Characteristics and significance of the remnant evergreen broad-leaved forest in the urban area of Chongqing, China
重庆都市区残存常绿阔叶林的群落特征及其意义

As a consequence of extensive urban development and intensive human activities,the vegetation has been damaged severely in the urban area of Chongqing Municipality and only some natural forest patches remain on the Pingxing Mountain Ridges in eastern Sichuan Basin.The forest in Tieshanping National Forest Park in the core of Chongqing is the only well-protected typical evergreen broadleaved forest at lower alti-tude in mid-subtropical China.In 2006,we established a 0.2-hm2 permanent plot(29?37.606' N,106?41.737' E) and divided it into 20 subplots,then conducted a detailed community survey.A total of 58 species of vas-cular plants were recorded in the community,belonging to 46 genera and 32 families.Of these,there were 39 monotypic genera and 20 monotypic families.The analysis of floristic geographical elements indicated that the tropical elements were dominant but that temperate affinities also existed in the community.An analysis of life form spectra and leaf characters showed that the physiognomy of the community was characterized by phanerophytes with meso-and microphyllic-leathery simple leaves.In this community,four distinct layers were distinguished from the forest floor to the canopy,namely ground vegetation,shrub layer,sub-tree layer and tree layer,respectively.Castanopsis carlesii var.spinusa,with relative dominance of 73.4%,was the only dominant species in the community,whose population structure showed an uninterrupted pattern.The forest could regenerate through seedlings and also root sprouts,which implies that the community could maintain itself for a long time if there is no intensive disturbances.