Evaluation Of Small Watersheds Ecosystem Service Functions Based On InVEST Model In The Loess Alpine Region

Based on field investigations,indoor experiments,and ArcGIS processing,this article uses the InVEST model to build a parameter database for the evaluation of small watersheds ecosystem service functions in 3 small watersheds(Yangjiazhai,Anmentan,Talgou)of Loess Alpine.This study assessed the soil conservation function and water supply function of three small watersheds at different afforestation stages.The consider analyzed the two service functions’level of different forest vegetation types.Overlay two service functions to analyze ecosystem services of small watersheds.Based on the evaluation results the writer proposed small watersheds’management and reconstruction measures in order to enhance the ecosystem service function value of vegetation in the Loess Alpine Region of Qinghai province,and solve the society’s multi-functional demand for vegetation,such as water conservation,solid soil and water supply on this region.The important results and conclusions of this study are as follows.(1)The calculation method of this index is determined according to the actual situation of the study area.Wischmeier monthly scale formula was used to calculate the rainfall erosivity factor,the vegetation cover factor segment calculation formula proposed by Cai Chongfa and others was used to calculate the vegetation cover factor value,and Modified-Hargreaves method was used to calculate the potential evapotranspiration,selecting non-defined fitting the soil PAWC estimation model to estimate the available water content of the plant,and the Z value of the three small watersheds using the formula of the number of rainfalls.(2)The study evaluated the soil conservation and water supply functions of three small watersheds in the study area.On account of the soil erosion modulus of the small watershed,it is concluded that the Yangjiazhai small watershed is mildly eroded,and the erosion degree of the Taergou and Anmentan is slightly eroded.At the watershed level,the order of soil conservation per unit area is Anmentan(554.28t/hm~2)>Yangjiazhai(526.17 t/hm~2)>Taergou(412.13 t/hm~2).At land use types,the amount of soil per unit area of rural homestead is the largest,and that of bare land is the lowest.At vegetation types,The soil retention effect of mixed forest land is better than that of pure forest land.The water supply of the three small watersheds is ranked as Anmentan(255.36 mm)>Yangjiazhai(228.07 mm)>Taergou(226.34 mm),at land use type,forest land water volume is higher than several other land types,and at vegetation type,coniferous forest land has higher water production than broad-leaved forest land.(3)The important values of the ecosystem service functions of the three small watersheds are Anmentan(0.49)>Yangjiazhai(0.48)>Talgou(0.44).The important value of the forest vegetation ecosystem services is Taergou(0.62)>Anmentan(0.60)>Yangjiazhai(0.56).The ecosystem service value of forest vegetation in Taergou small watershed is the largest.The current status and development trends of three afforestation small watersheds at different stages have proposed adjustment and transformation measures in terms of land use and forest vegetation types.