重庆都市区残存常绿阔叶林的群落特征及其意义

重庆市是近年来中国经济发展的热点地区之一, 处于快速城市化进程之中。其都市区植被受到严重的破坏, 仅在平行山岭上残存有少量的自然植被。铁山坪国家森林公园内残存的常绿阔叶林是中亚热带低海拔地区典型的常绿阔叶林, 也是重庆都市区核心区内唯一保存较好的自然常绿阔叶林片断。作者选择代表性地段设置了2,000 m2的永久样方, 进行了详细的群落学调查, 在此基础上, 对群落的物种组成、外貌以及结构特征等进行了分析。结果表明, 群落中共出现维管植物58种, 分属32科46属, 单种科和单种属的数量大, 分别为20和39个。物种的区系地理成分相对简单, 以热带植物区系成分占优势, 同时温带和东亚植物区系成分也占较大比例。群落外貌由小型和中型革质单叶的高位芽植物所决定, 中型革质单叶的高位芽植物所占比例相对较高。群落垂直空间分化明显, 可以分为乔木层、亚乔木层、灌木层和林床, 树冠分布较为连续。刺果米槠(Castanopsis carlesii var. spinusa)为群落的唯一优势种, 其相对优势度达到73.38%, 且更新连续。群落木本层多样性指数(Shannon-Wiener指数)较低, 为1.75, 而林床则达到3.96。对该群落的生活型组成、叶性质以及主要种的种群结构的分析表明该群落属较为成熟的湿润型常绿阔叶林类型。作为重庆都市区内宝贵的乡土物种基因库和资源库, 该残存常绿阔叶林在区域生物多样性的保护中具有重要的价值。

Characteristics and significance of the remnant evergreen broad-leaved forest in the urban area of Chongqing, China

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 altitude 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 vascular 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.