Ecological Effects And Pattern Optimization Of The Reclamation Of Saline-alkali Land In West Jilin Province

Land salinization is one of the main threats restricting the sustainable development of irrigated agriculture.It not only affects regional food production capacity,but also seriously harms the ecological environment.Areas with severe primary salinization problems are mostly distributed in arid or semi-arid areas,and their ecological environment is inherently fragile.In the process of reclamation,if conditions such as water and soil resources and topography are ignored,secondary salinization will occur,which is counterproductive and produces negative effects on the ecological environment.Therefore,the reclamation of saline-alkali land should be tailored to local conditions,accurately guided,and objectively and quantitatively assessed the changes in the ecological environment before and after reclamation,so as to scientifically and rationally formulate the construction sequence and layout of saline-alkali land reclamation projects to promote regional water-soil balance and water-salt balance.This study took the typical secondary saline-alkali soil area Zhenlai County in the west of Jilin Province as the research area,and took the ecological effects of five saline-alkali land reclamation methods as the main research object.Based on the quantity and spatial transfer status of the saline-alkali land and other land use types,this paper adopted the equivalent factor method to estimate the variations of ecosystem services value of different types of saline-alkali land reclamation,and optimized the future reclamation pattern of the saline-alkali land according to the spatial difference in the supply and demand of the ecosystem services to provide a basis for ecological restoration of territorial space of soda saline-alkaline soil area in Northeast China.The main research conclusions are as follows:(1)During 2009-2018,the research area reclaimed about 40,900 hectares of saline-alkali land resources,accounting for 46.40% of the total area of saline-alkali land at the beginning of the period,and they mainly converted to paddy field,wetland,waterbody,grassland,or rain-fed land.The central and western regions of the county had a relatively high degree of reclamation,and the types of reclamation were relatively abundant.Due to resource endowment restrictions,the types of wetland and water areas were usually distributed in close proximity.The barycenter of saline-alkali land migrated to the southwest during the study period,and the highest nuclear density decreased from 25 to12.(2)During the study period,the reclamation of saline-alkali land in Zhenlai County could increase ESV by 935 million yuan and the conversion to wetland or waterbody were the main contributors because of the significant improvement in water supply and environmental purification functions.Moreover,the conversion to paddy field could exert adverse effects on water supply and soil retention to a certain extent.In terms of spatial distribution,the conversion to wetland in Momoge Mongolian Township brought the most significant increase in ESV.The conversion to paddy field in Tantu Town reduced ESV to a certain extent.(3)This paper used the ecosystem services value to characterize the supply level of ecosystem services in the study area,and used land use intensity,ESV per capita,GDP per area,proximity to water sources,and rural per capita net income to calculate the demand of ecosystem services in the region.According to the spatial difference of ecosystem service supply and demand,the study area was divided into wetland development hotspot,paddy field development potential area,ecological supply-demand balance area and ecological protection area.The proposed construction sequence was to prioritize the development of wetland development hotspot and paddy field development potential area.As the direction of reclamation,it was recommended to develop and remediate artificial wetland projects in areas with a large gap in the supply of ecosystem services and obvious geographical advantages in water resources such as Wukeshu Town.For areas where the supply of ecosystem services exceeds demand,such as Yanjiang Town,this paper recommended that paddy field development should be appropriately selected according to local conditions.Areas where the supply and demand of ecosystem services are relatively balanced or "high supply-high demand" could be appropriately developed and protected according to the local water supply situation.(4)To provide a more accurate basis for the scientific guidance of the reclamation and utilization protection mode of territorial space in ecologically fragile areas,this paper corrected the mismatch between the supply and demand of regional ecosystem services caused by the reclamation of saline-alkali land.On this basis,we could more accurately manage the timing and layout of saline-alkali land reclamation projects.