Remote Sensing And GIS-based Evaluation Of Soil Erosion Risks And Ecological Management In Hickory Plantations

In the past three decades,rapid expansion of Hickory(Carya cathayensis)plantations with improper management in the hilly and mountainous region in Zhejiang Province has caused many serious environmental problems,such as soil erosion,land degradation,which have brought severe challenges to ecological environment protection.It is necessary to accurately predict soil erosion risks distribution to provide fundamental resources for making better decisions for ecological management of existing Hickory plantations.The Revised Universal Soil Loss Equation(RUSLE)is the most extensively used model for soil erosion estimation in different ecosystems.But the RUSLE was initially developed for agricultural ecosystems with gentle slopes.When RUSLE is used in hilly or mountainous regions,some errors often occurred.Therefore,the objective of this research was to develop an approach that can effectively predict the soil erosion risks using remote sensing and GIS technologies to provide the advice for ecological management in Hickory plantations.This research selected midwestern Lin'an district,Hangzhou prefecture-level city,as study area.Firstly,employed Landsat imagery,weather station data,soil-type maps,digital elevation model data,and for extraction of 47 potential variables included land cover,precipitation,soil,topography.Secondly,identified key variables of soil erosion risk using field survey data.Then,mapped soil erosion risks using the key variables based random forest approach.Finally,analyzed the soil erosion risk distribution and ecological management in hickory plantations.The results showed that:(1)it used the random forest approach to identify eight key variables—slope,normalized difference greenness index at leaf-on season,slope change rate,soil organic matter,fractional vegetation at leaf-on season,fractional soil at leaf-off season,precipitation in June,and percent of soil clay—for mapping soil erosion risk distribution in hickory plantations.(2)an overall accuracy of 89.8%was obtained for three levels of soil erosion risk.The soil erosion risk can be divided into three levels,namely,the high risk,medium risk,and low risk.The areas are 83.5 km~2?136.1 km~2?105.9 km~2,and account for 25.7%,41.8%,32.5%,respectively of hickory plantations.And the young hickory plantations have a higher risk of soil erosion than mature hickory plantations.In the process of planting and management in hickory plantations,it is necessary to achieve the purpose of controlling the runoff,improving the surface coverage and soil stability and ultimately reducing the risk of soil erosion through the combination of engineering measures,plant measures and management measures.This research provides a new approach to predict soil erosion risk in hickory plantations.This proposed approach will be valuable for other subtropical agroforestry and plantations,such as Torreya grandis,eucalyptus,that are playing important roles in improving economic conditions for the local farmers but face soil erosion problems.