Negative density dependence regulates two tree species at later life stage in a temperate forest.

Tiefeng Piao,Kwangil Cheon,Jung Hwa Chun,Hee Moon Yang

doi:10.1371/journal.pone.0103344

Abstract

Numerous studies have demonstrated that tree survival is influenced by negative density dependence (NDD) and differences among species in shade tolerance could enhance coexistence via resource partitioning, but it is still unclear how NDD affects tree species with different shade-tolerance guilds at later life stages. In this study, we analyzed the spatial patterns for trees with dbh (diameter at breast height) ≥2 cm using the pair-correlation g(r) function to test for NDD in a temperate forest in South Korea after removing the effects of habitat heterogeneity. The analyses were implemented for the most abundant shade-tolerant (Chamaecyparis obtusa) and shade-intolerant (Quercus serrata) species. We found NDD existed for both species at later life stages. We also found Quercus serrata experienced greater NDD compared with Chamaecyparis obtusa. This study indicates that NDD regulates the two abundant tree species at later life stages and it is important to consider variation in species' shade tolerance in NDD study.

Highlights

Tree populations are often thought to be regulated by negative density dependence (NDD) that can occur during several life stages, because higher conspecific density can impair performance due to stronger intraspecific competition for resources, more susceptibility to pathogens and easier detection by herbivores [1]
The above predictions can be obscured by habitat heterogeneity [33], because the performance of individuals can be greatly influenced by the availability of environmental resources [38,39,40], and the functional traits that are involved in plant-enemy interactions might be altered by abiotic and biotic factors [41]
For Chamaecyparis obtusa (CHOB), significant deviations were found at the scale of 0– 3, 4–4.5, 5.5–6.5, 8.5, 14–16.5, 17.5–19.5 m (Fig. 2a); for Quercus serrata (QUSE), significant deviations were found at all test scales (Fig. 2b)

Summary

Introduction

Tree populations are often thought to be regulated by negative density dependence (NDD) that can occur during several life stages, because higher conspecific density can impair performance due to stronger intraspecific competition for resources, more susceptibility to pathogens and easier detection by herbivores [1]. For established trees that have lower mortality rates, long time-scales observation is required to analyze mortality pattern because NDD may not be strong enough to induce immediate mortality, but instead cause limited growth over short time-scales [24] This may explain why few studies have been implemented to test NDD on trees at later life stages [4,26,27,28,29]. The above predictions can be obscured by habitat heterogeneity [33], because the performance of individuals can be greatly influenced by the availability of environmental resources [38,39,40], and the functional traits that are involved in plant-enemy interactions might be altered by abiotic and biotic factors [41] This change in performance with environment can affect a population’s susceptibility to herbivory to better link NDD with habitat heterogeneity [18]. By utilizing the spatial pattern of adult trees (dbh$10 cm), they factored out large-scale habitat heterogeneity and were able to detect NDD in western hemlock populations

Objectives

Methods

Results

Conclusion