Protection Policy Responses To Soil Erosion Of Alpine Grassland In The Three-river Head Water Area

Since ancient times,the three-river head-water area,called"Chinese water tower",is the origin of many rivers and lakes.At the same time,the grassland covers a vast area,with an average altitude of more than 4300 meters,which makes the surface vegetation mainly with wetland and alpine meadow.There is become the most important part of the high cold grassland ecosystem in China.However,due to the frequent disturbances of special land forms,climate impacts and human activities,the problem of grassland degradation has been escalating and soil erosion has intensified.The state has implemented a series of protection policies to ensure grassland ecosystem restoration,but the evaluation system for grassland protection policy is still lacking.This study takes the three-river head water as the research area and 310 soil samples in the field.¹³⁷Cs field measurement data,revised universal soil loss equation and universal soil loss equation based on GIS,the temporal and spatial variation characteristics of soil erosion in the three-river head-water area from 1986 to 2015 years before and after the establishment of the three-river head water nature reserve.The main results are as follows:?1?The revised universal soil loss model is still one of practical choices to study the soil erosion model of grassland in the three-river head water area.The revised universal soil loss model's MBE is14.28,less than the universal soil loss model's MBE 267.29.The universal soil loss model's CVRMSE is 59.85?more than 30 percentage?.The revised universal soil loss model's CVRMSE is 8.48?less than10 percentage?.The universal soil loss model's E is-1.81,and the revised universal soil loss model's is0.94.The accuracy index of the above three evaluation models:the soil erosion modulus estimated by the universal soil loss model is generally less than that of the revised universal soil loss model.?2?The extent of the soil erosion is generally lighter from 1986 to 2015 years.The area of the slight erosion is decreasing,and the area of high erosion is increasing.The soil erosion amount is 4.8x10⁷t/a before the establishment of the protection zone,and it is 5.8x10⁷t/a after the establishment of the protection zone.The erosion amount increased 1.0x10⁷ t/a.The erosion amount reduced in grade II,III,IV and V,and the area of grade I and VI increased.The grade I is 86 percentage which is reclassified.The area of soil erosion modulus from 0 to 50[t/?km²·a?]and 200 to 2500[t/?km²·a?]showed a downward trend;the area of soil erosion modulus from 50 to 200[t/?km²·a?]and more than2500[t/?km²·a?]showed increased trend.?3?The influences of NDVI,the rainfall erosion and protection policies on the soil erosion increased step by step.in the study area.It is suggested to adopt classification,subsection and district treatment measures.The implementation,supervision and management of protected areas should be strengthened,and we also should do a good job in improving vegetation coverage.Such as Geermu township,Maqin county,Qumalai county,Maduo county and Jiuzhi county areas where soil erosion is aggravated.We should focus on restoring areas where erosion increases,while strengthening the areas where erosion is reduced.Such as Zhiduo county,Nangqian county,Xinghai county,Dari county,Zaduo county and Yushu township.