Spatio-temporal differentiation characteristics and impact factors of cultivated land in Ngari Prefecture of Tibet, China

Cultivated land resources have restricted the agricultural production and economic development in China, particularly with the ever-increasing urbanization and population. There are the spatiotemporal variations of cultivated land in different regions, due to the different natural and social economic conditions. However, only a few quantitative studies have been focused on the distribution of cultivated land use under various terrain and climate in the field of geography. Furthermore, the data accuracy of most studies cannot accurately reflect the spatial change of cultivated land. Taking Ngari Prefecture as the research area, the purpose of this study was to explore the spatiotemporal differentiation and distribution of cultivated land resources under different terrain and climate. Farmland data was collected in 2005, 2013 and 2020. Google Earth high-resolution imagery was then utilized to visually interpret with a resolution of 0.49-8.26 m. Kernel density estimation, spatial and buffer analysis functions in ArcGIS software were also used to identify the spatiotemporal differentiation and influencing factors of farmland. The results showed that: 1) In terms of spatial change, the scattered and fragmented cultivated land was more concentrated in the valleys of the southwestern part of Pulan County and the central part of Zada County. The small patches were dominated in the cultivated land. The cultivated land was also more concentrated in Pulan Township of Pulan County, Xiangzi Township of Zada County, Shiquanhe Town of Gar County and Ritu Town of Ritu County, compared with different townships. Meanwhile, the cultivated land was distributed mainly in the spatial area with an altitude of 3500-4500 m, a slope of 0-6°, a slope to the southwest, an average annual precipitation of 0-25 mm, an average annual temperature of 0-5°C, and a distance of less than 200 m from roads and rivers. 2) In terms of temporal change, the cultivated area was aggregated in a multiregional manner from 2005 to 2020, indicating a general trend of growth. The reason was attributed to the influence from the geographic location, natural environment, population increase, non-agriculturalization, and market demand. Specifically, the cultivated land area of Zada and Pulan counties in the south increased slowly or even declined, while there was the significant increase in the Gaer and Ritu counties in the north. 3) The cultivated land area was continued to expand in the future, in order to meet the demand of market and employment. There was the smaller increase in the south, together with the small decrease. An outstanding increase was found in the north. Therefore, the mechanization, the output value per unit area and the high-quality agriculture should be improved to focus on the environmental carrying capacity of regional arable land, soil quality and sustainability. In general, the farmland was also dominated by the location and hydrothermal conditions, particularly the influence from the population, non-agricultural development and market demand. The distribution and area changes of farmland were greatly varied in different regions. This finding can also provide a strong reference for the current status of land use, agricultural land planning and sustainable development of cultivated land in Ngari Prefecture.