We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces,respectively.Each type of land was tested under a simulated moderate rainf...We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces,respectively.Each type of land was tested under a simulated moderate rainfall of 0.33 mm/min,a downfall of 0.90 mm/min,and a rainstorm of 1.86 mm/min.Runoff dynamics and changes in the export amount of phosphorus are influenced by the rainfall intensity,the slope and surface conditions of cropland.The vegetation diverts rain water from the surface into soil and helps the formation of a subsurface runoff,but has little influence on runoff process at the same sloping degree.Vegetated soil has a smaller phosphorous loss,particularly much less in the particulate form.A heavier rainfall flushes away more phosphorous.Rainwater percolating soil carries more dissolved phosphorous than particulate phosphorous.Understanding the patterns of phosphorous transport under various conditions from purple soil in the middle of Sichuan basin is helpful for developing countermeasures against non-point-source pollution resulting in the eutrophication of water bodies in this region that could,if not controlled properly,deteriorate the water quality of the Three Gorges Reservoir.展开更多
Land use and land cover change is a key driver of environmental change. To investigate the runoff and erosion responses to frequent land use change on the steep lands in the Three Gorges area, China, a rainfall simula...Land use and land cover change is a key driver of environmental change. To investigate the runoff and erosion responses to frequent land use change on the steep lands in the Three Gorges area, China, a rainfall simulation experiment was conducted in plots randomly selected at a Sloping Land Conversion Program site with three soil surface conditions: existing vegetation cover, vegetation removal, and freshly hoed. Simulated rainfall was applied at intensities of 60 (low), 90 (medium), and 120 mm h 1 (high) in each plot. The results indicated that vegetation removal and hoeing significantly changed runoff generation. The proportion of subsurface runoff in the total runoff decreased from 30.3% to 6.2% after vegetation removal. In the hoed plots, the subsurface runoff comprised 29.1% of the total runoff under low-intensity rainfall simulation and the proportion rapidly decreased with increasing rainfall intensity. Vegetation removal and tillage also significantly increased soil erosion. The average soil erosion rates from the vegetation removal and hoed plots were 3.0 and 10.2 times larger than that in the existing vegetation cover plots, respectively. These identified that both the runoff generation mechanism and soil erosion changed as a consequence of altering land use on steep lands. Thus, conservation practices with maximum vegetation cover and minimum tillage should be used to reduce surface runoff and soil erosion on steep lands.展开更多
Gully erosion is one of the most important forms of land degradation in many regions of the world.Understanding the process of gully erosion therefore is important for better management of the wa-tersheds prone to gul...Gully erosion is one of the most important forms of land degradation in many regions of the world.Understanding the process of gully erosion therefore is important for better management of the wa-tersheds prone to gully erosion.However,many different aspects of gully erosion,like hydrological behavior,are still not fully understood.The present study investigates the spatial distribution of soil moisture content(SMC),as one of the hydrological factors,at different depths and points across the cross section in the vicinity of the headcut of three gullies located in the Kalat County,Khorasan Razavi Province,Iran.SMCs were measured at depths of 10,20,30,50,70 and 100 cm at each seven points across the study cross sections one to three days after occurrence of three rain events.Two sampling points were symmetrically located at a distance of 50 cm outside the gully banks,two at the vertex of the sidewalls,two in the middle of the sidewalls and one at the center of gully cross section.SMCs were measured using a weighted method.Results of the study revealed a broad range of changes in SMCs at various depths and points.The minimum and maximum SMCs were found to be about 2%and 38%,respectively,for the study period and gullies under consideration.The coefficient of variation(CV)had drastic changes for various gullies and storm events from 2 to 107%.Results further indicated that SMC moved from the sidewalls towards the floor of the cross section.Accordingly,the maximum SMC for storm events was associated with the point located in the center of gullies,which indicated the role of gully system in draining soil moisture.The findings of this study will help watershed managers un-derstand the important role of gully facies in changing water content of the soil that affects other eco-hydrological processes.展开更多
An empirical simulation method to simulate the possible position of shallow rainfall-induced landslides in China has been developed.This study shows that such a simulation may be operated in real-time to highlight tho...An empirical simulation method to simulate the possible position of shallow rainfall-induced landslides in China has been developed.This study shows that such a simulation may be operated in real-time to highlight those areas that are highly prone to rainfall-induced landslides on the basis of the landslide susceptibility index and the rainfall intensity-duration(I-D) thresholds.First,the study on landslide susceptibility in China is introduced.The entire territory has been classified into five categories,among which high-susceptibility regions(Zone 4-'High' and 5-'Very high') account for 4.15%of the total extension of China.Second,rainfall is considered as an external triggering factor that may induce landslide initiation.Real-time satellite-based TMPA3B42 products may provide real rainfall spatial and temporal patterns,which may be used to derive rainfall duration time and intensity.By using a historical record of 60 significant past landslides,the rainfall I-D equation has been calibrated.The rainfall duration time that may trigger a landslide has resulted between 3 hours and 45 hours.The combination of these two aspects can be exploited to simulate the spatiotemporal distribution of rainfall-induced landslide hazards when rainfall events exceed the rainfall I-D thresholds,where the susceptibility category is 'high' or 'very high'.This study shows a useful tool to be part of a systematic landslide simulation methodology,potentially providing useful information for a theoretical basis and practical guide for landslide prediction and mitigation throughout China.展开更多
基金the Natural Science Foundation of China (No. 40571093)the National Field Station Fund
文摘We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces,respectively.Each type of land was tested under a simulated moderate rainfall of 0.33 mm/min,a downfall of 0.90 mm/min,and a rainstorm of 1.86 mm/min.Runoff dynamics and changes in the export amount of phosphorus are influenced by the rainfall intensity,the slope and surface conditions of cropland.The vegetation diverts rain water from the surface into soil and helps the formation of a subsurface runoff,but has little influence on runoff process at the same sloping degree.Vegetated soil has a smaller phosphorous loss,particularly much less in the particulate form.A heavier rainfall flushes away more phosphorous.Rainwater percolating soil carries more dissolved phosphorous than particulate phosphorous.Understanding the patterns of phosphorous transport under various conditions from purple soil in the middle of Sichuan basin is helpful for developing countermeasures against non-point-source pollution resulting in the eutrophication of water bodies in this region that could,if not controlled properly,deteriorate the water quality of the Three Gorges Reservoir.
基金Supported by the National Natural Science Foundation of China (Nos. 41171223 and 41001164)the Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology of China
文摘Land use and land cover change is a key driver of environmental change. To investigate the runoff and erosion responses to frequent land use change on the steep lands in the Three Gorges area, China, a rainfall simulation experiment was conducted in plots randomly selected at a Sloping Land Conversion Program site with three soil surface conditions: existing vegetation cover, vegetation removal, and freshly hoed. Simulated rainfall was applied at intensities of 60 (low), 90 (medium), and 120 mm h 1 (high) in each plot. The results indicated that vegetation removal and hoeing significantly changed runoff generation. The proportion of subsurface runoff in the total runoff decreased from 30.3% to 6.2% after vegetation removal. In the hoed plots, the subsurface runoff comprised 29.1% of the total runoff under low-intensity rainfall simulation and the proportion rapidly decreased with increasing rainfall intensity. Vegetation removal and tillage also significantly increased soil erosion. The average soil erosion rates from the vegetation removal and hoed plots were 3.0 and 10.2 times larger than that in the existing vegetation cover plots, respectively. These identified that both the runoff generation mechanism and soil erosion changed as a consequence of altering land use on steep lands. Thus, conservation practices with maximum vegetation cover and minimum tillage should be used to reduce surface runoff and soil erosion on steep lands.
基金The present manuscript has been partially supported by the Agrohydrology Research Group of Tarbiat Modares University(grant IG-39713),Iran,concerning the corresponding author
文摘Gully erosion is one of the most important forms of land degradation in many regions of the world.Understanding the process of gully erosion therefore is important for better management of the wa-tersheds prone to gully erosion.However,many different aspects of gully erosion,like hydrological behavior,are still not fully understood.The present study investigates the spatial distribution of soil moisture content(SMC),as one of the hydrological factors,at different depths and points across the cross section in the vicinity of the headcut of three gullies located in the Kalat County,Khorasan Razavi Province,Iran.SMCs were measured at depths of 10,20,30,50,70 and 100 cm at each seven points across the study cross sections one to three days after occurrence of three rain events.Two sampling points were symmetrically located at a distance of 50 cm outside the gully banks,two at the vertex of the sidewalls,two in the middle of the sidewalls and one at the center of gully cross section.SMCs were measured using a weighted method.Results of the study revealed a broad range of changes in SMCs at various depths and points.The minimum and maximum SMCs were found to be about 2%and 38%,respectively,for the study period and gullies under consideration.The coefficient of variation(CV)had drastic changes for various gullies and storm events from 2 to 107%.Results further indicated that SMC moved from the sidewalls towards the floor of the cross section.Accordingly,the maximum SMC for storm events was associated with the point located in the center of gullies,which indicated the role of gully system in draining soil moisture.The findings of this study will help watershed managers un-derstand the important role of gully facies in changing water content of the soil that affects other eco-hydrological processes.
基金supported by the National Natural Science Foundation of China(Grant No.41501458)China Postdoctoral Science Foundation Funded Project(Grant No.2016M592860)+4 种基金National Basic Research Program of China(Grant No.2013CB733204)Key Laboratory of Mining Spatial Information Technology of NASMG(Grant Nos. KLM201309)Science Program of Shanghai Normal University(Grant No. SK201525)the Shanghai Gaofeng & Gaoyuan Project for University Academic Program Development(Grant Nos.2013LASW-A09 & SKHL1310)the Center of Spatial Information Science and Sustainable Development Applications,Tongji University,Shanghai,China
文摘An empirical simulation method to simulate the possible position of shallow rainfall-induced landslides in China has been developed.This study shows that such a simulation may be operated in real-time to highlight those areas that are highly prone to rainfall-induced landslides on the basis of the landslide susceptibility index and the rainfall intensity-duration(I-D) thresholds.First,the study on landslide susceptibility in China is introduced.The entire territory has been classified into five categories,among which high-susceptibility regions(Zone 4-'High' and 5-'Very high') account for 4.15%of the total extension of China.Second,rainfall is considered as an external triggering factor that may induce landslide initiation.Real-time satellite-based TMPA3B42 products may provide real rainfall spatial and temporal patterns,which may be used to derive rainfall duration time and intensity.By using a historical record of 60 significant past landslides,the rainfall I-D equation has been calibrated.The rainfall duration time that may trigger a landslide has resulted between 3 hours and 45 hours.The combination of these two aspects can be exploited to simulate the spatiotemporal distribution of rainfall-induced landslide hazards when rainfall events exceed the rainfall I-D thresholds,where the susceptibility category is 'high' or 'very high'.This study shows a useful tool to be part of a systematic landslide simulation methodology,potentially providing useful information for a theoretical basis and practical guide for landslide prediction and mitigation throughout China.
