Community Feature And Its Structuring Mechanism Of Representative Forests In Five National Nature Reserves, Zhejiang Province, East China

We established5one-ha (100×100m) forest dynamics plots (FDPs) in five nature reserves of Zhejiang province according to the protocols of Center for Tropical Forest Sciences (CTFS), These FDPs are Qingliangfeng (QLF), Jiulongshan (JLS), Fengyangshan (FYS), Baishanzu (BSZ) and Wuyanling (WYL), named after the nature reserves they locate in. In each FDP, we mapped, tagged and identified all free-standing stems with diameter at breast height (DBH)≥1cm. We analyzed the community compositions, size structure and population structures. And we cunducted spatial pattern analysis, redundancy analysis (RDA), principal coordinates of neighbor matrices (PCNM) and spatial point pattern modeling to estimate the ecological processes that affected the assembly of the these forest communities. The results showed that:(1) In total, we recorded270species belonging to50genera and116families in which gymnosperms composed8species (7genera and5families) and angiosperms composed262species (109genera and45families). Among these FDPs, WYL was highest in richness, while QLF was lowest. Community similarities (Jaccard index) between WYL, JLS and BSZ were the highest, possibily due to their geographical closeness and similar attitudes. Community similarities between QLF, WYL and BSZ were the lowest, may be due to their geographical remoteness.(2) Following the floristic distribution division principle of Wu (1991,2003), we classified the50genera and116families into12areal types. At the family level, regardless of analyzing the FDPs together or individually, the numbers of tropic elements were larger than the numbers of temperate elements. Besides, under the premise of small differences in FDP attitudes, the number of tropic elements increased gradually from north to south, while the temperate elements gradually reduced.(3) Comparing the importance values (IVs) of species within each FDP, we found that all the5FDPs were with obvious dominant species. When species were ranked according to IV, the first species usually accounted for>10%of the total IV, and the first15species accounted for>50%of the total IV. The dominant species were mostly from families like Theaceae, Fagaceae, Lauraceae, indicated these forests are typical mid-subtropical forests.(4) The DBH size structures of populations of all the species and of each grow form group generally showed the reverse ’J’ shape, indicating good community regeneration. Population structures of the dominant species showed the reverse ’J’, skewed Gaussian or Gaussian shapes, and indicated no signs of population depression.(5) All the common species in each FDP showed aggregated spatial distribution patterns at the small scales (0-10m). However, with the increase in spatial scale, the species increasingly exhibited random or regular distribution patterns.(6) Negative density dependence (NDD) was detected in all five FDPs. But NDD was not prevalent in each FDP. In the FDP where NDD was most prevalent, we found the maximal strengths of NDDs were negatively related to species abundance, and positively related to the strengths of conspecific aggregations.(7) Habitat filtering might not be important in influencing community assembly after the stems reach1cm in DBH within these FDPs.