[Spatial-temporal Differentiation Characteristics and Influencing Factors of Cultivated Land NPP in Major Grain...

As an important cornerstone of grain production， the fluctuation of the quantity and quality of cultivated land resources is directly related to the stability of grain production， which in turn affects the effective supply of grain and food security. In recent years， in the face of the pressure of food demand caused by population growth， China has promoted cultivated land protection as a basic national policy and formulated and implemented a series of strategies for cultivated land protection and balanced control. Because of this， as the world's largest developing country， China has successfully fed 22 % of the world's population with only approximately 9 % of the world's arable land resources. However， factors such as urban construction land expansion， land degradation， and climate change still pose severe challenges to agricultural production. Henan Province， as the core area of national grain production， or 'China granary'， plays an important role. In order to ensure national food security， Henan Province has put forward the agricultural space development strategy of implementing the spatial layout of the national agricultural industry， improving the scale and intensive level of grain production， and guiding the development of agricultural modernization. At the specific implementation level， it is key to formulate relevant cultivated land zoning control strategies according to local conditions. However， due to the lack of research on the spatial and temporal evolution of cultivated land productivity， it is still impossible to get rid of the reality of taking administrative divisions as the control unit. Therefore， it is of great significance to explore the spatial and temporal differentiation characteristics of cultivated land use in Henan Province and the influencing factors of cultivated land productivity changes， so as to scientifically formulate the control strategy of cultivated land zoning， to implement the strategic pattern of national main functional areas， to keep the bottom line of land space security， and to ensure national food security. Based on this， this study constructs the transfer matrix of cultivated land use based on China's annual land cover data set and introduces the landscape pattern index of cultivated land to evaluate the spatial and temporal differentiation characteristics of cultivated land space in Henan Province from 2000 to 2020， and then the reasons for its change were analyzed. At the same time， using the net primary production （NPP） data set， Theil-Sen Median + Mann-Kendall trend analysis， Hurst index analysis， coefficient of variation analysis， partial correlation analysis， and partial correlation coefficient were used to explore the evolution of cultivated land productivity in Henan Province and quantify the impact of climate factors and human activities on cultivated land productivity. The results show that： ① Based on the expansion of urban construction land combined with the impact of cultivated land regulation policies and major projects， the area of cultivated land transferred out during the study period was much larger than the area of cultivated land transferred in， and the cultivated land was mainly transferred out for construction land， and the cultivated land in the Huang-Huai-Hai Plain and Nanyang Basin， as the main grain producing areas in Henan Province， fluctuated greatly. ② During the study period， the degree of fragmentation of the transferred cultivated land increased significantly. From the perspective of spatial distribution， the transferred-in cultivated land was more fragmented than the transferred-out cultivated land， showing the spatial variation characteristics of concentrated transfer-out and close to construction land and sporadic transfer-in. ③ The interannual distribution of cultivated land NPP showed significant differences， namely， high in the south and low in the north. The interannual variation trend gradually increased （4.23 g·m^-2·a^-1， calculated by C， the same below）， and the annual average value was between 78.16 and 1 080.58 g·m^-2·a^-1. ④ During the study period， 96.61 % of the cultivated land NPP showed an increasing trend， but the different growth rates showed obvious spatial heterogeneity in the study area， and the future growth may slow down or degrade. ⑤ The contribution of solar radiation to the change of NPP in cultivated land was more significant in climate factors. On the whole， human activities promoted the accumulation of NPP in cultivated land in the study area， but there were differences in space. The area of NPP reduction in cultivated land accounted for 1.76% and was relatively concentrated， mainly due to the expansion of urban construction space dominated by human activities. At the same time， the study found that the marginal area of cultivated land NPP reduction was affected by climate but showed an increasing trend.