The Topographic Variation And Environmental Interpretation Of Hulun Buir Steppe Community Spatial Pattern

Hulun Buir steppe located in the eastern part of Inner Mongolian, which belongs to plateau landscape, is a component of the Mongolian Plateau of central Asia. The elevation of the steppe is almost over 600 meters, and the ground-surface undulated because of the hilly landscape. Water zone is presented in the area because of the transition of sub-humid to semi-arid climate from the east to west.Coupled with complex terrain small changes, the region of ecological space expanded greatly, and the relationship between vegetation and environment present complicated and changeable trends. The research discussed the effect of the terrain and the factor of soil-environment on the structure of Hulun Buir steppe communities. The main content includes three aspects as follow:The first part, the analysis of the relationship between steppe communities structure and environment factor have been done by the ordination and classification methods. Based on the field experiment of 2006, combining TWINSPAN and DCA, a hundred plots have been applied to classification and ordination. The result showed that: the study regional vegetation communities can be divided into 13 Association groups, according to both the principle and system of Chinese vegetation classification and the ecological data analysis of field investigation and habitat characteristics. The results of the different communities in order axis position reflect the relationship between community with basic environmental gradient by the analysis of DCA ordination method to Species abundance matrix and soil-terrain environment factors. And total soil nitrogen, effective potassium and nitrogen, available phosphorus, organic matter and the slope shape decide the changes of the communities niche, which lead to changes of the communities types distribution gradient.The second part, DCCA ordination was used to partition the soil and topographic factors which affected the plant community distribution in Hulun Buir steppe. The results showed that the pure soil environment factors can explain 13% of the species diversity change, and the pure topographic factors can explain 13% of the species diversity change. 5% can be explained by the latter two factors and the unexplainable parts was 75%. Topographic factors played an important role to community structure by affecting the reallocation of the hydro-thermal combination. According to this result, we established the vegetation pattern and topography diversity conception model based on DEM, and simulated the plant community structure distribution pattern. The KAPPA consistency test was used to check up the precision of the simulation results according to land survey community type map. The accuracy of KAPPA consistency test was 0.45 which showed the model had a good simulation effect.The third part, we study on the relation between spatial structure and species abundance distribution in community by using trend surface analysis, which is based CCA(Canonical Correspondence Analysis) and interpolation method. The result showed that: in the study area ,the community structure can be inosculated well in the species space of community and the physics space. Community structure is affect by certain mechanism controlled by spatial structure.