ANALYSIS OF THE SPATIAL-TEMPORAL CHARACTERISTICS OF LUCC FROM 1975 TO 2015 IN THE DONGZHI LOESS TABLELAND

The Dongzhi loess tableland (34°50'~37°19‘N, 106°14'~108°42‘E) is the largest tableland on the Chinese Loess Plateau. However, the plateau surface of the Dongzhi tableland has suffered serious soil and water loss due to human activities. Land use change is an important indicator that reflects the impacts of human activities at regional scale. Therefore, the land use change of the Dongzhi tableland during the past 40 years (1975~2015) was characterized and the aim of this study was to quantify the dynamics of land use change and elucidate the impacts of human activities. In this study, the technologies of Remote Sensing (RS) and Geographical Information System (GIS) were applied and three imageries of remote sensing (1975, 1995 and 2015) were interpreted. Three indicators, including amplitude, direction and intensity of land use change, were used to characterize the dynamics of land use change and its driving forces. Results showed that:(1) Farmland and grassland were the main land use types on the Dongzhi tableland, which occupied more than 70% of the total land area. During the past 40 years, the area of construction land, forestland, water bodies and land for water conservation facilities exhibited an increasing trend, which increased by 236.25 km², 158.68 km² and 2.06 km², respectively. The grassland showed a changing pattern of first decrease in 1975~1995 and then increase in 1995~2015, which ultimately decreased by 166.93 km²; whereas the farmland showed a changing pattern of first increase in 1975~1995 and then decrease in 1995~2015, which ultimately decreased by 218.01 km². During the study period, the abandoned land showed a slight decrease of 12.02 km². (2) The directions of land use change showed similar characteristics during the two periods of 1975~1995 and 1995~2015. The mutual conversions between farmland, grassland, construction land and forestland were the main features of land use change during the two periods of 1975~1995 and 1995~2015. However, the frequent exchange between grassland and construction land was the dominant form of land use change in the area. During 1975~1995, large area of grassland converted to farmland and construction land; while during 1995~2015, large area of farmland converted to grassland and forestland. Moreover, an area of farmland converted to urban during the time of 1995~2015. (3) The integration indicators of land use change increased from 0.03 during 1975~1995 to 0.11 during 1995~2015, which indicated that the intensity of land conversion significantly increased. During 1975~1995, the integration indicators of land use change showed positive values (0.051); while it showed negative value (-0.012) during 1995~2015, which indicate that human activities are changing to a conservation role in the land use change on the Dongzhi tableland.