| China’s farmland ecosystem has a large area and high carbon storage,making it an important component of the global carbon cycle.Clarifying the carbon sequestration potential and influencing factors of China’s farmland ecosystem is of great significance for analyzing the global carbon cycle and the country’s agricultural carbon neutrality.In recent years,the country has attached great importance to the protection of agricultural ecological environment,reduction of agricultural emissions,and promotion of coordinated pollution reduction and carbon reduction in agriculture,which includes the construction of well-facility farmland to increase organic matter content and enhance the ability of agricultural ecosystems to sequester carbon.However,during the construction process,there are issues such as mismatched funding and land resources,scattered investment,and difficulty in achieving comprehensive benefits.The reason is that the well-facility farmland construction project lacks scientific guidance in site selection and planning,resulting in a significant gap between investment and expected goals.Therefore,it has become an important issue in the field of farmland carbon neutrality research to systematically carry out the evaluation of spatial suitability and stability of well-facility farmland construction and its temporal and spatial layout,as well as to conduct research on the mechanism of increasing production and carbon sequestration in agricultural ecosystems through the construction of well-facility farmland.This will provide technical support for the site selection and planning of well-facility farmland construction projects.Loess Tableland is mainly distributed in the central part of Shaanxi Province,covered by loess on the terraces of river valleys and distributed in a strip shape along the river valleys,forming alluvial deposits with fertile soil and a good foundation for agricultural development.In recent years,systematic well-facility farmland construction has been implemented,which has laid a foundation for the evaluation of spatial suitability and stability of well-facility farmland construction and the study of increased production and carbon sequestration in farmland ecosystems through well-facility farmland construction.Based on the actual situation of the Loess Tableland,this article selected nine evaluation indicators and used Geographic Information System(GIS)technology and Remote Sensing(RS)technology to conduct a systematic evaluation of the suitability of well-facility farmland construction using the Analytic Hierarchy Process(AHP).Secondly,using the Carnegie-Ames-Stanford Approach(CASA)model and soil respiration model,Landsat-8data,meteorological station data,and vegetation type data were used to estimate the Net Primary Productivity(NPP)and Net Ecosystem Productivity(NEP)of vegetation and crop yield in the Loess Tableland region.The main research content and conclusions are as follows:(1)The combination of reasonable indicators and Analytic Hierarchy Process(AHP)can accurately evaluate the suitability of well-facility farmland construction in the Loess Tableland region.The construction of well-facility farmland is constrained by multiple factors such as the natural endowment of cultivated land,field infrastructure,and long-term stability conditions.Each factor requires a suitable threshold to be set for well-facility farmland construction.In the area defined by all these thresholds,any combination of environmental resources that meets the standards for well-facility farmland construction is considered suitable.By constructing a suitability evaluation system for well-facility farmland construction and dividing the suitability levels based on the weights of each level,the suitability of farmland construction in different regions is clarified.The research results show that although the terrain and landform conditions in the Loess Tableland are complex,the overall natural endowment of cultivated land is good,and the suitability is high.The areas very suitable(I)and suitable(II)for well-facility farmland construction cover11,312.57 km~2,accounting for 88.38%of the total area.The analysis of the suitability of each indicator shows that slope and contiguous cultivated land area are key factors affecting well-facility farmland construction in the Loess Tableland.As slope increases,the area very suitable for construction gradually decreases,while the area unsuitable for construction increases.(2)Remote sensing methods can accurately simulate the carbon sequestration potential and crop yield of farmland ecosystems in the Loess Tableland region.Based on the Carnegie-Ames-Stanford Approach(CASA)model,the Net Primary Productivity(NPP)of vegetation before(2015)and after(2021)well-facility farmland construction in the Loess Tableland was estimated,and the results showed an overall increasing trend from 2015 to2021.The seasonal variation of NPP was significant,with the highest growth in summer and the lowest in winter.Using a soil respiration model to estimate soil respiration(Rh)and combining it with NPP to calculate Net Ecosystem Productivity(NEP),the results showed an overall increasing trend of NEP in the Loess Tableland from 2015 to 2021.The area of carbon sink accounted for 97.98%of the total area,and the annual average NEP was greater than zero,indicating that the Loess Tableland is a net carbon source.(3)Well-facility farmland construction is beneficial for increasing production and carbon sequestration in farmland ecosystems.Under different suitability conditions,the yield of the area very suitable for construction is higher than that of the suitable area,which is higher than that of the moderately suitable area,which is higher than that of the marginally suitable area,which is higher than that of the unsuitable area.The higher the increase in yield,the higher the suitability level,indicating that well-facility farmland construction is beneficial for increasing crop yield.With the increase of suitability level for well-facility farmland construction,the annual average increase in NPP is greater and its growth rate is also higher,indicating that well-facility farmland construction in the Loess Tableland region can improve vegetation growth environment.Similarly,with the increase of suitability level for well-facility farmland construction,the annual average increase in NEP is greater and its growth rate is also higher.This study focuses on the Loess Tableland region and evaluates the suitability of well-facility farmland construction using three indicators:natural endowment of cultivated land,field infrastructure,and socio-economic conditions.The Carnegie-Ames-Stanford Approach(CASA)model and a soil microbial respiration model were used to estimate the Net Primary Productivity(NPP)and Net Ecosystem Productivity(NEP)of the land ecosystem before and after well-facility farmland construction.The study analyzes the impact of well-facility farmland construction on increasing production and carbon sequestration in farmland ecosystems.The research results will provide guidance for the high-quality development of farmland in the Loess Tableland region and serve as a demonstration for well-facility farmland construction in China. |
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