Comparing Various Small Spatial Scales Used When Analyzing The Spatial Heterogeneity In Three Types Grassland Community By Power Law Model

Research of ecosystem depends on the ecological process within a time and space.The problem of ecological phenomenon,in scale,in the degree of interconnection,the measurement of cross-scale and the change of the same phenomenon at different scales,is all extremely important.These problems are the basis for analyzing any ecosystem.To change scales diversifies the manifestations of spatial heterogeneity,causing the spatial heterogeneity increasing,reducing or even disappearing.Exploring scientific matters on a small scale leads to a more detailed and microcosmic result,while conversely,investigation on a large scale gives us a more macroscopic result.A small change in scale could lead to the changing in diversity of species,species richness and spatial distribution of biomass.These changings could impact on the emergence and growth of plant species and the composition and structure of plant communities.However,the studies of grassland community spatial heterogeneity above,are almost all respectively limited to a single scale.Our research adopted the"binary occurrences"field survey method(plant species in the quadrats appearing were recorded as"1",non-appearing were recorded as"0")combined with the analytical method of power law model,to conduct a field survey with a large number of quadrats(1600 quadrats with the area of 0.25 m×0.25 m each),discussing the variation of spatial heterogeneity of the grassland community on different spatial scales in a natural grassland community.Conclusion1.Power law model is fitted for spatial pattern of the frequency of occurrence on varies scales.2.Variation trend of the spatial heterogeneity index value(?_i)of dominant species is consistent with the integral spatial heterogeneity index value(?_c)of the grassland community.3.The spatial heterogeneity index changes with the species diversity index in three kinds of grassland communities.4.With the increase of the spatial scales,spatial heterogeneity index value(?_c)goes up first,peaking at a certain point on a scale defined by 0.25 m~2(0.5 m×0.5 m)quadrats,and then goes down.Therefore,0.25 m~2 is the best area of a quadrat to choose to conduct the survey,since it can manifest the most spatial heterogeneity of the grassland community.