Haber Lisa T, Fahey Robert T, Wales Shea B, Correa Pascuas Nicolás, Currie William S, Hardiman Brady S, Gough Christopher M
Department of Biology Virginia Commonwealth University Richmond VA USA.
Department of Natural Resources and the Environment & Center for Environmental Sciences and Engineering University of Connecticut Storrs CT USA.
Ecol Evol. 2020 Apr 12;10(10):4419-4430. doi: 10.1002/ece3.6209. eCollection 2020 May.
Differential disturbance severity effects on forest vegetation structure, species diversity, and net primary production (NPP) have been long theorized and observed. Here, we examined these factors concurrently to explore the potential for a mechanistic pathway linking disturbance severity, changes in light environment, leaf functional response, and wood NPP in a temperate hardwood forest.Using a suite of measurements spanning an experimental gradient of tree mortality, we evaluated the direction and magnitude of change in vegetation structural and diversity indexes in relation to wood NPP. Informed by prior observations, we hypothesized that forest structural and species diversity changes and wood NPP would exhibit either a linear, unimodal, or threshold response in relation to disturbance severity. We expected increasing disturbance severity would progressively shift subcanopy light availability and leaf traits, thereby coupling structural and species diversity changes with primary production.Linear or unimodal changes in three of four vegetation structural indexes were observed across the gradient in disturbance severity. However, disturbance-related changes in vegetation structure were not consistently correlated with shifts in light environment, leaf traits, and wood NPP. Species diversity indexes did not change in response to rising disturbance severity.We conclude that, in our study system, the sensitivity of wood NPP to rising disturbance severity is generally tied to changing vegetation structure but not species diversity. Changes in vegetation structure are inconsistently coupled with light environment and leaf traits, resulting in mixed support for our hypothesized cascade linking disturbance severity to wood NPP.
长期以来，人们一直在理论上探讨并观察到干扰严重程度对森林植被结构、物种多样性和净初级生产力（NPP）的不同影响。在此，我们同时研究了这些因素，以探索在温带硬木森林中，连接干扰严重程度、光环境变化、叶片功能响应和木材NPP的潜在机制途径。通过一系列跨越树木死亡率实验梯度的测量，我们评估了与木材NPP相关的植被结构和多样性指数变化的方向和幅度。根据先前的观察结果，我们假设森林结构和物种多样性变化以及木材NPP相对于干扰严重程度将呈现线性、单峰或阈值响应。我们预计干扰严重程度的增加将逐渐改变林下光可用性和叶片性状，从而将结构和物种多样性变化与初级生产联系起来。在干扰严重程度梯度上，观察到四个植被结构指数中的三个呈现线性或单峰变化。然而，与干扰相关的植被结构变化与光环境、叶片性状和木材NPP的变化并不一致相关。物种多样性指数并未随着干扰严重程度的增加而变化。我们得出结论，在我们的研究系统中，木材NPP对干扰严重程度增加的敏感性通常与植被结构的变化有关，而与物种多样性无关。植被结构的变化与光环境和叶片性状的耦合不一致，导致对我们假设的将干扰严重程度与木材NPP联系起来的级联反应的支持不一。
