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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. Magnetic proxy climate results from the Duanjiapo loess section, southernmost extremity of the Chinese loess plateau

    OpenAIRE

    Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zhu, R.; Institute of Geophysics, Chinese Academy of Sciences, Beijing, China; Guo, B.; Institute of Geophysics, Chinese Academy of Sciences, Beijing, China; Yue, L.; Department of Geology, Northwest University, Xi'an, China; Pan, Y.; Institute of Geophysics, Chinese Academy of Sciences, Beijing, China; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia

    1999-01-01

    We report mineral magnetic results from a 7.5 m loess sequence (150 samples) from the southernmost extremity of the Chinese loess plateau (which includes the last two glacial cycles). In this area the loess sediments experienced particularly intense weathering processes. The magnetic assemblage is dominated by a mixture of pseudo-single domain (PSD) and multidomain (MD) magnetite with associated superparamagnetic (SP) grains of either magnetite or maghemite in the paleosols and weat...

  3. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  5. 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.

  6. 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

  7. 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; SONG Yougui

    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.

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

    NARCIS (Netherlands)

    Hessel, R.

    2006-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    GuodongJia

    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.

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

    Science.gov (United States)

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

    2016-06-01

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

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

    Directory of Open Access Journals (Sweden)

    R. Liu

    2010-01-01

    Full Text Available The Chinese Loess Plateau is located in the north of China and has a significant impact on the climate and ecosystem evolvement over the East Asian continent. Estimates of evapotranspiration (ET at a regional scale are in crucial need for climate studies, weather forecasts, hydrological surveys, ecological monitoring and water resource management. In this research, the ET of the Chinese Loess Plateau was estimated by using an energy balance approach and data collected during the LOess Plateau land-atmosphere interaction pilot EXperiments 2005 (LOPEX05. With the combined data of the Medium Resolution Imaging Spectrometer (MERIS, the Advanced Along-Track Scanning Radiometer (AATSR and some other variables such as air temperature, crop height and wind speed, the instantaneous net radiation, sensible heat flux and soil heat flux were calculated; the instantaneous latent heat flux was derived as the residual term of energy balance, and then converted to daily ET value by sunshine duration. The calculated daily ET from the model showed a good match with the measurements of the eddy covariance systems deployed in LOPEX05. The minimum relative error of this approach is 9.0%, the cause of the bias was also explored and discussed.

  13. 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.

  14. Tracing the provenance of fine-grained dust deposited on the central Chinese Loess Plateau

    Science.gov (United States)

    Sun, Youbin; Tada, Ryuji; Chen, Jun; Liu, Qingsong; Toyoda, Shin; Tani, Atsushi; Ji, Junfeng; Isozaki, Yuko

    2008-01-01

    Eolian dust deposits in north China provide an excellent means of determining past variations in continental paleoclimate and atmospheric circulation. However, debate still exists on which deserts in east Asia are the dominant sources of Chinese loess and whether the dust provenance has shifted significantly at different time scales. Here we present new constraints on the provenance of fine-grained dust deposited on the central Chinese Loess Plateau (CLP) by combining electron spin resonance signal intensity and crystallinity index of fine-grained quartz contained in samples from two loess-paleosol sequences. Our results show that the fine-grained dust deposits on the CLP originate mainly from the Gobi desert in southern Mongolia and the sandy deserts in northern China (primarily the Badain Juran and Tengger deserts), rather than from the Taklimakan desert in western China, at least during the last climatic cycle. The dominant source of fine-grained dust varied significantly, from southern Mongolia during cold periods, to northern China during warm periods. The glacial-interglacial provenance fluctuations are strongly coupled with changes in the intensity of the near-surface northwesterly winter monsoon.

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

    Institute of Scientific and Technical Information of China (English)

    LI Fengjiang; WU Naiqin; Denis-Didier Rousseau

    2006-01-01

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

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

    Science.gov (United States)

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

    2004-12-01

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

  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. 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...... Chinese Loess Plateau site. We reconstruct MARs and construct an age model for monsoon proxies at the site. The luminescence ages show significant pedogenic and anthropogenic disturbance in material deposited after ca. 20–22 ka. Analysis of other published data suggests that this disturbance may be more...

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

    Directory of Open Access Journals (Sweden)

    Gang Liu

    2011-08-01

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

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

    Science.gov (United States)

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

    2013-04-01

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

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

    OpenAIRE

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2013-12-01

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

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

    Science.gov (United States)

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

    2014-11-01

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

  5. Proxy of monsoon seasonality in carbon isotopes from paleosols of the southern Chinese Loess Plateau

    Science.gov (United States)

    Wang, Hongfang; Follmer, L.R.

    1998-01-01

    Soil organic matter (SOM) and soil carbonate (SC) are common constituents in soils and are directly related to plant growth. SOM accumulates gradually from the decomposition of plant material over time, whereas SC formation is biased to dry-season soil-dissolved CO2 that derives from plant respiration during a drying phase of the growing season. In some mixed C3-C4 environments, the peak of C3 and C4 plant metabolism differs seasonally, and the carbon source that contributes to the SOM and SC can be different. Consequently, ??13C(SOM) values reflect an annual average of the floral biomass, but ??13C(SC) values reflect a seasonal aspect of the plant community. The relationship between ??13C(SC) and ??13C(SOM) is mainly controlled by how different the seasonal conditions are. Our results suggest that the relationship is a seasonal proxy that can be used to differentiate the seasonality effects of Indian, East Asian, and Siberian monsoons on the Chinese Loess Plateau during the last interglacial-glacial cycle.

  6. 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

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

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

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

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

    Science.gov (United States)

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

    2006-10-01

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

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

    Science.gov (United States)

    Nie, Junsheng; Song, Yougui; King, John

    2016-03-01

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

  10. 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

  11. Magnetic stratigraphy constraints on the Matuyama-Brunhes boundary recorded in a loess section at the southern margin of Chinese Loess Plateau

    Science.gov (United States)

    Wu, Yi; Zhu, Zhaoyu; Qiu, Shifan; Han, Yulin; Cai, Jianxin; Rao, Zhiguo

    2016-02-01

    Although the Matuyama-Brunhes boundary (MBB) in the Chinese Loess Plateau (CLP) is very important in reliably correlating Quaternary loess with other sediments in the world, particularly with marine and polar ice cores, its exact stratigraphic position remains controversial. Previous investigations usually placed the MBB between paleosol unit S8 and loess unit L8 in various locations. To better understand the spatial differences in the MBB position, a high-resolution paleomagnetic study was conducted in a loess section of the Lantian Basin at the southern margin of the CLP. The results show that the MBB is situated in the middle of the relatively weak paleosol unit S7, consistent with a recent report on the MBB based on a 10Be study from the Xifeng and Luochuan loess sections of the central CLP. However, the regional anomalously low magnetic susceptibility in paleosols S7 and S8 indicates that it is more reliable to determine the paleoclimate boundaries between loess and paleosol horizons of this segment with median grain size. Then, the MBB in the Yushan section can be correlated with the bottom of paleosol S7, corresponding to the older part of interglacial marine isotope stage 19. This result temporally reconciles the striking discrepancy of the position of the MBB recorded in between loess and other typical sedimentary sequences, and further confirms that the stratigraphic position of the MBB could spatially vary to a certain extent due to regional sedimentary or paleoclimatic conditions in the marginal areas of the CLP. In the Yushan section, the high-frequency variations of paleomagnetic directions during a long period of ˜31 ka before the MBB, however, could not be attributed to a genuine response to the true geomagnetic behaviour. Moreover, the climate offset defined by the magnetic susceptibility and median grain size of the section can be preliminarily attributed to the regional geology and paleoenvironment background. A multiproxy-based stratigraphic

  12. 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.

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

    Science.gov (United States)

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

    2016-04-01

    Understanding how the vulnerability of agricultural production to climate change can differ spatially has practical significance to sustainable management of agricultural systems worldwide. Accordingly, this study developed a conceptual framework to assess the agricultural vulnerability of 243 rural counties on the Chinese Loess Plateau. Indicators representing the climate/agriculture interface were selected to describe exposure and sensitivity, while stocks of certain capitals were used to describe adaptive capacity. A vulnerability index for each county was calculated and the spatial distribution was mapped. Results showed that exposure, sensitivity, and adaptive capacity occur independently, with most contributing indicator values concentrated in a narrow range after normalization. Within the 49 most vulnerable counties, which together encompass 81 % of the vulnerability index range, 42 were characterized by high exposure and sensitivity but low adaptive capacity. The most vulnerable area was found to be located in the central northeast-southwest belt of Loess Plateau. Adaptation measures for both ecological restoration and economic development are needed and potential adaptation options need further investigation. PMID:26563383

  14. 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.

  15. Assessment of bank gully development and vegetation coverage on the Chinese Loess Plateau

    Science.gov (United States)

    Li, Zhen; Zhang, Yan; Zhu, Qingke; He, Yuanmei; Yao, Wenjun

    2015-01-01

    Gully erosion is a serious environmental problem and the primary source of sediment loss on the Loess Plateau of China, yet previous research focusing on bank gullies is limited. An assessment of bank gully development is needed as a basis for predicting erosion rates under the effects of vegetation cover and land use change. To estimate bank gully retreat rates under different land uses, assess the factors leading to bank gully development and model gully area growth rate at the catchment scale, 30 catchments with an average area of 39.0 ha were selected in the southeastern part of the Loess Plateau. QuickBird images (0.61 m resolution) obtained in 2003 and 2010 were interpreted to delineate bank gully features, and a 5 m resolution digital elevation model was used to extract topographic factors. The results showed that from 2003 to 2010, the maximum retreat rates of bank gully heads in the 30 investigated catchments ranged between 0.23 and 1.08 m yr- 1, with an average of 0.51 m yr- 1. The ratio of bank gully growth area to valley area changed from 0.49 to 9.45%, depending on land use, with average increases of 3.94, 4.00 and 2.09% for the three land use types identified, i.e. mixed use, grassland and forestland, respectively. Correlation analysis indicated that the effects of topographic factors on bank gullies decreased as vegetation coverage increased in upslope drainage areas and that vegetation coverage exceeding 60% in upslope drainage areas can significantly control bank gully development. A model was built to predict the bank gully area growth rate (Ra, m2 yr- 1) with upslope drainage area (Ai, m2), local slope gradient (S, m m- 1) and the proportion of the area with vegetation coverage below 60% in upslope drainage areas (Φ0.6) at the catchment scale. The regression equation is in the form Ra = 0.1540[(Φ0.6Ai)0.24S]3.2588. Compared with previous studies, vegetation is a factor in this model, which would be helpful for assessing the influence of

  16. 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.

  17. Miocene climate change on the Chinese Loess Plateau: Possible links to the growth of the northern Tibetan Plateau and global cooling

    Science.gov (United States)

    Sun, Youbin; Ma, Long; Bloemendal, Jan; Clemens, Steven; Qiang, Xiaoke; An, Zhisheng

    2015-07-01

    The evolution of the Asian monsoon-arid environmental system during the Cenozoic was closely related to the growth of the Himalayan-Tibetan Plateau and global climate change. However, due to inconsistencies in paleoclimatic reconstructions and to various constraints on the timing of the growth of the Tibetan Plateau, the relative impacts of regional uplift and global cooling on Asian climate change remain controversial. Here we investigate the mineralogical composition of a Miocene Red Clay deposit on the western Chinese Loess Plateau in order to infer changes in chemical weathering and monsoon intensity. Variations of four mineralogical ratios (chlorite/quartz, illite/quartz, calcite/quartz, and protodolomite/quartz) reveal that the summer monsoon intensity was relatively strong during the early Miocene (23.5-18.5 Ma), weakened gradually until ˜9.5 Ma, and strengthened again in the late Miocene. We synthesized previously published thermochronological data from the northeastern Tibetan Plateau and surrounding mountains, and the results suggest that two phases of the rapid growth of northern Tibet occurred around 24-17 and 13-7 Ma. Comparison of paleoclimatic proxies and thermochronological data suggests that the gradual weakening of the summer monsoon intensity from 18.5 to 9.5 Ma paralleled global cooling, whereas two intervals of strengthened monsoon in the early and late Miocene were possibly related to the rapid growth of northern Tibet. Our combination of paleoenvironmental proxies and thermochronological data reveals possible links between Miocene Asian monsoon evolution, phased growth of the Tibetan Plateau, and global climate change, and confirms the interconnection of geodynamic and atmospheric processes in the geological past.

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

    Science.gov (United States)

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

    2016-06-01

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

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

    Science.gov (United States)

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

    2010-09-01

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

  20. Germinable Soil Seed Banks and the Restoration Potential of Abandoned Cropland on the Chinese Hilly-Gullied Loess Plateau

    Science.gov (United States)

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

    2010-09-01

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

  1. Provenance changes of eolian dust at Lingtai section in the Chinese Loess Plateau since 7 Ma and its implication for desert development in East Asia

    Science.gov (United States)

    Isozaki, Y.; Tada, R.; Sun, Y.; Nagashima, K.; Zheng, H.; Toyoda, S.; Tani, A.

    2008-03-01

    It is suggested that the uplift of Himalaya-Tibetan Plateau enhanced interior aridity in East Asia and resulted in development of middle latitude gobi and sandy deserts and accumulation of the eolian sediments in the Chinese Loess Plateau. Therefore, estimation of the provenance for eolian sediments in the Chinese Loess Plateau is critical to reconstruct the environmental changes in East Asia and their relation to the Himalaya-Tibetan Plateau uplift. We recently developed a new provenance tracing method by using a combination of Electron Spin Resonance (ESR) signal intensity and Crystallinity Index (CI) of quartz, and demonstrated that fine fraction of the surface sediments from nine major deserts in East Asia could be distinguished one another on the ESR signal intensity versus CI diagram. Here, we measured ESR signal intensity and CI of quartz in fine fractions of samples covering the last 7 Ma obtained from Lingtai section in the central Chinese Loess Plateau, and compared the results with those of the surface samples from nine major deserts in East Asia. The results suggest that the provenance of fine fraction of the eolian sediment in Lingtai section changed at 4.3, 2.1, 1.4, 1.1, 0.8 and 0.4 Ma. During 7 to 4.3 Ma, the dust might be have been supplied from Precambrian to Paleozoic metamorphic and granitic rocks and granite exposed in the present central to eastern part of the Tian Shan Mountains. The contribution from the Taklimakan desert appeared at 4.3 Ma, increased drastically at 1.1 Ma, and persisted till 0.8 Ma, whereas the main source of detrital material to the Taklimakan desert might have changed from eastern part of the Kunlun and the Altyn Mountains to western part of the Kunlun and the Tian Shan Mountains. During 0.8 to 0.4 Ma, contribution from the Badain Juran desert gradually increased. Finally, contribution from the Tengger desert appeared from 0.4 to 0 Ma. Together with tectonic evidences from literatures, the provenance changes from 4.3 to 0

  2. Provenance changes of eolian dust at Lingtai section in the Chinese Loess Plateau since 7 Ma and its implication for desert development in East Asia

    Directory of Open Access Journals (Sweden)

    Y. Isozaki

    2008-03-01

    Full Text Available It is suggested that the uplift of Himalaya-Tibetan Plateau enhanced interior aridity in East Asia and resulted in development of middle latitude gobi and sandy deserts and accumulation of the eolian sediments in the Chinese Loess Plateau. Therefore, estimation of the provenance for eolian sediments in the Chinese Loess Plateau is critical to reconstruct the environmental changes in East Asia and their relation to the Himalaya-Tibetan Plateau uplift.

    We recently developed a new provenance tracing method by using a combination of Electron Spin Resonance (ESR signal intensity and Crystallinity Index (CI of quartz, and demonstrated that fine fraction of the surface sediments from nine major deserts in East Asia could be distinguished one another on the ESR signal intensity versus CI diagram. Here, we measured ESR signal intensity and CI of quartz in fine fractions of samples covering the last 7 Ma obtained from Lingtai section in the central Chinese Loess Plateau, and compared the results with those of the surface samples from nine major deserts in East Asia.

    The results suggest that the provenance of fine fraction of the eolian sediment in Lingtai section changed at 4.3, 2.1, 1.4, 1.1, 0.8 and 0.4 Ma. During 7 to 4.3 Ma, the dust might be have been supplied from Precambrian to Paleozoic metamorphic and granitic rocks and granite exposed in the present central to eastern part of the Tian Shan Mountains. The contribution from the Taklimakan desert appeared at 4.3 Ma, increased drastically at 1.1 Ma, and persisted till 0.8 Ma, whereas the main source of detrital material to the Taklimakan desert might have changed from eastern part of the Kunlun and the Altyn Mountains to western part of the Kunlun and the Tian Shan Mountains. During 0.8 to 0.4 Ma, contribution from the Badain Juran desert gradually increased. Finally, contribution from the Tengger desert appeared from 0.4 to 0 Ma. Together with tectonic evidences from literatures

  3. Check dam identification using multisource data and their effects on streamflow and sediment load in a Chinese Loess Plateau catchment

    Science.gov (United States)

    Tian, Peng; Zhao, Guangju; Mu, Xingmin; Wang, Fei; Gao, Peng; Mi, Zhijuan

    2013-01-01

    During the recent six decades, numerous check dams have been constructed for soil erosion control and agricultural production, and have become the key measure for soil and water conservation in the Loess Plateau. Obtaining check dam information is very important for soil erosion control and river basin management. This study utilizes remote-sensing images in conjunction with Google Earth images and field survey to derive the spatial distribution of the check dams in the Huangfuchuan catchment. Multisource data including topographic maps, Landsat images, and images from Google Earth are collected for check dam identification. The results are verified based on a field survey. The water surface area of the check dams derives from in situ measurement and images present good relationship with the high correlation coefficient of 0.96. Furthermore, the area extent and number of check dams derived from the remote sensing images are similar to those from Google Earth images. Historically, an increase in the check dam number, controlled area, and storage capacity indicate their substantial trapping effects on streamflow and sediment load in the Huangfuchuan catchment. This study may be a good reference for proposing an efficient approach to identify the check dams and provide decision supports for soil and water conservation in the Loess Plateau.

  4. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    1999-01-01

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

  6. Carbonate leaching processes in the Red Clay Formation, Chinese Loess Plateau: Fingerprinting East Asian summer monsoon variability during the late Miocene and Pliocene

    Science.gov (United States)

    He, Tong; Chen, Yang; Balsam, William; Qiang, Xiaoke; Liu, Lianwen; Chen, Jun; Ji, Junfeng

    2013-01-01

    High-resolution variations in carbonate minerals from the Jiaxian Red Clay section, located at the northern limit of the present East Asian summer monsoon (EASM) on Chinese Loess Plateau were quantified using Fourier transform infrared spectroscopy. We analyzed a large quantity of sediments dated from the late Miocene to Pliocene (8.2-2.6 Ma). The carbonates in this interval show high-frequency variations alternating between leached and calcareous horizons. The low carbonate contents and high values of magnetic susceptibility and high Rb/Sr ratios were found in the leached zones, a pattern that is consistent with that observed in the overlying Quaternary loess-paleosol sequences. This pattern suggests that East Asian Monsoon (EAM) rainwater enhanced leaching and accumulation processes of carbonate minerals in the Red Clay Formation in a way similar to the loess-paleosol sequence. Seven alternating leached and calcareous zones are identified, suggesting oscillations of the EASM and East Asian winter monsoon intervals. The calcareous zones were also found to have high Zr/Rb ratio. These indications of shifts from a strong EASM to East Asian winter monsoon dominance correlate well with the cooling transition indicated by deep sea δ18O isotopes. This evidence suggests that the EAM was active during the late Miocene and Pliocene and was similar to the Quaternary monsoon. The presence of a strong EAM during the Pliocene Warm Period also raises questions about the hypothesis that past and future warm climate conditions could produce a permanent El Niño-like state.

  7. Loess Plateau storage of Northeastern Tibetan Plateau-derived Yellow River sediment

    Science.gov (United States)

    Nie, Junsheng; Stevens, Thomas; Rittner, Martin; Stockli, Daniel; Garzanti, Eduardo; Limonta, Mara; Bird, Anna; Andò, Sergio; Vermeesch, Pieter; Saylor, Joel; Lu, Huayu; Breecker, Daniel; Hu, Xiaofei; Liu, Shanpin; Resentini, Alberto; Vezzoli, Giovanni; Peng, Wenbin; Carter, Andrew; Ji, Shunchuan; Pan, Baotian

    2015-01-01

    Marine accumulations of terrigenous sediment are widely assumed to accurately record climatic- and tectonic-controlled mountain denudation and play an important role in understanding late Cenozoic mountain uplift and global cooling. Underpinning this is the assumption that the majority of sediment eroded from hinterland orogenic belts is transported to and ultimately stored in marine basins with little lag between erosion and deposition. Here we use a detailed and multi-technique sedimentary provenance dataset from the Yellow River to show that substantial amounts of sediment eroded from Northeast Tibet and carried by the river's upper reach are stored in the Chinese Loess Plateau and the western Mu Us desert. This finding revises our understanding of the origin of the Chinese Loess Plateau and provides a potential solution for mismatches between late Cenozoic terrestrial sedimentation and marine geochemistry records, as well as between global CO2 and erosion records. PMID:26449321

  8. 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.

  9. 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

  10. 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.

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

    Directory of Open Access Journals (Sweden)

    Feng Wu

    2011-01-01

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

  12. 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

  13. 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.

  14. 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, J.; Van Oost, K.; Chen, L.; Govers, G.

    2015-09-01

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

  15. 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)

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

    OpenAIRE

    Wei GUO

    2016-01-01

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

  17. 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

  18. 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

  19. Lack of correlation between paleoprecipitation and magnetic susceptibility of Chinese loess/paleosol sequences

    OpenAIRE

    Guo, B.; Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China; Zhu, R. X.; Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China; Roberts, A. P.; Southampton Oceanography Centre, Southampton, UK; Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia

    2001-01-01

    We have conducted a detailed mineral magnetic study of loess unit 8 (L8) and paleosol unit 8 (S8) from three localities (Jingbian, Yichuan, and Duanjiapo) along a N-S transect in the Chinese loess plateau. As expected, the lowfield magnetic susceptibility (χ) has higher values in S8 and lower values in L8. Similarly, superparamagnetic particle concentrations increase in S8 with increasingly humid climates along the N-S transect, which suggests that pedogenic magnetic enhancement is r...

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Dolomite abundance in Chinese loess deposits: A new proxy of monsoon precipitation intensity

    Science.gov (United States)

    Meng, Xianqiang; Liu, Lianwen; Balsam, William; Li, Shilei; He, Tong; Chen, Jun; Ji, Junfeng

    2015-12-01

    Dolomite of detrital origin in carbonate-rich soil can help indicate the intensity of carbonate dissolution and leaching processes. Using Fourier transform infrared spectroscopy, we generated a high-resolution record of dolomite and calcite contents from eight sections on the Chinese Loess Plateau spanning the last 130 kyr. Based on the relative abundance of calcite and dolomite, four dissolution phases of carbonate minerals related to summer monsoon (SM) variations are identified as follows: (1) coexistence of dolomite and calcite indicating a very weak SM with a mean annual precipitation (MAP) leaching indicating a strong SM, 690 leaching of the underlying loess layer suggesting a very strong SM with MAP > 725 mm.

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

    Institute of Scientific and Technical Information of China (English)

    聂军胜; 昝金波; 宋友桂

    2012-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    谢巧勤; 陈天虎; 徐晓春; 孙玉兵

    2012-01-01

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

  7. Comparison of Measured and Simulated Water Storage in Dryland Terraces of the Loess Plateau, China

    Science.gov (United States)

    In the mountainous regions of China, developing sustainable agriculture requires implementing conservation management practices that prevent soil erosion and conserve soil and water resources. In the semiarid northwest Loess Plateau, the primary conservation management practice is terracing, which ...

  8. Plagioclase sub-species in Chinese loess deposits: Implications for dust source migration and past climate change

    Science.gov (United States)

    He, Tong; Liu, Lianwen; Chen, Yang; Sheng, Xuefen; Ji, Junfeng

    2016-01-01

    Plagioclase mineral sub-species in the Lingtai Section in central Chinese Loess Plateau are examined using Mineral Liberation Analyzer techniques, showing that loess and paleosol samples exhibit similar patterns in terms of plagioclase feldspar sub-species content. This suggests that both loess and paleosol units have preserved their primary Ca-bearing plagioclase compositions of loess source regions. Weighted average CaO (%) in Ca-bearing plagioclase lies within a narrow range and is equivalent to the average plagioclase composition for upper continental crust. This fact supports the hypothesis that Chinese loess deposits are the result of a thorough mixing of dust sources. The sum of Ca-bearing plagioclase content exhibits a general increasing trend superimposed by glacial-interglacial oscillations. In combination with observed plagioclase data in the deserts, the variations of Ca-bearing plagioclase minerals might be used as a proxy for dust source migration and climate changes in the loess source regions. Furthermore, linear relationship between lithogenic magnetic susceptibility (MS) component input and contents of Ca-bearing plagioclase in loess units revises a MS proxy for reconstructing paleo-monsoon precipitation history. The revised MS and plagioclase sub-species records help in understanding the mechanism of glaciation across northern Tibetan Plateau.

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

    Science.gov (United States)

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

    2000-08-01

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

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

    Science.gov (United States)

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

    2009-04-01

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

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

    OpenAIRE

    Guo, Bin; ZHANG Li

    2013-01-01

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

  12. 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

  13. 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 (pwater 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. PMID:24941017

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

    International Nuclear Information System (INIS)

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

  15. 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

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

    Science.gov (United States)

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

    2016-09-01

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

  17. Thermoluminescence dating of loess from the Potwar Plateau, northern Pakistan

    International Nuclear Information System (INIS)

    The loess deposits of northern Pakistan present a good opportunity for establishing a chronology using fine grain TL dating. The TL response of the 2-10 μm size fraction of polymineral (predominantly quartz/feldspar) mixtures is well behaved with linear dose-dependence and no anomalous fading. The loess horizons have very similar uranium and thorium contents, thus minimising dosimetry problems, and the fairly arid climatic conditions reduce the errors in water content estimation, at least for the uppermost horizons. A series of laboratory bleaching experiments reveal uncertainties in the absolute age estimates but not in their relative values. (author)

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

    Institute of Scientific and Technical Information of China (English)

    QiuPing FU; QuanJiu WANG; XinLei SHEN; Jun FAN

    2014-01-01

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

  19. 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), Pchanging climate. Such studies are essential if we are to meet the human water demand in the Loess Plateau region. PMID:27422727

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

    OpenAIRE

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

    2015-01-01

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

  1. 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.

  2. 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.

  3. Study of remote sensing monitoring of dynamic change of the Loess Plateau forest resources

    Science.gov (United States)

    Yuliang, Qiao; Ying, Wang; Junyou, Tang

    Taking for example Daning County, a key pilot area of ``the Three North Protection Forest Project'' in China's Loess Plateau, this article is to explore the method of using remote sensing technology to monitoring the dynamic change information of forest vegetation. It uses LANDSAT TM, CBERS-1 data and aerial remote sensing and ground investigation to monitoring the dynamic change of forest vegetation information of Daning County in three different periods - 1978, 1987 and 2000. The results of the research prove that, this method is worth widely popularized, by which the dynamic change information of the forest vegetation can be monitored simply and quickly so as to explore a scientific, rational and effective road for us to rectify the territory of China's Loess Plateau, change the poor physiognomy of this area, improve the ecological environment and promote the development of national economy.

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

    OpenAIRE

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

    2012-01-01

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

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

    OpenAIRE

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

    2012-01-01

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

  6. Calcium Nodules as a Proxy for Quaternary Paleoclimate Change on China’s Loess Plateau

    OpenAIRE

    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 e...

  7. Influence of Soil Moisture on Litter Respiration in the Semiarid Loess Plateau

    OpenAIRE

    Zhang, Yanjun; Guo, Shengli; Liu, Qingfang; Jiang, Jishao

    2014-01-01

    Understanding the response mechanisms of litter respiration to soil moisture in water-limited semi-arid regions is of vital importance to better understanding the interplay between ecological processes and the local carbon cycle. In situ soil respiration was monitored during 2010–2012 under various conditions (normal litter, no litter, and double litter treatments) in a 30-year-old artificial black locust plantation (Robinia pseudoacacia L.) on the Loess Plateau. Litter respiration with norma...

  8. 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.

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

    Institute of Scientific and Technical Information of China (English)

    LIUHuifang; WEITianxing; ZHUQingke

    2004-01-01

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

  10. 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.

  11. 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)

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

    Institute of Scientific and Technical Information of China (English)

    张涵丹; 卫伟; 陈利顶; 于洋; 杨磊; 贾福岩

    2015-01-01

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

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

    Science.gov (United States)

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

    2003-12-01

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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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. PMID:26379259

  20. 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. PMID:26633304

  1. 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. PMID:26633304

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

    Directory of Open Access Journals (Sweden)

    Wenming He

    Full Text Available 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.

  3. 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.

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

    DEFF Research Database (Denmark)

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

    2006-01-01

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

  5. 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.

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

    Science.gov (United States)

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

    2009-12-01

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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2008-01-01

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

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

    Science.gov (United States)

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

    2015-09-01

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

  14. 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.

  15. 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.

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

    Science.gov (United States)

    Zeng, Quanchao; Dong, Yanghong; An, Shaoshan

    2016-01-01

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

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

    Science.gov (United States)

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

    2015-04-01

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

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

    Science.gov (United States)

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

    2016-02-01

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

  19. 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

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

    Science.gov (United States)

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

  1. 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.

  2. Effects of coal gangue content on water movement and solute transport in a China loess plateau soil

    Energy Technology Data Exchange (ETDEWEB)

    Beibei, Zhou; Quanjiu, Wang [Institute of Water Resources and Hydro-electric Engineering, Xi' an University of Technology, Xi' an (China); State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, Shaanxi (China); Ming' an, Shao; Mingxia, Wen [State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, Shaanxi (China); College of Resources and Environment, Northwest A and F University, Yangling, Shaanxi (China); Horton, Robert [Department of Agronomy, Iowa State University, Ames, Iowa (United States)

    2010-11-15

    The mining industry has grown strongly in China in recent decades, resulting in large amounts of coal gangues, which cause water and soil pollution, soil erosion, and various other environmental problems. They are often used in reclamation projects in attempts to restore land damaged by mining, hence they are frequently present (in widely varying proportions) in the topsoil in areas around mines. Their presence can strongly affect key soil variables, including its bulk density, structure, water retention, water movement, and solute transport rates. In the study presented here, the effects of gangue contents on infiltration, saturated hydraulic conductivity, and solute transport parameters of a Chinese Loess plateau soil were examined. The results show that infiltration rates and saturated hydraulic conductivity decreased with increasing gangue content. The Peck-Watson equation modeled these relationships well, but Bouwer-Rice equations provided poorer matches with the acquired data. Cumulative infiltration over time was described well by both the Philip equation and Kostiakov equation. Both the simplified convection-dispersion equation and a two-region model described the solute transport processes well. In addition, the dispersion increased, while both the Peclet number and mobile water fraction decreased, with increases in gangue contents. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. 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.

  4. Heat balance and soil moisture in the Loess Plateau [Shanxi], China

    International Nuclear Information System (INIS)

    A three-layer soil model was used for clarifying the heat balance and soil water content in the Loess Plateau. China, and applied to actual bare soil fields (Tottori Sand Dune and Shenmu District, Shaanxi Province, China). The difference between the observed and calculated evaporation per day was approximately 0.18 mm (5 WmE-2) to 0.21 mm (6WmE-2). Because of its moderate mixture of sand, silt and clay, yellow loessial soil in Shenmu affects water retentivity and restriction of evaporation from the soil surface. The seasonal change of heat balance and soil water content was examined using meteorological data in Yulin near Shenmu. The annual means of sensible heat and latent heat flux were 23WmE-2 and 19WmE-2 (239mm per year), respectively. The soil water content of the second and third layers remained comparatively high in winter

  5. 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.

  6. Land suitability assessment on a watershed of Loess Plateau using the analytic hierarchy process.

    Directory of Open Access Journals (Sweden)

    Xiaobo Yi

    Full Text Available In order to reduce soil erosion and desertification, the Sloping Land Conversion Program has been conducted in China for more than 15 years, and large areas of farmland have been converted to forest and grassland. However, this large-scale vegetation-restoration project has faced some key problems (e.g. soil drying that have limited the successful development of the current ecological-recovery policy. Therefore, it is necessary to know about the land use, vegetation, and soil, and their inter-relationships in order to identify the suitability of vegetation restoration. This study was conducted at the watershed level in the ecologically vulnerable region of the Loess Plateau, to evaluate the land suitability using the analytic hierarchy process (AHP. The results showed that (1 the area unsuitable for crops accounted for 73.3% of the watershed, and the main factors restricting cropland development were soil physical properties and soil nutrients; (2 the area suitable for grassland was about 86.7% of the watershed, with the remaining 13.3% being unsuitable; (3 an area of 3.95 km(2, accounting for 66.7% of the watershed, was unsuitable for forest. Overall, the grassland was found to be the most suitable land-use to support the aims of the Sloping Land Conversion Program in the Liudaogou watershed. Under the constraints of soil water shortage and nutrient deficits, crops and forests were considered to be inappropriate land uses in the study area, especially on sloping land. When selecting species for re-vegetation, non-native grass species with high water requirements should be avoided so as to guarantee the sustainable development of grassland and effective ecological functioning. Our study provides local land managers and farmers with valuable information about the inappropriateness of growing trees in the study area along with some information on species selection for planting in the semi-arid area of the Loess Plateau.

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

    Institute of Scientific and Technical Information of China (English)

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

    2007-01-01

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

  8. 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.

  9. Early and middle Matuyama geomagnetic excursions recorded in the Chinese loess-paleosol sediments

    Science.gov (United States)

    Yang, Tianshui; Hyodo, Masayuki; Yang, Zhenyu; Ding, Lin; Fu, Jianli; Mishima, Toshiaki

    2007-07-01

    A detailed paleomagnetic and rock-magnetic investigation on the early and middle Matuyama loess-paleosol sediments has been carried out at the Baoji section, Shaanxi province, southern Chinese Loess Plateau. Our new magnetostatigraphy revises the position of the lower Olduvai boundary from L27 to S26. Seven shortlived geomagnetic excursions, tentatively named as E1, E2, E3, E4, E5, E6, and E7, have been recognized in the L13, S22, L26, L27, S29, and upper and middle parts of L32, respectively. Results of the anisotropy of low-field magnetic susceptibility (AMS) show that the studied loess-paleosol sediments retain the primary sedimentary fabric. Rock magnetic experiments reveal that the sediments from the excursional and polarity transitional intervals have the same magnetic characteristics as those from the surrounding normal and reversed polarity intervals. Assuming a constant accumulation rate between polarity boundaries, these seven excursions are estimated to be at about 1.11 Ma (E1), 1.58 Ma (E2), 1.92 Ma (E3), 2.11 Ma (E4), 2.25 Ma (E5), 2.35 Ma (E6), and 2.42 Ma (E7) Ma. The E1 and E2 in the middle Matuyama Chron can be correlated with the Punaruu and Stage 54 (Gilsa) excursions, respectively. The E4, E5, and E7 in the early Matuyama Chron can be correlated with the Réunion II, Réunion I, and cryptochron C2r.2r-1 (X-subchron), respectively. The E3 in the lower Olduvai subchron and E6 in the early Matuyama Chron have no comparable events. At present they can only be correlated with the anomalous directions observed in the Osaka Bay core (Biswas et al., 1999). Therefore, further investigations are necessary to support their global occurrences. The present result together with the two late Matuyama excursions dated at about 0.89 Ma and 0.92 Ma (Yang et al., 2004) show that the Baoji section yields at least nine Matuyama excursions which, along with the results of the study, suggests that eight excursions occur at 0.9-2.2 Ma (Channell et al., 2002), thereby

  10. 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.

  11. 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.

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

    OpenAIRE

    Tingting Ning; Wenzhao Liu; Wen Lin; Xiaoqiang Song

    2015-01-01

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

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

    OpenAIRE

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

    2015-01-01

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

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

    OpenAIRE

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

    2012-01-01

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

  15. 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.

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

    Directory of Open Access Journals (Sweden)

    X. M. Feng

    2012-03-01

    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, applying the basic theories to evaluate the regional effects of land cover change on water resources has been rarely done 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 modeled actual evapotranspiration (ET output. We constructed a monthly ET model using published eddy flux ET measurements, ET estimates derived from local 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 as a whole might have decreased (1–48 mm yr−1 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 yr−1, and 35% of the study area might have seen an increase with a range of 1–10 mm yr−1. 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. When compared to findings at the plot or catchment-scale, this study suggested that regional hydrologic effects

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

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

    Institute of Scientific and Technical Information of China (English)

    YAN YunXia; XU JiongXin

    2007-01-01

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

  5. Changes in soil carbon and nitrogen following land abandonment of farmland on the Loess Plateau, China.

    Directory of Open Access Journals (Sweden)

    Lei Deng

    Full Text Available The revegetation of abandoned farmland significantly influences soil organic C (SOC and total N (TN. However, the dynamics of both soil OC and N storage following the abandonment of farmland are not well understood. To learn more about soil C and N storages dynamics 30 years after the conversion of farmland to grassland, we measured SOC and TN content in paired grassland and farmland sites in the Zhifanggou watershed on the Loess Plateau, China. The grassland sites were established on farmland abandoned for 1, 7, 13, 20, and 30 years. Top soil OC and TN were higher in older grassland, especially in the 0-5 cm soil depths; deeper soil OC and TN was lower in younger grasslands (<20 yr, and higher in older grasslands (30 yr. Soil OC and N storage (0-100 cm was significantly lower in the younger grasslands (<20 yr, had increased in the older grasslands (30 yr, and at 30 years SOC had increased to pre-abandonment levels. For a thirty year period following abandonment the soil C/N value remained at 10. Our results indicate that soil C and TN were significantly and positively correlated, indicating that studies on the storage of soil OC and TN needs to focus on deeper soil and not be restricted to the uppermost (0-30 cm soil levels.

  6. 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.

  7. Joint analysis of changes in temperature and precipitation on the Loess Plateau during the period 1961-2011

    Science.gov (United States)

    Miao, Chiyuan; Sun, Qiaohong; Duan, Qingyun; Wang, Yafeng

    2016-02-01

    The Loess Plateau is particularly sensitive to climate change owing to its fragile ecological environment and geographic features. Here, we present a comprehensive analysis of the joint probabilistic characteristics and tendencies for bivariate and trivariate precipitation and temperature indices across the plateau, based on copula theory. The results show that the southeast region of the plateau had a higher potential for flooding: the 10-year return levels for the number of days with heavy and very heavy precipitation (R10mm, R20mm) and for the maximum 5-day precipitation value (RX5day) were higher in this region. The northwest region of the plateau, however, had a higher potential for drought, as reflected in the high and increasing 10-year return levels for the number of consecutive dry days (CDD) and the number of days with low precipitation (R1mm). In a joint analysis of precipitation indices, large areas of the Loess Plateau showed a relatively high risk of concurrent extreme precipitation events. However, the risk of concurrent extreme wet and dry events did not increase over the past half century, as demonstrated by nonsignificant changes in the probability of concurrently long CDD and long consecutive wet days (CWD). A trivariate copula analysis showed that some grid locations in the southeast of the plateau had an increasing risk of extreme precipitation events occurring at a high frequency and a high intensity, and forming a large percentage of the annual precipitation. Joint analysis of precipitation and temperature indices showed that the risk of higher temperatures and longer spells of consecutive dry days had increased over the past 50 years in grid locations scattered in the northern and southern regions: there were negative trends in the bivariate return periods for warm days (TX90p) and CDD. In addition, there was a decreased probability of concurrent long spells of consecutive wet days and colder temperatures, as demonstrated by the positive

  8. Weathering histories of Chinese loess deposits based on uranium and thorium series nuclides and cosmogenic 10Be

    International Nuclear Information System (INIS)

    The long, continuous deposition of dust in the Chinese loess plateau offers an unique opportunity to study the nature of soil weathering in a wide range of climatic conditions. In this paper we report on measurements of concentrations of U- and Th-series nuclides and of major cations in 150 loess and paleosol samples from five sites, going back 2.5 Ma. Using the results for 10Be concentrations in these soils, we determined the absolute amounts of water added to several soil units and obtained: (1) first-order leaching constants for U and several cations and (2) the compositions of the soils contributing to the dust-source regions and of the dust at deposition. Further, based on analyses of 230Th in soils deposited in the past ca. 140 ka, we determined when the soils weathered in the source regions. We conclude that most of the weathering in the dust-source regions may have occurred during the interglacials. 34 refs., 8 figs., 2 tabs

  9. 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

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

    Science.gov (United States)

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

    2014-12-01

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

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

    Institute of Scientific and Technical Information of China (English)

    AN Shaoshan; HUANG Yimei

    2006-01-01

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

  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. 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.

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

    Directory of Open Access Journals (Sweden)

    L. Yang

    2012-09-01

    Full Text Available Soil moisture in deep soil layers is an important relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the spatial variations of deep soil moisture with respect to the topographic conditions has significant importance for vegetation restoration. In this study, we focused on analyzing the spatial variations and factors influencing soil moisture content (SMC in shallow (0–2 m and deep (2–8 m soil layers, based on soil moisture observations in the Longtan watershed, Dingxi, Gansu province. The vegetation type of each sampling site for each comparison is same and varies by different positions, gradients, or aspects. The following discoveries were captured: (1 in comparison with shallow SMC, slope position and slope aspect may affect shallow soil moisture more than deep layers, while slope gradient affects both shallow and deep soil moisture significantly. This indicates that a great difference in deep soil hydrological processes between shallow and deep soil moisture remains that can be attributed to the introduced vegetation and topography. (2 A clear negative relationship exists between vegetation growth condition and deep soil moisture, which indicates that plants under different growing conditions may differ in consuming soil moisture, thus causing higher spatial variations in deep soil moisture. (3 The dynamic role of slope position and slope aspect on deep soil moisture has been changed due to large-scale plantation in semi-arid environment. Consequently, vegetation growth conditions and slope gradients may become the key factors dominating the spatial variations in deep soil moisture.

  15. 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.

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

    Directory of Open Access Journals (Sweden)

    Li-fang Wang

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

  17. 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.

  18. Dynamic monitoring of land-use change in Loess Plateau using multi-temporal Landsat TM data

    Science.gov (United States)

    Hou, Xiyong; Liu, Jiyuan; Gao, Zhiqiang; Zhuang, Dafang; Yu, Xinfang

    2004-11-01

    Loess Plateau is a unique region in the world where the human activities are very intensive and the eco-environment is highly frangible. During the past two decades, the Land Use/Cover Change has been considered as one of the most important reasons for the eco-environment degeneration in Loess Plateau. In this paper, land use data in 1990, 1995 and 2000 were got based on the Landsat TM Remote Sensing images, and the 1km-grid land use change data of 1990-1995, 1995-2000 and 1990-2000 was made using the data management and spatial analysis techniques of ArcGIS 8.3 software. Furthermore, statistical tabular data of Grain for Green Project on county level in recent years were joined in the administrative regionalism spatial data. Based on all of these data, temporal-spatial characteristics of land use change in Loess Plateau were studied in detail, and its driving forces were discussed either. It turned out that land use change in different periods had very different characteristics. On the whole, from 1990 to 2000, farmland and built-up increased greatly, and forest, grassland, water body and unused land decreased remarkably. On the contrary, conversions from farmland and unused to forest or grassland has become the dominant land use change process since 2000. The regional social-economic development and the national macro-control policy have been the most important driving forces of land use change since 1990. Especially, from 2000 to now, the widely implemented Grain for Green Project, under which farming on fragile land gives way to forestation, has become and will remain the most radical and effective driving force to both the land use change and the regional eco-environment restoration.

  19. [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. PMID:26259439

  20. 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...

  1. 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.

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

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

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

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

    Science.gov (United States)

    Xu, Guoce; Li, Zhanbin; Li, Peng

    2016-04-01

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

  4. Mass accumulation rate changes in Chinese loess during MIS 2, and asynchrony with records from Greenland ice cores and North Pacific Ocean sediments during the Last Glacial Maximum

    Science.gov (United States)

    Kang, Shugang; Roberts, Helen M.; Wang, Xulong; An, Zhisheng; Wang, Min

    2015-12-01

    Sensitivity-corrected quartz optically stimulated luminescence (OSL) dating methods have been widely accepted as a promising tool for the construction of late Pleistocene chronology and mass or dust accumulation rates (MARs or DARs) on the Chinese Loess Plateau (CLP). Many quartz OSL ages covering marine isotope stage (MIS) 2 (equal to L1-1 in Chinese loess) have been determined for individual sites within the CLP in the past decade. However, there is still a lack of detailed MAR or DAR reconstruction during MIS 2 across the whole of the CLP. Here, we present detailed MARs determined for eight sites with closely-spaced quartz OSL ages covering ∼MIS 2, and relative MARs suggested by a probability density analysis of 159 quartz OSL ages ranging from ∼30 to 10 ka ago, from 15 sites on the CLP. The results show enhanced dust accumulation during the Last Glacial Maximum (LGM), with particularly rapid dust accumulation from ∼23 to 19 ka ago (the late LGM). In contrast, MARs determined for the last deglaciation (from ∼19 to 12 ka ago) are low. The MAR changes during MIS 2 in Chinese loess are mainly controlled by the East Asian winter monsoon (EAWM) intensity, which is forced by Northern Hemisphere ice volume. The MAR changes also indicate that dust accumulation during MIS 2 is generally continuous at millennial time scales on the CLP. Comparison of Asian-sourced aeolian dust MARs in Chinese loess with those preserved in Greenland ice cores and North Pacific Ocean sediments indicates that rapid dust accumulation occurred from ∼26 to 23 ka ago (the early LGM) in Greenland ice cores and North Pacific Ocean sediments, suggesting a several kilo-year difference in timing when compared with the rapid dust accumulation during the late LGM in Chinese loess. This asynchronous timing in enhanced dust accumulation is probably related to both changes in the EAWM intensity and changes in the mean position of zone axis of the Westerly jet, both of which are greatly influenced

  5. 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.

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

    Directory of Open Access Journals (Sweden)

    Jun Zhai

    2015-03-01

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

  7. 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.

  8. 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.

  9. 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.

  10. 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

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

    Institute of Scientific and Technical Information of China (English)

    张玉萍; 孟丽君; 王芳; 鹿有贵; 贾静

    2014-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  14. 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. PMID:27124482

  15. 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

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

    International Nuclear Information System (INIS)

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

  17. 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.

  18. 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

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

    Institute of Scientific and Technical Information of China (English)

    Yini Han; Jianzhi Niu; Feizhou Wu

    2015-01-01

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

  20. Effects of conservation tillage practices on ammonia emissions from Loess Plateau rain-fed winter wheat fields

    Science.gov (United States)

    Yang, Yang; Zhou, Chunju; Li, Na; Han, Kun; Meng, Yuan; Tian, Xiaoxiao; Wang, Linquan

    2015-03-01

    Ammonia emissions from agricultural activities contribute to air pollution. For the rain-fed winter wheat system in the Loess Plateau there is a lack of information about ammonia emissions. Current study aimed to provide field data on ammonia emissions affected by conservation tillage practices and nitrogen applications. A two-year field experiment was conducted during 2011-2013 wheat growing seasons followed a split-plot design. Main plots consisted of one conventional tillage (CT, as the control) and five conservation tillage systems, i.e., stalk mulching (SM), film mulching (FM), ridge tillage (RT), ridge tillage with film mulch on the ridge (RTfm), and ridge tillage with film mulch on the ridge and stalk mulch in the furrow (RTfmsm); while subplots consisted of two nitrogen application rates, i.e., 0 and 180 kg N ha-1. Ammonia emissions were measured using an acid trapping method with vented chambers. Results showed ammonia fluxes peaked during the first 10 days after fertilization. On average, nitrogen application increased ammonia emissions by 26.5% (1.31 kg N ha-1) compared with treatments without nitrogen application (P soil ammonium, moisture, and temperature. Tillage systems had significant effects on ammonia emissions. On average, conservation tillage practices reduced ammonia emissions by 7.7% (0.46 kg N ha-1) compared with conventional tillage (P effective. Deep-band application of nitrogen fertilizer, stalk mulches, and film mulches were responsible for reductions in ammonia emissions from nitrogen fertilization in conservation tillage systems, thus they were recommended to reduce ammonia emissions from winter wheat production regions in the southern Loess Plateau.

  1. 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.

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

    Science.gov (United States)

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

    2009-12-01

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

  3. 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

  4. 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.

    2016-04-01

    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.

  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. Satellite evidence for significant biophysical consequences of the "Grain for Green" Program on the Loess Plateau in China

    Science.gov (United States)

    Xiao, Jingfeng

    2014-12-01

    Afforestation has been implemented worldwide as regional and national policies to address environmental problems and to improve ecosystem services. China's central government launched the "Grain for Green" Program (GGP) in 1999 to increase forest cover and to control soil erosion by converting agricultural lands on steep slopes to forests and grasslands. Here a variety of satellite data products from the Moderate Resolution Imaging Spectroradiometer were used to assess the biophysical consequences of the GGP for the Loess Plateau, the pilot region of the program. The average tree cover of the plateau substantially increased because of the GGP, with a relative increase of 41.0%. The GGP led to significant increases in enhanced vegetation index (EVI), leaf area index, and the fraction of photosynthetically active radiation absorbed by canopies. The increase in forest productivity as approximated by EVI was not driven by elevated air temperature, changing precipitation, or rising atmospheric carbon dioxide concentrations. Moreover, the afforestation significantly reduced surface albedo, leading to a positive radiative forcing and a warming effect on the climate. The GGP also led to a significant decline in daytime land surface temperature and exerted a cooling effect on the climate. The GGP therefore has significant biophysical consequences by altering carbon cycling, hydrologic processes, and surface energy exchange and has significant feedbacks to the regional climate. The net radiative forcing on the climate depends on the offsetting of the negative forcing from carbon sequestration and higher evapotranspiration and the positive forcing from lower albedo.

  7. 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%.

  8. 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

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

    OpenAIRE

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

    2014-01-01

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

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

    OpenAIRE

    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 aes...

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

    OpenAIRE

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

    2013-01-01

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

  12. 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.

  13. 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

  14. 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.

  15. 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.

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  18. 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.

  19. 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.

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

    Science.gov (United States)

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

    2015-01-01

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

  1. 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.

  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. [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) 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. PMID:24015535

  4. 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.

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

    Science.gov (United States)

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

    2015-12-01

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

  6. 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.

  7. 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.

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

    Institute of Scientific and Technical Information of China (English)

    WEI Zhigang; WEN Jun; LI Zhenchao

    2009-01-01

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

  9. 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.

  10. 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

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

    International Nuclear Information System (INIS)

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

  12. A comparison of natural- and laboratory-generated dose response curves for quartz optically stimulated luminescence signals from Chinese Loess

    International Nuclear Information System (INIS)

    It has previously been observed that laboratory-generated quartz optically stimulated luminescence (OSL) signals from different samples have similar dose response curves (DRCs) after they are normalized using a test dose. It therefore seems likely that growth of the normalized signal due to natural irradiation of quartz may also follow a general dose response curve. The existence of such a curve is investigated by constructing a natural DRC from the test dose-normalized natural OSL signals of seven samples from the Luochuan section of the Chinese Loess Plateau. The same aliquots are then used to build single aliquot regenerative (SAR) DRCs, making it possible to compare the natural and laboratory constructed curves. Two main differences are observed. Firstly, the laboratory-generated DRCs are best fitted with double saturating exponential functions whereas the natural DRC is equally well fitted with a single saturating function. Secondly, in the laboratory-generated DRCs the normalized OSL signal continues to increase at high laboratory doses (>500 Gy), whereas no growth is seen at these doses in the equivalent natural DRC. These differences between natural- and laboratory-generated DRCs are still apparent even if data are manipulated to isolate the fast component, or if a sensitivity corrected multiple aliquot regenerative (SC-MAR) dose procedure is used. This suggests that the observed differences are not due to the influence of different components or inter-regenerative dose cycle sensitivity changes. The divergence between the natural- and laboratory-generated DRC means that the current maximum limit of quartz OSL dating at the Luochuan section is 150 Gy, as De estimates above this value are likely to be underestimations.

  13. 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.

  14. 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 (< 0.05 mm) and fine sand (0.25-0.05 mm). The overall gradients of the trends for silt-clay and fine sand are 0.0622 (slight increase) and - 0.0618 (slight decrease), respectively, for Shipanmao, and - 0.8415 (decrease) and 0.8448 (increase), respectively, for Zhangshan. There are considerable differences in the PSDs among different layers, especially in the coarse and fine sand fractions. The coefficient of variation (CV) for the coarse sand fraction is highest, followed by the fine sand and the silt-clay size fractions. Larger 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

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

    Science.gov (United States)

    Sun, Caili; Liu, Guobin; Xue, Sha

    2016-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

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

  18. 137Cs budget during the period of 1960s in a small drainage basin on the Loess Plateau of China

    International Nuclear Information System (INIS)

    A sediment profile with a thickness of 28.12 m in a failed reservoir in a small catchment of the Yuntaishan Gully in the Loess Plateau of China consisted of 44 flood couplets deposited during the period from 1960 to 1970 with total volume of 2.36 x 106 m3. Specific sediment yields for a flood event varied from 300 t km-2 to 14,400 t km-2 and annual sediment yields varied from 2500 t km-2 in 1966 to 40,000 t km-2 in 1964 with a mean value of 12,700 t km-2 a-1 for the period. Average annual 137Cs concentrations of the sediments increased from 0.92 Bq kg-1 in 1960 to 4.82 Bq kg-1 in 1963, then decreased to 1.53 Bq kg-1 in 1970. The total 137Cs activity in the reservoir sediments was 9.22 x 109 Bq, which accounted for 31.9% of the total 137Cs fallout precipitation of 2.89 x 101 Bq within the catchment during the period. The proportion of the 137Cs loss from the catchment to the 137Cs fallout precipitation within the catchment in a year varied between 8.01% and 66.8%, and it was 20.9% for the peak 137Cs deposition year of 1963 and 52.0% in 1964. By analysis of the 137Cs budget in the catchment for the 137Cs peak precipitation period from 1962 to 1964, the 137Cs surface enrichment coefficient Γ should be much less than 0.23. And for calculation of soil losses on the cultivated land in the inter-gully area by using the Mass Balance Model II, the value of Γ should be 0.05-0.1

  19. 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.

  20. Changes of streamflow and sediment discharge at multi-temporal scales and the responses to human activities and climate variability in the Yanhe watershed of Loess Plateau, China

    Science.gov (United States)

    Gao, Guangyao

    2014-05-01

    To control the severe soil erosion in the Loess Plateau and reduce the sediment transported into the China's Yellow River, a great number of soil conservation measures including terracing, afforestation, pasture establishment and construction of sediment trapping check dams have been implemented across the Loess Plateau since the 1950s. These measures have resulted in large-scale land use and land cover change, which had substantial effects on streamflow and sediment discharge with combination of climate variability. In this work, the Yanhe watershed in the middle part of Loess Plateau was chosen as the study area, and hydro-climatic data during 1952-2011 were collected. The changes of streamflow and sediment discharge at multi-temporal scales (annual, flood season, monthly and daily scales) as well as those of precipitation and potential evaportranspiration were investigated. A water balance model based on Budyko hypothesis was used to quantitatively assess the impacts of human activities and climate variability on streamflow, and their contributions to changes of sediment discharge was evaluated by the regression method. The precipitation and potential evaportranspiration showed negative and positive trends, respectively, but not at significant level. Significant decreasing trends (Ppoints all occurred in 1996. Overall, human activities contributed more than climate variability to streamflow (66% vs. 34%) and sediment discharge (81% vs. 19%) decline. Among the soil conservation measures, construction of sediment-trapping dams appeared to be the main cause of the reduced streamflow and sediment discharge, which also made the sediment grain more fine. Future catchment management should consider more sustainable measures such as pastureland to reduce soil erosion while not significantly affecting streamflow, and the spatial organization of land management actions deserves much more attention.

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

    Science.gov (United States)

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

    2016-02-15

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

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  3. Effect of water content on strontium retardation factor and distribution coefficient in Chinese loess.

    Science.gov (United States)

    Huo, Lijuan; Qian, Tianwei; Hao, Junting; Liu, Hongfang; Zhao, Dongye

    2013-12-01

    Geological burial and landfill are often employed for disposal of nuclear wastes. Typically, radionuclides from nuclear facilities transport through the unsaturated zone before reaching the groundwater aquifer. However, transport studies are often conducted under saturated and steady-state flow conditions. This research aimed to examine the effects of unsaturated flow conditions and soil water content (θ) on Sr sorption and retardation in Chinese loess through 1D column transport experiments. Reagent SrCl2 was used as a surrogate for the radioactive isotope ((90)Sr) in the experiment because of their analogous adsorption and transportation characteristics. The spatial distribution of Sr along the column length was determined by segmenting the soil bed and analysing the Sr content in each soil segment following each column breakthrough test. The single-region (SR) and two-region (TR) models were employed to interpret the transport data of Sr as well as a tracer (Br(-)), which resulted in the dispersion coefficient (D) and retardation factor (Rd) under a given set of unsaturated flow conditions. For the tracer, the SR and TR models offered nearly the same goodness of fitting to the breakthrough curves (R(2) ≈ 0.97 for both models). For the highly sorptive Sr, however, the TR model provided better fitting (R(2), 0.80-0.96) to the Sr retention profiles than the SR model (R(2), 0.20-0.89). The Sr retention curves exhibited physical non-equilibrium characteristics, particularly at lower water content of the soil. For the unsaturated soil, D and the pore water velocity (v) displayed a weak linear correlation, which is attributed to the altering dispersivity as the water content varies. A much improved linear correlation was observed between D and v/θ. The retardation factor of Sr increased from 69.1 to 174.2 as θ decreased from 0.46 to 0.26 (cm(3) cm(-3)), while the distribution coefficient (Kd) based on Rd remained nearly unchanged at various θ levels. These

  4. Effect of water content on strontium retardation factor and distribution coefficient in Chinese loess

    International Nuclear Information System (INIS)

    Geological burial and landfill are often employed for disposal of nuclear wastes. Typically, radionuclides from nuclear facilities transport through the unsaturated zone before reaching the groundwater aquifer. However, transport studies are often conducted under saturated and steady-state flow conditions. This research aimed to examine the effects of unsaturated flow conditions and soil water content (θ) on Sr sorption and retardation in Chinese loess through 1D column transport experiments. Reagent SrCl2 was used as a surrogate for the radioactive isotope (90Sr) in the experiment because of their analogous adsorption and transportation characteristics. The spatial distribution of Sr along the column length was determined by segmenting the soil bed and analysing the Sr content in each soil segment following each column breakthrough test. The single-region (SR) and two-region (TR) models were employed to interpret the transport data of Sr as well as a tracer (Br−), which resulted in the dispersion coefficient (D) and retardation factor (Rd) under a given set of unsaturated flow conditions. For the tracer, the SR and TR models offered nearly the same goodness of fitting to the breakthrough curves (R2 ≈ 0.97 for both models). For the highly sorptive Sr, however, the TR model provided better fitting (R2, 0.80–0.96) to the Sr retention profiles than the SR model (R2, 0.20–0.89). The Sr retention curves exhibited physical non-equilibrium characteristics, particularly at lower water content of the soil. For the unsaturated soil, D and the pore water velocity (v) displayed a weak linear correlation, which is attributed to the altering dispersivity as the water content varies. A much improved linear correlation was observed between D and v/θ. The retardation factor of Sr increased from 69.1 to 174.2 as θ decreased from 0.46 to 0.26 (cm3 cm−3), while the distribution coefficient (Kd) based on Rd remained nearly unchanged at various θ levels. These results

  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 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.

  8. Soil C, N, P and Its Stratification Ratio Affected by Artificial Vegetation in Subsoil, Loess Plateau China.

    Science.gov (United States)

    Deng, Jian; Sun, Pingsheng; Zhao, Fazhu; Han, Xinhui; Yang, Gaihe; Feng, Yongzhong; Ren, Guangxin

    2016-01-01

    Artificial vegetation restoration can induce variations in accumulation and distribution of soil carbon (C), nitrogen (N) and phosphorus (P). However, little is known about variations in soil C, N and P nutrient fraction stratification following artificial vegetation in Loess Plateau China. Based on the hypothesis that re-vegetated can improve soil quality and stratification ratios (SR) can be used as an indicator to evaluate soil quality. This study measured contents and storages of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) and their SRs in topsoil (0-20 cm) and subsoil (20-60 cm) in three 30-year re-vegetated lands that had been converted from arable land (Robinia pseudoacacia L., Caragana Korshinskii Kom. and abandoned cropland with low interferences and few management measures) and one slope cropland (SC) as a control for three soil profiles(0-20 cm, 20-40 cm and 40-60 cm) from June 2009 to June 2013. The results showed that the contents and storages of SOC, TN and TP in re-vegetated land were significantly higher than those in the SC in both topsoil and subsoil. The storages of SOC, TN and TP in the topsoil (0-20 cm) of the re-vegetated lands increased by 16.2%-26.4%, 12.7%-28.4% and 16.5%-20.9%, respectively, and increased by smaller but significant amounts in subsoil from 2009 to 2013. The SRs for SOC, TN and TP in the re-vegetated lands were mostly >2 (either for 0-20:20-40 cm or 0-20:40-60 cm) and greater than that in the SC. The SRs showed an increasing trend with increasing restoration age. The results also showed that the land use type and soil depth were the most influential factors for the SRs and storages, and the SRs of SOC and TN had significantly positive correlations with their storages. The SRs were concluded to be a good indicator for evaluating the soil quality, which can be significantly enhanced through vegetation restoration. Moreover, vegetation restoration can significantly enhance SOC, TN and TP accumulation

  9. 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

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

    International Nuclear Information System (INIS)

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

  11. Red TL of quartz extracted from Chinese loess: Bleachability and saturation dose

    International Nuclear Information System (INIS)

    The red TL of quartz has been shown to exhibit a much higher saturation dose than that of the UV emission in quartz, and thus has the potential to considerably extend the dating range. Unlike heated materials, in which the luminescence signal has been completely thermally reset, the quartz red TL from Aeolian sediments accumulates on top of a residual signal left after daylight bleaching. The characteristics of this bleaching process must be investigated before any dating attempts can be made. It is demonstrated in this paper that the red TL of quartz extracted from Chinese loess: (1) bleachable by sunlight, but with high residual level. Up to about 40% of the natural signal remains after bleaching in our sample; all of the broad natural TL peak bleaches simultaneously in sunlight; (2) has significant dose-dependent sensitivity change when laboratory doses beyond 1500Gy are applied; this sensitivity change cannot be corrected for by a test dose; and (3) has a D0 value of ∼550Gy, much larger than that of optically stimulated luminescence (OSL) (∼90Gy) from the same sample

  12. 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.

  13. [Effect of Below-cloud Secondary Evaporation in Precipitations over the Loess Plateau Based on the Stable Isotopes of Hydrogen and Oxygen].

    Science.gov (United States)

    Jin, Xiao-gang; Zhang, Ming-jun; Wang, Sheng-jie; Zhu, Xiao-fan; Dong, Lei; Ren, Zheng-guo; Chen, Fen-li

    2015-04-01

    Based on stable isotopes in 409 precipitation samples provided by GNIP and meteorological records at the eight stations in Loess Plateau from January 1985 to December 2004, as well as the trajectory model of HYSPLIT 4.9, the spatial and temporal variations of d-excess and Δ18O were analyzed. The spatial distribution of secondary evaporation rate and the impact of meteorological factors on below-cloud secondary evaporation were also discussed. The result showed that: (1) During summer and winter monsoon periods, Δ18O showed an uptrend variation and d-excess showed a downtrend variation from south to north in Loess Plateau. From east to west, Δ180 showed an uptrend variation only in summer monsoon period and a downtrend variation in winter monsoon period. The value of d-excess also showed a downtrend variation. Amplitude of variation Δ18O and d-excess could indicate the routes of monsoon. (2) Secondary evaporation existed on an annual basis, and it was relatively significant during the summer monsoon period, with ranges from 1.51% to 5.88% and an average rate of 3.87%. While winter monsoon became lower, the rates ranged from 1.06% to 5.46%, and the average rate dropped to 3.03%. Monsoon had larger influence on secondary evaporation in margin area of the plateau, while the influence on the central stations was little. (3) Temperature had the highest contribution to secondary evaporation, followed by precipitation amount and water vapor pressure, and relative humidity had a small contribution. Moreover, the influence of wind speed and altitude on secondary evaporation was weak. PMID:26164896

  14. 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

  15. Using multi-approaches to investigate the effects of land cover on runoff and soil erosion in the Loess Plateau of China

    Science.gov (United States)

    Gao, G.; Fu, B.; Liu, Y.; Wang, Y.

    2012-12-01

    This study used the in-situ measurement, model simulation and radioisotope tracing methods to investigate the effects of land cover on runoff and soil erosion at plot and hillslope scales in the Loess Plateau of China. Three runoff plot groups covered by sparse young trees (Group 1), native shrubs (Group 2) and dense tussock (Group 3) with different revegetation time were established in the Yangjuangou catchment of Loess Plateau. Greater runoff was produced in plot groups (Group 2 and Group 3) with higher vegetation cover and longer restoration time as a result of soil compaction processes. Both of the runoff coefficient and soil loss rate decreased with increasing plot length in Group 2 and Group 3 plots. The runoff coefficient increased with plot length in Group 1 plots located at the early stage of revegetation, and the soil loss rates increased over an area threshold. Therefore, the effect of scale on runoff and soil erosion was dependent on restoration extent. The antecedent moisture condition (AMC) was explicitly incorporated in runoff production and initial abstraction of the SCS-CN model, and the direct effect of runoff on event soil loss was considered in the RUSLE model by adopting a rainfall-runoff erosivity factor. The modified SCS-CN and RUSLE models were coupled to link rainfall-runoff-erosion modeling. The modified SCS-CN model was accurate in predicting event runoff from the three plot groups with Nash-Sutcliffe model efficiency (EF) over 0.85, and the prediction accuracy of the modified RUSLE model was satisfactory with EF values being over 0.70. The 137Cs tracing technique was used to examine soil erosion under different land uses and land-use combinations. The results show that the order of erosion rate in different land uses increases sequentially from mature forest to grass to young forest to orchard to terrace crop. The land-use combinations of 'grass (6 years old) + mature forest (25 years old) + grass (25 years old)' and 'grass (6 years old

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

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

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

  17. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2008-01-01

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

  19. Using 137Cs and 210Pb to assess the sediment sources in a dam reservoir catchment on the loess plateau, China

    International Nuclear Information System (INIS)

    As the part of integrated studies of soil erosion and sedimentation within the same reservoir catchment, 'Sedimentation Assessment Studies' supported by IAEA, the primary scientific objective is to determine the source types of sediments reaching the reservoir and their relative contribution of different spatial locations to dam reservoir. This study addresses the need to quantify and link dam reservoir sedimentation, land use and different landscape locations using the 137Cs and 210Pb techniques within a GIS frame. A brief description of the basis for the site selection, sampling strategy, and the first results on the spatial distributions of 137Cs content and the possible sources of sediment and the relative contributions of these potential sources within the Yangjuangou dam reservoir catchment, Loess Plateau are provided. (3 figs., 4 tabs.)

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

    Directory of Open Access Journals (Sweden)

    Bing Wang

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

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

    Science.gov (United States)

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

    2016-07-01

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

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

    Science.gov (United States)

    Wang, Bing; Wen, Fenxiang; Wu, Jiangtao; Wang, Xiaojun; Hu, Yani

    2014-01-01

    Characterization of soil water content (SWC) profiles at catchment scale has profound implications for understanding hydrological processes of the terrestrial water cycle, thereby contributing to sustainable water management and ecological restoration in arid and semi-arid regions. This study described the vertical profiles of SWC at the small catchment scale on the hilly and gully Loess Plateau in Northeast China, and evaluated the influences of selected environmental factors (land-use type, topography and landform) on average SWC within 300 cm depth. Soils were sampled from 101 points across a small catchment before and after the rainy season. Cluster analysis showed that soil profiles with high-level SWC in a stable trend (from top to bottom) were most commonly present in the catchment, especially in the gully related to terrace. Woodland soil profiles had low-level SWC with vertical variations in a descending or stable trend. Most abandoned farmland and grassland soil profiles had medium-level SWC with vertical variations in varying trends. No soil profiles had low-level SWC with vertical variations in an ascending trend. Multi-regression analysis showed that average SWC was significantly affected by land-use type in different soil layers (0-20, 20-160, and 160-300 cm), generally in descending order of terrace, abandoned farmland, grassland, and woodland. There was a significant negative correlation between average SWC and gradient along the whole profile (Psustainable water management in these small catchments on the Loess Plateau as well as in other complex terrains with similar settings. PMID:25313829

  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

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

    Science.gov (United States)

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

    2009-12-01

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

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

    Institute of Scientific and Technical Information of China (English)

    胡春生; 潘保田; 苏怀

    2012-01-01

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

  7. 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.

  8. 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

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

    Science.gov (United States)

    Li, Hongchen; Zhao, Xining; Gao, Xiaodong

    2015-04-01

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

  10. 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

  11. [Soil organic carbon mineralization of Black Locust forest in the deep soil layer of the hilly region of the Loess Plateau, China].

    Science.gov (United States)

    Ma, Xin-Xin; Xu, Ming-Xiang; Yang, Kai

    2012-11-01

    The deep soil layer (below 100 cm) stores considerable soil organic carbon (SOC). We can reveal its stability and provide the basis for certification of the deep soil carbon sinks by studying the SOC mineralization in the deep soil layer. With the shallow soil layer (0-100 cm) as control, the SOC mineralization under the condition (temperature 15 degrees C, the soil water content 8%) of Black Locust forest in the deep soil layer (100-400 cm) of the hilly region of the Loess Plateau was studied. The results showed that: (1) There was a downward trend in the total SOC mineralization with the increase of soil depth. The total SOC mineralization in the sub-deep soil (100-200 cm) and deep soil (200-400 cm) were equivalent to approximately 88.1% and 67.8% of that in the shallow layer (0-100 cm). (2) Throughout the carbon mineralization process, the same as the shallow soil, the sub-deep and deep soil can be divided into 3 stages. In the rapid decomposition phase, the ratio of the mineralization or organic carbon to the total mineralization in the sub-deep and deep layer (0-10 d) was approximately 50% of that in the shallow layer (0-17 d). In the slow decomposition phase, the ratio of organic carbon mineralization to total mineralization in the sub-deep, deep layer (11-45 d) was 150% of that in the shallow layer (18-45 d). There was no significant difference in this ratio among these three layers (46-62 d) in the relatively stable stage. (3) There was no significant difference (P > 0.05) in the mineralization rate of SOC among the shallow, sub-deep, deep layers. The stability of SOC in the deep soil layer (100-400 cm) was similar to that in the shallow soil layer and the SOC in the deep soil layer was also involved in the global carbon cycle. The change of SOC in the deep soil layer should be taken into account when estimating the effects of soil carbon sequestration in the Hilly Region of the Loess Plateau, China. PMID:23323422

  12. 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

  13. 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.

  14. Depth persistence of the spatial pattern of soil-water storage along a small transect in the Loess Plateau of China

    Science.gov (United States)

    Li, Xuezhang; Shao, Ming'an; Jia, Xiaoxu; Wei, Xiaorong; He, Liang

    2015-10-01

    Knowledge of the spatial patterns of soil-water storage (SWS) in soil profiles is important for understanding the dynamics of soil water between surface and subsurface soil layers in semiarid area. We investigated the depth persistence of the overall and scale-specific spatial patterns of SWS for different soil layers during different seasons. Soil-water contents were measured using a neutron probe on 22 occasions in 2012 and 2013 along a 1340-m transect over several sub-watersheds in the Liudaogou catchment on the Loess Plateau of China. Similarities in the spatial patterns of SWS were analyzed by Spearman's rank correlations and wavelet coherency. A spatiotemporal analysis indicated that the temporal evolution of the SWS profiles differed between the growing and non-growing seasons and that landscape position and soil texture determined the amount of SWS at each sampling location. Spearman's rank correlations were significant between any two layers within different seasons, and the correlation coefficients decreased as the distance between layers increased. Clay content controlled the spatial pattern of SWS between layers at large scales. The SWS spatial pattern had a higher depth persistence during the non-growing season than during the growing season, and the soil layer had a larger effect than season on the similarity in SWS spatial patterns. These results can improve our understanding of the hydrological processes in soil profiles and can be of considerable value in the application of hydrological models and in water management.

  15. 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.

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

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    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.

  17. Volatile Compounds of Young Wines from Cabernet Sauvignon, Cabernet Gernischet and Chardonnay Varieties Grown in the Loess Plateau Region of China

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    Zhenwen Zhang

    2010-12-01

    Full Text Available In order to elucidate the aroma components of wine produced in the Loess Plateau region of China, volatile compounds of young wines from Cabernet Sauvignon, Cabernet Gernischet and Chardonnay varieties grown in the new ecological region were investigated for the first time in this research. Among the volatile compounds analyzed by HS-SPME with GC-MS, a total of 45, 44 and 42 volatile compounds were identified and quantified in Cabernet Sauvignon, Cabernet Gernischet and Chardonnay wines, respectively. In the volatiles detected, alcohols formed the most abundant group in the aroma compounds of the three wines, followed by esters and fatty acids. According to their odor active values (OAVs, 18 volatile compounds were always present in the three wines at concentrations higher than their threshold values, but ethyl octanoate, ethyl hexanoate, and isoamyl acetate were found to jointly contribute to 92.9%, 93.3%, and 98.7%, of the global aroma of Cabernet Sauvignon, Cabernet Gernischet and Chardonnay wines, respectively. These odorants are associated with “fruity’’ and ‘‘ripe fruit’’ odor descriptors.

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

    Science.gov (United States)

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

    2016-01-01

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

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

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    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.

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

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    Xuan Fang

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

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

    Science.gov (United States)

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

    2014-01-01

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

  2. 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.

  3. 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

  4. On the factors influencing surface-layer energy closure and their seasonal variability over the semi-arid Loess Plateau of Northwest China

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    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.

  5. Variations in energy consumption and survival status between rural and urban households: A case study of the Western Loess Plateau, China

    International Nuclear Information System (INIS)

    As energy consumption is closely related to all aspects of human life, it becomes the standard by which to measure people's quality of life and the national development level. Based on the “energy ladder” hypothesis, we conducted questionnaire surveys in the Western Loess Plateau of China, and accessed a considerable amount of information about the energy usage of rural and urban households. The results show that the per capita effective heat is 323.3, 282.8, 250.0 and 123.6 kgce in the provincial capital, medium-sized cities, county towns and rural areas, respectively. The energy ladder feature is obvious. Using 719 sample data, the multiple regression analysis was conducted between per capita effective heat and two independent variables including per capita income and the attributes of energy used, the parameter estimation of the cross-quadratic model produced more significant effects. The three-dimensional graph clearly shows the differences in living standards and survival status between urban and rural households. High-income residents in urban areas consume more high-quality energy, they enjoy an affluent lifestyle. While low-income households in rural areas obtain less effective heat, and use poor quality fuels, they are still at the level of basic survival. - Highlights: ► The per capita effective heat is 323.3.4, 282.8, 250.0 and 123.6 kgce in four types of region. ► The energy attributes score of a rural resident is 60% of that of an urban resident. ► The energy ladder feature is obvious. ► The effective heat is the result of two independent variables interacting together. ► The differences in living standards and survival status between urban and rural households are great.

  6. 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.

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

    Science.gov (United States)

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

    2014-01-01

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

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

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    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.

  9. 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. PMID:25893832

  10. 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. PMID:26305354

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

    Directory of Open Access Journals (Sweden)

    H. Yu

    2010-05-01

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

  12. 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.

  13. 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.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2015-08-01

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

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

    Science.gov (United States)

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

    2016-10-15

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

  18. 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.

  19. Evaluation of the Soil Water Index and Surface Soil Moisture on the Loess Plateau%土壤湿度指数在黄土高原的适宜性评价

    Institute of Scientific and Technical Information of China (English)

    蒋冲; 王飞; 穆兴民; 李锐

    2012-01-01

    In this paper,the capability of the European Remote Sensing Satellite(ERS) scatterometer-derived soil water index(SWI) and surface soil moisture(SSM) data which are retrieved by a change detection method,developed at the Institute of Photogrammetry and Remote Sensing(IPF),Vienna University of Technology(TU-Wien) to disclose soil moisture and precipitation distribution on Loess Plateau is investigated with the help of GIS,remote sensing and correlation analysis.Monthly averaged SWI/SSM data for the years 1992—2000 are analyzed to evaluate the use of the SWI/SSM as an index to monitor soil moisture on Loess Plateau and to investigate whether it can reflects general precipitation distribution characteristics in this area or not.Monthly averaged in situ relative soil moisture and monthly precipitation data from Chinese meteorological gauge stations are employed to perform comparisons with SWI/SSM on point and regional scales.The result is that in different land use,soil texture and topography conditions SWI/SSM correlate well with precipitation and in situ relative soil moisture,most of them reach significant level,they have same change tendency,SWI and precipitation have similar spatial distribution characteristics.Among the seven stations,there is a good correlation between precipitation and soil water content(SWI and in situ relative soil moisture),especially for first 10 cm layer,the correlation between precipitation and SWI is better than that of precipitation and in situ moisture.The results show that SWI/SSM can relative accurately disclose soil moisture variation and spatial distribution characteristic on the Loess Plateau.Furthermore,the freely available 20-yr(1992—2011) time series SWI/SSM data are thus a valuable tool to overcome the scarcity of in situ soil moisture observation,which are usually not available on regional scale.%利用1992—2000年间黄土高原地区逐月降雨量、实测土壤湿度数据,结合GIS遥

  20. 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.

  1. Temporal stability of soil moisture under different land uses/cover in the Loess Plateau based on a finer spatiotemporal scale

    Directory of Open Access Journals (Sweden)

    J. Zhou

    2013-08-01

    Full Text Available The Temporal stability of soil moisture (TSSM is an important factor to evaluate the value of available water resources in a water-controlled ecosystem. In this study we used the evapotranspiration-TSSM (ET-TSSM model and a new sampling design to examine the soil water dynamics and water balance of different land uses/cover types in a hilly landscape of the Loess Plateau under a finer spatiotemporal scale. Our primary focus is to examine the difference among soil water processes, including the wet-to-dry (WTD process triggered by precipitation and the dry-to-wet (DTW process caused by radiation among varied land uses/cover types. Three vegetation types and bare land were selected in the sampling scheme. For each land uses/cover type, four microplots (60 cm × 60cm were established, and the soil moisture was measured at the central point (CP and four ambient points (AP. The results indicated that (1 the bare land (plot1 was sensitive to the influence of rainfall and radiation compared with other land uses types; (2 Andropogon (plot2 and Spiraea pubescens (plot4 more efficiently represented the average soil moisture of the different land uses/cover in the WTD and DTW processes, respectively, in the CP position. In contrast, the bare land and Artemisia coparia (plot3 seemed to be more representative of the average soil water content in the AP position; (3 the ET-TSSM model demonstrated that, in the WTD processes, although Spiraea pubescens land use reached the net deficit of the soil water storage condition was longest, the vegetated land uses have a higher capacity of water consumption than bare land and more easily affected the serious condition of the soil water deficiency at the end of WTD processes. We concluded that a finer spatiotemporal scale in the TSSM study could be a new method to describe the effect of plant on soil moisture dynamics triggered by precipitation or radiation and that the improvement of the application of the TSSM

  2. Assessing and regulating the impacts of climate change on water resources in the Heihe watershed on the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Climate change can cause considerable changes in water resources and assessing the potential impacts can provide important information for regional sustainable development. The objectives were to evaluate the possible impacts of climate change during 2010-2039 on water resources (runoff, soil water content, and evapotranspiration) in the Heihe watershed on the Loess Plateau of China and to further explore adaptive measures to cope with the changes. Projections of four climate models (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emission scenarios (A2, B2, and GGa) were used to estimate future changes in precipitation, maximum and minimum temperature based on Change Factor method. The Soil and Water Assessment Tool (SWAT) was employed to simulate the hydrologic responses to climate changes. The CA-Markov model was used to develop land use scenarios. Compared with the present climate, the climate models predicted a -2.3% to 7.8% change in annual precipitation, 0.7 to 2.2°C rises in maximum temperature, and 1.2 to 2.8°C rises in minimum temperature. Without consideration of land use change, SWAT predicted a -19.8% to 37.0% change for runoff, -5.5% to 17.2% change for soil water content, and 0.1% to 5.9% increase for evapotranspiration during 2010–2039 under all climate scenarios. Though the change of hydrometeorolocial variables are complex, they would possibly increase with great probability, and the hydrological regime would be influenced such as a decrease in runoff in winter months. With land use changes, the projected land use of 2015 would increase soil water content by 4.0% and surface runoff by 5.7% while slightly decrease evapotranspiration by 0.6% compared with the 2000 land use. This result showed that adjustment of land use patterns was capable of regulating water resources and could be used to mitigate the adverse effects of climate change.

  3. Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework.

    Science.gov (United States)

    Gao, Guangyao; Fu, Bojie; Wang, Shuai; Liang, Wei; Jiang, Xiaohui

    2016-07-01

    Understanding and quantifying the impacts of land use/cover change and climate variability on hydrological responses are important to the design of water resources and land use management strategies for adaptation to climate change, especially in water-limited areas. The elasticity method was used to detect the responses of streamflow and runoff coefficient to various driving factors in 15 main catchments of the Loess Plateau, China between 1961 and 2009. The elasticity of streamflow (Q) and runoff coefficient (Rc) to precipitation (P), potential evapotranspiration (E0), and catchment characteristics (represented by the parameter m in Fu's equation) were derived based on the Budyko hypothesis. There were two critical values of m=2 and E0/P=1 for the elasticity of Q and Rc. The hydrological responses were mainly affected by catchment characteristics in water-limited regions (E0/P>1), and in humid areas (E0/Pclimate conditions played a more important role for cases of m>2 whereas catchment characteristics had a greater impact for cases of m<2. The annual Q and Rc in 14 of the 15 catchments significantly decreased with average reduction of 0.87mmyr(-1) and 0.18%yr(-1), respectively. The mean elasticities of Q to P, E0 and m were 2.66, -1.66 and -3.17, respectively. The contributions of land use/cover change and P reduction to decreased Q were 64.75% and 41.55%, respectively, while those to decreased Rc were 75.68% and 32.06%, respectively. In contrast, the decreased E0 resulted in 6.30% and 7.73% increase of Q and Rc, respectively. The contribution of land use/cover changes was significantly and positively correlated with the increase in the percentage of the soil and water conservation measures area (p<0.05). The Rc significantly and linearly decreased with the vegetation coverage (p<0.01). Moreover, the Rc linearly decreased with the percentage of measures area in all catchments (eight of them were statistically significant with p<0.05). PMID:27016681

  4. 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

  5. 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

  6. 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

  7. 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.

  8. Soil moisture consumption and ecological effects in alfalfa grasslands in Longdong area of Loess Plateau%陇东黄土高原苜蓿草地土壤水分消耗及水分生态效应

    Institute of Scientific and Technical Information of China (English)

    胡守林; 贾志宽; 万素梅

    2009-01-01

    Soil desiccation is the most serious problem, which leads to widespread land degradation in the Loess Plateau of China. Hence, it has important theoretical significance to study the consumption patterns of soil moisture in alfalfa grasslands so as to realize sustainable agricultural development and ecological environment rehabilitation in the entire Loess Plateau. Changes of soil moisture characteristics in 0-1000 cm soil and the effects on ecological environment of soil moisture in alfalfa grasslands were investigated. The results showed that: (1) In 0-1000 cm soil, the grasslands with alfalfa growing for four years, six years had the best soil moisture conditions, while the grasslands with alfalfa growing for twelve years, eighteen years and twenty-six years had the poorest soil moisture conditions. (2) In the Loess Plateau, emerging regional and extent of dry soil layer differed in alfalfa grasslands. (3) The grasslands with alfalfa growing for four years, six years and eight years did not produced unfavorable impacts on ecological environments of soil moisture, but the grasslands with alfalfa growing for twelve years, eighteen years and twenty six years had a profound negative impact on ecological environments of soil moisture. The study considered that in Longdong Loess Plateau, grass-crop rotation should be practiced to recover soil moisture so as continue to raise land productivity, after alfalfa grew for more than six years.%黄土高原地区土壤干化导致林草植被大面积衰退,研究苜蓿草地土壤水分消耗规律对该区农业持续发展及生态环境恢复具有重要的理论意义.该文研究了黄土高原地区不同生长年限苜蓿草地1 000 cm土层土壤水分的变化特征及其对土壤水分生态环境的影响.结果表明:在0~1 000 cm土层,4年、6年生苜蓿草地土壤水分条件最好;12年、18年、26年生苜蓿草地土壤水分条件最差.在黄土高原地区,苜蓿地土壤干层出现的

  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. Sustainability of Smallholder Agriculture in Semi-Arid Areas under Land Set-aside Programs: A Case Study from China’s Loess Plateau

    OpenAIRE

    Qirui Li; Amjath-Babu, T.S.; Peter Zander; Zhen Liu(Pittsburgh Particle physics, Astrophysics, and Cosmology Center, Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara St., Pittsburgh, PA 15260, U.S.A.); Klaus Müller

    2016-01-01

    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 ...

  11. Effects of Soil and Water Conservation of Algae Crust in Hilly and Gully Regions on Loess Plateau%黄土高原沟壑区藻类结皮的水土保持效应

    Institute of Scientific and Technical Information of China (English)

    康磊; 孙长忠; 殷丽; 汤志敏; 贺淑霞

    2012-01-01

    The effect of soil and water conservation of algae crust widespread in hilly and gully regions on Loess Plateau had been researched from two aspects which were rainfall infiltration-runoff and evaporation of soil water.The results were as follows: ①Algae crust could increase the 0-10 cm depth soil porosity.The maximum increase of total porosity was 7.4%,and the capillary was 14.2%.Algae crust had no significant effect on the soil porosity of the deeper layer.②In wasterland,mongolian scotch pine and Chinese pine forest,the runoff between the algae crust and non-crust had a significant difference.Compared with the runoff of non-crust,the runoff of algae crust in the three types of vegetation reduced by 28.1%~32.5%,34.4%~43.1% and 30.8%~31.6%.③In the three types vegetation,the amount of soil erosion between algae crust and non-crust had a significant difference.Compared with the amount of soil erosion of non-crust,the amount of soil erosion of algae crust in the three types of vegetation reduced by 58.8%~70.6%,48.9%~62.6% and 38.3%~57.1%.④By stepwise regression analysis,the different regression equations between runoff,soil erosion of algae crust and rainfall factor in different vegetation types could be obtained.⑤The soil moisture of 20-60 cm depth could be affect by algae crust.In this depth the soil moisture of algae crust was significantly higher than non-crust zone.%从降雨径流、水分蒸发两方面探讨黄土高原沟壑区藻类结皮的水土保持效应。结果表明:①藻类结皮可显著增加0-10cm土层内土壤孔隙度,最大增加幅度总孔隙度为7.4%,毛管孔隙度为14.2%;对更深土层的土壤孔隙度无显著影响。②荒草坡、樟子松林和油松林3种植被类型下,有藻类结皮试验区径流量与无结皮对照区有显著差异,径流量分别减少了28.1%~32.5%、34.4%~43.1%和30.8%~31.6%。③3种植被类型下,藻类结皮的土壤侵蚀量与无结皮对照土壤侵蚀量有

  12. MECHANISM OF LARGE-SCALE SLIDE AT EDGE OF LOESS PLATEAU ON NORTH OF WEIHE RIVER IN BAOJI URBAN AREA,SHAANXI PROVINCE%宝鸡渭河北岸黄土塬边大型滑坡成因机制研究

    Institute of Scientific and Technical Information of China (English)

    石菊松; 李滨; 吴树仁; 王涛; 辛鹏

    2013-01-01

    滑坡成因机制是深入认识、合理评价与有效防治滑坡的关键难点,其中黄土滑坡成因机制一直是中国工程地质界的研究热点问题之一。利用DEM,Quick bird影像与地面调查相结合完成了宝鸡市区渭河北岸黄土塬边大型滑坡详细编录与GIS制图,结合典型滑坡的钻探、物探成果,利用第四纪地质的最新成果,重建了渭河河谷构造地貌演化过程、查清了斜坡地层岩性组合、获得了新近系黏土地层工程地质特性参数和活动断裂的特征,初步建立了宝鸡渭河北岸黄土塬边大型黄土滑坡的概化模型。初步研究认为:(1)宝鸡渭河北岸在上新世-早更新世时期古地形由北向南渐低,古地貌由山前冲洪积平原向古三门湖变化,且古三门湖逐渐消亡,早更新世晚期现今渭河形成且主流总体向北偏移,直至全新世偏离北岸,形成现今地貌格局的地貌演化过程。(2)黄土塬边渭河北缘断裂为晚更新世以来的活动正断裂系,其不仅是地下水的导水通道,而且为滑坡后壁和次级滑面的形成提供了可追踪的软弱结构面。(3)渭河北岸黄土塬边古、老滑坡是在渭河侧蚀和地下水作用下,追踪断裂面沿新近系硬黏土界面或硬黏土层内部发生的地堑地垒式多级坡基旋转、坡体平移或复合型滑坡,是受新近系三趾马红土或三门系黏土地层和断裂控制的特殊类型黄土滑坡。%Landslide mechanism is the key of understanding,reasonable assessment,effective prevention and con-trol of landslides.It is quite difficult to achieve.Meanwhile,loess landslide mechanism has been one of the research hotspots in Chinese engineering geological circles over last decades.This study carries out detailed landslide survey and inventory combined with typical large scale slide drilling and geophysical exploration at the edge of loess plateau on north of Weihe river in

  13. 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

  14. Nitrogen fertilization effect on dryland soil water balance and winter wheat yield in the Chinese Loess Plateau

    Science.gov (United States)

    Continuous N fertilization to dryland winter wheat (Triticum aestivum L.) for a long period may have detrimental effect on grain yield due to high water consumption and soil acidity development. We evaluated the effect of five N fertilization rates (0, 45, 90, 135, and 180 kg N ha-1) on soil water b...

  15. 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

    ) and thermally transferred OSL (TT-OSL) signals. Since both the latter are associated with systematic uncertainties due to the potential (a)-thermal instability of these signals, a search continues for alternative, and demonstrably stable luminescence signals that can cover the entire Quaternary...... timescale. Here we explore the violet stimulated luminescence (VSL) signal at the Luochuan section, which provides a continuous archive of homogenous sediment with favourable luminescence characteristics and a solid independent age framework. By testing several VSL protocols and their associated performance......, we 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...

  16. Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau

    OpenAIRE

    Jian, Shengqi; Zhao, Chuanyan; Fang, Shumin; Yu, Kai

    2014-01-01

    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 tra...

  17. 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

  18. 黄土丘陵沟壑区坡面尺度土壤水分空间变异及影响因子%Spatial patterns of soil moisture at transect scale in the Loess Plateau of China

    Institute of Scientific and Technical Information of China (English)

    姚雪玲; 傅伯杰; 吕一河

    2012-01-01

    Understanding the spatial variability and impact factors of soil moisture is important when modeling the antecedent soil moisture status of a catchment. Soil moisture is a limiting factor of ecosystem development in semi-arid and arid areas. Soil moisture spatial patterns and impact factors are particularly important for ecosystem restoration in the semi-arid areas of the Loess Plateau. This study identifies soil moisture spatial patterns and impact factors (terrain, land use types and wet season) in Yangjuangou catchment in north of the Loess Plateau from the measurement of soil moisture in the top 100 cm soil layer along five different transects on a loess hill before and after the wet season. Statistical analysis revealed that the soil moisture spatial variation in deeper soil ( > 40cm) was more significant than that in upper soil ( planted R. pseudoacacia forest land (8 years) > planted R. pseudoacacia forest land (20 years) > planted Hippophae reamnoides forest land, no matter before or after the wet season. Although the topography of planted forest land has advantageous conditions (shading slope, lower position, smaller gradient or terraces) for retaining soil moisture, the soil in planted land was still found to be have a much lower soil moisture content than the soil in natural grasslands, especially in deeper soil. Thus it is considered that the influence of terrain on soil moisture content is masked by the influence of surface vegetation. Therefore, when modeling hydrological processes in the Loess Plateau, it is recommended that the pattern of vegetation types within the simulated area should be paid special attention. Hydrologic models of the Loess Plateau based only on terrain properties should be used cautiously. The soil moisture content at all sample sites increased after the wet season, however, the spatial patterns of soil moisture was not significantly changed. Sites which had high soil moisture content relative to other sites before the wet

  19. 黄土高原沟壑区苜蓿生产力及养分特性的研究%Alfalfa productivity and plateau characteristics in a gully region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    折凤霞; 郝明德; 臧逸飞

    2013-01-01

    在长期定位试验的基础上,研究了黄土高原沟壑区粮草轮作中苜蓿产草量及其养分变化特性.结果表明,苜蓿产草量一年生最低,为8 763 kg/hm2,3年生产草量达到最高,为12 020 kg/hm2,4年生产草量为9 665 kg/hm2,开始出现下降.1年生苜蓿对氮、磷、钾的吸收量最低,分别为218 kg/hm2,11 kg/hm2,105 kg/hm2,3年生苜蓿对磷、钾的吸收量最高,分别为23 kg/hm2和185 kg/hm2,比1年生苜蓿吸磷量高109.1%、吸钾量高76.2%;而4年生苜蓿对氮的吸收量最高,为351 kg/hm2,比1年生苜蓿吸氮高61%.土壤有机质、全氮和碱解氮含量逐年增加,有机质由15.60 g/kg增至18.26 g/kg,全氮由1.20 g/kg增至1.50 g/kg,碱解氮由64.74 mg/kg增至88.02mg/kg;土壤全磷、速效磷及速效钾含量逐年下降,全磷由0.86 g/kg降至0.76 g/kg,速效磷由14.00mg/kg降至9.27 mg/kg,速效钾由70.51 mg/kg降至54.35 mg/kg.建议在生产中施适量钾肥满足苜蓿高品质、高产量的需要.%Alfalfa (Medicago sativa) plant yield and nutrient change characteristics of forage crop rotation were studied in a long-term experiment in the gully region of the Loess Plateau. The one-year Medicago yield was 8 763 kg/ha (the lowest) and the three-year Medicago yield was 12 020 kg/ha (the highest) but the four-year yield fell to 9 665 kg/ha. The N, P, K uptake (218, 11, 105 kg/ha respectively) in one-year Medicago was the lowest. The P, K uptake of three-year Medicago was the highest (23 kg/ha and 185 kg/ha respectively) and compared with one-year Medicago, the P uptake was 109. 1% higher and the K uptake was 76, 2% higher. The N uptake of four-year Medicago was the highest, about 351 kg/ha, which was 61% higher than one-year Medicago. Soil organic matter, total nitrogen and alkali solution nitrogen content increased each year, organic matter increased form 15. 60 to 18. 26 g/kg, total nitrogen increased from 1, 20 to 1. 50 g/kg, and alkali solution nitrogen increased from 64

  20. Soil and Water Loss and Coping Mechanism on Loess Plateau in Qing Dynasty%清代黄土高原水土流失及社会应对机制

    Institute of Scientific and Technical Information of China (English)

    李荣华

    2015-01-01

    清代黄土高原水土流失极为严重,直接影响着黄河中下游地区人民的生产生活。面对此问题,中央政府及大部分地方政府没有形成系统、有效的治理机制,只是个别地方官带领民众进行植树造林。民间社会通过植树造林、梯田以及建设拦泥淤地工程、修建沟头防护工程等措施进行应对,他们所采取的许多方法不受官方重视,没有被总结、改良与推广。这一时期的应对机制不够健全,官方与民间社会互动不足,导致黄土高原水土流失问题无法得到有效治理。%Soil and water loss was serious on loess plateau in Qing dynasty and this brought enormous influenceto people's life in the middle and lower reaches of the Yellow River. Facing this problem, the central government and most of the local government did not form systematic and effective govern-ance mechanism and some individual local officials led peopleplant tree only. Folk society carried out coping-style that was tree planting, constructing terrace, and buildingconstruction for sediment retention and farmland-making, gully head protection. Many of these methods had not been paid attention and summarized, improved, extended by the official. Coping mechanisms was not enough healthiness in this time and interaction was not deficient in the official and folk society, these led soil and water loss on loess plateau effectivelycontrol.

  1. Normative Research of Pollination by Osmia Cornifrons on Apple in the Weibei-loess Plateau%渭北高原区苹果壁蜂授粉技术的规范研究

    Institute of Scientific and Technical Information of China (English)

    马志峰; 郭民主; 王荣花; 王智民

    2012-01-01

    In order to standard the pollination technology by Osmia comifivns of orchardist which lived in the Weibei-loess plateau, the effect of Osmia out of cocoon by the different styles, the place of nest boxes and the tube of nest on leaving the cocoon was studied by comparison method. The results showed that stripping the cocoon method was the best way, which had the highest ratio of breaking through and nidification. The height of nest boxes should be 20 cm above ground. The nest ratio of bulrush and paper were higher than that of plastic tube.%为了规范渭北高原苹果产区应用壁蜂授粉技术.通过田间试验研究了壁蜂不同释放方法、巢箱高度、巢材管对壁蜂出茧速度、出茧率、营巢管率等的影响.结果表明:剥茧放蜂法出茧速度最快、出茧率和营巢管率最高.巢箱距地面20cm左右营巢管率最高.纸巢管和芦苇巢管的营巢管率显著高于塑料巢管.

  2. 长期施用氮肥和磷肥对渭北旱塬土壤中氨氧化古菌多样性的影响%Effects of Long-term Nitrogen and Phosphate Fertilization on Diversity of Ammonia-Oxidizing Archaea in Dry Highland Soil of Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    武传东; 闫倩; 辛亮; 王保莉; 曲东

    2012-01-01

    Ammonia-oxidizing archaea are likely the most abundant ammonia-oxidizing microbes in natural environment and they also play an important role in nitrification. In order to improve nitrogen use efficiency and explicate the indicating function of ammonia-oxidizing ar-chaea( AOA) on changes of soil quality in the Loess Plateau, AOA community structure diversity was studied. The soil samples used in this research derived from Changwu Agro-ecological Experimental Station on the Loess Plateau, Chinese Academy of Sciences, which had received 23 years continuous fertilization treatments, include CK (control, without fertilizers), LD (unplanted, without fertilizers), N(nitrogen input), P(phosphorus input) and NP(combination of nitrogen and phosphorus fertilizers). The soil AOA community structure diversity was analyzed by restriction fragment length polymorphism(PCR-RFLP) and DNA sequence. Positive clones collected randomly from clone libraries were digested by Rsa I and Msp I, respectively. According to the statistics of diversity index, there were 25, 18, 29, 20 and 30 restriction endonuclease types(OTUs), respectively. The a diversity indices indicated that there was a pronounced difference among five fertilizer treatments. The OTUs were the highest in both P treatment and CK treatment, while the lowest in NP treatment. The rescaled distance matrix tree indicated that the different fertilization had weak convergence of AOA community types with the CK treatment soil. Phylogenetic tree of amoA gene amino acid sequences analysis showed all AOA sequences fell within cluster S and cluster M, but the proportions were different. These results indicated that long-term fertilization resulted in change of AOA community diversity; however, different fertilizer alkaline soil had no significant impact on the species composition of dominant AOA.%采用基于氨单加氧酶基因的PCR-RFLP和DNA测序技术,以黄土高原旱地黑垆土为材料,研究长期施用氮肥和磷肥对

  3. Magnetic properties derived from a loess section at the northern piedmont of Tianshan Mountains, Xinjiang, China, and their paleoenvironmental significance

    Science.gov (United States)

    Li, Guanhua; Xia, Dunsheng; Jia, Jia; Zhao, Shuang; Gao, Fuyuan; Wang, Youjun; Lu, Hao; Chen, Fahu

    2015-11-01

    Loess deposits in the arid Central Asia contain valuable information on the evolution of local aridification and dust sources in the Northern Hemisphere. Xinjiang is located in the eastern part of Central Asia and previous researches have revealed the complex enhancement of magnetic susceptibility in loess-paleosol sequences. However, systematic magnetic archives of loess deposit in this arid Asian interior are still far from adequate. In this study, magnetic parameters combined with nonmagnetic properties (granulometry and chromaticity) were analysed on a loess section in Shawan (SW), northwestern China. The section shares a similar magnetic composition with those in the Chinese Loess Plateau (CLP) as well as other sites in Xinjiang. Ferrimagnetic components (magnetite and maghemite) dominate the magnetic signal while the contribution of antiferromagnetic phases (like hematite and goethite) and paramagnetic portions are relatively low. There is no specific correlation between magnetic concentration and pedogenic intensity in the SW section. In general, magnetic enhancement was largely influenced by the paleowind intensity. However, a positive correlation between magnetic susceptibility and pedogenesis is observed in the upper part (0-3.5 m depths), which is characterized by a moderate wind intensity. Moreover, pedogenesis might be responsible for the enhancement of fine magnetic particles in paleosols. Magnetic properties are controlled by coarse magnetic particles in the pseudo-single domain state, but a coarse stable single domain phase was found in certain paleosol samples. The input of detrital fractions from a nearby dust source probably controlled the magnetic properties while a superparamagnetic fraction, which has been deemed as a product of pedogenesis in the CLP, is limited in the SW section. Caution is needed to employ magnetic susceptibility directly for paleoclimatic assessment because of its uncertainty in the Xinjiang loess. However, the

  4. 黄土高原汾河流域地表景观演变特征研究%Study on the Surface Landscape Changes in Fenhe River Basin of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    侯志华; 马义娟

    2013-01-01

    黄土高原是中国高度脆弱的生态系统之一,基于2000年和2008年两期TM遥感影像,以黄土高原脆弱区独立的流域单元——汾河流域为例,综合运用GIS和RS技术及景观生态学的基本原理与方法,分析该流域地表景观特征及其变化趋势,同时利用DEM数据,探讨景观演变的空间分异规律,为进一步研究流域景观演变驱动机制提供有价值的信息.结果表明:(1)农田、森林、草地始终是该流域的主要景观构成,但绝对优势景观(农田)所占比例大幅下降;(2)就整体景观尺度而言,形状趋于规则,连通性增强,多样性增大,蔓延度下降,整体景观格局受人为活动的干扰越来越强;(3)流失的农田主要流向了草地、森林和聚落,成为该流域8 a来主要的景观演变类型;(4)农田向聚落景观的演变主要发生在地势平坦、海拔低的中部两大盆地地区,农田向林草景观的演变则主要发生在海拔较高、坡度较大的上游、中游南部以及中下游外围的山地丘陵区.%The Loess Plateau is one of the most ecologically fragile regions in China. A case study was conducted in an independent basin unit in the eco-fragile region of the Fenhe River basin on the Loess Plateau based on Landsat-TM image respectively made in 2000 and 2008 and integrated by the means of the technology of RS and GIS as well as the theory of landscape ecology, the change tendency of landscape pattern was analyzed, and digital elevation model (DEM) was used to discuss the spatial distribution of the major landscape change types to provided valuable information for studying the driving force of the landscape changes. The results showed; (1) farmland, forest and grass were the main landscape types all along. Moreover, although the farmland element had the absolute superiority over the other two, it sharply decreased during the study period; (2) by analyzing the landscape pattern of the whole area, we found that the

  5. 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、

  6. 黄土高原坡面刺槐林土壤水分生态位特征分析%Characters of soil moisture niche-fitness of locust forest in the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    孟秦倩; 蔡焕杰; 王健; 张青峰

    2009-01-01

    通过定位观测并引入土壤水分生态位适宜度,以刺槐林根系分布作为土壤水分生态位权重,对黄土高原刺槐林不同地理位置、不同坡向和不同时期土壤水分生态位进行了分析.结果表明:由南向北,土壤水分生态位递减,淳化刺槐林土壤水分生态位为97.5%,可满足刺槐生长,米脂刺槐林土壤水分生态位为53.2%,林木生长较大受水分的限制;在不同坡向间刺槐林土壤水分生态位表现为阴坡最高,阳坡最低,在生长季节,刺槐的生长受土壤水分的制约,半阴坡和半阳坡介于二者之间;在年内,春旱及春末旱,导致土壤储水量减少,7月初土壤水分生态位降到最低.随着林龄和林木密度的增加,土壤水分生态位降低,保持适当的林分密度,可实现林木的正常生长.%The soil moisture of locust forest at different period and slope aspect from different geographic locations in the Loess Plateau is analyzed with the help of the model of the moisture niche-fitness. The results show that the value of the soil moisture niche-fitness of locust forest declines gradually from the South(Chunhua County, 97.5%) to the North (Mizhi County, 53.2%) of the Loess Plateau. The growth of the locust forest is affected more by the soil moisture factor. The highest value of the moisture niche-fitness is in the north-slope, while the lowest is in the south-slope. During the growth period in a year, the drought in spring can reduce the soil moisture capacity, and it can even cause the lowest soil moisture niche-fitness at the beginning of July. Along with the increase of the age and thickness of stand, the soil moisture niche-fitness is in a downward trend. So the suitable density of stand can promote the growth of the forest.

  7. 甘肃黄土高原水热气候异常阶段特征%Analysis of Abnormality of Water and Heat Resources in Gansu Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    郭林; 张凯; 王毅荣; 雷俊

    2013-01-01

    利用1960~ 2004年相关地面实测气象资料,分析甘肃黄土高原地区水热气候异常变化的阶段性特征.结果表明,该地区地表变暖最为突出,夏半年增幅明显大于冬半年,地温随深度加深增温幅度越大;降水日数减少,连阴雨天气时段缩短、过程雨量减少,无雨时段增长,日照出现2次突变、呈现下降趋势;降水日数在1991年后突变减少,最长连续降水日数及过程降水量在1978年后突变减少.%Based on surface meterological data from 34 weather stations in Gansu during 1960-2004,the abnormal variation of water and heat resources on the Gansu loess plateau was analyzed by using weighted average,wavelet analysis and EOF (empirical orthogonal function).Results show that the ground temperature increased obviously after 1983,the increasing amplitude in summer was more than that in winter,and the increasing amplitude of groud temperature was bigger with depth deepening.The rainfall days decreased obviously after 1991,the length of successive raining days shorteued and no rain days extended,the longest continuous rainfall days and procession precipitation decreased after 1978.The sunshine hours also presented decreasing trend.

  8. 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

  9. 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

  10. 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.

  11. 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,...

  12. Characterization of Argentine Loess and Paleosols by Moessbauer Spectroscopy

    International Nuclear Information System (INIS)

    We have used Moessbauer spectroscopy to investigate iron-bearing mineral samples of loess and paleosols from a geologic section at La Plata, Argentina, 34 deg. 54' 14'' S and 58 deg. 2' W. Hematite is by far the dominant iron-bearing magnetic component in initial loess and paleosol samples. The samples were also subjected to magnetic separation. The magnetically enriched loess fractions show a remarkable increase in the content of magnetite. The enhancement of non-magnetic Fe3+ and a decrease of Fe2+ mineral phases in the paleosol layer seem to be a consequence of the process of pedogenesis which also caused a dissolution of magnetic iron oxides by weathering. The increase of magnetite in the silt fraction suggests that the wind could have been the main carrier of magnetic minerals, causing the major differences in the magnetic parameters between loess and paleosols in the Argentine loess plateau

  13. 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.

  14. Study on the characteristics of soil moisture and water potential at the vadose zone in the Loess Plateau of East Gansu%陇东黄土塬区土壤包气带水分水势特征研究

    Institute of Scientific and Technical Information of China (English)

    王云权; 周向阳; 马金珠

    2011-01-01

    选取陇东黄土包气带为研究对象,综合运用数理统计与对比分析相结合的方法,研究黄土地区包气带土壤水分、水势变化特征和土水势构成结构,结果发现,在陇东黄土塬区,坡头荒地等较干旱、沙质土壤中,包气带水分变化呈对数分布特征,而耕作土壤其水分含量特征则不满足这种类型.在土水势构成方面,溶质势所占比例平均约为20%,其中坡头荒地约占15%,耕地中约占25%;基质势所占比例最大,在坡头荒地占近80%,耕地样本的平均比例超过60%.溶质势各分势构成方面,起主导作用的阴离子为HCO,起主导作用的阳离子为Ca.黄土塬区HCO和Ca所占溶质势的比重分别约为50%和25%;Na和Cl各约占10%.%This paper studys soil moisture distribution and composition of soil water energy at unsaturated zone in East Gansu. The results are as follows: Soil water mass content characteristics are logarithmic in the more arid Potou wasteland,sand and non-cultivated soil in the Loess Plateau of East Gansu, while moisture content of the arable soil is affected by its soil texture, displaying quite difference. In the unsaturated zone of the Loess Plateau, the proportion of solute potential is about 15% at Potou wasteland, while it can be up to about 25% in the farmland. Matric potential accounts for nearly 80% in Potou of the arable and is 60% in average content in farmland, which is of the largest proportion of the soil water pertential. HCO3- plays a leading role of anios in the solute potential of the unsaturated zone, and leading cation is Ca2 + in the loess area. Soil solute potential in the weight of the plasma ions is the largest HCO3- and Ca2+ , which is about 50% and 25% respectively of the solute potential in the Loess Plateau, Na+ and Cl- are about 10%.

  15. Evaluation on ecotourism suitability in frangile environment of loess plateau based on RS and GIS-exampled on Zhongyang county, Shanxi province%基于RS、GIS的黄土高原环境脆弱区生态旅游适宜度评价——以山西省中阳县为例

    Institute of Scientific and Technical Information of China (English)

    李会琴; 侯林春; 肖拥军; 薛重生

    2009-01-01

    Evaluation on ecotourism suitability is a key to tourism exploitation in loess plateau with fragile environment, which can provide references for ecotourism planning, choosing places, products programming. Consequently, it can reduce the bad impacts on environment effectively. According to the characteristic of ecotourism resources in loess plateau, this paper built some evaluation indexes and model of ecotourism suitability. By RS image, the author picked up indexes information, such as terrain, vegetation and loess physiognomy. Using spatial and buffer analysis methods of GIS, this paper realized quantative evaluation and spatial continuity of ecotourism suitability. Thereby, the author put forward a method in ecotourism suitability evaluation in loess plateau. Finally, taking Zhongyang county in Shanxi province as a case study, they analyzed ecotourism suitability in this county and educed the optimum area, preferable area, medium area and inferior area of ecotourism. Furthermore, the paper brought forward the plans on ecotourism and some problems should be noticed.%生态旅游适宜度评价为黄土高原环境脆弱区旅游开发提供产品开发、项目选址、旅游分区等方面的决策依据,从而有效降低旅游活动对环境的影响.根据黄土高原区域特征及生态旅游资源的特点,论文构建了黄土高原生态旅游适宜度评价因子和模型.并基于RS、GIS空间信息技术,实现了地形、植被、黄土地貌等6个评价因子的信息采集与评价结果的空间显示,提出了黄土高原生态旅游适宜度评价方法.以山西省中阳县为例进行了实证研究,得到了南川河河谷为该县生态旅游最适宜区、吴家峁黄土地貌等为中适宜区以及一般适宜区和不适宜区.根据评价结果,论文最后提出了该县生态旅游的开发方向及应注意的问题.

  16. 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.

  17. 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.

  18. 黄土高原水土保持林对土壤水分的影响%Soil moisture dynamics of water and soil conservation forest on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    张建军; 李慧敏; 徐佳佳

    2011-01-01

    黄土高原植被恢复的限制因素主要是土壤水分,植被与土壤水分关系的研究对黄土高原植被恢复具有重要意义.2008年7月1日至2009年10月31日间采用EnviroSMART土壤水分定位监测系统以每30min监测1次的频度,对晋西黄土区刺槐人工林地、油松人工林地、次生林地的土壤水分变化进行了研究.研究得出:次生林地0-150 cm土层中平均蓄水量为331.95mm,刺槐人工林地为233.85 mm,有整地措施的油松人工林地为314.85mm,刺槐人工林比次生林多消耗的98.10mm土壤水分主要来源于80 cm以下土层.次生林主要消耗0-80 cm土层的水分,而人工林不但对0-80 cm土层水分的消耗量大于次生林,对深层土壤的消耗也较次生林大,这将有可能导致人工林地深层土壤的“干化”.在土壤水分减少期(11-1月)刺槐人工林土壤水分的日均损耗量为0.86mm、油松人工林为0.82 mm、次生林为0.84 mm.土壤水分缓慢恢复期(2-5月)刺槐人工林地土壤水分的恢复速度0.90mm/d,油松人工林地为0.53 mm/d、次生林地为0.79 mm/d.土壤水分剧烈变化期(5-10月)刺槐人工林地土壤水分含量的极差为95.71mm,油松人工林地为179.1mm,次生林地为72.03mm.在干旱少雨的黄土高原进行植被恢复时,应多采取封山育林等方式,依靠自然力量形成能够与当地土壤水资源相协调的次生林,是防止人工植被过度耗水形成“干化层”、保障水土保持植被持续发挥生态服务功能的关键.%Soil moisture was the limiting factor for vegetation rehabilitation on the Loess Plateau in China. Understanding the relationship between vegetation and soil moisture was important to soil and water conservation. During the period of July 1, 2008 and October 31, 2009, we measured soil moisture dynamics of Robinia pseudoacacia plantations, Pinus tabulaeformis plantation and the secondary forests every 30 minutes on the Loess Plateau in western ShanXi Province

  19. 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.

  20. Impact of Biological Soil Crust on Soil Physical Properties in the Hilly Loess Plateau Region,China%黄土丘陵区生物结皮对土壤物理属性的影响

    Institute of Scientific and Technical Information of China (English)

    高丽倩; 赵允格; 秦宁强; 张国秀; 杨凯

    2012-01-01

    Biological soil crusts(biocrusts) are ubiquitous living surface covers in many arid and semi-arid regions.It has been demonstrated that the coverage of biocrusts was over 70% in the hilly Loess Plateau region of China and it played many important roles,such as exerting observably impact on soil properties and improving soil antierodibility.But the response of soil physical properties to the development of biocrusts has been unclear so far.The objective of the study was to determine the impact of development of biocrusts(i.e.with variable biomass) on soil physical properties in hilly Loess Plateau region.In this study,soil samples were collected after biocrusts and vegetation coverage survey,and the soil physical properties including soil bulk density,soil porosity,field water holding capacity,cohesion and hardness of biocrusts in different developmental stages were determined.The results showed: 1) Fine particles content increased due to the development of biocrusts.The content of coarse sand decreased by 86% while fine sand increased by 45% with biocrusts developing from cyanobacteria dominated to moss dominated(biomass of moss was 4.31±0.12 g/dm^2).2) With the development of biocrusts,soil bulk density and hardness were reduced while field water holding capacity,soil porosity and cohesion were increased significantly.Along with the development of biocrusts,soil bulk density was dropped by 15%.Soil hardness of biocrusts in later development stage was reduced by 68% compared with the early stage.Field water holding capacity was increased to 57%,adding about 36% compared with the early stage,while soil porosity gone up to 58%,increasing by about 14%.Cohesion of biocrusts was 6 or 7 times as much as that of subsurface soil(0-2 cm).3) Impact of biocrusts on soil physical properties was closely related to biocrusts'biomass.When biomass of moss in biocrusts was to 2.91±0.12 g/dm^2,soil physical properties changed no longer significantly.4

  1. 黄土高原小流域不同地形下土壤有机碳分布特征%The distribution of soil organic carbon as affected by landforms in a small watershed of gully region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李林海; 郜二虎; 梦梦; 魏孝荣

    2013-01-01

    研究了黄土高原小流域尺度塬面、坡地、沟道和梯田4种地形条件下土壤有机碳总量和活性组分的分布、储量及碳库管理指数的差异.结果表明,小流域土壤有机碳和不同活性有机碳的变异系数介于32%-70%之间,表现出中到高度的变异特征.4种地形下各组分有机碳含量和储量以塬面土壤最高,沟道土壤最低,并随土层深度的增加而降低,降低程度随有机碳活性增强而增加.以塬面土壤为对照所获得的碳库管理指数可灵敏指示有机碳对地形条件的响应特征,中活性有机碳库管理指数的指示效果最好.研究结果可部分解释黄土高原土壤有机碳地带性分布特征.%Soil organic carbon plays important role in soil quality changes and terrestrial carbon cycling. However, the relationships between soil organic carbon distribution and landscape positions were not well understood, which are essential for the precisely predication of the spatial distribution of soil organic carbon and for the rational management of soil organic carbon, as well as for the assessment of the dynamics of soil organic carbon at different landscape positions at different landscape scales. China's Loess Plateau is a major region for agricultural production, and an ecological ecotone in northwest China, which suffers serious land degradation and ecologically economic problems due to the soil erosion in the region. The distribution and cycling of soil organic carbon were related not only with the maintaining and improving of soil quality in the region, but also with the response and adaptation of soil ecosystems to the future global climate change, and thus should be carefully assessed. In this study, we investigated the distribution of soil organic carbon and labile organic carbon at various landforms, that is, plateau land, sloping land, gully bottom and terrace land. We also anlyzed the differences of carbon management index at various landscape

  2. 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.

  3. 黄土高原吕二沟流域不同植被下的坡面径流特征%Characteristics of Slope Runoff under Different Vegetation Conditions in Lvergou Watershed of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    varied because of its different vegetation, soil conditions and roots, etc. Under the same rainfall conditions, the runoff of four plots with different vegetation types showed shrub> mixed> locust> pine. The same law was also exhibited in surface runoff with the performance of shrubs> locust> pine> mixed. While subsurface flow was different from the both above with the performance of mixed > pine> shrub> locust. The main form of slope runoff of locust and shrub runoff plots was surface runoff, which accounted for 95.61% and 91.62% of the total runoff respectively. The main form of slope runoff of mixed runoff plots was subsurface flow, which accounted for 90.86%. The surface runoff and subsurface flow of slope runoff of pine runoff plots accounted for 61.99% and 38.01% respectively. Precipitation, especially for the Loess Plateau which seasonally rains obviously, is the main source of runoff. When the rainfall reaches a certain threshold, runoff process will be produced. The effects of rainfall intensity on surface runoff and subsurface flow were different. Antecedent soil moisture was a very important factor which affected slope producing flow.

  4. 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

  5. 历史时期黄土高原生态环境建设分析%Analysis on Eco-environment Construction in Human Period on Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    王飞; 李锐; 谢永生

    2001-01-01

    -environment construction, especially in water engineering, soil improvement and soil and water conservation, was so outstanding that many of them are important today. The experiences in history can be used to accelerate the step of environment harness. Under the historic current chance of development in west area of China, the scientific views and ways on development should be considerated carefully to make Loess Plateau beauty as soon as possible.

  6. 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

  7. Stationarity and Change Trend of Streamflows in Forest and Less Forested Watersheds on Loess Plateau%黄土高原森林/非森林流域径流稳定性及其演变趋势对比

    Institute of Scientific and Technical Information of China (English)

    谢名礼; 张晓萍; 刘二佳; 陈妮; 张亭亭; 郭敏杰

    2013-01-01

    The stationarity of streamflows over the past 50 years were investigated for well/poorly forested watersheds in the Beiluohe River basin on the Loess Plateau,using concentration degree and concentration period methods.The change trend and change point were checked with nonparametric M-K,Pettitt and Rank-sum tests.Results show that all the five watersheds studied were characterized by the high fluctuation of annual streamflow and the double peaks of inner-annual hydrograph.Forested ones presented mild slopes and less forested ones,steep shapes.In contrast,the streamflows were better distributed in well forested watersheds where the concentration period was 1 month behind the poorly forested counterpart.Different components of the streamflow in forested watersheds did not show a significant trend or change point,while significant decrease and change points were detected in annual streamflow and the components in summer,fall and flood season for less forested watersheds in the past 50 years.In both annual and inner-annual scales,the streamflow in forested watersheds was considered more stable than that of the less forested,which implies that less forested watersheds still demands a long-term construction and conservation for the eco-environment to recover.%采用集中期、集中度等方法及M-K,Pettitt等非参检验法对比分析了黄土高原北洛河子午岭森林流域与相邻丘陵沟壑区非森林流域近50 a来的径流稳定性差异及演变趋势,为黄土高原地区生态治理的水文效应分析提供参考和借鉴.结果表明,黄土高原子午岭林区和非林区流域径流量年际尺度分布表现出一致的强变异性,年内分布均为双峰型特征,但林区峰型平缓,非林区陡峭.林区流域年内分布较非林区流域均匀,前者径流集中期较后者滞后1个月.近50 a来林区流域径流量无明显变化趋势,而非林区流域年、夏、秋及汛期径流量表现出显著性减少趋势,且有显著的跃

  8. 陕北黄土高原刺槐植物功能性状与气象因子的关系%Relationships between Plant Functional Traits of Robinia Pseudoacacia and Meteorological Factors in Loess Plateau, North Shaanxi, China

    Institute of Scientific and Technical Information of China (English)

    宋光; 温仲明; 郑颖; 丁曼

    2013-01-01

    To elucidate the variation in plant functional traits and adaptive strategies of Robinia Pseudoacacia on the Loess Plateau,we measured 10 plant functional traits of Robinia Pseudoacacia in 14 counties along the middle area to the north of Shaanxi province,and analyzed the relationships among these functional traits along environmental gradients.The results showed that leaf nitrogen content (LNC) and root nitrogen content (RNC) have no significant differences among 14 sampling points,while other 8 plant functional traits showed significant differences among sampling points (P < 0.05).Specific leaf area (SLA),leaf thickness (LT),leaf tissue density (LTD) and specific root length (SRL) have significant negative correlations,and root tissue density(RTD) and specific root length(SRL) has the remarkable negative correlation.Different enviromental factors had different impact on plant functional traits.It showed that mean annual precipitation has the greatest impact on plant functional traits of Robinia pseudoacacia,and followed by mean annual temperature and annual sunlight ratio according to the stepwise regression analysis.%为阐明刺槐植物功能性状在黄土高原不同环境下的变异规律,探明刺槐对黄土高原环境的适应策略,对陕西省境内从中部向北的14个县(市、区)的刺槐植物功能性状进行测定与统计分析.研究了不同生境刺槐植物功能性状的种内差异、刺槐功能性状间的相关关系及气象因子对刺槐植物功能性状的影响.结果表明:(1)除叶氮含量(LNC)、根组织密度(RTD)和根氮含量(RNC)在各采样点之间的差异不显著之外,其他8个性状在各采样点之间均表现出显著的差异(P<0.05).(2)刺槐植物功能性状相互之间都有一定的相关关系,比叶面积(SLA)与叶厚度(LT)、叶组织密度(LTD)和比根长(SRL)呈极显著负相关关系,根磷含量(RPC)与叶磷含量(LPC)和比根长(SRL)呈显著正相关关系,根组织密度(RTD)

  9. 黄土丘陵区生物结皮对土壤可蚀性的影响%Effects of biological soil crust on soil erodibility in Hilly Loess Plateau Region of Northwest China

    Institute of Scientific and Technical Information of China (English)

    高丽倩; 赵允格; 秦宁强; 张国秀

    2013-01-01

    在采样分析生物结皮对土壤理化属性影响的基础上,采用EPIC模型估算与模拟降雨试验相结合的方法,研究了黄土丘陵区不同生物量、不同土壤质地和不同季节的生物结皮对土壤可蚀性(K值)的影响.结果表明:生物结皮显著降低了土壤可蚀性,生物结皮层土壤可蚀性较下层土壤降低17%;土壤可蚀性随生物结皮生物量的增加呈降低趋势,藓结皮土壤可蚀性K值较藻结皮土壤降低21%;生物结皮土壤可蚀性在不同季节因其生物活性不同而存在差异,雨季中显著高于雨季前和雨季末;不同质地土壤上生物结皮对可蚀性的影响不同,可蚀性K值为砂壤>粉壤>砂土;模拟降雨条件下测定表明,生物结皮的发育使土壤可蚀性较对照(下层5~10 cm土壤)降低约90%.%Based on the analysis of the effects of biological soil crust (biocrust) in re-vegetated grasslands on soil physical and chemical properties, and by using EPIC estimation model in combi-ning with simulated rainfall trials, this paper studied the effects of biocrust with different biomass and different soil texture on the soil credibility (K value) in Hilly Loess Plateau Region of North-west China in different seasons. The results showed biocrust could significantly decrease soil erod-ibility, with the K value of biocrust soil decreased by about 17% , compared with subsoil. The soil erodibility decreased with the increasing biomass of biocrust. The K value of moss crust soil de-creased by 21% , compared with cyanobacteria crust soil. The erodibiliy of biocrust soil differed with different seasons, being significantly higher in rainy season than before or after the rainy season due to the differences in the biological activity of the biocrust organisms. The erodibilty of biocrust soil with different texture also varied significantly, with the K value in the order of sandy loam soil > silt soil > sandy soil. The measurement under simulated

  10. Spatial-temporal change and its driving forces of woodlands in the gully area of Longdong loess plateau over the last 30 years%近30年陇东黄土高原沟壑区林地时空变化及其驱动力分析

    Institute of Scientific and Technical Information of China (English)

    董晓峰; 马如兰; 庞国锦; 李波; 宋翔

    2011-01-01

    通过使用ERDAS和GIS分析工具对陇东地区1978年、1990年、2000年和2007年4期遥感影像进行人工目视解译,得出近30年来陇东黄土高原沟壑区林地的动态变化信息.结果表明,近30年陇东黄土高原沟壑区林地面积总体上呈增加趋势,表现为1978-1990年林地面积减少,1990-2000年林地面积增加,2000-2007年林地面积大幅增加.对林地变化的驱动力分析表明,人类活动是影响林地变化的主要因素;此外,气候变化、虫害等因素对林地时空变化也产生了影响.%Based on four remote sensing images(MSS in 1978 and TM in 1990, ETM+ in 2000 and TM in 2006), the spatial-temporal changes of woodlands inthe Longdong loess plateau area are analyzed with the support of ERDAS and GIS.Over the past 30 years the total area of the woodlands increased, during 1978 to 1990, patchy forest decreased heavily, during 1990 to 2000, patchy forest increased, from 2000 to 2007, forest land was rising substantially.The process responsible for woodlands change in the Longdong loess plateau area could be divided into natural and anthropogenic groups by analyzing the transition matrices.Human activities have been an important factor, at the same time climate change and insect damage also play important roles.

  11. 黄土高原中部秋季干湿的年际和年代际环流异常特征及与海温的多尺度相关性研究%Interannual and interdecadal atmospheric circulation anomalies of autumn dry/wet over the loess plateau and its multi-scalar correlation to SST

    Institute of Scientific and Technical Information of China (English)

    刘晓云; 王劲松; 李栋梁; 岳平; 李耀辉; 姚玉璧

    2013-01-01

    The ecological environment is vulnerable and extremely sensitive to climate change in the loess plateau. The interannual and interdecadal variations of dry/wet index are particularly obvious in this region. Up to now, the analisis of the dry/wet variation in the loess plateau has been basically understood during summer, but the autumn dry/wet evolution of the loess plateau and the atmospheric circulation characteristic are still laking in its knowledge. Based on the monthly mean rainfall and temperature of 589 China weather stations, the NCEP/NCAR reanalysis dataset and NOAA extended reconstructed sea surface temperature (SST) data from 1961 to 2010, using the EOF/REOF, bandpass filtering, wavelet technique and regression methods, the autumn dry/wet evolution of the loess plateau and the atmospheric circulation characteristic associated with them, and the multi-scale relationship between dry/wet index and SST were analyzed on the basis of classification of dry/wet over China region in autumn. The continuous wavelet transform shows that the autumn wet/dry index exists has∼4 a and 8 a period over the loess plateau, and the∼8 year oscillation from 1970-1990 is rather obvious. On the interannual scales, the atmospheric circulation anomalies of 500 hPa associated with the wet years exhibit a‘double-blocking’ in the mid-high latitude, and the westerly jet stream turns to be weakened and the jet axis moves to the north significantly. Japan-Okhotsk Sea is featured with anticyclone, and the east wind at the bottom of the anticyclone provides favorable moisture for the middle Loess plateau. On the interdecadal scales, the atmospheric circulation anomalies associated with the wet years show the negative geopotential height anomaly over East Asian, and the East Asian subtropical westerly jet stream of 200 hPa is weakened and moves north too. The vapour of the middle Loess plateau comes from two paths, one is the westerly water vapor transport in the middle latitude

  12. Lithium distribution and isotopic fractionation during chemical weathering and soil formation in a loess profile

    Science.gov (United States)

    Tsai, Pei-Hsuan; You, Chen-Feng; Huang, Kuo-Fang; Chung, Chuan-Hisung; Sun, You-Bin

    2014-06-01

    Lithium (Li) is a fluid-mobile element and δ7Li in secondary deposits represents an excellent proxy for silicate weathering and authigenic mineral formation. The soil samples from 1205 to 1295 cm in the Weinan profile, one of the best developed loess-paleosol sequences covering the last glacial-interglacial climatic cycle, were collected and chemically separated into detritus and carbonate fractions for subsequent analyses of Li, δ7Li, major and trace elements. Other desert specimens (i.e., Qaidam Desert, Tengger Desert, Badain Juran Desert and Taklimakan Desert) near the Chinese Loess Plateau (CLP) and various standard clays were analyzed for assisting provenance determination. The Li and δ7Li distributions in the detritus are rather homogeneous, 1.4-2.0 μg/g and +2.5‰ to +4.7‰, respectively, compared with the carbonate fraction. The detrital δ7Li varies systematically with magnetic susceptibility and grain size changes, reflecting significant Li isotopic variation associated with sources and mineralogy of detrital material. On the other hand, Li and δ7Li in carbonates show large changes, 781-963 ng/g and -4.1‰ to +10.2‰, respectively. These carbonate δ7Li correlated well with the estimated index of chemical weathering, as a result of Li mobilization and soil formation during chemical weathering.

  13. Physical mechanisms of plant roots affecting weathering and leaching of loess soil

    Institute of Scientific and Technical Information of China (English)

    LI; Yong; ZHANG; Qingwen; WAN; Guojiang; HUANG; Ronggui; PIAO; Hechun; BAI; Lingyu; LI; Lu

    2006-01-01

    Plant roots have potential impacts on soil mineral weathering and leaching. Our objective is to understand the physical mechanisms of plant roots affecting weathering and leaching of loess soil. Root densities were measured through the method of a large-size dug profile, and transport fluxes of soil elements were determined using an undisturbed monolith soil infiltration device on the hilly and gully regions of the Chinese Loess Plateau. The results show that the improvement effects of soil environment by plant roots are mainly controlled by the density and weight of the fibrous roots with the diameters less than 1 mm. Plant roots have the stronger effects on soil physical properties than chemical properties. The principal components analysis (PCA) indicates that soil physical properties by plant roots account for 56.7% of variations in soil environment whereas soil chemical properties and pH contribute about 24.2% of the soil variations. The roles of plant roots in controlling soil weathering and leaching increased in the following order: infiltration enhancement > increase of bioactive substance > stabilization of soil structure. The effects of plant roots on soil mineral weathering and leaching can be quantified using the multiple regression models with the high prediction accuracies developed in this study.

  14. Geochemical study of boron isotopes in the process of loess weathering

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Zhiqi; (

    2003-01-01

    ., Atmospheric carbon dioxide concentrations over the past 60 million years, Nature, 2000, 406: 695-699.[25]Liu Tungsheng, Loess and Environment (in Chinese), Beijing: Science Press, 1985, 191-302.[26]Gu Zhaoyan, Lal, D., Guo Zhengtang et al., 10Be geochemical characteristics of loess and redclay on the Loess Plateau, Quaternary Research (in Chinese), 2000, 20(5): 409-423.[27]Liu Tungsheng, Loess and Environment (in Chinese), Bejing: Science Pres, 1985, 1-481.[28]Zhao Zhiqi, Liu Congqiang, Xiao Yinkai, Separation of boron in acid-soluble phases in loess and paleosol deposits and its isotopic determination, Geochimica (in Chinese), 2000, 29(4): 351-357.[29]Xiao, Y. K., Beary, E. S., Fassett, J. D., An improved method for the high-precision isotopic measurement of boron by thermal ionization masses spectrometry, Int'l. J. Mass Spect. and Ion Proc., 1988, 85: 203-213.[30]Spivack, A. J., Edmond, J. M., Determination of boron isotope ratios by thermal ionization mass spectrometry of the dicesium metaborate cation, Anal. Chem., 1986, 58: 31-35.[31]Kiss, E., Ion-exchange separation and spectrophotometric determination of boron in geological materials, Anal. Chem. Acta, 1988, 211: 243-256.[32]Liu Tungsheng, Loess and Environment (in Chinese), Beijing: Science Press, 1985, 44-106.[33]Liu Congqiang, Zhao Zhiqi, Xiao Yinkai, Boron isotopic composition of loess and its implication for climatic tracing, Quaternary Research (in Chinese), 2000, 20(4): 394.[34]Taylor, S. R., Mclennan, S. M., Mcculloch, M. T., Geochemistry of loess, continental crustal composition and crustal model age, Geochim. Cosmochim. Acta, 1983, 47: 1897-1905.[35]Liu, C. Q., Masuda, A., Okada, A. et al., A geochemical study of loess and desert sand in northern China: Implications for continental crust weathering and composition, Chemical Geology, 1996, 106: 359-374.[36]Ishikawa, T., Nakamura, E., Boron isotope systematics of marine sediment, Earth Planet Sci. Lett., 1993, 117

  15. Charge analysis on lightning discharges to the ground in Chinese inland plateau (close to Tibet

    Directory of Open Access Journals (Sweden)

    X. Qie

    Full Text Available Since the summer of 1996, scientists from China and Japan have conducted a joint observation of natural cloud-to-ground lightning discharges in the Zhongchuan area that is located close to Qinghai-Xizang (Tibet Plateau, China. It has been found that the long-duration of intracloud discharge processes, just before the first return stroke, lasted more than 120 ms for 85% of cloud-to-ground flashes in this area, with a mean duration of 189.7 ms and a maximum of 300 ms. We present the results of charge sources neutralized by four ground flashes and two intracloud discharge processes, just before the first return stroke, by using the data from a 5-site slow antenna network synchronized by GPS with 1 µs time resolution. The result shows that the altitudes of the neutralized negative charge for three negative ground flashes were between 2.7 to 5.4 km above the ground, while that of neutralized positive charges for one positive ground flash and one continuing current process were at about 2.0 km above the ground. The comparison with radar echo showed that the negative discharges initiated in the region greater than 20 dBZ or near the edge of the region with intense echoes greater than 40 dBZ, while positive discharge initiated in the weak echo region.

    Key words: Meterology and atmospheric dynamics (atmospheric electricity; convective processes; lightning

     

  16. Can the magnetic susceptibility record of Chinese Red Clay sequence be used for palaeomonsoon reconstructions?

    Science.gov (United States)

    Zhao, Guoyong; Han, Yan; Liu, Xiuming; Chang, Liao; Lü, Bin; Chen, Qu; Guo, Xuelian; Yan, Junhui; Yan, Jun

    2016-03-01

    Red Clay underlying the loess-palaeosol sequences on the Chinese Loess Plateau is an eolian deposit. There is a controversy over whether magnetic susceptibility (χ) variations in Red Clay sequence can be used as an indicator of summer palaeomonsoon intensity. This study investigates the magnetic mineralogy, magnetic concentration and magnetic grain size distribution of Jiaxian Red Clay with multimagnetic methods. Our results indicate that the magnetic properties of Jiaxian Red Clay are similar to those of the Quaternary loess-palaeosol sequences, and ultrafine ferrimagnetic grains produced during pedogenesis are responsible for an increase in susceptibility, therefore the χ enhancement mechanism of Red Clay is similar to that of the overlying loess-palaeosol sequences. This paper explores χ variations in the Red Clay sequence through spatial and temporal analysis. The susceptibility variation of six sites along a NNE to SSW transect correlate to palaeoclimatic cycles, so χ can be used to trace the summer palaeomonsoon intensity from a spatial perspective. However, a simple loess-derived calibration function cannot be used to quantitative reconstruct the palaeomonsoon intensity variations thought time. An adjusted calibration function for palaeosols from Red Clay sequence needs to be developed, so that χ can be used to quantitative reconstruct palaeomonsoon intensity. Further study is necessary to develop such a transfer function.

  17. Comparative Study on Growth Process of Main Introduced Tree Species in the Middle Loess Plateau%黄土高原中部主要引进树种生长过程分析

    Institute of Scientific and Technical Information of China (English)

    刘广全; 孙克; 何正祥; 王鸿喆

    2012-01-01

    The introduced 16 species Austrian black pine,ponderosa pine,pinyon,scotch pine,Austrian pine and so on in the middle part of the Loess Plateau,the process of the average individual height growth can be grouped into two categories,the first type represented by Austrian pine,it grows rapidly in the period of seedlings,along with the ages its growth slows down and gradually stabilizes.The other type follows the growth pattern of "show-rapid-slow-stably drop down".Its average annual growth in height is 0.369±0.097m,Ponderosa pine and Austrian pine are the highest(0.535±0.052m),and china hemlock is the lowest(0.251±0.044m).The mean current annual growth in height of the 6 species is 0.387±0.104 m,the black pine is the maximum,the huashan pine is the minimum,the former is 2.63 times of the later.The variation of the average annual growth at breast height of the above-mentioned sixteen species is not appreciable,the highest of the ponderosa pine is 1.595±0.192 cm,the lowest is Wilson spruce with variation of 0.363±0.088cm.The average annual growth at breast height of the native tree species as bunge pine,huashan pine,golden larch,Wilson spruce,china hemlock and mogol scotch pine is 0.6048 cm,compared with the introduced tree species with 0.8488cm,which growth surpass the native tree species.Among the 16 introduced tree species with the mean current annual growth of 0.7056±0.2590 cm,the ponderosa pine is the maximum(1.249±0.350cm),and Wilson spruce is the minimum(0.376±0.241cm),the introduced tree species surpass the native tree species more than 50.0%.%本文对黄土高原中部引进的奥地利黑松、美国黄松、美人松、欧洲赤松、欧洲黑松等16个树种,林分个体树高平均生长量曲线分两种类型,以欧洲黑松为代表的第一种类型,苗期生长较快,随着年龄的增加,树高平均生长量趋于减慢且逐渐稳定,另外一种类型满足正常的"慢—快—缓慢—稳中有降"的生长规

  18. 黄土区次生植被恢复对土壤有机碳官能团的影响%Effect of revegetation on functional groups of soil organic carbon on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    李婷; 赵世伟; 张扬; 马帅; 李晓晓

    2011-01-01

    Vegetation succession affects soil physical and chemical properties, including organic carbon functional group species, quantities, and structural changes. Changes in soil organic carbon (SOC) functional groups during the vegetation restoration process could reveal the processes governing changes in the composition and properties of humus. The study was on the Loess Plateau in the Ziwuling forest region of Shaanxi Province, where various stages of secondary forests have developed. At different phases of development, vegetation systems in this region have changed from pioneer herbage species, which initially colonized abandoned croplands, (Bothriochloa isehemum, Artenmisia giradii, Stipa bungeana, Artenmisia sacrornai, Spodiopogen sibiricus, Sophora flavecens,Themeda japonica, and Arundinella anomala) , to secondarv shrubs (Hippophae rhamnoides, Sophora viciifdia, and Ostrjopsis davidiana) , to an early forest community ( Populus davidiana, Betula platyphylla, and Platycladus orientalis with groups of trees and/or shrubs) , and finally to a Liaotungesis community forming the mature forest. The SOC content in the 0-40 cm soil layer increases significantly during the vegetation succession from abandoned cropland to mature Liaotungesis forest. The rate of increase in SOC is different during vegetation succession, and organic carbon functional groups varied among the different plant communities. Recent studies using synchrotron-based C( 1s) near-edge X-ray absorption fine structure (NEXAFS) have shown it to be an effective, non-invasive technique, which can be used to identify and fingerprint the complex structural characteristics of SOC. Consequently it can be used to investigate the impact of management on the composition and biogeochemical cycling of organic C at the molecular level in terrestrial ecosystems. This synchrotron radiation technology has rarely been used to study SOC structure in China before so we used it in this study with the objective of developing a

  19. Loess in China: A Good Archive of Climatic and Environmental Changes during the Quaternary

    Institute of Scientific and Technical Information of China (English)

    Wang Limeng; Lu Huayu

    2005-01-01

    @@ Quaternary scientists in China have significantly improved our knowledge of loess deposition as well as our understanding of paleoclimatic and paleoenvironmental changes over the past 2.5 million years. It is recognized that loess is of aeolian origin with loess forming dust continuously deposited. It is also believed that grain-size, magnetic susceptibility, carbon isotopes and fossil assemblages in loess deposits are good proxy indicators of paleomonsoon climate and paleovegetation changes over the past 2.5 million years. Chinese loess is regarded as one of the best terrestrial archives of climatic and environmental changes during the Quaternary.Further investigation of loess deposits and their records of climatic and environmental change aids understanding of climate change and gives scientific backing for the project of ecological and environmental restoration in northwest China.

  20. Removal of radiation damage by subpopulations of plateau-phase Chinese hamster ovary cells

    International Nuclear Information System (INIS)

    Specific cellular radiobiology studies are often required to test aspects of the mathematical models developed in the Radiation Dosimetry program. These studies are designed to determine whether specific mathematical expressions, which characterize the expected effect of biochemical mechanisms on observable biological responses, are consistent with the behavior of selected cell lines. Since these tests place stringent requirements on the cellular system, special techniques and culture conditions are required to minimize biological variability. The use of specialized cell populations is providing data on the extent of repair following low doses, and on the changes in the types of damage that can be repaired as the cell progresses toward mitosis. The stationary-phase Chinese hamster ovary (CHO) cells are composed primarily of G(1)-phase cells (83%), with the remainder comprising both G(2) and S phases. Removal of radiation damage by cells was studied in split-dose experiments. To date, we have observed no significant differences in cellular repair rate. This suggests, therefore, that each of the repair processes found in stationary-phase cells is cell-age independent. However, cellular radiation sensitivity does change rapidly and considerably as the cells progress from one phase to the next through the cell cycle. Since the rate of damage removal appears invariant, the change in survival must reflect the efficiency of producing that damage. The experimental data suggest that production of one or another sort of damage probably dominates during specific phases of the cell cycle, while the capacity for removal of all types of damage remains relatively constant

  1. 陇中黄土高原自然植被下垫面陆面过程及其参数对降水波动的气候响应%Responses of the land-surface process and its parameters over the natural vegetation underlying surface of the middle of Gansu in loess plateau to precipitation fluctuation

    Institute of Scientific and Technical Information of China (English)

    张强; 李宏宇; 张立阳; 岳平; 史晋森

    2013-01-01

    作为气候敏感区和生态脆弱区,黄土高原地区的陆面物理过程受气候波动影响十分明显.目前,虽然对黄土高原特定气候条件下的陆面物理过程有了一定认识,但对其随气候波动的动态变化规律认识却非常有限.本文利用黄土高原陆面过程观测试验在陇中黄土高原榆中SACOL站5年多的观测资料,系统分析了该地区自然植被下垫面陆面水分收支和能量平衡及地表反照率、土壤热传导率和粗糙度长度等陆面过程参数对气候波动的响应规律,发现陇中黄土高原自然植被下垫面的陆面过程特征及其参数对降水的气候波动十分敏感,不仅对降水量波动响应显著,而且与降水性质也密切相关.土壤湿度并不完全随年总降水量波动,而是随有效降水量增加而增大;陆面水分收支和土壤水分收支也随有效降水量波动变化明显;近地层垂直感热平流通量随年总降水量增加而减弱,地表能量不平衡差额却随年总降水量增加而增大.夏半年平均反照率随有效降水量增加而减小,但全年平均地表反照率却受冬季积雪时数影响十分明显,而且随积雪时数增加而增大;土壤热传导率和粗糙度长度均随年有效降水量增加而增加.并且,降水量越小,陆面过程参数对降水波动的响应就越敏感.不过,陆面过程参数基本在荒漠气候平均值和农田气候平均值之间波动,并没有突破气候约束,能够用拟合关系来表示它们对降水因子波动的响应规律,这种动态参数化关系可用来改善以往数值模拟或微气象分析时由于使用非动态陆面过程参数所带来的误差.%The Loess Plateau is well known as a specific region sensitive to global climate change, and thus its land-surface process is significantly influenced by climatic fluctuation. Up to now, the land-surface physical process over the Loess Plateau has been basically understood under a

  2. 黄土高原土壤剖面粒度异常层及相关因素的响应初步分析%Preliminary Analysis on Abnormal Granularity Layers of Soil Profile and the Response of Relative Factors in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    吕海波; 梁宗锁

    2011-01-01

    [目的]对黄土高原安塞县纸坊沟流域退耕林土壤1 m剖面有机碳含量、粒度、全氮含量、碳氮比、碳酸钙含量进行分析,研究以粒度反映下的土壤异常层理化性质变化,以及各土壤物理化学的响应.[方法]对黄土高原上3个样地各随机选择3个10 m×10 m的样方并分坡上、坡中、坡下分别挖掘3剖面,间隔10 cm采样,地表0~10 cm分0~5 cm和5~ 10 cm 2部分分别采样.每剖面采样11个,共99个样品,对其进行机碳含量、粒度、全氮含量、碳氮比、碳酸钙含量分析.[结果]3个样地土壤剖面存在a1、b1、b2、c1、c25个特征层,<0.02 mm粒径的土壤颗粒含量减少,>0.02 mm粒径的土壤颗粒含量增加,有机碳含量和C/N值(a1、b1、b2、c2)增加,但CaCO3含量上升趋势不明显.[结论]研究证明土壤特征层在黄土地区,尤其是侵蚀性黄土地区是普遍存在的,在现代土壤学和生态学研究领域应当给予重视.%[Objective]The paper was to analyze organic carbon content (SOC) , granularity, total nitrogen content (TN) , carbon-nitrogen ratio (C/N), calcium carbonate content (CaCO3) of 1cm soil profiles in returning forest in Zhifanggou watershed of Ansai County in Loess Plateau, so as to study the changes of physicochemical characters in abnormal layer of soil reflected with granularity, as well as the physical and chemical responses of soil. [ Method] Three sampling plots with the size of 10 m × 10 m were randomly selected in three sampling sites in Loess Plateau, three profiles in upper, middle and lower slope were excavated, and the samples were collected with interval of 10 cm; the surface layer with the depth of 0 - 10 cm was divided into two layers 0 -5 cm and 5-10 cm for sampling, respectively. 11 samples were collected in each profile with a total of 99 samples. Its organic carbon content, granularity, total nitrogen content, carbon-nitrogen ratio and CaCO3 content were analyzed. [ Result] The soil

  3. 陕北黄土高原乡村旅游资源及其营销策略比较优势%STUDY ON COMPARATIVE ADVANTAGES OF RURAL TOURISM RESOURCES AND MARKETING STRATEGY IN THE LOESS PLATEAU OF NORTHERN SHANXI

    Institute of Scientific and Technical Information of China (English)

    霍佳颖

    2016-01-01

    近年来,随着生活节奏的不断加快,人们休闲娱乐的时间变短,可以享受自然与人文风光的乡村旅游逐渐成为游客首选的旅游形式之一.为了满足游客多样化的需求,如何开发并合理利用乡村旅游资源成为乡村旅游发展的重要问题.陕北黄土高原拥有丰富的乡村旅游资源,其乡村旅游发展具有很大潜力.文章通过梳理乡村旅游的概念、 乡村旅游资源的内涵与分类方式,从自然旅游资源与人文旅游资源等2个方面分析了陕北黄土高原乡村旅游资源现状,总结出该地区的乡村旅游资源拥有资源数量较多、 类型多样,分布较为集中、 利于组合开发等比较优势,提出陕北黄土高原乡村旅游应采取打造陕北黄土高原乡村旅游品牌、 利用科技手段建立先进营销模式及开发个性化的旅游服务营销产品等营销策略,从而推动陕北黄土高原旅游产业的快速发展.%In recent years, with the accelerating pace of life, people's leisure time is short. Rural tourism has grad-ually become one of tourism forms that the tourists preferred,because it can make people enjoy natural and cultural landscape. In order to meet the diverse needs of tourists, how to develop and make use of rural tourism resources becomes an important issue of rural tourism development. The Loess Plateau of Northern Shanxi has rich rural tourism resources and great potential in rural tourism development. Through combing rural tourism concept and con-notation of rural tourism resources and classification, this paper analyzed the current situation in Loess Plateau of Northern Shanxi Province rural tourism resources from two aspects, i. e. , natural tourism resources and cultural tourism resources, summed up the comparative advantages of rural tourism resources which had a large number of resources and diverse types, more concentrateddistribution, and combination development and so on. Finally, it put forward some

  4. Evolution of the Ordos Plateau and environmental effects

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the analysis of temporary-spatial distribution, geomorphic position, contact relationship with underlying strata and grain size of red clay, we studied the formation and environmental background of red clay. During late Miocene-Pliocene, the Ordos Block finished the transformation from the basin to the plateau, which had an obvious environmental effect on the topography, indicated by the formation of highland undergoing wind erosion and lowland receiving red clay deposits. The red clay materials were sourced from dusts carried by wind energy and covered on the initial topography. Unlike Quaternary loess dust covering the overall the Loess Plateau, red clay deposited on the highland would be transported to the lowlands by wind and fluvial process. As a result, there was no continuous "Red Clay Plateau" in the Ordos region and red clay was only preserved in former lowlands. However, red clay was discontinuously distributed through the Loess Plateau and to some extent modified the initial topography. The differential uplift in interior plateau is indicated by the uplift of northern Baiyushan, central Ziwuling and southern Weibeibeishan. The Weibeibeishan Depression formed earlier and became the sedimentary center of red clay resulting in the thicker red clay deposits in Chaona, Lingtai and Xunyi. Since Quaternary the aridity in the northern plateau enhanced and accelerated loess accumulation caused the formation of the Loess Plateau. During the late Pleistocene the rapid uplift led to the enhancement of erosion. Especially after the cut-through of Sanme Lake by the Yellow River, the decline of base level caused the falling of ground water level and at the same time the increase of drainage density resulting in the enhancement of evaporation capacity, which enhanced the aridity tendency of aridity in the Loess Plateau region.

  5. Simulation of the erosion and drainage development of Loess surface based on GIS

    Science.gov (United States)

    Wang, Chun; Tang, Guoan; Ge, Shanshan; Li, Zhanbin; Zhou, Jieyu

    2006-10-01

    The research probes into the temporal-spatial process of drainage development of Loess Plateau on the basis of a carefully designed experiment. In the experiment, the development of a simulated loess watershed is tested under the condition of lab-simulated rainfall. A close-range photogrammetry survey is employed to establish a series of high precision and resolution DEM (Digit Elevation Model) of the simulated loess surface. Based on the established DEM, the erosion loss, the slope distribution, the topographic index , the gully-brink, and the drainage networks are all derived and discussed through comparison analysis and experimental validation. All the efforts aim at revealing the process and mechanism of erosion and drainage development of loess surface .This study demonstrates: 1) the stimulation result can effectively reflect the truth if those experimental conditions, i.e. loess soil structure, simulated rainfall, are adjusted in accord with true situation; 2) the remarkable character of the erosion and drainage up-growth of loess surface include the drainage traced to the source, the increased of the drainage's density, the enlarged of gully, the durative variety of multiple terrain factor's mean value and its distribution, such as slope and topographic index; 3) The slope spectrum is the more felicitous terrain factor for depicting the erosion and drainage development of loess surface, including the rule of erosion and evolution process. It is the new way and mean for studying the loess physiognomy.

  6. Molecular fossil and paleovegetation records of paleosol S4 and adjacent loess layers in the Luochuan loess section, NW China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using gas chromatography-mass spectrometry (GC-MS) technique, a series of biomarkers were identi- fied, including n-alkanes, n-alkane-2-ones, isoprenoid etc. from the loess-paleosol samples collected from the S4 and adjacent L5, L4 of the Luochuan loess section, Northwestern China. Based on these data, especially n-alkanes and high-resolution magnetic susceptibility and grain size data, the pa- leoenvironment and paleovegetation history during S4 was reconstructed. The CPI (Carbon Predomi- nance Index) and correlation between n-alkanes and magnetic susceptibility and grain size data dem- onstrated that the molecular fossils in paleosol and loess layers can reflect the vegetation condition during the loess-paleosol formation, if the allochthonous organic inputs could be excluded reasonably. The ACL (average chain length) index is correlated well with paleomagnetic susceptibility and grain size variations, displaying their good synchrony with warm and humid climate. However, it relatively lagged behind the paleomagnetic susceptibility and the grain size variations when the climate began to deteriorate. During the formation period of paleosol, the n-alkanes was dominated by C31 homologue, indicating that the primary organic input originated from herbs. Our study also demonstrated that the herbs were more flourish than wood plants in Loess Plateau, especially in the Luochuan area during the warm and humid phase, and there was no typical forest vegetation developed in the studied period.

  7. Origin of the Red Earth sequence on the northeastern Tibetan Plateau and its implications for regional aridity since the middle Miocene

    Institute of Scientific and Technical Information of China (English)

    WANG; Xianyan; LU; Huayu; JI; Junfeg; WANG; Xiaoyong; ZHAO; Jingbo; HUANG; Baochun; LI; Zhen

    2006-01-01

    The Red Earth deposit around Xining, northeastern Tibetan Plateau, has been studied in terms of soil micro-structure, grain-size distribution, major- and trace-element chemistry and magnetostratigraphy. Field investigations indicate that the Red Earth sequence consists of 25 visually definable yellow-brown and weakly-developed soils interbedded with reddish strongly-developed soils, and has a similar structure to the aeolian Red Clay deposit on the Chinese Loess Plateau. Grain-size analysis shows that the Red Earth deposit is very fine-grained with a negligible sand fraction (>63μm). Thin-section observations under light microscopy show that the deposit has a clayey texture and the coarse fraction (>10μm) mainly consists of quartz, feldspar and micas. Pyroxene and hornblende were also observed. This mineralogical composition of the coarse fraction is similar to that of the Quaternary loess. In addition, all of the mineral grains are semi angular semi-angular and are generally finer than 63μm. There is a good agreement between the major and minor trace element chemistry of loess-soil units and the Red Earth deposit. The REE distributions of the loess-soil and the Red Earth deposit are similar in shape, with enriched LREE and fairly flat HREE profiles and a clear negative Eu anomaly. The geochemical characteristics of the Red Earth deposit are also identical to those of upper continental crust, thus indicating a wind-blown origin.Magnetostratigraphic investigation shows that onset of the Red Earth deposition predates 11.4 Ma BP (13.6 Ma at a nearby site). The distribution of the reported Miocene aeolian loess at Qin'an of the Loess Plateau is still unknown. Our results indicate that this aeolian deposit had extended to the northeastern Tibetan Plateau by at least the middle Miocene. The similarity of the element geochemistry between the Red Earth deposit and the overlying loess shows that they may have similar sources and dynamic transport system, and may indicate

  8. Multiproxy evidence of Late Pleistocene environmental changes in the loess-paleosol sequence of Bůhzdař (Czech Republic)

    Science.gov (United States)

    Flašarová, Kristýna; Vysloužilová, Barbora; Juřičková, Lucie; Šefrna, Luděk; Verecchia, Eric

    2016-04-01

    Europe. Eiszeitalter und Gegenwart, Quaternary Science Journal, 60 (1) http://doi.org/10.3285/eg.60.1.00 Kaakinen, A., Sonninen, E., & Lunkka, J. P. (2006). Stable isotope record in paleosol carbonates from the Chinese Loess Plateau: Implications for late Neogene paleoclimate and paleovegetation. Palaeogeography, Palaeoclimatology, Palaeoecology, 237 (2-4), 359-369. http://doi.org/10.1016/j.palaeo.2005.12.011 Ložek, V. (1952) Zpráva o paleontologickém výzkumu cihelny v Zájezdu u Buštěhradu. Anthropozoikum, III, 135-138. Obreht, I., Buggle, B., Catto, N., Markovič, S. B., Bösel, S., Vandenberghe, D. A. G., … Jović, G. (2014). The Late Pleistocene Belotinac section (southern Serbia) at the southern limit of the European loess belt: Environmental and climate reconstruction using grain size and stable C and N isotopes. Quaternary International, 334-335, 10-19. http://doi.org/10.1016/j.quaint.2013.05.037

  9. Mangshan loess on China’s Central Plain and its response to tectonic movement and climate

    Institute of Scientific and Technical Information of China (English)

    吴锡浩; 蒋复初; 肖华国; 薛滨; 孙东怀

    1999-01-01

    The Mangshan loess on China’s Central Plain, located on the transitional zone between the uplifting Loess Plateau and the subsiding North China Plain, is a proximal sandy loess transported from the fanhead of alluvial fan in the lower reaches of the Yellow River and has recorded the eoupting effect of the tectonics and climate over the last 200 ka. An abrupt environmental change indicated by the abrupt rise of deposit rate in the late penultimate glaciation, about 150 ka BP, took place; that is, the Yellow River downcut and moved eastwards through the Sanmenxia Gorge and transported abundant materials from the Loess Plateau to form paleosol S1 with a thickness of 15.7 m and loess L1 with a thickness of 77.3 m. The loess-paleosol sequence at Mangshan has not only recorded detailed climate responses of this area to the East Asian monsoon, but also refleets the tectonogenetie environmental effect caused by the trunk stream of the Yellow River cutting through Sanmenxia Gorge into sea.

  10. 植被覆盖度和综合治理对纸坊沟流域土壤氮素流失的影响%Effects of Vegetation Coverage and Management Practice on Soil Nitrogen Loss by Erosion in a Hilly Region of the Loess Plateau in China

    Institute of Scientific and Technical Information of China (English)

    张兴昌; 邵明安

    2003-01-01

    同小流域土壤侵蚀一样,小流域土壤氮素随洪流流失也受到植被覆盖度的影响,通常经过调整小流域内土地利用结构以达到控制水土流失.该研究以8.27 km2纸坊沟流域和1:400比例流域模型为研究对象,研究植被覆盖度和综合治理对纸坊沟流域土壤氮素流失的影响.结果表明:在模拟降雨下,当流域植被覆盖度分别为60%、40%、20%和0时,流域模型铵态氮流失量分别为87.08、44.31、25.16和13.71 kg/km2,硝态氮为85.50、74.05、63.95和56.23 kg/km2,全氮为0.81、1.18、1.98和7.51 t/km2;在自然降雨下,1998年与1992年相比,全流域年土壤侵蚀量为1 086 t/km2和1 119 t/km2,氮素流失量为8 758.5和7 562.2 kg,减少了15.8%,其中农地减少了52.0%.流域对降水中的矿质氮具有过滤作用,硝态氮的过滤作用明显高于铵态氮.洪流泥沙中<20 μm微团聚体富集造成了泥沙有机质和全氮的富集.植被覆盖虽能有效地减少流域土壤侵蚀和全氮的流失,却能增加土壤矿质氮的流失.坡地退耕还林草可显著减少流域土壤氮素流失.%Soil erosion and nutrient loss due to erosion are world-wide problems. Similar to soil loss byerosion, soil nitrogen (N) loss by erosion in small catchments is affected by vegetation coverage. Thepractice of comprehensive management for catchments mainly by adjusting cropland, grassland and wood-land areas was widely adopted to reduce soil and water loss in catchments of the Chinese Loess Plateau.Three experiments under natural and artificial rainfall conditions on N loss by erosion for a model catch-ment and for an actual catchment in Zhifanggou of Ansai County in China was performed to determine therelationships between comprehensive management and N loss by runoff in small catchments. The resultsfor vegetation coverage of 60%, 40%, 20% and 0 show that runoff loss of ammonium, nitrate, and total Nwere 87.08, 44.31, 25.16, 13.71 kg/km2; 85.50 74.06, 63.95, 56.23 kg

  11. 黄土高原土壤剖面粒度异常层及相关因素的响应初步分析%Preliminary Analysis on Abnormal Granularity Layers of Soil Profile and the Response of Relative Factors in Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    吕海波; 梁宗锁

    2011-01-01

    [Objective] The paper was to analyze organic carbon content (SOC), granularity, total nitrogen content (TN), carbon-nitrogen ratio (C/N), calcium carbonate content (CaCO3) of 1cm soil profiles in returning forest in Zhifanggou watershed of Ansai County in Loess Plateau, so as to study the changes of physical and chemical properties in abnormal layer of soil reflected with granularity, as well as the physical and chemical responses of soil. [Method] Three quadrats with the size of 10 m×10 m were randomly selected in three sampling plots in Loess Plateau, three profiles in upper, middle and lower slope were excavated, and the samples were collected with interval of 10 cm; the surface layer with the depth of 0-10 cm was divided into two layers of 0-5 and 5-10 cm for sampling, respectively. Eleven samples were collected in each profile with a total of 99 samples. Its organic carbon content, granularity, total nitrogen content, carbon-nitrogen ratio and CaCO3 content were analyzed. [Result] The soil profiles in three sampling sites contained five characteristic layers, including a1, b1, b2, c1 and c2, the content of soil granule with particle size less than 0.02 mm decreased, and those with particle size 0.02 mm increased, the organic carbon content and C/N value (a1, b1, b2, c2) increased, but the increase trend of CaCO3 content was not obvious. [Conclusion] The study shows that the characteristic soil layer is commonly existed in loess region, especially the eroded loess region, which should be paid attention in the research fields of modern soil science and ecology.%[目的]对黄土高原安塞县纸坊沟流域退耕林土壤1m剖面有机碳含量、粒度、全氮含量、碳氮比、碳酸钙含量进行分析,研究以粒度反映下的土壤异常层理化性质变化,以及各土壤物理化学的响应。[方法]对黄土高原上3个样地各随机选择3个10m×10m的样方并分坡上、坡中、坡下分别挖掘3剖面,间隔10cm

  12. Effects of Film Mulching and Different Ratios of Base Nitrogen to Dressing on Yield and Key Quality of Spring Maize in Dryland of the Loess Plateau%黄土高原旱地秋覆膜及氮肥秋基春追比例对春玉米产量和品质的影响

    Institute of Scientific and Technical Information of China (English)

    王勇; 宋尚有; 樊廷录; 高育峰

    2012-01-01

    [Objective] The objective of this study was to provide principal evidence for combating drought and protecting the seedlings of spring maize based on experiments of soil water conservation by autumn film mulching and N application as basal fertilizer in autumn and dressing in spring. [Method] Experiments of two plastic film application models of autumn and spring mulching and N management were conducted in Loess Plateau dry highland from 1999 to 2010 and from 2001 to 2003, respectively. Water storage efficiency in 0-200 cm soil layers, the maize yields and the key quality were analyzed. [Result] The experimental results showed that autumn plastic film mulching could significantly improve soil wate storge efficiency compared with that of spring mulching. The soil water storage capacity of autumn mulching was 36.7 mm more than that of spring mulching, soil water storage efficiency achieved 78.4%. And maize yield and water use efficient (WUE) was 11 149.8 kg·hm-2 and 33.1 kg·hm-2·mm-1, improved by 16.7 percent and 14.9 percent, respectively. For a fixed amount of N application of 180 kg·hm-2, the WUE and grain proteins content under the combination of 72 kg·hm-2 autumn basal dressing and 108 kg·hm-2 spring top dressing were the highest. [Conclusion] Under the conditions of these experiments, in dry highland of Loess Plateau, autumn plastic film mulching had significant effects on spring maize yield, WUE and soil storage efficiency. The optimization of N fertilizer can increase maize grain yield and get good key nutrient quality synchronously.%[目的]研究玉米秋冬闲期地膜覆盖保墒及优化氮肥秋基春追比例,为抗旱保苗及合理施肥提供理论依据.[方法]采用秋季与春季地膜覆盖对比试验(1999-2010年),监测0-200 cm土层土壤蓄水效率及不同降水年型产量变化.开展氮肥管理试验(2001-2003年),分析氮肥不同基、追肥比例的玉米籽粒产量和关键营养品质.[结果]秋覆膜春播玉米播前1

  13. Analysis of Climate Characteristics of Land Surface Temperature and Energy in the Semi-arid Region in the Loess Plateau%黄土高原半干旱区陆面温度和能量的气候特征分析

    Institute of Scientific and Technical Information of China (English)

    孙昭萱; 张强

    2011-01-01

    利用黄土高原半干旱区"定西陆面过程综合观测试验站"2004年11月至2005年10月的各种陆面物理量综合资料,比较系统地研究了黄土高原半干旱区土壤温度、降水量、地表反照率、地表辐射分量和能量平衡分量的年变化和日变化特征及其影响机制。结果显示,黄土高原陆面过程特征与其他地区有很大不同。土壤温度变化向下传播速度约为2.5~3.5 h/10cm;地表反照率随土壤湿度的增大而减小,两者的相关系数达到了0.5338;而地表反照率随降雪量增大而增大,与降雪量的相关系数为0.6645;长波辐射年最大值出现的时间比总辐射迟1个月左右,年平均日变化中地表和大气对太阳辐射加热大约需要1个小时的响应时间;潜热通量夏季是冬季的5倍多,感热通量有了两个比较明显的峰值,潜热通量、感热通量和土壤热通量的日峰值比净辐射滞后30 min~1 h。%By making use of integrated data of a variety of land surface physical parameters observed in Dingxi Synthetical Experimental Observatory of Land Surface Process in the Loess Plateau from November,2004 to October,2005,annual and daily variations characteristics of soil temperature,precipitation,land surface albedo,surface radiation components and energy balance components in the semi-arid region are systematically analyzed,as well as their influencing mechanism.Results show that the characteristics of land surface process over the Loess Plateau are different from in other regions.Downward transfer velocity of soil temperature is about 2.5~3.5 h/10cm.The land surface albedo decreases with soil moisture increasing,and their correlation coefficient is 0.5338;the land surface albedo increases with snowfall increasing,and the correlation coefficient is 0.6645.The maximum value of long-wave radiation appears later about 1 month than the total radiation.It takes one hour for solar radiation to heat the land surface and atmosphere

  14. 黄土高原北部水蚀风蚀交错区产流条件及径流系数%Runoff Conditions and Runoff Coefficient of the Wind-water Erosion Crisscross Region on the Northern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    卢龙彬; 付强; 黄金柏

    2013-01-01

    为了揭示黄土高原北部水蚀风蚀交错区的产流机制并推求径流系数,为该地区地表水资源的深入研究提供基础数据,选取具有黄土高原北部水蚀风蚀交错区典型气象与水文特征的六道沟流域为研究区.通过分析实测水文数据,从机制上分别研究了试验流域在表层土壤(5-10 cm)达到饱和及不饱和条件下的产流过程,在长历时低强度降雨条件下,产流的必要条件是表层土壤达到饱和且雨强≥0.12 mm/min;在短历时高强度降雨条件下,表层土壤未达到饱和状态时,产流的必要条件是降雨强度≥0.52 mm/min;径流系数与平均降雨强度之间存在着显著的正相关关系;以运动波理论的基础方程式结合GIS技术开发了适用于试验流域的分布式降雨—径流数值模型,模型的误差<3%;基于2005-2009年(5 a)的降雨—径流数值计算,得到试验流域在这5 a的平均径流系数为0.11,从而推求出多年平均径流系数为0.10~0.15.%With an aim to estimate runoff conditions and runoff coefficient,to provide the basis for further studies on surface water resources at the wind-water erosion crisscross region on the northern Loess Plateau,a catchment known as Liudaogou which has representative hydrological and meteorological characteristics of the wind-water erosion crisscross region on the Loess Plateau was chosen as the study site.Runoff conditions were clarified through analysis of the observed rainfall-runoff data.When a long duration with low intensity rainfall occurred,the necessary condition for runoff generation was the topsoil (thickness:5-10 cm) attained saturation and rain intensity ≥0.12 mm/min; when a short duration with high intensity rainfall occurred,the necessary condition for runoff generation was rain intensity≥0.52 mm/min; runoff ratio was proportion to the average rain intensity; a numerical model for rainfall-runoff has been developed for the study site based on kinematic

  15. 基于Le Bissonnais法对黄土高原森林植被带土壤团聚体及土壤可蚀性特征研究%Soil aggregate stability and erodibility under forest vegetation in the Loess Plateau using the Le Bissonnais method

    Institute of Scientific and Technical Information of China (English)

    曾全超; 董扬红; 李鑫; 李娅芸; 刘雷; 安韶山

    2014-01-01

    The composition and stability of soil aggregates are the main indicators of soil structure and quality. For sustainable ecological restoration, soil aggregates stability under different vegetation types in the forest zones of the Loess Plateau was studied using the Le Bissonnais (LB) method. Three sieving methods of LB (SW: slow-wetting sieving method; FW: fast-wetting sieving method;WS:wet-stirring sieving method) were used to simulate light rain, heavy rain and disturbance. Soil samples were collected from 10 types of vegetation in Yanhe Catchment of Yan’an City. The mean weight diameter (DMW), geometric mean diameter (DGM), mass fractal dimension (D) of soil aggregates and soil erodibility (K) were calculated. The results showed that FW treatment was the most destructive to soil aggregate stability, under which soil water-stable aggregate particle size was mainly concentrated in the2 mm size group. It then explained that light rains had no strong damaging effects on soil aggregates. The orders of DMW, DGM, D and K were SW>WS>FW, SW>FW>WS, WS>FW>SW, and FW>WS>SW, respectively, in both 0-10 cm and 10-20 cm soil layers. Under SW, Artemisia gmelinii community and Rosa xanthina community had greater DMW and DGM, and smaller K, indicating the two vegetation types had advantages in soil protection under light rain. Under WS and FW, Platycladus orientalis community and Acer buergerianum communities had DMW and DGM, and smaller K. They were appreciate vegetation types for soil protection under heavy rain and strong disturbance. The results suggested that LB method was appropriately applicable in measuring soil aggregate structure in the Loess Plateau. The LB method not only simulated traditional wet sieving re-sults, but also explained the mechanisms involved in the disintegration of soil aggregates under different conditions in terms of soil structure stability. The results also suggested that the vegetation types significantly influenced soil water-stable aggregates

  16. Interaction of CARD14, SENP1 and VEGFA polymorphisms on susceptibility to high altitude polycythemia in the Han Chinese population at the Qinghai-Tibetan Plateau.

    Science.gov (United States)

    Chen, Yu; Jiang, Chunhua; Luo, Yongjun; Liu, Fuyu; Gao, Yuqi

    2016-03-01

    High altitude polycythemia (HAPC) is a serious public health problem among Han Chinese immigrants to the Qinghai-Tibetan Plateau. This study aims to explore the genetic basis of HAPC in the Han Chinese population. 484 male subjects (234 patients and 250 controls) were enrolled in this study. Genotyping was performed for polymorphisms of I/D in ACE, C1772T and G1790A in exon 12 of HIF-1α, rs2567206 in CYP1B1, rs726354 in SENP1, rs3025033 in VEGFA, rs7251432 in HAMP, rs2075800 in HSPA1L and rs8065364 in CARD14. Gene-gene interaction was assessed by multifactor dimensionality reduction. A significant association was seen between CARD14 polymorphism rs8065364 and risk of HAPC development in male Han Chinese, and the C allele of rs8065364 was a risk factor (odds ratio (OR)=1.59, 95% confidence interval (95% CI)=1.21-2.08). Gene-gene interaction analysis indicated that a synergistic relationship existed between rs3025033 and rs8065364 (1.00%), rs3025033 and rs726354 (0.18%), and rs726354 and rs8065364 (0.17%). The combination of rs8065364 in CARD14, rs3025033 in VEGFA and rs726354 in SENP1 was the best model to predict HAPC development in this study (testing accuracy=0.6183, p=0.0010, cross-validated consistency=10/10). Genetic interactions of SNPs in CARD14, SENP1 and VEGFA might represent a functional mechanism in the pathogenesis of HAPC. PMID:26852650

  17. Influences of stand age on root patterns in a rain-fed jujube (Ziziphus jujube) plantation of Loess Plateau in China%黄土丘陵区不同树龄旱作枣园细根空间分布特征

    Institute of Scientific and Technical Information of China (English)

    李陆生; 赵西宁; 高晓东; 吴普特; 李虹辰; 凌强; 孙文浩

    2015-01-01

    以黄土丘陵区2、6、10、15龄旱作枣林(Ziziphus jujube cv.Junzao)为研究对象,采用根钻法,距树干0.5、1、1.5 m处、分层(0.2 m)钻取土样,分析了旱作枣林细根随树龄的变化特征.结果表明:随着枣林树龄增大,枣林细根根长密度增加,比根长减小;2龄枣树细根主要分布于径向1.5 m以内和垂向1.6 m以上,10、15龄枣树细根分布超过径向1.5 m和垂向3 m以上,并在株间形成根系高密度区,6龄枣树细根径向分布范围大于2龄,垂向分布与10龄和15龄接近;不同树龄枣林细根根长密度均随土层深度增加而减小,且主要集中在0~0.6 m土层中;随着树龄增加,细根根长密度径向分布无差异(10、15龄).研究表明:2、6龄枣林应靠近树干地表处施肥,而理论上成熟期10、15龄枣林可在林内任意位置施肥;同时为防止枣林减产和退化,需增加枣林管理措施以有效降低枣树自身奢侈性耗水和非生产性耗水.%Fine roots (roots≤2 mm in diameter) are the primary organ of absorbing water and nutrients in forest systems. Since the initiation of the large-scale ecological rehabilitation project (known as "Grain for Green" project) by the Chinese central government in 1999, the acreage of the jujube orchard has been increased rapidly on the Loess Plateau mainly for conserving soil plus water and raising economic benefits. However, the knowledge of fine roots dynamics during stand development is lacked to guide management practices for rain-fed jujube plantations, and most studies focused on the vertical dynamic of fine roots, with the method of random sampling and missed characterizing the radial distribution of fine roots. The objective of this study was to investigate the characteristics of fine roots in a rain-fed jujube plantation (Ziziphus jujube Mill. cv. Lizao) with a range of stand ages (2, 6, 10, and 15 years) in Qingjian County in Shaanxi Province (37°15′N, 118°18′E). Specifically, the fine root

  18. Loess and Eolian Dust Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Records of past environment derived from Loess and Eolian dust (silt-sized material deposited on the Earth surface by the surface winds. Parameter keywords describe...

  19. Inhibition of X-ray-induced potentially lethal damage (PLD) repair in aerobic plateau-phase Chinese hamster cells by misonidazole

    International Nuclear Information System (INIS)

    The effect of the 2-nitroimidazole radiosensitizer misonidazole (MISO) and the hydrophilic analog SR-2508 on the repair of X-ray-induced potentially lethal damage (PLD) was studied in plateau-phase Chinese Hamster ovary (HA-1) cells. It was found that although MISO does not radiosensitize aerobic cells, it inhibits the repair of PLD. However, under hypoxic conditions, MISO has no effect on PLD repair. The major portion of the inhibition of PLD repair in aerobic cells requires the presence of MISO only during irradiation; little or no additional inhibition occurs when MISO is present during the postirradiation repair period. Also, treatment of aerobic cells with 5 mM MISO for either 5 or 30 min prior to irradiation is equally inhibitory. This suggests that the presence of MISO in some way modifies the initial lesion under aerobic conditions since it does not increase cell killing as determined by immediate plating but inhibits subsequent repair. The inhibition is concentration dependent; 0.5 mM MISO inhibits PLD repair by one-half while 5-10 mM totally inhibits the repair measured 6 hr postirradiation. This phenomenon suggests that radiosensitization of tissue in vivo by MISO and other 2-nitroimidazoles may not be unequivocal proof of the presence of hypoxic cells

  20. Rock magnetic and DRS characteristics of loess-palaeosol sediments from Bulgaria and their link to palaeo-environmental conditions

    International Nuclear Information System (INIS)

    Complete text of publication follows. One of the best preserved terrestrial records of past climate are in loess-palaeosol sequences around the world. Except classical Chinese loess, European sequences are widely used for palaeoenvironmental reconstructions. Low Danube loess deposits are part of the south-eastern loess cover, linking loess belt in Asia with Central European loess. Its magnetic properties have been extensively studied, putting emphasis on present continental conditions. In the present work, role of Black sea as climatic factor playing role in setting up rock magnetic properties of samples from Durankulak loess outcrop have been studied. Combined use of magnetic and DRS data show that magnetic enhancement of palaeosols is accompanied by an increase of hematite content, suggesting that pedogenic maghemite (magnetite) and hematite are simultaneously formed during warm interglacial periods. Comparison with data from a loess-palaeosol section in the countryside (away from maritime climates) suggests that more humid and warmer conditions favour faster growth of pedogenic Fe oxides towards stable SD magnetic grain sizes. Possible role of diagenetic effects will be discussed.

  1. A simple model for reconstructing geomagnetic field intensity with (10)~Be production rate and its application in Loess studies

    Institute of Scientific and Technical Information of China (English)

    J.; Warren; BECK

    2008-01-01

    A simple model for reconstructing the paleomagnetic field intensity with (10)~Be production rate was used for the first time in Loess (10)~Be studies of Luochuan profile. Using the LGM (Last Glacial Maxmium) method, the climatic effects and geomagnetic modulation effects on loess (10)~Be was separated and in turn the 80 ka geomagnetic excursion sequence reconstructed, of which the globally remarkable geomagnetic excursion events such as the Laschamp (42 ka), Mono Lake (32 ka) during the Last Glacial period were revealed and the paleo-geomagnetic intensity curve from Loess (10)~Be over the past 80 ka was quantitatively reconstructed. The reconstructed paleo-intensity fits well with the paleo-intensity curves (SINT200 and NAPIS75), which indicates the significance of global criterion of the (10)~Be paleo- intensity curve and the future direction of loess (10)~Be tracing studies. Results show the irregular vari-ability of the East Asian monsoon precipitation in Loess Plateau is the main cause that has resulted in the ambiguity of the geomagnetic modulation of the (10)~Be record in the loess, and the intrinsic source component of the loess (10)~Be and inherited fraction of magnetic susceptibility (SUS) are characterized by the "quasi-homogeneous distribution" manner.

  2. 黄土丘陵区不同演替阶段生物结皮对土壤CO2通量的影响%Effects of biological soil crust at different succession stages in hilly region of Loess Plateau on soil CO2 flux

    Institute of Scientific and Technical Information of China (English)

    王爱国; 赵允格; 许明祥; 杨丽娜; 明姣

    2013-01-01

    生物结皮是土壤表面具有光合活性的致密复合层,是土-气界面CO2通量的影响因子之一.本文采用改进的Li-8100土壤碳通量测量系统,研究了黄土丘陵区退耕地上不同演替阶段生物结皮对土壤CO2通量的影响.结果表明:光照条件下,生物结皮土壤CO2通量较除去生物结皮显著下降,其中藻结皮和藓结皮分别下降了92%和305%;生物结皮对土壤CO2通量的降低程度与其生物组成和生物量有关,深色藻结皮和藓结皮土壤CO2通量较裸地分别降低了141%和484%.生物结皮土壤CO2通量的日变化呈降低-升高-降低的趋势,而裸地CO2通量日变化趋势为单峰曲线,藻结皮、藓结皮的碳吸收峰值分别出现在8:00和9:00前后,其CO2通量分别为0.13和-1.02 μmol CO2·m-2·s-1;藻结皮24 h CO2通量排放总量较裸地增加7.7%,而藓结皮减少了29.6%.生物结皮对土壤CO2通量的影响显著,在评价退耕地土壤碳循环时,应考虑生物结皮的影响.%Biological soil crust ( biocrust) is a compact complex layer of soil, which has photosyn-thetic activity and is one of the factors affecting the CO2 flux of soil-atmosphere interface.In this paper, the soil CO2 flux under the effects of biocrust at different succession stages on the re-vegetated grassland in the hilly region of Loess Plateau was measured by a modified LI-8100 automated CO2 flux system.Under light condition, the soil CO2 flux under effects of cyanobacteria crust and moss crust was significantly decreased by 92% and 305% , respectively, as compared with the flux without the effects of the biocrusts.The decrement of the soil CO2 flux by the biocrusts was related to the biocrusts components and their biomass.Under the effects of dark colored cyanobacteria crust and moss crust, the soil CO2 flux was decreased by 141% and 484% , respectively, as compared with that in bare land.The diurnal curve of soil CO2 flux under effects of biocrusts presented a

  3. Effect of Se,Zn and Mo on Yield and Contents of Nutrient Elements and Selenium and Cadmium of Potato and Cabbage on the Loess Plateau%硒锌钼对黄土高原马铃薯和小白菜产量及营养元素与硒镉含量的影响

    Institute of Scientific and Technical Information of China (English)

    王建伟; 王朝辉; 毛晖; 赵护兵; 昝亚玲; 李孟华

    2012-01-01

    黄土高原旱地土壤微量元素硒锌钼潜在缺乏,不仅影响农作物产量,还降低农产品的矿物营养品质,研究施用硒锌钼肥料对该地区作物生长及可食部分营养元素含量的影响具有重要意义.通过田间试验,研究了硒锌钼肥单独土施、硒锌肥配施、硒锌钼肥配施对马铃薯和小白菜产量及营养元素和硒镉含量的影响.结果表明:硒肥提高了马铃薯块茎和小白菜叶片硒含量,分别由对照的0.02 mg· kg-1和0.09 mg· kg-1提高到1.51~2.15 mg·kg-1和13.03~19.44 mg·kg-1,钼肥提高了马铃薯块茎和小白菜叶片钼含量,分别由对照的0.43 mg· kg-1和2.3 mg· kg-1提高到1.03~1.16 mg·kg-1和17.7~19.9 mg·kg-1,单施与配施处理间无显著差异.锌肥土施或锌与硒、钼肥配合土施不但使小白菜叶片中的锌含量由对照的21.0 mg·kg-1显著提高到48.1~68.4 mg· kg-1,还使镉含量显著降低50%以上;施锌对马铃薯块茎的锌含量无显著影响.硒锌钼肥单施或配施均对马铃薯和小白菜产量及氮、磷、钾、硫、钙、镁、铁、锰、铜、硼含量无显著影响.因此,在黄土高原旱地,硒钼配合土施可同时提高马铃薯块茎的硒钼含量,硒锌钼配合土施可同时提高小白菜叶片的硒锌钼含量.%On the dryland of the Loess Plateau in China, deficiency of Se, Zn and Mo not only impacts crop yields, but also reduces the essential nutrient concentrations in agricultural products. Therefore, in order to improve the crop yield and its nutritional quality, field experiments were carried out to investigate the effects of separately soil-applied selenium(Se), zinc(Zn) and molybdenum (Mo) fertilizer or their combination on the yield and concentrations of mineral nutrient, Se and cadmium (Cd) of potato and cabbage. Obtained results showed that soil Se application significantly increased Se concentrations in potato tubers and cabbage leaves from 0.02 mg·kg-1 and 0.09 mg·kg-1

  4. 黄土高原水蚀风蚀交错带不同立地条件下土壤呼吸特征%Soil respiration characteristics under different site conditions in wind-water crisscross erosion region on Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    付微; 黄明斌※; 邵明安; 杜书立

    2013-01-01

      水蚀风蚀交错带是黄土高原土壤侵蚀最严重地区,该地区立地条件复杂,土壤质地有较大的空间变异性,对生态系统碳循环过程产生重要影响。该文选取土壤质地为立地条件的主要参考因子,利用便携式CO2分析仪对黄土高原水蚀风蚀交错带不同立地条件下2种典型灌木(柠条和沙柳)土壤呼吸特征进行了连续2a的野外对比研究,分析不同立地条件下灌木林地土壤呼吸之间的差异,阐明土壤呼吸的动态变化及其对土壤温度的敏感性。结果表明:在不同立地条件下,柠条林地黄绵土土壤呼吸高于风沙土,相反,沙柳林地风沙土土壤呼吸高于黄绵土。每种灌木林地在不同立地条件下土壤呼吸呈现明显的季节性变化,土壤呼吸速率的高峰值出现在7、8月份。不同立地条件下土壤呼吸与土壤温度呈现显著指数函数关系,每种灌木林地黄绵土土壤呼吸的温度敏感性系数 Q10高于风沙土,从而对土壤温度的响应更为敏感。%  The wind and water erosion transitional belt of the Loess Plateau experiences intensive soil erosion, where the site conditions are complicated. The spatial heterogeneity of soil texture can alter spatial heterogeneity of soil respiration, with a consequent impact on carbon cycling of the ecosystem. The objective of this study was to investigate the soil respiration characteristics of two dominant shrubs (Caragana Korshinkii and Salix psammophila) under different site conditions, and elucidate the temperature sensitivity of soil respiration in the wind and water erosion transitional belt of the Loess Plateau. Experiments were performed with two site conditions (silt loam soil and sandy soil) for each shrub during the growing seasons from 2009 to 2010. Soil respiration was measured every other day with an ultra-light portable photosynthesis system (CI-340, CID Inc., USA) fitting with a soil

  5. Diurnal dynamic characteristics and temperature sensitivity of soil CO2 flux of biocrusts in different erosion regions on the Loess Plateau%黄土高原不同侵蚀区生物结皮土壤CO2通量日动态特征及其温度敏感性

    Institute of Scientific and Technical Information of China (English)

    王爱国; 赵允格; 许明祥; 王一贺; 杨丽娜; 明姣

    2013-01-01

    Biological soil crusts (biocrusts),as ubiquitous living covers on soil surface in arid and semi-arid regions,exerted a potential effect on soil CO2 flux.In the study,the diurnal dynamic of soil CO2 flux of biocrusts in different erosion regions (water erosion region,water-wind alternated erosion region and wind erosion region) on the Loess Plateau was measured by LI-8100 automated soil CO2 flux system and the temperature sensitivity of soil respiration was analyzed.The results showed that CO2 flux of soil with activated biocrusts decreased compared with the flux without biocrusts in the three regions.The daily soil CO2 flux with biocrusts was reduced by 5.0%,8.9% and 20.5% in the water erosion region,water-wind alternated erosion region and wind erosion region,respectively.The soil CO2 fluxes in the daytime showed a simple peak curve.The peak fluxes were observed during 12:00-14:00.The value of CO2 flux in the water erosion region,the water-wind alternated erosion region and the wind erosion region was 1.64,1.64 and 1.37μmol·m-2·s-1,respectively.Soil respiration rate increased along with the rising temperature,and the relationship can be described by an exponent model.The range of temperature sensitivity quotients (Q10) was changed between 1.93 and 2.43 in the water erosion region and in the water-winderosion region while the range of Q10 values was 4.80 ~5.56 in the wind erosion region,which indicated that the effect of temperature on biocrusts soil respiration in the wind erosion region was more sensitive than that in the water erosion region and the water-wind erosion region.The study suggested that the effect of biocrusts on soil CO2 flux should be taken into consideration when discussing the soil carbon exchange on the Loess Plateau.%利用LI-8100土壤碳通量自动观测系统监测了黄土高原不同侵蚀区(水蚀区、水蚀风蚀交错区、风蚀区)生物结皮土壤CO2通量的日变化,分析了土壤呼吸的温度敏感性.结果表

  6. 黄土高原河龙区间最大日雨量(PMP)极值拟合及时空演变特征%Fitting of the PMP Values and Identifying Its Spatiotemporal Characteristics in the Helong Section on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    马芹; 张晓萍; 万龙; 马瞳宇; 孙艳萍; 徐金鹏; 雷泳南

    2012-01-01

    There is high frequency of the heavy precipitation events in the Helong Section on the Loess Plateau.And the heavy precipitation events can cause severe soil erosion.The paper deals with the estimation of the return period of precipitation extremes in the Helong Section on the Loess Plateau.In this study,the daily precipitation datasets at 24 meterological stations from 1957—2009 were used to estimate the probable maximum precipitation(PMP) in the Helong Section.Two extreme distribution models of probability estimations were compared to identify the applicability: the GEV distribution and the Gumbel distribution.The spatiotemporal characteristics for the extreme events were detected.The results showed that:(1) for the return period less than 10 years,there was little difference between the two distributions for estimation of the PMP.But for the return period greater than 20 a,the GEV distribution was properly more than the Gumbel distribution to estimate the PMP in the Helong Section.When there were several heavy precipitation events with the similar precipitation values,the Gumbel distribution is properly more than the GEV distribution;(2) the PMP values in the Helong Section for the return period of 2 a,5 a,10 a,20 a,50 a,100 a were between 40~70,50~85,60~100,70~110,85~130,95~150 mm,respectively.The PMP value for a given return period was higher in the Yanhe River in the south and in the Ordos Desert in the northwestern Helong Section.However,it was lower in the northeastern part.The PMP values estimated by the daily precipitation data of the three period of 1950s—1960s,1970s—1980s,1990s—2000s were varied.The PMP values estimated by the datasets of 1950s—1960s in the Taiyuan and Yulin stations were higher.However,at the Dongsheng,Xingxian and Yanan stations,the estimated PMP values were higher for the datasets of 1970s—1980s.%黄土高原河龙区间暴雨可以造成极为严重的土壤侵蚀。为了探究河龙区间暴雨重现

  7. Dynamic Simulation of Land Use in the Southern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Bin; GUO

    2014-01-01

    To study the dynamic changes of land use and predict the future land use scenarios based on the current land use,this paper uses Cellular Automata- Markov( CA- Markov) model to simulate the landscape pattern in 2030. The results show that in the study area during the period 1980- 2005,grassland and construction land increased,and woodland increased slightly; waters and unused land decreased,and arable land underwent dramatic changes. The simulation precision of CA- Markov model is 87. 28%,indicating that the use of it for simulation is reliable. The land use of the study area will be changed greatly in the future. This method provides a reference for the regions to carry out land prediction,and the research results can provide a basis for the study of optimization of land.

  8. Spatial variability of soil nutrients and its relations to topographical factors in hilly and gully area of Loess Plateau%黄土高原沟壑区土壤养分空间变异及其与地形因子的相关性

    Institute of Scientific and Technical Information of China (English)

    宋丰骥; 常庆瑞; 钟德燕

    2011-01-01

    【目的】研究黄土高原沟壑区土壤养分空间分布特征及变异规律,分析地形因子对土壤养分空间分布的影响,为土壤养分的有效利用与管理提供理论依据。【方法】运用地统计学和GIS技术相结合的方法,研究地处黄土高原沟壑区的安塞县土壤有机质、碱解氮、有效磷和速效钾的空间变异特征,并利用数字高程模型(DEM)提取坡度、水平曲率、垂直曲率、地形湿度指数和河流动能指数等5个地形因子,分析土壤养分含量与这些地形因子之间的相关性。【结果】(1)土壤有机质、碱解氮、有效磷和速效钾4种土壤养分的变异系数为14.14%~26.84%,块金效应值为16.45%~45.87%。(2)研究区西南部土壤养分含量较高,北部土壤养分含量相对较低。(3)坡度与有机质、碱解氮和有效磷含量呈显著或极显著负相关;水平曲率与有机质和速效钾含量呈显著负相关;地形湿度指数与有机质和速效钾含量呈显著正相关。【结论】安塞县土壤有机质、碱解氮、有效磷和速效钾养分均具有中等变异性,速效钾具有很强的空间相关性;坡度较小、土壤水分较多、水土流失较轻微的地区,土壤养分含量较高;在施肥时,应增大研究区北部氮、磷的施用量。%【Objective】 The spatial distribution and variability of soil nutrients were analyzed in hilly and gully area of Loess Plateau,and the influences of topographical factors on spatial distribution of soil nutrient were also analyzed.This study provided a theoretical basis for the effective use and management of soil nutrients.【Method】 Geostatistics combined with geographical information system(GIS) technique were applied to analyze the spatial variability of organic matter,available nitrogen,available phosphorus and available potassium in Ansai county which belongs to hilly and gully area of Loess Plateou.5 topographical factors gradient

  9. 黄土高原冬小麦田土壤CH4通量对人工降水的短期响应%Short-term response of soil CH4 flux to simulated precipitation in a winter wheat field on the Loess Plateau, Northwest China

    Institute of Scientific and Technical Information of China (English)

    刘全全; 王俊; 陈荣荣; 刘文兆; Upendra M.Sainju

    2015-01-01

    为了解黄土高原旱作农田土壤CH4排放对不同降水事件的短期响应过程,分别在冬小麦拔节期和夏闲期进行了人工模拟降水试验,对1~32 mm不同降水量模拟降水后0~72 h土壤CH4排放通量进行了观测.结果表明:模拟降水后旱作农田土壤CH4排放通量变化特征表现出两种不同的模式:低降水量(1、3和8 mm)处理为波动变化,高降水量(16和32 mm)处理呈单峰型变化.降水后72 h土壤CH4累积通量(CH4-C)与降水量(P)呈显著线性正相关(冬小麦拔节期:CH4-C=2.45P-6.09,R2=0.92,P<0.01;夏闲期:CH4-C=2.43P-4.73,R2=0.91,P<0.01).相关分析表明,土壤CH4通量与土壤含水量和土壤微生物生物量碳含量显著相关,而与土壤温度不相关.少量降水(1~8 mm)可以在短期内促进旱作农田土壤对CH4的吸收,加强土壤作为大气CH4汇的强度,然而这种促进作用也会随降水量的增大和降水的下渗而削弱.较大降水(≥16 ram)可以刺激土壤产甲烷菌活性促进CH4释放,在短期内使旱作农田土壤由单一的汇功能转变为汇源双重功能.%To understand the short-term response of soil CH4 flux to different precipitation events in a winter wheat field on the Loess Plateau,we conducted precipitation simulation experiments during winter wheat jointing stage and summer fallow period to measure the soil CH4 flux in 0 to 72 h after precipitation simulation of 1 to 32 mm.Results showed that CH4 flux during 0 to 72 h fluctuated at 1 to 8 mm of precipitation application and peaked at 16 and 32 mm.Cumulative CH4 flux after 72 h of precipitation (CH4-C) increased linearly with the precipitation amount (P) (wheat jointing stage:CH4-C=2.45P-6.09,R2=0.92,P<0.01; summer fallow:CH4-C=2.43P-4.73,R2=0.91,P<0.01).Statistical analysis showed that CH4 flux was also correlated with soil water content and microbial biomass carbon but not with soil temperature.In the long run,small precipitation events (1-8 rm) could enhance

  10. 黄土高原干旱半干旱地区气溶胶光学厚度遥感分析%Analyses on Aerosol Optical Depth over Arid and Semi-Arid Region of Loess Plateau Using Remote Sensor Data

    Institute of Scientific and Technical Information of China (English)

    胡蝶; 张镭; 王宏斌

    2013-01-01

    The characteristics of diurnal,monthly change of aerosol optical depth (AOD),and monthly change of Angstrom index (α-index) were analyzed using data of Sun Photometer (CE-318) at the SemiArid Climate and Environment Observatory of Lanzhou University (SACOL) from August 2006 to October 2008,it is found that the amplitude of the diurnal AOD change in spring is larger than that in other seasons,and it shows the double-peak characteristic.AOD is smaller in September and larger in April and December,α-index reaches its minimum in April,and maximum in July.Correlation coefficients of 550 nm AOD retrieved from sun photometer data and that from Terra and Aqua MODIS data are 0.69/0.62.The errors are analyzed from aspects of surface albedo assumption,aerosol model,and influence of clouds.Additionally,Terra and Aqua MODIS data are used for analyzing spatial and seasonal characteristics of AOD above the arid and semi-arid regions of Loess Plateau.Results show that east region has larger AOD,and local maximums are corresponding to capital cities of those provinces.AOD above the arid and semi-arid regions reaches maximum in spring and minimum in autumn.The Deep Blue algorithm for Aqua-MODIS is a good supplement for the retrieval of AOD above bright surface of deserts in Northwest China.%利用兰州大学半干旱气候与环境观测站2006年8月-2008年10月太阳光度计(CE-318)观测资料和同期卫星MODIS(Terra和Aqua)产品资料,分析了该站气溶胶光学厚度(AOD)日变化、月变化和Angstrom波长指数(α指数)月变化特征,发现春季AOD日变幅最大,存在双峰现象,秋、冬季较小;9月AOD最小,4月和12月AOD较大;α指数在4月最小,7月最大.采用太阳光度计反演的550 nm AOD与Terra-MODIS和Aqua-MODIS AOD产品相比较,Terra-MODIS与太阳光度计AOD相关系数为0.69,大于Aqua-MODIS的0.62.并从地表反照率假设、气溶胶模型选择和云影响等方面分析了产生对比偏差的原因,进一步分析了

  11. 黄土高原北部水蚀风蚀交错带沟壑地形的降雨反应特性%Responsive Characteristics of Rainfall of Gully Landform in Wind-Water Erosion Crisscross Region on the Northern Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    黄金柏; 卢龙彬; 付强; 王斌; 温佳伟

    2013-01-01

    为揭示黄土高原水蚀风蚀交错带沟壑地形的降雨反应特性,选取该区具有典型水文及气象特征的六道沟流域作为研究区域,基于对所选沟道的沟顶及沟底2005-2009年雨季同期观测降雨数据(38次集中降雨事件)的分析,揭示沟壑地形对降雨反应的特性;通过对典型降雨—径流事件的分析,分别推求长历时低强度降雨以及短历时高强度降雨条件下降雨强度与产流的关系.结果表明:沟顶单次降雨事件的降雨量,3,5,10 min最大雨强及平均雨强均是沟底对应值的1.3倍以上;沟顶单次降雨事件降雨量的3,5,10min雨强各序列标准差均大于沟底对应序列的值;沟顶与沟底的降雨量序列,各时间间隔的最大、平均雨强序列均存在着较高的正相关性,相关系数在0.9以上;表层土壤在饱和及不饱和条件下,产流的必要条件分别是5 min平均降雨强度达到0.12,0.52 mm/min.%The objectives of this study were to explore the responsive characteristics of rainfall of gully landform in wind-water erosion crisscross region on the northern Loess Plateau.The Liudaogou catchment which had the representative hydrological and meteorological characteristics in the wind-water erosion crisscross region was chosen as the study location.Rainfall observation was carried out for the period from 2005 to 2009.The 38 rainfall events which occurred in rainy season were adopted for analysis.The relationships between rain intensity and runoff generation were estimated through analyzing the representative rainfallrunoff events for the long-duration and low-intensity rainfall events and the short-duration and high-intensity rainfall events,respectively.The results indicated that the rainfall amount of each rainfall event,the maximum rain intensity and mean rain intensity of 3,5,10 min of the gully-top were higher than 1.3 times of that of the gully-bottom.The root-mean-square deviation for each series such as

  12. 黄土丘陵区不同降水量带生物结皮对土壤氮素的影响%Impacts of biological soil crusts on soil nitrogen in different rainfall regions in hilly areas of the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    明姣; 赵允格; 许明祥; 杨丽娜; 王爱国; 姚春竹

    2013-01-01

    黄土丘陵区生物结皮广泛发育,可通过固氮作用影响土壤氮素水平,但该区生物结皮对土壤氮素水平的影响鲜见报道.本文通过野外调查结合采样分析,研究了黄土丘陵区不同降水量带生物结皮组成、覆盖度差异及其对土壤氮素水平的影响.结果表明,1)黄土丘陵区不同降水量带生物结皮覆盖度无显著差异,但组成有差别;2)不同降水量带土壤氮素含量剖面分布具有明显的分层特征,生物结皮显著增加了结皮层土壤氮素含量,对下层土壤影响较小,结皮层下0-2 cm、2-5 cm、5-10 cm土层中氮素含量差异不显著;3)生物结皮层土壤全氮、碱解氮及微生物氮在不同降水量带差异不显著,而0-2 cm、2-5 cm、5-10 cm土壤全氮、碱解氮及土壤微生物氮含量在200~300 mm降水量带小于300~600 mm降水量带.研究结果揭示了黄土丘陵区生物结皮对土壤氮素的贡献,而不同降水量带生物结皮对土壤氮素的贡献差异不显著的原因有待于进一步研究.%Biocrusts ( biological soil crusts) , as ubiquitous living covers on soil surface of the revegetated grasslands in the hilly Loess Plateau regions, are potential influence factors on soil nitrogen contents. However, studies on the influence of biocrusts on soil nitrogens in this region were fresh. The objective of the paper was to determine the impact of biological soil crusts on soil nitrogen contents. Field investigation was conducted, and the contents of soil total nitrogen, soil alkali-hydrolyzable nitrogen and soil microbial nitrogen in different soil layers from various rainfall regions were analyzed. The results show that the coverage of biocrusts in different rainfall regions have no significant differences, while the compositions of biocrusts are different. The formation of the biocrusts enriched nitrogen (soil total nitrogen, alkali-hydrolyzable nitrogen and soil microbial nitrogen) in the upper layers of soils

  13. Spatio-temporal Evolution of Agricultural Eco-efficiency in Loess Plateau of East Gansu Province:A Case Study of Qingyang City%陇东黄土高原农业生态效率的时空演变分析--以庆阳市为例

    Institute of Scientific and Technical Information of China (English)

    张子龙; 鹿晨昱; 陈兴鹏; 薛冰

    2014-01-01

    Based on the definition of ecological efficiency raised by World Business Council for sustainable de-velopment (WBCSD), the article applied undesired-output SBM model of Data Envelopment Analysis (DEA) to analyze the spatio-temporal evolution of agricultural eco-efficiency in Loess Plateau of East Gansu Province in 2001-2011. The results indicated that: the agricultural ecological-efficiency in Qingyang City is declining overall, and the spatial discrepancy of eco-efficiency is enlarging. According to the spatial distribution of eco-efficiency, Qingyang can be divided into two regions: 1) The high agricultural eco-efficiency region in-cludes Xifeng, Heshui, Ningxian, Zhengning county which possess good ecological environment, abundant wa-ter resource and developed agriculture. 2) The low agricultural eco-efficiency region includes Qingcheng, Hua-chi, Huanxian, Zhenyuan county which have fragile ecological condition and the scarce water resource. The reasons for inducing low eco-efficiency are disproportional factor inputs, low efficiency of resources utiliza-tion and excessive redundancy of undesired outputs. Furthermore, the article analyzed the redundancy of ele-ments of agricultural input in the regions where have lower ecological efficiency in order to put forward the way to improve the ecological efficiency.%以地处黄土高原的庆阳市为例,基于世界可持续发展工商理事会(WBCSD)对生态效率内涵的界定,应用数据包络分析(DEA)中的非期望产出SBM模型,对2001~2011年间该地区农业生态效率的时空演变进行分析,结果表明:庆阳市农业生态效率总体上呈现下降趋势,其空间差异在不断扩大。依据生态效率的空间分布状况,基本可以将庆阳市分为2种类型:生态环境较好、水资源较为充沛、农业较为发达的西峰区、合水县、宁县和正宁县的农业生态效率相对较高;而生态环境较为脆弱、水资源短缺的庆城县、

  14. Dust deposition during the Early Holocene on the loess plateaus of the Vojvodina region in Northern Serbia

    Science.gov (United States)

    Markovic, Slobodan; Timar-Gabor, Alida; Stevens, Thomas; Guo, Zhengtang; Hao, Qingzhen; Song, Yang; Hambach, Ulrich; Lehmkuhl, Frank; Peric, Zoran; Obreht, Igor; Zeeden, Christian; Veres, Daniel; Gavrilov, Milivoj

    2015-04-01

    The Northern Serbian province of Vojvodina is a lowland area encompassing the confluence of the Danube, Sava, Tisa (Tisza), Drava, Morava and Tamiš (Temes, Timiş) rivers, which separate several remnant loess plateaus. Loess sediments in the Vojvodina region are among the oldest and most complete loess-paleosol formations in Europe. These thick sequences contain a detailed paleoclimatic record since the Early Pleistocene. The better preservation of Serbian loess-paleosol sequences compared to other European loess records is most likely related to the persistence of much drier conditions in the region, coupled with "plateau-like" dust accumulation style. Recently and through detailed luminescence-based chronological investigations of accumulation derived from several loess sections we aimed at addressing the timing of the onset of Holocene soil (S0) formation in the wider region. So far, the chronological results demonstrate a lack of intensive pedogenesis coeval with the postulated Holocene onset (ie., 11.7 ka BP), and continuation of Aeolian dust deposition during the Early Holocene in some of the investigated sections. Lake sediment and speleothem records from the wider area also suggest that, at least regionally, the hydroclimatic characteristics of the Early Holocene differed markedly. This evidence leads to an important question about the validity of previously generalized direct stratigraphic correlations between regional terrestrial environmental archives and global marine and ice core records (direct synchronization of records vs. acknowledging leads/lags), that employ the Late Pleistocene/Holocene boundary at 11.7 as an absolute tie point.

  15. Analysis of the causes of large-scale loess landslides in Baoji, China

    Science.gov (United States)

    Shi, J. S.; Wu, L. Z.; Wu, S. R.; Li, B.; Wang, T.; Xin, P.

    2016-07-01

    Landslide hazards are common in western China. Understanding the mechanism of landslides in loess-covered regions is particularly important for landslide risk assessment. A detailed landslide survey including large-scale slide drilling and geophysical exploration was carried out at the edge of the Loess Plateau on the north side of the Wei River in China. We reconstructed the geomorphological evolution model of the Wei River and analyzed slope structures and lithology. Engineering geologic conditions and active fault properties in the landslide regions were investigated. The results showed that paleogeomorphology of the north slope of the river gradually lowered from south to north. Ancient landforms showed a gradual transition to the south Sanmen Lake Basin from the piedmont alluvial plain during the Pliocene to early Pleistocene. The lake basin in the southern part of the study area gradually retreated, and the Wei River formed in the early Pleistocene. The main river flow shifted northward because of neotectonic movement and periodic climate changes until the Holocene, and then gradually moved southward to produce the current landforms. The active Wei River fault at the edge of the Loess Plateau acted as a route of water infiltration, weakening the structural planes. Erosion and rise of the groundwater table caused old (occurrence during the Late Pleistocene) and ancient (occurrence before the Late Pleistocene) landslides to form on the edge of the plateau along active fractures and interfaces of Pliocene sand, gravel and clay. These were multiple deep-seated rotational slides and/or multiple perched translational landslides. Slope stability analysis indicated that the complex landslides that occurred in the loess areas in recent years were closely related to the distribution of water and Pliocene clay.

  16. Biodiversity and conservation in the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Tibetan Plateau (Qinghai-Xizang Plateau) is a unique biogeographic region in the world, where various landscapes, altitudinal belts, alpine ecosystems, and endangered and endemic species have been developed. A total of 26 altitudinal belts, 28 spectra of altitudinal belts, 12,000 species of vascular plant, 5,000 species of epiphytes, 210 species of mammals, and 532 species of birds have been recorded. The plateau is also one of the centers of species formation and differentiation in the world. To protect the biodiversity of the plateau, about 80 nature reserves have been designated, of which 45 are national or provincial, covering about 22% of the plateau area. Most of the nature reserves are distributed in the southeastern plateau. Recently, the Chinese government has initiated the "Natural Forests Protection Project of China,' mainly in the upper reaches of the Yangtze and Yellow rivers. "No logging" policies have been made and implemented for these areas.

  17. 黄土高原半干旱丘陵区不同树种纯林土壤性质极化研究%SOIL POLARIZATION UNDER PURE STANDS OF DIFFERENT TREE VARIETIES IN SEMI-ARID HILLY AREAS OF THE LOESS PLATEAU

    Institute of Scientific and Technical Information of China (English)

    刘增文; 段而军; 刘卓玛姐; 冯顺煜

    2009-01-01

    to polarization (I = P/R) were proposed for polarization analysis based on results of determination of soil properties of soil samples collected from a variety of mature stands of pure and mixed forests using a multi-point mixed sampling method at multiple sites in the semi-arid, hilly area of loess plateau. Results show very strong polarization (P>0.20) of the following soil properties: chemical properties under Pinus tabulaeformis forest; chemical and biological properties under Platycladus orientalis, Robinia pseudoacacia and Hippophae rhamnoides forests; chemical, biological properties and trace elements content under Ulmus pumila forest; biological properties under Betula platyphylla forest; and biological and physical properties under Acer ginnala forest. Among the species in this study, pure stands of P. tabulaeformis and R.pseudoacia resulted in serious depletion of soil nutrient reserves; Pure stands of P. orientalis increased soil fertility; Pure stands of U. pumila increased soil fertility but decreased trace elements content; Pure stands of B. platyphylla worsened soil biological properties; Pure stands of A. ginnala led to depletion of soil nutrient reserves and deterioration of soil biological properties; and Pure stands of H. rhamnoides did to depletion of soil nutrient reserves and degradation of soil biological and physical properties. The anti-polarization capacities of P. simonii and P. tabulaeformis were the highest and of U. pumila the lowest. Relative to anti-polarization capacity, the ratios of polarization resistance to polarization of the stands fell into the category of more than "medium" (I_a>0.40)including chemical and physical properties under P. tabulaeformis forest, all the soil properties as a whole under P. orientalis, R.pseudoacia and U. pumila forests, and biological, physical and chemical properties under B. platyphylla forest.

  18. Effects of Long-term Fertilization on Diversity of AmmoniaOxidizing Archaea Communities and Abundance in Dry Highland Soil of Loess Plateau%长期施肥对黄土旱塬黑垆土氨氧化古菌群落多样性和丰度的影响

    Institute of Scientific and Technical Information of China (English)

    武传东; 辛亮; 李秀颖; 王保莉; 曲东

    2011-01-01

    [Objective] In order to improve the efficiency of nitrogen utilization and explicate the function of ammonia-oxidizing archaea (AOA) under the changes of soil quality in the Loess Plateau, the community structure diversity and abundance of AOA were studied. [Method] The influence of long-term fertilization treatments including CK, M, NM, PM and NPM on soil AOA community structure diversity and amoA gene copy numbers were analyzed by restriction fragment length polymorphism (PCR-RFLP) and real-time PCR. [Result] From the clone libraries of the different fertilization treatments, there were 25,18,29,20 and 30 restriction endonuclease types, respectively. The a diversity indices indicated that there was a pronounced difference among five fertilizer treatments. The OTUs was the highest in NPM treatment and the lowest diversity in M treatment. The rescaled distance matrix tree indicated that the different fertilization had the largest convergence coefficient of AOA community types with the CK treatment soil, so the different fertilization led to significant changes of AOA communities. The amoA gene copy numbers of AOA changes were different among the treatments, whereas the highest copy numbers were detected in the NPM treatment, and had a pronounced difference with other fertilizer treatments. All preponderant sequences of AOA fell within soils/fresh water sediments based on phylogenetic tree of amoA gene amino acid sequences analysis. [Conclusion] Long-term fertilization resulted in changes of AOA community diversity and abundance.%[目的]研究长期不同施肥制度下黄土旱塬黑垆土氨氧化古菌群落多样性和丰度的变化,为提高黄土高原地区氮素利用效率、检测土壤质量变化提供重要依据.[方法]利用PCR-RFLP技术和Real-time PCR技术分析无肥(cK)、有机肥(M)、氮肥+有机肥(NM)、磷肥+有机肥(PM)、氮磷肥+有机肥(NPM)等5种长期施肥处理对土壤氨氧化古菌群落结

  19. Long-term Fertilization Determining Ammonia-oxidizing Organism Abundance and Distribution in Dry Highland Soil of Loess Plateau%长期施肥对旱地土壤中氨氧化微生物丰度和分布的影响

    Institute of Scientific and Technical Information of China (English)

    辛亮; 武传东; 曲东

    2012-01-01

    采用基于氨单加氧酶基因(amoA)的荧光定量PCR技术,以黄土高原旱地土为材料,研究长期施肥对土壤氨氧化细菌和氨氧化古菌丰度的影响,并分析环境因素与氨氧化菌丰度的关系.以不施肥土壤为对照(CK),设置3个施肥处理,分别为单施磷肥(P),氮、磷共施(NP)和氮、磷、有机肥共施(NPM)3个处理.结果表明,不同处理氨氧化菌amoA基因拷贝数为1.326×106~1.886×106 g1,各处理间氨氧化细菌丰度差异不显著;氨氧化古菌的arch-amoA基因拷贝数为1.329×106~4.510×106 g-1,表现为处理NPM> NP>CK>P,NPM处理为对照的3.314倍,二者呈现显著性差异.采用DCCA法对4个处理进行环境相似度分类,结果显示,P和NPM处理、CK和NP处理分别构成了2个相似类群;4个处理和12个环境因子的关联(CCA)分析表明,不同处理中的氨氧化微生物活跃度以及氨氧化过程强度表现为处理NMP>NP>CK>P;不同环境因子和不同施肥处理生境相似度分布存在不同的关系,其中反映氨氧化过程的硝态氮含量、氨氧化细菌和氨氧化古菌丰度,以及代表微生物生长主要环境因素的pH值、含水量、全氮和有机碳含量与不同施肥处理导致的生境相似度的分布关系最为紧密.%Real-time PCR with primers targeting Ammonia monooxygenase subunit A gene iamoA) was performed to quantify abundance of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing ar-chaea (AOA) in dry highland soilt long-term fertilized, from Loess Plateau. We also investigated the relationship between environmental factors and abundance of ammonia-oxidizing organism. The treatments were no fertilizer (CK), phosphate (P), nitrogen/phosphate fertilizers (NP), and NP combined with organic fertilizer (NPM). We found that fertilization caused no significant difference on the amoA gene copy numbers of AOB arranging from 1, 326× 106 to 1. 886 × 106 copies · g-1 dry soil. In contrast, abundance of

  20. 黄土丘陵区生物结皮对土壤磷素有效性及碱性磷酸酶活性的影响%Impacts of biological soil crust on availability of phosphorus and phosphatase activity in hilly regions of the Loess Plateau, China

    Institute of Scientific and Technical Information of China (English)

    张国秀; 赵允格; 许明祥; 高丽倩

    2012-01-01

    Biocrusts (biological soil crusts ), as ubiquitous living covers on soil surface of the revegetated grasslands in hilly regions of the Loess Plateau, are potential influence factors on the availability of soil P (phosphorus). However, researches focus on the relationship between soil P availability and development of biocrusts were still fresh so far. Impacts of biocrusts on soil total P, available P and phosphatase activity were investigated in revegetated grasslands at different stages of biocrusts developed after the survey of biocrusts distribution. The objects of the study were to determine the influences of biocrusts development on the availability of soil P in the region. The results show that the biological crusts could significantly improve soil total phosphorus contents in the biocrusts layers, while the contents of total phosphorus in 0-10 cm layers are not significant. Soil available phosphorus contents of the biocrusts in the study area are in the range of 3.27-5.87 mg/kg, which are accounting for O. 57%-0. 95% of total P in the same layer. The alkaline phosphatase activities in biocrusts are significantly higher than those of the lower soils (0-10 cm) 3-81 times. The effects of biological crusts on the availability of soil P and phosphatase activity are related to the developmental stages of biocrusts. The biological crusts increase availability alkaline phosphatase activity and organic matter, of soil phosphorus. These results suggest that and reduce the crusts on soil pH, finally improve the availability of soil P could be significantlyenhanced for the formation of biocrusts.%黄土丘陵区生物结皮广泛发育,可影响土壤磷素有效性。目前鲜见生物结皮对土壤磷素有效性的研究报道。本文以该区不同年限退耕地的生物结皮为研究对象,通过野外调查和室内分析,研究了生物结皮对土壤全磷、有效磷及碱性磷酸酶活性的影响。结果表明,1)生物结皮的形

  1. STUDY ON THE DYNAMIC PROCESS OF RILL EROSION OF LOESS SLOPE SURFACE

    Institute of Scientific and Technical Information of China (English)

    Zhanbin LI; Kexin LU; Wenfeng DING

    2001-01-01

    Rill erosion is a dominant process of morphological evolution of the Loess Plateau in China, and deliveries much loess sediment to rivers. Data from two flume experiments conducted on the bare and glass-covered beds indicated that the fill flow develops into a series of rolling waves. The shear stress on the rill bed distributes unevenly both spatially and temporally. A new method based on the energy conservation law is proposed in this study. Thus the relationship between the runoff energy consumption from the interaction of water flow and slope bed and soil detachment is formulated. The results showed that the data for the soil detachment rate on slope (Dr) and the energy consumption of runoff (E1) fitted well with newly-developed function. The rill erosion occurs when the runoff energy consumption exceeds a critical value.

  2. Spatial variation of shallow and deep soil moisture in the semi-arid loess hilly area, China

    OpenAIRE

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

    2012-01-01

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

  3. Cyclostratigraphy for Chinese red clay sequences: Implications to changing previous age models and paleoclimate interpretations

    Science.gov (United States)

    Anwar, T.; Kravchinsky, V. A.; Zhang, R.

    2015-12-01

    The Chinese Loess Plateau contains red clay sequence which has continuous alternation of sedimentary cycles with recurrent paleoclimatic fluctuations. Absence of abundant fossils and inability of radiometric dating method made magnetostratigraphy a leading method to build age model for the red clay. Here magnetostratigraphic age model in red clay sequence is tested using cyclostratigraphy as orbital parameters of Earth are known. Milankovitch periodicities recorded in magnetic susceptibility and grain size in the Shilou red clay section are investigated and previously found age of 11 Ma for this section is re-evaluated. Magnetostratigraphy dating based on only visual correlation could potentially lead to erroneous age model. In this study the correlation is executed through the iteration procedure until it is supported by cyclostratigraphy; i.e. Milankovitch cycles are resolved in the best possible manner. Our new approach provides an age of 5.2 Ma for the Shilou profile. Wavelet analysis reveals that a 400 kyr eccentricity cycle is well preserved and the existence of a 100 kyr eccentricity in the red clay sequence on the eastern Chinese Loess Plateau suggests that eccentricity plays a vital role in Pliocene climate evolution. Paleomonsoon evolution is reconstructed and divided into three intervals (5.2-4.5 Ma, 4.5-3.6 Ma and 3.6-2.58 Ma). The earliest stage indicates that summer and winter monsoon cycles may rapidly alter, whereas the middle stage reflects an intensification of winter monsoon and aridification in Asia, and the youngest stage is characterized by relatively intensified summer monsoon. This study demonstrates that cyclostratigraphy can greatly assist magnetostratigraphy in dating the red clay sequences, and implies that many published age models for the red clay sequences should likely be re-assessed where possible. An evaluation of the monsoon system and climate change in eastern Asia might prominently benefit from this approach.

  4. Vegetation filtering in gully region of loess plateau based on laser scanning point cloud’s intensity attenuation model and its terrain construct%黄土沟壑区切沟植被的激光点云滤波及地形构建

    Institute of Scientific and Technical Information of China (English)

    马鼎; 李斌兵

    2013-01-01

    The point cloud data of a gully region in loess plateau via Terrestrial Laser Scan (TLS) was characterized by uneven distribution of laser footprints, rapid geomorphologic change, and high density of herbaceous vegetation. In order to improve the precision of gully DEM, this paper proposes a vegetation filtering method of TLS point cloud. We first use laser return intensity to make an applicable classification.It is significant to compensate intensity attenuation which is brought by distance, angle of incidence, and environment, and establish a unified relationship between object and return light intensity. Available data indicates that return intensity is represented by an inverse second-order-dependent function of distance and other parameters can be treated as a constant in one experiment. We built a distance attenuation model of return light intensity. We can calculate the attenuation factor based on it and then compensate for laser return intensity of the whole point cloud. In this study, the return intensities of six sphere targets are used to build an attenuation model, and we obtained the attenuation factor as 0.3173. With the unified return intensity, each point’s intensity deviation with intensity of the ground was used as a weight to enlarge the difference of non-ground points and ground points. Then we used segmentation and surface fitting method to calculate each point’s distance to the trend surface, and set the threshold to separate the ground points and vegetation points. In this study, we propose an adaptive mesh grid filtering method integrated with return light intensity. In this method, we updated the distance to the trend surface though each point’s intensity weight which has a linear relationship with its intensity deviation. Besides, the adaptive segmentation is more fast and effective than the K neighborhood search method. The method’s reliability was tested through a point cloud acquired from a typical gully in Qiaozi Valley

  5. Paleoenvironmental changes recorded in a luminescence dated loess/paleosol sequence from the Tianshan Mountains, arid central Asia, since the Penultimate Glaciation

    Science.gov (United States)

    Li, Guoqiang; Rao, Zhiguo; Duan, Yanwu; Xia, Dunsheng; Wang, Leibin; Madsen, David B.; Jia, Jia; Wei, Haitao; Qiang, Mingrui; Chen, Jianhui; Chen, Fahu

    2016-08-01

    Mid-latitude arid central Asia (ACA) is one of the driest regions in the world and is a key source area of global atmospheric dust. Loess records of paleoclimatic changes in ACA are complex and interpretations are problematic due primarily to the lack of robust chronologies. Quartz OSL and K-feldspar pIRIR dating methods were employed to date 8 quartz and 30 K-feldspar samples from a 30 m loess sequence (BYH10 section) on the northern slope of the Tianshan Mountains, central ACA, northwest China. The reliability of quartz and K-feldspar ages was monitored by internal checks of luminescence characteristics and by comparison of the quartz and K-feldspar ages. The section lithology, proxy indexes of grain size and magnetic susceptibility, and the high resolution OSL chronology together indicate: (1) Quartz OSL dating can be used to date ACA loess samples less than 40 ka, while K-feldspar pIRIR dating is reliable for loess samples at least as old as ∼150 ka from ACA; (2) Aeolian loess began to be deposited on the northern slope of Tianshan Mountains beginning at least ∼145 ka ago, and was deposited primarily during the penultimate and last glaciation periods; (3) Rapid loess deposition occurred during MIS 6, MIS 4 to early-mid MIS 3, and MIS 2, but little or no loess deposition occurred during MIS 5, MIS 3a and MIS 1; (4) This loess depositional sequence is comparable to previously published stalagmite growth records in the region on glacial-interglacial cycles. Rapid dust deposition and lack of stalagmite growth during glacials, and lack of loess deposition and stalagmite growth during interglacials, indicate a climatic pattern of wet-warm (interglacial) and dry-cold (glacial) climatic regimes on orbital cycles in ACA; (5) Variation in the loess deposition rates in ACA was much larger than in the central loess plateau during the last glaciation; (6) Depositional hiatuses of >50 kyr occur in ACA loess sequences, and high resolution chronologies are needed when

  6. The Agh Band loess-palaeosol sequence in Northern Iran - a detailed archive for climate and environmental change during the last and penultimate glacial - interglacial cycles

    Science.gov (United States)

    Lauer, Tobias; Frechen, Manfred; Vlaminck, Stefan; Kehl, Martin; Sharifi, Jafar; Rolf, Christian; Khormali, Farhad

    2016-04-01

    The northern Iranian loess profiles host important information on quaternary climate and palaeoenvironmental changes in the region. Furthermore, they build an important link to correlate European and Central Asian archives. Due to a significant climatic gradient with decreasing precipitation from the west to the east and from the south to the north, loess-palaeosol sequences which were formed synchronously under different climatic conditions can be studied. The Agh Band profile is located in the so called Iranian "Loess Plateau", a semi-arid region with about 300 mm annual precipitation. The loess deposits reach a thickness of > 60 meters and are subdivided by several weak soil horizons in the more upper part and by a pedo-complex of 3 Bw(y) horizons in the lower part of the loess. The Agh Band profile was sampled in 2 cm intervals for multi-proxy analyses (e.g. magnetic susceptibility and grain size measurements). Furthermore, samples for palaeomangentic studies and luminescence dating were collected and a pIRIR290 approach was applied to fine-grain polyminerals. The results show that the Agh Band profile yields a climate archive reaching from MIS 7 to MIS 2. Several chronological hiatuses of some 10 ka show that periods of intense loess accumulation were interrupted by phases of only minor loess sedimentation and/or erosion. The Agh Band profile hosts an extraordinary good temporal resolution for MIS 4 and MIS 5. The pedocomplex at the bottom part of the profile indicates a period of increased humidity and landscape stability during late MIS 7 and MIS 6 following the luminescence ages. The loess-profile is also subdivided by several shifts in grain-size distribution. The coarsening- and fining up trends correlate with increasing and decreasing wind- velocity, respectively.

  7. Combined traditional Chinese and Western medicine intervention on postoperative rehabilitation after tibial plateau fracture surgery%中西医结合干预对胫骨平台骨折术后康复的影响

    Institute of Scientific and Technical Information of China (English)

    姚海英

    2016-01-01

    Objective To observe the effect of the combined traditional Chinese and Western medicine intervention on the postoperative rehabilitation after tibial plateau fracture surgery. Methods A total of 80 patients with tibial plat-eau fracture who were admitted in our hospital from May,2013 to November,2014 were included in the study and ran-domized into the experiment group and the control group with 40 cases in each group. After operation,the patients in the experiment group were given routine treatment,rehabilitation training,and in combined with the traditional Chinese and Western medicine intervention,while the patients in the control group were only given the routine treatment and rehabili-tation training. A 3-month follow-up visit was paid to the patients in the two groups. The fracture healing rate and the oc-currence rate of complications in the two groups were compared. Lysholm knee joint function evaluation system was used to asses the improvement of knee joint function. Results The occurrence rate of postoperative complications in the ex-periment group was significantly lower than that in the control group(P <0. 05). The fracture healing rate 3 months after operation in the experiment group was significantly higher than that in the control group(P <0. 05). The improvement of Lysholm knee joint function 3 months after operation in the experiment group was significantly superior to that in the control group(P <0. 05). Conclusions The combined traditional Chinese and Western medicine intervention can sig-nificantly reduce the occurrence rate of postoperative complications after tibial plateau fracture surgery,promote the frac-ture healing,and enhance the efficacy;therefore,it deserves to be widely recommended in the clinic.%目的:观察中西医结合干预疗法对胫骨平台骨折术后患者康复的影响。方法选取我院收治行切开复位内固定术治疗的胫骨平台骨折患者80例,术后随机分为实验组及对照组,各40

  8. Climate instability during the last glaciation recorded in the Yuanbu loess section

    Institute of Scientific and Technical Information of China (English)

    Yimeng Chen

    2009-01-01

    Abrupt events within the Linxia Yuanbu loess section in the western Loess Plateau in China were investigated.The climatic proxy index of the content of mean grain-size and>4 μm grain-size fraction of the section was used as a climatic indicator,and a moving average method was applied in the statistical analysis to extract the abrupt events recorded in the section.It was found that the loess of the last glaciation recorded not only the abrupt events teleconnected with the high-latitude North Atlantic and Greenland regions but also as many as 15 abrupt events in addition to the Heinrich (H) and Younger Dryas (YD) events.This indicates that abrupt climate changes were typical of the climate changes occurring in the Loess Plateau during the last glaciation.The widely recognized mechanisms of the abrupt climate changes,including the heat transfer theory of the North Atlantic Ocean,the atmospheric circulation theory,and the theory of the interaction between low-latitude ocean and the atmosphere remains to be discussed.Perhaps this problem could be resolved by revealing the relation between the evolution of the features of the East Asian monsoon climate and the climate in the surrounding areas.Through a detailed study of the features of the Heinrich and YD events,criteria on which the abrupt events recorded in the loess could be distinguished were tentatively defined.The events were associated with a large grain size,high carbonate content,high lightness,low susceptibility,low redness and low yellowness.In addition,the variation amplitude of the adjacent peak and valley on the curve of the content of the mean grain-size and>40μm grain-size fraction was larger than 3.4μm and the content of >40μm grain-size fraction was larger than 2.0μm.Lastly,the length of the variation time was less than 500 years.If all these criteria were met,the event was viewed as an abrupt event.

  9. Geochemical investigation of dry- and wet-deposited dust during the same dust-storm event in Harbin, China: Constraint on provenance and implications for formation of aeolian loess

    Science.gov (United States)

    Xie, Yuanyun; Chi, Yunping

    2016-04-01

    A strong dust-storm event occurred in Harbin, China on May 11, 2011. The dry- and wet-deposited dust depositions in this dust-storm event, together with the surface sediments from the potential sources, were collected to study grain size distributions, carbonate content and carbon isotopic composition of carbonate, major element, trace element and rare earth elements (REE), and Sr-Nd isotopic compositions. The results indicate as follows. The dry-deposited dusts are characterized by bimodal grain-size distributions with a fine mode at 3.6 μm and a coarse mode at 28 μm whereas the wet-deposited dusts are indicative of unimodal grain-size modes with a fine mode at 6 μm. The dust-storm depositions are influenced to a certain extent by sedimentary sorting and are of a derivation from the recycled sediments. Based on identifying the immobility of element pairs before constraining sources of dust-storm deposits using geochemical elements, in conjunction with REE and especially Sr-Nd isotopic compositions, the primary and strengthening sources for the dust-storm event were detected, respectively. The Hunsandake Sandy Land as the primary source and the Horqin Sandy Land as the strengthening source were together responsible for the derivation of dust depositions during dust-storm event. The Hunsandake Sandy Land, however, contributes less dust to the dust-storm event in Harbin compared to the Horqin Sandy Land, and the Hulun Buir Sandy Land is undoubtedly excluded from being one of the sources for dust-storm depositions in Harbin. There are not notable differences in geochemical (especially Sr-Nd isotopic) compositions between dry- and wet-deposited dusts, indicating that the wet-deposited dust is of identical derivation to the dry-deposited dust. Based on our observations, it is of interest to suggest that fine and coarse particles in the CLP (Chinese Loess Plateau) loess possibly have the same sources.

  10. The rock magnetic characteristics of last glacial cycle loess from the island of Susak (Adriatic Sea, Croatia)

    Science.gov (United States)

    Hambach, Ulrich; Duchoslav, Maguerita; Rolf, Christian; Wacha, Lara; Frechen, Manfred; Galovic, Lidija

    2010-05-01

    Loess is by far the most important terrestrial archive that provides detailed palaeoclimatic information for the whole Quaternary. Loess covers wide areas in Asia and Southeast Europe where continental and sub-continental climates predominate. In Mediterranean climate settings, however, loess deposits are almost absent and the few existing sites provide invaluable palaeoclimatic information. Heller & Liu (1984) were the first who used magnetic susceptibility variations in Chinese loess to correlate the loess deposits to marine records. The susceptibility variations in the loess-palaeosol couplets resemble the pattern of the global ice volume record with higher values in palaeosols (interglacials) and lower values in loess (glacials). In most parts of the Eurasian loess belt, the intensity of pedogenesis leads to enhancement of magnetic minerals in soils. However, in other parts of the world under different climatic conditions, even depletion of the magnetic fraction could be observed. Furthermore, the wind strength during dust transport and loess deposition also seems to control the magnetic mineralogy. With stronger winds, minerals with higher density such as iron oxides are enriched during aeolian transport. Here we report on first results from a detailed rock magnetic investigation of a loess sequence from the Adriatic coast of Croatia. The Pjeskokop site is located on the island of Susak in the northern Dalmatian archipelago. On Susak, aeolian sands, sandy loess and loess have been deposited on Cretaceous marine limestones and form an up to 20 metres thick Pleistocene sediment blanket (Cremaschi 1990). At the Pjeskokop site, non-oriented samples were collected with narrow spacing (~2 cm) from a more than 11 metres high section. All samples were subjected to standard rock laboratory procedures. Detailed petrographical and grain size studies on parallel samples are in progress. A strongly rubified pedo-complex forms the base of the sequence. Weakly developed

  11. Properties of Bentonite Enhanced Loess and Laterite

    Institute of Scientific and Technical Information of China (English)

    刘阳生; 白庆中; 聂永丰

    2004-01-01

    Loess and laterite distributed widely in the northern and southern China cannot be directly used as the natural barrier to isolate the solid waste because of their high hydraulic conductivity. In this paper, they are enhanced by bentonite to improve their hydraulic performance. The impact of bentonite content and water content on compressive strength of the compacted soil was investigated. The effects of bentonite content, water content, dry density and hydraulic gradient on the hydraulic conductivity were studied in detail. For the laterite and the laterite with 8% of bentonite, the experimental results of hydraulic conductivity can be applied in the engineering design. However, for the loess and the bentonite enhanced loess, those of hydraulic conductivity can not be directly applied in the engineering design because their hydraulic performance does not comply with the Darcy's law. These experimental results have to be carefully modified before application.

  12. Landslide disaster in the loess area of China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    China is the country with most widely distributed loess area in the world, and its loess area accounts of 6.63% of total nation land area. The landslide disaster occurs frequently for complex natural condition and becomes major factors hindering the social and economic development of loess regions. Through different indexes, the authors divided the landslides into 9 principal types and analyzed the distribution characteristics of loess landslide in time and space, the affecting factors and mechanism of landslides. It is pointed out that time and spatial distributions of landslides are closely correlative to topographic and geomorphic conditions, earthquake and rainfall, and the key influencing factors include topography, geomorphology, new tectonic movements, earthquake activity, surface water, ground water and human activities. The authors emphasized that the natural condition of loess areas was favorable to landslides, human activities impelled its occurrence and that controlling the loess landslide was an urgent task for sustainable development in the loess zone.

  13. The effect of repeated small doses of radiation on recovery from sublethal damage by Chinese hamster cells irradiated in oxic or hypoxic conditions in the plateau phase of growth

    International Nuclear Information System (INIS)

    Unfed plateau phase Chinese hamster cells have been irradiated with either single doses or up to ten fractions of x-rays six hours apart. These cells remained in an extended G1-like phase throughout the irradiation period. The single-dose log survival curve had an extrapolation number of about 9 and the oxygen enhancement ratio was three. Cells were exposed either to 200 rad per fraction in air and 600 rad per fraction in hypoxia (during irradiation only), or 150 rad per fraction in air and 450 rad per fraction in hypoxia. The resulting fractionated log survival curves did not fit a multitarget model of cell survival, being much steeper than that would predict. The addition of a single-hit component to the lethal effect of the radiation gave reasonable agreement for the first five fractions although the curves tended to bend downwards with increasing number of fractions. The log survival curve for cells irradiated with five fractions of 200 rad (or 600 rad in hypoxia) six hours apart and graded doses six hours after the fifth fraction had an extrapolation number much less than that following single doses, implying a decreased ability to absorb radiation damage as sublethal. The ratio of the initial slopes of the fractionated log survival curves for irradiation in air and hypoxia was less than three, implying that the oxygen enhancement ratio on the shoulder may be less than that in the exponential region of survival. (author)

  14. The effect of repeated small doses of radiation on recovery from sub-lethal damage by Chinese Hamster cells irradiated in the plateau phase of growth

    International Nuclear Information System (INIS)

    Unfed plateau-phase cells have been irradiated with either single doses or up to ten fractions of X-rays 6 hours apart. The single-dose survival curve had an extrapolation number of 11.4, and the oxygen-enhancement ratio (o.e.r.) was 3.1. Cells were exposed to multiple fractions of 200 rad or 150 rad in air and 600 rad or 450 rad in hypoxia. The resulting survival curves did not fit a multi-target, single-hit model of cell survival, being much steeper than that would predict. The curves were exponential up to five fractions of X-rays, but tended to bend downwards with increasing number of fractions. Cells that had survived five fractions of 200 rad (or 600 rad in hypoxia) 6 hours apart, were less able to absorb damage as sub-lethal than those which had not previously been exposed to radiation. The ratio of the initial slopes of the fractionated survival curves for irradiation in air and hypoxia was 2.1, implying that the o.e.r. 'on the shoulder' may be less than that in the exponential region of survival. (author)

  15. Development of Dense Time Series 30-m Image Products from the Chinese HJ-1A/B Constellation: A Case Study in Zoige Plateau, China

    Directory of Open Access Journals (Sweden)

    Jinhu Bian

    2015-12-01

    Full Text Available Time series remote sensing products with both fine spatial and dense temporal resolutions are urgently needed for many earth system studies. The development of small satellite constellations with identical sensors affords novel opportunities to provide such kind of earth observations. In this paper, a new dense time series 30-m image product was proposed respectively based on an 8-day, 16-day and monthly composition. The products were composited by the Charge Coupled Device (CCD images from the 2-day revisit small satellite constellation for environmental monitoring and disaster mitigation of China (HJ-1A/B. Taking the Zoige plateau in China as a case area where it is covered by highly heterogeneous vegetation landscapes, a detailed methodology was introduced on how to use 183 scenes of CCD images in 2010 to create composite products. The quality of the HJ CCD composites was evaluated by inter-comparison with the monthly 30-m global Web-Enabled Landsat Data (WELD, 16-day 500-m MODIS NDVI, and 8-day 500-m MODIS surface reflectance products. Results showed that the radiometric consistency between HJ and WELD composited Top Of Atmosphere (TOA reflectance was in good agreement except for May, June, July and August when more clouds and invalid data gaps appeared in WELD. Visual assessment and temporal profile analysis also revealed that HJ possessed better visual effects and temporal coherence than that of WELD. The comparison between HJ and MODIS products indicated that HJ composites were radiometrically consistent with MODIS products over areas consisting of large patches of homogeneous surface types, but can better reflect the detailed spatial differences in regions with heterogeneous landscapes. This paper highlights the potential of compositing HJ-1A/B CCD images, allowing for providing a cloud free, time-space consistent, 30-m spatial resolution, and dense in time series image product. Meanwhile, the proposed products could also be treated as a

  16. On the applicability of post-IR IRSL dating to Japanese loess

    DEFF Research Database (Denmark)

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

    2011-01-01

    Recent work on infrared stimulated luminescence (IRSL) dating has focussed on finding and testing signals which show less or negligible fading. IRSL signals measured at elevated temperature following IR stimulation at 50°C (post-IR IRSL) have been shown to be much more stable than the low...... temperature IRSL signal and seem to have considerable potential for dating. For Early Pleistocene samples of both European and Chinese loess natural post-IR IRSL signals lying in the saturation region of the laboratory dose response curve have been observed; this suggests that there is no significant fading...

  17. “巫山黄土”的稀土元素特征与成因%REE Compositions of the "Wushan Loess" and Its Origin

    Institute of Scientific and Technical Information of China (English)

    张玉芬; 李长安; 邵磊; 周耀; 刘引迪

    2013-01-01

    为了探讨“巫山黄土”的成因,对剖面样品进行了稀土元素含量、稀土分布模式和稀土特征值计算分析.结果表明:“巫山黄土”稀土元素特征与现代河流沉积物差别明显,而与北方黄土及长江中下游的下蜀土却基本一致.稀土分布模式与典型风尘沉积物相似,物源判别函数得到的物源指数(PD均与风积黄土的最为接近,显示其风积成因的特点.“巫山黄土”稀土元素平均含量216.39×10-6高于地壳平均值178.0×10-6和两块中国黄土标样平均值178.22×10-6,但与长江中下游镇江下蜀土样品的平均值207.7×10-6比较接近.样品的轻稀土较富集,重稀土略有淋失,轻重稀土比值为8.62,Eu呈较明显的负异常,Ce异常不明显.表明“巫山黄土”风尘沉积后经历了较北方黄土更为强烈的风化作用,其形成环境与下蜀土比较接近.%The rare earth element (REE) compositions of the "Wushan Loess" are studied in order to encipher information on the genesis of the "Wushan Loess". The REE patterns, concentrations and indices are used for the discussion. The results show that REE compositions of the "Wushan Loess" are quite different from those of the modern river sediments and similar to those of the Loess Plateau and the "Xiashu Loess" in the middle and lower Yangtze reaches. REE distribution patterns are similar to those of the typical eolian deposits. The index (PI) calculated by source discriminant function is similar to those of the e-olian deposits, indicating the eolian origin. The average REE content (216. 39×10-6) is significantly higher to the average rate of the earth crust (178. 0×10-6), two samples from the Loess Plateau (178. 22×10-6), and fairly close to the average rate of the samples from the Xiashu loess in the middle and lower Yangtze reaches (207. 7 ×10-6). The light rare earth element (LREE) are relatively enriched, while the heavy rear earth element (HREE) are slightly missing. The

  18. Life strategies of bryophytes on loess cliffs in Vojvodina, Serbia

    Directory of Open Access Journals (Sweden)

    Sabovljević Marko S.

    2004-01-01

    Full Text Available The loess cliffs of Vojvodina present a special ecosystem type. The main plant components in these habitats are cryptogams (bryophytes and lichens. The biology and life strategies of bryophytes recorded on loess in Vojvodina are studied in the present work, whose results confirm a very special ecology in such habitats. Colonist species with xeropottioid characteristics are dominant among bryophytes. It is stressed that loess cliff habitats are especially important from the standpoint of conservation.

  19. Spatial Variability of Soil Saturated Hydraulic Conductivity in a Small Watershed of Loess Hilly Region,China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Saturated hydraulic conductivity (Ks) is an important soil hydraulic parameter for charactering the rate of water flow across the soils and is mainly related to its high spatial variability. In a small watershed with the area of 0.27 km2 in the Loess Plateau, Ks of 197 soil samples under different vegetations and landforms were measured. Ks had a moderate variability for total samples. The forestland had high Ks with low coefficient of variation (CV), but the grassland in the watershed bottom had low Ks wit...

  20. On the Chinese People's Aesthetics

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    正Appreciation of art is not a birthright. In the prehistoric primitive society, the ancestors of the Chinese people rooted in the harsh natural environment of the Yellow River Basin and began forging their own solid characteristics as the loess and rock. Our ancestors survived in the harsh natural conditions. Pressure of keeping alive deprived of their original romantic, despite that Neolithic primitive rock art, pottery painting

  1. Spatio-Temporal Patterns of Cropland Conversion in Response to the “Grain for Green Project” in China’s Loess Hilly Region of Yanchuan County

    Directory of Open Access Journals (Sweden)

    Jieyong Wang

    2013-10-01

    Full Text Available To prevent environmental degradation, China’s central government launched the “Grain for Green Project” (GGP in 1999. Since its beginning, the effects and influences of the GGP have been hotly debated among domestic and international scholars and policymakers. This paper is taking the County of Yanchuan in the Loess Plateau as a case study, examines the spatio-temporal patterns of cropland conversion in response to the GGP. This research is methodologically based on remote sensing (RS and geographic information systems (GIS, and also employs personal interviews with local government officials and farmers. The results show that land use/cover patterns in Yanchuan County have changed dramatically after the implementation of GGP. Cropland has decreased remarkably, while orchard land and sparse forest has increased significantly: 23.84% of cropland was converted to orchard, and 22.25% to sparse forest. Simultaneously, the landscape has become more fragmented but also more diversified, forestland has become more dominant. A total of 61.19% of the total converted cropland was on slopes greater than 15 degrees, 64.85% of which was lower-grade land. The converted cropland is mostly located in more accessible areas for convenient management. Partially affected by farmers’ self-willingness, sloping cropland was preferred to orchard (economic forest, and some gentle slope (less than 15 degrees or higher-grade cropland were involved in the GGP. To maintain and reinforce the achievements of the GGP and further contribute to the GGP’s sustainability and rural development, the paper recommends that the Chinese government should build a continuous compensation mechanism for the households who lost cropland for the GGP while improving the productivity of flat cropland.

  2. Point Cloud Oriented Shoulder Line Extraction in Loess Hilly Area

    Science.gov (United States)

    Min, Li; Xin, Yang; Liyang, Xiong

    2016-06-01

    Shoulder line is the significant line in hilly area of Loess Plateau in China, dividing the surface into positive and negative terrain (P-N terrains). Due to the point cloud vegetation removal methods of P-N terrains are different, there is an imperative need for shoulder line extraction. In this paper, we proposed an automatic shoulder line extraction method based on point cloud. The workflow is as below: (i) ground points were selected by using a grid filter in order to remove most of noisy points. (ii) Based on DEM interpolated by those ground points, slope was mapped and classified into two classes (P-N terrains), using Natural Break Classified method. (iii) The common boundary between two slopes is extracted as shoulder line candidate. (iv) Adjust the filter gird size and repeat step i-iii until the shoulder line candidate matches its real location. (v) Generate shoulder line of the whole area. Test area locates in Madigou, Jingbian County of Shaanxi Province, China. A total of 600 million points are acquired in the test area of 0.23km2, using Riegl VZ400 3D Laser Scanner in August 2014. Due to the limit Granted computing performance, the test area is divided into 60 blocks and 13 of them around the shoulder line were selected for filter grid size optimizing. The experiment result shows that the optimal filter grid size varies in diverse sample area, and a power function relation exists between filter grid size and point density. The optimal grid size was determined by above relation and shoulder lines of 60 blocks were then extracted. Comparing with the manual interpretation results, the accuracy of the whole result reaches 85%. This method can be applied to shoulder line extraction in hilly area, which is crucial for point cloud denoising and high accuracy DEM generation.

  3. The last 850 millennia recorded at the Stari Slankamen loess-paleosol sequence: revised chronostratigraphy and long-term environmental trends

    Science.gov (United States)

    Markovic, S. B.; Hambach, U.; Machalett, B.; Stevens, T.; Kukla, G. J.; Heller, F.; Ouches, E. A.; McCoy, W. D.; Buggle, B.; Zoeller, L.; Basarin, B.; Milojkovic, N.; Lukic, T.

    2008-12-01

    The Stari Slankamen loess section is located on the northeastern part of the Srem Loess Plateau (Vojvodina region, North Serbia) on the west bank of the Danube River opposite the Tisa (Tisza) confluence. The ca. 40-m thick cliff is comprised of loess intercalated with 7 major paleo-pedocomplexes and can be considered to be one of the most significant, nearly continuous, Quaternary sections in the Carpathian (Panonnian) Basin area. Here we present magnetostratigraphic and aminostratigraphic evidence that further emphasizes the importance of the site in terms of its age and the long-term paleoclimatic record it preserves. Characteristic remnant magnetization, obtained through alternating field demagnetization, was obtained on 59 oriented samples and demonstrates the presence of the Matuyama-Brunhes boundary (MBB) at a profile depth of 36 m, within loess unit V-L7. This interpretation is confirmed by new high resolution paleomagnetic investigations (434 oriented samples) from the lower of the profile. Low frequency field magnetic susceptibility was measured in situ in the lower 20 m of the exposure and in the laboratory on samples taken from the upper 20 m of the loess-paleosol sequence. As a record of pedogenic alteration, the magnetic susceptibility (MS) record provides a mean of correlating the sequence with key loess sites in Central and Southeastern Europe, China, and with key climate archives such as the marine oxygen-isotope record. The MS records and evidence from amino acid geochronology measurements indicate a missing pedocomlex (V-S2), the result of an erosion event represented by distinct layer overlying an erosion unconformity. In addition, the magnetostratigraphic and aminostratigraphic based age model requires a significant revision of hitherto published chronostratigraphic subdivisions of the sequence. Our revised chronostratigraphic model suggests that previous age estimates, including results of previous thermoluminescence dating, need to be

  4. Determination of organophosphorus pesticide residues in main Chinese herbal medicines in Qinghai Plateau%青海高原主要中药材中有机磷类农药残留的测定

    Institute of Scientific and Technical Information of China (English)

    韩澄华; 崔鹏

    2012-01-01

    Objective To establish a capillary gas chromatography method to determinate the 10 kinds of organophosphorus pesticide residues in Chinese herbal medicines in Qinghai plateau. Method The samples were extracted by acetonitrile ultrasonic, dehydrated by anhydrous sodium sulfate, purified by graphitized carbon ( CARB) / amino (NH2) solid - phase extraction column after concentration, determined constant volum by acetone, separated by DB - 7 capillary column, and determined the nature and quantification by FPD detector. Results These 10 kinds of organophosphorus pesticides presented better linear relation in a concentration range of 0. 10 ~ 1.0g/ml. The lowest detection limit of this method was between 0. 0058 mg/kg and 0. 060 mg/kg. The additive amount of mixed standard solution of these 10 organophosphorus was 0. 5mg/kg. It had measured parallelly for 6 times. The average recovery rate was between 67. 1% and 120. 0% , and the relative standard deviation was between 2. 9% and 5. 7%. Conclusion This method had high sensitivity, accuracy and repeatability, which was suitable for the measurement of 10 kinds of organophosphorus pesticides residues in Chinese herbal medicine in basic units.%目的 建立毛细管气相色谱法测定青海高原中药材中10种有机磷农药残留的分析方法.方法 样品经乙腈超声提取,无水硫酸钠脱水,浓缩后经石墨化碳( CARB)/氨基(NH2)串联固相萃取柱提纯净化,丙酮定容,采用DB -7毛细管柱分离,FPD检测器定性定量.结果 10种有机磷农药在0.10~1.0μg/mL的浓度范围内呈较好的线性关系,该方法的最低检出限为0.0 058~0.060mg/kg.10种有机磷混合标准溶液添加量为0.5mg/kg,平行测定6次,平均回收率为67.1%~ 120.0%,相对标准偏差为2.9%~5.7%.结论 该方法具有较高灵敏度、准确、重现性好等优点,适于中药材中10种有机磷类农药残留在基层单位的测定.

  5. Iodine sorption on loess and clay samples

    International Nuclear Information System (INIS)

    Sorption batch experiments were performed to evaluate the ability of Saligny geologic formations to retard the main radionuclides that could be released from the disposal facility by dissolution/leaching processes. This paper presents the results obtained for iodine, one of the long-lived radionuclides present in the radioactive waste generated from Cernavoda NPP operation and decommissioning. Experimental results suggest that loess and clay samples present in Saligny site can not retard significantly the iodine transport and this radionuclide will be transported at velocities as similar to those in case of the ground water. (authors)

  6. The environmental magnetic fingerprint of periglacial loess in Eastern Germany

    Science.gov (United States)

    Baumgart, Philipp; Hambach, Ulrich; Meszner, Sascha; Faust, Dominik

    2013-04-01

    In the framework of a comprehensive stratigraphic study of loess Eastern Germany, a detailed rock magnetic study was carried out of four last glacial/interglacial loess-palaeosol sequences. Magnetic susceptibility and laboratory-induced remanences have been determined to compare individual sections and to identify the specific rock magnetic characteristics of the Saxonian Loess Province. According to the model of pedogenic magnetic enhancement, an increasing neoformation of ferrimagnetic minerals in the course of pedogenesis was observed only in the uppermost Late Weichselian lithological units consisting of almost unweathered loess and indicating dryer climatic conditions. In contrast, the rock magnetic characteristics of the lower Middle and Early Weichselian units exhibit a significant destruction of primary magnetic minerals caused by such secondary processes as climatically controlled waterlogging and reworking. The main observation, an increasing ?fd with decreasing ? with stratigraphic depth, argues for a general magnetic depletion in conjunction with decreasing magnetic grain sizes caused by weathering of larger primary particles. The magnetic fingerprint of the Saxonian loess is characterised by prevailing magnetic depletion processes, which effectively rules out the application of the wind vigour model. Moreover, the observed magnetic characteristics differ significantly from that of other loess regions. Therefore, we propose a new magnetic facies model for more humid (Central European) loess provinces dominated by typical periglacial conditions, including widespread permafrost, which control the intense reworking and waterlogging (gleyification) processes.

  7. Thermoluminescence and new 14C age estimates for late quaternary loesses in southwestern Nebraska

    Science.gov (United States)

    Maat, P.B.; Johnson, W.C.

    1996-01-01

    Loess of late Quaternary age mantles most of Nebraska south of the Platte River Valley. At least five late Quaternary loesses are recognized: from oldest to youngest, one or more undifferentiated pre-lllinoian loesses, the Loveland Loess, the Gilman Canyon Loess, which exhibits a well developed soil and rests unconformably on the Sangamon soil, the Peoria Loess capped by the Brady soil, and the Bignell Loess, which is distributed discontinuously. Previous research shows that the Loveland Loess is Illinoian. the Gilman Canyon Loess and Peoria Loess are Wisconsin, and the Bignell Loess is Holocene. We present here the first thermoluminescence (TL) age estimates and new C ages for these late Quaternary loesses at two key sections in southwestern Nebraska, the Eustis ash pit and the Bignell Hill road cut. TL age estimates from all samples collected from Eustis ash pit and Bignell Hill were internally consistent. TL and C age estimates from these two sections generally agree and support previous age determinations. The TL age estimate on Loveland Loess indicates deposition at 163 ka. TL and radiocarbon age estimates indicate that Oilman Canyon Loess, believed to be deposited during the Farmdale interstade, first began to accumulate at about 40 ka: the lower part of the Gilman Canyon Loess is 36 ka at Eustis and the middle of the unit is 30 ka at Bignell Hill. The lower and upper parts of the Peoria Loess give age estimates of 24 ka and 17 ka, respectively. TL age estimates for deposition of the Bignell Loess are 9 ka near the base, in agreement with radiocarbon age estimates, and 6 ka immediately below the modern soil, substantiating its Holocene age. Comparisons of TL age estimates with ??18O and insolation curves which show loess deposition during interglacial and interstadial as well as glacial periods, indicate that loess deposition on the Great Plains can occur under a variety of climatic conditions.

  8. Optical dating: bleaching experiment on IRSL signals from loess samples

    International Nuclear Information System (INIS)

    A kind of red LEDs (Light emitting Diode) with a wavelength of 655 nm provides light illumination of loess samples while pretreatment the samples with minimal effect on the latent IRSL. The IRSL signal is decreased to two percent after 20 minutes bleaching by sun light. It implies that the residual signals may be neglected even when dating very young loess samples, and that IRSL dating has significant potential in dating very poorly-bleached sediments. The recuperation of IRSL in loess is negligible, so the measurable age limit for IRSL is much lower than that for GLSL (Gree Light Stimulate Luminescence)

  9. Geotechnical problems related with loess deposits in Northern France

    CERN Document Server

    Delage, Pierre; Antoine, Pierre

    2008-01-01

    Special problems were encountered in some areas in Northern France where the high speed railways (TGV Nord) crossed some loess deposits that appeared to be specially sensitive to change in water content and susceptible to collapse. Numerous sinkholes appeared along some sections of the line following wet climatic periods. After a general geological and geotechnical presentation of loess deposits and collapse susceptibility, in which some tools of the mechanics of unsaturated soils are reconsidered with special application to loess collapsibility, this paper describes the results of a geotechnical study carried out on block samples of intact loess. Collapse susceptibility is examined in the light of microstructure observation. The dependence of collapse to water content changes is examined and the validity of various existing collapse criteria is investigated.

  10. Improved provenance tracing of Asian dust sources using rare earth elements and selected trace elements for palaeomonsoon studies on the eastern Tibetan Plateau

    Science.gov (United States)

    Ferrat, Marion; Weiss, Dominik J.; Strekopytov, Stanislav; Dong, Shuofei; Chen, Hongyun; Najorka, Jens; Sun, Youbin; Gupta, Sanjeev; Tada, Ryuji; Sinha, Rajiv

    2011-11-01

    The Asian Monsoon forms an important part of the earth's climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace elemental (Sc, Y, Th and the rare earth elements) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai-Tibetan Plateau) dust sources. Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle

  11. 中药薰洗湿热敷对胫骨平台骨折术后恢复的效果观察%Observation of the effect of the fumigation and wet hot compress of traditional Chinese medicines on the postoperative recovery of tibial plateau fracture

    Institute of Scientific and Technical Information of China (English)

    芦盛贞; 彭夏红

    2014-01-01

    Objective:To investigate the effect of the fumigation and wet hot compress of traditional Chinese medicines in combination with rehabilitation training on the postoperative functional recovery of knee joint after the fracture of tibial plateau.Methods: Eighty-six cases of patients with operation of tibial plateau fracture were randomly divided into a treatment group and a control group with 42 cases each. The fumigation and wet hot compress of traditional Chinese medicines were performed in the treatment group besides the conventional treatment and early rehabilitation after operation.Results: The incidence of knee joint pain and knee swelling was obviously lower in the treatment group than in the control group (P<0.05) and Hohl score of knee joint function was signiifcantly higher in the treatment group than in the control group in iffth weeks (P<0.05). Conclusion: The fumigation and wet hot compress of traditional Chinese medicines in combination with early rehabilitation training can promote the recovery of knee joint function after operation of tibial plateau fracture with signiifcant clinical effect.%目的:探讨中药薰洗加湿热敷配合康复训练对胫骨平台骨折手术后膝关节功能恢复的影响。方法:选择2010-2014年6月本院胫骨平台骨折手术患者84例,随机分为治疗组和对照组各42例。两组均给予术后常规治疗及早期康复训练,治疗组加用中药熏洗和湿热敷;评价中药熏洗和湿热敷对局部疼痛、肿胀、膝关节功能的影响。结果:治疗组患者膝关节疼痛和局部肿胀程度明显低于对照组(P<0.05);Hohls膝关节功能评分治疗组明显高于对照组(P<0.05)。结论:中药薰洗及湿热敷配合早期康复训练对胫骨平台骨折术后肿胀的消退、疼痛的减轻及膝关节功能恢复有明显疗效,便于推广和应用。

  12. CENTRAL PLATEAU REMEDIATION

    Energy Technology Data Exchange (ETDEWEB)

    ROMINE, L.D.

    2006-02-01

    A systematic approach to closure planning is being implemented at the Hanford Site's Central Plateau to help achieve the goal of closure by the year 2035. The overall objective of Central Plateau remediation is to protect human health and the environment from the significant quantity of contaminated material that resulted from decades of plutonium production in support of the nation's defense. This goal will be achieved either by removing contaminants or placing the residual contaminated materials in a secure configuration that minimizes further migration to the groundwater and reduces the potential for inadvertent intrusion into contaminated sites. The approach to Central Plateau cleanup used three key concepts--closure zones, closure elements, and closure process steps--to create an organized picture of actions required to complete remediation. These actions were merged with logic ties, constraints, and required resources to produce an integrated time-phased schedule and cost profile for Central Plateau closure. Programmatic risks associated with implementation of Central Plateau closure were identified and analyzed. Actions to mitigate the most significant risks are underway while high priority remediation projects continue to make progress.

  13. CENTRAL PLATEAU REMEDIATION

    International Nuclear Information System (INIS)

    A systematic approach to closure planning is being implemented at the Hanford Site's Central Plateau to help achieve the goal of closure by the year 2035. The overall objective of Central Plateau remediation is to protect human health and the environment from the significant quantity of contaminated material that resulted from decades of plutonium production in support of the nation's defense. This goal will be achieved either by removing contaminants or placing the residual contaminated materials in a secure configuration that minimizes further migration to the groundwater and reduces the potential for inadvertent intrusion into contaminated sites. The approach to Central Plateau cleanup used three key concepts--closure zones, closure elements, and closure process steps--to create an organized picture of actions required to complete remediation. These actions were merged with logic ties, constraints, and required resources to produce an integrated time-phased schedule and cost profile for Central Plateau closure. Programmatic risks associated with implementation of Central Plateau closure were identified and analyzed. Actions to mitigate the most significant risks are underway while high priority remediation projects continue to make progress

  14. Tibial Plateau Fractures

    DEFF Research Database (Denmark)

    Elsøe, Rasmus

    This PhD thesis reported an incidence of tibial plateau fractures of 10.3/100,000/year in a complete Danish regional population. The results reported that patients treated for a lateral tibial plateau fracture with bone tamp reduction and percutaneous screw fixation achieved a satisfactory level of...... radiological outcomes and a level of health related quality of life (Eq5d) below but not significantly different from the Danish reference population at a mean of 5.2 years follow-up. Furthermore, a knee injury-specific questionnaire (KOOS) reported a level of disability close to a reference population with...... only the subgroup Sport significantly below the age matched reference population. The thesis reports a level of health related quality of life (Eq5d) and disability (KOOS) significantly below established reference populations for patients with bicondylar tibial plateau fracture treated with a ring...

  15. Factors affecting transpiration of Pinus tabulaeformis in a semi-arid region of the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effects of soil water and meteorological factors affecting transpiration of Pinus tabulaeformis were studied under different levels of soil water content to offer a scientific basis for increasing efforts in afforestation survival and management of soil water in forested land.Under artificial control methods for soil water and potting experiments,the transpiration rate (Tr) of P.tabulaeformis and environmental factors were measured using a portable steady porometer (Li-1600) and a speedy weight method (BP-3400) during a representative fine day in the growing season of 2004.The results indicated that the diurnal course of Tr and Rst of P.tabulaeformis displayed a double-peaked curve and a "W" curve under different levels of soil water content.Given a representative fine day,the Tr could be represented as a cubic relation with soil water content (SWC).The SWC which caused maximum Tr values of P.tabulaeformis was 17.7%,19.8%,and 17.5% in July,August and October respectively.Tr was affected not only by physiological characteristics,but also by SWC and meteorological factors.Tr was significantly correlated with meteorological factors when the soil water was sufficient,but this correlation would decrease under conditions of serious water stress.Under such stress conditions,air temperature was the primary factor to affect Tr in July and August and photosynthetically active radiation (PAR) was the primary factor in October.When soil water is sufficient,the main factors affecting Tr were relative humidity (RH),air temperature (Ta) and leaf temperature (T1) in July,August and October respectively.

  16. Erosion environment in the sediment-rich area on the Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on the investigation and analysis of characteristics of precipitation, natural environment, socio-economic factors and soil erosion, this paper indicates that the precipitation is the main driving force for the soil erosion in the sediment-rich area, its variability determines the characteristics of soil and water loss; the natural conditions such as the drainage systems, geological and topographic features, the composition of soil and land surface materials, vegetation and climate determine the seriousness of soil and water loss; irrational socio-economic activities of human beings usually accelerated soil and water loss; meanwhile, the low preservation rate and inferiority of soil and water conservation measures made it impossible to make rapid progress on soil and water loss control. Furthermore, the characteristics of erosion environment endowed this area with more sediment that is the main reason for the flooding disasters by the Yellow River. Therefore, more emphasis should be placed on the enhancement of soil and water conservation. The soil loss prediction models will provide scientific basis for the planning of soil and water conservation, the designing of soil and water conservation measures and the valuation of effects of soil and water loss control. According to the analysis of the previous studies on soil loss prediction, and the water-sediment variation features, it is thought that study on soil loss prediction under various rainfall conditions and soil-water conservation measures should be carried out.

  17. Relationship of nitrate isotopic character to population density in the Loess Plateau of Northwest China

    International Nuclear Information System (INIS)

    Highlights: • Investigated nitrate isotopic composition in Xi’an. • δ15N–NO3- enrich process is mainly caused by the anthropogenic activity. • δ15N–NO3- value useful for tracing nitrate source. • δ15N–NO3- value and population density show a significant logarithmic correlation. - Abstract: Nitrate pollution of groundwater is an increasingly serious anthropogenic problem. In this study, the hydrogeochemistry of major ions and stable isotope ratios of NO3- in groundwater were determined to identify the contamination sources and chemical transformation processes occurring in the shallow groundwater of Xi’an, the capital of Shaanxi province, NW China. Of a total of 32 groundwater samples, 31% had NO3-–N concentrations exceeding the accepted drinking water limit of 10 mg-N L−1. Most of these samples were from the urban center of the study area, while samples with <10 mg-N L−1 were mainly from suburban areas. Combined with information on NO3- and Cl−, the variation in isotopes of NO3- in the groundwater suggest a mixing of multiple NO3- sources in areas on the urban/suburban border. By determining rainwater and river water NO3- isotopic values, the groundwater recharge mode can be deduced for Xi’an city. Chemical fertilizers and nitrification of N-containing organic materials contribute NO3- to suburban groundwater, while sewage effluent and nitrification dominate NO3- distribution in urban groundwater. Nitrification from organic soil N, manure and sewage was significant in some sampling areas, and NO3- isotopic values from groundwater in Xi’an indicated that the effects of denitrification were not an obvious contributor. Thus, the δ15N–NO3- enrichment process is mainly caused by the intense anthropogenic activity in the city center. From the urban center to suburban areas, the mean δ15N–NO3- values varied from +16.4‰ to +5.4‰, and the mean NO3-–N concentrations varied from 28.0 mg L−1 to 4.0 mg L−1. In particular, the δ15N–NO3- value (r = −0.75, p < 0.01) correlated more significantly with distance from the urban center than did the NO3-–N concentration data (r = −0.49, p < 0.01), which suggests that NO3- isotopic values are an effective indicator of contamination sources. In addition, the δ15N–NO3- values and population density show a significant logarithmic correlation in Xi’an city

  18. Soil moisture dynamics of caragana korshinskii woodland in loess plateau of northwest china

    International Nuclear Information System (INIS)

    Root water uptake is an important process of water circle and a component of water balance in the field. It should be understood better and effectively. A quantitative method of determining root water uptake should be built for efficient water use. The aims of this paper were to develop a water uptake model for single Caragana Korshinskii individual and to validate the model with soil water content in a plantation. Tube-time domain reflectometry (TDR) was used to measure soil volumetric water content, and sap flow sensors based on stem-heat technology were used to monitor locally the sap flow rates in the stems of C. Korshinskii. Root density distribution was determined and soil hydraulic characteristics parameters were fitted from measurements. A root water uptake model was established, which includes root density distribution function, potential transpiration and soil water stress-modified factor. The measured data were compared against the outputs of transpiration rate and soil water contents from the numerical simulation of the soil water dynamics that uses Richards equation for water flow and the established root uptake model. The results showed an excellent agreement between the measured data and the simulated outputs, which indicate that the developed root water uptake model is effective and feasible. (author)

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

    OpenAIRE

    Feng, X. M.; Sun, G; Fu, B. J.; Su, C H; Liu, Y.; Lamparski, H.

    2012-01-01

    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...

  20. Radiative plateau inflation

    Science.gov (United States)

    Ballesteros, Guillermo; Tamarit, Carlos

    2016-02-01

    We describe how monomial chaotic inflation becomes compatible with the latest CMB data thanks to radiative corrections producing a plateau. The interactions of the inflaton with other fields, required for reheating, can flatten the potential and moderate the production of primordial gravitational waves, keeping these below the current upper bound. We show that the appearance of a plateau requires that the inflaton couples to fermions and to another scalar or a gauge group. We give concrete examples of minimal particle physics models leading to plateaus for quadratic and quartic chaotic inflation. We also provide a three-parameter model-independent description of radiatively corrected inflation that is amenable to CMB analyses.

  1. Radiative plateau inflation

    CERN Document Server

    Ballesteros, Guillermo

    2015-01-01

    We describe how monomial chaotic inflation becomes compatible with the latest CMB data thanks to radiative corrections producing a plateau. The interactions of the inflation with other fields, required for reheating, can flatten the potential and moderate the production of primordial gravitational waves, keeping these below the current upper bound. We show that the appearance of a plateau requires that the inflaton couples to fermions and to another scalar or a gauge group. We give concrete examples of minimal particle physics models leading to plateaus for quadratic and quartic chaotic inflation. We also provide a three-parameter model-independent description of radiatively corrected inflation that is amenable to CMB analyses.

  2. Holocene cold events on the Tibetan Plateau

    Science.gov (United States)

    Mischke, Steffen; Zhang, Chengjun

    2010-06-01

    did not reach the significance of the cold event at 4.2 cal ka BP. However, the three cold periods since 4.2 cal ka BP are apparently coeval with the decline and establishment of Chinese Dynasties implying a remarkable impact on the social systems in eastern China. The consistent inference of cold events around 8.2 cal ka BP or a few hundred years later and starting at 4.2 cal ka BP is evidence for a temporary trans-regional climatic response on the Tibetan Plateau in the Holocene regardless of the catchment-specific response of complex natural systems.

  3. δ13CSC values of the loess-paleosol sequence in Dali area, Shaanxi Province, China, and paleoenvironmental implications

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The carbon isotopic ratios of carbonate in the two profiles of the Dali area were analyzed and some new understandings on the influencing factors of the δ13CSC value of the loess-paleosol sequence and its paleoenvironmental implications were discussed preliminarily in this report. The 13CSC value of the Dali loess-paleosol sequence is synchronizing with the variance of magnetic susceptibility basically and the negative peaks of the δ13CSC curves are corresponding to the different developmental periods of the paleosol. It is believed that the intervention of the CO2 produced by plants will cause the decrease of the δ13CSC value, the amplitude of which may be relevant to the paleovegetation density and the ancient humidity. The relative biomass of C4 plants in the vegetation will affect the sublevel change of the δ13CSC. Low δ13CSC value by and large indicates the environmental conditions of the relatively abundant vegetation and humid climate. During the last 250000 years, the period with the sparsest vegetation and the most arid climate is the phase of the loess in L2 depositing and the period with the most abundant vegetation and the most humid climate is the last interglacial period. The δ13CSC curves of Dali also show that the High Temperature and Large Precipitation Event of the Qinghai-Tibetan Plateau during 40-30 kaBP had affected the Central Shaanxi Plain with relatively humid climate, and had apparent influence on the local vegetation and humidity.

  4. The Lithium Plateau Enigma

    OpenAIRE

    Charbonnel, C.; Vauclair, S.

    1998-01-01

    Why is the lithium abundance constant in the so-called lithium plateau while all predictions suggest that it should vary from star to star? Can we find a "lithium attractor" which would remain stable in halo stars while fundamental parameters (M_*, Teff, [Fe/H]) vary?

  5. Experimental Study of the Subsidence Characteristics of Clayey Loess

    Institute of Scientific and Technical Information of China (English)

    Li Lan; Wang Lanmin

    2007-01-01

    Presented in this paper are the results of experimental study and analysis of the subsidence characteristics obtained from soil samples with different contents of clay particles though laboratory dynamic triaxial test, Laser particle size analysis, chemical analysis and electronic microscope scanning. By comparison of the obtained data, the following conclusions are drawn out: (1)The stability of the loess varies with different content of clay; (2) The relation between the dynamic shear strength and the clay particles is not monotonous, but parabolic; (3) In the same consolidation ratio, the clayey loess is the weakest subsidence-resistant when the clay particle content is between 16% ~ 17%.

  6. Soil development on loess overlying Cretaceous sediments and Devonian limestones

    Czech Academy of Sciences Publication Activity Database

    Žigová, Anna; Šťastný, Martin

    2015-01-01

    Roč. 12, č. 3 (2015), s. 267-278. ISSN 1214-9705 Institutional support: RVO:67985831 Keywords : loess * Cretaceous and Devonian rocks * mineral composition * soil development * Luvic Chernozem * Albic Luvisol Subject RIV: DF - Soil Science Impact factor: 0.389, year: 2014

  7. Features of major greenhouse gases in loess, Shanxi Province,China

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    According to the investigations of five loess sections in Shanxi Province, China, it was found that the concentrations of the major greenhouse gases CO2, CH4 and NaO in loess-paleosol sequences are generally high, even sometimes may be several times or scores of times higher than their atmospheric concentrations respectively. Although the CO2 concentration in the same loess section shows poor regularity among different layers, it increases slowly from north to south in space. The CH4 concentration in the layers under Malan Loess is much higher than that in the atmosphere, although it is not high in Malan Loess. Most of the δ13C values of CO2 in loess are -11.14‰-15.48‰ (relative to PDB standard). Analysis of carbon isotopic compositions of CO2 indicates that the main source of CO2 in loess section The δ13Cg of CO2 is a little heavier than organic source for exchanging carbon isotope with carbonate in loess. The abundant carbonate in loess not only makes the loess a huge carbon reservior but also adjusts atmospheric CO2 during the formation of deuterogenic carbonate.``

  8. Embedded Plateau Problem

    OpenAIRE

    Coşkunuzer, Barış

    2010-01-01

    TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 364, Number 3, March 2012, Pages 1211–1224 S 0002-9947(2011)05486-3 Article electronically published on October 19, 2011 EMBEDDED PLATEAU PROBLEM BARIS COSKUNUZER Abstract. We show that if Γ is a simple closed curve bounding an embedded disk in a closed 3-manifold M, then there exists a disk Σ in M with boundary Γ such that Σ minimizes the area among the embedded disks with boundary Γ. Moreover, Σ is smooth...

  9. Time Series Analysis of Soil Moisture Storage Dynamic Change in the Chinese Pine Forest Land in Hilly Region of the Loess Plateau%黄土丘陵区人工油松林地土壤水分动态的时间序列分析

    Institute of Scientific and Technical Information of China (English)

    石辉; 刘世荣; 孙鹏森; 李秧秧

    2004-01-01

    利用时间序列分析方法研究了黄土丘陵区人工油松林地土壤水分序列和降水序列之间的关系.在黄土丘陵区,降水时间序列不存在自相关关系,相反土壤贮水量之间存在自相关关系;这说明了前期降水对后期降水没有影响,而前期土壤含水量的高低影响了后期含水量的多少.降水时间序列与人工油松林地0~80 cm土层总贮水量序列之间存在相关关系,同时油松林地贮水量与降水时间序列相比表现出1个滞后时间距(1月),说明贮水量主要受当月和前一个月降水的影响.对于上部三个层次(0~10 crm,10~20cm,20~40 cm)的贮水动态与降水时间序列相关;而20cm以下的土层,与一个滞后时间距的降水时间序列相关系数增大;说明20 cm以上土层的贮水量主要受当月降水的影响,20 cm以下土层贮水量与当月和前一个月的降水有关.当月降水可以补充到40cm深土层.

  10. Dynamics of Soil Water Content under Different Forestland in the Loess Hilly Region%黄土丘陵区不同林地土壤水分动态变化

    Institute of Scientific and Technical Information of China (English)

    王晶; 朱清科; 刘中奇; 邝高明; 赵荟

    2011-01-01

    研究黄土丘陵区不同林地的土壤水分变化,对于改善黄土高原生态环境建设有着重要的意义.采用定点监测的方法,对陕西省吴起县不同林地土壤水分动态变化进行了研究.结果表明:不同林地在生长季中土壤蓄水量具有显著差异,其顺序为:沙棘林>河北杨林>油松林>山杏林;林地的土壤蓄水量变化具有明显的季节性,根据生长季内土壤蓄水量的变化,可以将土壤水分变化分为3个时期:土壤水分恢复期、土壤水分消耗期、土壤水分补充期;各林地0-200 cm土层土壤水分变异系数从小到大为:山杏林>河北杨林>沙棘林>油松林;在雨水人渗、蒸发、蒸散的共同作用下山杏林地在0-60 cm土层含水量的变化明显大于其它林地.研究结果揭示了不同林种对土壤水分消耗和补给的影响,为当地造林结构配置和植被恢复与重建工作提供一定参考依据.%Soil water content is crucial to vegetation rehabilitation on the hilly loess plateau.Using fixed-point dynamic monitoring methods, dynamics of soil water content under different forest were studied in forest or grass lands converted from farmlands in loess hilly region.Results showed that different forestland has a significant differences on soil water storage capacity in the growing season, in terms of soil water, forest species may be ranked in the descendant order of sea buckthorn, hebei poplar, Chinese pine, prunus armeniaca; forestland soil water storage has obvious seasonal change, according to growing season changes in soil water storage, soil moisture changes can be divided into three period: recovery period of soil moisture, consumption period of soil water, replenishment period of soil moisture; in the 0-200 cm soil layer, the variation coefficient of soil water in forestland may be ranked in the descendant order of prunus armeniaca, hebei poplar, sea buckthorn, Chinese pine.In the action of rainwater infiltration, evaporation

  11. Characteristics of structural loess strength and preliminary framework for joint strength formula

    OpenAIRE

    Rong-jian LI; Jun-ding LIU; Yan, Rui; Zheng, Wen; Sheng-jun SHAO

    2014-01-01

    The strength of structural loess consists of the shear strength and tensile strength. In this study, the stress path, the failure envelope of principal stress ( line), and the strength failure envelope of structurally intact loess and remolded loess were analyzed through three kinds of tests: the tensile strength test, the uniaxial compressive strength test, and the conventional triaxial shear strength test. Then, in order to describe the tensile strength and shear strength of structural loes...

  12. Holocene loess and paleosols in Central Alaska: A proxy record of holocene climate change

    International Nuclear Information System (INIS)

    Episodic Holocene loess deposition and soil formation in the sediments of the Nenana valley of Central Alaska may reflect Holocene climate change. Periods of loess deposition seem to correlate with times of alpine glacier activity, while paleosols correspond to times of glacial retreat. These variations may reflect changes in solar activity. Other mechanisms, such as orbitally forced changes in seasonality, volcanism, and atmospheric CO2 variability may also have affected Holocene climates and loess deposition

  13. The precision of water content estimates in the thermoluminescence dating of loess from Northern Pakistan

    International Nuclear Information System (INIS)

    The estimation of water content since deposition presents a major source of uncertainty in the thermoluminescence dating of sediments. In the case of loess, information on dry density, porosity, pore size distribution, microstructures and behaviour during laboratory compaction tests may be used to obtain estimates of water content during burial. The results of laboratory studies of loesses from northern Pakistan are presented and their implications for the TL dating of loesses from different stratigraphic horizons are explored. (author)

  14. Intensive winds during glacial periods increased sand-dune activity and loess deposition

    Science.gov (United States)

    Crouvi, O.; Enzel, Y.; Amit, R.; Gillespie, A.

    2010-12-01

    The formation of loess in deserts worldwide is mostly attributed to glacial periods, whereas during interglaciations (e.g. the Holocene) loess deposition rates are reported as minimal. Several explanations for this glacial-interglacial change in loess formation were proposed in the past, but no consensus exists. We examined the data available for several well-known loess accretion zones near subtropical deserts (including Sahara, Sinai-Negev, and Arabia) and show that all these loess zones are located downwind of adjacent sand dunes/seas that were active in the late Pleistocene as indicated by dune orientations. Moreover, mineralogical similarity is common to the loess and the upwind sand dunes, intensified erg activity and loess formation are temporally associated and grain-size mode of loess decreases systematically with distance from ergs. These observations suggest that sand dunes were an important primary source for desert loess, probably through aeolian abrasion of sand grains. Only intense, windy episodes in low and mid-latitudes worldwide could have (a) advanced and/or mobilized these dune fields and (b) forcefully abraded sand into silts. The common denominator underlying both dune activity and loess deposition must be winds with sufficient strength to mobilize dunes; either increased aridity at the source or increased precipitation at the sink or both together cannot dominate the coupled silty dust supply and loess deposition, as previously suggested. Both conditions are ubiquitous today in desert margins: most of the studied desert loess regions are located in semi-arid climate, where there is enough rainfall (>150-200 mm/yr) to deposit loess, whereas the loess regions suggested sources (i.e. the adjacent, upwind sand seas) are located in extremely dry (<50 mm/yr) climate. However, loess accretion downwind of ergs today is insignificant; the main change has been wind strength: modern wind durations and strengths are probably insufficient for significant

  15. Plateau Rayleigh instability simulation.

    Science.gov (United States)

    Mead-Hunter, Ryan; King, Andrew J C; Mullins, Benjamin J

    2012-05-01

    The well-known phenomena of Plateau-Rayleigh instability has been simulated using computational fluid dynamics (CFD). The breakup of a liquid film into an array of droplets on a cylindrical element was simulated using a volume-of-fluid (VOF) solver and compared to experimental observations and existing theory. It is demonstrated that the VOF method can correctly predict the breakup of thins films into an array of either axisymmetric droplets or clam-shell droplets, depending on the surface energy. The existence of unrealistically large films is precluded. Droplet spacing was found to show reasonable agreement with theory. Droplet motion and displacement under fluid flow was also examined and compared to that in previous studies. It was found that the presence of air flow around the droplet does not influence the stable film thickness; however, it reduces the time required for droplet formation. Novel relationships for droplet displacement were derived from the results. PMID:22512475

  16. Mineral composition of agricultural soils developed on loess

    Czech Academy of Sciences Publication Activity Database

    Žigová, Anna; Šťastný, Martin

    Troubsko : Research institute for Fodder Crops, 2011 - (Badalíková, B.), s. 109-114 ISBN 978-80-86908-27-4. [International Soil Conference ISTRO - Czech Branch /6./. Průhonice (CZ), 31.08.2011-02.09.2011] R&D Projects: GA ČR GA526/08/0434 Institutional research plan: CEZ:AV0Z30130516 Keywords : loess * mineralogy * Haplic Chernozem * Haplic Luvisol * Greyic Phaeozem Subject RIV: DF - Soil Science

  17. Optical dating of coarse-silt sized quartz from loess: Evaluation of equivalent dose determinations and SAR procedural checks

    International Nuclear Information System (INIS)

    This study discusses the values of equivalent dose (De) determined for samples taken for optical dating from a loess section at Loveland, Iowa, North America. A modified single-aliquot regenerative-dose (SAR) procedure was applied to quartz grains of 35-50μm diameter which were isolated using hydrofluorosilicic acid (H2SiF6). 'Preheat plots' were constructed to select appropriate De values for use in subsequent age determinations. The De values of the younger (Peoria loess) samples varied little with preheat temperatures between 160 and 300 deg. C. However, the older (Pisgah Formation) samples showed a decrease in De values with increasing preheat temperature, by as much as a factor of two. Interestingly, both younger and older samples could recover a known laboratory administered radiation dose for a range of preheat temperatures. These apparently contradictory findings present a dilemma regarding which De values are the most appropriate to use for dating the samples. The behaviour of the samples is examined to investigate the cause of the variations in De values with preheat temperature for older samples. In addition, two modified SAR procedures were tested in an attempt to generate more reproducible De values. The data from the three SAR methods are examined, and the question of how to discriminate between De values is discussed. This study demonstrates that preheat temperature can play a significant role in the determination of De values. The use of plots of normalised luminescence signal (Lx/Tx) versus preheat temperature is proposed to supplement dose recovery tests and preheat plateau tests

  18. Methodical comparison of neutron depth probes and long-term soil moisture measurements on loess, sandy loess, and boulder clay

    International Nuclear Information System (INIS)

    Three measuring instruments were tested: 0.05 mCi Cf-252, 100 mCi Am-241/Be, 500 mCi Am-241/Be. The advantages - measurement in undisturbed soil profiles, large depths of measurement, reproducibility of measurements in the same place over several years - and the disadvantages - radiation protection, resolution, variations of measured volume in dependence of moisture, background influences etc. - have been critically checked by experiment. In addition, annual soil moisture curves have been measured over two years by parallel use of the free probes on a loess, sandy loess, and boulder clay site. The results were compared and discussed with a view to the soil water dynamics of these sites. (orig./HP)

  19. 150,000 years of loess accumulation in central Alaska

    Science.gov (United States)

    Jensen, Britta J. L.; Evans, Michael E.; Froese, Duane G.; Kravchinsky, Vadim A.

    2016-03-01

    The Halfway House site in interior Alaska is arguably the most studied loess deposit in northwestern North America. The site contains a complex paleomagnetic and paleoenvironmental record, but has lacked the robust chronologic control that would allow its full potential to be exploited. Detailed reexamination of stratigraphy, paleomagnetics and tephrostratigraphy reveals a relatively complete marine isotope stage (MIS) 6 to Holocene record constrained by the Old Crow (124 ± 10 ka), VT (106 ± 10 ka), Sheep Creek-Klondike (ca. 80 ka), Dominion Creek (77 ± 8 ka) and Dawson (ca. 30.2 cal ka BP) tephras. We show two well-developed paleosols formed during Marine Isotope Stages (MIS) 5e and 5a, while MIS 5c and 5b are either poorly represented or absent. The new tephrostratigraphy presented here is the most complete one to date for the late Pleistocene and indicates MIS 5 sediments are more common than previously recognized. A magnetic excursion within the sediments is identified as the post-Blake excursion (94.1 ± 7.8 ka), providing independent age control and adding to the increasing body of evidence that Alaskan loess is a detailed recorder of variations of the Earth's magnetic field over time. A high-resolution magnetic susceptibility profile placed into this new chronostratigraphic framework supports the hypothesis that wind-intensity is the main variable controlling fluctuations in susceptibility. Correlation of the susceptibility record to global marine δ18O records is complicated by highly variable accumulation rates. We find the lowest rates of accumulation during peak warm and cold stages, while abrupt increases are associated with periods of transition between marine isotope (sub)stages. Building on previous accumulation models for Alaska, surface roughness is likely a leading variable controlling loess accumulation rates during transitions and peak cold periods, but the negligible accumulation during MIS 5e and 5a suggests that loess production was

  20. Organizational restructuring and career plateauing

    OpenAIRE

    Paffen, P.; Timmermans, Hans

    2009-01-01

    This article describes a flexibility program for plateaued professionals in a technical Dutch firm operating in the consultancy sector we will refer to with the pseudonym Greentree Corp. First, we will discuss the impact reorganization had on job-requirements and career opportunities for technical employees. Secondly, we will discuss the program the company developed in close cooperation with external consultants to make the plateaued workforce more flexible and the outcomes of the flexibilit...

  1. CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY

    Energy Technology Data Exchange (ETDEWEB)

    BERGMAN, T. B.; STEFANSKI, L. D.; SEELEY, P. N.; ZINSLI, L. C.; CUSACK, L. J.

    2012-09-19

    THE CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY WAS CONDUCTED TO DEVELOP AN OPTIMAL SEQUENCE OF REMEDIATION ACTIVITIES IMPLEMENTING THE CERCLA DECISION ON THE CENTRAL PLATEAU. THE STUDY DEFINES A SEQUENCE OF ACTIVITIES THAT RESULT IN AN EFFECTIVE USE OF RESOURCES FROM A STRATEGIC PERSPECTIVE WHEN CONSIDERING EQUIPMENT PROCUREMENT AND STAGING, WORKFORCE MOBILIZATION/DEMOBILIZATION, WORKFORCE LEVELING, WORKFORCE SKILL-MIX, AND OTHER REMEDIATION/DISPOSITION PROJECT EXECUTION PARAMETERS.

  2. Bijdrage tot de kennis van loess en dekzanden : in het bijzonder van de Zuidoostelijke Veluwe

    NARCIS (Netherlands)

    Vink, A.P.A.

    1949-01-01

    A detailed map of loess and cover sand, occurring along the south-eastern border of the Veluwe; Gelderland, was made to check hypotheses on the origin of loess and cover sand.The eastern flank of the Veluwe hills, consisting of glacial sand and gravel, proved to be covered by fine cover sand near th

  3. Survival and growth of Cochlodinium polykrikoides red tide after addition of yellow loess.

    Science.gov (United States)

    Lee, Young Sik; Kim, Jung Dong; Lim, Weol Ae; Lee, Sam Geun

    2009-11-01

    We examined the survival rate of Cochlodinium polykrikoides after yellow loess addition and conducted culture experiments to investigate the possibility that red tides maybe caused by C. polykrikoides individuals that are precipitated when loess is added. At least 15% of the C. polykrikoides cells that precipitated to the bottom layer either by the addition of loess or no addition survived for 1 week at all growth phases, rather than disappearing immediately after precipitating. However no live cells were observed after 20 days, regardless of phase or loess addition. In the exponential phase, the number of C. polykrikoides cells increased to >2886 cells ml(-1) after loess was added. However in the stationary phase, the number of cells did not increase until 18 days. In the exponential phase, those C. polykrikoides that survived precipitation caused by scattering loess on cultures did not appear to have the ability to cause red tides again because of the short red tide periods in the field, long lag time after loess addition, and low survival rate after loess addition. PMID:20329384

  4. Response of grain size of Quaternary gravels to climate and tectonics in the northern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The widely distributed thick gravel deposits along the rim of the Tibetan Plateau have been long thought to be the product of rapid tectonic uplift of the plateau. However, this has been challenged by recent works that suggest these thick gravels may be the result of climate change. In this paper we carried out a detailed field measurement of gravel grain sizes from the Jiuquan and Gobi Gravel Beds in the top of the Laojunmiao section in the Jiuxi Basin in the northern margin of Qilian Mts. (northern Tibetan Plateau). The results suggest that the grain sizes of the Jiuquan and Gobi Gravel Beds over the last 0.8 Ma are characterized by nine coarse-fine cycles having strong 100-ka and 41-ka periodicities that correlate well with the loess-paleosol monsoon record and isotopic global climatic record from deep sea sediments as well as by a long trend of coarsening in gravel grain size. The coarse gravel layers were formed during the warm-humid interglaciations while the fine layers correspond to the cold-dry glaciations. Because the paleoclimate in NW China began to get dramatically drier after the mid-Pleistocene, we think the persistent coarsening of gravel grain size was most probably caused by the rapid uplift of the northern Tibetan Plateau, and that the orbital scale cyclic variations in gravel grain size were driven by orbital forcing factors that were superimposed on the tectonically-forced long-term coarsening trend in gravel size. These findings also shed new light on the interaction results of climate and tectonics in relation to the uplift of the Tibetan Plateau.