神农架巴山冷杉(Abies fargesii)林群落特征及其优势种群结构

Community characteristics and population structure of dominant species of Abies fargesii forests in Shennongjia National Nature Reserve

采用样方法对神农架自然保护区巴山冷杉林的群落组成、优势种群结构与动态进行了研究。结果表明,该群落具有明显的温带常绿针叶林特征,以中小型革质、单叶的常绿高位芽植物为主。群落成层现象明显,可划分为乔木层、灌木层和草本层,林下苔藓层发达。植物的科属组成较为分散,乔木层主要优势科有松科(Pinaceae)、桦木科(Betulaceae)、杜鹃花科(Ericaceae)、槭树科(Aceraceae)等。区系成分复杂分散,与温带植物区系关系密切。巴山冷杉是该群落的建群种,重要值达54.30%,幼苗储备丰富,占更新层的90.4%,但幼树缺失。巴山冷杉中小径级个体占多数(78.8%),为进展型种群。高度结构基本呈倒金字塔形,集中分布于8～10级3个高度级上(62.2%),10级个体最多,占29.3%。植株个体数随冠幅级的递增呈倒"J"形分布,冠幅小于20m2的植株占87.4%,其中5m2以下最多(30.8%)。冠幅与胸径呈指数相关,回归方程为y=2.7118e0.0308x,R2=0.520,冠幅与胸径的关系比与树高更密切。

The community composition of Abies fargesii and the population structure of dominant species in this community was studied using a sample plot method. The research plot was located in Shennongjia National Nature Reserve. Results showed that the appearance of community was characterized by evergreen phanerophytes plants with microphyll or mesophyll, coriaceous and single leaf. The vertical structure of the community can be clearly divided into four layers： tree layer, shrub layer, herb layer and developed moss layer. Dominant families of the community were Pinaceae, Betulaceae, Ericaceae and Aceraceae. The floral composition could be divided into 12 areal-types and 3 subtypes. North-temperate elements were plentiful, indicating that the community was closely related to that of the temperate zone. Abies fargesii was the outstanding dominant species in the community, especially in the tree layer; its importance value reached 54.3%. It suggested that Abies fargesii population was a developing population, as there were more seedlings and young trees than old trees. It was found that saplings were established more frequently in gaps than under the close canopy, which indicated a pattern of gap regeneration. The height structure of Abies fargesii population presented reverse pyramid shape, most individuals were 24 -30m high （62.2%） , and trees with heights between 27m and 30m accounted for 29.3%. Crown size structure of the population showed a typical reversed J shape. The individuals of Abies fargesii concentrated in small crown classes; 30.8% of them were smaller than 5m^2 and the 8th class was absent. 87.4% of the individuals developed crowns smaller than 20m^2, this was related to the features of conifer trees. An exponential correlation was observed between crown size and DBH, with a regression curve at y =2. 7118e^0.0308x ,R^2 =0. 520. The relation between crown size and DBH was more obvious than that between crown size and height.