Characteristics Of Community Patches Under Three Grazing Modes In Sunite Desert-steppe

As the most basic manifestation of the spatial structure of the community in small scale range,the mini-patch of grassland reflects the current succession status and the future succession trend of the grassland in terms of the characters,composition and pattern.In this paper,a combination of ground survey and low altitude remote sensing of unmanned aerial vehicle was used to study the community characteristics,and landscape characteristics as well as distribution patterns of community mini-patch in the desert steppe of Sunite in Inner Mongolia under the modes of rest grazing,free grazing and rotation grazing.The main research conclusions are as follows:(1)There are 27 species of plants in test area,belonging to 24 genera and 8 families;there are 4 life forms,including perennial herbs,annual herbs,shrubs and subshrubs.Perennial herbs account for 51.85%of the total species.(2)From the rest grazing area to rotation grazing area,the diversity index of shannon-wianer decreases from 1.45 to 1,the pielou evenness index decreases from 0.53 to 0.38,and the simpson dominance index gradually decreases.The vegetation community in the rotation grazing area is simple and the species quantity distribution is uneven.The Euclidean distance from the stable point is 0.24,0.55 and 0.61 respectively in the rest grazing area,the free grazing area and the rotation grazing area,and the community in the rest grazing area is relatively stable.On the whole,the stability of plant community structure in the test area is poor and it is in the stage of succession.(3)The characteristics of community patches are significantly different under the three grazing modes.In the rest grazing area,the patch area of Achnatherum splendens occupies 91.15%of the total landscape area,and its CONTAG is up to 77.92,indicating a dominant patch;in the free grazing area,the aggregation degree of Convolvulus ammannii patch is the best,with the most dense spatial distribution;in the rotation grazing area,the patch area of Caragana accounts for 59.92%of the total area,indicating a dominant patch,and its SPLIT is up to 46.99,indicating a high degree of fragmentation in this area.Under the three grazing modes,the fractal dimension of the Caragana patch is 1.88,indicating the most irregular shape;the fractal dimension of Achnatherum splendens patch is 1.43,with the value close to 1.50,indicating poor stability.(4)Under the three grazing modes,the patch types mainly show a cluster distribution in the scale range of the sample plot,and occasionally present random distribution and uniform distribution in the small scale range,and the spatial correlation is complex.There is a weak correlation among the patches in the state of rest grazing and free grazing,and there is a phenomenon of competition for resources;under the state of rotation grazing,the correlation among the patches is good,forming a good pattern relationship.