Spatio-temporal dynamics and ecological service function assessment of slope farmland in Karst areas of Guizhou province, China

Abstract: Slope farmland is strongly affected by human activity in karst areas of southwest China, which leads to prominent ecological problems. Quantitative evaluation of spatial-temporal dynamics and ecological service function of slope farmland in Karst areas of southwest China can be of significance in desertification control and ecological recovery, poverty alleviation and community development. Based on land-use data obtained from multi-temporal and multi-source remote sensing images in the years of 2000, 2005 and 2010, and with the consideration of slope gradient, lithology, settlements and transportation conditions, this study used the land-use dynamic model, integrated Hot-spot area model and the model of value ecosystem services to study spatial-temporal dynamics and ecological service function of slope farmland since 2000 in the Karst areas of Guizhou province (103°36′-109°35′E, 24°37′-29°13′N), China. The results showed that the farmland of 4.4 thousand km2 had been reduced in the Karst area since year 2000, and about 80% of the lost farmland was from the slope area. The most farmland was distributed in the slope gradient from 6° to 15°. With slope gradient increasing, the percentage of slope farmland was reduced significantly. In addition, the spatial dynamics of slope farmland was correlated with the types of soil parent geological materials in Karst areas. The proportion and quantity of land loss in the slope farmland derived from limestone, especially steep slope farmland, was significantly higher (P<0.05) than the land in dolomite areas. There was more slope farmland distributed in slight slope of dolomite areas. Moreover, for the space distribution, the steep slope farmland was often located in areas far away from the settlements with most slope farmland located in the areas >900 m away from settlements. For these areas, changing land use should been accelerated in order to conserve the soils and vegetation. Also, road for automobiles had a strong impact on the process of land use change from agriculture in the slope farmland. About 30% of land in the areas <500 m away from the automobile road had been changed into other land uses rather than traditional agriculture from slope farmland. With the increase in distance away from the road, less land use changes in the slope farmland were observed. Two hotspots in northeast Zunyi and Tongren were Wujiang catchment closing the Yangtze River, and Guiyang and Anshun cities in Guizhou plateau, where land use was changed from traditional agriculture to other land uses in the slope farmland of Karst areas, Guizhou province. Finally, since 2000, land use change in the slope farmland from agricultural use had produced good ecological effects in Karst areas. The ecological services value (ESV) of the land use change in the slope farmland was estimated to be RMB 43,998,100 yuan /yr. In short, slope farmland in karst area has changed greatly in recent decades and its ecological effect is obvious.