Abstract: The monsoon evergreen broadleaved forest (MEBF) in Dinghushan Nature Reserve (DNR) has been considered as a zonal vegetation in lower subtropical China,with a history of more than 400 years.In this paper,the intra- and interspecific competition intensity in Cryptocarya concinna,one of the constructive species in MEBF in DNR was quantitatively analyzed by Hegyi single-tree competition index model.The results showed that the intraspecific competition intensity in C.concinna decreased gradually with increasing tree diameter.For C.concinna,its intraspecific competition was weaker than its interspecific competition with Aporosa yunnanensis.The competition intensity of interspecific competition with C.concinna followed the order of A.yunnanensis > Schima superba > Gironniera subaequalis > Acmena acuminatissima > Castanopsis chinensis >Syzygium rehderianum >Pygeum topengii > Blastus cochinchinensis >Sarcosperma laurinum > Pterospermum lanceaefolium > Cryptocarya chinensis.The relationship of the DBH of objective tree and the competition intensity between competitive tree and objective tree in the whole forest and C.concinna population nearly conformed to power function,while that between other competitive tree and the objective C.concinna tree conformed to logarithm function.There was a significantly negative correlation between the competition intensity and the DBH of objective tree.

Key words: geographic variation, stable carbon isotope, provenance., hydrothermal factor