Time-sequence characteristics of the annual changes of the agricultural land use in China during the period 1980～2002

Based on the cost-income datum(1980～2002) of farm product and the China Agricultural Yearbook, taking these main crops in the progress of the arable land use as a study case, this paper studied the characters and its driving force for the annual changes of the degree of intensity, the sowing area and the abandonment of the arable land. The results showed that the degree of intensity and the sowing area of the land use in China during 1980～2000 had a total trend to increase, but there were three times to decline. And when the degree of intensity declined obviously during the period of 1984～1986, 1992～1993 and 1997～1999, the sowing area of the crop shrank evidently and the abandonment of land use began to increase notably almost in the same time. The ultimate cause to result in these changes had a tightness relation with the change of the net return for the cost factor and land factor in the progress of the land use. But the changes of the intensity, the sowing area and the abandonment of land use often lag 1～3 years after the net return change of the land use because of the response course of "observing—balancing—acting".