Changes in Vegetation Pattern and Their Driving Factors Across Four Mega Deserts in Northern China during 1990～2015CN
Abstract：Four mega deserts(Hulun Buir,Horqin,Otindag and Mu Us)are very fragile and highly sensitive to climate change and human activities,which are the key regions for vegetation construction in northern China.To investigate the dynamics of the sand-fixing vegetation patterns and their influencing factors is thus a crucial requirement for introducing and establishing sand-fixing vegetation.Based on vegetation map,several typical vegetation types with different dominant species(Artemisia sp.,Caragana sp.,Ulmus sp.,and Pinus sylvestris var.mongolica)were selected in four mega deserts to analysis vegetation dynamics using landscape vulnerability index and detect their influencing factors using the Geodetector method.The main results and conclusions are as follows:(1)From 1990 to 2015,there was no significant change in vegetation cover in each mega desert.In the spatial distribution,the area with increased vegetation cover in three deserts(except Horqin)was larger than the deterioration area,especially in the Mu Us,where vegetation coverage showed an increasing trend in more than 80%of areas.(2)Different vegetation showed different landscape pattern dynamics.Overall connectivity of Artemisia shrublands enhanced,landscape vulnerability decreased,and landscape pattern gradually stabilized.Caragana shrublands showed a decreasing trend,and their landscape pattern became stable.Elm forestlands gradually represented fragmentation,landscape vulnerability continued to rise,and landscape pattern stability declined.Natural Pinus sylvestris var.mongolica forestlands showed a stable status,while artificial Mongolian pine forestlands showed declining trends.(3)At the time scale,annual precipitation,annual temperature and growing season precipitation had no significant change trend.The growing season temperature in the Mu Us desert showed a significantly decreasing trend,while the growing season temperature of the other three deserts showed a significant upward trend with the largest in the Hulun Buir Desert.(4)Artemisia sp.and Caragana sp.shrublands were mainly influenced by average annual precipitation(q=0.3 1,q=0.41,respectively),and they could continue to play their ecological service for wind break and sand-fixation.Ulmus sp.and Pinus sylvestris var.mongolica forestlands were mainly influenced by LUCC and growth season temperature,respectively.(5)This study suggested that in mega deserts of northern china,differentiated strategies for vegetation restoration and protection should be developed under different climatic conditions to mitigate and control land degradation.Specifically,in the drier land,the sand-fixing vegetation should mainly consist of Artemisia sp.or Caragana sp.species.Pinus sylvestris var.mongolica may be not suitable for large areas of introduction to the lower latitude regions.Besides,Ulmus sp.forestlands need to be strictly sealed and protected.