PRESENT PRESSURE ANALYSIS AND TREND PREDICATION OF CULTIVATED LAND IN HUNAN PROVINCE
分析了1949-1999年湖南省耕地面积和人均耕地变化，用压力指数评估耕地紧张程度，预测2031年将达阈值，建议依靠科技提高单产并加强保护。
Since the foundation of P. R. China, the total cultivated land area in Hunan has decreased fluctuantly. Within 51 years, it decreased 189.1 thousand hm2 from 3402.3 thousand hm2 in 1949 to 3,213.2 thousand hm2 with the rate of 3.6 thousand hm2 per year. With the increase of population, construction of city and process of industralization, the supply and demand condition of limited cultivated land become worse. On the one hand, the process of citilization and industralization enlarged the demand for land, on the other hand, increasing population induced the increasing demand for cultivated land. As a result, the use of cultivated land resource in Hunan is in a dilemma. The per capita cultivated land area in Hunan reduced from 0.114 hm2 in 1949 to 0.0492 hm2 in 1999.Consequently, the burden of limited cultivated land resource is heavier. The per capita cultivated land area in Hunan only accounts for 55.6 percent that of China and it takes the last four place among all provinces, municipalities and autonomous regions in China. The per capita cultivated land area in 9 prefectures and 56 counties of Hunan is less than 0.05 hm2 and that of 12 counties is less than 0.0339 hm2.Taking minimal demand for per capita cultivated land area --per capita cultivated land area critical value as a standard, this paper uses the ratio (K) of revised per capita cultivated land area critical value (Smin) and actual per capita cultivated land area (Sa) as index of cultivated land pressure to illustrate the burden and serious condition of cultivated land pressure. The equation is K=Smin/Sa.When K1,the cultivated pressure is not obvious; when K=1,it reaches the threshold of it; when K1,the cultivated pressure is obvious. Smin is calculated by the following model:Smin=(β·Gr·M)/,Where, β is the ratio of self-support; Gr is the average food demand; M is the total area of cultivated land; Z is the output of food and R is the coefficient of calamity.The results illustrate that from 1949 to 1999, the cultivated land pressure index in Hunan fluctuates obviously. From 1949 to 1969,the index (K) is mostly lager than 1 and reached the highest level in 1959,so the cultivated pressure is obvious. From 1969 to 1984,the index is mostly smaller than 1, so the cultivated land pressure is not obvious. From 1984 to 1999, the cultivated land pressure index takes on an in creasing trend and the index increases gradually.By the curve regression analysis of cultivated land pressure index from 1978 to present, this paper chose the mathematical model to predict the trend of cultivated land pressure index in the future. Based on the analysis and predication, this paper draw a conclusion that cultivated land pressure index will reach its threshold in 2031, and then the cultivated land crisis will be more serious. As a result, cultivated land pressure can be relieved by relying on the progress of science and technology to improve the output of cultivated land. At the same time, making rational use of cultivated land and putting the protection of cultivated land into reality are good ways to relieve the cultivated land pressure.