古田山常绿阔叶林不同演替群落的萌生特征

萌生是植物营养繁殖的重要方式之一, 树木的萌生更新对群落结构的维持、植被的动态和演替具有重要意义。本研究基于古田山常绿阔叶林内处于不同演替阶段的25个30 m × 30 m样方中胸径 ≥ 5 cm的木本植物萌生茎发生情况的调查数据, 应用线性回归模型分析了不同演替群落的萌生特征及其地形解释。结果发现: (1)样地内共有56种木本植物存在萌生现象, 占总物种数的53.8%。(2)群落(样方)水平的萌生能力与海拔显著负相关, 与坡度和坡向的相关性较弱。(3)群落水平的萌生能力与林分年龄显著负相关; 在控制地形因子的影响下, 林分年龄对萌生指标解释量仍然达到20%-30%。萌生个体数和萌生物种丰富度所占比例随林分年龄显著下降, 萌生物种主茎的平均胸径随林分年龄显著增加。研究表明, 古田山常绿阔叶林萌生能力随林分年龄的增大而下降, 可能由演替序列上物种组成的变化(即萌生能力较强物种的多度下降)和群落结构的变化(即大径级个体增多)导致。另外, 萌生能力受到海拔、坡向等地形因素的影响。

Sprouting characteristics of communities during succession in an evergreen broad-leaved forest on Gutian Mountain,East China

Sprouting is an important vegetative reproduction strategy. Sprouting in woody plants is especially of great significance for maintaining forest structure and influencing vegetation dynamics and succession. In this study, we collected sprout data from 25 plots (30 m × 30 m) in an evergreen broad-leaved forest on Gutian Mountain, Zhejiang Province, East China for all trees with diameter at breast height (DBH) equal to or greater than 5 cm. Based on this data, we used general linear regression models to explore the characteristics and the effects of topographic factors and forest age on sprouting ability in forest communities during succession. We found that (1) 53.8% (56/104) of species in this forest showed evidence of sprouting. (2) The plot-level sprouting ability decreased significantly with elevation and marginally decreased significantly with aspect. (3) The plot-level sprouting ability decreased significantly with forest age. Forest age explained 20%-30% of the variation in sprouting ability after being fitted with the models using topographical factors. Both the number of sprouting genets and the proportion of sprouted species richness decreased significantly, while the mean DBH of sprouting genets increased significantly with forest age. This study shows that a decrease in community sprouting ability coupled with an increase in forest age may result from changes in both species composition (i.e. a decreasing number of individuals, but a higher sprouting ability) and structure (i.e. an increasing in proportion of larger individuals) during forest succession. In addition, the sprouting ability of forest communities is also affected by topographical factors, such as elevation and aspect.