Health status evaluation of the farmland supply function at county level in Hebei Province

An adequate supply of agricultural products is vital for human wellbeing."ecosystem service" theory is used to study the supply function,the dominant function of farmland ecosystems.The concept of health status of the supply function covers the core components of ecosystem health,such as the level of system productivity,the stability and persistence of productivity,and the connection between productivity and human welfare.There is a close connection between the health status evaluation of the farmland supply function described in this paper and land suitability assessment,which is applied widely at home and abroad. We first establish the stability coefficient of farmland productivity(Cs) as a health status evaluation index of the supply function of the farmland ecosystem at the county level.The stability coefficient of farmland productivity was defined as an average ratio between the fluctuation coefficient of net primary productivity in the natural ecosystem and the farmland ecosystem at county level in a certain period.Following this,correlation analyses were carried out between the stability coefficients of farmland productivity and human welfare,which was represented by county-level net income per capita of cultivated land.Finally,a threshold value for a healthy farmland supply function was determined through a correlation analysis of 136 counties. Our results demonstrated that the stability coefficients of farmland productivity could be used to evaluate the county-level health status of supply functions of farmland ecosystems.According to our experience,10 years is the optimal time scale for evaluation.The stability coefficients of farmland productivity were significant for both the stability of farmland productivity and the absolute levels of farmland productivity.The boundaries of human society feedback effects on ecosystems were critical in determining the healthy status threshold.In this paper,if "Cs≥1",with an increase in the stability coefficients,the net income per capita of cultivated land would increase slightly;and if "Cs1",with a reduction in the stability coefficients,the net income per capita of cultivated land would decline sharply.Therefore,"Cs=1"was selected as the threshold value for a healthy farmland supply function. The stability coefficients in both 1991—2000 and 2001—2009 showed an increasing trend and consistent spatial pattern in Hebei Province.The counties with lower stability coefficients of farmland productivity and poor health status of the farmland supply function were concentrated in the ecologically fragile areas of the northern Hebei Province,where many people live in poverty.The counties with higher stability coefficients and a healthy farmland supply function were located in the central and southern Hebei Province,where the land use was rational and most people were wealthy.This suggests that people′s poverty status is spatially related to the health status of the farmland supply function. The results of this study provide important referents for the adjustment of land-use structure,and for eliminating regional poverty in the northern Hebei Province.In the future,we need to investigate how to combine the health status evaluation of the farmland supply function and land suitability assessment.