宝天曼国家级自然保护区落叶阔叶林密度制约效应对树木存活的影响

密度制约对物种共存起着重要作用。随着密度制约效应研究的深入, 亲缘关系较近的物种间表现出的密度制约效应逐渐被人们认识。本研究基于2009和2014年对宝天曼1 ha落叶阔叶林样地的2次调查数据, 利用广义线性混合模型分析了重要值排名前11位的物种不同邻域尺度的密度制约效应对不同径级(小径级(1 cm ≤ DBH < 5 cm)、中径级(5 cm ≤ DBH < 10 cm)、大径级(DBH ≥ 10 cm))目标个体存活的影响。研究表明: (1) 5年间样地中DBH ≥ 1 cm的所有个体的年均死亡率和增员率分别为5.85%和0.27%; (2)有5个物种的个体存活率与同种邻体个体数及同种邻体胸高断面积显著负相关; (3)小径级个体的存活在5 m的邻域范围内受同种密度制约和谱系密度制约的影响都很显著; 中径级个体在3个尺度上受到的密度制约和谱系密度制约的影响都不大; 大径级个体在7.5 m、10 m邻域范围内受谱系密度制约影响显著。结果表明, 同种密度制约和谱系密度制约效应对宝天曼落叶阔叶林不同生长阶段的树木个体影响不同。

Detecting density dependence on tree survival in a deciduous broad- leaved forest in Baotianman National Nature Reserve

It has been found that density dependence plays a crucial role in determination of species distribution and coexistence, and the effect of negative density dependence also plays an important part among phylogenetically related species. Based on two census datasets in 2009 and 2014 of the 1-ha deciduous broad- leaved forest plot in Baotianman National Nature Reserve, generalized linear mixed models (GLMMs) were used to examine the density dependence on individual survival of the top 11 species (with high important value) at different neighborhood scales and different DBH sizes (1 cm ≤ DBH< 5 cm, 5 cm ≤ DBH < 10 cm, DBH ≥ 10 cm). The results showed that (1) mean annual mortality and recruitment rate of individuals (DBH ≥ 1 cm) were 5.85% and 0.27%, respectively; (2) survival rate of 5 tree species was negatively correlated with abundance or neighbor conspecific basal area; (3) density dependence and phylogenetic diversity exerted significant effects on survival of small individuals (at 5 m neighborhood scale), whereas no significant influence on medium trees. With increasing tree size, phylogenetic diversity exerted important effect on large individuals at 7.5 m and 10 m neighborhood scales. In conclusion, density dependence and phylogenetic diversity play different roles on tree survival at different life stages and neighborhood scales in the deciduous broad-leaved forest in Baotianman National Nature Reserve.