关键词: 同属比较, 生境异质性, 密度制约, 稀疏效应, 自疏效应

Abstract: [Objective] Based on massive data of two dominant species of Cyclobalanopsis in the same habitat, habitat heterogeneity anddensity-dependent effectsin subtropical evergreen-deciduous broadleaved mixed forest were analyzed to reveal interspecific differences andunderlining mechanism by comparing the distribution patterns of the two species, which laid the foundation to further reveal the role of community composition in maintenance mechanism of community species diversity.[Methods] Cyclobalanopsis multinervis (CYMU) and Cyclobalanopsis myrsinifolia (CYMY) were selected due totheir enormous abundances, extensive distributions, morphological similarity and of same genus in Mulinzi National Nature Reserve with 15 hm² large dynamic forest plot. After removing highly concentrated tillering plants, the twospecies were divided into three developmental phases:small trees (1 cm ≤ DBH< 10 cm), mediumtrees (10 cm ≤ DBH< 20 cm), andlarge trees (DBH ≥ 20 cm). The effects of habitat heterogeneity at 0-150 m anddensity-dependent effectsat 0-30 m on tree spatial pattern were analyzed using pairwise correlation functions g(r) and four models in point pattern analysis (completely spatial randomness, heterogeneous Poisson, antecedent condition and random labeling).[Results] The CYMU and CYMY were significantly aggregated on the scale of r>20 m because of habitat heterogeneity, nevertheless, CYMY were insensitive to habitat heterogeneity on the scale of 112-150 m. And the correlation of spatial pattern of CYMU and CYMY in the same developmental phase was g₁₂(r)≈1 on the scale of 1-150 m, which could be characterized as no correlation or negative correlation. While, two species tended to gather mutually at the small tree and mediumtree phases within 1 m and could not coexist at big tree phase. The thinning of density-dependent effects was not detected on the 0-30 m scale but had a slight effect on CYMU at its small tree phase, however, they all showed obvious density-limiting sparse effects at 0-10 m scale at the phase of small trees to medium-trees of CYMU and CYMY. Comparing CYMU and CYMY, the distribution pattern of small trees or mediumtrees showed no association to congeneric big trees on 0-30 m scales and big trees all showed Nurse Effect to congeneric small trees and medium-trees within 1 m, Moreover, the growing of big trees led to the sparsity of the congeneric small trees within 1-10 m.[Conclusions] In the populations of CYMU and CYMY, the mechanisms of thinning density dependent, self-thinning density dependent and distance dependent were basically the same. The difference was that small trees of CYMU tended to stay away from big trees, while small trees of CYMY gathered slightly around big trees on a small scale. CYMU and CYMY could coexist wellon a small scale, and habitat heterogeneity was the important basis for widespread coexistence for the two species on medium and large scale. Our researchresults could provide guidance for community restoration, diversity protection andforest management insubtropical evergreen-deciduous broadleaved mixed forest of Mulinzi Nature Reserve.

Key words: comparison of congener, habitat heterogeneity, density-dependent effects, self-thinning, thinning