Spatial pattern analysis on quantity and quality of cultivated land in mid-west Jilin province based on remote sensing

Cultivated land resource is the material base that mankind depend on for existence. Understanding how the cultivated land changes in quantity and quality has an important significance for country's food security and social stability. Based on the satellite images from Landsat TM/ETM in 2000 and OLI in 2013, this paper mapped the spatial distribution of cultivated land in the mid-west Jilin province both in 2000 and 2013 and analyzed its temporal and spatial changes. Furthermore, soil data from 2351 field sampling points in study area were used to evaluate the quality of cultivated land and a comprehensive evaluation was made. Results revealed that cultivated land area in the mid-west Jilin province increased from 5.61×104 km2 in 2000 to 5.64×104 km2 in 2013, among which dry farmland increased by 645 km2 and paddy field decreased by 350 km2. The transformation between dry land and paddy land was evident. Distribution of cultivated land changed differently from the east to the west: increasing in west part of study area and decreasing in east part, which resulted in the gravity center of cultivated land moved toward the west obviously. The increased cultivated lands were mainly converted from wetland and grassland, accounting for 66.04% and 21.12% of the total change area, respectively. The lost cultivated lands were mainly turned to artificial area, woodland and wetland with an area percent of 45.08%, 28.85% and 22.61%, respectively (mainly distributed around Changchun city). In terms of cultivated land quality, most cultivated lands were in upper-middle grade in the mid-west Jilin province in 2013, and the quality in the east part was better than that of the west. Although the total area of cultivated land increased, the quality of increased cultivated land mainly distributing in Baicheng and Songyuan city corresponded to lower grades including the third, fourth and fifth class with an area of 235, 148 and 218 km2 respectively. Besides, the area of cultivated land in first class decreased by 305 km2, which mostly happened in the surrounding regions of Changchun city. The factors influencing the change of cultivated land were analyzed and we found that urbanization and policy were the most important driving forces to affect cultivated land quality and quantity. Accompanied by the rapid urbanization process, more and more high-quality cultivated lands were occupied. Newly increased cultivated lands were mostly reclaimed from salinized land, alkalized land and wasteland, which led to an increase of cultivated land area and a decrease in quality. Overall, the cultivated land in the mid-west Jilin province degraded severely during the past 15 years. This paper can provide an important reference for regional sustainable development of cultivated land resource.