湖北神农架山地米心水青冈-多脉青冈混交林的群落动态

Community dynamics of a montane Fagus engleriana-Cyclobalanopsis multiervis mixed forest in Shennongjia,Hubei,China

常绿落叶阔叶混交林是我国北亚热带的地带性植被类型,在神农架山地其优势类型为水青冈-青冈混交林。本研究基于对120m×80m的永久样地的2001、2006、2010年3次调查数据,从物种组成、数量特征、群落结构等方面分析了神农架山地米心水青冈-多脉青冈(Fagus engleriana-Cyclobalanopsis multiervis)混交林群落的动态特征。结果表明:群落的物种组成变化不大,在2001年、2006年和2010年分别为81、84和83种;优势成分以多脉青冈、米心水青冈、粉白杜鹃(Rhododendron hypoglaucum)和灰柯(Lithocarpus henryi)为主,但常绿树种重要值有增加的趋势;树木生长速率有加快的趋势;常绿树种的动态性强于落叶树种。树木数量、胸高断面积均呈现出先增加后减少的趋势;群落的整体结构未发生较大的变化,死亡个体的结构变化较为明显。从群落9年内的物种组成和结构变化来看,虽然在两次调查间隔期间树木的死亡和增补格局发生变化,雪灾对该群落可能产生了一定的影响,但该群落的物种组成和结构总体格局未发生较大变化,处于一种动态平衡,对外界干扰有较强的抵抗力。

Montane evergreen and deciduous broad-leaved mixed forests are some of the main vegetation types in China. Specifically, the Fagus-Cyclobalanopsis mixed forest is a dominant forest community in the mountainous region of Shennongjia. Using three datasets （2001, 2006, and 2010） from a permanent 120 m× 80 m plot in the montane evergreen and deciduous broad-leaved mixed forest in Shengnongjia, we analyzed the dynamics of tree species composition and community structure for individual trees （DBH ≥ 4 cm）. We found that total species number increased from 81 in 2001 to 84 in 2006, and then decreased to 83 in 2010. Dominant species remained constant throughout the study period, including Cyclobalanopsis multiervis, Fagus engleriana, Rhododendron hypoglaucum and Lithocarpus henryi. Stem number and basal area followed the same trend with an initial increase, followed by a decline. The mortality and recruitment of this survey plot changed substantially over the nine-year study period. Although an ice storm in 2008 had some impact on the community, the species richness and community structure did not alter significantly and the community appeared to be in a state of dynamic equilibrium with strong resilience to external disturbances.