Abstract: Cryptomeria fortunei plays a critical role in the vegetation of the Mountain Tianmu national nature reserve.However,decline has been observed in the Cryptomeria fortunei forests in recent years.Three typical plots of C.fortunei forests were set for surveys in order to understand the role of competition in the decline.C.fortunei was the sole dominant species,accounting for 58.79%-93.34% of the total area at breast height in the surveyed communities.C.fortunei in Laodian plot suffered the most serious competition with a mean competition index per tree(CI)being 4.35.The mean competition index per tree of Dashuwang plot was 0.58,the lowest among the three.Intra-specific competition of C.fortunei,which contributed 57.3%-69.6% of the total CI,was higher than the inter-specific.Dashuwang CI was negatively correlated with diameter at breast height.The present study indicates that competition,especially intra-specific,plays an important role in the decline of C.fortunei in the Mountain Tianmu national nature reserve.

Key words: Cryptomeria fortunei, intra-specific competition, inter-specific competition, competition index(CI), Mountain Tianmu national nature reserve