Land use change driven by Sloping Land Conversion Program in typical watershed on Loess Plateau and its rationality evaluation

Abstract: To combat the severe soil erosion and improve the regional eco-environment, the Chinese central government initiated the Sloping Land Conversion Program (SLCP) in 1999. This program implemented on the Loess Plateau has resulted in dramatic land use change in the region. It is of significance to understand the land use change and its rationality for developing effective strategies in the next period of the program in the region. In this study, we explored the spatiotemporal characteristics of land use change over 2000-2014 in Qingshuihe Watershed(436 km2) located in the west Shanxi Province, a typical watershed on the Loess Plateau. Land use data for 2000, 2005, 2011 and 2014 were interpreted from TM/ETM+ images by using the supervised classification method. To improve the interpretation accuracy, the high-resolution images of Google Earth were used to revise the supervised classification results. The concept of rational degree was introduced for evaluating the rationality of land use change. The discriminant criterion for rationality was developed based on the integrated analysis of ordinances, regulations, and policy of SLCP as well as the studies about soil erosion and vegetation succession on the Loess Plateau. The results showed that the land use structure of the watershed had changed significantly. Land use ratio of farmland: orchard: forestland: grassland was evolved from 1:0.06:2.05:3.95 in 2000 to 1:3.22:12.03:5.51 in 2014. From 2000 to 2005, the percentage of farmland and grassland decreased to 9.19% and 52.76%, while the percentage of orchard and forestland increased to 1.82% and 35.64% respectively. Incented by the favorable subsidy of SLCP, farmland on gentle slope(<15°) was even converted to forestland and grassland, leading to the low rational level of land use change with the rational degree of only 78.60%. In order to improve the livelihood of the program participating farmers, the local government carried out the construction of basic farmland and orchard actively in 2005-2011. Some grassland was converted to high-quality basic farmland, but at the same time large amounts of sloping farmland and grassland were converted to orchard, leading to the decrease of farmland and grassland and increase of orchard. The percentage of farmland and grassland decreased to 7.62% and 43.19% respectively, while the percentage of orchard increased to 6.29% during this period. Moreover, forestland coverage increased from 35.64% to 41.69%. The overall rational degree of land use change increased to 91.71% that was a high rational level. With the further expansion of apple tree planting from 2011 to 2014, farmland and grassland were continuously converted to orchard. The percentage of orchard increased to 14.52%, while the percentage of farmland and grassland decreased to 4.51% and 24.89%, respectively. Forestland had been increasing constantly up to 54.30% of the total watershed. The overall rational degree of land use change was up to 95.20%.We suggest that the ultimate objectives of SLCP should be focused on achieving the balanced tradeoffs between grain production, economic trees and ecological forests and the integration in the policy instrument for implementing more effectively the program. More specifically, major efforts for next period of SLCP for this watershed should be implemented by improving the stability, structure and function of current ecological plantation forests established while maintaining a reasonable farmland scale and controlling the expansion of orchard.