四明山常绿阔叶次生林不同海拔群落生态位与物种联结特征OA

[Objective]As the core area of the ecological restoration project of the Grand Canal in eastern Zhejiang,Siming Mountain holds significant importance for maintaining local biodiversity,conserving water re-sources,regulating climate,and preventing soil erosion.Nevertheless,studies specifically targeting the community assembly mechanisms in this area are still relatively insufficient.This paper aimed to uncover the differentiation pat-terns of forest community composition,niche and inter-specific relationships at different altitudes of Siming Moun-tain,thus clarifying the construction mechanism of forest communities.[Method]A total of 20 forest sample plots were set up at different altitudes(low and high)of Siming Mountain.After surveying the community characteristics,the altitude-driven community construction mechanisms were expounded through the analysis of species niche breadth,niche overlap,and inter-specific associations.[Result]The importance values of dominant species across tree and shrub layers showed differences between high and low altitudes,supporting the"altitude niche differentiation hypothesis".In low-altitude zones,Cyclobalanopsis glauca dominated the tree layer,while Camellia fraterna pre-vailed in the shrub layer.At high altitudes,Pterostyrax corymbosus became the tree-layer dominant,while C.frater-na and Rhododendron ovatum comprised the main body of shrub-layer.Litsea coreana and Quercus glandulifera were arboreal species spanning across altitudes,and their importance values increased with altitude.Niche breadth of dominant species expanded consistently with altitude,and niche differentiation among species was more pronounced at high altitudes than at low elevations.The forest community exhibited overall positive interspecific associations(VR>1),with association strength strengthening at high altitudes(VR=1.08 vs.1.49).The tree layer maintained high Ochiai indices(OI>0.5)and low negative association rates,suggesting competition avoidance via niche dif-ferentiation,whereas the shrub layer showed low OI(OI<0.5)and high negative association rates,indicating obvi-ous competitive exclusion.[Conclusion]Altitude affects forest community assembly by regulating niche differentia-tion of key species and the intensity of interspecific interactions.At high altitudes,community stability is maintained by the synergy between niche differentiation and strong positive interspecific associations,whereas low-altitude communities rely on competitive interactions among species with high niche overlap to sustain structural organization.