Associations between canopy openness, butterfly resources, butterfly richness and abundance along forest trails in planted and natural forests

Atsushi Ohwaki,Saki Maeda,Masahiko Kitahara,Takashi Nakano

doi:10.14411/eje.2017.068

Abstract

Increasing the biodiversity in plantations of trees is an important issue because plantations have replaced many natural and semi-natural ecosystems worldwide. Therefore, identifying appropriate management techniques and key factors for enhancing biodiversity in plantations is required. We surveyed butterfly assemblages along forest trails in both plantations and natural forests and measured various environmental variables, including canopy, sub canopy and shrub stem densities, percentage of deciduous trees, flower plant richness, host plant richness, canopy openness and distance to forest edge. We hypothesized that (1) flower and host plant richness increase with an increase in the percentage of deciduous trees and canopy openness; (2) butterfly richness and abundance increase with an increase in forest structural complexity, butterfly resources, canopy openness and distance to forest edge; (3) the responses of plants and butterflies to canopy openness differ in plantations and natural forests; and (4) in plantations, tree-feeding butterflies respond to canopy openness less strongly than herbaceous plant feeding butterflies do because of the low diversity of trees in plantations. Our results generally support these hypotheses. Butterfly resources and butterfly richness and abundance all increase with increasing canopy openness; however, the increases were usually more dramatic in natural forests than in plantations and other factors are less important. In plantations, herbaceous plant feeding butterflies responded to increasing canopy openness more strongly than tree-feeding butterflies. The results of the present study indicate the importance of sunlit forest trails in enhancing butterfly resources, butterfly richness and abundance in plantations. Because at the stand-level management is labour- and cost-intensive, labour- and cost-saving trail management options need to be explored further in terms their effectiveness in increasing biodiversity in plantations.

Highlights

The increase in biodiversity in plantations of trees is an important issue because plantations have replaced many natural and semi-natural forests and grasslands worldwide and the area covered by these plantations continues to increase (Brockerhoff et al, 2008; Payn et al, 2015)
We examined the effects of conversion of natural forests into coniferous plantations, canopy openness and various forest characteristics on butterfly resources and butterfly assemblages and whether the responses of plants and butterflies to canopy openness differ between plantations and natural forests
The relationships between the percentage of deciduous trees and flower abundance, total butterfly abundance and herbaceous plant feeding butterfly richness and abundance may indicate the positive effects of improving light conditions in forests

Summary

Introduction

The increase in biodiversity in plantations of trees is an important issue because plantations have replaced many natural and semi-natural forests and grasslands worldwide and the area covered by these plantations continues to increase (Brockerhoff et al, 2008; Payn et al, 2015). Because the conversion of natural forests into plantations has a great effect on the native fauna and flora (plants: Barlow et al, 2007a; Bremer & Farley, 2008; vertebrates: Barlow et al, 2007a; du Bus de Warnaffe & Deconchat, 2008; Yamaura et al, 2009; insects: Robertson et al, 1995; Magura et al, 2000; Barlow et al, 2007a, b; reviewed in Lindenmayer & Hobbs, 2004; Brockerhoff et al, 2008), identification of the appropriate management techniques and key factors that enhance biodiversity within plantations is required This is important in countries where plantations occupy a large percentage of the forest area or where the area under plantations is rapidly increasing. The diversity of longicorn beetles (Cerambycidae) is lower in plantations than in natural forests, and positively correlated with tree diversity, forest matureness and light conditions

Methods

Results

Conclusion