Dynamic monitoring and control benefits of vegetation in rocky desertification areas based on Landsat images

Abstract: Ecological restoration is an effective measure to mitigate rocky desertification, control water loss, protect the existing forests and increase vegetation coverage. The long-term ecological restoration project is the key to the sustainable development of regional economy and ecology. Chinese governments have implemented a series of the Karst Rocky Desertification Comprehensive Control and Restoration Project in the karst regions of Southwest China since the late 1990s. In order to reveal the effectiveness of the Karst Rocky Desertification Comprehensive Control and Restoration Project implemented in the typical rocky desertification zone in Luxi County of Yunnan Province, we analyzed the spatiotemporal variation of vegetation coverage on the basis of Mann-Kendall mutation test, Theil-Sei trend analysis, and the relationships between remotely sensed vegetation indices named normalized difference vegetation index (NDVI) and climate changes, human activities using multiple regression analysis and residual analysis. For the analysis, the Moderate Resolution Imaging Landsat TM data at a spatial resolution of 30 meters over the period 1986-2016 are considered. The results are as follows: 1) In the past 30 years, the vegetation coverage of Luxi County showed a significantly increasing trend, with a growth rate of 0.43%/10a (P<0.01), a sudden change-point of time appeared in 2001, and the growth rate increased from 0.35%/10a (P>0.1) to 0.63%/10a (P<0.1); 2) The areas with high vegetation coverage primarily distributed in the eastern and western mountain areas of Luxi County, while the low vegetation coverage distributed at the junction of towns in the central and northern areas; 3) In terms of trends, the areas of ??vegetation coverage showing increasing and decreasing accounted for 85.2% and 14.79% over the period 1986-2016, respectively. Between 1986 and 2000, the areas of ??vegetation coverage with extremely significantly increase only accounted for 7.71%, scattered in the northern. But the areas of ??vegetation coverage with extremely significantly increase rose to 21.62% between 2001 and 2016, which was primarily distributed in eastern mountainous areas where the priority was given to implement the Karst Rocky Desertification Comprehensive Control and Restoration Project; 4) Increase in temperature and precipitation had a positive effect on vegetation coverage, and the contribution of temperature (r = 0.45, P<0.05) on vegetation coverage was significantly higher than precipitation (r =0.372, P<0.05). Between 2001 and 2016, human activities played an important role in the improvement of vegetation coverage. The areas that human activities played a positive role in vegetation coverage accounted for 79.6%, and the areas that human activities played a negative role in vegetation coverage only accounted for 20.4%, almost located in the towns. The impact of climate change on vegetation coverage accounted for 39.1%, the impact of human activities accounted for 60.9%; 5) The ecological restoration project farther from the town showed more important role in the improvement of vegetation coverage. The role of human activities in vegetation improvement is significantly stronger than climate changes. Our study suggested that the Karst Rocky Desertification Comprehensive Control and Restoration Project contributed on the improvement of vegetation coverage and was deemed as one of the important driving forces for vegetation increasing between 2001 and 2016.