梵净山森林群落林下草本植物组成及多样性格局

Understory herbaceous composition and diversity patterns of forest community in Fanjingshan mountain

【目的】草本植物作为森林生态系统的组成部分,在维持生物多样性、调节生态系统结构和功能方面发挥着重要作用。为明晰梵净山林下草本植物组成、多样性特征及其影响因素,为生物多样性保护,森林生态系统管理和森林健康评价提供科学依据。【方法】采用典型样方法在梵净山634~2382 m海拔范围内设置了15个30 m×30 m森林群落固定样地,调查了林下草本植物物种组成,分析了草本植物多样性与海拔和林分密度因子的相关关系。同时,揭示了草本植物α、β多样性沿海拔梯度和林分密度的变化规律,探讨了影响草本植物多样性的环境因子。【结果】1)15个森林群落固定样地一共记录到草本维管束植物50科97属146种,其中:蕨类植物10科20属44种,被子植物40科77属102种。优势科主要有鳞毛蕨科Dryopteridaceae、蹄盖蕨科Athyriaceae、菊科Asteraceae、兰科Orchidaceae、天门冬科Asparagaceae和水龙骨科Polypodiaceae,所含种数占总种数的38.36%。不同群落草本植物种类和重要值均存在差异,草本植物种类变幅为2~40,8号样地最多,14号样地最少。草本植物重要值变幅为0.31~58.21,其中蕨类植物重要值总体较高,偶见种或伴生种占比较低。2)草本植物Margalef指数(0.43~5.50)、Simpson指数(0.18~0.88)、Shannon-Wiener指数(0.33~2.59)和Pielou指数(0.46~0.83)随海拔升高或林分密度增大均无明显变化规律。回归分析显示,除Pielou指数外,Margalef指数、Simpson指数和Shannon-Wiener指数与海拔呈较弱的负相关关系。Margalef指数、Simpson指数、Shannon-Wiener指数和Pielou指数与林分密度呈较弱的正相关关系。3)Jaccard指数随海拔梯度升高总体呈下降趋势,表明物种替代速率随着海拔升高逐渐加快,Cody指数随海拔升高呈上升趋势。Jaccard指数和Cody指数随林分密度增大上下波动,无明显变化规律。【结论】海拔和林分密度是影响梵净山森林群落林下草本植物多样性的生态因子,但二者与多样性指数的相关性不强,在草本植物多样性形成和维持方面并未发挥主导性作用。

【Objective】As a component of forest ecosystem,understory herbaceous play an important role in maintaining biodiversity and coordinating structure and function of ecosystem.The aim of this study is to clarify the composition of understory herbaceous,diversity characteristics and influencing factors in different forest communities in Fanjingshan mountain,and provide scientific basis for biodiversity conservation,scientific management and health assessment of forest ecosystem.【Method】The 1530 m×30 m forest community permanent plots with elevation ranged from 634 to 2382 m were set up in Fanjingshan natural reserve located in Guizhou,China,and the understory herbaceous composition was investigated using typical quadrat method,the correlation between herbaceous diversity and elevation as well as stand density were analyzed by means of correlation analysis.Meanwhile,the changes ofα,βdiversity of understory herbaceous along elevation and stand density gradient were revealed,and the environmental factors impacting herbaceous diversity were discussed.【Result】1)There were 146 species of herbaceous vascular plants belonging to 97 genera and 50 families in 15 forest community permanent plots,among them,44 species,belonging to 20 genera and 10 families were pteridophyte,and 102 species,belonging to 77 genera,40 families were angiosperm.Dryopteridaceae,Athyriaceae,Asteraceae,Orchidaceae,Asparagaceae and Polypodiaceae were the dominant families,accounting for 38.36%of total species.Specie number and important value of herbaceous were variable in different communities,herbaceous specie number ranged from 2 to 40,plot 8 was the richest,while plot 14 was the least.The important value of herbaceous ranged from 0.31 to 58.21,and Pteridophyte were relatively high,while casual species and companion species were relatively low.2)The Margalef index(0.43-5.50),Simpson index(0.18-0.88),Shannon-Wiener index(0.33-2.59)and Pielou index(0.46-0.83)all did not demonstrate obvious change with the increase of elevation and stand density.The regression analysis showed that:except Pielou index,Margalef index,Simpson index and Shannon-Wiener index slight negatively correlated with elevation,whereas all diversity indices showed a low positive correlation with stand density.3)Jaccard index overall presented a downward trend with increasing elevation which indicated that the species turnover rate of different communities was gradually increased,however,Cody index showed an upward tendency with the increase of elevation.Jaccard index and Cody index fluctuated with the increase of stand density and did not appear significant change.【Conclusion】Both elevation and stand density had effects on understory herbaceous composition and diversity of forest communities in Fanjingshan mountain,but both of them did not strongly correlate with diversity indices,and did not play a decisive role in formation and maintenance of herbaceous diversity.