Traits mediate a tradeoff in seedling growth response to light and conspecific density in a diverse subtropical forest

Understanding tree species responses to biotic and abiotic factors is fundamental for stronger predictions of community assembly and dynamics. However, several challenges remain. These include a failure to investigate whether there is evidence for key hypothesized life-history tradeoffs and to link these tradeoffs to functional traits.

In this study, we seek to explicitly address the above outstanding challenges by constructing models for individual seedling growth in response to abiotic and biotic factors using three years of seedling census data from a 20-ha subtropical forest dynamics plot in a diverse subtropical forest and correlated these responses with functional traits.

We found that light and conspecific neighbours increase and decrease the relative growth rate of tree seedlings, respectively. We also found that the ability of a species to positively respond to canopy openness trades off against susceptibility to CNDD. This tradeoff was evident across seasons and could be...

解析树木物种对生物（biotic）与非生物（abiotic）因子的响应规律，是精准预测群落组装与动态的核心基础。然而当前仍存在诸多挑战：一是尚未探明关键假说所提出的生活史权衡（life-history tradeoffs）是否存在实证依据，二是未能将此类权衡与功能性状（functional traits）建立关联。
本研究依托物种多样的亚热带森林中一处20公顷的亚热带森林动态监测样地（subtropical forest dynamics plot）的三年幼苗普查数据（seedling census data），构建幼苗个体针对生物与非生物因子的生长响应模型，并将上述响应与功能性状进行关联分析，以此明确解决前述突出挑战。
研究结果表明，光照与同种邻株（conspecific neighbours）分别会提升与降低树木幼苗的相对生长速率（relative growth rate）。此外还发现，物种对林冠开度（canopy openness）产生正向响应的能力，与其对CNDD的易感性之间存在权衡关系；该权衡在不同季节均表现显著，且可进一步……