画稿溪自然保护区桫椤(Alsophila spinulosa)群落乔木层的物种组成与结构

Species composition and structure of the tree layer of Alsophila spinulosa community in the Huagaoxi National Nature Reserve,Sichuan

桫椤是世界上珍稀濒危植物之一.为了对生物多样性进行长期监测与研究,在画稿溪保护区建立了2 hm^(2)监测样地,分析样地乔木层(H≥3 m)的物种组成、物种密度、径级结构和高度结构,结果表明,乔木层有3498株,隶属39科56属87种.群落中桫椤(Alsophila spinulosa)、八角枫(Alangium chinense)、赤杨叶(Alniphyllum fortunei)、杉木(Cunninghamia lanceolata)和润楠(Machilus pingii)重要值分别为22.58%、8.53%、8.24%、6.27%、4.87%和4.63%,桫椤占绝对优势.乔木层最大密度为69株/100 m^(2),最小密度为1株/100 m^(2),平均密度约为18株/100 m^(2).样地内具有较多的幼树和幼苗,种群能够自我更新且群落较为稳定.桫椤主要分布在乔木中下层,有一定数量的幼苗库.由于临时样地面积小、监测时间短,不足以认识桫椤群落水平上生物多样性维持机制.本研究首次对2 hm^(2)监测样地进行调查并分析物种组成、物种密度、径级结构和高度结构,结果可为生物多样性长期监测与研究提供有效的理论依据.

Alsophila spinulosa is a rare,endangered plant.For long-term monitoring and research of biodiversity,we established a monitoring plot(area,2 hm^(2))in the Huagaoxi National Nature Reserve and investigated species composition,diameter at breast height(DBH),and height structures of trees(H≥3 m).T he r esults showed that the monitoring plot consisted of 3498 individuals,belonging to 39 families,56 genera,and 87 species.The importance value indexes of Alsophila spinulosa,Alangium chinense,Alniphyllum fortune,Cunninghamia lanceolata,and Machilus pingii were 22.58%,8.53%,8.24%,6.27%,and 4.63%,respectively.A.spinulosa had an obvious advantage in terms of the population,and the monitoring plot was considered an A.spinulosa community.The maximum,minimum,and average densities in the monitoring plot were 69 individuals/100 m^(2),1 individual/100 m^(2),and 18 individuals/100 m^(2).The species was abundant in saplings and seedlings,the population could self-regenerate,and the A.spinulosa community could stabilize.A.spinulosa was mainly distributed in the lower and middle layers of trees and was abundant in the seedling banks.At present,the temporary plot is relatively small in size and has been monitored over a relatively short period,which is insufficient to understand the mechanism of biodiversity maintenance at the community level.This study is the first to survey and analyze the species composition,species density,diameter grade structure,and height structure of a 2 hm^(2)monitoring plot,thus providing an effective theoretical basis for long-term monitoring and research of biodiversity.