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Influences of rock fragments on the hydraulics and erosion of concentrated runoff in steep spoil heaps on the Loess plateau of China

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International Journal of Sediment Research 2022年第5期37卷 553-562页

作者： Wenzhao Guo Hongliang Kang Xiao Yu Wenlong Wang Pei Tian state key laboratory of soil erosion and dryland farming on the Loess plateau Institute of Water and Soil Conservation Northwest Agriculture & Forestry University key laboratory for Geographical Process Analysis & Simulation of Hubei Province Central China Normal University

The soil-rock mixed spoil heaps are prone to severe soil erosion during heavy rain, causing severe land degradation and ecological and environmental damage. Nevertheless, past research on the erosion on spoil heaps has focused on soil particles that were readily eroded and disregarded the rock fragments(RF) that were not readily eroded. To explore the effect of the RF embedded in spoil heaps on the hydraulics of and erosion caused by concentrated runoff, scour-erosion experiments were implemented on three types of spoil heaps: RF = 7%, RF = 45%, and RF = 69%. The RF clearly reduced runoff and erosion on steep spoil heaps. As the RF increased from 7% to 69%, the runoff intensity and runoff coefficient decreased by 72.9%-79.1% and 83.2%-84.1% respectively, and the sediment concentration, soil denudation rate, and total soil loss decreased by 36.0%-47.8%, 83.7%-87.1%, and 87.0%-92.3%, respectively.Narrow rills were generated during the experiments, and the RF distinctly influenced the rill characteristics. High contents of RF restrained rill retreating and undercutting, and promoted rill widening. With an increase in RF, the flow shear stress and stream power gradually decreased, and the Darcy-Weisbach roughness coefficient increased. These findings imply that the RF dissipated the flow energy and reduced soil detachment capacity and sediment transport capacity. soil detachment is strongly related to the Darcy-Weisbach roughness coefficient, Reynolds number, and runoff intensity,which may be the preferred descriptors of soil detachment. The current findings indicate that embedded rock fragments could effectively reduce soil loss on steep spoil heaps.

关键词： soil erosion Runoff Rock fragments (RF) Rills Chinese loess plateau

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Unique landslides (loess slide-flows) induced by an extreme rainstorm in 2018 on the Loess plateau: A new geological hazard and erosion process

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International Journal of Sediment Research 2023年第2期38卷 228-239页

作者： Li Luo Wen-Zhao Guo Pei Tian Yi-li Liu Shao-Kun Wang Jia-Wei Luo state key laboratory of soil erosion and dryland farming on the Loess plateau/College of Water Resources and Architectural Engineering Northwest Agriculture and Forestry University state key laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology key laboratory for Geographical Process Analysis & Simulation of Hubei Province Central China Normal University

Currently, the vegetation has recovered well in most areas of the Loess plateau in China, and soil erosion has significantly decreased. However, the heavy rainfall event in July 2018 triggered many instances of a unique type of loess landslides(i.e., slide-flows) on the gully-slopes with vegetation recovery in the Nanxiaohegou Basin on the Loess plateau. This rainfall event was unusual and was a persistent heavy rainfall. The accumulated rainfall from 24 June to 10 July was 232.2 mm, which comprised 42% of the mean annual rainfall. A loess slide-flow is characterized by combining two movement types of the slide and flow. The loess slide-flows first slide on the gully-slopes and then turn into long run-out earthflows moving downstream, delivering vast amounts of sediment to the river. The average landslide erosion rates were 110.8-134.9 kg/m2. These loess slide-flows generally did not occur individually but in groups,which were characterized by large numbers, high density, small scale, and shallow depth. The changes of vegetation characteristics and soil characteristics both had a significant impact on the scale of the landslides. Grass with high coverage had an adverse effect on the occurrence of shallow landslides. The adverse hydrological effects of the plant may offset the weak root reinforcement. Loess slide-flows have become a new geological hazard and erosion process on the Loess plateau. Loess slide-flows are a prominent ecological and environmental problem after vegetation restoration, and more attention should be paid to loess slide-flows in the future.

关键词： Loess plateau landslide soil erosion Vegetation Rainfall

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Sap flow characteristics and physiological adjustments of two dominant tree species in pure and mixed plantations in the semi-arid Loess plateau of China

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Journal of Arid land 2018年第6期10卷 833-849页

作者： TANG Yakun WU Xu CHEN Yunming state key laboratory of soil erosion and dry-land farming on the Loess plateau Northwest A&F UniversityYangling 712100China state key laboratory'of soil erosion and dry-land farming on the Loess plateau Institute of Soil and Water Conservation Chinese Academy of Sciences and the Ministry of Water ResourcesYangling 712100China University of Chinese Academy of Sciences Beijing 100049China

It is essential to understand the water consumption characteristics and physiological adjustments of tree species under drought conditions,as well as the effects of pure and mixed plantations on these characteristics in semi-arid regions.In this study,the normalized sap flow(SFn),leaf water potential,stomatal conductance(gs),and photosynthetic rate(Pr)were monitored for two dominant species,i.e.,Pinus tabuliformis and Hippophae rhamnoides,in both pure and mixed plantations in a semi-arid region of Chinese Loess plateau.A threshold-delay model showed that the lower rainfall thresholds(RL)for P.tabuliformis and H.rhamnoides in pure plantations were 9.6 and 11.0 mm,respectively,and the time lags(τ)after rainfall were 1.15 and 1.76 d for corresponding species,respectively.The results indicated that P.tabuliformis was more sensitive to rainfall pulse than H.rhamnoides.In addition,strong stomatal control allowed P.tabuliformis to experience low gsand Prin response to drought,while maintaining a high midday leaf water potential(Ψm).However,H.rhamnoides maintained high gsand Prat a lowΨmexpense.Therefore,P.tabuliformis and H.rhamnoides can be considered as isohydric and anisohydric species,respectively.In mixed plantation,the values of RLfor P.tabuliformis and H.rhamnoides were 6.5 and 8.9 mm,respectively;and the values ofτwere 0.86 and 1.61 d for corresponding species,respectively,which implied that mixed afforestation enhanced the rainfall pulse sensitivity for both two species,especially for P.tabuliformis.In addition,mixed afforestation significantly reduced SFn,gs,and Prfor P.tabuliformis(P<0.05),while maintaining a high leaf water potential status.However,no significant effect of mixed afforestation of H.rhamnoides was observed at the expense of leaf water potential status in response to drought.Although inconsistent physiological responses were adopted by these species,the altered water consumption characteristics,especially for P.tabuliformis indicated that the mixed afforestation requires further investigation.

关键词： normalized sap flow physiological adjustments mixed afforestation Pinus tabuliformis Hippophae rhamnoides

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Infiltration characteristics of non-aqueous phase liquids in undisturbed loessal soil cores

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Journal of Environmental Sciences 2009年第10期21卷 1424-1431页

作者： WANG Yunqiang SHAO Ming'an state key laboratory of soil erosion and dry-land farming on the Loess plateau Institute of Soil and Water Conservation Chinese Academy of Sciences Northwest A&F University Yangling 712100 China. Graduate University of Chinese Academy of Sciences Beijing 100049 China

The widespread contamination of soils and aquifers by non-aqueous phase liquids （NAPL）, such as crude oil, poses serious environmental and health hazards globally. Understanding the infiltration characteristics of NAPL in soil is crucial in mitigating or remediating soil contamination. The infiltration characteristics of crude and diesel oils into undisturbed loessal soil cores, collected in polymethyl methacrylate cylindrical columns, were investigated under a constant fluid head （3 era） of either crude oil or diesel oil. The infiltration rate of both crude and diesel oils decreased exponentially as wetting depth increased with time. soil core size and bulk density both had significant effects on NAPL infiltration through the undisturbed soil cores; a smaller core size or a greater bulk density could reduce oil penetration to depth. Compacting soil in areas susceptible to oil spills may be an effective stratage to reduce contamination. The infiltration of NAPL into soil cores was spatially anisotropic and heterogeneous, thus recording the data at four points on the soil core is a good stratage to improve the accuracy of experimental results. Our results revealed that crude and diesel oils, rather than their components, have a practical value for remediation of contaminated loessal soils.

关键词： crude oil diesel oil soil compaction soil core sample size the Loess plateau of China

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Decay stages and meteorological factors affect microbial community during leaf litter in situ decomposition

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soil Ecology Letters 2023年第3期5卷 61-73页

作者： Haixin Zhang Yimei Huang Shaoshan An Quanchao Zeng Baorong Wang Xuejuan Bai Qian Huang key laboratory of Plant Nutrition and the Agri-environment in Northwest China Ministry of AgricultureCollege of Natural Resources and EnvironmentNorthwest A&F UniversityYangling 712100China state key laboratory of soil erosion and dryland farming on the Loess plateau Institute of Soil and Water ConservationNorthwest A&F UniversityYangling712100China Huazhong Agricultural University College of Resources&EnvironmentWuhan 430070China state key laboratory of soil erosion and dryland farming on the Loess plateau Institute of Soil and Water ConservationChinese Academy of Sciences andMinistry of Water ResourcesYangling 712100China

Litter microorganisms play a crucial role in the biological decomposition in forest ecosystems;however,the coupling effect of meteorological and substrate changes on it during the different stages of leaf decomposition in situ remains unclear.Hence,according to meteorological factors dynamics,a one-year field litter of Quercus wutaishanica in situ decomposition experiment was designed for four decay stages in a warm temperate forest.Microbial community composition was characterized using Illumina sequencing of fungal ITS and bacterial 16S genes.Bacterial(6.6)and fungal(3.6)Shannon indexes were the largest after 125 days’litter decomposition(October).The relative abundance of Acidobacteria after 342 days and Bacteroidetes after 125 days were 3 and 24 times higher than after 31 days,respectively.Some non-dominant species(bacteria:Firmicutes,Planctomycotes,and Verrucomicrobia;fungi:Chytridiomycota and Glomeromomycota)may be absent or present at different decomposition stages due to litter properties or meteorological factors.Chemoheterotrophy and aerobic-chemoheterotrophy were the dominant bacterial functional groups,and the dominant fungal functional groups were saprotrophs,pathotrophs,and symbiotrophs.Precipitation and relative humidity significantly affected bacteria.Temperature,sunlight intensity,and net radiation significantly affected fungi.Besides,among the relative contributions of changes in bacterial and fungal community structure,leaf litter properties alone explained the variation of 5.51%and 10.63%.Microbial diversity and decay stage directly affected the litter mass-loss rate,with meteorological factors(precipitation,relative humidity,air temperature,and sunlight intensity)being indirect.Our findings highlight the importance of microbial diversity for leaf litter decomposition and the influence of meteorological factors.

关键词： leaf litter decomposition microbial community composition meteorological factors Loess plateau Quercus wutaishanica

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Improving water-use efficiency by decreasing stomatal conductance and transpiration rate to maintain higher ear photosynthetic rate in drought-resistant wheat

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The Crop Journal 2017年第3期5卷 231-239页

作者： Yuping Li Hongbing Li Yuanyuan Li Suiqi Zhang state key laboratory of soil erosion and dryland farming on the Loess plateau Northwest A&F University state key laboratory of soil erosion and dryland farming on the Loess plateau Institute of Soil and Water Conservation Chinese Academy of Sciences and Ministry of Water Resources

In wheat, the ear is one of the main photosynthetic contributors to grain filling under drought stress conditions. In order to determine the relationship between stomatal characteristics and plant drought resistance, photosynthetic and stomatal characteristics and water use efficiency(WUE) were studied in two wheat cultivars: the drought-resistant cultivar ‘Changhan 58' and the drought-sensitive cultivar ‘Xinong 9871'. Plants of both cultivars were grown in pot conditions under well-watered(WW) and water-stressed(WS) conditions. In both water regimes,‘Changhan 58' showed a significantly higher ear photosynthetic rate with a lower rate of variation and a significantly higher percentage variation of transpiration compared to control plants at the heading stage under WS conditions than did ‘Xinong 9871' plants. Moreover,‘Changhan 58' showed lower stomatal density(SD) and higher stomatal area per unit organ area(A) under both water conditions. Water stress decreased SD, A, and stomatal width(SW), and increased stomatal length in flag leaves(upper and lower surfaces) and ear organs(awn, glume,lemma, and palea), with the changes more pronounced in ear organs than in flag leaves.Instantaneous WUE increased slightly, while integral WUE improved significantly in both cultivars. Integral WUE was higher in ‘Changhan 58', and increased by a greater amount, than in‘Xinong 9871'. These results suggest that drought resistance in ‘Changhan 58' is regulated by stomatal characteristics through a decrease in transpiration rate in order to improve integral WUE and photosynthetic performance, and through sustaining a higher ear photosynthetic rate, therefore enhancing overall drought-resistance.

关键词： Wheat Stomatal structure Ear photosynthesis Drought resistance Water use efficiency

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Changes in diversity,composition and assembly processes of soil microbial communities during Robinia pseudoacacia L.restoration on the Loess plateau,China

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Journal of Arid land 2022年第5期14卷 561-575页

作者： WANG Kun WANG Xiaoxia FEI Hongyan WAN Chuanyu HAN Fengpeng state key laboratory of soil erosion and dryland farming on the Loess plateau College of Natural Resources and EnvironmentNorthwest A&F UniversityYangling 712100China Research Center on soil&Water Conservation Institute of Soil and Water ConservationChinese Academy of Sciences and Ministry of Water ResourcesYangling 712100China

Robinia pseudoacacia L.(RP)restoration has increased vegetation cover in semi-arid regions on the Loess plateau of China,but ecological problems have also occurred due to RP restoration,such as reduced soil moisture.Further,it is still uncertain how microbial diversity,composition and assembly processes change with RP restoration in semi-arid regions.Therefore,amplicon sequencing of small subunit ribosomal ribonucleic acid(16S rRNA)and internal transcribed spacer(ITS)genes was performed to study soil bacterial and fungal diversity,composition and assembly processes at four study sites with different stand ages of RP plantations(Y10,RP plantation with stand ages less than 10 a;Y15,RP plantation with stand ages approximately 15 a;Y25,RP plantation with stand ages approximately 25 a;and Y40,RP plantation with stand ages approximately 40 a)along a 40-a chronosequence on the Loess plateau.The diversity of soil bacteria and fungi increased significantly during the restoration period from 10 to 15 a(Psoil bacterial communities were mainly related to changes in soil total nitrogen,nitrate nitrogen and moisture contents,while soil fungal communities were mainly shaped by soil organic carbon and nitrate nitrogen contents.Bacterial communities were structured by the heterogeneous selection and stochastic process,while fungal communities were structured primarily by the stochastic process.The RP restoration induced an increase in the relative importance of heterogeneous selection on bacterial communities.Overall,this study reveals the changes in microbial diversity,community comp

关键词： Robinia pseudoacacia microbial diversity community structure community assembly restoration semi-arid regions

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Changes in soil free-living diazotrophic community and co-occurrence patterns along desert wetland degradation gradient in the Mu Us Desert,northern China

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Pedosphere 2023年第4期33卷 638-648页

作者： Kun WANG Hongyan FEI Qian TONG Chuanyu WAN Ruopeng PAN Fengpeng HAN state key laboratory of soil erosion and dryland farming on the Loess plateau College of Natural Resources and EnvironmentNorthwest A&F UniversityShaanxi 712100(China) Research Center on soil&Water Conservation Institute of Soil and Water ConservationChinese Academy of Sciences and Ministry of Water ResourcesShaanxi 712100(China)

Climate change and human activity have led to the degradation of desert wetlands.Free-living diazotrophs are vital for soil nitrogen input.However,a comprehensive understanding of how soil free-living diazotrophic communities and their co-occurrence patterns respond to desert wetland degradation is lacking.Here,quantitative polymerase chain reaction(qPCR),amplicon sequencing targeting nitrogenase gene(nifH),and network analysis were used to investigate the abundance,diversity,community composition,and co-occurrence patterns of soil free-living diazotrophs along the wetland degradation gradient,i.e.,non-degraded(ND),lightly degraded(LD),moderately degraded(MD),and severely degraded(SD),in the southeastern Mu Us Desert,northern China.The abundance and Shannon,Simpson,Chao 1,and ACE indexes decreased(Pland,whereas no significant difference(P>0.05)was observed between ND and LD wetlands.The relative abundance of Proteobacteria generally decreased(by 53.5%–19.7%)across the different degradation levels,while the relative abundance of Cyanobacteria increased(by 6.2%–40.1%)from ND to MD levels.The abundance,diversity,and community composition of diazotrophs were most strongly related to soil organic carbon,followed by total nitrogen,moisture,and pH.The least number of network nodes and edges and the lowest density were observed for MD and SD wetlands,indicating that the complexity of free-living diazotrophic networks was reduced by continued degeneration.Overall,severe desert wetland degradation affected the abundance,diversity,and network complexity of soil free-living diazotrophs more negatively than light degradation.This degradation promoted the growth of autotrophic diazotrophs and inhibited the growth of heterotrophic diazotrophs.These changes were mostly related to the loss of soil organic carbon.

关键词： amplicon sequencing biological nitrogen fixation co-occurrence network analysis nifH gene quantitative polymerase chain reaction soil organic carbon

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Manipulated precipitation regulated carbon and phosphorus limitations of microbial metabolisms in a temperate grassland on the Loess plateau,China

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Journal of Arid land 2022年第10期14卷 1109-1123页

作者： HAI Xuying LI Jiwei LIU Yulin WU Jianzhao LI Jianping SHANGGUAN Zhouping DENG Lei state key laboratory for soil erosion and dryland farming on the Loess plateau Institute of Soil and Water ConservationNorthwest A&F UniversityYangling 712100China Institute of soil and Water Conservation Chinese Academy of Science and Ministry of Water ResourcesYangling 712100China School of Agriculture Ningxia UniversityYinchuan 750021China

Manipulated precipitation patterns can profoundly influence the metabolism of soil microorganisms.However,the responses of soil organic carbon(SOC)and nutrient turnover to microbial metabolic limitation under changing precipitation conditions remain unclear in semi-arid ecosystems.This study measured the potential activities of enzymes associated with carbon(C:β-1,4-glucosidase(BG)andβ-D-cellobiosidase(CBH)),nitrogen(N:β-1,4-N-acetylglucosaminidase(NAG)and L-leucine aminopeptidase(LAP))and phosphorus(P:alkaline phosphatase(AP))acquisition,to quantify soil microbial metabolic limitations using enzymatic stoichiometry,and then identify the implications for soil microbial metabolic limitations and carbon use efficiency(CUE)under decreased precipitation by 50%(DP)and increased precipitation by 50%(IP)in a temperate grassland.The results showed that soil C and P were the major elements limiting soil microbial metabolism in temperate grasslands.There was a strong positive dependence between microbial C and P limitations under manipulated precipitation.Microbial metabolism limitation was promoted by DP treatment but reversed by IP treatment.Moreover,CUE was inhibited by DP treatment but promoted by IP treatment.soil microbial metabolism limitation was mainly regulated by soil moisture and soil C,N,and P stoichiometry,followed by available nutrients(i.e.,NO^(-)_(3),NH^(+)_(4),and dissolved organic C)and microbial biomass(i.e.,MBC and MBN).Overall,these findings highlight the potential role of changing precipitation in regulating ecosystem C turnover by limiting microbial metabolism and CUE in temperate grassland ecosystems.

关键词： carbon use efficiency ecoenzymatic stoichiometry microbial metabolic limitations semi-arid ecosystems soil organic carbon

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Effects of freeze-thaw on soil erosion processes and sediment selectivity under simulated rainfall

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Journal of Arid land 2017年第2期9卷 234-243页

作者： WANG Tian LI Peng REN Zongping XU Guoce LI Zhanbin YANG Yuanyuan TANG Shanshan YAO Jingwei state key laboratory Base of Eco-Hydraulic Engineering in Arid Area Xi’an University of Technology state key laboratory of soil erosion and dry-land farming on the Loess plateau Institute of Soil and Water ConservationChinese Academy of Sciences and Ministry of Water Resources

The freeze-thaw （FT） processes affect an area of 46.3% in China. It is essential for soil and water conservation and ecological construction to elucidate the mechanisms of the FF processes and its associated soil erosion processes. In this research, we designed the control simulation experiments to promote the understanding of FT-water combined erosion processes. The results showed that the runoff of freeze-thaw slope （FTS） decreased by 8% compared to the control slope （CS）, and the total sediment yield of the FTS was 1.10 times that of the CS. The sediment yield rate from the FTS was significantly greater than that from the CS after 9 min of runoff （P〈0.01）. Both in FTS and CS treatments, the relationships between cumulative runoff and sediment yield can be fitted well with power functions （R2〉0.98, P〈0.01）. Significant differences in the mean weight diameter （MWD） values of particles were between the CS and the FTS treatments in the erosion were smaller than those under FTS for both washed and observed for washed particles and splashed particles process （P〈0.05）. The mean MWD values under CS splashed particles. The ratio of the absolute value of a regression coefficient between the CS and the FTS was 1.15, being roughly correspondent with the ratio of K between the two treatments. Therefore, the parameter a of the power function between cumulative runoff and sediment yield could be an acceptable indicator for expressing the soil erodibility. In conclusion, the FTS exhibited an increase in soil erosion compared to the CS.

关键词： freeze-thaw erosion loess soil soil erodibility runoff sediment size-selectivity rainfall simulation

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