Effects of neighborhood diversity on herbivory in early-stage forests in southern China.

Abstract

Herbivory plays important roles in forest ecosystems and is thought to be influenced by tree diversity. However, it is unclear whether, and if so how, tree diversity confers associational resistance or associational susceptibility to neighboring trees. In this study, our overall aim is to test whether biodiversity confers associational resistance or associational susceptibility to herbivores in tree species during the early stages of forest development. For this purpose, we examined whether tree species diversity affects herbivore damage in the early stages of forest development and what factors mediate the interaction between tree diversity and herbivory. We found that in some cases herbivory was related to species identity, e.g., Erythrophleum fordii was more susceptible to leaf chewers when surrounded by diverse neighbors. In other cases (i.e., Castanopsis carlesii and Elaeocarpus sylvestris), herbivory was positively associated with tree apparency. Additionally, we found that early-stage damage constrains growth in several species (e.g., C. carlesii and E. sylvestris), highlighting a previously underappreciated pathway through which diversity can shape long-term stand dynamics. Thus, herbivore damage in young subtropical plantations is not only governed by diversity but also by a three-way interplay between the identity of focal tree species, neighborhood diversity, and focal tree apparency, showing signs of associational susceptibility. Our finding that reduced tree apparency contributes to associational resistance in young trees can inform more effective forest management strategies.