Maintaining mechanism of tree diversity in a secondary conifer and broadleaf mixed forest in Changbai Mountains

The formation and maintaining mechanism of biodiversity of the temperate forests is still open to theoretical discussion. The effects of 21 tree species on local community diversity were examined by individual species-area relationship model. The results showed that: 1) the effect of different tree species on the local diversity pattern was different. Betula platyphylla, Fraxinus mandshurica, Larix olgensis, Maackia amurensis, Picea jezoen, Pinus koraiensis, Populus cathayana, Populus davidiana, Symplocarpus foetidus, Tilia amurensis, Ulmus davidiana var. japonica, Acer mono, Acer tegmentosum and Acer ukurunduense acted as diversity accumulators at all studied spatial scales, Acer pseudo- sieboldianum and Betula costata as diversity repellers, Phellodendron amurense and Quercus mongolica as neutral at most spatial scales, and Ulmus laciniata and Tilia mandschurica as diversity repellers only at some spatial scales. 2) The proportion of diversity accumulators declined with increasing scales. However, it was still higher than that of repellers and neutrals at all studied scales of 0-50 m, indicating that it was significantly scale-dependent. The proportion of repellers and neutrals always stayed at about 20%. Therefore, diversity accumulators played a determinant role in the structuring processes of community diversity in the secondary conifer and broadleaf mixed forest. Our result indicated that niche theory plays an important role in maintaining species diversity in temperate forest community. Meanwhile, the function of random processes represented by neutral species in the construction of community structure should not be ignored.