Study On Multi-scale Vegetation Spatial Patterns And Its Responses To Different Disturbances Of Hulunber Steppe

Spatial pattern of ecological systems and ecological processes at different scales, and their relationship are central issues of ecology. Disturbance as part of the process, is the main sources of spatial heterogeneity, which can significantly change the ecological pattern and processes at different scales, causing apparently shift of the structure and function of ecological systems. Hulunber steppe with the unique ecosystem characteristics, relatively well-preserved natural environment, abundant landscape types and biodiversity, relatively advanced and intensive production mode, is the optimal object for researching the natural ecological patterns and process in steppe ecosystems, and its responses to human-caused disturbances.It may benefit for expanding the field of vegetation ecology, providing a scientific basis for grassland resources utilization and protection, establishing ecosystem management scheme reasonably, and has important practical significance for restoration and reconstruction of degraded grassland so that formulating livestock development plan by systematically and thoroughly study of multi-scale vegetation patterns and its responses to disturbances.This paper took Hulunber steppe as research object, made use of field survey data and community patterns at landscape, community and population scales, diversity analysis methods, point pattern analysis, fractal analysis and regression analysis methods has been used to analysis vegetation spatial patterns and ecological processes, and its responses to disturbances at different scales. The main results were as followed.The first part, the pattern of biodiversity and productivity was analysised at landscape scale. The results showed that: there were no old and endemic species in Hulunber steppe. There were 135 species of vascular plants, which belonged to 28 families and 93 genera in the study area. Floristic composition of constructive species did not change significantly. The species richness and aboveground biomass increased with the longitude gradient. The relationship between biodiversity and aboveground biomass was unimodal.The second part, the association patch pattern was studied at community scale. The results showed that: there were 92 species of vascular plants, which belonged to 22 families and 66 genera in the study area. Indices of community structure and function were significantly different, and the community status located in different successional stages because of different disturbances. Species niche and succesional stages were different between sample plots, so as the number of patches were significantly different. The level of Korcak patchness exponent value, which expressed area distribution, was not only related to patch area, but also related to evenness of patch. The value of Perimeter-area exponent, which expressed the complexity of patch boundaries, was due to the niche of association patch and species diffusion. The stability of community not only lied on the direction and stages of community succession, but also lied on the starting position and the special attribution of dominant species, such as reproduction.The third part, the species spatial pattern was analysised at population scale. The results showed that: there were no consistent relationship between the root cover of species and population point pattern, spatial association. The population spatial pattern was no significant difference in experimental sample plots and in different treatment of same sample plot, and the population spatial pattern of the same treatments in same sample plots was not consistent, related to the community properties, changed in microhabitat and the intensity of disturbance. The population spatial pattern depended on the type of the species'life forms in the special scale. The types of population distribution pattern were influenced by the species themselves, the species niche in communities, the different microhabitat, the interaction between species, outside disturbances, and the anti-disturbances ability of species. Control factors of population pattern were just different in different sample plots and disturbances. From the plant's-eye view, herbages may interact in centimeter range. The nature of spatial structure appeared to depend on the scale of observation, but the smaller-scale data were more likely to provide a biologically interpretable measure of local spatial structure in this community. So, it was a positive meaning in studying population pattern and dynamics by selection of the 2×2 cm as the smallest sampling unit.The fourth part, the synthetical mode of vegetation pattern was discussed at multi-scale. The results showed that: they were different for studying vegetation at different scale. From the plant's-eye view, spatial pattern was due to characteristics of the species itself and randomcity at population scale. Species competition and diffusion determined interspecific relationship and complexity of community, species composition of community was determined by local species pool at community scale. Species composition of community was determined by regional species pool at landscape scale. The edificators of plant communities were all determined by characteristics of the species itself at different scale. From the environment's-eye view, climate determined zonal vegetation pattern, but the local condition determined the distribution of azonal vegetation, which could interpret existance of outlier.