湖北九宫山成熟常绿落叶阔叶混交林3种优势种的邻域效应研究

以最近邻株距离统计研究了湖北九宫山成熟常绿落叶阔叶混交林3种优势种青冈栎(Cyclobalanopsis glauca)、甜槠(Castanopsis eyrei)和短柄枹栎(Quercus serrata var.brevipetiolata)的邻域效应,进而探讨了局域尺度上的竞争/帮促关系与物种共存格局.结果显示,青冈栎、甜槠和短柄枹栎的最近邻株距离不存在下限;青冈栎的胸径大小与其种内最近邻株距离存在正相关(p=0.029),甜槠的胸径大小与种内、种间最近邻株距离均无相关性(p≥0.360),而短柄枹栎的胸径大小与种间最近邻株距离为负相关(p=0.040);3树种中任意一个的种内与种间最近邻株距离都没有显著差异(p≥0.122).这些结果表明,九宫山成熟常绿落叶阔叶混交林内邻域尺度上的竞争排斥并未充分激化,但是青冈栎的种内竞争仍然在起作用,而甜槠的竞争效应不明显,短柄枹栎则依赖种间帮促甚于相互竞争.同种和异种之间的排斥效果没有差异表明局域尺度的物种共存格局可能出于随机过程而非负密度制约过程.

Study on Neighbor Effects of Three Dominant Species in the Evergreen-deciduous Mixed Forest in Jiugongshan Natural Reserve

Neighbor effects of three dominant species Cyclobalanopsis glauca,Castanopsis eyrei and Quercus serrata var.brevipetiolata in an old-growth evergreen-deciduous mixed forest in Jiugongshan Natural Reserve were examined by nearest neighbor distance statistics,and the importance of competition/facilitation and implications for local species co-existence were explored.There were no lower limits of nearest neighbor distance for any species.The size（e.x.DBH） of Cyclobalanopsis glauca was positively correlated with its intraspecific nearest neighbor distance（p=0.029）,but the size of Quercus serrata var.brevipetiolata was negatively correlated with its interspecific nearest neighbor distance（p= 0.040）.No significant correlations were detected between size of Castanopsis eyrei and either of its interspeci-fic/intraspecific nearest neighbor distance（p≥0.360）.Intraspecific nearest neighbor distances differed insignificant from interspecific ones for all species（p≥ 0.122）.Our results imply that local competition has not been fully sharpened in the old-growth evergreen-deciduous mixed forest in Jiugongshan Natural Reserve.Neighbor effects were species-specific,with intraspecific competition in Cyclobalanopsis glauca being evident,competitive/facilitative effects of Castanopsis eyrei unobvious if not negligible,and dependence of Quercus serrata var.brevipetiolata on interspecific facilitation over competition.The insignificant differences between interspecific and intraspecific nearest neighbor distance for all species suggest that stochastic processes rather than negative density-dependent processes drove local species co-existence.