成都市耕地资源及耕地压力时空变化特征分析

On Spatial and Temporal Variations of Cultivated Land and Its Pressure Index in Chengdu

基于成都市1952-2009年的耕地、粮食产量及人口等统计数据,对全市耕地资源及耕地压力的时空变化特征及原因进行了分析.结果表明:1952-2009年成都市耕地面积减少了37.73%;耕地变化过程可分为波动期(1952-1965年)、平缓下降期(1966-1998年)、急剧下降期(1999-2003年)和快速下降期(2004-2009年),4个时期耕地年均减少速度分别为0.37%,0.44%,3.54%和1.16%;空间上近郊耕地减少速度总体上大于远郊.由于粮食单产和复种指数的不断提高,1952-1992年全市耕地压力指数总体呈现下降趋势;1993-1998年耕地压力指数均小于1,耕地无明显压力;1999-2009年由于耕地大幅减少、粮经作物结构调整和人口的快速增加,耕地压力指数急剧增大.近郊在1998年耕地压力指数由小于远郊转变为明显大于远郊.农业结构调整、城镇及工业发展、退耕还林、粮经比和人口等因素的变化及区域差异是近年来全市耕地面积减少和耕地压力增加产生时空差异的主要因素.

With the rapid development of economy and urban expansion in the plain areas, there are serious contradictions between protection of cultivated land and urban development in these areas. Chengdu city, located in Chengdu plain, is a region with rapid economic and urban development. To coordinate relation-ship between urban development and cultivated land protection, the spatial - temporal variation of cultivated land and cultivated land pressure index of Chengdu City and the causes were analyzed in this paper based on statistics of cultivated land, population and grain yield from the agricultural statistical yearbooks and statistical yearbooks of Sichuan Province between 1952 and 2009. Results shows that, the area of cultivat-ed land decreased 20. 71 X 104 hm2 , with an annual decrease of 0. 66% from 1952 to 2009. The changing processes of cultivated land can be divided into four periods, they are fluctuating （1952-1965） , gentle declining （1966 - 1998） , sharply falling （1999 - 2003） and rapid declining （2004 - 2009） with the annual reduced degree of 0. 37 % 、0. 44% 、3. 5 4% and 1. 16 % resp ect ive ly . The changes of cultiva ted land in suburbs and outskirts shows different reduced speed in different periods. Totally, the annual reduced degree of suburbs is larger than that of outskirts. The adjustment of agricultural structure, urban and industry development are the major causes for the decrease of cultivated land in suburbs, while the policy of returning farmland to forests is one of the important reasons for outskirts besides the reasons of suburbs. Duo to the increase of grain yield per unit and the multiple cropping index, the cultivated land pressure index of the whole city shows a decreased trend from 1952 to 1992, which is decreased from 1. 33 to 0. 94. The pressure index is less than 1 during 1993 to 1998,suggesting no obvious pressure on cultivated land. Since 1999 the pressure index increased sharply from 0. 99 in 1998 to 1. 63 in 2009. The pressure index of suburbs was lower than that of outskirts before 1998,while suburbs showed a larger pressure index than outskirts since 1998. The factors such as the structure adjustment of food crop and economic crop, great decrease of cultivated land and rapid increase of population resulted in the sharp increase of cultivated land pressure index, and the regional differences in these factors caused the different change speed of pressure index in suburbs and outskirts.