[Spatial structure of Quercus mongolica forest in Beijing Songshan Mountain Nature Reserve].

Based on the survey data of a 0.6 hm2 plot in Songshan Mountain Nature Reserve, and by using the uniform angle index, neighborhood comparison and mingling degree, this paper analyzed the spatial structural characteristics of Quercus mongolica forest in the Reserve. There were 10 populations in the tree layer of the forest, among which, Q. mongolica had the obvious advantage in population density and basal area, being the dominant and constructive species of the tree layer. The average mingling degree of the forest was 0.299, suggesting the low mingling degree of stands. The dominant species was mainly none- or less-mixed, while the accompanying species were generally well-mixed. In the spatial structural units, Q. mongolica and Pinus tabulaeformis populations were mainly of dominant, sub-dominant, and intermediate trees, accounting for 68% and 58% of the total plants of the populations, respectively, while the advantages of other populations were not obvious, being mostly of suppressed trees. The spatial pattern of the stands was of aggregative distribution, but the aggregation degree was not high and the aggregation scale was not large.