Study On The Spatial Selection Of Returning Farmland To Forest Based On Ecological Benefit Assessment

As the largest ecological compensation project in China,the project of returning farmland to forest is an important step in the construction of ecological civilization.It can effectively alleviate the ecological and environmental problems that arise during the process of rapid social and economic development.Clarifying the ecological benefits of the project of returning farmland to forest and accurately identifying the space for returning farmland to forest will help consolidate the achievements of the project and provide a basis for the next round of the project of returning farmland to forest.Therefore,this paper first evaluated the ecosystem services in the Gansu section of the Weihe River in 2000,2010,and 2020,and analyzed the impact of the farmland conversion project on the ecosystem services in the study area.Then,the project area for converting farmland to forest was determined based on both the slope method and the cultivated land suitability method,respectively.The ecosystem services after the implementation of both methods were evaluated,and the comprehensive index of ecosystem services under both methods was calculated.Finally,using the ecosystem services in 2020 as the baseline,the amount of newly added ecosystem services and the corresponding comprehensive ecosystem service index under both methods were compared and analyzed.The results show that:(1)From 2000 to 2020,the ecosystem services in the Gansu section of the Weihe River were enhanced due to the influence of land use change.Between 2000 and2010,water conservation services increased by 0.78%;Soil conservation services increased by 0.55%.Water quality(nitrogen and phosphorus)purification services increased by 2.29%and 4.79%,respectively;Habitat quality services increased by0.33%.Between 2010 and 2020,water conservation services increased by 0.07%;Soil conservation services increased by 0.04%;Water quality(nitrogen and phosphorus)purification services increased by 0.32%and 1.77%,respectively;Habitat quality services increased by 0.47%.(2)From 2000 to 2020,the ecosystem services of the project of returning farmland to forest area were also enhanced,and the enhancement range was much greater than that of the study area.Between 2000 and 2010,water conservation services increased by 32.29%;Soil conservation services increased by 1.92%;Water quality(nitrogen and phosphorus)purification services increased by 36.17%and61.58%,respectively;Habitat quality services increased by 52.80%.Between 2000and 2020,water conservation services increased by 71.72%;Soil conservation services increased by 3.57%;Water quality(nitrogen and phosphorus)purification services increased by 71.19%and 66.67%,respectively;Habitat quality services increased by 43.38%.(3)Based on the slope method,the space area for returning farmland to forest in the Gansu section of the Weihe River is 41137.56 hm~2,with a slope of over 25°,the high suitability of farmland is 0.4112.Based on the same area of returning farmland to forest,the space area for returning farmland to forest with the selection of cultivated land suitability was distributed in the three ranges of 0～15°,15～25°and above 25°.Among them,the space for returning farmland to forest above 25°accounted for the largest proportion(56.52%),followed by 15～25°(38.29%)and 0～15°was the least(5.19%).The farmland suitability is lower at 0.3953.(4)Compared to 2020,the space for returning farmland to forest in the Gansu section of the Weihe River was selected based on the farmland suitability and slope method,resulting in enhanced ecosystem services after simulated conversion.Among them,based on the selection of farmland suitability,the comprehensive index of newly added ecosystem services after farmland conversion simulated was 0.0119.However,based on the selection of slope method,the comprehensive index of newly added ecosystem services after farmland conversion simulated was 0.0104.The former was 14.42%higher than the latter.This indicates that the space for returning farmland to forest based on the farmland suitability method is more conducive to the comprehensive maximization of ecological benefits in the study area.