Analyzing Temporal and Spatial Distribution Characteristics of Pressure Index of Cultivated Land in China
中国耕地压力指数时空规律分析

The pressure index of cultivated land is the ratio of per capita minimal area of cultivated land and per capita actual area of cultivated land. The pressure index of cultivated land could reflect the status of pressure on cultivated land. The paper calculates the pressure index of cultivated land since China's economic reform and opening-up using the pressure index model It is found that the pressure index decreased from 1981 to 1996 because the speed of per capita minimal area decrease is faster than that of per capita actual area. And the pressure index increase after 1996 because per capita actual area decreases rapidly. After calculation of pressure index in different provinces in 2004,there are 21 provinces' pressure index is more than 1and the pressure index inShanghai is up to 2.84. Even in the 5 provinces, the pressure index is all more than 0.78. The regional pressure is extremely obvious. There are three aspects of reason that cause various provinces pressure index on the high side. Firstly, cultivated land in some provinces is taken massively, which induces per capita actual area of cultivated land smaller then makes pressure index of cultivated land on the high side,such as Shanghai, Zhejiang and so on. Secondly, per capita minimal area of cultivated land is on the high side because of low level of unit output which is limited of natural condition and agricultural science, such as Gansu, Shaanxi, Sichuan, Guizhou and so on.Thirdly, some provinces in which grain are producted mainly must undertake duty of national food security, which causes per capita minimal area of cultivated land on the high side, such as Hubei, Hunan and so on. It could relieve cultivated land pressure status by controlling the speed of cultivated land decreasing and enhancing the standard of agricultural science and technology.