[Community structure of Quercus aliena var acuteserrata forest in the Taibai Mountain, China]

Qinling Mountains are biodiversity hotspots in China, with rich vegetation resources and species diversity. To clarify the mechanism underlying biodiversity maintenance during vegetation restoration in this area, we established two permanent plots with each area of 100 m×150 m in the Q. aliena var. acuteserrata secondary forest (SF) and primary forest (PF) in the northern slope of Taibai Mountain in 2016, following the standardized protocols by CTFS (the Center for Tropical Forest Science). We analyzed community composition and structure with measuring all trees with DBH ≥ 1 cm. 2839 and 2840 trees were recorded in the SF and PF plots, respectively. Trees in those two plots belong to 29 families, 45 genera, 65 species and 21 families, 37 genera, 47 species, respectively. The proportions of occasional species and rare species were 38.4% and 24.6% in the SF plot, and 40.4% and 19.2% in the PF plot. Most of the trees were distributed in northern temperate zones, and the proportions of genera were 46.6% and 48.7% in the SF and PF plots, respectively. The diameter of Q. aliena var. acuteserrata in both plots followed a unimodal distribution (more young trees than old ones). The diameter distributions of companion species (e.g., Sorbus alnifolia, Acer davidii, Cornus kousa, and Staphylea holocarpa) were inverted "J" shapes, indicating that those populations could have complete life history. In the pair correlation function g(r) analyses, the aggregation of dominant species were the strongest at 0-2 m scale in the two plots when r=10 m. The degree of aggregation gradually weakened with increasing scale. The population distribution patterns of the dominant species were random or uniform when the scale increased to certain value. The average uniform angle index (W) were 0.56 and 0.58 in the SF and PF, respectively. Trees in the communities followed an aggregated distribution. The average W of the community and dominant species in the SF were smaller than that in the PF, indicating weaker species aggregation in the SF. The average dominance in the SF and PF was both 0.47, indicating that the stands were in a co-dominant state. The average mingling was 0.70 and 0.57 in the SF and PF, respectively, which belonged to high and moderate mingling. Species richness, community stability and spatial distribution patterns of forest community could be affected by human disturbance. The role of interspecific interaction, effects of habitat heterogeneity on species coexistence, and variation of community structure should be considered during vegetation restoration of disturbed forest community.