Spatiotemporal characteristics of cultivated land use transition in hilly and mountainous regions based on barycenter model

Topographic relief is the constraining factor of land use in an area. This is especially the case in transitional zones in hilly and mountainous regions. To analyze the spatial and temporal characteristics of cultivated land utilization transformation in hilly and mountainous regions, this study selected Ganzhou city as a case study area. Six period (1990, 1995, 2000, 2004, 2009 and 2014) dataset of land use of 30 m resolution images were used to extract the relief degree and land cover data of land surface. The optimal statistical unit of topographic relief was determined by means of DEM data and mean turning-point analysis method. In order to contrastive analyzing the dynamic relationship of the spatial location-relation and the spatial correlation for different land use types, this study introduced the concept of land use barycenter. The results showed that the best statistical window was proved 0.865 km2. The topographic relief of Ganzhou was divided into four grades: Plains, micro relief mountains, small relief mountains and medium relief mountains. The ranking of annual mean area for mountain types was small relief mountains>medium relief mountains>plains>micro relief mountains. In addition, the spatial distribution of elevation was consistent with the relief degree of land surface. Based on six period dataset of land use of 30 m resolution in the Ganzhou, cultivated land forest, grasses, bare land, water and artificial surface barycenter and there movement directions of five period (1990-1995, 1995-2000, 2000-2004, 2004-2009 and 2009-2014) were calculated. Five period barycenter movement directions of cultivated land was 63.4°, 330.5°, 201.4°, 203.4° and 106.4°. Pearson correlation coefficients of barycenter movement for cultivated land and forest, grasses, bare land, water and artificial surface were 0.44, 0.94, 0.02, 0.36, 0.85. The correlation coefficient of barycenter movement for cultivated land and grasses was 0.94, which was higher than the others. By tracking adjacent patch shape changes of cultivated land and grasses in observation of land use patch and land use spatial pattern, the spatial position change of cultivated land and grasses was closely related. The second high correlation coefficient of barycenter movement for cultivated land was 0.85, which was for cultivated land and artificial surface. Artificial surface had the closest ties to cultivated land, but the morphological change of cultivated land and artificial surface was not consistency. Cultivated land use intensity and the area of cultivated land use transition decreased with the raising relief degree of land surface. The major transformation types about cultivated land were mutual conversion between forest and cultivated land, and mutual conversion between grasses and cultivated land. The area change of cultivated land had a higher interrelationship to the forest than the others. Moreover, the spatial position change of cultivated land had a higher interrelationship to the grasses than the others. The cultivated land use transition in hilly and mountainous regions is the results of natural and human effects. The study provide a scientific basis for the management of cultivated land in hilly and mountainous regions.