on the Loess Plateau, Quaternary Research (in Chinese), 2000, 20(5): 409-423.[27]Liu Tungsheng, Loess and Environment (in Chinese), Bejing: Science Pres, 1985, 1-481.[28]Zhao Zhiqi, Liu Congqiang, Xiao Yinkai, Separation of boron in acid-soluble phases in loess and paleosol deposits and its isotopic determination, Geochimica (in Chinese), 2000, 29(4): 351-357.[29]Xiao, Y. K., Beary, E. S., Fassett, J. D., An improved method for the high-precision isotopic measurement of boron by thermal ionization masses spectrometry, Int'l. J. Mass Spect. and Ion Proc., 1988, 85: 203-213.[30]Spivack, A. J., Edmond, J. M., Determination of boron isotope ratios by thermal ionization mass spectrometry of the dicesium metaborate cation, Anal. Chem., 1986, 58: 31-35.[31]Kiss, E., Ion-exchange separation and spectrophotometric determination of boron in geological materials, Anal. Chem. Acta, 1988, 211: 243-256.[32]Liu Tungsheng, Loess and Environment (in Chinese), Beijing: Science Press, 1985, 44-106.[33]Liu Congqiang, Zhao Zhiqi, Xiao Yinkai, Boron isotopic composition of loess and its implication for climatic tracing, Quaternary Research (in Chinese), 2000, 20(4): 394.[34]Taylor, S. R., Mclennan, S. M., Mcculloch, M. T., Geochemistry of loess, continental crustal composition and crustal model age, Geochim. Cosmochim. Acta, 1983, 47: 1897-1905.[35]Liu, C. Q., Masuda, A., Okada, A. et al., A geochemical study of loess and desert sand in northern China: Implications for continental crust weathering and composition, Chemical Geology, 1996, 106: 359-374.[36]Ishikawa, T., Nakamura, E., Boron isotope systematics of marine sediment, Earth Planet Sci. Lett., 1993, 117

  6. 陇中黄土高原自然植被下垫面陆面过程及其参数对降水波动的气候响应%Responses of the land-surface process and its parameters over the natural vegetation underlying surface of the middle of Gansu in loess plateau to precipitation fluctuation

    Institute of Scientific and Technical Information of China (English)

    张强; 李宏宇; 张立阳; 岳平; 史晋森

    2013-01-01

    作为气候敏感区和生态脆弱区,黄土高原地区的陆面物理过程受气候波动影响十分明显.目前,虽然对黄土高原特定气候条件下的陆面物理过程有了一定认识,但对其随气候波动的动态变化规律认识却非常有限.本文利用黄土高原陆面过程观测试验在陇中黄土高原榆中SACOL站5年多的观测资料,系统分析了该地区自然植被下垫面陆面水分收支和能量平衡及地表反照率、土壤热传导率和粗糙度长度等陆面过程参数对气候波动的响应规律,发现陇中黄土高原自然植被下垫面的陆面过程特征及其参数对降水的气候波动十分敏感,不仅对降水量波动响应显著,而且与降水性质也密切相关.土壤湿度并不完全随年总降水量波动,而是随有效降水量增加而增大;陆面水分收支和土壤水分收支也随有效降水量波动变化明显;近地层垂直感热平流通量随年总降水量增加而减弱,地表能量不平衡差额却随年总降水量增加而增大.夏半年平均反照率随有效降水量增加而减小,但全年平均地表反照率却受冬季积雪时数影响十分明显,而且随积雪时数增加而增大;土壤热传导率和粗糙度长度均随年有效降水量增加而增加.并且,降水量越小,陆面过程参数对降水波动的响应就越敏感.不过,陆面过程参数基本在荒漠气候平均值和农田气候平均值之间波动,并没有突破气候约束,能够用拟合关系来表示它们对降水因子波动的响应规律,这种动态参数化关系可用来改善以往数值模拟或微气象分析时由于使用非动态陆面过程参数所带来的误差.%The Loess Plateau is well known as a specific region sensitive to global climate change, and thus its land-surface process is significantly influenced by climatic fluctuation. Up to now, the land-surface physical process over the Loess Plateau has been basically understood under a

  7. Removal of radiation damage by subpopulations of plateau-phase Chinese hamster ovary cells

    International Nuclear Information System (INIS)

    Specific cellular radiobiology studies are often required to test aspects of the mathematical models developed in the Radiation Dosimetry program. These studies are designed to determine whether specific mathematical expressions, which characterize the expected effect of biochemical mechanisms on observable biological responses, are consistent with the behavior of selected cell lines. Since these tests place stringent requirements on the cellular system, special techniques and culture conditions are required to minimize biological variability. The use of specialized cell populations is providing data on the extent of repair following low doses, and on the changes in the types of damage that can be repaired as the cell progresses toward mitosis. The stationary-phase Chinese hamster ovary (CHO) cells are composed primarily of G(1)-phase cells (83%), with the remainder comprising both G(2) and S phases. Removal of radiation damage by cells was studied in split-dose experiments. To date, we have observed no significant differences in cellular repair rate. This suggests, therefore, that each of the repair processes found in stationary-phase cells is cell-age independent. However, cellular radiation sensitivity does change rapidly and considerably as the cells progress from one phase to the next through the cell cycle. Since the rate of damage removal appears invariant, the change in survival must reflect the efficiency of producing that damage. The experimental data suggest that production of one or another sort of damage probably dominates during specific phases of the cell cycle, while the capacity for removal of all types of damage remains relatively constant

  8. 黄土高原土壤剖面粒度异常层及相关因素的响应初步分析%Preliminary Analysis on Abnormal Granularity Layers of Soil Profile and the Response of Relative Factors in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    吕海波; 梁宗锁

    2011-01-01

    [目的]对黄土高原安塞县纸坊沟流域退耕林土壤1 m剖面有机碳含量、粒度、全氮含量、碳氮比、碳酸钙含量进行分析,研究以粒度反映下的土壤异常层理化性质变化,以及各土壤物理化学的响应.[方法]对黄土高原上3个样地各随机选择3个10 m×10 m的样方并分坡上、坡中、坡下分别挖掘3剖面,间隔10 cm采样,地表0~10 cm分0~5 cm和5~ 10 cm 2部分分别采样.每剖面采样11个,共99个样品,对其进行机碳含量、粒度、全氮含量、碳氮比、碳酸钙含量分析.[结果]3个样地土壤剖面存在a1、b1、b2、c1、c25个特征层,<0.02 mm粒径的土壤颗粒含量减少,>0.02 mm粒径的土壤颗粒含量增加,有机碳含量和C/N值(a1、b1、b2、c2)增加,但CaCO3含量上升趋势不明显.[结论]研究证明土壤特征层在黄土地区,尤其是侵蚀性黄土地区是普遍存在的,在现代土壤学和生态学研究领域应当给予重视.%[Objective]The paper was to analyze organic carbon content (SOC) , granularity, total nitrogen content (TN) , carbon-nitrogen ratio (C/N), calcium carbonate content (CaCO3) of 1cm soil profiles in returning forest in Zhifanggou watershed of Ansai County in Loess Plateau, so as to study the changes of physicochemical characters in abnormal layer of soil reflected with granularity, as well as the physical and chemical responses of soil. [ Method] Three sampling plots with the size of 10 m × 10 m were randomly selected in three sampling sites in Loess Plateau, three profiles in upper, middle and lower slope were excavated, and the samples were collected with interval of 10 cm; the surface layer with the depth of 0 - 10 cm was divided into two layers 0 -5 cm and 5-10 cm for sampling, respectively. 11 samples were collected in each profile with a total of 99 samples. Its organic carbon content, granularity, total nitrogen content, carbon-nitrogen ratio and CaCO3 content were analyzed. [ Result] The soil

  9. Evolution of the Ordos Plateau and environmental effects

    Institute of Scientific and Technical Information of China (English)

    YUE; LePing; LI; JianXing; ZHENG; GuoZhang; LI; ZhiPei

    2007-01-01

    Based on the analysis of temporary-spatial distribution, geomorphic position, contact relationship with underlying strata and grain size of red clay, we studied the formation and environmental background of red clay. During late Miocene-Pliocene, the Ordos Block finished the transformation from the basin to the plateau, which had an obvious environmental effect on the topography, indicated by the formation of highland undergoing wind erosion and lowland receiving red clay deposits. The red clay materials were sourced from dusts carried by wind energy and covered on the initial topography. Unlike Quaternary loess dust covering the overall the Loess Plateau, red clay deposited on the highland would be transported to the lowlands by wind and fluvial process. As a result, there was no continuous "Red Clay Plateau" in the Ordos region and red clay was only preserved in former lowlands. However, red clay was discontinuously distributed through the Loess Plateau and to some extent modified the initial topography. The differential uplift in interior plateau is indicated by the uplift of northern Baiyushan, central Ziwuling and southern Weibeibeishan. The Weibeibeishan Depression formed earlier and became the sedimentary center of red clay resulting in the thicker red clay deposits in Chaona, Lingtai and Xunyi. Since Quaternary the aridity in the northern plateau enhanced and accelerated loess accumulation caused the formation of the Loess Plateau. During the late Pleistocene the rapid uplift led to the enhancement of erosion. Especially after the cut-through of Sanme Lake by the Yellow River, the decline of base level caused the falling of ground water level and at the same time the increase of drainage density resulting in the enhancement of evaporation capacity, which enhanced the aridity tendency of aridity in the Loess Plateau region.

  10. Loess in China: A Good Archive of Climatic and Environmental Changes during the Quaternary

    Institute of Scientific and Technical Information of China (English)

    Wang Limeng; Lu Huayu

    2005-01-01

    @@ Quaternary scientists in China have significantly improved our knowledge of loess deposition as well as our understanding of paleoclimatic and paleoenvironmental changes over the past 2.5 million years. It is recognized that loess is of aeolian origin with loess forming dust continuously deposited. It is also believed that grain-size, magnetic susceptibility, carbon isotopes and fossil assemblages in loess deposits are good proxy indicators of paleomonsoon climate and paleovegetation changes over the past 2.5 million years. Chinese loess is regarded as one of the best terrestrial archives of climatic and environmental changes during the Quaternary.Further investigation of loess deposits and their records of climatic and environmental change aids understanding of climate change and gives scientific backing for the project of ecological and environmental restoration in northwest China.

  11. 陕北黄土高原乡村旅游资源及其营销策略比较优势%STUDY ON COMPARATIVE ADVANTAGES OF RURAL TOURISM RESOURCES AND MARKETING STRATEGY IN THE LOESS PLATEAU OF NORTHERN SHANXI

    Institute of Scientific and Technical Information of China (English)

    霍佳颖

    2016-01-01

    近年来,随着生活节奏的不断加快,人们休闲娱乐的时间变短,可以享受自然与人文风光的乡村旅游逐渐成为游客首选的旅游形式之一.为了满足游客多样化的需求,如何开发并合理利用乡村旅游资源成为乡村旅游发展的重要问题.陕北黄土高原拥有丰富的乡村旅游资源,其乡村旅游发展具有很大潜力.文章通过梳理乡村旅游的概念、 乡村旅游资源的内涵与分类方式,从自然旅游资源与人文旅游资源等2个方面分析了陕北黄土高原乡村旅游资源现状,总结出该地区的乡村旅游资源拥有资源数量较多、 类型多样,分布较为集中、 利于组合开发等比较优势,提出陕北黄土高原乡村旅游应采取打造陕北黄土高原乡村旅游品牌、 利用科技手段建立先进营销模式及开发个性化的旅游服务营销产品等营销策略,从而推动陕北黄土高原旅游产业的快速发展.%In recent years, with the accelerating pace of life, people's leisure time is short. Rural tourism has grad-ually become one of tourism forms that the tourists preferred,because it can make people enjoy natural and cultural landscape. In order to meet the diverse needs of tourists, how to develop and make use of rural tourism resources becomes an important issue of rural tourism development. The Loess Plateau of Northern Shanxi has rich rural tourism resources and great potential in rural tourism development. Through combing rural tourism concept and con-notation of rural tourism resources and classification, this paper analyzed the current situation in Loess Plateau of Northern Shanxi Province rural tourism resources from two aspects, i. e. , natural tourism resources and cultural tourism resources, summed up the comparative advantages of rural tourism resources which had a large number of resources and diverse types, more concentrateddistribution, and combination development and so on. Finally, it put forward some

  12. Origin of the Red Earth sequence on the northeastern Tibetan Plateau and its implications for regional aridity since the middle Miocene

    Institute of Scientific and Technical Information of China (English)

    WANG; Xianyan; LU; Huayu; JI; Junfeg; WANG; Xiaoyong; ZHAO; Jingbo; HUANG; Baochun; LI; Zhen

    2006-01-01

    The Red Earth deposit around Xining, northeastern Tibetan Plateau, has been studied in terms of soil micro-structure, grain-size distribution, major- and trace-element chemistry and magnetostratigraphy. Field investigations indicate that the Red Earth sequence consists of 25 visually definable yellow-brown and weakly-developed soils interbedded with reddish strongly-developed soils, and has a similar structure to the aeolian Red Clay deposit on the Chinese Loess Plateau. Grain-size analysis shows that the Red Earth deposit is very fine-grained with a negligible sand fraction (>63μm). Thin-section observations under light microscopy show that the deposit has a clayey texture and the coarse fraction (>10μm) mainly consists of quartz, feldspar and micas. Pyroxene and hornblende were also observed. This mineralogical composition of the coarse fraction is similar to that of the Quaternary loess. In addition, all of the mineral grains are semi angular semi-angular and are generally finer than 63μm. There is a good agreement between the major and minor trace element chemistry of loess-soil units and the Red Earth deposit. The REE distributions of the loess-soil and the Red Earth deposit are similar in shape, with enriched LREE and fairly flat HREE profiles and a clear negative Eu anomaly. The geochemical characteristics of the Red Earth deposit are also identical to those of upper continental crust, thus indicating a wind-blown origin.Magnetostratigraphic investigation shows that onset of the Red Earth deposition predates 11.4 Ma BP (13.6 Ma at a nearby site). The distribution of the reported Miocene aeolian loess at Qin'an of the Loess Plateau is still unknown. Our results indicate that this aeolian deposit had extended to the northeastern Tibetan Plateau by at least the middle Miocene. The similarity of the element geochemistry between the Red Earth deposit and the overlying loess shows that they may have similar sources and dynamic transport system, and may indicate

  13. Simulation of the erosion and drainage development of Loess surface based on GIS

    Science.gov (United States)

    Wang, Chun; Tang, Guoan; Ge, Shanshan; Li, Zhanbin; Zhou, Jieyu

    2006-10-01

    The research probes into the temporal-spatial process of drainage development of Loess Plateau on the basis of a carefully designed experiment. In the experiment, the development of a simulated loess watershed is tested under the condition of lab-simulated rainfall. A close-range photogrammetry survey is employed to establish a series of high precision and resolution DEM (Digit Elevation Model) of the simulated loess surface. Based on the established DEM, the erosion loss, the slope distribution, the topographic index , the gully-brink, and the drainage networks are all derived and discussed through comparison analysis and experimental validation. All the efforts aim at revealing the process and mechanism of erosion and drainage development of loess surface .This study demonstrates: 1) the stimulation result can effectively reflect the truth if those experimental conditions, i.e. loess soil structure, simulated rainfall, are adjusted in accord with true situation; 2) the remarkable character of the erosion and drainage up-growth of loess surface include the drainage traced to the source, the increased of the drainage's density, the enlarged of gully, the durative variety of multiple terrain factor's mean value and its distribution, such as slope and topographic index; 3) The slope spectrum is the more felicitous terrain factor for depicting the erosion and drainage development of loess surface, including the rule of erosion and evolution process. It is the new way and mean for studying the loess physiognomy.

  14. Characterization of Soil Microbial Community Function and Structure in Rhizosphere of Typical Tree Species and the Meaning for Environmental Indication in the Loess Plateau%黄土高原典型林木根际土壤微生物群落结构与功能特征及其环境指示意义

    Institute of Scientific and Technical Information of China (English)

    张海涵; 唐明; 陈辉

    2009-01-01

    Determination of the soil microbial community structure in rhizosphere of typical tree species in the Loess Plateau can be of great theoretical significance for correctly assessing the characteristics of soil ecological rehabilitation of the Loess Plateau. In this study, spore density analysis, microbial cultivation and BIOLOG were employed to evaluate the AMF spore density and soil microbial community diversity under four tree species with vesicular-arbuscular mycorrhizae in ecological rehabilitation area of the Loess Plateau, north Shaanxi Province. The results show that the different tree species differed significantly in both soil microbial number and microbial functional diversity, AMF spore density of Hippophae rhamnoides soil is 2.24 times than that of the Robinia pseudoacacia soil, and the rank as following order: Hippophae rhamnoides > Sophora viciifolia > Caragana mwrophjlla > Robinia pseudoacacia . The statistical significant are detected in the bacteria and actinomyces numbers, however, there is no statistical significance in fungi number among the treatments. The principle component analyses indicates that scatter of Caragana microphylla and Hippophae rhamnoides axe smaller than that of Sophora viciifolia and Robinia pseudoacacia, these results suggest that the soil community structure strongly varied among the different tree species. Numbers of carbon sources related to the first two components are 14 and 8. Correlation analysis shows that the AMF spore density appeared extremely significantly and positively correlated with the number of bacteria, and the metabolic of amino acids, amines and aromatic compounds, respectively . Moreover, AMF spore density positively correlated with the average well color development (AWCD) , nevertheless, no correlations are found among AMF spore density, carboxylic acids, carbohydrates and polymers. These results suggest that AMF spore density is shown to be an important environmental biology parameter used in

  15. Molecular fossil and paleovegetation records of paleosol S4 and adjacent