Monitoring interannual dynamics of desertification in Minqin County,China,using dense Landsat time series

Minqin County in northwestern China is highly affected by desertification.Campaigns have been initiated in recent decades to combat desertification in Minqin.To assess the effectiveness of these campaigns,this study used a dense Landsat time series from 1987 to 2017 to investigate the interannual dynamics of vegetation coverage and greenness over the past 31 years.First,this study applied an advanced technology to reconstruct a high-quality Landsat annual time series.Specifically,one image in the vegetation-peak season was selected as the base image in each year,and then problematic pixels were interpolated by the neighborhood similar pixel interpolator using ancillary images in the same year.Second,the land cover map and the enhanced vegetation index(EVI)were derived from all reconstructed images.Third,the change of vegetation coverage and EVI values over the 31 years were analyzed.The results show that the total vegetation coverage and greenness increased during the 31 years.Linking this change trend to other factors suggests that vegetation in Minqin County is highly affected by agriculture and groundwater supply rather than by climate.To mitigate desertification in a sustainable way,agriculture should be well managed to avoid overconsumption of natural resources such as underground water.

Relative Ecological Value of Major Plants in Minqin Desert Area

This paper analyzed relative ecological value of several major plants in Minqin desert grassland using layered projection of plant canopy. The results showed that ecological functions of natural Nitraria tangutorum and Ephedra sinica woods of a unit area were much better than those of artifi cial Haloxylon ammodendron woods, relative ecological value of N. tangutorum, E. sinica and Artemisia desertorum were much higher than that of artifi cial H. ammodendron woods. Layered projection explains clearly the ecological functions and relative ecological value of desert vegetation of the same coverage. It is inaccurate to indicate wind prevention and sand fi xation of desert vegetation in deserts using ecological function service value and ecological niche calculated on the basis of two-dimensional vegetation coverage, but three-dimensional projection degree should be applied to indicate ecological functions and relative ecological value of vegetation. Application of layered projection of plants in calculating ecological functions and relative ecological value of desert plants(vegetation) is the innovation point of this research.