| Topography is one of the most important factors that can determine the structure of theplant community, and the diversity of the plants affect the flow in the landscape at differentscales. Analysis on the relationship between the plants and the topography is essential to learnthe function and the process of the ecosystem as they have strong correlation at different scales.Superposition of geographic information of the digital elevation model (DEM) and maps oflandscape genres is weighed in this article to mirror the spatial distribution of the plantcommunities at different slops, aspects and position. Then the quantified correlation of thetopographic factors and the distribution of the plants is gained through the structure of thisspatial distribution of the plant communities. Calculations of the proportion of the main treespecies (Quercus mongolica, Ulmus pumila, Fraxinus mandshurica, Juglans mandshurica) atdifferent grades of the topographic factors (slope, aspect and position) in the secondary forestin the region of Laoyeling are done, on the base of modules of Arcgis, 3D and the extendmodule of spatial analysis, in order to discuss the distribution of these tree species. The resultindicated that the average slope of the plots is between 10.2～22.5 in the research area. Thereare five levels for the aspect of the slope, and marked differences are showed in slope andaspect. The scales of the spatial heterogeneity are 31.2m, 161.6m and 17.3m respectively,according to the semi variance analysis of topographic factors such as slope and aspect as wellas species composition of the plant community. The scale of topographic factor is much largerthan that of the species composition. This demonstrates topographic factor is not the onlyfactor that affects the species composition of the plant community at the small scale. Thenugget variance of semi variance of slope and aspect were 9610 and 2172. The high value ofnugget variance indicated that the influence of topographic factor in the small scale could notbe ignored. The topographic adaptation of these species was different, and according to theirrespect to topography, these nine species were classified into four groups using hierarchicalcluster analysis. Therefore, the species composition of a community is affected by a variety offactors, and this effect can be reflected by the variety of topography. This paper discussed therelationship of flowaccumulation with soil moisture and tree distribution pattern in thewatershed of Zhangjiagou—a typical small catchment on the platform of GIS which cancalculate the flowaccumulation and topographic index from digitizing topographic map todepict the topographic hydrologic characters with field survey and anlysis. The result is thatwhen the size of grid is 10m×10m or 12m×12m, there is a significant positive correlationbetween the flowaccumulation and soil moisture with the correlation coefficient of 0.819 or0.8705; when the size of grid is 18m×18m, there is no significant correlation with the size of grid is small. Most of the trees in the research distributes in the area which has little value offlowaccumulation, But on the account for the proportion to each tree, the spatial distributionpattern of Acer mono, Fraxinus mandshurica and Phellodendron amurense show strongcorrelation with the flowaccumulation, while Quercus mongolica, Ulmus pumila, Tilia, Betulaplatyphylla and Juglans mandshurica show weaker. ANOVA result of community speciesdiversity index in different layers explicited the significant difference between different plantarchitecture. The trends ofαdiversity index showed trees＞shrubs＞grass, and the trees hadthe most significant impact on the structure,appearance and dynamics of the three. We alsoexamined the impact of the topographical factors toαdiversity index, the order was that slopeaspect＞slope position＞slope gradient＞elevation＞slope surface＞slope type, the resultsshowed that the spatial pattern of biodiversiy was significantly affected by local landform, andthe elevation did not show significant effect.
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