Evaluation Of The Function Of Ecosystem Services Of Three-North Shelterbelt Project In Northern Shaanxi

The Three North Shelter Forest Project is a large-scale artificial forestry ecological project started in 1978 to improve the ecological environment in China.The overall plan for the construction of the Three North Shelter Forest is divided into three stages and eight periods,which lasted 73 years and are currently in the fifth period.To explore the construction and environmental benefits of the Three North Shelter Forest Project in northern Shaanxi in the past 40 years,this paper takes the northern Shaanxi Shelter Forest System as the research object,collected and organized the data of 1980,1990,2000,2010 and 2018.Analysis and discussion on the changes of forest area and coverage in northern Shaanxi,variation characteristics of soil main nutrients in shelter forest and characteristics of ecosystem service function value changes,Analysis and discussion on the changes of forest area and coverage in northern Shaanxi,variation characteristics of soil main nutrients in shelter forest and characteristics of ecosystem service function value changes.Aiming to provide a theoretical basis for scientifically evaluating the ecological and environmental effects of the Three North Shelter Forest construction and promoting the sustainable development of northern Shaanxi.The characteristics of the changes in forest area and coverage are based on quantitative statistical analysis methods and GIS technology to analyze the land use type data(mainly forest land type data)for 1980,1990,2000,2010,and 2018 and MODIS data for 2000,2010,and 2018,the NDVI and vegetation coverage index as indicators of forest land change;After the construction of the Three North Shelter Forest,research literature published from 1978to 2018 were selected and analyzed the change of main soil nutrients of the shelter forest system using Meta-analysis methods.Soil organic carbon(SOC),total nitrogen(TN),available phosphorus(AP)and available potassium(AK)were selected as the main soil nutrient index;Four service functions of climate regulation,water conservation,soil formation and protection,and biological diversity conservation were selected.Collected and organized the estimated data of ecosystem service functions value from 1980,1990,2000,2010 and 2018,and used the ecosystem service function value estimation model to evaluate the changes of ecosystem service function value of the northern Shaanxi after the construction of the construction of Three North Shelter Forest.Obtain the following main research results:(1)Overall,the forest land area in northern Shaanxi has increased,compared with 1980,the area of open forest,other forest and total forest land increased by 6(0.32%),347(5.36%),166(7.29%),949(518.58%)and 1468 km~2(13.61%)in 2018,respectively.From 2000 to 2018,the NDVI vegetation index and vegetation coverage index showed an upward trend.(2)From the meta-analysis results of the published research data from 1978 to 2018,it can be seen that the soil nutrient content of the shelter forest increased significantly compared with agricultural land or abandoned land.Compared with the control group,in the 0-20 cm soil layer,the content of soil organic carbon and available potassium in the shelter forest increased by 118.57%and 108.73%respectively;in the 20-40 cm soil layer,the soil total nitrogen content of the shelter forest increased by 86.19%.Soil organic carbon(104.07%),total nitrogen(130.28%)and available potassium(125.60%)in the shelter forest with planting years>30a increased the most;the soil available phosphorus of shelter forest with planting years of 0-10 years had the largest change(27.33%).Planting Pinus sylvestris var.Mongolica is beneficial to increase the content of soil organic carbon(120.86%)and available phosphorus(74.33%);Planting Pinus tabuliformis was beneficial to increase the soil total nitrogen content(73.82%),and Robinia pseudoacacia was beneficial to increase the content of soil available potassium(72.93%).(3)In general,among all ecosystem service functions,the service value of water conservation functions in 1980,1990,2000,2010 and 2018 was the highest.In terms of time scale,from 1980 to 2018,the value of service functions of climate regulation,water conservation,soil formation and protection,and biological diversity conservation showed an upward trend over time;The total value of different ecosystem service functions in 1980,1990,2000,2010,and 2018 were 11697.40×10~4,11725.40×10~4,11833.11×10~4,12805.11×10~4,and 13046.67×10~4 yuan,respectively,and the total value also showed an upward trend over time.