生物邻体和生境异质性共同驱动乔木幼苗存活动态

Local biotic neighborhood and habitat heterogeneity drive tree seedling survival dynamics in a temperate forest

以长白山原始阔叶红松林样地为平台,样方中胸径小于1 cm的乔木幼苗为研究对象,基于2012-2014年连续3年的幼苗调查数据,利用广义线性混合模型分析影响群落乔木幼苗存活的生物邻体和生境异质性,探讨阔叶红松林幼苗存活影响因素及物种共存机制.结果显示:(1)生物邻体和生境异质性对幼苗存活都有显著影响,适宜大树生长的局域生境可能同样也适宜幼苗的存活,幼苗在林冠开阔度较高和土壤中含有较高有效氮、全磷和全钾的区域存活率较高.(2)幼苗个体之间存在明显的竞争,较多的幼苗邻体会显著降低幼苗的存活率.2年生幼苗存活分析中同种幼苗邻体与幼苗存活呈显著负相关,表明存在负密度制约效应.(3)随着存活年龄的增加,生境异质性对幼苗存活的影响逐渐增大.本研究验证了负密度制约效应和生境异质性对该温带森林乔木幼苗存活有着重要影响,各个因子的相对重要性随着种子传播方式、年龄级以及物种而发生变化,证明群落多样性维持和物种共存会随着个体发育过程的不同而变化.

This research aimed to understand the importance of biotic neighborhood and habitat heterogeneity for tree seedling survival in a broad-leaved Korean pine （Pinus koraiensis） mixed forest in the Changbai Mountain, northeastern China. We examined the relative effect of biotic neighborhood and habitat heterogeneity on seedling survival by using generalized mixed linear model over 3 years. Our study showed that both biotic neighborhood and habitat heterogeneity had significant effect on seedling survival at the community level, The local environment suitable for adult growth was also suitable for seedling survival. Higher canopy openness and soil available nitrogen had significant positive effect on seedling survival. On the other hand, seedling density had significant negative effect on seedling survival due to the individual competition. Particularly, we found significant negative density dependence effects on seedling survival which was caused by conspecific seedling neighbors. As expected, with the increase of seedling survival age, the habitat heterogeneity became more and more important to seedling survival. We conclude that both local biotic neighborhood and habitat heterogeneity drive seedling survival in this temperate forest, but their relative importance varies with the seedling age class and species traits,