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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. A first paleomagnetic and rock magnetic investigation of calcareous nodules from the Chinese Loess Plateau

    Science.gov (United States)

    Yang, T.; Hyodo, M.; Yang, Z.; Sun, Z.

    2005-01-01

    A detailed paleomagnetic and rock magnetic investigation was carried out on calcareous nodule layers embed-ded in the loess-paleosol sequences near Baoji city, southern Chinese Loess Plateau. The anisotropy of low-field magnetic susceptibility confirms that calcareous nodules retain the primary sedimentary fabric of original de-posits. Rock magnetic properties demonstrate that calcareous nodules have the same mineralogy and grain sizes as loess-paleosol deposits. Characteristic remanent magnetizations of calcareous nodules have directions consis-tent with those of adjacent loess and paleosol deposits. The Punaruu event, previously found from loess deposits in the upper part of loess unit L13 in Weinan, southern Chinese Loess Plateau, is observed at the corresponding stratigraphic level in the calcareous nodule layer. These observations indicate that the calcareous nodule layers preserve primary remanent magnetizations of original deposits before calcification, and that they can contribute to paleomagnetic studies in 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. Palaeoclimatic records of the loess/palaeosol sequences of the Chinese Loess Plateau

    Science.gov (United States)

    Maher, Barbara A.

    2016-12-01

    Whether during past climate stages or into a progressively warming world, changes in precipitation constitute a key component of climatic change. Quantitative proxies for palaeo-precipitation are relatively rare. The magnetic properties of the windblown loess units and interbedded palaeosols of the famous Chinese Loess Plateau provide key palaeo-precipitation data for this populous, monsoon-dominated region. The loess/palaeosol sediments record rainfall totals, directly complementing the oxygen isotope records of Chinese speleothems. These isotopic records predominantly reflect moisture source, and hence large-scale atmospheric circulation changes. The two major Asian monsoon systems appear to display antiphase behaviour. Dominance of the Indian summer monsoon system seems associated with minimum precession/maximum northern hemisphere summer heating; dominance of the East Asian summer monsoons with maximum precession. At ∼2.8 Ma, more intense development of the East Asian winter monsoon initiated major increases in dust deposition rates, and formation of relatively unweathered loess layers. Glacial-stage loess units then interleaved with interglacial/interstadial-stage palaeosols throughout the Quaternary period. Decoupling of the loess/palaeosol rainfall records from the Chinese cave records of moisture source shows that the Indian and East Asian monsoon winds were continuously driven by precessional forcing while summer monsoonal rainfall was greatly suppressed during cool, glacial stages. The timing of these East Asian climatic transitions, the subsequent intensification of northern hemisphere glaciations, and the association between monsoon circulation changes and North Atlantic temperatures, indicates a possibly leading global role for these monsoonal changes via alterations in the poleward distribution of heat and moisture.

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

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    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.

  9. 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.

  10. 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.

  11. 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.

  12. Non-Magnetic Factors Affecting Magnetic Susceptibility of the Loess-Paleosol Sequences in the Chinese Loess Plateau

    Science.gov (United States)

    Wang, H.; Feng, Z.

    2009-12-01

    Several different proposals have been adopted to explain the linkage between the magnetic susceptibility of loess-paleosol sequences and the associated past climate. First, the intensity of dustfall controlled the variation in the susceptibility. Second, the degree of pedogenesis controlled the variation. A third proposal states that the susceptibility signal is a result of the competing processes between pedogenic enhancement and detrital inheritance. This paper examines the acceptability as the summer monsoon proxy from nonmagnetic perspectives. Several conclusions can be drawn from our data. First, clay translocation within the Last Interglacial paleosol S1 profiles must have moved some of the magnetic minerals downward so that the susceptibility reflects only the post-translocation distribution of the magnetic susceptibility-producing minerals. Second, the best-developed paleosol S1S3 (equivalent to MIS 5e) at most of the sections studied is not well expressed by the magnetic susceptibility because this paleosol developed in underlying coarse loess (L2) and coarse textures tend to lower the susceptibility. Third, carbonate concentration is negatively correlated with the magnetic susceptibility or suppresses the magnetic susceptibility peak when the susceptibility enhancement exceeds the carbonate dilution effect. It should be stressed that the susceptibility signal and its contributors in eolian sequences can be site- and time-dependent within the Chinese Loess Plateau. A stronger eolian component northwestward and a stronger pedogenic component southeastward are the general trends, but the trends can be complicated by those site- and time-dependent factors. Therefore, a more comprehensive model is needed to more precisely address the relationship between the paleoclimate and the proxy.

  13. 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...

  14. Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    孙东怀; 刘东生; 陈明扬; 安芷生; John Shaw

    1997-01-01

    Two Red Clay profiles near Xi’ an and Xifeng were investigated in an attempt to determine magne-tostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma, and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5-2.5 Ma. Stepwise increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan Plateau, sola

  15. 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.

  16. 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.

  17. 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)

    CHEN XiuLing; FANG XiaoMin; AN ZhiSheng; HAN WenXia; WANG Xin; BAI Yan; HONG Ye

    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.

  18. 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.

  19. 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.

  20. 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.

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

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    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.

  2. 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

  3. 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

  4. Magnetic parameter variations in the Chaona loess/paleosol sequences in the central Chinese Loess Plateau, and their significance for the middle Pleistocene climate transition

    Science.gov (United States)

    Song, Yougui; Fang, Xiaomin; King, John W.; Li, Jijun; Naoto, Ishikawa; An, Zhisheng

    2014-05-01

    A high-resolution rock magnetic investigation was performed on the Chaona Quaternary loess/paleosol sequences in the Central Chinese Loess Plateau. Based on a newly developed independent unturned time scale and magnetic records, we reconstructed the history of the East Asia monsoons during the last 3 Ma and explored the middle Pleistocene climate transition (MPT). Rock magnetic results show that the loess layers are characterized by relatively high coercivity and remanent coercivity, lower magnetic susceptibility (MS), and that the paleosol layers are characterized by relatively high MS, saturation magnetization and remanent saturation magnetization. Spectrum analyses indicate that there are various periods in addition to orbital periodicities. According to the onset and stable appearance of 100 kyr period, we consider that the MPT recorded in this section began at ~ 1.26 Ma and was completed by ~ 0.53 Ma, which differs from previous investigations based on orbitally tuned time scales. The forcing mechanism for the MPT was more complicated than just the orbital forcing. We conclude that the rapid uplift of the Tibetan Plateau may have played an important role in the shift of periodicities during the middle Pleistocene.

  5. 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

  6. Holocene vegetation cover in Qin'an area of western Chinese Loess Plateau revealed by n-alkane

    Institute of Scientific and Technical Information of China (English)

    ZHONG YanXia; CHEN FaHu; AN ChengBang; XIE ShuCheng; HUANG XianYu

    2007-01-01

    Previous studies have found that wetlands prevailed in western Chinese Loess Plateau and pine pollen could reach up to 80% in Qin'an area of the plateau during middle Holocene.It was then deduced that forest vegetation covered Qin'an area in a warm and wet climate during middle Holocene.The proxies of molecule biomarkers from two Holocene sections,a swamp-alluvial loess section and a typical loess-paleosol section are used to reconstruct regional vegetation history.It is found that the heavy-molecular-weight(HMW)homologues of the n-alkanes in all samples exhibit a pronounced odd-over-even predominance,maximizing at C31 and the abundance of the nC27-alkanes is the lowest in nC27,nC29,nC31,i.e.C27<C29<C31,a typical grass n-alkanes model.The results are the same as those of model surface soil samples under grass cover but different from both forest cover and modern pine leaves,which yield preferentially nC29-alkanes peak.It could be jnferred that the area was dominated by grass cover but not forest cover during whole Holocene epoch.The study shows that combining both molecule biomarkers and pollen analysis can avoid the disadvantage of pollen analysis in reconstruction of regional vegetation cover.

  7. Detection of Catchment-Scale Gully-Affected Areas Using Unmanned Aerial Vehicle (UAV on the Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    Kai Liu

    2016-12-01

    Full Text Available The Chinese Loess Plateau suffers from serious gully erosion induced by natural and human causes. Gully-affected areas detection is the basic work in this region for gully erosion assessment and monitoring. For the first time, an unmanned aerial vehicle (UAV was applied to extract gully features in this region. Two typical catchments in Changwu and Ansai were selected to represent loess tableland and loess hilly regions, respectively. A high-powered quadrocopter (md4-1000 equipped with a non-metric camera was used for image acquisition. InPho and MapMatrix were applied for semi-automatic workflow including aerial triangulation and model generation. Based on the stereo-imaging and the ground control points, the highly detailed digital elevation models (DEMs and ortho-mosaics were generated. Subsequently, an object-based approach combined with the random forest classifier was designed to detect gully-affected areas. Two experiments were conducted to investigate the influences of segmentation strategy and feature selection. Results showed that vertical and horizontal root-mean-square errors were below 0.5 and 0.2 m, respectively, which were ideal for the Loess Plateau region. The overall extraction accuracy in Changwu and Ansai achieved was 84.62% and 86.46%, respectively, which indicated the potential of the proposed workflow for extracting gully features. This study demonstrated that UAV can bridge the gap between field measurement and satellite-based remote sensing, obtaining a balance in resolution and efficiency for catchment-scale gully erosion research.

  8. 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.

  9. Estimation of soil loss by water erosion in the Chinese Loess Plateau using Universal Soil Loss Equation and GRACE

    Science.gov (United States)

    Schnitzer, S.; Seitz, F.; Eicker, A.; Güntner, A.; Wattenbach, M.; Menzel, A.

    2013-06-01

    For the estimation of soil loss by erosion in the strongly affected Chinese Loess Plateau we applied the Universal Soil Loss Equation (USLE) using a number of input data sets (monthly precipitation, soil types, digital elevation model, land cover and soil conservation measures). Calculations were performed in ArcGIS and SAGA. The large-scale soil erosion in the Loess Plateau results in a strong non-hydrological mass change. In order to investigate whether the resulting mass change from USLE may be validated by the gravity field satellite mission GRACE (Gravity Recovery and Climate Experiment), we processed different GRACE level-2 products (ITG, GFZ and CSR). The mass variations estimated in the GRACE trend were relatively close to the observed sediment yield data of the Yellow River. However, the soil losses resulting from two USLE parameterizations were comparatively high since USLE does not consider the sediment delivery ratio. Most eroded soil stays in the study area and only a fraction is exported by the Yellow River. Thus, the resultant mass loss appears to be too small to be resolved by GRACE.

  10. 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.

  11. A wavelet analysis of the relationship between Loess Plateau erosion and sunspots

    NARCIS (Netherlands)

    Gao, P.; Geissen, V.; Temme, A.J.A.M.; Ritsema, C.J.; Mu, X.; Wang, F.

    2014-01-01

    The Chinese Loess Plateau is one of the most rapidly eroding regions in the world. The purpose of this study is to find out to which extent soil erosion on the Loess Plateau is driven by sunspot activity. We analyzed the relation between annual sediment discharge (from 1919 to 2010) from the Loess P

  12. [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.

  13. 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.

  14. The occurrence of a grassy vegetation over the Chinese Loess Plateau since the last interglacier: the molecular fossil record

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A series of allochthonous and autochthonous molecular fossils were identified from the Holocene paleosol (S0), Malan Loess (L1) and the top Lishi Loess (S1) in Jiuzhoutai loess profile in Lanzhou through the GC/MS analysis. The allochthonous molecules were transported into the Plateau by the loess grains whilst the autochthonous molecules were related to the input of the local paleo-vegetation and could be used to reconstruct the paleo-vegetation. The distribution of the autochthonous n-alkanes was discriminated from the overlapping allochthonous homologues characterized by the CPI value of unity. The dominance of autochthonous C31 n-alkane implicates the occurrence of a grassy vegetation over the Loess Plateau since the last interglacier. The warmest period of the Holocene, though dominated by grass, was additionally characterized by the relatively increased abundance of C27 n-alkane indicative of woody plants. The desert plants might occur during the last glacier. The molecular fossil record is not contradictory with the recent phytolith data, denying the occurrence of a forest over the Plateau since the last interglacier. These data from the loess molecular stratigraphy indicate the importance of the discrimination of the autochthonous molecules from the allochthonous compounds.

  15. 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.

  16. 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

  17. Accumulation and erosion of aeolian sediments in the northeastern Qinghai-Tibetan Plateau and implications for provenance to the Chinese Loess Plateau

    Science.gov (United States)

    Liu, Xiang-Jun; Xiao, Guoqiao; E, Chongyi; Li, Xiangzhong; Lai, Zhongping; Yu, Lupeng; Wang, Zhong

    2017-03-01

    The northern and northeastern Qinghai-Tibetan Plateau (QTP) is regarded as one important source region of the Chinese Loess Plateau (CLP). However, how the fine grain sediments in this region were transported to the CLP remains debatable. In this study, we dated aeolian sediments, alluviums, beach sediments, and sand wedges in the northeastern QTP using optical dating, combined with previously reported ages, explored the aeolian sediment deposition patterns in this region. The dating results shown that aeolian sediments mainly accumulated during the marine isotope stage (MIS) 3 and since the last deglaciation, alluvial sediments mainly deposited during the middle to late MIS 3 (between ∼40 ka and 22 ka), and sand wedges formed during the MIS 4 and MIS 2 cold intervals. Based on the sedimentary stratigraphic characteristics and existing optical dating chronologies, we propose that fine grain sediments in the northern and northeastern QTP were eroded and carried to the CLP by westerly wind during last glacial and stadial cold stages. However, during last interglacial and interstadial warm stages, aeolian sediments deflated from western barren lands and deserts were mainly trapped in the northeastern QTP, and some were transported to the Alax arid zone or Yinchuan-Hetao plain by rivers that flow out of QTP, then transported to the CLP by northwesterly Asian winter monsoon (AWM). This cold stage westerly wind transport, warm stage rivers plus AWM transport pattern has existed at least since the late middle Pleistocene.

  18. 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.

  19. Drought variation of western Chinese Loess Plateau since 1568 and its linkages with droughts in western North America

    Science.gov (United States)

    Fang, Keyan; Guo, Zhengtang; Chen, Deliang; Linderholm, Hans W.; Li, Jinbao; Zhou, Feifei; Guo, Guoyang; Dong, Zhipeng; Li, Yingjun

    2017-03-01

    Understanding long-term drought variations in the past can help to evaluate ongoing and future hydroclimate change in the arid western Chinese Loess Plateau (WCLP), a region with increasing demand for water resources due to the increasing population and socioeconomic activities. Here we present a new tree-ring chronology inform the WCLP, which shows coherent interannual variations with tree-ring chronologies from 7 neighboring areas across the WCLP, suggesting a common regional climate control over tree growth. However, considerable differences are observed among their interdecadal variations, which are likely due to growth disturbances at interdecadal timescales. To deal with this issue, we use a frequency based method to develop a composite tree-ring chronology from 401 tree-ring series from these 8 sites, which shows more pronounced interdecadal variability than a chronology developed using traditional methods. The composite tree-ring chronology is used to reconstruct the annual precipitation from previous August to current July from 1568 to 2012, extending about 50 years longer than the previous longest tree-ring reconstruction from the region. The driest epoch of our reconstruction is found in the 1920s-1930s, which matches well with droughts recorded in historical documents. Over the past four centuries, a strong resemblance between drought variability in the WCLP and western North America (WNA) is evident on multidecadal timescales, but this relationship breaks down on timescales shorter than about 50 years.

  20. 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.

  1. 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...

  2. Violet stimulated luminescence dating of quartz from Luochuan (Chinese loess plateau)

    NARCIS (Netherlands)

    Ankjærgaard, C.; Guralnik, B.; Buylaert, J.P.; Reimann, T.; Yi, S.W.; Wallinga, J.

    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)

  3. Chronology and the upper dating limit for loess samples from Luochuan section in the Chinese Loess Plateau using quartz OSL SAR protocol

    Science.gov (United States)

    Lai, ZhongPing

    2010-01-01

    Luminescence dating of loess older than 100 ka has long been a challenge. It has been recently reported that, using optically stimulated luminescence (OSL) of fine-grained quartz (4-11 μm) extracted from loess, the range of luminescence dating could be pushed to ˜0.6 Ma with OSL ages being in agreement with independent ages [Watanuki, T., Murray, A.S., Tsukamoto, S., 2005. Quartz and polymineral luminescence dating of Japanese loess over the last 0.6 Ma: comparison with an independent chronology. Earth and Planetary Science Letters 240, 774-789]. The aim of this study is to provide a luminescence chronology (20 samples) for the standard Luochuan loess section, and to further examine the upper limit of quartz OSL dating for Chinese loess. The growth curve does not saturate at 700 Gy, and should allow reliable equivalent dose ( De) determination up to at least 400 Gy. However, when compared with independent chronological control, the De that could be treated as reliable is less than ˜230 Gy (corresponding to ˜70 ka in age for Chinese loess), and the De larger than ˜230 Gy should be underestimated. Ages for samples from the lower part of palaeosol S1 are severely underestimated, with the maximum age of 95 ka for a sample from the bottom of this palaeosol, much younger than the expected age of ˜128 ka. The maximum De obtained for sample L9/M, collected from loess layer L9 which is below the Matuyama-Brunhes (B/M) boundary whose age is ˜780 ka, is only 403 Gy which corresponds to an age of 107 ka. The cause of underestimation is not yet clear. The previous results by Watunuki et al. (2005) on the extension of OSL dating of loess to 0.6 Ma is not confirmed. When evaluating the validity of OSL ages in S1, another possibility is to question the already established chronological frame for Luochuan section, which is based on the hypothesis of continuous dust deposition. The assumption of an erosion hiatus between L2 and S1 could make the OSL ages look reasonable

  4. 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.

  5. 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.

  6. Distribution of Palygorskite in the Lingtai Profile of Chinese Loess Plateau: Its Paleoclimatic Implications

    Institute of Scientific and Technical Information of China (English)

    XIE Qiaoqin; CHEN Tianhu; CHEN Jun; JI Junfeng; XU Huifang; XU Xiaochun

    2008-01-01

    Palygorskite is a typical indicator mineral of the arid and strong evaporation environment.Distribution of palygorskite in loess-red clay sequences may act as an important indicator for reconstruction of the paleoenvironment and paleoclimate. In this paper, field emission scanningelectron microscope and high-resolution transmission electron microscope observations on the redclay-loess-paleosoi of the Renjiapo profile at Lingtai, Gansu Province indicate that palygorskite occurswidely in red clay sequences formed before 3.6 Ma, but no occurrence has been found in eolian sediments since 3.2 Ma. Micromorphological features and microstructure of palygorskite show that it is an autogenic mineral formed during pedogenesis, and transformed from illite-montmorilionite under the pore water action. In the Lingtai profile, the disappearance horizon of palygorskite is consistent with those of increasing magnetic susceptibility, dust flux and depositional rate. The distribution of palygorskite in the profile indicates that the interval of around 3.6 Ma was an important transformation period of the East Asian paleomonsoon, when changes took place in the East Asia paleoclimate pattern, I.e. A high-frequency strong fluctuation alternative evolution of the environment.Therefore, palygorskite is a key indicator mineral of the East Asian paleomonsoon evolution of that time.

  7. 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.

  8. Vegetation cover and topography rather than human disturbance control gully density and sediment production on the Chinese Loess Plateau

    Science.gov (United States)

    Zhao, Jianlin; Vanmaercke, Matthias; Chen, Longqian; Govers, Gerard

    2016-12-01

    The factors controlling topsoil erosion rates on the Chinese Loess Plateau (CLP) are currently relatively well understood and topsoil erosion rates can now be relatively accurately estimated. 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 and spatial distribution on the CLP are less well understood. In this study we quantified the contribution of non-topsoil erosion to total sediment production on the CLP and investigated which factors control spatial and temporal variations in non-topsoil erosion. We estimated non-topsoil erosion rates (ENT) by comparing the measured average sediment yields of 46 gauged catchments for the 1950-1970 period, when soil conservation measures were nearly absent in the area, with predicted topsoil erosion rates (using a recently developed empirical model). In addition, gully density was estimated in each catchment using Google Earth data. Our results showed that the area-weighted average catchment erosion rate (E) and ENT were 58.60 ± 51.80 and 48.68 ± 49.78 t ha- 1 yr- 1 respectively for the studied catchments. The sediment contribution of non-topsoil erosion to total sediment production ranged between ca. 0 and 97% with a mean of 70 ± 25%. Both E and ENT were significantly correlated to longitudinal 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 rainfall erosivity. Importantly, gully density was not only related to overall slope steepness, but also to the longitudinal slope of the river network and the hypsometric integral, suggesting that not only land cover disturbance but also tectonic uplift controls gully density and erosion rates. The

  9. 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.

  10. 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.

  11. New insights into the paleoclimatic interpretation of the temperature dependence of the magnetic susceptibility and magnetization of Mid-Late Pleistocene loess/palaeosols in Central Asia and the Chinese Loess Plateau

    Science.gov (United States)

    Zan, Jinbo; Fang, Xiaomin; Yan, Maodu; Li, Bingshuai

    2016-11-01

    The temperature dependence of magnetic susceptibility (χ-T curves) and magnetization (M-T curves) has been used as a routine rock magnetic tool to characterize the magnetic mineralogy and magnetic granulometry of Chinese loess/palaeosols. However, paleoclimatic interpretation of these thermomagnetic analyses remains controversial. In the present study, total organic carbon (TOC), thermomagnetic and low-temperature magnetic experiments on Mid-Late Pleistocene loess/palaeosols in Central Asia and the Chinese Loess Plateau (CLP) have been conducted. We found that the M (T) cooling curves at room temperature were mostly lower than the corresponding heating curves, whereas for the χ (T) analyses the cooling curves at room temperature were always much higher than the heating curves. Low-temperature magnetic measurements demonstrated that a large amount of superparamagnetic ferrimagnetic particles were produced during the thermal treatment and resulted in the aforementioned differences. This finding further indicated that the use of the M - T curves to estimate the relative content of maghemite in the loess/paleosols from the CLP was problematic. In addition, a positive correlation exists between the TOC and the frequency-dependent susceptibility (χFD) in the CLP, suggesting that stronger pedogenesis would result in the simultaneous increase in the content of both maghemite and organic matter. Consequently, the parameters △χ1 (representing the relative content of pedogenic maghemite), △χ2 ([χph-χ] +△χ1) and χph (related to the organic matter concentration), which can be calculated from the χ - T analyses, can potentially be used as new indicators of pedogenesis and paleoclimate in Central Asia and the CLP.

  12. New insights into the palaeoclimatic interpretation of the temperature dependence of the magnetic susceptibility and magnetization of Mid-Late Pleistocene loess/palaeosols in Central Asia and the Chinese Loess Plateau

    Science.gov (United States)

    Zan, Jinbo; Fang, Xiaomin; Yan, Maodu; Li, Bingshuai

    2017-02-01

    The temperature dependence of magnetic susceptibility (χ-T curves) and magnetization (M-T curves) has been used as a routine rock magnetic tool to characterize the magnetic mineralogy and magnetic granulometry of Chinese loess/palaeosols. However, palaeoclimatic interpretation of these thermomagnetic analyses remains controversial. In the present study, total organic carbon (TOC), thermomagnetic and low-temperature magnetic experiments on Mid-Late Pleistocene loess/palaeosols in Central Asia and the Chinese Loess Plateau (CLP) have been conducted. We found that the M (T) cooling curves at room temperature were mostly lower than the corresponding heating curves, whereas for the χ (T) analyses the cooling curves at room temperature were always much higher than the heating curves. Low-temperature magnetic measurements demonstrated that a large amount of superparamagnetic ferrimagnetic particles were produced during the thermal treatment and resulted in the aforementioned differences. This finding further indicated that the use of the M-T curves to estimate the relative content of maghemite in the loess/palaeosols from the CLP was problematic. In addition, a positive correlation exists between the TOC and the frequency-dependent susceptibility (χFD) in the CLP, suggesting that stronger pedogenesis would result in the simultaneous increase in the content of both maghemite and organic matter. Consequently, the parameters ▵χ1 (representing the relative content of pedogenic maghemite), ▵χ2 ([χph - χ] +▵χ1) and χph (related to the organic matter concentration), which can be calculated from the χ-T analyses, can potentially be used as new indicators of pedogenesis and palaeoclimate in Central Asia and the CLP.

  13. 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.

  14. Application of a modified distributed-dynamic erosion and sediment yield model in a typical watershed of a hilly and gully region, Chinese Loess Plateau

    Science.gov (United States)

    Wu, Lei; Liu, Xia; Ma, Xiaoyi

    2016-11-01

    Soil erosion not only results in the destruction of land resources and the decline of soil fertility, but also contributes to river channel sedimentation. In order to explore the spatiotemporal evolution of erosion and sediment yield before and after returning farmland in a typical watershed of the hilly and gully region (Chinese Loess Plateau), a distributed-dynamic model of sediment yield based on the Chinese Soil Loss Equation (CSLE) was established and modified to assess the effects of hydrological factors and human activities on erosion and sediment yield between 1995 and 2013. Results indicate that (1) the modified model has the characteristics of a simple algorithm, high accuracy, wide practicability and easy expansion, and can be applied to predict erosion and sediment yield in the study area, (2) soil erosion gradations are closely related to the spatial distribution of rainfall erosivity and land use patterns, and the current soil and water conservation measures are not efficient for high rainfall intensities, and (3) the average sediment yield rate before and after model modification in the most recent 5 years (in addition to 2013) is 4574.62 and 1696.1 Mg km-2, respectively, decreasing by about 35.4 and 78.2 % when compared to the early governance (1995-1998). However, in July 2013 the once-in-a-century storm is the most important reason for maximum sediment yield. Results may provide an effective and scientific basis for soil and water conservation planning and ecological construction of the hilly and gully region, Chinese Loess Plateau.

  15. Environmental significance of mineral weathering and pedogenesis of loess on the southernmost Loess Plateau, China

    NARCIS (Netherlands)

    Huang, C.; Zhao, W.; Liu, F.; Tan, W.F.; Koopal, L.K.

    2011-01-01

    Soils derived from the Loess Plateau of China are regionally important and expression of the soil properties along the soil profile may be directly related to climate changes. The objective of this research was to analyze the clay mineral transformation of loess from the southernmost Loess Plateau,

  16. 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

  17. 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

  18. 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

  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. 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

    Luminescence dating of loess accumulation in China has raised questions over disturbance and gaps in the record, the magnitude of mass accumulation rates (MARs), and monsoon forcing mechanisms. Here we present a detailed quartz optically stimulated luminescence (OSL) chronology from the Xifeng...... common than previously realized. MARs from undisturbed portions of Xifeng vary dramatically, with peaks potentially matching the timing of Heinrich events. The last glacial maximum peak MAR (22–27 ka) matches the Pacific and Greenland dust flux records, although appears earlier than peak MARs seen...

  3. 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...

  4. 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.

  5. 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.

  6. 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)

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. Recent progress of {sup 10}Be tracer studies in Chinese loess

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Weijian, E-mail: weijian@loess.llqg.ac.cn [State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061 (China); Shaanxi Provincial Key Laboratory of Accelerator Mass Spectrometry and Application, Xi’an AMS Center, Xi' an 710061 (China); Joint Center for Global Change Studies, Beijing 100875 (China); Xie, Xingjun [State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061 (China); Shaanxi Provincial Key Laboratory of Accelerator Mass Spectrometry and Application, Xi’an AMS Center, Xi' an 710061 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Beck, Warren [NSF-Arizona AMS Facility, University of Arizona, Tucson, AZ 85721 (United States); Kong, Xianghui; Xian, Feng; Du, Yajuan; Wu, Zhenkun [State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061 (China); Shaanxi Provincial Key Laboratory of Accelerator Mass Spectrometry and Application, Xi’an AMS Center, Xi' an 710061 (China)

    2015-10-15

    Studies of cosmogenic {sup 10}Be in Chinese loess began about twenty-five years ago and since then a number of research groups worldwide have contributed to a firm understanding of the production, transport, deposition and storage of {sup 10}Be in loess. The essential characteristics that make {sup 10}Be a useful isotopic tracer in loess, include: (1) dominant atmospheric production directly linked to the intensity of the Earth’s magnetic field; (2) climate-dependent deposition; and (3) subsequent immobility, so that as {sup 10}Be accumulates in a loess profile its stratigraphic integrity is preserved. This fact, combined with very high deposition rates in loess on the Chinese Loess Plateau, makes {sup 10}Be an especially valuable continental archive of paleoclimate and paleomagnetism, complementing marine and ice-core records. Here we provide in particular the most recent progress of {sup 10}Be tracer studies in Chinese loess, including the determination of the correct age of the Brunhes–Matuyama polarity reversal at 780 ± 3 ka B.P., in accord with marine and ice records, and quantitative reconstruction of 130-ka paleoprecipitation using {sup 10}Be from Chinese loess profiles.

  15. 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.

  16. Soil carbon sequestration potential for "Grain for Green" project in Loess Plateau, China.

    Science.gov (United States)

    Chang, Ruiying; Fu, Bojie; Liu, Guohua; Liu, Shuguang

    2011-12-01

    Conversion of cropland into perennial vegetation land can increase soil organic carbon (SOC) accumulation, which might be an important mitigation measure to sequester carbon dioxide from the atmosphere. The "Grain for Green" project, one of the most ambitious ecological programmes launched in modern China, aims at transforming the low-yield slope cropland into grassland and woodland. The Loess Plateau in China is the most important target of this project due to its serious soil erosion. The objectives of this study are to answer three questions: (1) what is the rate of the SOC accumulation for this "Grain for Green" project in Loess Plateau? (2) Is there a difference in SOC sequestration among different restoration types, including grassland, shrub and forest? (3) Is the effect of restoration types on SOC accumulation different among northern, middle and southern regions of the Loess Plateau? Based on analysis of the data collected from the literature conducted in the Loess Plateau, we found that SOC increased at a rate of 0.712 TgC/year in the top 20 cm soil layer for 60 years under this project across the entire Loess Plateau. This was a relatively reliable estimation based on current data, although there were some uncertainties. Compared to grassland, forest had a significantly greater effect on SOC accumulation in middle and southern Loess Plateau but had a weaker effect in the northern Loess Plateau. There were no differences found in SOC sequestration between shrub and grassland across the entire Loess Plateau. Grassland had a stronger effect on SOC sequestration in the northern Loess Plateau than in the middle and southern regions. In contrast, forest could increase more SOC in the middle and southern Loess Plateau than in the northern Loess Plateau, whereas shrub had a similar effect on SOC sequestration across the Loess Plateau. Our results suggest that the "Grain for Green" project can significantly increase the SOC storage in Loess Plateau, and it is

  17. Soil carbon sequestration potential for "grain for green" project in Loess Plateau, China

    Science.gov (United States)

    Chang, R.; Fu, B.; Liu, Gaisheng; Liu, S.

    2011-01-01

    Conversion of cropland into perennial vegetation land can increase soil organic carbon (SOC) accumulation, which might be an important mitigation measure to sequester carbon dioxide from the atmosphere. The "Grain for Green" project, one of the most ambitious ecological programmes launched in modern China, aims at transforming the low-yield slope cropland into grassland and woodland. The Loess Plateau in China is the most important target of this project due to its serious soil erosion. The objectives of this study are to answer three questions: (1) what is the rate of the SOC accumulation for this "Grain for Green" project in Loess Plateau? (2) Is there a difference in SOC sequestration among different restoration types, including grassland, shrub and forest? (3) Is the effect of restoration types on SOC accumulation different among northern, middle and southern regions of the Loess Plateau? Based on analysis of the data collected from the literature conducted in the Loess Plateau, we found that SOC increased at a rate of 0.712 TgC/year in the top 20 cm soil layer for 60 years under this project across the entire Loess Plateau. This was a relatively reliable estimation based on current data, although there were some uncertainties. Compared to grassland, forest had a significantly greater effect on SOC accumulation in middle and southern Loess Plateau but had a weaker effect in the northern Loess Plateau. There were no differences found in SOC sequestration between shrub and grassland across the entire Loess Plateau. Grassland had a stronger effect on SOC sequestration in the northern Loess Plateau than in the middle and southern regions. In contrast, forest could increase more SOC in the middle and southern Loess Plateau than in the northern Loess Plateau, whereas shrub had a similar effect on SOC sequestration across the Loess Plateau. Our results suggest that the "Grain for Green" project can significantly increase the SOC storage in Loess Plateau, and it is

  18. 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.

  19. 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.

  20. Spatial and temporal variation in terrestrial net primary productivity on Chinese Loess Plateau and its influential factors%黄土高原植被净初级生产力时空变化及其影响因素

    Institute of Scientific and Technical Information of China (English)

    谢宝妮; 秦占飞; 王洋; 常庆瑞

    2014-01-01

    为了探明黄土高原地区植被生产力变化的驱动机制,该文基于MODIS传感器获得的MOD17A3数据,分析了黄土高原2000-2010年间植被净初级生产力(net primary productivity, NPP)的时空变化及其主要影响因素,并借助多元统计分析方法对引起 NPP 变化的自然和人为因素进行量化分析。结果表明:黄土高原植被总 NPP 从2000年的119 Tg(以C计)增加到2010年的144 Tg(以C计),年增速4.57 g/(m2·a)(P<0.05)(以C计)。黄土高原约91%的区域NPP呈增加趋势,37%的区域增加趋势显著,主要分布在陕西、青海大部分地区、甘肃南部及宁南山区。整个黄土高原近11 a间NPP变化受自然和人为因素共同影响,其中退耕还林还草累计面积、帕尔默干旱指数(palmer drought severity index, PDSI)、耕地面积和人口数量是影响NPP变化的主要因素。退耕还林还草累计面积占四者总贡献率的43%,PDSI占40%,耕地面积和人口数量分别占13%和4%。对区域而言,由退耕还林还草工程引起的土地利用覆被变化是退耕区(陕北、甘肃东南部等)NPP增加的主要因素,而近年来干旱情况的缓解(PDSI 呈上升趋势)则是青海、内蒙古等地 NPP 增加的主要因素。该研究对于黄土高原各区域生态资源管理,以及生态系统的建设具有一定的指导和借鉴意义。%Monitoring dynamics of vegetation productivity and its influential factors are important for understanding the mechanisms of carbon cycling in terrestrial ecosystems. This study investigated the variation in vegetation net primary productivity (NPP) and its major influential factors on the Chinese Loess Plateau during 2000-2010. The remotely sensed time-series data MOD17A3 for vegetation collected by a MODIS sensor was analyzed for NPP changes. The climate factors (temperature, precipitation and solar radiation), palmer drought severity index (PDSI) and

  1. [Assessment indicators of soil quality in hilly Loess plateau].

    Science.gov (United States)

    Xu, Mingxiang; Liu, Guobin; Zhao, Yunge

    2005-10-01

    By the methods of sensitivity analysis, main component analsis and discriminant analysis, this paper screened the sensitive indicators from 32 soil attributes to assess the productivity and erosion-resistance ability of the soils in hilly Loess Plateau. The results showed that soil available phosphorus content, anti-scouring ability, infiltration coefficient, labile organic carbon content, organic matter content and urease activity were the most sensitive indicators for soil quality assessment and the main targets for soil quality management and improvement, while soil biological indicators were with high and medium sensitivity. Five soil quality factors were summed up from 29 soil chemical, physical and biological attributes, i. e., organic matter, texture, phosphorus, porosity and microstructure. Except the factor porosity, the other four factors were significantly different between different land use types. Eight indicators including soil organic matter content, infiltration coefficient, anti-scouring ability, CEC, invertase activity, mean weight diameter (MWD) of aggregates, available phosphorus, and MWD of microaggregate were identified as the assessment indicators of the soil quality in hilly Loess Plateau, with the organic matter content, infiltration coefficient and anti-scouring ability as the key indicators.

  2. 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.

  3. Carbon sequestration function of check-dams: a case study of the Loess plateau in China.

    Science.gov (United States)

    Wang, Yafeng; Chen, Liding; Gao, Yang; Wang, Shuai; Lü, Yihe; Fu, Bojie

    2014-11-01

    Check-dams are the most common structures for controlling soil erosion in the Loess Plateau. However, the effect of check-dams on carbon sequestration, along with sediment transport and deposition, has not been assessed over large areas. In this study, we evaluated the carbon sequestration function of check-dams in the Loess Plateau. The results indicate that there were approximately 11 000 check-dams distributed in the Loess Plateau, with an estimate of the amount of sediment of 21 × 10⁹ m³ and a soil organic carbon storage amount of 0.945 Pg. Our study reveals that check-dams in the Loess Plateau not only conserve soil and water but also sequester carbon.

  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. The evol ution of coupling of Asian winter monsoon and high latitude climate of Northern Hemisphere——Grain evidence from 8.1 Ma loess-red clay sequence on the Chinese central Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    吕连清; 方小敏; JosephA.Mason; 李吉均; 安芷生

    2001-01-01

    The evolution and driving mechanism of the Asian winter monsoon system are of great importance to understanding the present-day climate. Through high-resolution particle size analysis of the oldest loess-red clay sequence known so far (with a basal age of about 8 Ma) and comparison of the results with oxygen isotope curves from North Atlantic marine sediments, 4 stages of the evolution of the Asian winter monsoon were clearly demonstrated. During the first stage, between about 8.1 and 4.3 Ma, there was no relation between Asian winter monsoon and Northern Hemisphere ice volume and high latitude climate inferred from marine sediments. A weak relation developed during the second stage, about 4.3 to 3.5 Ma. During the third stage (3.5 to 2.6 Ma) an Asian winter monsoon system similar to the present formed, initiating a stronger relation between the winter monsoon and Northern Hemisphere ice volume and high latitude climate. In the final stage (2.6 to 0 Ma) the present Asian winter monsoon system was fortifi

  6. Towards sustainable integrated watershed ecosystem management: a case study in Dingxi on the loess plateau, China.

    Science.gov (United States)

    Chen, Liding; Yang, Lei; Wei, Wei; Wang, Ziting; Mo, Baoru; Cai, Guojun

    2013-01-01

    The Chinese government initiated a massive conservation program called "Grain-for-Green" in 1999 to reduce soil erosion and improve ecosystem function. Implementing practical sustainable development in the loess plateau still remains problematic, particularly in its eco-fragile areas. Here we discussed an approach for sustainable development at the watershed scale by integrating land use suitability, ecosystem services and public participation in the loess hilly area. We linked land use scenario analysis and economic modeling to compare the outcomes of three scenarios, CLU (Current Land Use), GOLU (Grain-production Oriented Land Use) and PSLU (Potential Sustainable Land Use). The results indicated that compared to PSLU, GOLU may provide a higher economic productivity in the short-term, but not in the long-term. CLU ranked lowest in terms of economic benefits and did not meet the daily needs of the local farmers. To reconcile the land use adjustments with farmers' basic needs, a labor-saving land use strategy is necessary. Since the PSLU scenario assumes that slope cropland should be converted to pastures or orchards, more time may be available for off-farm work and for more public participation in integrated ecosystem management. Financial support to the local farmers for environmental conservation should be modulated in function of their positive contribution to ecosystem management.

  7. Climate and land use controls on soil organic carbon in the loess plateau region of China.

    Science.gov (United States)

    Dang, Yaai; Ren, Wei; Tao, Bo; Chen, Guangsheng; Lu, Chaoqun; Yang, Jia; Pan, Shufen; Wang, Guodong; Li, Shiqing; Tian, Hanqin

    2014-01-01

    The Loess Plateau of China has the highest soil erosion rate in the world where billion tons of soil is annually washed into Yellow River. In recent decades this region has experienced significant climate change and policy-driven land conversion. However, it has not yet been well investigated how these changes in climate and land use have affected soil organic carbon (SOC) storage on the Loess Plateau. By using the Dynamic Land Ecosystem Model (DLEM), we quantified the effects of climate and land use on SOC storage on the Loess Plateau in the context of multiple environmental factors during the period of 1961-2005. Our results show that SOC storage increased by 0.27 Pg C on the Loess Plateau as a result of multiple environmental factors during the study period. About 55% (0.14 Pg C) of the SOC increase was caused by land conversion from cropland to grassland/forest owing to the government efforts to reduce soil erosion and improve the ecological conditions in the region. Historical climate change reduced SOC by 0.05 Pg C (approximately 19% of the total change) primarily due to a significant climate warming and a slight reduction in precipitation. Our results imply that the implementation of "Grain for Green" policy may effectively enhance regional soil carbon storage and hence starve off further soil erosion on the Loess Plateau.

  8. Brunhes-Matuyama Magnetic Polarity Reversal Tracing using Chinese loess10Be

    Science.gov (United States)

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

    2014-12-01

    The geomagnetic polarity reversal is generally considered to occur synchronously around the world, and is commonly used as a time marker. However, in the case of the most recent reversal, the Brunhes-Matuyama (B-M) reversal (~780 ka), comparison of paleomagnetic studies in Chinese loess-paleosol sequences versus marine sediments revealed a marked discrepancy in timing of this event (Tauxe et al., 1996; Zhou and Shackleton, 1999), leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments (Wang et al., 2006; Liu et al., 2008; Jin and Liu, 2011). 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 (Masarik and Beer, 1999). This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out the 10Be studies 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 S7corresponding to MIS 19. These results have proven that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records (Tauxe et al., 1996) and 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 magnetic polarity reversal recorded in these same Chinese loess-paleosol sequences, demonstrating that loess magnetic overprinting has occurred. 1.Jin, C.S.,et al., 2011,PALAEOGEOGR PALAEOCL, 299, 309-3172.Liu, Q.S., et al., 2008, EARTH

  9. Breaking the spiral of unsustainability : An exploratory Land use study for Ansai, the Loess Plateau of China

    NARCIS (Netherlands)

    Lu Changhe,

    2000-01-01

    Serious soil loss, food insecurity, population pressure, and low income of the rural population are interrelated, and consequently result in a spiral of unsustainability in the Loess Plateau, China. This thesis takes Ansai County in the Loess Plateau of China as a case study, to explore strategic la

  10. Reduced Runoff Due to Anthropogenic Intervention in the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    Yanzhong Li

    2016-10-01

    Full Text Available To maintain the sustainable utilization of water resources and reduce soil erosion in the Loess Plateau, the Chinese government has adopted a number of environmental restoration strategies since 1999, including the Grain for Green Project (GFGP and the Natural Forest Conservation Program; these large projects greatly alter the regional water cycle. Detecting runoff changes and quantitatively assessing the contribution of anthropogenic activities (including land use/cover change (LUCC and water diversion and climate change (including potential evaporation and precipitation are imperative for implementing sustainable management strategies. Using observed records from 15 hydrological stations and 85 national meteorological stations from 1980 to 2013, the decomposition method, based on the Budyko hypothesis, is used to quantify the impact of climate variation and anthropogenic interference on annual runoff for the 12 catchments in the Loess Plateau. The results show the following: (1 the observed annual runoff exhibited a negative trend in all 12 catchments (significant in eight catchments with a range of −1.94 to −0.16 mm·year−1 and exhibited a substantial difference before and after 1999; (2 the sensitivity of runoff to vegetation change, precipitation, and potential evapotranspiration increased in most catchments after 1999, indicating that great challenges and uncertainties might be introduced to regional water resource availability; and (3 the anthropogenic interference, particularly LUCC caused by forest strategies, has become the main contribution to runoff change. We suggest that more attention should be given to water resource availability and that the hydrologic consequences of revegetation should be taken into account in future management.

  11. 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.

  12. 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.

  13. 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...

  14. 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

  15. [Coupling coordinated development of ecological-economic system in Loess Plateau].

    Science.gov (United States)

    Zhang, Qing-Feng; Wu, Fa-Qi; Wang, Li; Wang, Jian

    2011-06-01

    Based on system theory, a coupling coordinated development model of ecological-economic system in Loess Plateau was established, and the evaluation criteria and basic types of the coordinated development of the ecological-economic system were proposed. The county-level coupling coordinated development of the ecological-economic system was also discussed, based on the local characteristics. The interactions between the ecological and economic systems in Loess Plateau could be divided into four stages, i.e., seriously disordered development stage, mild-disordered development stage, low-level coordinated development stage, and high level well-coordinated development stage. At each stage, there existed a cyclic process of profit and loss-antagonist-running-dominant-synchronous development. The coupling development degree of the ecological-economic system in Loess Plateau was overall at a lower level, being about 62.7% of the counties at serious disorder, 30.1% of the counties at mild disorder, and 7.1% of the counties at low but coordinated level. The coupling development degree based on the model established in this study could better reflect the current social-economic and ecological environment situations, especially the status of coordination. To fully understand the coupling of ecological-economic system and to adopt appropriate development mode would be of significance to promote the county-level coordinated development in Loess Plateau.

  16. 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

  17. 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.

  18. 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.

  19. Typical Geochemical Elements in Loess Deposit in the Northeastern Tibetan Plateau and Its Paleoclimatic Implication

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Widespread and thick loess deposit in the northeastern Tibetan Plateau records paleoclimatic changes over the Quaternary period. In this study, we investigate a loess section located in a high terrace of the Huangshui River in the Xining Basin, and collect samples at 20-cm intervals by digging a well of 16-m depth (including paleosol S1 and S0 and several loess interlayers over the last glacial-interglacial cycle and the Holocene). Concentration of some active elements (Sr and Ca) and inert elements (Rb, Zr, Ti) in these loess samples are measured. The results show that ratios of those elements (oxide), such as Rb/Sr, Ti/Sr, and Zr/CaO ratios, would indicate sensitively paleoclimatic changes, especially the history of precipitation over the last glacial-interglacial and the Holocene.Moreover, the curves of Rb/Sr, Ti/Sr, and Zr/CaO ratios had almost the same variable trends from the bottom to the top and also closely correlated with values of magnetic susceptibility and the global marine δ18O record. But compared with the curves of magnetic susceptibility, the changes of ratios of these elements (oxide) are clearer and easy to understand. Therefore, the ratios of these typical chemical elements in the loess deposit may be used as an excellent index to investigate the history of paleoclimate, particularly precipitation changes in the northeastern Tibetan Plateau.

  20. 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

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. Soil carbon fractions and enzyme activities under different vegetation types on the Loess Plateau of China

    OpenAIRE

    Zhang, Haixin; Zeng, Quanchao; An, Shaoshan; Dong, Yanghong; Darboux, Frédéric

    2016-01-01

    Vegetation restoration was effective way of protecting soil erosion and water conservation on the Loess Plateau. Carbon fractions and enzyme activities were sensitive parameters for assessment of soil remediation through revegetation. Forest, forest steppe and grassland soils were collected at 0–5 cm and 5–20 cm soil layers in Yanhe watershed, Shaanxi Province. Urease, sucrase, alkaline phosphatase, soil organic carbon (SOC), microbial biomass carbon (MBC), easily ox...

  6. 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.

  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. Simulating the Effect of Climate Change on Vegetation Zone Distribution on the Loess Plateau, Northwest China

    Directory of Open Access Journals (Sweden)

    Guoqing Li

    2015-06-01

    Full Text Available A risk assessment of vegetation zone responses to climate change was conducted using the classical Holdridge life zone model on the Loess Plateau of Northwest China. The results show that there are currently ten vegetation zones occurring on the Loess Plateau (1950–2000, including alvar desert, alpine wet tundra, alpine rain tundra, boreal moist forest, boreal wet forest, cool temperate desert, cool temperate desert scrub, cool temperate steppe, cool temperate moist forest, warm temperate desert scrub, warm temperate thorn steppe, and warm temperate dry forest. Seventy years later (2070S, the alvar desert, the alpine wet tundra and the cool temperate desert will disappear, while warm temperate desert scrub and warm temperate thorn steppe will emerge. The area proportion of warm temperate dry forest will expand from 12.2% to 22.8%–37.2%, while that of cool temperate moist forest will decrease from 18.5% to 6.9%–9.5%. The area proportion of cool temperate steppe will decrease from 51.8% to 34.5%–51.6%. Our results suggest that future climate change will be conducive to the growth and expansion of forest zones on the Loess Plateau, which can provide valuable reference information for regional vegetation restoration planning and adaptive strategies in this region.

  9. Quantifying the effects of conservation practices on soil, water, and nutrients in the Loess Mesa Ravine Region of the Loess Plateau, China.

    Science.gov (United States)

    Xu, Xiang-Zhou; Li, Mei-Juan; Liu, Bin; Kuang, Shang-Fu; Xu, Shi-Guo

    2012-05-01

    A large number of soil and water conservation programs have been implemented on the Loess Plateau of China since the 1950s. To comprehensively assess the merits and demerits of the conservation practices is of great importance in further supervising the conservation strategy for the Loess Plateau. This study calculates the impact factors of conservation practices on soil, water, and nutrients during the period 1954-2004 in the Nanxiaohegou Catchment, a representative catchment in the Loess Mesa Ravine Region of the Loess Plateau, China. Brief conclusions could be drawn as follows: (1) Soil erosion and nutrient loss had been greatly mitigated through various conservation practices. About half of the total transported water and 94.8 % of the total transported soil and nutrients, had been locally retained in the selected catchment. The soil retained from small watersheds do not only form large-scale fertile farmland but also safeguard the Yellow River against overflow. (2) Check dam was the most appropriate conservation practice on the Loess Plateau. In the selected catchment, more than 90 % of the retained soil and water were accomplished by the dam farmland, although the dam farmland occupied only 2.3 % of the total area of all conservation measures. Retention abilities of the characteristic conservation practices were in the following order: dam farmland > terrace farmland > forest land and grassland. (3) The conservation practices were more powerful in retaining sediment than in reducing runoff from the Loess Plateau, and the negative effects of the conservation practices on reducing water to the Yellow River were relatively slight.

  10. Quantifying the Effects of Conservation Practices on Soil, Water, and Nutrients in the Loess Mesa Ravine Region of the Loess Plateau, China

    Science.gov (United States)

    Xu, Xiang-Zhou; Li, Mei-Juan; Liu, Bin; Kuang, Shang-Fu; Xu, Shi-Guo

    2012-05-01

    A large number of soil and water conservation programs have been implemented on the Loess Plateau of China since the 1950s. To comprehensively assess the merits and demerits of the conservation practices is of great importance in further supervising the conservation strategy for the Loess Plateau. This study calculates the impact factors of conservation practices on soil, water, and nutrients during the period 1954-2004 in the Nanxiaohegou Catchment, a representative catchment in the Loess Mesa Ravine Region of the Loess Plateau, China. Brief conclusions could be drawn as follows: (1) Soil erosion and nutrient loss had been greatly mitigated through various conservation practices. About half of the total transported water and 94.8 % of the total transported soil and nutrients, had been locally retained in the selected catchment. The soil retained from small watersheds do not only form large-scale fertile farmland but also safeguard the Yellow River against overflow. (2) Check dam was the most appropriate conservation practice on the Loess Plateau. In the selected catchment, more than 90 % of the retained soil and water were accomplished by the dam farmland, although the dam farmland occupied only 2.3 % of the total area of all conservation measures. Retention abilities of the characteristic conservation practices were in the following order: dam farmland > terrace farmland > forest land and grassland. (3) The conservation practices were more powerful in retaining sediment than in reducing runoff from the Loess Plateau, and the negative effects of the conservation practices on reducing water to the Yellow River were relatively slight.

  11. Ecologically asynchronous agricultural practice erodes sustainability of the Loess Plateau of China.

    Science.gov (United States)

    Wang, Tianming; Wu, Jianguo; Kou, Xiaojun; Oliver, Chadwick; Mou, Pu; Ge, Jianping

    2010-06-01

    Sustainability of agricultural landscapes depends largely on land-use practices. As one of the most productive and widespread agricultural soils, loess is often deep and easily eroded, posing grand challenges for environmental sustainability around the world. One prime example is the Loess Plateau of China, which has been cultivated for more than 7500 years. Based on long-term data sets, this study demonstrates that the dominant agricultural practice, winter wheat cropping, continues to be the primary driver for the massive soil erosion and landscape modifications on the Loess Plateau. This traditional farming system is asynchronous with the dynamic rhythm between natural vegetation and climate in the region. In particular, the long summer fallow period for winter wheat fields is concurrent with the heavy-rainstorm season, which greatly accelerates soil erosion. Our finding indicates that common land-use practices that have lasted for thousands of years in China are not environmentally sustainable. Agriculture in this region has relied primarily on the continuous "mining" of the soil for the past several thousand years but does not have a one-thousand-year future because of myriad environmental and socioeconomic factors associated with soil erosion. To contain soil erosion and promote sustainability on the Loess Plateau, therefore, a change in the agricultural regime is needed to make sure that current and future agricultural practices follow the vegetation-climate rhythm. In addition, to achieve environmental, economic, and social sustainability in this region, multifunctional land-use planning is required to increase landscape diversity and functions (e.g., proper arrangement of crop fields, orchards, and protected areas).

  12. 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.

  13. 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

  14. 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)

  15. Aggregate Characteristics During Natural revegetation on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    AN Shao-Shan; HUANG Yi-Mei; ZHENG Fen-Li; YANG Jian-Guo

    2008-01-01

    Field investigations and laboratory analysis were conducted to study the characteristics of soil water-stable aggregates during vegetation rehabilitation in typical grassland soils of the hilly-gullied loess area. The relationship between water-stable aggregates and other soil properties was analyzed using canonical correlation analysis and principal component analysis. The results show that during the natural revegetation, the aggregates > 5 mm dominated and constituted between 50% and 80% of the total soil water-stable aggregates in most of the soil layers. The 2-5 mm aggregate class was the second main component. The mean value of water-stable aggregates > 5 mm within the 0-2 m soil profile under different plant communities decreased in the following order: Stipa grandis > Stipa bungeana Trin. > Artemisia sacrorum Ledeb. > Thymus mongolicus Ronn. > Hierochloe odorata (L.) Beauv. Clay, organic matter, and total N were the key factors that influenced the water stability of the aggregates. Total N and organic matter were the main factors that affected the water stability of the aggregates > 5 mm and 0.5-1 mm in size. The contents of Fe2O3, Al2O3, and physical clay (< 0.01 mm) were the main factors which affected the water stability of the 1-2 and 0.25-0.5 mm aggregates.

  16. 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.

  17. 3Ma以来黄土高原朝那黄土-红粘土序列赤铁矿记录及其古气候意义%HEMATITE RECORD OF 3Ma LOESS-RED CLAY SEQUENCES IN THE CENTRAL CHINESE LOESS PLATEAU 3Ma AND ITS PALEOCLIMATIC SIGNIFICANCE

    Institute of Scientific and Technical Information of China (English)

    李香钰; 方小敏; 杨一博; 昝金波

    2012-01-01

    . The result of the characters of x-T curves, x-T curves of different temperatures, IRM acquisition, hysteresis loops indicate the major magnetic material and magnetic carrier of the characteristic remanent magnetization are magnetite, hematite and maghemite. Zhuanglang red clay is characterized by significantly high concentration of magnetite and maghemite during the Middle Miocene Climate Optimum, but considerably lower concentration before and after the MMCO. To the contrary, the content of hematite is lower in the MMCO than the period before and after MMCO. Combined with Day-plot we can know the average grain size of the samples is pseudo single domain( PSD) . According to magnetic parameters such as xld , SIRM , S-ratio curves varitations along with depth, we can conclude that the enhancement of magnetic susceptibility during 16. 5 ~ 13. 8Ma is probably dependent on the ferriomagnetic mineral concentration , the grain size of which are the superparamagnetic ( SP) , single domain ( SD) , pseudo single domain( PSD). This obviously high concentration of magnetite and maghemite during the MMCO may indicate an enhancement of the Asian summer monsoon and pedogenesis in the Chinese Loess Plateau. Through other climate parameters from the continent and ocean we suppose that the summer monsoon and the winter monsoon in East Asia are all strengthened during the Middle Miocene Climate Optimum.%土壤和前期研究表明黄土-红粘土序列的赤铁矿含量与环境密切相关,对气候的干湿变化非常敏感,气候越湿热,赤铁矿含量越高.本文研究表明黄土-红粘土样品漫反射光谱一阶导数曲线在555~575nm间的峰面积作为赤铁矿指数可以客观有效地指示赤铁矿含量的高低.通过黄土高原朝那剖面红粘土-黄土序列的系统漫反射光谱分析,建立了3Ma以来黄土高原赤铁矿含量变化记录,揭示赤铁矿含量在约2.5Ma,1.5Ma,0.6Ma和0.15Ma显著阶段性减小,指示了黄土高原阶段性变冷干的演化历史.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Aragonite-calcite transformation in fossil snail shells of loess sequences in Loess Plateau, Central China

    Institute of Scientific and Technical Information of China (English)

    SHENG Xuefen; CHEN Jun; CAI Yuanfeng; CHEN Yang; JI Junfeng

    2005-01-01

    The methods of X-ray diffraction (XRD) and ICP-AES are applied to analyzing the mineral composition of modern and fossil snail shells in Luochuan section and Xifeng section. The results show that the mineral phase of calcium carbonate in modern snail shells is aragonite, but for some fossil snail shells in certain layers of loess sequences, a part of aragonite is transformed into calcite. In Luochuan and Xifeng sections, the stratigraphic borderline of aragonite-calcite transformation appearing obviously is between L5 and L6. Under the earth surface condition, the aragonite-calcite transformation is influenced by the factor of temperature only in a long time scale. It seems that the pressure is not the factor influencing the aragonite-calcite transformation. The results also show that existing age of snail shells is possibly the dominant and principal factor for the aragonite-calcite transformation. To a certain extent, the degree of aragonite-calcite transformation in snail shell is controlled by the content of trace element, such as Mg2+. The trace element can improve the stability of snail shell aragonite and impede the process of aragonite transforming into calcite.

  3. Evaluating the coupling effects of climate aridity and vegetation restoration on soil erosion over the Loess Plateau in China.

    Science.gov (United States)

    Zhang, Baoqing; He, Chansheng; Burnham, Morey; Zhang, Lanhui

    2016-01-01

    In this study, the coupling effects of climate aridity and vegetation restoration on runoff and sediment yield over the Loess Plateau were examined and characterized. To take into consideration the complexity of drought, as well as the varied strengths and weaknesses of different drought measures, two drought indices are selected to identify and evaluate drought variability. The Normalized Difference Vegetation Index (NDVI) data were obtained to monitor and express spatiotemporal variations in vegetation cover. The results show that most regions of the Loess Plateau experienced increasingly severe droughts over the past 40years, and these regions comprise the major source of the Yellow River sediment. Climatic drying initially occurred in the 1990s, and became statistically significant in 2000s. The increasingly severe droughts could negatively impact surface and groundwater supplies as well as soil water storage, but may also minimize surface runoff yield, which is one of the major causes of soil erosion on the Loess Plateau. Vegetation cover on the Loess Plateau was significantly improved after the implementation of "Grain for Green" project, which were helpful for controlling severe soil erosion. With the impacts of the construction of check dams, terraces and large reservoirs, runoff and sediment yield over the Loess Plateau initially exhibited downward trends between 1970 and 1990. After 1990, with the effects of the climate warming and drying, a second sharp reduction in runoff and sediment yield occurred. The coupling effects of climate aridity and vegetation restoration have led to a third significant decrease in runoff and sediment yield over the Loess Plateau after 2000.

  4. 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.

  5. Revegetation in China’s Loess Plateau is approaching sustainable water resource limits

    Science.gov (United States)

    Feng, Xiaoming; Fu, Bojie; Piao, Shilong; Wang, Shuai; Ciais, Philippe; Zeng, Zhenzhong; Lü, Yihe; Zeng, Yuan; Li, Yue; Jiang, Xiaohui; Wu, Bingfang

    2016-11-01

    Revegetation of degraded ecosystems provides opportunities for carbon sequestration and bioenergy production. However, vegetation expansion in water-limited areas creates potentially conflicting demands for water between the ecosystem and humans. Current understanding of these competing demands is still limited. Here, we study the semi-arid Loess Plateau in China, where the `Grain to Green’ large-scale revegetation programme has been in operation since 1999. As expected, we found that the new planting has caused both net primary productivity (NPP) and evapotranspiration (ET) to increase. Also the increase of ET has induced a significant (p ecological and socio-economic resource demands in a coupled anthropogenic-biological system.

  6. Effects of straw and biochar amendments on aggregate stability, soil organic carbon, and enzyme activities in the Loess Plateau, China.

    Science.gov (United States)

    Zhang, Man; Cheng, Gong; Feng, Hao; Sun, Benhua; Zhao, Ying; Chen, Haixin; Chen, Jing; Dyck, Miles; Wang, Xudong; Zhang, Jianguo; Zhang, Afeng

    2017-02-23

    Soil from the Loess Plateau of China is typically low in organic carbon and generally has poor aggregate stability. Application of organic amendments to these soils could help to increase and sustain soil organic matter levels and thus to enhance soil aggregate stability. A field experiment was carried out to evaluate the effect of the application of wheat straw and wheat straw-derived biochar (pyrolyzed at 350-550 °C) amendments on soil aggregate stability, soil organic carbon (SOC), and enzyme activities in a representative Chinese Loess soil during summer maize and winter wheat growing season from 2013 to 2015. Five treatments were set up as follows: no fertilization (CK), application of inorganic fertilizer (N), wheat straw applied at 8 t ha(-1) with inorganic fertilizer (S8), and wheat straw-derived biochar applied at 8 t ha(-1) (B8) and 16 t ha(-1) (B16) with inorganic fertilizer, respectively. Compared to the N treatment, straw and straw-derived biochar amendments significantly increased SOC (by 33.7-79.6%), microbial biomass carbon (by 18.9-46.5%), and microbial biomass nitrogen (by 8.3-38.2%), while total nitrogen (TN) only increased significantly in the B16 plot (by 24.1%). The 8 t ha(-1) straw and biochar applications had no significant effects on soil aggregation, but a significant increase in soil macro-aggregates (>2 mm) (by 105.8%) was observed in the B16 treatment. The concentrations of aggregate-associated SOC increased by 40.4-105.8% in macro-aggregates (>2 mm) under straw and biochar amendments relative to the N treatment. No significant differences in invertase and alkaline phosphatase activity were detected among different treatments. However, urease activity was greater in the biochar treatment than the straw treatment, indicating that biochar amendment improved the transformation of nitrogen in the soil. The carbon pool index and carbon management index were increased with straw and biochar amendments, especially in the B16

  7. Calcium Nodules as a Proxy for Quaternary Paleoclimate Change on China's Loess Plateau.

    Science.gov (United States)

    He, Wenming; He, Hongming; Zhu, Mingyong

    2015-01-01

    Different proxies have been used to investigate Quaternary paleoclimate change. Here, we used weathering of calcium nodules in paleosols on China's Loess Plateau as a proxy for Quaternary paleoclimate changes to provide an alternative indicator of these changes. Paleosol and carbonate nodules were collected from Luochuan and Lantian counties in Shaanxi Province, China. We found that this approach allowed quantitative reconstruction of temperature, rainfall, soil mineral composition, and the effects of weathering and leaching. The changes in carbonate content in the loess and paleosol sequences were controlled by alternating dry and wet climatic conditions. Nodule formation conditions were directly affected by the leaching and migration of elements. The loess and paleosol sequences developed calcium nodules, and their formation was closely related to the rainfall and leaching characteristics of the paleoclimate. The paleoclimate and soil minerals affected the vegetation types and directly influenced changes in the soil. During formation of the calcium nodules, the surface vegetation evolved slowly, and the number of species and quantity of vegetation both decreased.

  8. 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.

  9. 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:

  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. 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.

  13. 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.

  14. 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.

  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. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary

    Science.gov (United States)

    Lu, H.; Mason, J.A.; Stevens, T.; Zhou, Y.; Yi, S.; Miao, X.

    2011-01-01

    This paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long-held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well-dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11-8ka and 1-0ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post-depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons. ?? 2011 John Wiley & Sons, Ltd.

  8. 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), Prunoff mainly occurred in three stages, with transitions in 1970, 1981 and 1996. Reduced precipitation was the main reason for the decrease in runoff over the entire study period. However, human intervention played a dominant role in creating the transition points. Water yield (i.e., the ratio of runoff to precipitation) decreased following each anthropogenic 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Roots of forbs sense climate fluctuations in the semi-arid Loess Plateau: Herb-chronology based analysis

    Science.gov (United States)

    Shi, Songlin; Li, Zongshan; Wang, Hao; von Arx, Georg; Lü, Yihe; Wu, Xing; Wang, Xiaochun; Liu, Guohua; Fu, Bojie

    2016-06-01

    Growth of herbaceous plants responds sensitively and rapidly to climate variability. Yet, little is known regarding how climate warming influences the growth of herbaceous plants, particularly in semi-arid sites. This contrasts with widely reported tree growth decline and even mortality in response to severe water deficits due to climate warming around the world. Here, we use the relatively novel approach of herb-chronology to analyze the correlation between climatic factors and annual ring width in the root xylem of two perennial forb species (Medicago sativa, Potentilla chinensis) in the Loess Plateau of China. We show that warming-induced water deficit has a significant negative effect on the growth of herbaceous plants in the Loess Plateau. Our results indicate that the growth of forbs responds rapidly and sensitively to drought variability, implying that water availability plays a dominant role in regulating the growth of herbaceous plants in semi-arid areas. If warming and drying in the Loess Plateau continue in the future, further affects the growth of herbaceous plants, potentially driving regional changes in the relationship between herbaceous vegetation and climate.

  19. 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.

  20. Attribution analysis of runoff decline in a semiarid region of the Loess Plateau, China

    Science.gov (United States)

    Li, Binquan; Liang, Zhongmin; Zhang, Jianyun; Wang, Guoqing; Zhao, Weimin; Zhang, Hongyue; Wang, Jun; Hu, Yiming

    2016-12-01

    runoff decline. This study enhances our understanding of runoff changes caused by SWC measures and climate variability in the typical semiarid region of Loess Plateau, China.

  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 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.

  2. 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.

  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. 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

  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. 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

  7. Effects of pruning intensity on jujube transpiration and soil moisture of plantation in the Loess Plateau

    Science.gov (United States)

    Nie, Zhenyi; Wang, Xing; Wang, Youke; Ma, Jianpeng; Wei, Xinguang; Chen, Dianyu

    2017-01-01

    In order to ease soil desiccation and prevent ecological deterioration in the Loess Plateau, where jujube (Zizyphus jujube MIll) is widely cultivated as a drought tolerant plant, four pruning intensities (PI), from PI-1 (light) to PI-4 (heavy) were set up based on total length of secondary branches to study the effects of pruning on transpiration and soil moisture in jujube plantations. Furthermore, growth indexes were regularly monitored to estimate jujubes biomass. Sap flow, meteorological and soil moisture conditions were monitored using thermal dissipation probes (TDP), weather station (RR-9100) and the combination of time domain transmission (TDT) technology and neutron moisture gauges (CNC503B), respectively. The results showed that daily actual transpiration of jujube was positively correlated with leaf biomass. Compared with PI-1, jujube transpiration during growth period under PI-2, PI-3, and PI-4 dropped by 11.1%, 29.2%, and 47.9%, respectively. On the contrary, annual water storage under PI-2, PI-3, and PI-4 increased by 6.29 mm, 25.78 mm and 34.74 mm while water use efficiency increased by 5.1%, 15.7% and 24.2%, respectively. Overall, increase in pruning intensity could significantly reduce water consumption of jujube and improve soil moisture in jujube plantations.

  8. 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.

  9. Weed inhibition by sowing legume species in early succession of abandoned fields on Loess Plateau, China

    Science.gov (United States)

    Li, Jin-Hua; Xu, Dang-Hui; Wang, Gang

    2008-01-01

    A major constraint on vegetation succession on abandoned land is dominance by early successional species. Our aim was to inhibit weeds and alter the initial vegetation succession by the introduction of legume species ( Medicago sativa, Melilotus suaveolens, and Astragalus adsurgens) into abandoned fields on the Loess Plateau, China. Results from our study showed that the addition of legume species strongly affected the dominance pattern of the abandoned-field vegetation. The number of naturally colonizing species was inhibited by the introduction of legume species in the first two growing seasons. The strongest effect on weed inhibition appeared by sowing Melilotus suaveolens. Vegetation cover and above-ground biomass increased after introduction of legume species and the number of naturally colonizing plant species showed a positive correlation with above-ground biomass. Later successional species like Stipa breviflora and Astragalus polycladus appeared three years following the introduction of Melilotus suaveolens, indicating that the course of old-field succession may be accelerated by introducing legume species such as Melilotus suaveolens, at least temporarily.

  10. How ecological restoration alters ecosystem services: an analysis of carbon sequestration in China's Loess Plateau.

    Science.gov (United States)

    Feng, Xiaoming; Fu, Bojie; Lu, Nan; Zeng, Yuan; Wu, Bingfang

    2013-10-03

    Restoring disturbed and over-exploited ecosystems is important to mitigate human pressures on natural ecosystems. China has launched an ambitious national ecosystem restoration program called Grain to Green Program (GTGP) over the last decade. By using remote sensing techniques and ecosystem modelling, we quantitatively evaluated the changes in ecosystem carbon sequestration since China's GTGP program during period of 2000-2008. It was found the NPP and NEP in this region had steadily increased after the initiative of the GTGP program, and a total of 96.1 Tg of additional carbon had been sequestered during that period. Changes in soil carbon storage were lagged behind and thus insignificant over the period, but was expected to follow in the coming decades. As a result, the Loess Plateau ecosystem had shifted from a net carbon source in 2000 to a net carbon sink in 2008. The carbon sequestration efficiency was constrained by precipitation, and appropriate choices of restoration types (trees, shrubs, and grasses) in accordance to local climate are critical for achieving the best benefit/cost efficiency.

  11. Cyclic precipitation variation on the western Loess Plateau of China during the past four centuries

    Science.gov (United States)

    Tan, Liangcheng; An, Zhisheng; Huh, Chih-An; Cai, Yanjun; Shen, Chuan-Chou; Shiau, Liang-Jian; Yan, Libin; Cheng, Hai; Edwards, R. Lawrence

    2014-09-01

    Precipitation variation on the Loess Plateau (LP) of China is not only important for rain-fed agriculture in this environmentally sensitive region, but also critical for the water and life securities over the whole Yellow River basin. Here we reconstruct high resolution precipitation variation on the western LP during the past 370 years by using two replicated, annually-laminated stalagmites. Spatial analysis suggests that the reconstruction can be also representative for the whole LP region. The precipitation variations show a significant quasi-50 year periodicity during the last 370 years, and have an important role in determining the runoff of the middle Yellow River. The main factor controlling the decadal scale variations and long-term trend in precipitation over this region is southerly water vapour transport associated with the Asian summer monsoon. The Pacific Decadal Oscillation is also an important influence on precipitation variation in this region, as it can affect the East Asian summer monsoon and the West Pacific Subtropical High.

  12. 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.

  13. Analysis of Precipitation Characteristics during 1957-2012 in the Semi-Arid Loess Plateau, China.

    Science.gov (United States)

    Zhao, Weijun; Yu, Xinyang; Ma, Huan; Zhu, Qingke; Zhang, Yan; Qin, Wei; Ai, Ning; Wang, Yu

    2015-01-01

    Precipitation is the only water supply and most important factor affecting vegetation growth on the slopes of semi-arid Loess Plateau of China. Based on precipitation data from 7 synoptic stations in the study area over the period 1957-2012, the trends of precipitation and standardized precipitation index (SPI) were analyzed by using linear regression, Mann-Kendall, and Spearman's Rho tests at the 5% significance level. The results show that (1) the precipitation fluctuation of monthly precipitation was intense (coefficients of variation> 100%), and the drier years were recorded as 1965 and 1995 at all stations. (2) The significant change trend of different stations varied on different time scales: the Changwu station had a significant decreasing trend in April (-0.488 mm/year) and November (-0.249 mm/year), while Luochuan station was in April (-0.457 mm/year); Changwu station displayed a significant increasing trends in winter (0.220 mm/year) and a significant decreasing trends in spring (-0.770 mm/year). The significant decreasing trends in annual precipitation were detected at the Suide (-2.034 mm/year) and Yan'an (-2.129 mm/year) stations. (3) The SPI-12 series analysis suggests that the drought degree of Yulin and Changwu was the lowest and that of Hengshan was the highest among the 7 synoptic stations.

  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. 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.

  16. [Ecological cost of grain production in gully area of Loess Plateau].

    Science.gov (United States)

    Li, Xiao; Xie, Yong-sheng; Zhang, Ying-long; Li, Wen-zhuo

    2010-12-01

    Economic and ecological methods were applied to investigate the ecological cost of grain production in the gully area of Loess Plateau. In the study area in 2008, the ecological loss due to grain production was 7.2% of the total crop output, and the ecological cost reached 2.42 yuan x kg(-1) for wheat and 2.12 yuan x kg(-1) for corn. However, the per unit sales were 1.70 yuan x kg(-1) for wheat and 1.28 yuan x kg(-1) for corn. The combination of high production cost and low income affected the sustainable development of local ecological economy. The analysis of grey relationships among various factors affecting the ecological cost of grain production indicated that yield, sown area, and agricultural mechanical cost were the important factors affecting the ecological cost of grain production, while chemical fertilizer cost and organic fertilizer cost had less impact on the ecological cost of grain production. Under current production conditions, the ecological cost of grain production in the area could be reduced by raising the level of scientific and technological inputs, expanding the scale of family agricultural production, and improving the grain yield.

  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)

    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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Airborne pollen assemblages and weather regime in the central-eastern Loess Plateau, China

    Science.gov (United States)

    Li, Yuecong; Ge, Yawen; Xu, Qinghai; Bunting, Jane M.; Lv, Suqing; Wang, Junting; Li, Zetao

    2015-04-01

    This paper presents the results of pollen trapping studies designed to quantify the pollen assemblages carried in the winds of the Loess Plateau in Luochuan and Hunyuan. The one-year-collection samples analysis results show that pollen assemblages can be more sensitive to the change of climate than the vegetation composition, because of the change of pollen production. The analysis results of pollen traps in different weather regimes indicate that the pollen influx coming from dust weather contribute more to the total pollen influx than that coming from non-dust weather. The wind speed is the most important influenced factor to pollen assemblages, then the mean temperature and the mean relative humidity, the wind direction also contributes some. Strong wind coming from dust direction can make the percent and influx of Artemisia and Chenopodiaceae increase obviously with averagely higher than over 2.7 times in dust weather than in non-dust samples. The influences of wind speed and wind direction are not serious to some arboreal pollen such as Rosaceae, Quercus, Betula, Pinus and Ostryopsis, which are mainly influenced by temperature or the relative humidity such as Salix, Hippophae, Carpinus, Brassicaceae, Cupressaceae, Fabaceae.

  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)

    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.

  4. 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

  5. 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.

  6. Changes in sediment transport in the Kuye River in the Loess Plateau in China

    Institute of Scientific and Technical Information of China (English)

    Jueyi SUI; Yun HE; Cheng LIU

    2009-01-01

    In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations (CSs), as well as discharge and sediment transport at 3 Gauging Stations (GSs) are used to assess the features of sediment transport in the Kuye River. The runoff modulus (defined as the annual average discharge per unit area, L/(s'km2)) and the sediment transport modulus (defined as the annual suspended sediment transport per unit area, t/(yr km2)) are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m3/s in August with an average monthly sediment concentration of 88.9 kg/m3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m3 and occurs in July, which has an average discharge of 42.6 m3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye

  7. Effects of straw and plastic film mulching on greenhouse gas emissions in Loess Plateau, China: A field study of 2 consecutive wheat-maize rotation cycles.

    Science.gov (United States)

    Chen, Haixin; Liu, Jingjing; Zhang, Afeng; Chen, Jing; Cheng, Gong; Sun, Benhua; Pi, Xiaomin; Dyck, Miles; Si, Bingcheng; Zhao, Ying; Feng, Hao

    2017-02-01

    Mulching practices have long been used to modify the soil temperature and moisture conditions and thus potentially improve crop production in dryland agriculture, but few studies have focused on mulching effects on soil gaseous emissions. We monitored annual greenhouse gas (GHG) emissions under the regime of straw and plastic film mulching using a closed chamber method on a typical winter-wheat (Triticum aestivum L. cv Xiaoyan 22) and summer-maize (Zea mays L. cv Qinlong 11) rotation field over two-year period in the Loess Plateau, northwestern China. The following four field treatments were included: T1 (control, no mulching), T2 (4000kgha(-1) wheat straw mulching, covering 100% of soil surface), T3 (half plastic film mulching, covering 50% of soil surface), and T4 (complete plastic film mulching, covering 100% of soil surface). Compared with the control, straw mulching decreased soil temperature and increased soil moisture, whereas plastic film mulching increased both soil temperature and moisture. Accordingly, straw mulching increased annual crop yields over both cycles, while plastic film mulching significantly enhanced annual crop yield over cycle 2. Compared to the no-mulching treatment, all mulching treatments increased soil CO2 emission over both cycles, and straw mulching increased soil CH4 absorption over both cycles, but patterns of soil N2O emissions under straw or film mulching are not consistent. Overall, compared to T1, annual GHG intensity was significantly decreased by 106%, 24% and 26% under T2, T3 and T4 over cycle 1, respectively; and by 20%, 51% and 29% under T2, T3 and T4 over cycle 2, respectively. Considering the additional cost and environmental issues associated with plastic film mulching, the application of straw mulching might achieve a balance between food security and GHG emissions in the Chinese Loess Plateau. However, further research is required to investigate the perennial influence of different mulching applications.

  8. 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

  9. [Comparison on the methods for spatial interpolation of the annual average precipitation in the Loess Plateau region].

    Science.gov (United States)

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

    2015-04-01

    Based on 57 years (1957-2013) daily precipitation datasets of the 85 meteorological stations in the Loess Plateau region, different spatial interpolation methods, including ordinary kriging (OK), inverse distance weighting (IDW) and radial-based function (RBF), were conducted to analyze the spatial variation of annual average precipitation regionally. Meanwhile, the mean absolute error (MAE), the root mean square error (RMSE), the accuracy (AC) and the Pearson correlation coefficient (R) were compared among the interpolation results in order to quantify the effects of different interpolation methods on spatial variation of the annual average precipitation. The results showed that the Moran's I index was 0.67 for the 57 years annual average precipitation in the Loess Plateau region. Meteorological stations exhibited strong spatial correlation. The validation results of the 63 training stations and 22 test stations indicated that there were significant correlations between the training and test values among different interpolation methods. However, the RMSE (IDW = 51.49, RBF = 43.79) and MAE (IDW = 38.98, RBF = 34.61) of the IDW and the RBF showed higher values than the OK. In addition, the comparison of the four semi-variagram models (Circular, Spherical, Exponential and Gaussian) for the OK indicated that the circular model had the lowest MAE (32.34) and the highest accuracy (0.976), while the MAE of the exponential model was the highest (33.24). In conclusion, comparing the validation between the training data and test results of the different spatial interpolation methods, the circular model of the OK method was the best one for obtaining accurate spatial interpolation of annual average precipitation in the Loess Plateau region.

  10. Simulation on slope uncertainty derived from DEMs at different resolution levels: a case study in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    TANGGuoan; ZHAOMudan; LITianwen; LIUYongmei; ZHANGTing

    2003-01-01

    Slope is one of the crucial terrain variables in spatial analysis and land use planning, especially in the Loess Plateau area of China which is suffering from serious soil erosion. DEM based slope extracting method has been widely accepted and applied in practice. However slope accuracy derived from this method usually does not match with its popularity. A quantitative simulation to slope data uncertainty is important not only theoretically but also necessarily to applications. This paper focuses on how resolution and terrain complexity impact on the accuracy of mean slope extracted from DEMs of different resolutions in the Loess Plateau of China. Six typical geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1:10,000 scale topographic maps. Field survey results show that 5 m should be the most suitable grid size for representing slope in the Loess Plateau area. Comparative and math-simulation methodology was employed for data processing and analysis. A linear correlativity between mean slope and DEM resolution was found at all test areas, but their regression coefficients related closely with the terrain complexity of the test areas. If taking stream channel density to represent terrain complexity, mean slope error could be regressed against DEM resolution (X) and stream channel density (S) at 8 resolution levels and expressed as(0.0015S2+0.031S-0.0325)X-0.0045S2-0.155S+0.1625, with a R2 value of over 0.98. Practical tests also show an effective result of this model in applications. The new development methodology applied in this study should be helpful to similar researches in spatial data uncertainty investigation.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Streamflow Regime Variations Following Ecological Management on the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    Jianjun Zhang

    2015-12-01

    Full Text Available The continuous ecological management of the Loess Plateau is known throughout the world for two strategies: the integrated soil conservation project that began in the 1970s, and the “Grain for Green” project that began in the 1990s. Six sub-catchments nested in the Beiluo River basin were selected to investigate streamflow regime variations during the two project periods. The annual streamflow trends and change points were detected using a bootstrap-based Mann-Kendall test and Pettitt test. Annual streamflow (from the 1950s to 2011 exhibited significantly negative trends in five out of six catchments, varying from −0.15 to −0.30 mm/a. During the integrated soil conservation period, the annual streamflow was reduced due to high flow decreases (5% of time exceeded, whereas in the low flows (95% it increased in all sub-catchments. During the “Grain for Green” period, the annual streamflow decreased due to daily streamflow reductions at four stations. In addition to high flow and low flow decreases at the Wuqi and Liujiahe stations during the “Grain for Green” period, it is significant that the low flows continuously increased. Compared with trends from the forestry area, which includes the Zhangcunyi and Huangling stations, incremental annual streamflow reductions were observed in other sub-catchments, which can be linked to ecological management. This result implies that streamflow can be moderated by appropriate management options, even in semiarid areas. It was concluded that a stable streamflow regime can be achieved in vegetated areas, and streamflow moderation is dependent on ecological management practices.

  16. Abatement costs of soil conservation in China's Loess Plateau: balancing income with conservation in an agricultural system.

    Science.gov (United States)

    Hou, Lingling; Hoag, Dana L K; Keske, Catherine M H

    2015-02-01

    This study proposes the use of marginal abatement cost curves to calculate environmental damages of agricultural systems in China's Loess Plateau. Total system costs and revenues, management characteristics and pollution attributes are imputed into a directional output distance function, which is then used to determine shadow prices and abatement cost curves for soil and nitrogen loss. Marginal abatement costs curves are an effective way to compare economic and conservation tradeoffs when field-specific data are scarce. The results show that sustainable agricultural practices can balance soil conservation and agricultural production; land need not be retired, as is current policy.

  17. Analysis of baseflow index based hydrological model in Upper Wei River basin on the Loess Plateau in China

    OpenAIRE

    Liu, D; Chang, J.; Tian, F.; Q. Huang; X. Meng

    2015-01-01

    The baseflow is the drainage from the groundwater and soil water to the streamflow. As one important source of the streamflow, the baseflow could be the main source of the streamflow in the dry season. The Wei River, located in the semi-arid region of the Loess Plateau which is overlain by deep and loose soil, is the largest tributary of the Yellow River. According to former research, most of the streamflow in the dry season in the headwater of the Yellow River is baseflow. For the whole Yell...

  18. 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...

  19. 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.

  20. Attribution of Runoff Change for the Xinshui River Catchment on the Loess Plateau of China in a Changing Environment

    Directory of Open Access Journals (Sweden)

    Guoqing Wang

    2016-06-01

    Full Text Available Stream flow plays a crucial role in the environment, society, and the economy, and identifying the causes of changes in runoff is important to understanding the impact of climate change and human activity. This study examines the variation trends in recorded runoff for the Xinshui River, a tributary of the Yellow River on the Loess Plateau, and uses hydrological simulations to investigate how climate change and human activity have contributed to those trends. Results show that the recorded runoff at the Daning station on the Xinshui River declined significantly from 1955–2008 with an abrupt change occurring in 1973. The Simplified Water Balance Model (SWBM simulates monthly discharge well with a Nash–Sutcliffe efficiency (NSE coefficient of 78% and a relative error of volumetric fit (RE of 0.32%. Runoff depth over the catchment in 1973–2008 fell by 25.5 mm relative to the previous period, with human activity and climate change contributing 60.6% and 39.4% of the total runoff reduction, respectively. However, the impacts induced by climate change and human activities are both tending to increase. Therefore, efforts to improve the ecology of the Loess Plateau should give sufficient attention to the impacts of climate change and human activity.

  1. 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.

  2. 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.

  3. Spring maize yield, soil water use and water use efficiency under plastic film and straw mulches in the Loess Plateau

    Science.gov (United States)

    Lin, Wen; Liu, Wenzhao; Xue, Qingwu

    2016-12-01

    To compare the soil water balance, yield and water use efficiency (WUE) of spring maize under different mulching types in the Loess Plateau, a 7-year field experiment was conducted in the Changwu region of the Loess Plateau. Three treatments were used in this experiment: straw mulch (SM), plastic film mulch (PM) and conventional covering without mulch (CK). Results show that the soil water change of dryland spring maize was as deep as 300 cm depth and hence 300 cm is recommended as the minimum depth when measure the soil water in this region. Water use (ET) did not differ significantly among the treatments. However, grain yield was significantly higher in PM compared with CK. WUE was significantly higher in PM than in CK for most years of the experiment. Although ET tended to be higher in PM than in the other treatments (without significance), the evaporation of water in the fallow period also decreased. Thus, PM is sustainable with respect to soil water balance. The 7-year experiment and the supplemental experiment thus confirmed that straw mulching at the seedling stage may lead to yield reduction and this effect can be mitigated by delaying the straw application to three-leaf stage.

  4. [Effects of mulching and fertilization on winter wheat field soil moisture in dry highland region of Loess Plateau].

    Science.gov (United States)

    Wang, Xiao-Feng; Tian, Xiao-Hong; Chen, Zi-Hui; Chen, Hui-Lin; Wang, Zhao-Hui

    2009-05-01

    A field experiment was conducted in a winter wheat field in Weibei dry highland region of Loess Plateau to study the effects of different mulching and fertilization treatments on soil moisture regime. The treatments were 1) no fertilization, 2) conventional fertilization, 3) recommended fertilization, 4) recommended fertilization + manure, 5) recommended fertilization + plastic mulch on soil ridges, 6) recommended fertilization + plastic mulch on soil ridges and straw mulch in furrows, and 7) recommended fertilization + straw mulch on entire plot. Soil moisture content was determined regularly with a neutron probe. Among the treatments, recommended fertilization plus plastic mulch on soil ridges and straw mulch in furrows in dry season (spring) resulted in the greatest increase of soil water storage and maintained the storage to the critical stage crops needed, followed by recommended fertilization plus plastic mulch on soil ridges. These two treatments could store more precipitation in field, and would benefit the development of rainfed agriculture in dry highland region of Loess Plateau. As for recommended fertilization plus manure, it had the least increase of soil water storage, with a difference of 48.2 mm to the recommended fertilization plus plastic mulch on soil ridges and straw mulch in furrows in dry season.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Application and Modification of Hargreaves Models on the Loess Plateau%Hargreaves模型在黄土高原地区的应用与改进

    Institute of Scientific and Technical Information of China (English)

    王幼奇; 白一茹; 展秀丽

    2013-01-01

    利用黄土高原地区55个气象站30年的气象资料,以Penman-Monteith(PM)公式作为计算ET0的标准,探讨了Hargreaves公式在黄土高原地区的适用性,并对Hargreaves公式进行了修正.结果表明,Hargreaves公式不宜直接应用于黄土高原地区,但修正后的Hargreaves公式计算的3d或更长时间尺度的ET0与PM公式计算的结果吻合度较高.可见,修正后的Hargreaves公式在黄土高原地区具有可行性.%According to meteorological data of 55 climatic stations on the Loess Plateau from 1971 to 2000, the ET0 calculated with Penman-Monteith (PM) equation, was compared to the Hargreaves formula. The objective of the research was to investigate and establish the Hargreaves formula adequate for the Loess Plateau. The results showed that Hargreaves formula should not be applied directly on the Loess Plateau. There was a satisfactory correlation between ET0 of three or more days using modified Hargreaves formula and PM formula. Modified Hargreaves formula could be used for calculating ET0 on the Loess Plateau.

  10. Characteristics of Soil and Organic Carbon Loss Induced by Water Erosion on the Loess Plateau in China.

    Science.gov (United States)

    Li, Zhongwu; Nie, Xiaodong; Chang, Xiaofeng; Liu, Lin; Sun, Liying

    2016-01-01

    Soil erosion has been a common environmental problem in the Loess Plateau in China. This study aims to better understand the losses of soil organic carbon (SOC) induced by water erosion. Laboratory-simulated rainfall experiments were conducted to investigate the characteristics of SOC loss induced by water erosion. The applied treatments included two rainfall intensities (90 and 120 mm h-1), four slope gradients (10°, 15°, 20°, and 25°), and two typical soil types- silty clay loam and silty loam. Results showed that the sediment OC enrichment ratios (ERoc) in all the events were relative stable with values ranged from 0.85 to1.21 and 0.64 to 1.52 and mean values of 0.98 and 1.01 for silty clay loam and silty loam, respectively. Similar to the ERoc, the proportions of different sized particles in sediment showed tiny variations during erosion processes. No significant correlation was observed between ERoc values and the proportions of sediment particles. Slope, rainfall intensity and soil type almost had no impact on ERoc. These results indicate that the transportation of SOC during erosion processes was nonselective. While the mean SOC loss rates for the events of silty clay loam and silty loam were 0.30 and 0.08 g m-2 min-1, respectively. Greater differences in SOC loss rates were found in events among different soil types. Meanwhile, significant correlations between SOC loss and soil loss for all the events were observed. These results indicated that the amount of SOC loss was influenced primarily by soil loss and the SOC content of the original soil. Erosion pattern and original SOC content are two main factors by which different soils can influence SOC loss. It seems that soil type has a greater impact on SOC loss than rainfall characteristics on the Loess Plateau of China. However, more kinds of soils should be further studied due to the special formation processes in the Loess Plateau.

  11. 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

  12. Terrestrial mollusk evidence for the origin and sedimentary environment of the Late Tertiary Red Clay Formation in the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    PEI Yunpeng; WU Naiqin; LI Fengjiang

    2004-01-01

    The origin and sedimentary environment of the Late Tertiary (Neogene) Red Clay Formation in northern China had long been controversial. A new mollusk record from the Xifeng red clay (red-earth) sequence in the central Loess Plateau provides the biological evidence for addressing questions of its origin and environmental implication. The study of composition and preservation condition of seventy mollusk fossil assemblages reveals the initial ecological condition of the red clay formation, avoiding the effect of post-deposited alteration. The result shows that all of identifiable mollusk species are composed of terrestrial taxa, most of them are the common species found in the overlying Quaternary loess-paleosol sequence. Most of fossil individuals preserved in the red clay strata are in living conditions based on the investigation of fieldwork, indicating the original population. Thus, the mollusk fossil assemblages can be used as an indicator of primary environment of the red clay formation. The mollusk record from the Xifeng red clay sequence supports the view that the red clay is an aeolian origin, similar to the overlying Quaternary loess deposits. Our data also reveal the history of environmental changes at Xifeng from 6.2-2.4 Ma, which is coupled in phase with the formation and development of the Arctic ice sheets and the process of the Tibetan Plateau uplift. Both may be the major cause and forcing mechanisms of the late Tertiary environmental changes in the Loess Plateau.

  13. 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.

  14. 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.

  15. 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

  16. Aepyosciurinae -- a new subfamily of Sciuridae (Rodentia, Mammalia) from basal loess deposits at the northeastern border of Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Aepyosciurinae, a new subfamily of Sciuridae, were found at the base of the early Pleistocene loess deposits in Dongxiang County, Gansu Province. Its unilaterally hypsodont and lophodont cheek teeth are unique among the sciurids so far known all over the world. Certain degree of similarity can be observed between the cheek teeth of the new subfamily and the Anomalurinae living in tropical and subtropical forests in central and western Africa. Aepyosciuris orientalis gen. et sp. nov. might have lived in montaneous woodland or grassland and lived on harder leaves, barks, or even grass. This tends to show that the northeastern border area of the Tibetan Plateau had been lifted considerably high in early Pleistocene (ca. 2 Ma), with drier climate, becoming a suitable habitat for Aepyosciurus orientalis.

  17. 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.

  18. 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.

  19. 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.

  20. Testing research for assessing suitability of multi-species of trees Introduced in habitats In hilly and gully areas of Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Zhang Hai; Zhang Lixin; Liu Jianghua

    2006-01-01

    To enrich resource of species,105 arbor species (25 genera,15 families) were introduced to the hilly and gully areas on Loess Plateau.By acclimation and selection,more than 90 tree species (12 genera,8 families) were identified as fine species,including trees suitable for sloping fields such as Pinus sylvestri var mongolica,Pinus tabulaeformis, Platycladus orientalis, and Robinia pseudoacacia,trees suitable for gully bottoms such as Populus davidiana, Populus diversifolia, and Salix cheilophila and non-timber trees such as Prunus armeniaca,Ziziphus jujuba and Prunus persica.For those fine trees,habitat conditions and regularity of requirement of water and fertilizers were studied and then habitat ranges were given.From research results,it could be seen that Robinia pseudoacacia consumed more water,but it could improve the content of organic matters in soil;by contrast,Pinus tabulaeformis and Platycladus orientalis consumed less water and were suitable for dry sloping fields;species of apricot were suitable for sunny or semi-shady sloping fields with good conditions of water and fertilizer;species of pear were suitable for both shady sloping fields and sunny sloping fields;species of Chinese date were suitable for sunny sloping fields.

  1. 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

  2. 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

  3. 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.

  4. [Distribution characteristics of soil pH, CEC and organic matter in a small watershed of the Loess Plateau].

    Science.gov (United States)

    Wei, Xiao-Rong; Shao, Ming-An

    2009-11-01

    Soil chemical properties play important roles in soil ecological functioning. In this study, 207 surface soil (0-20 cm) samples were collected from different representative landscape units in a gully watershed of the Loess Plateau to examine the distribution characteristics of soil pH, cation exchange capacity (CEC) and organic matter, and their relations to land use type, landform, and soil type. The soil pH, CEC and organic matter content ranged from 7.7 to 8.6, 11.9 to 28.7 cmol x kg(-1), and 3.0 to 27.9 g x kg(-1), and followed normal distribution, log-normal distribution, and negative binomial distribution, respectively. These three properties were significantly affected by land use type, landform, and soil type. Soil CEC and organic matter content were higher in forestland, grassland and farmland than in orchard land, and soil pH was lower in forestland than in other three land use types. Soil pH, CEC and organic matter content were higher in plateau land and sloping land than in gully bottom and terrace land. Soil CEC and organic matter content were higher in dark loessial soil and rebified soil, while soil pH was higher in yellow loessial soil. Across all the three landscape factors, soil CEC and organic matter content showed the similar distribution pattern, but an opposite distribution pattern was observed for soil pH.

  5. 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.

  6. 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%.

  7. [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.

  8. 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.

  9. A preliminary investigation of the dynamic characteristics of dried soil layers on the Loess Plateau of China

    Science.gov (United States)

    Wang, Yunqiang; Shao, Ming'an; Shao, Hongbo

    2010-02-01

    SummarySerious soil desiccation, resulting from climatic conditions and poor land management, may lead to the formation of a dried soil layer (DSL), which can negatively affect ecological and hydrological processes. To mitigate these effects through management, it is necessary to understand property interactions within DSLs, compared with those in the whole soil profile, and DSL formation processes under different land uses. We investigated the relationships between soil water content (SWC) and plant root indices, and other soil properties, under various land uses in the Liudaogou watershed on the Loess Plateau, China. We also studied the development of DSLs as a function of the growth age of two vegetation types. Rate of formation and thickness of DSLs were dependent on vegetation type: DSLs formed after 2 years of alfalfa ( Medicago sativa) growth and 3 years of Caragana korshinskii growth; after 4 years of growth, DSLs under alfalfa were thicker than those under C. korshinskii, but after 31 years the DSL thickness under C. korshinskii (4.4 m) exceeded that formed under alfalfa (3 m). The more persistent DSLs occurred below a 100 cm thick upper soil layer that was seasonally dried and replenished by rainfall under both vegetation types. The degree of soil desiccation under natural vegetation was generally less than that under non-indigenous plant species, and was similarly less over a period of about 30 years for a natural plant succession sequence than for an artificial one. Thus, the use of natural vegetation succession management principles would possibly reduce soil desiccation during vegetative restoration. Densities of root length, weight, and surface area, and the average root diameter of soybean ( Glycine max), alfalfa, Stipa bubgeana, and C. korshinskii all decreased with increases in soil depths below 20 cm. Correlations between SWC and root indices, and various soil physical and chemical properties, were generally weaker within the DSL layers than

  10. 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

  11. 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.

  12. 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

  13. Effects of Litter on Seedling Emergence and Seed Persistence of Three Common Species on the Loess Plateau in Northwestern China.

    Science.gov (United States)

    Zhang, Rui; Hu, Xiaowen; Baskin, Jerry M; Baskin, Carol C; Wang, Yanrong

    2017-01-01

    Litter accumulation resulting from land use change (enclosure) is one of the key variables influencing seedling recruitment and consequently the regeneration of plant populations and seed persistence in the soil seed bank. A better understanding of the effects of litter on seed germination and seedling emergence is crucial for developing a new set of indicators for grassland ecosystem health and for grassland management policy. We investigated the effects of seed position in litter and amount of litter covering the seed on seedling emergence and seed persistence of three common species on the Loess Plateau in northwestern China. Seed position beneath the litter layer provided a suitable environment for seedling emergence of the three species. A moderate amount of litter (160 g/m(2)) was beneficial for seedling emergence of the small-seeded species Stipa bungeana and Lespedeza davurica from seeds from beneath the litter layer. The large-seeded species Setaria glauca was more tolerant of a high amount of litter (240 g/m(2)) than the two small-seeded species. Seed persistence in the soil differed among the three species and also was affected by seed position in litter and amount of litter cover. The proportion of viable seeds of Stipa bungeana and Setaria glauca on top of the litter layer increased with an increase in amount of litter. Seedling emergence and seed persistence varied significantly among species, amount of litter and seed position in litter. A moderate amount of litter and seeds positioned beneath the litter layer were better for seedling recruitment than for those on top of the litter layer. A high amount of litter was more favorable for persistence of seeds positioned on top of the litter than for those beneath the litter. Our study showed that maintaining litter amount between 80 and 160 g/m(2) is optimal for S. bungeana dominated grassland on the Loess Plateau. We suggest that litter amount can serve as a guide for monitoring and managing grassland

  14. [Effects of revegetation on organic carbon storage in deep soils in hilly Loess Plateau region of Northwest China].

    Science.gov (United States)

    Zhang, Jin; Xu, Ming-Xiang; Wang, Zheng; Ma, Xin-Xin; Qiu, Yu-Jie

    2012-10-01

    Taking the Robinia pseudoacacia woodlands, Caragana korshinskii shrublands, and abandoned croplands with different years of revegetation in the hilly Loess Plateau region of Northwest China as test objects, this paper studied the profile distribution and accumulation dynamics of organic carbon storage in deep soil (100-400 cm), with those in 0-100 cm soil profile as the control. In 0-100 cm soil profile, the organic carbon storage decreased significantly with the increase of soil depth; while in deep soil, the organic carbon storage had a slight fluctuation. The total organic carbon storage in 100-400 cm soil profile was considerably high, accounting for approximately 60% of that in 0-400 cm soil profile. The organic carbon storage in 80-100 cm soil layer had a significant linear correlation with that in 100-200 and 200-400 cm soil layers, and among the organic carbon storages in the five layers in 0-100 cm soil profile, the organic carbon storage in 80-100 cm soil layer had the strongest correlation with that in 100-400 cm soil profile, being able to be used to estimate the organic carbon storage in deep soil in this region. The organic carbon storage in 0-20 cm soil layer in the three types of revegetation lands was significantly higher than that in slope croplands, but the organic carbon storage in deep soil had no significant difference among the land use types. The organic carbon storage in deep soil increased with the increasing years of revegetation. In R. pseudoacacia woodlands and C. korshinskii shrub lands, the average increasing rate of the organic carbon storage in 100-400 cm soil layer was 0.14 and 0.19 t x hm(-2) x a(-1), respectively, which was comparable to that in the 0-100 cm soil layer in C. korshinskii shrublands. It was suggested that in the estimation of the soil carbon sequestration effect of revegetation in hilly Loess Plateau region, the organic carbon accumulation in deep soil should be taken into consideration. Otherwise, the effect of

  15. A drought hazard assessment index based on the VIC-PDSI model and its application on the Loess Plateau, China

    Science.gov (United States)

    Zhang, Baoqing; Wu, Pute; Zhao, Xining; Wang, Yubao; Gao, Xiaodong; Cao, Xinchun

    2013-10-01

    Drought is a complex natural hazard that is poorly understood and difficult to assess. This paper describes a VIC-PDSI model approach to understanding drought in which the Variable Infiltration Capacity (VIC) Model was combined with the Palmer Drought Severity Index (PDSI). Simulated results obtained using the VIC model were used to replace the output of the more conventional two-layer bucket-type model for hydrological accounting, and a two-class-based procedure for calibrating the characteristic climate coefficient ( K j ) was introduced to allow for a more reliable computation of the PDSI. The VIC-PDSI model was used in conjunction with GIS technology to create a new drought assessment index (DAI) that provides a comprehensive overview of drought duration, intensity, frequency, and spatial extent. This new index was applied to drought hazard assessment across six subregions of the whole Loess Plateau. The results show that the DAI over the whole Loess Plateau ranged between 11 and 26 (the greater value of the DAI means the more severe of the drought hazard level). The drought hazards in the upper reaches of Yellow River were more severe than that in the middle reaches. The drought prone regions over the study area were mainly concentrated in Inner Mongolian small rivers, Zuli and Qingshui Rivers basin, while the drought hazards in the drainage area between Hekouzhen-Longmen and Weihe River basin were relatively mild during 1971-2010. The most serious drought vulnerabilities were associated with the area around Lanzhou, Zhongning, and Yinchuan, where the development of water-saving irrigation is the most direct and effective way to defend against and reduce losses from drought. For the relatively humid regions, it will be necessary to establish the rainwater harvesting systems, which could help to relieve the risk of water shortage and guarantee regional food security. Due to the DAI considers the multiple characteristic of drought duration, intensity, frequency

  16. 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.

  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. 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.

  19. Effects of ecological restoration projects on changes in land cover: A case study on the Loess Plateau in China

    Science.gov (United States)

    Zhao, Jun; Yang, Yanzheng; Zhao, Qingxia; Zhao, Zhong

    2017-03-01

    Changes in land cover have become key components of global environmental change and represent the impact of human activity. To better understand the fundamental processes of land transition characteristics before and after the implementation of ecological programmes, we determined the dominant systematic changes in land cover in Yongshou, a hilly-gully region on the Loess Plateau. This was achieved by performing an in-depth analysis of a cross-tabulation matrix and a modified spatial dynamic degree model. Our results indicated that (1) forest land and cultivated land were the most important land cover types in Yongshou and their persistence would greatly affect the landscape pattern of the entire region; (2) the most significant changing signals in the study area during the periods 1992–2000 and 2000–2013 were from immature forest land to forest land, cultivated land to orchards and orchards to construction land; and (3) the region that experienced the most changes during 1992–2000 was the densely populated county seat of Yongshou; however, from 2000–2013, the region of most changes was Changning, a town located in the northcentral region of Yongshou. These findings reveal the main characteristics of the land cover changes in this region and provide insight into the processes underlying these changes.

  20. [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.

  1. Seasonal characteristics of CO2 fluxes in a rain-fed wheat field ecosystem at the Loess Plateau

    Directory of Open Access Journals (Sweden)

    Q. Guo

    2013-11-01

    Full Text Available This study investigated the dynamics of CO2 flux in a rain-fed wheat field ecosystem using an eddy covariance technique during the 2011 to 2012 wheat-growing season at the Loess Plateau, China. Results showed that the daily CO2 flux was closely related to photosynthetically active radiation (PAR, growth stage, soil temperature and rainfall. The average CO2 flux at different growth stages followed the order jointing and booting > erecting > reviving > heading > wintering > seeding and tillering > grain filling > ripening. The first four stages were carbon sinks, whereas the last four stages were carbon sources. The relationship between nighttime CO2 flux and air temperature was significant and fitted the index model (y=aebt. The relationship between daytime CO2 flux and PAR was also significant and fitted the quadratic model (y=ax2+bx+c. Moreover, daytime CO2 flux was significantly correlated with air temperature and PAR at the erecting, jointing and booting, and heading stages. Nighttime CO2 flux was also significantly correlated with soil temperature at 5 cm depth at the heading as well as jointing and booting stages. The carbon budget in the rain-fed wheat ecosystem was -401 g C m-2 yr-1, which was higher than those in other wheat ecosystems. This study implies that the ability of carbon-sequestration in different wheat field ecosystems may respond differently to climate and environment change.

  2. Effects of ecological restoration projects on changes in land cover: A case study on the Loess Plateau in China

    Science.gov (United States)

    Zhao, Jun; Yang, Yanzheng; Zhao, Qingxia; Zhao, Zhong

    2017-01-01

    Changes in land cover have become key components of global environmental change and represent the impact of human activity. To better understand the fundamental processes of land transition characteristics before and after the implementation of ecological programmes, we determined the dominant systematic changes in land cover in Yongshou, a hilly-gully region on the Loess Plateau. This was achieved by performing an in-depth analysis of a cross-tabulation matrix and a modified spatial dynamic degree model. Our results indicated that (1) forest land and cultivated land were the most important land cover types in Yongshou and their persistence would greatly affect the landscape pattern of the entire region; (2) the most significant changing signals in the study area during the periods 1992–2000 and 2000–2013 were from immature forest land to forest land, cultivated land to orchards and orchards to construction land; and (3) the region that experienced the most changes during 1992–2000 was the densely populated county seat of Yongshou; however, from 2000–2013, the region of most changes was Changning, a town located in the northcentral region of Yongshou. These findings reveal the main characteristics of the land cover changes in this region and provide insight into the processes underlying these changes. PMID:28322250

  3. 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.

  4. 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.

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

    Directory of Open Access Journals (Sweden)

    Tingting Ning

    2015-01-01

    Full Text Available 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 Over the past decades, climate tended to be warmer and drier. However, the mean temperature significantly decreased and precipitation slightly increased from 1998 to 2012, especially in spring and summer, which was one of the major reasons for the increase in the annual maximum NDVI. Compared to temperature, vegetation was more sensitive to precipitation changes in this area. The NDVI and annual precipitation changes were highly synchronous over the first half of the year, while a 1-month time lag existed between the two variables during the second half of the year. (3 Positive human activities, including the “Grain for Green” program and successful environmental treatments at coal mining bases, were some of the other factors that improved the vegetation condition.

  6. Species Composition, Richness and Aboveground Biomass of Natural Grassland in Hilly-Gully Regions of the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    DENG Lei; SHANGGUAN; Zhou-ping

    2014-01-01

    In order to study the characteristics of species composition, richness and aboveground biomass of natural grasslands, and then ifnd out the relations between species richness and aboveground productivity of the communities and possible mechanisms to form the relations, four typical grassland communities (Artemisia capillaries (AC), Thymus quinquecostatus (TQ), Stipa bungeana (SB) and Stipa grandis (SG)) along with a succession sequence in hilly-gully regions of the Loess Plateau, China, were investigated by ifeld survey and laboratory analysis. The results were summarized as follows:Different succession stages had different species compositions as well as different proportions of plant life forms and photosynthetic types, and Asteraceae, Poaceae and Leguminosae were their dominant species as well as their dominant perennial herb species;and different succession stages had signiifcantly different species richness and aboveground biomasses. There were many relation patterns (linear positive correlation, unrelated relations and unimodal relations) between the species richness and aboveground biomass in different succession stages and a signiifcant unimodal relation between the species richness and aboveground biomass in all the grassland communities and the highest species diversity appeared at a moderate level of productivity. The results suggest the unimodal relations in all the grassland communities are accumulative results of the relations in each succession stage.

  7. 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.

  8. [Effect of conservation tillage on weeds in a rotation system on the Loess Plateau of eastern Gansu, Northwest China].

    Science.gov (United States)

    Zhao, Yu-xin; Lu, Jiao-yun; Yang, Hui-min

    2015-04-01

    A field study was conducted to investigate the influences of no-tillage, stubble retention and crop type on weed density, species composition and community feature in a rotation system (winter wheat-common vetch-maize) established 12 years ago on the Loess Plateau of eastern Gansu. This study showed that the weed species composition, density and community feature varied with the change of crop phases. No-tillage practice increased the weed density at maize phase, while rotation with common vetch decreased the density in the no-tillage field. Stubble retention reduced the weed density under maize phase and the lowest density was observed in the no-tillage plus stubble retention field. No-tillage practice significantly increased the weed species diversity under winter wheat phase and decreased the diversity under common vetch phase. At maize phase, a greater species diversity index was observed in the no-tillage field. These results suggested that no-tillage practice and stubble retention possibly suppress specific weeds with the presence of some crops and crop rotation is a vital way to controlling weeds in a farming system.

  9. 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.

  10. Vegetation dynamics and climate seasonality jointly control the interannual catchment water balance in the Loess Plateau under the Budyko framework

    Science.gov (United States)

    Ning, Tingting; Li, Zhi; Liu, Wenzhao

    2017-03-01

    Within the Budyko framework, the controlling parameter (ω in the Fu equation) is widely considered to represent landscape conditions in terms of vegetation coverage (M); however, some qualitative studies have concluded that climate seasonality (S) should be incorporated in ω. Here, we discuss the relationship between ω, M, and S, and further develop an empirical equation so that the contributions from M to actual annual evapotranspiration (ET) can be determined more accurately. Taking 13 catchments in the Loess Plateau as examples, ω was found to be well correlated with M and S. The developed empirical formula for ω calculations at the annual scale performed well for estimating ET by the cross-validation approach. By combining the Budyko framework with the semi-empirical formula, the contributions of changes in ω to ET variations were further decomposed as those of M and S. Results showed that the contributions of S to ET changes ranged from 0.1 to 74.8 % (absolute values). Therefore, the impacts of climate seasonality on ET cannot be ignored, otherwise the contribution of M to ET changes will be estimated with a large error. The developed empirical formula between ω, M, and S provides an effective method to separate the contributions of M and S to ET changes.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  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. Quantifying the effect of ecological restoration on soil erosion in China's Loess Plateau region: an application of the MMF approach.

    Science.gov (United States)

    Li, Changbin; Qi, Jiaguo; Feng, Zhaodong; Yin, Runsheng; Guo, Biyun; Zhang, Feng; Zou, Songbing

    2010-03-01

    Land degradation due to erosion is one of the most serious environmental problems in China. To reduce land degradation, the government has taken a number of conservation and restoration measures, including the Sloping Land Conversion Program (SLCP), which was launched in 1999. A logical question is whether these measures have reduced soil erosion at the regional level. The objective of this article is to answer this question by assessing soil erosion dynamics in the Zuli River basin in the Loess Plateau of China from 1999 to 2006. The MMF (Morgan, Morgan and Finney) model was used to simulate changes in runoff and soil erosion over the period of time during which ecological restoration projects were implemented. Some model variables were derived from remotely sensed images to provide improved land surface representation. With an overall accuracy rate of 0.67, our simulations show that increased ground vegetation cover, especially in forestlands and grasslands, has reduced soil erosion by 38.8% on average from 1999 to 2006. During the same time period, however, the change in rainfall pattern has caused a 13.1% +/- 4.3% increase in soil erosion, resulting in a net 25.7% +/- 8.5% reduction in soil erosion. This suggests that China's various ecological restoration efforts have been effective in reducing soil loss.

  18. 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.

  19. 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.

  20. Soil, Leaf and Root Ecological Stoichiometry of Caragana korshinskii on the Loess Plateau of China in Relation to Plantation Age

    Science.gov (United States)

    Zeng, Quanchao; Lal, Rattan; Chen, Yanan; An, Shaoshan

    2017-01-01

    Caragana korshinskii, a leguminous shrub, a common specie, is widely planted to prevent soil erosion on the Loess Plateau. The objective of this study was to determine how the plantation ages affected soil, leaf and root nutrients and ecological stoichiometry. The chronosequence ages of C. korshinskii plantations selected for this study were 10, 20 and 30 years. Soil organic carbon (SOC) and soil total nitrogen (STN) of C. korshinskii plantations significantly increased with increase in the chronosequence age. However, soil total phosphorous (STP) was not affected by the chronosequence age. The soil C: N ratio decreased and the soil C: P and N: P ratios increased with increasing plantation age. The leaf and root concentrations of C, N, and P increased and the ratios C: N, C: P, and N: P decreased with age increase. Leaf N: P ratios were >20, indicating that P was the main factor limiting the growth of C. korshinskii. This study also demonstrated that the regeneration of natural grassland (NG) effectively preserved and enhanced soil nutrient contents. Compared with NG, shrub lands (C. korshinskii) had much lower soil nutrient concentrations, especially for long (>20 years) chronosequence age. Thus, the regeneration of natural grassland is an ecologically beneficial practice for the recovery of degraded soils in this area. PMID:28076357

  1. Ecosystem Health Assessment at County-Scale Using the Pressure-State-Response Framework on the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    Delin Liu

    2016-12-01

    Full Text Available Assessing ecosystem health is helpful to determine reasonable eco-environmental restoration and resource management strategies. Based on a pressure-state-response (PSR framework, a set of comprehensive indicators including natural, social and economic aspects was proposed and applied for assessing the ecosystem health of Yuanzhou County, Loess Plateau, Ningxia Province, China. The basic data used to calculate the values of the assessment indicators include Landsat TM image and socio-economic data, and remote sensing (RS and the geographic information system (GIS were used to process image data. The results showed that the ecosystem health conditions of most townships in Yuanzhou County were at the moderately healthy level, three townships were at the healthy level, and only two townships were at the unhelathy level; the areas (percentage at the unhealthy, moderately healthy and healthy levels were 443.91 km2 (12.66%, 2438.75 km2 (69.54% and 624.50 km2 (17.81%, respectively. The results could provide useful information for local residents and the government to take measures to improve the health conditions of their township ecosystem.

  2. 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.

  3. 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

  4. 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

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

    Science.gov (United States)

    Hu, Xiao-Ming; Ma, ZhiQiang; Lin, Weili; Zhang, Hongliang; Hu, Jianlin; Wang, Ying; Xu, Xiaobin; Fuentes, Jose D; Xue, Ming

    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 O3 pollution. This study has important implications for understanding the essential meteorological factors for pollution episodes in this region and forecasting these severe events.

  6. 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.

  7. 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

  8. 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.

  9. A comparison of OSL ages derived from silt-sized quartz and polymineral grains from Chinese loess

    Science.gov (United States)

    Watanuki, T.; Murray, A. S.; Tsukamoto, S.

    2003-05-01

    Recent work (Watanuki et al., submitted) has shown by comparison with independent age control that silt-sized quartz grains extracted from Japanese loess can be used for optically stimulated luminescence (OSL) dating for equivalent doses of up to 425 Gy (˜500 ka at these sites). Further comparison with infrared (IR) stimulated and post-IR blue-stimulated OSL showed that the latter signal gave accurate ages, and was probably dominated by quartz, whereas the former systematically underestimated ages in the range 30-600 ka, and showed fading in laboratory tests. The main source of the loess deposits in Japan is the Chinese mainland; in eastern Asia, loess is widely distributed by the prevailing westerly winds, and one of the main sources is in the western desert areas of China. Unfortunately, independent age control is very unusual in loess deposits in China, and there is little evidence for the accuracy of existing luminescence ages from this material. As an alternative approach, this study builds on the Japanese results by using loess from two Chinese sites, and examining the relationship between single-aliquot regeneration dose IR and post-IR blue-stimulated luminescence ages from polymineral samples, and blue-stimulated quartz luminescence ages. The normalized blue-stimulated OSL intensity from quartz from the eastern site was about 10 times that from the west, suggesting either a different source of material, or (less likely) an increase in quartz sensitivity with transport distance. By comparison with quartz results we conclude that, in our samples of Chinese loess, the post-IR blue-stimulated OSL is the more reliable polymineral signal, when compared with the IR signal. It may nevertheless include a feldspar component, and this should be tested for using laboratory fading experiments.

  10. 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.

  11. The dynamic vegetation cover change in Loess Plateau%黄土高原植被覆盖变化动态分析

    Institute of Scientific and Technical Information of China (English)

    刘咏梅; 李京忠; 夏露

    2011-01-01

    目的 对1998-2005年黄土高原植被覆盖变化进行分析.方法 以SPOT VEGETATION S10NDVI为数据源,以月NDVI最大值、NDVI年均值和NDVI变化率为指标,采用时间序列分析方法,阐明黄土高原植被覆盖的时空变化特征.结果 8年间,黄土高原的植被覆盖间或有降低,但植被活动总体呈现增强趋势.结论 植被覆盖变化趋势和气候紧密联系,中西部地区植被增加和减少的区域相互交错,这一特性是由农业生产活动、城市建设、政府决策以及植被对气候变化的响应等综合因素作用的结果.%Aim Analysis on the dynamic vegetation cover change in Loess Plateau from 1998 to 2005. Methods Dynamic changes in Loess Plateau vegetation over 8 years and their spatial patterns were explored, using maximum NDVI per month, mean NDVI per year and NDVI deviation derived from SPOT VEGETATION S10 NDVI as indexes and adopting time-series analysis approach. Results Although significant declines appeared from 1998 to 2001 and from 2004 to 2005, an increasing trend occurred over the past eight years. Conclusion The dynamic vegetation cover is closely coupled with climatic fluctuation, vegetation increased areas and decreased areas are intervened mutually in middle of Loess Plateau, which is caused by agricultural activities, city construction, government policies and the response of vegetation to climate changes.

  12. 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.

  13. Effect of pore water velocities and solute input methods on chloride transport in the undisturbed soil columns of Loess Plateau

    Science.gov (United States)

    Zhou, BeiBei; Wang, QuanJiu

    2016-04-01

    Studies on solute transport under different pore water velocity and solute input methods in undisturbed soil could play instructive roles for crop production. Based on the experiments in the laboratory, the effect of solute input methods with small pulse input and large pulse input, as well as four pore water velocities, on chloride transport in the undisturbed soil columns obtained from the Loess Plateau under controlled condition was studied. Chloride breakthrough curves (BTCs) were generated using the miscible displacement method under water-saturated, steady flow conditions. Using the 0.15 mol L-1 CaCl2 solution as a tracer, a small pulse (0.1 pore volumes) was first induced, and then, after all the solution was wash off, a large pulse (0.5 pore volumes) was conducted. The convection-dispersion equation (CDE) and the two-region model (T-R) were used to describe the BTCs, and their prediction accuracies and fitted parameters were compared as well. All the BTCs obtained for the different input methods and the four pore water velocities were all smooth. However, the shapes of the BTCs varied greatly; small pulse inputs resulted in more rapid attainment of peak values that appeared earlier with increases in pore water velocity, whereas large pulse inputs resulted in an opposite trend. Both models could fit the experimental data well, but the prediction accuracy of the T-R was better. The values of the dispersivity, λ, calculated from the dispersion coefficient obtained from the CDE were about one order of magnitude larger than those calculated from the dispersion coefficient given by the T-R, but the calculated Peclet number, Pe, was lower. The mobile-immobile partition coefficient, β, decreased, while the mass exchange coefficient increased with increases in pore water velocity.

  14. Analysis of baseflow index based hydrological model in Upper Wei River basin on the Loess Plateau in China

    Science.gov (United States)

    Liu, D.; Chang, J.; Tian, F.; Huang, Q.; Meng, X.

    2015-05-01

    The baseflow is the drainage from the groundwater and soil water to the streamflow. As one important source of the streamflow, the baseflow could be the main source of the streamflow in the dry season. The Wei River, located in the semi-arid region of the Loess Plateau which is overlain by deep and loose soil, is the largest tributary of the Yellow River. According to former research, most of the streamflow in the dry season in the headwater of the Yellow River is baseflow. For the whole Yellow River basin, the baseflow is an important component of the streamflow, and accounts for about 44% of the annual runoff. Physically-based distributed hydrological models can simulate the runoff components separately, and are important tools to analyse the runoff components. Given the importance of the baseflow in the dry season for drought relief to support the ecological water requirement and irrigation, especially in the Wei River, the baseflow is analysed in this study. To investigate the baseflow in the Upper Wei River basin, a semi-distributed hydrological model based on a Representative Elementary Watershed approach (THREW) is employed to investigate the runoff generation process. To compare the results, an automatic baseflow separation method proposed by Arnold is used to separate the baseflow from the daily streamflow at Beidao hydrological station in Upper Wei River basin from 2001 to 2004. Based on the hydrological modelling and the Arnold separation method, the average annual baseflow index, i.e. the ratio of baseflow to the total runoff, is estimated as in the range of 0.30-0.36. The average intra-annual monthly baseflow index represents the seasonality of the baseflow due to the seasonality of the precipitation and evapotranspiration, and is also analysed.

  15. 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.

  16. Nutrient distribution and accumulation patterns of natural secondary forests in the Loess Plateau of Shanxi Province, northern China

    Institute of Scientific and Technical Information of China (English)

    Xiaojuan ZHANG; Tianxing WEI; Libo JING; Na YIN; Yanhui LIU

    2009-01-01

    We studied the biomass and its allocation in natural secondary forests, as well as the amounts, accumulation and distribution of nutrient elements (N, P, K, Ca and Mg) in sample plots established in the Loess Plateau in Shanxi Province, northern China. The results show that biomass in natural secondary forests amounted to 36.09 t/hm2,. of which the tree layer accounted for 46%, the shrub layer for 29%, the herb layer for 13% and the litter layer for 12%. The total storage of the five nutrient elements is 1089.82 kg/hm2. Nutrient storage in the tree layer is the largest, at 41%. The sequence of storage of the elements varied among different layers and is given as follows: shrub layer 31.27%, herb layer 12.55% and litter layer 15.36%. The accumulation of nutrient elements in the tree layer, ordered from high to low, is: branches > roots > stems > bark > leaves. The total storage of the five nutrient elements in the soil is 634.97 t/hm2, where the accumulation of the nutrients accounts for 95.32% (N), 99.64% (P), 99.91% (K), 99.84% (Ca) and 99.95% (Mg) of the total amounts. The accumulation coefficients of different organs in the tree layer are, from high to low: leaves > branches > roots > bark > stems. The accumulation coefficients in the different layers are listed as follows: shrub layer > tree layer > herb layer and for the elements as: N > P > Ca > K > Mg.

  17. 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.

  18. Impact of soil moisture and winter wheat height from the Loess Plateau in Northwest China on surface spectral albedo

    Science.gov (United States)

    Li, Zhenchao; Yang, Jiaxi; Gao, Xiaoqing; Zheng, Zhiyuan; Yu, Ye; Hou, Xuhong; Wei, Zhigang

    2016-12-01

    The understanding of surface spectral radiation and reflected radiation characteristics of different surfaces in different climate zones aids in the interpretation of regional surface energy transfers and the development of land surface models. This study analysed surface spectral radiation variations and corresponding surface albedo characteristics at different wavelengths as well as the relationship between 5-cm soil moisture and surface albedo on typical sunny days during the winter wheat growth period. The analysis was conducted using observational Loess Plateau winter wheat data from 2015. The results show that the ratio of atmospheric downward radiation to global radiation on typical sunny days is highest for near-infrared wavelengths, followed by visible wavelengths and ultraviolet wavelengths, with values of 57.3, 38.7 and 4.0%, respectively. The ratio of reflected spectral radiation to global radiation varies based on land surface type. The visible radiation reflected by vegetated surfaces is far less than that reflected by bare ground, with surface albedos of 0.045 and 0.27, respectively. Thus, vegetated surfaces absorb more visible radiation than bare ground. The atmospheric downward spectral radiation to global radiation diurnal variation ratios vary for near-infrared wavelengths versus visible and ultraviolet wavelengths on typical sunny days. The near-infrared wavelengths ratio is higher in the morning and evening and lower at noon. The visible and ultraviolet wavelengths ratios are lower in the morning and evening and higher at noon. Visible and ultraviolet wavelength surface albedo is affected by 5-cm soil moisture, demonstrating a significant negative correlation. Excluding near-infrared wavelengths, correlations between surface albedo and 5-cm soil moisture pass the 99% confidence test at each wavelength. The correlation with 5-cm soil moisture is more significant at shorter wavelengths. However, this study obtained surface spectral radiation

  19. [Growth process and diameter structure of Pinus tabulaeformis forest for soil and water conservation in Loess Plateau Hilly regions].

    Science.gov (United States)

    Zhang, Guang-Can; Liu, Xia; Zhou, Ze-Fu; Zhang, Shu-Yong; Liu, Gang; Chen, Jian

    2007-04-01

    Through stem analysis of sample trees, the biomass, growth process, and diameter structure of two 21 years old Pinus tabulaeformis forests growing on the shady and sunny slopes in Loess Plateau hilly and gully regions were investigated. The results showed that there were distinct differences between these two forests in their tree height, diameter at breast height (DBH), and timber volume. The forest biomass, growth status, and diameter structure on shady slope were superior to those on sunny slope. The fast-growing period of tree height all appeared in the period of 9-13 years, and after 13 years, the annual increment of tree height was larger in shady slope forest than in sunny slope forest, with the increment in the 21st year being 0.26 and 0.1, respectively. The DBH growth of the two forests was declined greatly after 13 years, but the decrement was obviously less in shady slope forest than in sunny slope forest. After 17 years, the annual increment of DBH growth was larger in shady slope forest than in sunny slope forest, with the values being 0.46 cm x a(-1) and 0.27 cm x a(-1), respectively in the 21st year. Before 13 years, there was little difference in the increment of timber production between the two forests, but the increment after 13 years was larger in shady slope forest than in sunny slope forest, with the values of 0.0023 m3 and 0.0015 m3, respectively in the 21st year. The summit of DBH distribution curve was all partial to left, but the skewness of shady slope forest (SK = 0.75) was lower than that of sunny slope forest (SK = 1.03), and the kurtosis of shady slope forest (K = 1.05) was higher than that of sunny slope forest (K = 0.94), indicating that sunny slope forest had a larger stand density than shady slope forest.

  20. [Characteristics of soil organic carbon and enzyme activities in soil aggregates under different vegetation zones on the Loess Plateau].

    Science.gov (United States)

    Li, Xin; Ma, Rui-ping; An, Shao-shan; Zeng, Quan-chao; Li, Ya-yun

    2015-08-01

    In order to explore the distribution characteristics of organic carbon of different forms and the active enzymes in soil aggregates with different particle sizes, soil samples were chosen from forest zone, forest-grass zone and grass zone in the Yanhe watershed of Loess Plateau to study the content of organic carbon, easily oxidized carbon, and humus carbon, and the activities of cellulase, β-D-glucosidase, sucrose, urease and peroxidase, as well as the relations between the soil aggregates carbon and its components with the active soil enzymes were also analyzed. It was showed that the content of organic carbon and its components were in order of forest zone > grass zone > forest-grass zone, and the contents of three forms of organic carbon were the highest in the diameter group of 0.25-2 mm. The content of organic carbon and its components, as well as the activities of soil enzymes were higher in the soil layer of 0-10 cm than those in the 10-20 cm soil layer of different vegetation zones. The activities of cellulase, β-D-glucosidase, sucrose and urease were in order of forest zone > grass zone > forest-grass zone. The peroxidase activity was in order of forest zone > forest-grass zone > grass zone. The activities of various soil enzymes increased with the decreasing soil particle diameter in the three vegetation zones. The activities of cellulose, peroxidase, sucrose and urease had significant positive correlations with the contents of various forms of organic carbon in the soil aggregates.

  1. 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

  2. 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.

  3. 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℃.

  4. 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

  5. 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.

  6. Optimization of Land Use Pattern Reduces Surface Runoff and Sediment Loss in a Hilly-Gully Watershed at the Loess Plateau, China

    Directory of Open Access Journals (Sweden)

    Han Yini

    2016-04-01

    Full Text Available Aim of study: The aim is to find a way increasing gain yield and lessen area of farmland, and then increasing vegetation cover, improving environment and alleviating soil erosion.Area of study: The Hilly-Gully region at the loess plateau of China.Material and methods: In this study, an adjusted and optimized land use pattern was developed in Luoyugou watershed in the Yellow River valley based on the gradient distribution of land use types, and its effect on water and sediment transport was simulated using the SWAT model and GIS, with remote sensing images, land use maps and hydrologic data.Main results: The results indicate: average simulated runoff and sediment for the period 1986-2000 under conditions of the three land use pattern (2011, 2008 and optimized land use reduced by 0.002-0.013 m3/s (2.7-17.6% and 0.66 million tons, respectively. The runoff and sediment data obtained were compared with observed data from 2008, which showed that runoff and sediment production would be reduced by 467625 m3 and 22754 tons, respectively.Research highlights: The adjustment of the land use pattern in comprehensive consideration of vegetation and geography have a positive effect on water and sediment transport which will be important for decision making and water resources management, and provides a reference for future environmental management and ecological construction in the loess plateau Hilly-Gully region. 

  7. Soil temperature and moisture sensitivities of soil CO2 efflux before and after tillage in a wheat field of Loess Plateau, China.

    Science.gov (United States)

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

    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 efflux (SCE) to soil temperature and moisture. Using a multi-channel automated CO2 efflux 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 tillage-induced increase in SCE might partially be attributed to the increases in temperature and moisture sensitivity of SCE.

  8. 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.

  9. 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.

  10. [Effects of mulching patterns on soil water, broomcorn millet growth, photosynthetic charac- teristics and yield in the dryland of Loess Plateau in China].

    Science.gov (United States)

    Su, Wang; Zhang, Yan-Ping; Qu, Yang; Li, Cui; Miao, Jia-Yuan; Gao, Xiao-Li; Liu, Jian-Hua; Feng, Bai-Li

    2014-11-01

    The objective of this study was to explore the effects of mulching patterns on soil water, growth, photosynthetic characteristics, grain yield and water use efficiency (WUE) of broomcorn millet in the dryland of Loess Plateau in China. In a three-year field experiment from 2011 to 2013, we compared four different mulching patterns with traditional plat planting (no mulching) as the control (CK). The mulching patterns included W ridge covered with common plastic film + intredune covered with straw (SG), common ridge covered with common plastic film + intredune covered with straw (LM), double ridges covered with common plastic film + intredune covered with straw (QM), and the traditional plat planting covered with straw (JG). The results showed that the soil water storage in 0-100 cm layer was significantly higher in all mulching patterns than in CK, particularly in SG then followed by LM, QM and JG, and the differences among the mulching patterns reached a significant level at the different growth stages of broomcorn millet. Among all mulching patterns, SG had the greatest effect on the growth and photosynthesis of broomcorn millet, respectively increasing the yield and WUE by 55.9% and 64.9% over CK, and the differences among the mulching patterns also reached a significant level. Therefore, SG was recommended as an efficient planting pattern for broomcorn millet production in the dryland of Loess Plateau in China.

  11. [Effects of land use and environmental factors on the variability of soil quality indicators in hilly Loess Plateau region of China].

    Science.gov (United States)

    Xu, Ming-Xiang; Liu, Guo-Bin; Zhao, Yun-Ge

    2011-02-01

    Classical statistics methods were adopted to analyze the soil quality variability, its affecting factors, and affecting degree at a regional scale (700 km2) in the central part of hilly Loess Plateau region of China. There existed great differences in the variability of test soil quality indicators. Soil pH, structural coefficient, silt content, specific gravity, bulk density, total porosity, capillary porosity, and catalase activity were the indicators with weak variability; soil nutrients (N, P, and K) contents, CaCO3 content, cation exchange capacity (CEC), clay content, micro-aggregate mean mass diameter, aggregate mean mass diameter, water-stable aggregates, respiration rate, microbial quotient, invertase and phosphatase activities, respiratory quotient, and microbial carbon and nitrogen showed medium variation; while soil labile organic carbon and phosphorus contents, erosion-resistance, permeability coefficient, and urease activity were the indicators with strong variability. The variability of soil CaCO3, total P and K, CEC, texture, and specific gravity, etc. was correlated with topography and other environmental factors, while the variability of dynamic soil quality indicators, including soil organic matter content, nitrogen content, water-stable aggregates, permeability, microbial biomass carbon and nitrogen, enzyme activities, and respiration rate, was mainly correlated with land use type. Overall, land use pattern explained 97% of the variability of soil quality indicators in the region. It was suggested that in the evaluation of soil quality in hilly Loess Plateau region, land use type and environmental factors should be fully considered.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Ningwu——An Ancient Pass On The Plateau

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正>Ningwu situated on the Loess Plateau in north of Shanxi Province is one of the three passes along the Great Wall. The other two are the Pian Pass in the west and the Yanmen Pass in the east. In the ancient times, it had been a key military town in the northern Chinese borders.

  19. 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

  20. [Dynamic monitoring of ecological environment in loess hilly and gully region of Loess Plateau based on remote sensing: A case study on Fuxian County in Shaanxi Province. Northwest China].

    Science.gov (United States)

    Li, Fen-ling; Chang, Qin-rui; Shen, Jian; Liu, Jing

    2015-12-01

    Based on the principal component analysis (PCA), four ecological evaluation indicators including vegetation index, wet index, land surface temperature and soil index were combined to evaluate the ecological environment quality of Fuxian County in hilly and gully area of Loess Plateau from year 1995 to 2014. The results showed that the RSEI integrated RS and PCA method could reveal regional ecological changes objectively and quantitatively. The level of overall regional ecological status in Fuxian County was good with a high vegetation fraction and rich biodiversity. The synthetical ecological environment quality index increased from 3.17 to 3.53 indicating the ecological environment had been improved greatly in recent 20 years. The area with best ecological environment quality was located in Niuwu town. The magnitude of change increased progressively from northwest to southeast, and the biggest change occurred in Jiaodao and Nandaode towns. From 1995 to 2014, the areas with decreased and increased ecological environment quality were 16.7% and 42.7% of the study area, respectively, and the improved regions were mainly distributed in plateau and hilly area in the center, rocky low mountainous area in northeast and the Ziwuling Nature Reserve area in southwest of the county.

  1. 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.

  2. Contribution analysis of the long-term changes in seasonal runoff on the Loess Plateau, China, using eight Budyko-based methods

    Science.gov (United States)

    Wu, Jingwen; Miao, Chiyuan; Wang, Yamei; Duan, Qingyun; Zhang, Xiaoming

    2017-02-01

    Over the last five decades, runoff from the Loess Plateau has greatly decreased because of changes in the climate and intensive human activities. Comprehending and distinguishing the relative impacts of climate change and human activities on runoff is essential to adapt water-resource management and soil-and-water conservation projects to climate change. In this study, we used a technique involving integrated climate elasticity and eight Budyko-based methods to assess the relative impacts of climate change and human activities on runoff changes during high-flow and low-flow seasons in 17 catchments across the Loess Plateau during the period of 1961-2013. The results showed that, on average, runoff in the high-flow season exhibited a significant downward trend in 15/17 catchments, with an average decrease of 0.63 mm/yr. In contrast, the decrease was 0.29 mm/yr for the low-flow season. We also found that changes in runoff were more sensitive to variations in precipitation than variations in potential evapotranspiration, in both high-flow and low-flow seasons. The quantitative contributions from climate change and human activities as calculated by the eight Budyko-based methods were relatively similar during the high-flow season, but varied across catchments in the low-flow season. The results showed that, during the high-flow season, human activities had a greater impact on runoff changes than climate change, accounting for about 73% of the total decrease. However, in the low-flow season, which exhibits significantly increased potential evapotranspiration (p human activities. The discrepancies between the results obtained via eight Budyko-based methods and the resulting uncertainties in the quantitative attributions are also discussed.

  3. 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.

  4. 黄土高原黄土的成因:沙尘气溶胶源汇模拟与黄土堆积%The causes of loess formation over Loess Plateau:simulated dust aerosol sources and sinks and loess accumulation

    Institute of Scientific and Technical Information of China (English)

    刘唯佳; 韩永翔; 赵天良

    2014-01-01

    黄土高原是重要的降尘区还是沙尘源区这一科学问题至今未有确切定论.本文利用北半球气溶胶区域气候模式 NARCM,根据1995~2004年10a的模拟数据,分析了中国区域沙尘起沙量、沉降量以及沙尘的盈亏空间分布及风场,得到如下结论:1)沙漠及沙漠化地区是起沙量最大的区域、沉降量高值区集中在沙漠、沙漠化地区及其下风方向.黄土高原起沙量很小,而沉降量远大于起沙量.2)沙尘源区是沙漠及沙漠化地区,其余的地区则是沙尘汇区,降尘量由西北向东南递减.3)黄土高原因太行山和秦岭阻挡,处在最大的沙尘汇区.黄土高原的黄土是冰期和间冰期交替、经过漫长年代沙尘沉降的结果,模拟分析结论为黄土的风成学说提供了有力的证据.%There is a scientific debate argument whether Loess Plateau is an important region of dust aerosol sinks or sources. Based on the 10-year (1995~2004) aerosol simulations of the northern aerosol regional climate model NARCM, the spatial distribution of dust aerosol emissions, depositions and budgets as well as wind field were analyzed. The simulation analysis showed 1) the highest dust emissions appeared in the desert and desertification areas, while the highest dust depositions were concentrated over the desert and desertification areas as well as their immediately downwind region.The dust depositions largely exceeded the dust aerosol emission in Loess Plateau with the low dust emissions. 2) Desert and desertification area were the main dust sources, the rest of areas were dust sinks. Dust depositions declined from the northwest to the Southeast.3) Due to the barrier of the Taihang and Qinling Mountains, the Loess Plateau was the largest dust sink region with the highest depositions. The loess over Loess Plateau was accumulated by dust depositions over the long term evolution of glacial and interglacial periods. The dust aerosol simulation provided a solid

  5. 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.

  6. Rock magnetic investigation of loess deposits in the Eastern Qingling Mountains (central China) and its implications for the environment of early humans

    Science.gov (United States)

    Wang, Xiaoyong; Lu, Huayu; Zhang, Weiguo; Hu, Pengxiang; Zhang, Hongyan; Han, Zhiyong; Wang, Shejiang; Li, Baoguo

    2016-11-01

    The Luonan Basin, located in the transitional zone between temperate and subtropical China, is an important locality for human evolution during the early to middle Pleistocene. The loess deposits in the Luonan Basin contain numerous in situ lithic artefacts; the deposits also constitute suitable material for dating the artefacts and are potentially useful for reconstructing the climatic fluctuations which is important for studying the adaptation and occupation of the area by early humans. We carried out a combined rock magnetic and geochemical investigation of a loess sequence from the Liuwan Palaeolithic site in the Luonan Basin. The results indicate a mixture of magnetic minerals, including magnetite/maghemite and hematite/goethite. Magnetic susceptibility was used as a palaeoclimate proxy on the Chinese Loess Plateau; however, its application to the Luonan Basin may be problematic because the provenance of the loess parent material, as well as the depositional environment, differs from that of the Chinese Loess Plateau. We found that rock magnetic parameters related to the grain size of magnetic minerals, such as SIRM/χ and χARM/SIRM, are better palaeoclimatic indicators than magnetic susceptibility. Overall, the magnetic results, together with the results of bulk grain-size and chemical index of alteration, indicate that the interglacial environment of early humans in Luonan Basin was warmer and more humid than the coeval environment of the Chinese Loess Plateau.

  7. 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

  8. Oxygen isotope signatures of quartz from major Asian dust sources: Implications for changes in the provenance of Chinese loess

    Science.gov (United States)

    Yan, Yan; Sun, Youbin; Chen, Hongyun; Ma, Long

    2014-08-01

    We present a systematic investigation of the oxygen isotopic composition of quartz in both fine and coarse fractions (values of both the fine and coarse fractions from the various sources are overlapped to varying degrees, thus making it difficult to differentiate them. Nevertheless, the quartz δ18O values of both fractions exhibit an increasing trend from the Mongolian Gobi, to the northern Chinese deserts, and then to the Taklimakan desert. This implies that the geological settings of the source areas are different, which in turn results in differing contributions of high-temperature igneous rocks. The combination of quartz δ18O results with other quartz-based provenance tracers can clearly differentiate the three major source areas, i.e., the Taklimakan desert, the Mongolian Gobi, and the northern Chinese deserts. In addition, comparison of our results with previous δ18O measurements of fine-grained quartz from the Luochuan loess sequence suggests the likely glacial-interglacial fluctuations in dust provenance. Finally, we suggest that the combination of quartz δ18O signatures and other dust provenance tracers can potentially improve the recognition of long-term fluctuations in the provenance of Chinese loess-red clay deposits.

  9. 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.

  10. 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

  11. 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

  12. 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

  13. Grain size distribution of quartz isolated from Chinese loess/paleosol

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Grain size distribution of bulk loess-paleosol and quartz chemically extracted from the loess/paleosol shows that mean size of the bulk samples is always finer than that of the quartz. The original aeolian depositions have been modified to various degrees by post-depositional weathering and pedogenic processes. The grain size distribution of the isolated quartz should be close to that of the primary aeolian sediment because the chemical pretreatment excludes secondary produced minerals. Therefore, the grain size of the quartz may be considered to more clearly reflect the variations of winter monsoon intensity.

  14. Research progress in erosion-type nonpoint source poLLution process simuLationof the Loess PLateau%黄土高原水土流失型非点源污染过程模拟研究进展

    Institute of Scientific and Technical Information of China (English)

    吴磊; 马孝义

    2015-01-01

    Loss of nitrogen and phosphorus in soil and water loss area of the Loess Plateau not only reduces the utilization rate of fertilizer,but also is a potential threat to aquatic environments.This study takes the typicality of soil and nutrient loss in the Lo-ess Plateau Region as a starting point to deeply analyse and systematically summarize the basic status of the Loss Plateau,the re-search progress of hydrological process,soil erosion,erosion-type nonpoint source pollution and its control strategies of the Loess Plateau.Aiming at the few existing studies on the Loess Plateau,the key research directions of nonpoint source pollution in the Loess Plateau for the future were proposed,such as the loss mechanism of nonpoint source pollution,the load estimation method of nonpoint source pollution in the Loess Plateau,the coupled model of water,sediment and pollution in the Loess Plateau,the combined application of 3S technology and control strategies of erosion-type nonpoint source pollution in the Loess Plateau etc.This re-sult may provide reference for studying the modeling process of erosion-type nonpoint source pollution in the Loess Plateau.%黄土高原严重的水土流失造成了土壤氮磷流失,不仅降低了化肥的利用率,而且对水环境造成了潜在威胁。从黄土高原区水土与养分流失的典型性入手,剖析和总结了黄土高原区基本概况、水文过程、土壤侵蚀、水土流失型非点源污染过程模拟及防控策略等的研究进展。针对目前黄土高原区尤其是黄土丘陵沟壑区非点源污染研究较少,提出了未来黄土高原地区非点源污染的研究方向与建议:黄土区非点源污染物流失机理,非点源污染负荷估算方法,流域水、沙、污染物耦合模型以及3S 技术与流域非点源污染防控决策耦合应用等。

  15. 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.

  16. [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 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.

  17. 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.

  18. 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

  19. [Simulation on the restoration effect of soil moisture in alfalfa (Medicago sativa)-grain rotation system in semi-arid and drought-prone regions of Loess Plateau].

    Science.gov (United States)

    Wang, Xue-Chun; Li, Jun; Fang, Xin-Yu; Sun, Jian; Tahir, Muhammad Naveed

    2011-01-01

    With the combination of field survey and EPIC modeling, this paper simulated the restoration effect of soil moisture in different alfalfa (Medicago sativa)-grain rotation systems in semi-arid and drought-prone regions of Loess Plateau. In perennial alfalfa field and in grain crop field after alfalfa, the correlation coefficients between the simulated and observed values of soil moisture content in 0-10 m layer were larger than 0.9 (P alfalfa field. During the cultivation of alfalfa, the soil moisture content in the layers at 8-10 m depth should not be less than 5.7%. Considering the sustainable development of agricultural production, the appropriate cultivation duration of alfalfa should be 4-6 years and no more than 8 years. For the restoration of soil moisture after alfalfa cultivation in the study regions, the rotation system potato (Solanum tuberosum) --> potato --> spring wheat (Triticum aestivum) could be adopted, and alfalfa could be cultivated again after 32-33 years.

  20. Spatial distribution of surface rock fragment on hillslopes in a small catchment in wind-water erosion crisscross region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The cover and size distributions of surface rock fragment in hillslopes were investigated by using digital photographing and treating technique in a small catchment in wind-water erosion crisscross region of the Loess Plateau. The results indicated that the maximal cover of rock fragment was pre-sented at mid-position in steep hillslope. Rock fragment presented a general decreasing-trend along the hillslope in gentle hillslope. Rock fragment cover was positively related to gradient, rock fragment size decreased generally along the hillslope, and the size reduced with the gradient. The mean size of rock fragment was at a range of 6―20 mm in the steep hillslope, rock fragment size > 50 mm was rarely presented. The covers of rock fragment at different positions were markedly related to the quantities of rock fragment < 40 mm. The area of rock fragment of 2―50 mm accounted for 60% or more of the total area, dominating the distribution of rock fragment in the hillslopes.

  1. 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.

  2. 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.

  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. 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.

  5. 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.

  6. [Biological soil crust nitrogenase activity and its responses to hydro-thermic factors in different erosion regions on the Loess Plateau, China].

    Science.gov (United States)

    Ming, Jiao; Zhao, Yun-Ge; Xu, Ming-Xiang; Yang, Li-Na; Wang, Ai-Guo

    2013-07-01

    Based on field survey, the biological soil crusts at their stable development stage were collected from the water erosion region, water-wind erosion region, and wind erosion region on the Loess Plateau, aimed to study the effects of the variations of moisture and temperature on the crusts nitrogenase activity (NA). The NA of the crusts in the erosion regions decreased in the order of water erosion region (127.7 micromol x m(-2) x h(-1)) > water-wind erosion region (34.6 micromol x m(-2) x h(-1)) > wind erosion region (6.0 micromol x m(-2) x h(-1)), and the optimal temperature for the crust nitrogen fixation was 35 degrees C, 25 degrees C, and 15 degrees C, respectively. At the optimal temperature and 100% -40% field water-holding capacity, the NA of the crusts from the water erosion and water-wind erosion regions had no significant difference. The NA of the crusts from the wind erosion region was more sensitive to the variation of moisture, showing a dramatic decline when the moisture decreased to 80% field water-holding capacity, and totally lost when the moisture decreased to 20% field water-holding capacity. The differences in the NA of the crusts from the three erosion regions and the responses of the NA to the variations of moisture and temperature were likely associated with the climate, environment, and the crust species composition.

  7. 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.

  8. [Characteristics of Soil Respiration along Eroded Sloping Land with Different SOC Background on the Hilly Loess Plateau].

    Science.gov (United States)

    Chen, Gai; Xu, Ming-xiang; Zhang, Ya-feng; Wang, Chao-hua; Fan, Hui-min; Wang, Shan-shan

    2015-09-01

    This study aimed to characterize soil respiration along eroded sloping land at erosion and deposition area under different soil organic carbon(SOC) levels, and linked the relationship between soil respiration and soil temperature, soil moisture, SOC and slope position. Experiments were carried out in the plots of S type slopes include five different soil organic carbon levels in the Loess Hilly Region. The S type slopes were divided into control area at the top of the slope, erosion area at the middle of the slope and deposition area at the toe of the slope. We found that soil temperature had a greater impact on soil respiration in the deposition area, whereas soil moisture had a greater impact on soil respiration in the erosion area compared among control area, erosion area and deposition area. In addition, SOC was the most important factor affecting soil respiration, which can explain soil respiration variation 54. 72%, followed by soil moisture, slope position and soil temperature, which explain soil respiration variation 18. 86% , 16. 13% and 10. 29%, respectively. Soil respiration response to erosion showed obvious on-site and off-site effects along the eroded sloping land. Soil respiration in the erosion area was reduced by 21. 14% compared with control area, and soil respiration in the deposition area was increased by 21. 93% compared with control area. Erosion effect on source and sink of carbon emission was correlated with SOC content of the eroded sloping land. When SOC content was higher than 6. 82 g.kg-1, the slope. erosion tended to be a carbon sequestration process, and when SOC content was lower than 3.03 g.kg-1, the slope erosion tended to be a process of the carbon emission source. The model could reflect the relationship between soil respiration and independent variables of soil organic carbon content, soil temperature and moisture.

  9. 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

  10. [Effects of soil moisture before sowing and nitrogen fertilization on winter wheat yield and water use on Weibei Plain of Loess Plateau].

    Science.gov (United States)

    Meng, Xiao-Yu; Wang, Zhao-Hui; Li, Fu-Cui; Li, Ke-Yi; Xue, Cheng; Li, Sheng-Xiu

    2012-02-01

    A five-year site-specific experiment was carried out on the Weibei Plain of Loess Plateau in Shaanxi Province of northwestern China to study the effects of soil moisture regime before sowing (SMBS) and nitrogen fertilization on the grain yield and water use of winter wheat. On the basis of applying 100 kg x hm(-2) of P2O5, five nitrogen fertilization levels (0, 80, 160, 240, and 320 kg N x hm(-2)) were installed, and took the precipitation in the five years into consideration. In the study area, there was a linear correlation between the precipitation in summer (from July to September) and the SMBS, with an increment of 0.6 mm SMBS per 1 mm precipitation. For a stable or high wheat yield, the SMBS should be kept around 550 mm, and the precipitation in summer should be around 370-390 mm. In the years with adequate precipitation (> 386 mm) in summer, the SMBS in present winter wheat growth season less decreased by the increase of the nitrogen fertilization rate in previous growth season. However, in the years with less precipitation in summer (nitrogen fertilization rate in previous growth season was increased by each 100 kg N x hm(-2). In addition to SMBS, adequate precipitation in key growth stages was another important factor to ensure the wheat yield in dryland area because 1 mm SMBS could produce 10.6-11.4 kg x hm(-2) of wheat grain, and 1 mm precipitation occurred in the key growth stages could lead to more grain yield as high as 30.6-33.1 kg x hm(-2). Variation analysis showed that nitrogen fertilization rate affected the utilization degree of SMBS by winter wheat, while SMBS controlled the allocation and transportation of dry matter from vegetative parts to grain.

  11. 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.

  12. 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.

  13. 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).

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

    Science.gov (United States)

    Gong, Daozhi; Hao, Weiping; Mei, Xurong; Gao, Xiang; Liu, Qi; Caylor, Kelly

    2015-01-01

    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.

  19. 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.

  20. Differential Effects of Legume Species on the Recovery of Soil Microbial Communities, and Carbon and Nitrogen Contents, in Abandoned Fields of the Loess Plateau, China

    Science.gov (United States)

    Li, Jin Hua; Jiao, Shu Mei; Gao, Rong Qing; Bardgett, Richard D.

    2012-12-01

    Plant-soil interactions are known to influence a wide range of ecosystem-level functions. Moreover, the recovery of these functions is of importance for the successful restoration of soils that have been degraded through intensive and/or inappropriate land use. Here, we assessed the effect of planting treatments commonly used to accelerate rates of grassland restoration, namely introduction of different legume species Medicago sativa, Astragalus adsurgens, Melilotus suaveolens, on the recovery of soil microbial communities and carbon and nitrogen contents in abandoned fields of the Loess Plateau, China. The results showed effects were species-specific, and either positive, neutral or negative depending on the measure and time-scale. All legumes increased basal respiration and metabolic quotient and had a positive effect on activity and functional diversity of the soil microbial community, measured using Biolog EcoPlate. However, soil under Astragalus adsurgens had the highest activity and functional diversity relative to the other treatments. Soil carbon and nitrogen content and microbial biomass were effectively restored in 3-5 years by introducing Medicago sativa and Astragalus adsurgens into early abandoned fields. Soil carbon and nitrogen content were retarded in 3-5 years and microbial biomass was retarded in the fifth year by introducing Melilotus suaveolens. Overall, the restoration practices of planting legumes can significantly affect soil carbon and nitrogen contents, and the biomass, activity, and functional diversity of soil microbial community. Therefore, we propose certain legume species could be used to accelerate ecological restoration of degraded soils, hence assist in the protection and preservation of the environment.

  1. 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.

  2. 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.

  3. Check dam sediments: an important indicator of the effects of environmental changes on soil erosion in the Loess Plateau in China.

    Science.gov (United States)

    Wang, Yafeng; Chen, Liding; Fu, Bojie; Lü, Yihe

    2014-07-01

    Check dam sediments document the process of soil erosion for a watershed. The main objectives of this research are as follows: first, to determine whether the sediments trapped in check dams can provide useful information about local erosion and the environment, and second, to obtain the extent to which they can be stratigraphically interpreted and correlated to the land use history of an area controlled by check dams. Particle size and the concentration of (137)Cs in sediments are the indicators used to study the effects of environmental changes on soil erosion in the Loess Plateau, China. A total of 216 soil samples were collected from four sediment profile cores at the Yangjuangou watershed check dam constructed in 1955 and fully silted with sediments by 1965. The results indicated that (137)Cs dating and sediment particle size can characterize the sediment deposition process. Silt makes up more than 50 % of the sediment; both the clay and silt sediment fractions decrease gradually in the upstream direction. The sediment profiles are characterized by three depositional layers. These layers suggest changes in the land use. The top layer showed tillage disturbance, with moderate sediments and new soil mixed from 0 to 20 cm. A transition stage from wetlands (characterized by vegetation such as bulrush) to cropland is inferred from sediments at depths of 20-85 cm. Below 85 cm, sedimentary layering is obvious and there is no tillage disturbance. At the downstream site, A0, the average rate of sediment deposition from 1958 to 1963 was approximately 6,125.4 t year(-1) km(-2). Because of their high time resolution, check dam sediments indicate the effects of environmental changes on soil erosion, and they can provide a multiyear record of the soil erosion evolution at the local scale in the middle reaches of the Yellow River.

  4. [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.

  5. 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.

  6. Sanmenxia Loess and Paleoenvironmental Change

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The Caocun(曹村) loess profile of Zhangbianyuan (张汴塬)is located at the southeast margin of the Loess Plateau,Which is a typical representative of loess stratum in the Sanmenxia(三门峡) area.In the 145 m thick profile,a loess-paleosol sequence occurs from L1 to L33,underlain by a red clay bed.The B/M boundary was recorded at the bottom of L7, the Jaramillo event at S11 to S12, the Olduval event at L23 to L26 , and the M/G boundary at the bottom of L33 near the red clay.The magnetic susceptibility of the loess deposits, as well as the carbonate and granularity components, indicates that there have been many periodic paleoclimate changes, including a total of 13 cold events that each lasted more than 40 000 a.A high-resolution chronostratigraphic profile has been established using an age model according to grain characteristics.A clear correlation exists between records of the paleomonsoon in the Caocun loess succession and SPECMAP from 3 × 105 a B.P.to the present.The Caocun profile can act as a control site in the southeastern Loess Plateau.Its paleoenvironmental records relate to eastern Asian paleomonsoon theory.

  7. 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.

  8. 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.

  9. 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...... dependence of De on first IR stimulation temperature between 50 and 260 °C suggesting negligible signal fading. Resultant ages are consistent with a last interglacial age (~130 to ~75 ka) and are also consistent within errors with continuous linear sedimentation rates. The average mass accumulation rate...... 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...

  10. Research On Granary Design In The Loess Plateau--Fengtuyicang In Shaanxi Province For Example%黄土高原粮仓建筑的设计研究--以陕西丰图义仓为例

    Institute of Scientific and Technical Information of China (English)

    石英; 汪俊旭

    2013-01-01

    According to the analysis of the granary in the loess plateau what is in the agrarian age in china. Such as site selection tactic, building-arrangement, the loess plateau thick and heavy envelope, the system of drainage in the thick and heavy envelope. Combining with the Fengtuyicang for example, it has significant meaning for development and construction of Modern granary which have low defense.%以农耕时代黄土高原粮仓为例,通过对粮仓的选址策略、建筑布局、黄土高原厚重型围护结构、粮仓建筑排水系统的调查,研究发现清末的粮仓不仅在储藏方面,更在防御性方面有着凸显的优势,对现代防御性下降粮仓发展与建设,具有重要的指导意义。

  11. 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.

  12. [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

  13. 黄土高原地区降雨径流理论分析%Theoretical Analysis of the Rainfall and Runoff in Loess Plateau Area

    Institute of Scientific and Technical Information of China (English)

    翟媛

    2015-01-01

    黄河中游河口镇—龙门区间属黄土高原区,是黄河流域水土流失最为严重的地区,也是黄河暴雨的多发区和主要产沙区。该区域的降雨产流方式属于典型的超渗产流,影响产流量和洪峰流量的主要因素是降雨强度,相同的日降雨量,时空分布不同,所产生的洪水量级也不同,不能用月或年的降雨量与径流量的相关关系来分析该区水沙关系的变化。随着水土保持等人类活动的影响,一般降雨情况下的径流量和来沙量明显减少,但当发生稀遇的大暴雨时,该区间仍可能出现大流量高含沙洪水。%Hekouzhen-Longmen reach on the middle reaches of the Yellow River belongs to Loess plateau area. This region is the most serious soil erosion area,as well as the storm and the main sediment producing area. Since this region is the typical runoff generation over infiltration area,the precipitation intensity is the main factor affecting the runoff discharge and peak flow. Due to the different spatial and temporal distributions,the magnitudes of flood vary greatly even under the same daily precipitation,no mention to analyze the relationship of water and sediment using the correlation between monthly or annual precipitation and runoff. The amount of runoff and sediment under general rainfall reduced with the influences of human activities such as soil and water conservation. However,it is still possible to have a big flood with high sediment concentration in this area when rare strong storm happened.

  14. Ecosystem Services and Ecological Restoration in the Northern Shaanxi Loess Plateau, China, in Relation to Climate Fluctuation and Investments in Natural Capital

    Directory of Open Access Journals (Sweden)

    Hejie Wei

    2017-02-01

    Full Text Available Accurately identifying the spatiotemporal variations and driving factors of ecosystem services (ES in ecological restoration is important for ecosystem management and the sustainability of nature conservation strategies. As the Green for Grain project proceeds, food provision, water regulation and climate regulation services in the Northern Shaanxi Loess Plateau (NSLP are changing and have caused broad attention. In this study, the dynamic pattern of the normalized differential vegetation index (NDVI and the main drivers of grain production (GP, water yield (WY and net primary production (NPP in the NSLP from 2000–2013 are identified by incorporating multiple data and methods, in order to provide a better understanding of how and why ES change during ecological restoration. WY was simulated by hydrological modeling, and NPP was estimated with the Carnegie Ames Stanford Approach (CASA model. The results show that vegetation restoration continued from 2000–2013, but fluctuated because of the comprehensive influence of climate and human activity. GP and NPP both exhibited significantly increasing trends, while changes in WY occurred in two stages: decline (2000–2006 and growth (2007–2013. Spatially, significantly increasing trends in NPP and WY were detected in 52.73% and 24.76% of the region, respectively, in areas that correspond with the Green for Grain project and high precipitation growth. Correlation and partial correlation analyses show that there were different dominant factors (i.e., natural vs. anthropogenic driving ES change in the NSLP from 2000–2013. The change in WY was mainly driven by precipitation, while the improvements in GP and NPP can be attributed to investments in natural capital (i.e., chemical fertilizer, agricultural machinery power and afforestation. We also found that vegetation restoration can produce positive effects on NPP, but negative effects on WY by using response analyses of WY or NPP change to NDVI

  15. Potential NDVI in Longxi Loess Plateau based on CART model%基于CART模型陇西黄土高原潜在NDVI模拟

    Institute of Scientific and Technical Information of China (English)

    王超; 戚鹏程; 冯兆东

    2009-01-01

    根据研究区30a的气象观测数据,使用栅格化技术,建成陇西黄土高原分布式气候模型(降水量、气温、蒸散发量);然后以人类活动影响较少的森林、灌木林和十草原作为该处的本底NDVI数据,使用分类与回归树模型建立潜在NDVI与栅格化的气候要素的关系,模拟了陇西黄土高原的潜在NDVI;在此基础上分析了外界压力对潜在NDVI的影响.结果表明:1)陇西黄土高原的多年平均降水量有从东南到西北的递减趋势,气温随海拔高度变化明显,多年平均生长季蒸散发量可达300 mm;2)使用CART模型模拟潜在NDVI精度较高,其总体精度达到了82.6%,可满足潜在NDVI的模拟;3)外界压力下的NDVI与潜在NDVI在空间分布上呈现很大的不一致.%Data from some meteorologic stations were used to build a distributed climate models (precipitation, temperature and evapotranspiration), and then an approach was presented for estimating potential NDVI from climate variables and training data of actual NDVI in nature reserves. The actual data from the baseline generally correspond with land cover types in the western China where there are fewer human activities. The results show: 1) the precipitation had a trend from southeast to northwest, the temperature changed with elevation and the average evapotranspiration reached 30 cm; 2) The CART model was accurate enough in estimating the potential NDVI of Longxi Loess Plateau, with the accuracy reaching 82.6%; 3) There was an great difference between the actual NDVI and potential NDVI.

  16. 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.

  17. Approach to the land-use change and its influential factors in Loess Plateau of Dingxi Prefecture

    Science.gov (United States)

    Yu, Li; Dong, Suocheng; Hou, Xiaoli; Fan, Zhenjun

    2004-11-01

    Based on land-use datum (at scale of 100,000) of the interpretation of Landsat Thematic Mapper in 1980, 1995 and 2000, which came from environmental database of the Chinese Academy of Sciences, the authors investigated land-use change and influential factors by the combined use of geographic information systems (GIS) method, Markov model and canonical correlation analysis (CCA) statistical method. The results showed that, in the periods 1980-2000, crop land increased by 0.58 percent (4278.86 hectares), of which 92.93 percent was transformed from grassland and 7.07 percent from forestland. Urban or built-up land increased by 26.23 percent (687.45 hectares), of which 77.35 percent was transformed from cropland. Rural residential land increased by 5.17 percent (1324.37 hectares). Forestland and water land decreased in area. Grassland decreased by 0.57 percent (5706.77 hectares). Secondly, transition rate of landscape spatial pattern among the landscape elements from 1995 to 2000 was slower than that from 1980 to 1995. Land use types as cropland, grassland, woodland and rural residential land were the primary change types from 1995 to 2000. Thirdly, both natural and social economic factors influenced land use pattern. The population and per capita grain yield were positively correlated to rural residential pattern. The spatial distribution of grassland and cropland showed strong positive correlation to annual rainfall and annual air temperature, and negative association to annual per capita net income of rural residents. The poor annual per capita net income of rural residents and investment in capital construction restricted the extended area of urban build-up land. Therefore, the drought is not proportional to pattern of urban build-up land. The study verified the analysis conclusion of influential factors by redundancy degree of CCA. The integration of remote sensing data, GIS, Markov process and CCA provided a comprehensive method to analyze land use pattern and

  18. 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

  19. Studies on designing the evaluation index system of sustainable development and its application on Loess Plateau%黄土高原可持续发展评价指标体系设计与应用

    Institute of Scientific and Technical Information of China (English)

    崔灵周; 李占斌; 马俊杰; 李勉

    2001-01-01

    通过对黄土高原可持续发展评价指标体系和方法的初步研究,设计出了包括1个高级综合指标--可持续发展综合指数、人口状况等5个基本指标和人口自然增长率等30个元素指标的层次性指标体系结构框架,熵技术支持下确定可持续发展指标权重的层次分析法,以及由递阶多层次综合评价、主成份分析和回归分析等数学方法所集成的可持续发展全面综合评价模型,并以陕北黄土高原为例进行了具体的应用分析与评价。%Based on the pilot studies on the evaluation index system and the method of sustainable development on Loess Plateau,this paper has designed the structure frame of the index system including three types of index including one advanced comprehensive index-the comprehensive index of sustainable development,five basic indexes and thirty element indexes,the Analytic Hierarchy Process which can be used to calculate the sustainable development index weight supported by entropy technology.The model can be used to evaluate the sustainable development of Loess Plateau comprehensively integrated by mathematical method such as compositive appraisement method of hierarchy multilayer、main component analytical method、regression analytical method and so on.Pilot study on the index system has been carried out on the Leoss Plateau of the Northern Shaanxi,and the results is promising.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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

  5. Is a Universal Model for Loess Magnetism / Climate Connection Utopian?

    Science.gov (United States)

    Lagroix, F.; Banerjee, S. K.; Berquó, T. S.; Carvallo, C.; Guyodo, Y.

    2009-05-01

    Pleistocene loess deposition punctuated by periods of soil formation is observed, predominantly at mid- latitudes, over the Asian, European and North American continents. Geoscientists exercising in different disciplines have seized the opportunity handed by loess and paleosol deposits to study the climate of the past from a continental perspective. Paleomagnetists and mineral magnetists have already contributed significantly, most notably from Chinese Loess Plateau sequences. The former provided chronological constraints through the recovery of geomagnetic polarity changes and the latter discovered that roughly 30 nm ferrimagnetic particles were the source of magnetic susceptibility peak values in paleosol. Semi-quantitative models linking magnetic susceptibility to annual precipitation have been proposed but in all cases these are geographically restricted to local or regional models. How can we move forward, beyond the dominantly qualitative and regional models, towards a quantitative and a global model capable of inverting data from loess to paleoclimatic parameters? Is this utopian? The objective of this presentation is two-fold. First, we will take a wide angle look at the question/task at hand. Potential variables to be included are parent material (composition, grain size), post-depositional inputs (organic material, organisms), climate (temperature, moisture, etc.), physical parameters (slope, vegetation, pH, etc.), alteration (neoformation, dissolution, remobilization, recrystallisation). How do current magnetism based models address these different variables? What can we learn from the data, models and approaches of other disciplines such as elemental and isotope geochemistry, sedimentology and pedology? Secondly, we will explore, from the point of view of working with natural sample, the merits of different approaches such as physical and chemical separations. A comprehensive investigation, as outlined above, complemented by a similar systematic

  6. An Observation on Index Variation Characteristics of Extreme Precipitation in Longdong Loess Plateau%观测记录以来陇东黄土塬区极端降水指数变化特征

    Institute of Scientific and Technical Information of China (English)

    张耀宗; 张多勇; 刘艳艳

    2016-01-01

    Based on the historical records and data from the National Meteorological Information Center , this paper reconstructs a precipitation sequence in Longdong Loess Plateau from 1938-2014 and studies the index variation characteristics of extreme precipitation in Longdong Loess Plateau in the past 77 years according to the eleven extreme precipitation index issued by World Meteorological Organization .The re-sults are as follows:1 ) .Precipitation variation in Longdong Loess Plateau experienced three stages from 1938 to 2014.On the whole, there is a weak increasing trend;2).There is a decreasing trend in the five precipitation index , and the most significant decrease exists in heavy precipitation ( R95 ); 3 ) . There is an increasing trend in the average daily precipitation R 10, R20 and CWD, while CDD and R50 are in a decreased trend; 4 ) .There is a weak increasing trend in precipitation intensity index .The differences of each index were significant in different stages which have different contribution to extreme precipitation in Longdong Loess Plateau .The results can provide reference for water conservancy project , water and soil conservation , and disaster prevention and reduction as well .%基于历史记录资料和国家气象信息中心气象资料重建了1938-2014年陇东黄土塬区日降水序列。通过 WMO推荐的11个极端降水指标研究了近77年以来陇东黄土塬区极端降水变化的特征。结果表明:①1938-2014年陇东黄土塬区降水微弱增加(0.07mm/10a),经历了明显减少(1938-1955)———微弱减少(1956-1993)———显著增加(1994-2014)3个阶段的变化。②5个降水量指数整体呈减少趋势,其中强降水量( R95)减少最显著。③降水日数指数中 CWD、R10、R20呈增加趋势,CDD 与 R50为减少趋势。④降水强度指数呈微弱减少趋势。但不同阶段各指数变化差异较大,对陇东黄土塬区极端降水贡献存在差异

  7. 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.

  8. [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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Composition, Susceptibility and Input Flux of Present Aeolian Dust Over Loess Plateau of China%黄土高原现代天然降尘的组成、通量和磁化率

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Present aeolian dust is collected at 7 sites in different partsof the Loess Plateau of China. Investigation on the composition indicates that mineral dust makes up the dominant part of the dust. Magnetic susceptibility of the dust varies in range of 80~150 units (10-8m3/kg), which is higher than that of glacial loess. The high susceptibility of present dust implies that original material of dust has been modified to certain extent by climatic condition. Seasonal variability of dust input flux exhibits a gentle decrease from northwest to southeast with strong seasonal variety in the northern margin of the Loess Plateau. Accumulated input flux of the dust remains consistent over most regions except for northern part where possesses obvious high input flux. Meteorological analysis on transportation and deposition process reveals that most dust material is produced in non-storm deposition rather than in dust storm deposition. Aeolian dust is mainly transported by low level winds in step-wise way to deposit in destination sites, and therefore its input flux offers an indicator to ground aridity of depositional as well as the source areas. Long-suspension dust from desert regions plays an important role in fine port of the aeolian dust. Compared to the other seasons, dust flux resulted from winter monsoon rises obviously in the northwestern part of the Loess Plateau, whereas other parts possess limited increase of dust input.%黄土高原现代天然降尘的季节性变化研究表明,矿物粉尘是天然粉尘的主要组成成分,有机质和污染物以夏季粉尘中含量最高。粉尘的磁化率在80~150单位之间,明显高于冰期黄土,指示着间冰期时原始粉尘的磁化率就已受到气候条件的影响。粉尘沉积通量的季节性变化在高原北部较大,中部和南部变化较小,年累积通量也是北部明显高于基本相当的其它地区。分析粉尘沉积的气候过程认为,黄土高原的天然降尘

  14. 黄土高原地区窑居度假村开发现状及其意义研究%Development and Significance of Cave Dwelling Resort on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李明; 孙庆珍

    2011-01-01

    Relevant ecotourism theories were applied to further investigate the mushrooming cave dwelling resorts on the Loess Plateau. By introducing the present development of cave dwelling settlements in the study area, types of cave dwelling resort were summarized: historical cave dwelling resort based on high cultural value, artistic value and aesthetic value; cave dwelling resort characterized by primitive folk customs; cave hotel showing folk house features of the Loess Plateau. Luochuan Resort of the Loess Folk Customs, Miaoshang Resort of Sanmenxia, Stone Cave Hotel of Y angjialing in Yan'an were respectively studied to analyze features and development conditions of cave dwelling resort, on the basis of which development principles and countermeasures were discussed. The orientation of cave dwelling resort on the Loess Plateau should be determined first, suotainability and accountability of ecotourism should be followed. Finally, the significance of cave dwelling resort for promoting local economic development, enhancing the rational utilization of natural resources, protecting and developing traditional settlements of cave dwellings was given.%运用生态旅游研究中的相关理论,对目前大量兴起的黄土高原窑居度假村进行了深入调研.从介绍黄土高原窑居聚落的现状入手,总结了窑居度假村的类型,即依托文化价值、艺术价值、审美价值较高的历史窑洞民居形成的旅游度假区;以原汁原味的窑洞民居及风土人情为特色开发的窑洞度假村;体现黄土高原民居特色的窑洞宾馆,并以洛川黄土风情度假村、三门峡庙上村民俗度假村、延安杨家岭石窑宾馆为例,详细分析了窑居度假村的特点和发展现状,在此基础上探讨了窑居度假村的开发原则与对策,强调应明确黄土高原窑居度假村开发的方向,并遵循生态旅游的可持续性原则与责任性原则.最后指出黄土高原窑居度假村的开发在促进当地

  15. Delayed build-up of Arctic ice sheets during 400, 000-year minima in insolation variability confirmed by Chinese loess

    Science.gov (United States)

    Hao, Qingzhen; Wang, Luo; Oldfield, Frank; Peng, Shuzhen; Qin, Li; Song, Yang; Xu, Bing; Qiao, Yansong; Bloemendal, Jan; Guo, Zhengtang

    2014-05-01

    The growth and decay of the Northern Hemisphere ice volume led to alternations of glacial and interglacial climate. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere during the Quaternary period only are scarce because benthic δ18O records represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)—as recorded in the aeolian dust deposits on the Chinese Loess Plateau—can serve as a useful proxy of Arctic climate variability. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections over the past 900 kyr to address the timing of build-up of Northern hemisphere ice sheets around 413 kyr mimina in eccentricity and precessional variability. These periods are regarded as the astronomical analogues of the present interglacial. The grain-size-inferred intensity of the EAWM records shows that the wind strength of EAWM increased rapidly after the end of most interglacials. However, during periods of low eccentricity and precessional variability around 400 kyr and 800 kyr ago, EAWM remains weak for up to 20 kyr after the end of the interglacial episodes MIS 11, MIS 19 and MIS 21. We conclude that the delayed increase in wind strength of the EAWM was caused by delayed buildup of Arctic ice sheets at the ends of the interglacials at 400 kyr intervals, which had led to much longer climate of interglacial mode at high northern latitudes than expected from the marine oxygen isotope records. During these times, the less severe summer insolation minima at 65° N (modulated by 413-kyr eccentricity cycles) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds. Astronomically driven insolation during the present interglacial and in the near future is

  16. 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

  17. 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

    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...

  18. 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.

  19. 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.

  20. 陕北黄土高原植物区系的演变及新生代植物区系分析%Study on the Cenozoic Flora and Flora Evolution of the Loess Plateau of Northern Shaanxi Province

    Institute of Scientific and Technical Information of China (English)

    李登武; 张文辉; 苟小东; 王冬梅

    2011-01-01

    运用植物区系地理学的研究方法,根据古植物学资料及与现代植物区系的对比分析,对陕北黄土高原植物区系的演变及新生代植物区系进行了研究,对深入了解陕北黄土高原植物区系、植被的起源和发展具有重要意义,同时为指导本区目前实施的退耕还林还草、植被恢复等生态环境建设方面可以提供参考.文中论述了自白垩纪以来各时期陕北黄土高原植物区系的演变发展过程,对陕北黄土高原植物区系的演变和现代与新生代孢粉植物群进行了比较分析,认为本区植物区系主要来源于4个方面:一是起源于本地及邻近地区晚白垩纪一早第三纪植物群,一些草本植物和湿生植物主要发生于晚第三纪,耐寒和耐旱的种类主要发生于第四纪;二是来源于地中海区-中亚和欧亚草原;三是来源于东北亚、西伯利亚温-寒地区;四是来源于我国西南、西北、华北及秦岭、华中地区.%Flora study is basic to the understanding of the intrinsic attributes of regional vegetation and its zoning, management, and utilization. Therefore, studies on the flora geography of the Loess Plateau of Northern Shaanxi Province will be important not only for the Loess Plateau Flora zoning, but also for the flora studies of Western China, local planning of its agriculture, forestry and animal husbandry industries. It will also have reference value for the utility and protection of local plant resources. In short, the study of the flora geography will have ecological, economic and social importance in the ecological improvement and natural resources protection. Comparative analysis of material between paleobotany and present-day flora of the Loess Plateau of Northern Shaanxi Province (LPNS) shows the evolution and sources of the LPNS’s flora. The evolutions of flora over stages since the Cretaceous period are discussed. From the flora evolution and the spore and pollen comparison

  1. 黄土高原南部地区农业用地驱动力分析与动态模拟%Driving forces and dynamic simulation of agricultural land in the southern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李强; 任志远

    2012-01-01

    Accessing to the regional agricultural land-use change and its driving factors data from TM and ETM + image in the southern Loess Plateau and using of Binary logistic regression model,we quantitatively analyzed the dynamic evolution characteristics and spatial distribution pattern of agricultural land.And simulated the different types of agricultural land-use change using ArcGIS.The results showed that: 1)The distribution of arable land in the southern Loess Plateau is mainly affected by the distance from the town center,elevation,slope,aspect,population density,GDP unit area.The greatest effect is slope,and the second effects are elevation and population.2)The distribution of woodland is mainly affected by slope and aspect.the biggest factor is slope and the bigger factor is aspect.3)The distribution of the grass is mainly affected by slope and population density.The influencing factors for agricultural land-use are natural and human factors,including the terrain of slope and population density in the southern Loess Plateau.It shows that the most important influencing factors is human activity.Human activity is the important factor for study the agricultural land resources and the rate of change in land ecosystems.%利用黄土高原南部地区TM和ETM+遥感影像,在获取区域农业土地利用变化及其驱动因子数据的基础上,采用Binary Logistic回归模型,定量分析区域内农业用地的动态演化特征与空间分布格局,并运用ArcGIS软件进行不同类型农业用地变化模拟与输出。结果表明:1)黄土高原南部地区耕地的分布主要受距县城中心的距离、高程、坡度、坡向、人口密度、地均GDP的影响,其中受坡度影响最大,发生比expβ是0.83130204,高于其他因子;其次是高程和人口密度,发生比expβ分别为0.99932988和1.00011472。2)林地的分布主要受坡度和坡向的影响,坡度影响最大,坡向次之,发生比expβ分别为1.09136459和0.99209087。3

  2. 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

  3. 黄土高原土壤中细菌群落结构多样性的PCR-DGGE分析%Diversity of Bacterial Community Structure in Soils of Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    潘雪莲; 黄晟; 方昊; 徐军; 郭晓峰; 陈旸; 崔益斌

    2009-01-01

    Soil samples were collected from five regions and 26 soil samples from the Xifeng Profile of the Loess Plateau.Total DNA was extracted from those samples with the aid of bacterial universal primer and amplified by means of PCR and its product analyzed with the DGGE technique to explore diversity of bacterial communities.Oriented towards the features of the microbes in the soil of the plateau,conditions of the DGGE experiment were optimized with an optimal denaturant gradient ranging between 40% and 70%,and an optimal electrophoresis duration being 17 hours (100 V).Analysis of DGGE profiles of bacteria in soils at various depths revealed that there are two different types of bacterial community structures in soils at various depths in the Loess Plateau,which is presumably attributed to changes of the warm-humid environment caused by monsoon climatic conditions,and ice age.In the age when monsoon got stronger in summers and became weak in winters,the climate was warm and humid,and weathering and soil formation were intensive,which showed multiple and dense bands in the DGGE profile,whereas conversely,weathering and soil formation are weak,which showed sparse bands in the profile.The determination of Shannon-Weiner indexes of soil bacteria in the five regions of the plateau indicated that the Shannon-Weiner indexes were influenced not only by the amount of bands,but also by brightness and moving rates of the bands%利用细菌通用引物,对从黄土高原5个地区土壤样品以及西峰剖面26个土壤样品中提取的总DNA进行聚合酶链式反应(PCR)扩增,采用变性梯度凝胶电泳(DGGE)技术对PCR产物进行分析,以揭示黄土高原土壤中细菌群落结构的多样性.针对黄土高原土壤微生物特点进行DGGE试验条件优化,获得最佳变性梯度为40%~70%,最佳电泳时间为17 h(100 V).对不同深度土壤细菌DGGE图谱的聚类分析表明,不同深度土壤细菌呈现2种不同的群落结构,推测其成因可能与

  4. 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.

  5. 黄土高原生态系统过渡带土地覆盖的时空变化分析%Spatial-temporal Change of Land-Cover in Ecosystem Transitional Zones on the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    范泽孟; 李婧; 岳天祥

    2013-01-01

    The ecosystem transitional zones (ETZs) , expected to be among the most sensitive areas to climate changes and human activities, have higher landscape level species richness than in the adjacent ecosystems. The ecological position of land-cover in the transitional zones is prior to the adjacent ecosystems. Therefore, how to quantitatively identify and classify different ETZs and highly explicit their land-cover changes is important for improving the adaptation strategies to mitigate or even benefit from the projected impact of climate change on land use. In this paper, the Holdridge life zone (HLZ) model is improved to classify the ETZ type on the Loess Plateau of China. A positive and negative transformation index of land-cover (PNTIL) is developed to quantitatively evaluate the land-cover changes in every ETZ type. The results show that there are 14 ETZ types, accounting for 25. 21% of the total land-cover area on the Loess Plateau. During the two decades from 1985 to 1995 and 1995 to 2005, cultivated land decreases 0. 93% per decade, and wetland and water area, woodland and grassland increase 3. 47% , 0. 24% and 0. 06% per decade, respectively, on an average. The total land-cover transformation rate of the whole ETZs decreases from 28. 53% to 21. 91%. The total, positive and negative transformed areas of land cover in ETZs have a decreasing trend during the two decades, in general. In both the transitional zones and adjacent biomes on the Loess Plateau, the area of cultivated land showed a decreasing trend, while the area of woodland showed an increasing trend during the two decades. Moreover, the transformation of land-cover types in the transitional zones is generally faster than the adjacent ecosystems. Our results provide a solid preliminary assessment of land-cover changes, indicating that the transitional zones are more affected by climate change and human activities on the Loess Plateau. The ecological diversity and patch connectivity of land-cover in all

  6. 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

  7. The Matuyama-Brunhes geomagnetic reversal in the Stari Slankamen loess section (Vojvodina, Serbia): Its detailed record and its stratigraphic position

    Science.gov (United States)

    Hambach, U.; Jovanović, M.; Marković, S. B.; Nowaczyk, N.; Rolf, C.

    2009-04-01

    The Matuyama-Brunhes geomagnetic reversal is the most important time marker in Quaternary sedimentary sequences. It provides unambiguous correlation between marine, lacustrine, loess and even fluvial deposits because its recognition does ideally not depend directly on the sediment properties but only on their recording capability. The recognition of the Matuyama-Brunhes boundary (MBB) in the Chinese Loess Plateau (CLP) by Friedrich Heller and Tung-Sheng Liu (HELLER & LIU 1982) started the success story of magnetic polarity dating in continental Quaternary sequences. They assigned the Chinese loess to the Quaternary time table and correlated it with the global ice volume record using the magnetic susceptibility signal as palaeoclimate proxy (HELLER & LIU 1984). At the western edge of the Eurasian loess belt, in the southern Carpathian basin in the region called Vojvodina we find several decametres thick loess deposits dating back to the Middle Pleistocene at least (Marković et al., 2008). Like in the CLP in the Vojvodina one can find true loess plateaus reaching thicknesses of more than 50 m. The exposure at Stari Slankamen is located in the north-eastern part of Srem Loess Plateau, on the right bank of the Danube River. The loess sequence is comprised of multiple couplets of loess and palaeosol units totaling approximately 40 m thickness of sediments. 8 palaeosol units can be distinguished separated by several metres thick loess layers. The lower 5 palaeosol units are developed as strongly rubified forest soils with decreasing degree of pedogenesis from old to young. In contrary, the younger palaeosol units including the recent soil are developed as steppe soils. This strongly suggests that a considerably longer palaeoclimatic record is preserved at the site than is found elsewhere in Europe. Magnetic susceptibility (MS) of the whole section was measured in the field as well as in the laboratory at 10 cm intervals in the palaeosol units and at 15 cm intervals in

  8. A Comparison of the Geochemical Features of Some Loess Sections in New Zealand and China

    Institute of Scientific and Technical Information of China (English)

    文启忠; DENNISN.EDEN; 等

    1992-01-01

    A comparison of the geochemical features of loesses of New Zealand and China indicates that the distributions of the elements and their variations reflect the fluctuations of climate which can be compared with the oxygen isotope stages and glacial periods.New Zialand loess is different in source from Chinese loess.Therefore ,some differences are also noticed in their chemical compositions .Loess accumulation in New Zealand is later than that in China.Because of more rainfall in New Zealand and different distributions of loess the elements in loess have suffered stronger leaching than in China.

  9. 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

  10. 参考作物蒸散简易估算方法在黄土高原的适用性%Applicability of simple estimating method for reference crop evapotranspiration in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李志

    2012-01-01

    Some methods for estimating reference crop evapotranspiration (ETo) are widely used in regions with insufficient meteorological data, but their applicabilities should be evaluated. The performances of six simple methods for estimating ET0 (i.e. FAO-24 Rad, FAO-24 BC, Hargreaves, Priestley-Taylor, Makkink and Turc) are evaluated based on the meteorological data from 48 stations during 1961 -2009 in the Loess Plateau. Results showed that FAO-24 BC and Hargreaves equations were satisfactory to estimate annual ETo while Makkink and Priestley-Taylor methods are not. The estimation errors of annual ETo mainly come from those in November to March, while in April to October were very small. Spatial variability exist in the applicability of the six methods. FAO-24 BC and Hargreaves performs better at most stations while the other methods, especially for Makkink and Priestley-Taylor, provide unsatisfactory results. Most methods are not suitable for estimating ETo in the southwest region except for Priestley-Taylor. Overall, FAO-24 BC and Hargreaves are recommended as the priority simple methods for calculating ETo in the Loess Plateau.%参考作物蒸散(ET0)的简易估算方法在气象数据缺乏区域具有广泛的应用,但其适用性需要评估.基于1961~2009年48个气象站的数据,以FAO Penman-Monteith公式为标准评估了6种ET0简易估算方法(FAO-24 Rad、FAO-24 BC、Hargreaves、Priestley-Taylor、Makkink和Turc)在黄土高原应用的可能性.结果表明,对于ET0年值的估算,FAO-24 BC和Hargreaves的结果令人满意,效果最差的是Makkink和Priestley-Taylor公式.ET0年值误差主要来源于11-3月,各方法对4-10月ET0的估算效果相对较好.各方法的适用性存在空间变异,FAO-24 BC和Hargreaves公式的效果普遍较好,其他方法对该区各站ET0估算误差均较大,特别是Makkink和Priestley-Taylor公式;除Priestley-Taylor公式外,多数方法对西南区的估算误差较大.因此,黄土

  11. 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、

  12. 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。

  13. 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

  14. 不同分辨率DEM提取地面坡度的不确定性模拟:以在黄土高原的试验为例%Simulation on slope uncertainty derived from DEMs at different resolution levels:a case study in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    汤国安; 赵牡丹; 李天文

    2003-01-01

    Slope is one of the crucial terrain variables in spatial analysis and land use planning,especially in the Loess Plateau area of China which is suffering from serious soil erosion. DEM based slope extracting method has been widely accepted and applied in practice. However slope accuracy derived from this method usually does not match with its popularity. A quantitative simulation to slope data uncertainty is important not only theoretically but also necessarily to applications. This paper focuses on how resolution and terrain complexity impact on the accuracy of mean slope extracted from DEMs of different resolutions in the Loess Plateau of China. Six typical geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1:10,000 scale topographic maps. Field survey results show that 5 m should be the most suitable grid size for representing slope in the Loess Plateau area. Comparative and math-simulation methodology was employed for data processing and analysis. A linear correlativity between mean slope and DEM resolution was found at all test areas,but their regression coefficients related closely with the terrain complexity of the test areas. If taking stream channel density to represent terrain complexity, mean slope error could be regressed against DEM resolution (X) and stream channel density (S) at 8 resolution levels and expressed as (0.0015S2+0.031S-0.0325)X-0.0045S2-0.155S+0.1625, with a R2 value of over 0.98. Practical tests also show an effective result of this model in applications. The new development methodology applied in this study should be helpful to similar researches in spatial data uncertainty investigation.

  15. Study on the Experience of Management of Rain and Flood of Ancient City in the valley of Loess Plateau%适水土而生--黄土沟壑地区古城雨洪治理经验内涵解读

    Institute of Scientific and Technical Information of China (English)

    宋功明; 韩晓莉

    2014-01-01

    黄土高原以其雨量不均、水土流失、地质灾害多发等特点,塑造了其独特的自然和人文景观,本文以黄土沟壑区古城防洪系统为研究对象,探讨黄土沟壑区古城与当地水土的适应性机制,总结了黄土沟壑区古城雨洪治理系统的规律与特点,指出适水土而生深刻地反映了黄土沟壑地貌下真实的人地关系,对确保古城可持续发展以及今天的城市水系治理、防洪防灾规划及土地利用规划具有重要意义。%Loess plateau with its uneven rainfal , soil erosion, frequent hazards, etc., have the unique natural and cultural landscape, this paper taking the flood control system of ancient city in val ey of loess plateau as the research object, explore adaptive mechanism of soil and water conservation, sum up storm water management laws and characteristics of the ancient city in val ey of loess plateau, point out that ancient cite of this area must be based on the hydrologic and soil condition to ensure that the ancient city of sustainable development. this research have great value to today's urban drainage management, flood control and disaster prevention planning and land use planning.

  16. 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.

  17. Composition and structures of insect community of the alfalfa pasture in the Longdong Loess Plateau%陇东黄土高原苜蓿田昆虫群落的组成与结构分析

    Institute of Scientific and Technical Information of China (English)

    王佛生; 邓芸; 霍转芳

    2011-01-01

    A field survey was conducted to determine the composition and structures of insect community of alfalfa pasture in the Longdong loess plateau of.This study showed that the total number of insects was 21021,and they were subordinated to 12 orders,69 families and 115 species,in which the species were the most from Coleoptera,Lepidoptera and Hymenoptera families,and the individual number of Homoptera,Coleoptera,Hemiptera and Diptera were the biggest.The dominant species were Acyrthosiphon pisum,Sitona lineatus and Adelphocoris lineolatus.The pest,the natural redator,the neutral insects and beneficial insects accounted for 67.54%,19.79%,11.20% and 1.47%,respectively.%在陇东黄土高原苜蓿(Medicago sativa)田调查昆虫群落组成与结构,共采集昆虫21 021头,隶属12目69科115种。研究结果表明,鞘翅目、鳞翅目、膜翅目昆虫科、种数较多;同翅目、鞘翅目、半翅目和双翅目昆虫个体数量较多;优势种群是豌豆无网长管蚜(Acyrthosiphon pisum)、苜蓿盲蝽(Adel phocoris)、条纹根瘤象(Sitonalineatus)。害虫、天敌、中性昆虫和益虫所占比例依次是67.54%、19.79%、11.20%和1.47%。

  18. Luminescence dating of Chinese loess and its applications:past, present and future%中国黄土释光测年与应用:过去、现在与未来

    Institute of Scientific and Technical Information of China (English)

    康树刚; 王旭龙; 王松娜

    2016-01-01

    中国黄土释光测年走过了近40年的历程,这对于推动释光测年技术的进步和黄土古气候古环境研究的深入有重要意义。本文针对中国黄土(以黄土高原为主),简要回顾了以多片法混合矿物热释光(TL)和红外释光(IRSL)测年技术为主的早期(20世纪70年代末期至21世纪第一个十年初期)探索阶段的发展,重点阐述了以成熟的单片再生剂量(SAR)法石英光释光(OSL)技术和延长测年年限的多种方法并存为特征的目前(21世纪以来)研究进展。同时,系统论述了释光测年技术在晚更新世以来中国黄土古气候古环境研究中的意义,如在年代标尺建立、粉尘堆积速率变化重建、地层对比与划分、轨道和亚轨道尺度气候演变与气候事件揭示等方面的应用。另外,也对将来中国黄土释光测年技术的发展方向和其在古气候古环境研究领域的应用前景进行了简单展望。%Background, aim, and scope It has been approximately forty years since the early luminescence dating of Chinese loess. Numerous efforts have been contributed to the luminescence dating technique development and its paleoclimate applications into Chinese loess. Thus, at this stage, it is important to present a systematic summary of the development of luminescence dating technique and its application into Chinese loess.Materials and methodsThis paper provides an overview and perspective of luminescence dating of Chinese loess and its applications in palaeoclimate area in the past approximately forty years.Results The luminescence dating development during early stage (1970s—2000s), which dominates by multiple-aliquot thermoluminescence (TL) and infrared stimulated luminescence (IRSL) dating of polymineral grains, will be briefly summarized. This paper will focus on the present (since 2000s) single-aliquot regenerative-dose (SAR) quartz optically stimulated luminescence (OSL

  19. Reliability analysis of gravitational erosion stability of small watershed in the Loess Plateau%黄土高原小流域重力侵蚀稳定可靠度分析

    Institute of Scientific and Technical Information of China (English)

    鲁克新; 李占斌; 于国强

    2012-01-01

    在应用有限差分FLAC3D软件对黄土高原小流域概化模型塑性屈服区分布规律进行数值模拟的基础上,采用基于FLAC3D的有限元强度折减法和简化一次二阶矩法相结合的方法研究了小流域概化模型重力侵蚀稳定可靠度和破坏概率.结果表明:小流域剪切塑性区域主要分布于坡面和沟坡大部分区域,张拉塑性区域主要分布于梁峁顶和梁峁坡上部;小流域边坡整体破坏概率达到28.6%,高于1%,表明流域重力侵蚀处于高破坏概率范畴之内,处于不可接受的风险水平,需采取适当的工程措施以提高其稳定性;采用安全系数法和可靠度相结合的二元指标评价体系分析和评价边坡稳定性,能获得更为合理、可靠的分析结果.相关数值模拟和稳定可靠度分析结果可应用于流域重力侵蚀研究中,为推动流域侵蚀产沙时空规律研究的深入发展和小流域水土流失综合治理提供科学依据.%Gravity erosion is an important agent for soilerosion and accounts for heavy portion of the total soil-erosion amount in the Loess Plateau, and is one of main sources of the formation and maintenance of hyper-concentrated flow in the middle reaches of the Yellow River, thus the study on gravity erosion has great theoretical and application values. The finite difference software, I. E. FLAC3D, is used to simulate the distribution law of plastic yield zone of a small watershed model in the paper, and the systematic method of combining strength reduction method based on FLAC3D with simplified first-order second-moment method is applied to study the stability reliability and failure probability of the small watershed model. The results in the paper are as follows: firstly, the volume of shear plastic yield zone in the watershed model accounts for about 99. 5 percent of that of total plastic yield zone in the watershed, while that of tension plastic yield zone accounts for only 0. 5 percent

  20. 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

  1. 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

  2. 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.

  3. Book Review: Late Cenozoic Climate Change in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution

    Science.gov (United States)

    Clemens, Steven C.

    2015-01-01

    Loess-Paleosol deposits drape >500,000 km2 of eastern China, spanning environments from the humid, monsoon-influenced regions near the coast to the arid, westerlies-dominated regions inland. Sections, up to hundreds of meters thick, are exposed in deeply incised river valleys and can be accessed as well by drilling. Combined, the high sedimentation rates and extensive geographic coverage make these sections unique among global terrestrial sediment archives. The Chinese loess-paleosol sequences, and the arid interior regions to the northwest, record diverse aspects of geologic and environmental change ranging from the tectonic evolution of the Tibetan Plateau (106 year time scale) through glacial-interglacial scale changes in global ice volume and greenhouse gasses (105 year time scale) on down through the orbital (104 years) to millennial and centennial scale events (103-102 year) relevant to the underpinnings of human interactions with changing environmental pressures. 'Late Cenozoic Climate Chang in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution' is a timely contribution that synthesizes findings derived from the extensive work in these areas, places the findings in the broader context of global climate change and helps to define avenues for future research.

  4. 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,...

  5. EAST ASIAN MONSOON CHANGES DURING THE HOLOCENE——RECORDS FROM THE SOUTHEASTERN LOESS PLATEAU%黄土高原东南部黄土记录的全新世东亚季风变化

    Institute of Scientific and Technical Information of China (English)

    许晨曦; 郝青振; 杨石岭; 赵淑君; 周鑫; 葛俊逸; 肖国桥

    2011-01-01

    The influence of global warming on East Asian Monsoon ( EAM) has received intensive concern, and studies on history of EAM could provide important climate analogue in the warmer temperature context. Five loess-paleosol sequences in the southeastern Loess Plateau were sampled to address the history of EAM during the last 20 ka. The intensity of EAM was weak from 18 to 12 ka B. P. , increased rapidly in the interval of 12-10 ka B. P, and reached highest points during 10-6 ka B. P. , and declined after 6 ka B. P. The proxies of summer monsoon, magnetic susceptibility and paleo-weathering intensity in this study is basically timely consistent with the geological records in different part of EAM region. The insolation of low-latitude northern hemisphere is main control factor of EAM, although changes of EAM lagged variations of insolation of low-latitude northern hemisphere. The lag may be induced by several important boundary conditions ( e. G. , scales of polar ice sheet in northern high latitudes, sea level changes, interaction between sea and atmosphere in low latitudes) of EAM to insolation and interaction between components of climate system. Additionally, our studies showed that magnetic susceptibility ( MS) and maximum FeD/FeT values in same section were not in same position of soil profiles, with lower position of maximum FeD/FeT value than that of MS in relatively strong weathering area. Compared with MS, FeD/FeT ratio can better reflect the intensity of EAM.%在全球变暖背景下,未来东亚季风的变化一直备受关注,而东亚季风演化规律的研究能够为未来的预测提供重要基础.黄土-古土壤序列几乎连续地记录了古东亚季风变化的信息,本文选取黄土高原东南部的荥阳、偃师、灵宝、吉县、丁村五个剖面进行磁化率和古风化强度分析,重建了黄土高原东南部两万年以来的东亚夏季风演化历史:18~12 ka B.P.,季风强度较弱;12 ~10 ka B.P

  6. 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.

  7. 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.

  8. 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.

  9. Comparative Studv on the Application of Several Drought Assessment Indices in the Loess Plateau%几种干旱评估指标在黄土高原的应用对比分析

    Institute of Scientific and Technical Information of China (English)

    尹盟毅; 赵西社; 刘新生; 李兴涛; 赵晓峰; 刘进

    2012-01-01

    With the agricultural drought indices for reference, the drought weather processes appeared in 43 counties and districts of Shaanxi loess plateau from March to June, 2007 were analyzed and compared by four methods. The results showed that the calculation results of the four methods showed more severe drought than that of the statistics departments; the drought level calculated by relative moisture index was higher than the actual level shown in statistics; the drought-affected area obtained by the standardized precipitation index was larger; the anomaly percentage of precipitation and comprehensive drought index were basically consistent with the actual situation. In the calculation of the start and end dates of drought, the calculation results of relative moisture index was the same as the calculation results of water conservancy industry standards set by the Ministry of Water Resources; in the calculation of drought end date, the calculated results using the integrated meteorological drought index and the precipitation anomaly percentage index were very close to that of water conservancy industry standard set by The Ministry of Water Resources.%利用4种气象干旱指数计算方法,以农业气象干旱指标为参照,对2007年3月~6月陕西黄土高原43县区出现的干旱天气过程进行分析比较.结果表明,4种干旱指数计算结果比统计部门的实际旱情程度严重;相对湿润度指数计算出的干旱等级比实际统计等级严重;标准化降水指数计算结果反映出特旱面积过大;降水量距平百分率和气象干旱综合指数计算结果与实际情况基本一致.在干旱开始与结束日期计算中,相对湿润度指数计算结果与水利部所规定的水利行业标准计算结果一致;在干旱结束日期计算中,采用气象综合干旱指数和降水距平百分率指数计算的结束日期与水利部规定计算结果较为接近.

  10. 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.

  11. 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.

  12. How to protect loess-palaeosol sequences? - Proposal of Loess Geopark in Vojvodina Province (North Serbia)

    Science.gov (United States)

    Vasiljević, Dj. A.; Marković, S. B.; Hose, T. A.; Lukić, T.; Basarin, B.; Vujičić, M. D.

    2012-04-01

    Loess-palaeosol sequences preserve the most important continental record of climatic and environmental changes during the Quaternary. As loess deposits in the Vojvodina region (North Serbia) could be regarded as one of the most important European terrestrial records of climatic and environmental changes during the last million years that makes them valuable scientific resource. Unfortunately, these sites, due to their economic (e.g. agriculture and brickyards) and functional (e.g. remote sections as waste disposals) values, are constantly endangered by numerous causes and could be degraded or exploited permanently. This study will give proposal of establishing loess geopark as protected area that would include the most significant loess sections in the investigated area. The study is based on analytical, theoretical and practical suggestions and rules according to the general Guidelines and Criteria for National Geoparks seeking UNESCO's assistance to join the Global Geoparks Network. Loess and loess like sediments cover more than 60 % of the area and are preserved in six separate loess plateaus: Bačka, Srem, Tamiš, Banat, south-east Banat, and Titel Loess Plateau, which make it a surface large enough to serve local economic and cultural development. As the dissemination of loess in Vojvodina has a dispersed character, the potential Geopark should also have a certain number of separate locations. A fragmented approach should require less effort during the geoconservation practice, with separate processes, but identical aim. Therefore, one the initial steps of protection and recognition of (loess) geosites should be first achieved by national or provincial legislation and/or by management policies before inscription on the World Heritage List of recognition as a Global Geopark because these organisations by themselves do not provide any protection. As unique protected area of this kind in Europe and wider, role model for this loess geopark could be China, the

  13. Micromorphological characters of quartz grain from Nilke loess-paleosol sequences and their implications of origin and provenance%伊犁尼勒克黄土石英颗粒微形态特征及其成因与物源意义

    Institute of Scientific and Technical Information of China (English)

    李越; 宋友桂; 赵井东

    2016-01-01

    Background, aim, and scope Xinjiang is also one of the most signiifcant loess regions in China with the exception of Chinese Loess Plateau, and the loess is mainly present in the northern piedmont of the Tianshan and Kunlun Mountains and Ili Basin. The loess deposits in Ili Basin unconformably cover the river terraces, the low uplands and the slopes of the Tianshan Mountains, and the researches on them have the merit of enabling reconstructions of past climate change in westerly dominant area of inland Asia. Although many predecessors have investigated the spatial distribution and studied the ages, pedostratigraphy, rock magnetism, elemental and mineral compositions and their implications for paleoclimate in details with respect to the Ili loess, there are many urgent questions that need to be solved: How were the materials of Ili loess generated? Which geological process was experienced by the loess silt particles before they reached the sediment area? And where is the provenance of Ili loess? We have had no understanding of the answers by far, which hampers the interpretation of climate change. For this reason, this paper aims to solve the problems above mentioned with the micromorphological characters of quartz grains. In recent study, we compared the micromorphology of quartz grains from Nilka loess with those from glacial tills, riverbed deposits and desert sands to determine the mechanisms of loess-sized quartz silt production. These works will lay the foundation for the subsequent studies on the Ili loess.Materials and methods The 4 loess samples were collected from Nlika section located at the second-order terrace of Kashi River in the east of Ili Basin with the depths 1.50 m, 9.10 m, 11.06 m and 19.56 m, respectively. Glacial till was sampled from the terminus of Arqialeter Glacier located in catchment area of Xiate River; riverbed deposits were sampled from Kashi River and the sampling sites lay in the west of Nilka loess section; desert sands were

  14. Green Revolution on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    THE Workers’ and Peasants’ Red Army, under the leadership of the Communist Party of China(CPC), arrived in northern Shaanxi Province at the end of 1935 following an arduous journey of over 12,500 km. Survivors of the Long March settled in the small bleak and desolate city ofYan’an.

  15. 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.

  16. Leaf functional traits of different forest communities in Ziwuling Mountains of Loess Plateau%黄土高原子午岭不同森林群落叶功能性状

    Institute of Scientific and Technical Information of China (English)

    李宏伟; 王孝安; 郭华; 王世雄; 夏菲

    2012-01-01

    对黄土高原子午岭地区5种主要森林群落中重要值>0.1的物种叶功能性状进行了比较,结果表明:1)叶干物质含量(LDMC)与比叶面积(SLA)呈负相关;SLA与叶厚度(LT)呈负相关,但与叶氮含量(LNC)和叶磷含量(LPC)呈正相关;LT与LNC、LPC和叶钾含量( LKC)呈负相关;LNC、LPC和LKC三者之间均呈正相关.2)坡位是影响叶大小(LS)、LT、LNC和LKC的主要地形因子,海拔对LPC和SLA的影响最大,而坡向则是影响LDMC的主要因子.因此,叶功能性状之间所呈现的特征及其对立地条件的适应都表现出了植物的生态策略.3)各群落间的乔木层叶功能性状均有显著差异,灌木层的叶功能性状无显著差异,而草本层除了LDMC无显著差异(P>0.05)外,其他叶功能性状均有显著差异,说明群落的叶功能性状的大小取决于群落内物种的叶功能性状及其重要值.%A comparative study was made on the leaf functional traits of the plant species whose importance value is >0. 1 in five main forest communities in Ziwuling Mountains of the Loess Plateau. For the test plant species, their leaf dry matter content ( LDMC) had significant nega-tive correlation with specific leaf area ( SLA) , SAL was significantly negatively correlated with leaf thickness ( LT) but positively correlated with leaf nitrogen content ( LNC) and leaf phosphor-us content (LPC) , LT was significantly negatively correlated with LNC, LPC, and leaf potassium content (LKC) , and there were significant positive correlations among LKC, LPC, and LNC. Slope position was the main terrain factor affecting leaf size, LT, and LNC, elevation had greater effects on LPC and SLA, while slope direction was the main factor affecting LDMC. The relation-ships among the leaf functional traits and the adaptation of the leaf functional traits to terrain fac-tors showed the ecological strategy of the plant species. The leaf functional traits of the plant spe-cies in tree layers of

  17. 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

  18. 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

  19. 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)

  20. 西北黄土高原区路域乡土植物资源筛选研究%Selection of Indigenous Plants in Roads in Northwestern Loess Plateau Area

    Institute of Scientific and Technical Information of China (English)

    张铁军; 王春玲

    2012-01-01

    [目的]通过对路用乡土植物区资源利用研究,解决生物工程所需的乡土植物资源不足问题。[方法]以西北黄土高原区为研究范围,以调查研究为主、试验研究为辅开展了乡土植物资源筛选的研究工作,调查了该区域能在恶劣条件下生长的植物种类及其在路域的适应状况,对有望大规模应用的植物组合模式进行了综合观测及评定。[结果]研究确定了该区中央分隔带可栽种乔木有4种,分别为侧柏、桧柏、圆柏、榆树;灌木有9种,分别为枸杞、柽柳、刺枚、连翘、四翅滨藜、榆叶梅、沙棘、紫穗槐、丁香。另皂荚、刺槐、沙枣、火炬、垂柳、旱柳及白腊树形高大饱满、景观效果好,适宜作为行道树种植;灌木分枝多、树形散乱、高度有限不宜单植,与植株比较高大的树种配合栽种可达到较好的景观效果;山桃、榆树易受虫害,宜和其他树种间植,在空间上阻隔传播。【结论】该研究为路域乡土植物资源筛选研究奠定了基础,为解决生物工程所需的乡土植物资源不足问题提供了帮助。%[Objective] The aim was to study on resource utilization of indigenous plants in roads in order to solve resource shortage of indigenous plant in bioengi- neering. [Method] Based on northwestern loess plateau area, we conducted research on selection of indigenous plants and survey on the species which could live in adverse condition, mainly by surveying, with frequent tests as a supplement, to make a comprehensive observation and evaluation on plant combinations which are to be extensively applied. [Result] The research indicated that in central dividing strips, four arbors, including Platycladus orientalis (Linn.)Franco, Sabina chinensis, Sabinachinen- sis(Linn.)Ant., and Ulmus purnila L., and nine frutices, including Lycium chinense, Tamarix austromongolica, Rosa xanthina Lindl., Forsythia suspense

  1. Selection of Indigenous Plants in Roads in Northwestern Loess Plateau Area%西北黄土高原地区路域乡土植物资源筛选研究

    Institute of Scientific and Technical Information of China (English)

    张铁军; 王春玲

    2012-01-01

    [ Object] Hie aim was to study on resource utilization of indigenous plants in roads in order to solve resource shortage of indigenous plant in bioengineering. [ Method ] Based on northwestern loess plateau area, we conducted research on selection of indigenous plants and survey on the species which could live in adverse condition, mainly by surveying, with frequent tests as a supplement, to make a comprehensive observation and evaluation on plant combinations which are to be extensively applied. [ Result] The research indicated that in central dividing strips, four arbors, including Platycladus orientnlis (Linn. ) Franco, Sabina chinensis, Sabinachinensis ( Linn. ) Ant. , and Ulmus pumila L. , and nine frutices, including Lycium chinense, Tamarix austromongolica, Rosa xanthina lindl. , Forsythia suspense, Atriplex canescens, Amygdalus triloba, Hippophae rhamnoides Linn. , Amorpha fruticosa L. , and Syzygium aromaticum could be planted. In addition, Gleditsia sinensis Lam, Robinia pseudoacacia L, Elaeagnus angustifolia L. , Rhus typhina, Salix babylonica, Salixmatsudana and Fraxinus chinensU, tall and strong, are suitable to be planted as border trees, presenting a good vision. Frutices, limited by height, are usually with more branches, which will provide a good landscape if grown with tall plants. Prunus dacidiana and Ulmus pumila L. , prone to be damaged by insects, should be planted with other species to stop the infestation in space. [ Conclusion ] The research laid foundation for selection of indigenous plants in roads, providing references for resource shortage of indigenous plant for bioengineering.%[目的]通过对路用乡土植物区资源利用研究,解决生物工程所需的乡土植物资源不足问题.[方法]以西北黄土高原区为研究范围,以调查研究为主、试验研究为辅开展了乡土植物资源筛选的研究工作,调查了该区域能在恶劣条件下生长的植物种类及其在路域的适应状况,对有望大规

  2. Seasonal variation of aerosol optical properties at AERONET of the semi-arid region in Loess Plateau%黄土高原半干旱区气溶胶光学特性季节变化特征

    Institute of Scientific and Technical Information of China (English)

    白鸿涛; 陈勇航; 王洪强; 张强; 郭铌; 王胜; 潘鹄; 张萍

    2011-01-01

    Semi - arid regions are defined as transition zones between arid and sub - humid belts where precipitation is less than the potential evaporation. Semi -arid lands, especially those located in mid -latitude inner continental regions, are some of the most sensitive areas to climate change. One of these regions is found in western China. During the last few decades, warm winters and dry springs occurred more frequently in northwestern China where, with disturbances brought about by human activity,large areas of vegetation were destroyed, thus giving rise to anthropogenie dust emissions. Understanding how human activity and the resulting dust emissions affect aerosol optical properties in these semi -arid regions is an essential step for developing mitigation and adaptation strategies to climate changes in these transition areas. In order to monitor the global aerosol optical properties, the U. S. space agency NASA and its partners established a worldwide network of ground - based observationswhich is an international aerosol automatic monitoring network called AERONET (Aerosol Robotic Network). The sun and sky diffuse radiation was measured and thene the aerosol optical properties are retrieved by using the sun and sky scanning spectral radiation observations. The products from the AERONET direct sun and sky radiance measurements are retrived through a rigorous calibration,cloud mask processing, and quality control. In this paper, the impact of dust aerosols on the semi - arid climate of northwestern China was analyzed using Version 2 Level 2 dataset from the AERONET site located in the semi - arid region in Loess Plateau in China, which is named as Lanzhou_city site. The seasonal variation of parameters of atmospheric aerosol optical properties such as aerosol optical thickness, Angstrom exponent, volume size distribution (dV(r)/dlnr), refractive index (n-ik) and single scattering albedo ( 0 ) were analyzed. The results show that the optical properties of the dust

  3. 基于GIS的黄土高原生态系统服务价值对土地利用变化的响应及生态补偿%Response of ecosystem service values to land use change based on GIS and ecological compensation in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    王飞; 高建恩; 邵辉; 张通; 张元星; 许秀泉; 赵春红; 王宏杰

    2013-01-01