Spatial Pattern and Topogr aphic Control of China''s Agricultural Productivity Variability
中国农田生产力变化的空间格局及地形控制作用

Being home to one of every five people in the world, China always put the food security issue high on its agenda and has successfully provided adequate food for its people. However, the stagnation of global agricultural production during the 1990s is not a short-term phenomenon caused by policies or market. Therefore, it is significant for food security, agricultural policy making and ecosystem service functions adjustment to recognize the variability of agricultural productivity and its predominant controlling factors at decadal temporal scale. The effect of topography on agricultural productivity variation has been poorly understood due to the lack of spatially explicit agricultural productivity information. In this study, the agricultural productivity variation and its spatial heterogeneity between the 1980s and 1990s are analyzed using a satellite-based production efficiency model (GLO-PEM) driven with NOAA/AVHRR data. It is shown that spatial heterogeneity of agricultural productivity variability was predominantly controlled by the topographic conditions at decadal scale. The proportion of cropland area occurring in agricultural productivity reduction increased with the amplifying relief, and consequently, the probability of cropland in hilly areas suffering from agricultural productivity reduction was 10%-30% higher than cropland in plain areas. Although the total agricultural production had increased in each agricultural region of China during 1981-2000, there were parts of cropland area suffering from reduction of agricultural productivity, accounting for 24% of the total cropland area. In those croplands with decreased agricultural productivity, 71% were located at hilly areas, particularly on the Loess Plateau and Yunnan-Guizhou Plateau areas.