神农架天然针阔混交林的物种组成和群落结构

Species composition and community structure of natural mixed needle-and broad-leaved forest in Shennongjia

天然针阔混交林是神农架山地的垂直地带性植被,具有重要的生态和经济功能。为深入了解天然针阔混交林群落的结构和动态、物种多样性维持机制,在湖北省神农架国家级自然保护区内建立了1 hm2的森林动态监测样地,分析了其物种组成、径级结构和主要优势种的空间分布特征。结果表明:样地内记录到存活个体5321株,隶属于14科26属44种,其中针叶树种相对单一,只有巴山冷杉(Abies fargesii)和华山松(Pinus armandii);巴山冷杉、华中山楂(Crataegus wilsonii)和山杨(Populus davidiana)的重要值之和为50.28%,其他阔叶树种的重要值之和为46.06%;群落的径级结构近似倒"J"型,幼树储备丰富,重要值排名前3的优势种中巴山冷杉和华中山楂的径级结构均近似倒"J"型,更新良好,但山杨的径级结构近正态分布,更新不良,种群有衰退的趋势;巴山冷杉、华中山楂和山杨表现出明显的生境偏好,随着尺度的增加,华中山楂和山杨均为聚集分布,而巴山冷杉则依次呈现聚集分布、随机分布和均匀分布;神农架针阔混交林阔叶树种丰富度远比针叶树种高,但从重要值排名前3的优势种来看,针、阔叶树种重要值基本相当,群落结构总体稳定。

The natural needle-and broad-leaved mixed forest is a vertical zonal vegetation in the Shennongjia Mountains,with important ecological and economic values. To gain insights into the structure,dynamics,and the maintenance of species diversity of the natural mixed needle-and broad-leaf forest community,a 1-hm2 forest plot was established in Shennongjia National Nature Reserve,Hubei Province. The species composition,size-class structure of diameter at breast height( DBH),and spatial distribution of dominant species were analyzed. A total of 5321 living individuals were recorded in the plot,belonging to 44 species,26 genera,and 14 families. There were very few conifer species,with only Abies fargesii and Pinus armandii present in the plot. The total importance values of Abies fargesii,Crataegus wilsonii and Populus davidiana was 50.28%,and that of other broad-leaved species was 46.06%. The DBH class structure showed a reversed"J"shape with abundant saplings in the understory. Among the top three dominant species with respect to importance value,both Abies fargesii and Crataegus wilsonii had a DBH class structure of reversed "J"shape,indicating their regeneration status were good. On the contrary,the sizeclass structure of DBH of Populus davidiana was close to the normal distribution,the saplings were scarce,and the population had a tendency to decline. Abies fargesii,Crataegus wilsonii and Populus davidiana showed obvious habitat preference. With the increases of sampling scale size,Crataegus wilsonii and Populus davidiana did not change their aggregated distribution,while the spatial distribution of Abies fargesii changed from a clustered,via a random,to a uniform distribution. The species richness of broad-leaved trees was higher than that of coniferous trees in the mixed needle-and broad-leaved forest in Shennongjia. However,if only the top three dominant species on the importance value sorting list were considered,the importance values of needle-and broad-leaved species were similar and the community structure was stable.