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Factors determining soil water heterogeneity on the Chinese Loess Plateau as based on an empirical mode decomposition method

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Journal of Arid Land 2020年第3期12卷 462-472页

作者： GONG Yidan XING Xuguang WANG Weihua Faculty of Agriculture and Food Kunming University of Science and TechnologyKunming 650500China Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education Northwest A&F UniversityYangling 712100China

Soil water is a critical resource,and as such is the focus of considerable physical research.Characterization of the distribution and spatial variability of soil water content(SWC)offers important agronomic and environmental information.Estimation of non-stationary and non-linear SWC distribution at different scales is a research challenge.Based on this context,we performed a case study on the Chinese Loess Plateau,with objectives of investigating spatial variability of SWC and soil properties(i.e.,soil particle composition,organic matter and bulk density),and determining multi-scale correlations between SWC and soil properties.A total of 86 in situ sampling sites were selected and 516 soil samples(0–60 cm depth with an interval of 10 cm)were collected in May and June of 2019 along the Yangling-Wugong-Qianxian transect,with a length of 25.5 km,in a typical wheat-corn rotation region of the Chinese Loess Plateau.Classical statistics and empirical mode decomposition(EMD)method were applied to evaluate characteristics of the overall and scale-specific spatial variation of SWC,and to explore scale-specific correlations between SWC and soil properties.Results showed that the spatial variability of SWC along the Yangling-Wugong-Qianxian transect was medium to weak,with a variability coefficient range of 0.06–0.18,and it was gradually decreased as scale increased.We categorized the overall SWC for each soil layer under an intrinsic mode function(IMF)number based on the scale of occurrence,and found that the component IMF1 exhibited the largest contribution rates of 36.45%–56.70%.Additionally,by using EMD method,we categorized the general variation of SWC under different numbers of IMFs according to occurrence scale,and the results showed that the calculated scales among SWC for each soil layer increased in correspondence with higher IMF numbers.Approximately 78.00%of the total variance of SWC was extracted in IMF1 and IMF2.Generally,soil texture was the dominant control on SWC,and the influence of the three types of soi

关键词： bulk density Loess Plateau soil water soil organic matter soil texture spatial variability

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Erosion-control mechanism of sediment check dams on the Loess Plateau

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International Journal of Sediment Research 2021年第5期36卷 668-677页

作者： Zhaoyin Wang Zuyu Chena Shu Yu Qiang Zhang Yu Wang Jianwei Hao State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research

Severe soil erosion occurs on the Loess Plateau in China, which makes the Yellow River the most sediment-laden river in the world. Construction of about 60,000 sediment check dams has remarkably controlled soil erosion on the Loess Plateau and reduced the sediment load of the middle and lower Yellow River. Nonetheless, little is known about the mechanism of erosion control and vegetation development of sediment check dams. The function of a single check dam mainly is trapping sediment,while the function of a train of check dams comprising dozens of or over hundreds of check dams in a gully encompasses controlling bed incision and reducing erosion energy. A formula was proposed to calculate the potential energy of bank failure and slope failure in a gully, which essentially constitutes the erosion energy. The erosion energy increases when gully incision occurs, which is induced by the incision of the Yellow River and its tributaries on the Loess Plateau. Sediment deposition in many gullies due to construction of check dams reduces the erosion energy to almost zero, which in turn greatly reduces soil erosion and sediment yield. Construction of check dams promotes vegetation development. The vegetation-erosion dynamics model was used to study the effect of check dams on vegetation development. Simulation results show that reforestation without check dam construction might result in an increase of vegetation cover in the first ten years and then a drop of vegetation cover to less than 10% in the later years. The check dams provide a foundation for vegetation development.

关键词： Loess Plateau Check dam Energy of soil erosion Vegetation-erosion dynamics Gully incision

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Regional features of topographic relief over the Loess Plateau,China:evidence from ensemble empirical mode decomposition

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Frontiers of Earth Science 2020年第4期14卷 695-710页

作者： Yongjuan Liu Jianjun Cao Liping Wang Xuan Fang Wolfgang Wagner School of Environment Science and Spatial Informatics China University of Mining and TechnologyXuzhou221116China School of Geography Science/Key Laboratory of Virtual Geographic Environment of Ministry of Education Nanjing Normal UniversityNanjing210023China School of Environmental Science Nanjing Xiaozhuang UniversityNanjing211171China Department of Geodesy and Geoinformation Vienna University of TechnologyVienna1040Austria

Landforms with similar surface matter compositions,endogenic and exogenic forces,and development histories tend to exhibit significant degrees of self-similarity in morphology and spatial variation.In loess hill-gully areas,ridges and hills have similar topographic relief characteristics and present nearly periodic variations of similar repeating structures at certain spatial scales,which is termed the topographic relief period(TRP).This is a relatively new concept,which is different from the degree of relief,and describes the fluctuations of the terrain from both horizontal and vertical(cross-section)perspectives,which can be used for in-depth analysis of 2-D topographic relief features.This technique provides a new perspective for understanding the macro characteristics and differentiation patterns of loess landforms.We investigate TRP variation features of different landforms on the Loess Plateau,China,by extracting catchment boundary profiles(CBPs)from 5 m resolution digital elevation model(DEM)data.These profiles were subjected to temporal-frequency analysis using the ensemble empirical mode decomposition(EEMD)method.The results showed that loess landforms are characterized by significant regional topographic relief;the CBP of 14 sample areas exhibited an overall pattern of decreasing TRPs and increasing topographic relief spatial frequencies from south to north.According to the TRPs and topographic relief characteristics,the topographic relief of the Loess Plateau was divided into four types that have obvious regional differences.The findings of this study enrich the theories and methods for digital terrain data analysis of the Loess Plateau.Future study should undertake a more in-depth investigation regarding the complexity of the region and to address the limitations of the EEMD method.

关键词： catchment boundary profile topographic relief period ensemble empirical mode decomposition Loess Plateau

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Is the runoff coefficient increasing or decreasing after ecological restoration on China’s Loess Plateau?

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International Soil and Water Conservation Research 2021年第3期9卷 333-343页

作者： Haiyan Zheng Chiyuan Miao Guanghui Zhang Xiaoyan Li Shuai Wang Jingwen Wu Jiaojiao Gou State Key Laboratory of Earth Surface Processes and Resource Ecology Faculty of Geographical ScienceBeijing Normal UniversityBeijing100875China

The“Grain for Green”project(GGP)was launched in 1999 on China’s Loess Plateau to reduce soil erosion,which had far-reaching impacts on the local eco-hydrological processes.In this study,we use monthly runoff depth and precipitation datasets spanning 1961 to 2015 for 16 primary basins of the plateau to reveal changes in runoff generation capacity before and after the GGP.We use a Budyko-based elasticity method to calculate the runoff depth(R_(1))and runoff coefficient(C_(1))exclusively attributable to land use/cover change.Results indicate that the mean annual runoff coefficients(Co)decline by 26%—76%from the periods 1961—1999 to 2000—2015.The annual observed runoff depth(Ro)and C_(0)for 75%of basins show significant downward trends during 1961—1999;after the implementation of the GGP,both annual Ro and annual Co for over 50%of basins show upward trends.The study further finds that the increase of erosive rainfall during the period 2000-2015,whose mean increasing rate reaches 4.6 mm/year,is the main reason for the upward trends of Ro and Co.After removing the effect of precipitation variation during this period,we find that 11 out of 16 basins show decreased trends for Cj,with the downward rate between 2.4%and 6.0%per year.The reduction rate in semi-arid areas is about four times the rate in semi-humid areas.The results remind us to consider the carrying capacity of local water resources when implementing soil and water conservation measures across the Loess Plateau.

关键词： Loess Plateau Precipitation Runoff coefficient Budyko-based elasticity method Land use/cover change

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预测和评估黄土高原多情景土地利用模拟下NPP的变化

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Journal of Geographical Sciences 2021年第7期31卷 977-996页

作者：江笑薇白建军 School of Geography and Tourism Shaanxi Normal UniversityXi'an 710119China

Land use/cover change(LUCC)is a major factor affecting net primary production(NPP).According to the LUCC of the Loess Plateau from 2005 to 2015,the LUCC patterns in 2025 in three scenarios were predicted by using the Future Land Use Simulation(FLUS)model.Furthermore,taking the average NPP of various land use/cover types in 16 years as the reference scale,the changes in NPP in multi-scenario simulations are predicted and analyzed,and the impact of different land use/cover transfers on NPP is quantified.The results are as follows:(1)The land use/cover changes greatly in the baseline and fast development scenarios,and changes relatively little in the ecological protection scenarios.(2)The changes in NPP in different scenarios reflected the significant difference in the ecological protection effect.All the three scenarios promote an NPP increase,but the ecological protection scenario can promote NPP increases the most.(3)The changes in NPP caused by LUCC in the three scenarios reflected the significant difference in the various land use/cover types protection effect.Analyzing and predicting NPP changes in multi-scenario LUCC simulations in the future can provide a theoretical basis for decision makers to judge the future changes in ecological environments and ecological protection effects against different policy backgrounds.

关键词： net primary production(NPP) scenario simulation land use/cover change(LUCC) Loess Plateau

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Increasing rainfed wheat yield by optimizing agronomic practices to consume more subsoil water in the Loess Plateau

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The Crop Journal 2021年第6期9卷 1418-1427页

作者： Wenjia Yang Weijian Liu Yulin Li Shiwen Wang Lina Yin Xiping Deng State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau College of Natural Resources and EnvironmentNorthwest A&F UniversityYangling 712100ShaanxiChina College of Life Sciences Northwest A&F UniversityYangling 712100ShaanxiChina Institute of Soil and Water Conservation Northwest A&F UniversityYangling 712100ShaanxiChina Institute of Soil and Water Conservation Chinese Academy of Sciences&Ministry of Water ResourcesYangling 712100ShaanxiChina

Erratic rainfall and misalignment between the rainy season and the growing season of winter wheat greatly limit rainfed winter wheat yield in the Loess Plateau of China. To increase the grain yield of winter wheat in this region, the effects of different agronomic practices, including adjusting planting pattern(NR, narrow row spacing), increasing seeding rate(high seeding rate, HS), decreasing basal nitrogen rate and increasing top-dressed nitrogen rate(DBN), and replacing an old cultivar with a new cultivar(NC) on wheat yield were investigated for two consecutive years. The results showed that the current grain yield of rainfed winter wheat in the Loess Plateau could be increased to 5879–7093 kg ha^(-1) by HS, DBN and NC practices relative to the practice of high-yielding farmers(PF). The increased yield due to HS, DBN and NC was attributed to the higher number of spikes ha^(-1), 1000-grain weight, and kernels spike^(-1). Before the flowering stage, HS increased soil water consumption(SWC) in 1–3 m subsoil due to the higher plant population compared with that of PF, whereas DBN decreased SWC in the 0–2 m soil layer compared with that of PF. After the flowering stage, HS, DBN, and NC increased SWC by 8–16 mm in 2–3 m subsoil compared to PF. The water use efficiency(WUE) was increased under DBN and NC in comparison with PF.However, the WUE did not increase under HS as it had the highest evapotranspiration among the five treatments. Increasing the use of subsoil water during the late growth stage by optimizing agronomic practices or applying new cultivars with expansive roots should be the primary approach to increase rainfed winter wheat yield in this region.

关键词： Winter wheat Agronomic practices Soil water consumption Grain yield Loess Plateau

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Comparing surface erosion processes in four soils from the Loess Plateau under extreme rainfall events

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International Soil and Water Conservation Research 2021年第4期9卷 520-531页

作者： Liying Sun John L.Zhou Qiangguo Cai Suxia Liu Jingan Xiao Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China School of Civil and Environmental Engineering University of Technology Sydney15 BroadwayNSW 2007Australia

This research aims to improve erosion control practice in the Loess Plateau,by studying the surface erosion processes,including splash,sheet/interrill and rill erosion in four contrasting soils under high rainfall intensity(120 mm h^(−1))with three-scale indoor artificial experiments.Four contrasting soils as sandy loam,sandy clay loam,clay loam and loamy clay were collected from different parts of the Loess Plateau.The results showed that sediment load was significantly impacted by soil properties in all three sub-processes.Splash rate(4.0-21.6 g m^(−2∙)min^(−1))was highest in sandy loam from the north part of the Loess Plateau and showed a negative power relation with the mean weight diameter of aggregates after 20 min of rainfall duration.The average sediment load by sheet/interrill erosion(6.94-42.86 g m^(−2∙)min^(−1))was highest in clay loam from middle part of the Loess Plateau,and the stable sediment load after 20 min showed a positive power relation with the silt content in soil.The average sediment load increased dramatically by rill and interrill erosion(21.03-432.16 g m^(−2∙)min^(−1)),which was highest in loamy clay from south part of the Loess Plateau.The average sediment load after the occurrence of rill showed a positive power relation with clay content and a negative power relation with soil organic matter content.The impacts of slope gradient on the runoff rate and sediment load also changed with soil properties.The critical factors varied for different processes,which were the aggregate size for splash erosion,the content of silt particles and slope gradient for sheet/interrill erosion,and the content of clay particles,soil organic matter and slope gradient for rill erosion.Based on the results of the experiments,specific erosion control practices were proposed by targeting certain erosion processes in areas with different soil texture and different distribution of slope gradient.The findings from this study should support the improvement of erosion prediction and cropland management in different

关键词： Soil erosion process Particle size Surface erosion Cropland management Loess Plateau

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Vegetation Mapping for Regional Ecological Research and Management: A Case of the Loess Plateau in China

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Chinese Geographical Science 2020年第3期30卷 410-426页

作者： LIU Yuanxin LYU Yihe BAI Yingfei ZHANG Buyun TONG Xiaolin State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of Sci-encesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China The Grain for Green Project Management Office of Yan'an Municipality Yan'an 716000China The Grain for Green Project Management Office of Ansai Dis-trict Yan'an 717400China

Vegetation maps are fundamental for regional-scale ecological research. However, information is often not sufficiently up to date for such research. The Loess Plateau is a key area for vegetation restoration projects and a suitable area for regional ecological research. To carry out regional vegetation mapping based on the principles of hierarchical classification, object-oriented methods, visual interpretation, and accuracy assessment, this study integrated land cover, high-resolution remote sensing images, background environmental data, bioclimate zoning data, and field survey data from the Loess Plateau. To further clarify the implications of vegetation mapping, we compared the deviation of the 2015 vegetation map of the Loess Plateau(VMLP) and the widely used vegetation map of China(VMC)(1 : 1 000 000) for the expressed vegetation information and the evaluation of ecosystem services. The results indicated that 1) the vegetation of the Loess Plateau could be divided into 9 vegetation type groups and 18 vegetation types with classification accuracies of 87.76% and 83.97%, respectively;2) the distribution of vegetation had obvious zonal regularity;3) a deviation of 29.56 × 10^4 km^2 occurred when the vegetation coverage area was quantified with the VMC;4) the vegetation classification accuracy affected the ecosystem service assessment, the total water yield of the Loess Plateau calculated by the VMC and other required parameters was overestimated by 2.2 × 10^6 mm in 2015. Because vegetation mapping is a basic and important activity, that requires greater attention, this study provides supporting data for subsequent multivariate vegetation mapping and vegetation management for conservation and restoration.

关键词： vegetation map Loess Plateau spatial pattern vegetation classification ecosystem service

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黄土丘陵区雨强对水流含沙量的影响

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Journal of Geographical Sciences 2020年第3期30卷 455-467页

作者：刘晓燕党素珍刘昌明董国涛 Yellow River Conservancy Commission Zhengzhou 450003China Yellow River Institute of Hydraulic Research Yellow River Conservancy CommissionZhengzhou 450003China Beijing Normal University Beijing 100875China

To study the effects of changes in the rainfall intensity on sediment concentrations in the Loess Plateau,the observed rainfall intensities and sediment concentrations from three typical small watersheds were used to analyze the relationship between these parameters.The results showed that the sediment concentration generally increased with the increasing rainfall intensity on slope scale.However,at watershed scale,a significant threshold phenomenon was observed for the effects of the rainfall intensity on the sediment concentration.When the rainfall intensity exceeds the threshold,the flood sediment concentration will no longer increase with the increase in the rainfall intensity.The rainfall intensity threshold increased with increasing vegetation coverage.The rainfall intensity threshold was 10–15 mm/h during 1956–1969,reached 20 mm/h from 1990 to 1997 and is approximately 40 mm/h at present.Due to a rainfall intensity of 10–15 mm/h almost happened every year,the vegetation did not change much from the 1950s to 1980s.Sediment yield mainly depends on soil erosion caused by surface flow,but the surface flow speed does not increase indefinitely with the increase in the flow discharge.Thus,the annual maximum sediment concentration of the tributaries in the loess area has been basically stable before the 1990s.

关键词： Loess Plateau loess hilly region rainfall intensity sediment concentration influence

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Revegetation with artificial plants improves topsoil hydrological properties but intensifies deep-soil drying in northern Loess Plateau,China

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Journal of Arid Land 2018年第3期10卷 335-346页

作者： ZHANG Qingyin JIA Xiaoxu ZHAO Chunlei SHAO Ming'an State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Northwest A&F University Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences College of Resources and Environment University of Chinese Academy of Sciences

Knowledge about the effects of vegetation types on soil properties and on water dynamics in the soil profile is critical for revegetation strategies in water-scarce regions, especially the choice of vegetation type and human management measures. We focused on the analysis of the effects of vegetation type on soil hydrological properties and soil moisture variation in the 0–400 cm soil layer based on a long-term（2004―2016） experimental data in the northern Loess Plateau region, China. Soil bulk density（BD）, saturated soil hydraulic conductivity（Ks）, field capacity（FC） and soil organic carbon（SOC） in 2016, as well as the volumetric soil moisture content during 2004–2016, were measured in four vegetation types, i.e., shrubland（korshinsk peashrub）, artificial grassland（alfalfa）, fallow land and cropland（millet or potato）. Compared with cropland, revegetation with peashrub and alfalfa significantly decreased BD and increased Ks, FC, and SOC in the 0–40 cm soil layer, and fallow land significantly increased FC and SOC in the 0–10 cm soil layer. Soil water storage（SWS） significantly declined in shrubland and grassland in the 40–400 cm soil layer, causing severe soil drought in the deep soil layers. The study suggested that converting cropland to grassland（alfalfa） and shrubland（peashrub） improved soil-hydrological properties, but worsened water conditions in the deep soil profile. However, natural restoration did not intensify deep-soil drying. The results imply that natural restoration could be better than revegetation with peashrub and alfalfa in terms of good soil hydrological processes in the semi-arid Loess Plateau region.

关键词： soil drying soil hydrological property soil moisture vegetation restoration Loess Plateau

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