Diversity Pattern And Community Assembly Of Shrub And Desert Plant Communities In Inner Mongolia

Large-scale geographical distribution patterns of biodiversity has always been the focus for ecological researchers.Among the numerous studies of distribution patterns of plant diversity,the research on the longitude gradient pattern of species diversity of woody plant communities are rarely reported.Scrubland is an important vegetation component widely distributed in arid and semi-arid areas of Inner Mongolia,while desert is also a momentous vegetation type widely distributed in arid or extremely arid regions of western Inner Mongolia.These two vegetation types,which are dominated by shrub species,play a vital role in maintaining ecosystem functions and protecting ecological security in this area.However,few studies focused on the description of community characteristics and quantitative analysis,the distribution pattern and driving factors of species diversity,as well as community assembly along the longitude gradient.We conducted field surveys of naturally distributed shrub communities along the water gradient(longitude gradient)from northeast to southwest throughout the Inner Mongolia Autonomous Region.Based on the taxonomic statistics of 42 scrubland and desert formations,and the analysis of plant diversity of 177 communities in different levels and multiple dimensions,we described the species composition and structural characteristics of each formation in detail,and separately analyzed the distribution patterns of woody plants,herbaceous plants and community species richness along the water gradient and their relationship with environmental factors.Additionally,we also explored the community assembly mechanisms of scrubland and deserts at three levels of species diversity,phylogenetic diversity and functional trait diversity,combined with two dimensions of alpha and beta diversity.The main results are as follows:(1)Compared with the data published in "Chinese Vegetation" in 1980,a total of 26 shrub formations have been investigated,and 16 new formations were newly recorded.(2)Extending from the northeast to the southwest along the precipitation gradient,the species richness of herbaceous and community generally presented a decreasing pattern,which is basically consistent with the spatial variation pattern of precipitation.However,the species diversity of woody plants did not show an obvious trend distribution pattern along the longitude gradient.(3)Both the phylogenetic and functional character structure of shrub and desert communities were mainly aggregated,which indicates that the formation of these two structures is mainly driven by environmental filtration.(4)The species diversity indices of communities of mountain,high plain and deserts,as well as the diversity of species,phylogenetic and functional beta diversity among communities were basically significantly different.And the results of considering the relative abundance of species were not completely consistent with which not considering the relative abundance.(5)There were obvious distance-attenuation patterns in species,phylogenetic and functional traits similarity among shrub and desert communities,and the environmental filtration and diffusion restriction jointly drive the beta diversity pattern of scrubland in Inner Mongolia.That is to say,the community assembly of scrubland and desert is dominated by both niche theory and neutral theory.To sum up,the environmental factors such as annual precipitation play an important role in driving the species diversity distribution pattern of shrub and desert communities in Inner Mongolia,while long-term environmental filtration and diffusion restrictions affect the phylogenetic and functional structure of shrub communities to a large extent.In addition,factors such as the layout of sample plots for field community survey and the selection of functional traits may also affect the relationship between community diversity and environmental factors.