深圳市径心水库区苏铁蕨群落结构特征及演替分析

苏铁蕨(Brainea insignis)最早出现于古生代泥盆纪,是重要孑遗种和珍稀濒危植物,对研究古植物区系及蕨类植物的起源和演化具有重要意义。该研究采用相邻格子法对深圳市径心水库区的苏铁蕨群落进行群落学研究,分析径心水库区苏铁蕨群落结构和演替特点,为苏铁蕨的保护提供理论和实践依据。结果表明:(1)深圳径心水库区的苏铁蕨群落属于南亚热带常绿阔叶林,在1 600m2的样地中共有维管束植物72种,隶属于45科66属,其中种类组成以热带成分占绝对优势,占非世界属的88.33%。(2)该苏铁蕨群落垂直结构明显,可划分为乔木2亚层、灌木层和草本层,层间植物较丰富;各种群的重要值分析表明,鸭脚木(Schefflera octophylla)、苏铁蕨(Brainea insignis)、九节(Psychotria rubra)、鼠刺(Itea chinensis)、银柴(Aporusa dioica)是该群落的主要优势种,其重要值分别为:53%、38%、28%、23%和22%。(3)年龄结构分析表明,主要优势种群如银柴、鼠刺和豺皮樟(Litsea rotundifolia)等均属于增长型种群,而苏铁蕨种群却呈现出一定的衰退趋势,说明该群落正处在旺盛发展阶段并且会不断演化替换掉苏铁蕨种群。(4)该研究区群落种群的频度规律为A级B级C级D级E级,与Raunkiaer的L形频度定律曲线相一致;与其他邻近地区进行比较,深圳径心水库区的苏铁蕨群落显示出较低的物种丰富度,可能是受海风和人类活动的影响比较大,应对该苏铁蕨群落进行适当的干预和保育,清理上层枯枝枯藤,加强林内透视度,增加光照。

Structure Characteristics and Succession Analysis of Brainea insignis Community in Jingxin Reservoir Area

The earliest origin of Brainea insignis, an important relict species and national rare and endangered plant, could be traced to Devonian of Paleozoic. Its evolutionary process is significant to study the palaeoflora and the origin and evolution of ferns. In order to provide theory and practice basis for the protection of B. insignis, we investigated and analyzed the characteristics of floristic composition, physiognomy, structure, species diversity and succession of B. insignis community in Jingxin reservoir area of Shenzhen City by using method of standard plot, which the results shows as following: (1) B. insignis community in Jingxin reservoir area belongs to the subtropical evergreen broad leaved forests with 72 species of vascular plants belonging to 66 genera and 45 families in the 16 quadrats of 1 600 m². Except for cosmopolitan, the geographical elements of genera are predominated by tropical one, accounting for 88.33% of total of non world genera. (2) The vertical structure of community can be divided into tree layer (with two sub layers), shrub layer and herb layer, and the liana among layers are abundant. Based on analysis of the importance value of different populations, it indicates that the Schefflera octophylla, B. insignis, Psychotria rubra, Itea chinensis and Aporusa dioica are belonged to dominant populations, and the important values are 53%, 38%, 28%, 23% and 22%, respectively. (3) Based on analysis of age structure, A. dioica, I. chinensis and Litsea rotundifolia populations all belong to the increasing population, but B. insignis population belongs to the declining population. These population age structures indicated that the community is situated with a vigorous development stage and the B. insignis population will be eliminated as time goes on. And (4) the frequency distribution law of the community in the study area is A >B >C >D < E, which is in accordance with the L shaped curve of Raunkiaer. By comparing with those of other neighboring regions, the B. insignis community in Jingxin reservoir area of Shenzhen City shows the lower species richness, which is likely to affected by the sea breeze and human activities, so the necessary intervention and measures should be taken to protect the B. insignis community on some extant, for example, to eliminate upper deadwood, withered vine, and strengthen transparency under forest, so as to obtain more illumination.