| Soil erosion is becoming a serious ecological and environmental problem in China and even the world,which has resulted in a series of negative influences on environment,such as land productivity descent,river pollution,ecological imbalance,and severely affected the social and economic sustainable development.Vegetation is an effective measure to control soil erosion.For the riparian zone,vegetation patches serve significant function to intercept runoff,reduce sediment,improve water quality and retain soil and water.However,with the development of urbanization and industrialization,riparian vegetation buffer zone has been severely damaged,which changed the function of the riparian vegetation buffer in water and soil conservation.Therefore,the 10 km riparian vegetation buffer zone along the mainstream of Beijiang River was selected as the object.Leakiness index?LI?,an indicator reflecting the relationship between landscape pattern and soil erosion,was applied to carry out the research on regulating soil and water conservation function of the Beijiang riparian vegetation buffer zone.In the present study,firstly,we demonstrated the principle and function of LI,and then analyzed the sensitivity of LI to the riparian vegetation buffer zone of Beijiang River by using upscaling and downscaling methods.Sencondly,the applicability of LI in study area was further validated with the Universal Soil Loss Equation?USLE?model.Based on the verification result,we subsequently investigated the variation of index with different vegetation pattern.Lastly,from the perspective of vegetation and terrain,we regulated the regions of serious soil erosion with the optimal vegetation pattern.The main results are shown below:?1?The sensitivity of DEM to resolution and LI was less than that of VC and LI had the potential to be applied to the riparian vegetation buffer zone of Beijiang River.For DEM,elevation did not significantly change with decreasing resolution and the average slope decreased slightly;LI presented minimally varied with the changes in DEM.Conversely,for VC,the mean values evidently decreased and the standard deviation continuously increased with decreasing resolution.LI sharply increased from 0.217to 0.68 with decreasing VC.The performance of LI in the Beijiang riparian vegetation buffer zone was also tested.The great changes in LI values from 1995,2000,2005,2010 and 2015 indicated that LI can be used in the Beijiang riparian vegetation buffer zone with great potential.?2?LI can be used to evaluate water and soil conservation function in riparian vegetation buffer zone of Beijiang River with better applicability.In order to further verify the applicability of LI in study area.USLE model widely used in China was applied to quantitatively monitor soil erosion modulus during1995-2015,and analyzed the correlation with the evaluate results of LI.The results showed that in the 5periods,soil erosion amount was 8109.79 t·hm-2·a-1,8109.79 t·hm-2·a-1,8756.19 t·hm-2·a-1,9397.42t·hm-2·a-1,9818.31 t·hm-2·a-1,respectively.There was a similar tendency for erosion modulus and LI values.Moreover,the correlation analysis presented significant linear relationship?P=0.039?,which indicated that LI was an effective index for evaluating the function of water and soil conservation in riparian vegetation buffer zone of Beijiang River.?3?The distribution direction and aggregation degree of vegetation patches had significant effect on LI.Through the scenario simulation,we selected 4 different vegetation patterns:position,orientation,aggregation degree,and mosaic pattern in the same slope to analyze the changes in LI.For the position of vegetation patch,when vegetation was distributed in the upper,middle and lower of slope,the value reached the minimum for lower position and soil and water conservation function was strongest.For the orientation of vegetation patch,when the vegetation patch was horizontal,vertical and grid-like distribution,LI value was 0.115,0.154 and 0.124,respectively.There was little difference for the horizontal and grid-like distribution,while the function of soil and water conservation was weak for vertical distribution.For the aggregation degree of vegetation patch,when vegetation was cluster distribution,LI value was0.183.The value was a little lower,0.161 when the vegetation was scattered.The soil and water conservation function was stronger with scattered distribution than that with cluster distribution.For the different mosaic pattern,LI value was 0.418 with the high fragmentation.The value reached 0.440 with relative low fragmentation.Based on the variation of LI in different scenarios,the orientation and aggregation degree of vegetation patch had more obvious impact on LI.?4?After the vegetation pattern regulation for the targeted regions,capacity of soil and water conservation reached a high level.The soil and water conservation function of riparian vegetation buffer of Beijiang River was medium with the value of 0.228 in 2015.However,the spatial variation of LI indicated that the function of soil and water conservation was lower in Shaoguan,Qingyuan,Sanshui,Sihui and Huadu?LI values were 0.455?0.459?0.527?0.507?0.418,respectively?,being the targeted regions for regulation.Based on the optimal pattern of scenario simulation,optimization solution was designed for the targeted regions to improve the function of soil and water conservation so as to optimize social and ecological benefits of riparian vegetation buffer zone.After regulation,LI values were 0.19?0.20?0.14?0.17 and 0.12,respectively with higher soil and water conservation function.The study results indicate that LI can be used in the riparian vegetation buffer of Beijiang River with better applicability,and different vegetation pattern will affect the function of soil and water conservation in riparian vegetation buffer zone through the influence on runoff path connectivity.Therefore,vegetation pattern is a better solution for regulating soil erosion.The landscape function will be optimized with reasonable arrangement of vegetation patch,which will make a favorable foundation for the effective management and sustainable development of riparian vegetation buffer zone. |
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