Meta‐analysis of management effects on biodiversity in plantation and secondary forests of Japan

Abstract

Conservation of temperate forest biodiversity has historically focused on natural oldgrowth. Less than 3% of the world's temperate forests remain unmodified by humans, however, and much of temperate-forest biodiversity is held in the predominating planted and secondary forests. Japan provides a widely applicable model for examining how to maximize biodiversity in managed temperate forests, because of its richness of forestry research generated from its vast forest area, albeit largely in Japanese, and the wide practice of its dominant management interventions across the northern temperate zone. Management for plantations includes thinning, extended rotation cycles and clear-cutting. For secondary forests regenerating from past clearance, traditional management varies in its intensities, from clear-cutting as coppices to small-scale understory clearance. Here we provide a first synthesis of published research on biodiversity in planted and secondary forests of Japan, relevant to management of these types of forest in northern temperate regions. Systematic review and meta-analyses of papers published in English and Japanese quantified management impacts on species richness and abundance of several taxa, in relation to moderator variables including stand age and management intensity. Plantation thinning substantially increases the richness and abundance of several taxa. Effect sizes decline with time since thinning for the abundance of regenerating saplings and seedlings, necessitating repeated thinning treatments every 6 years to sustain this positive effect. Taxonomic groups exhibit variable relationships with stand age in both planted and secondary forests, indicating a need to include both young and old forest stands in managed forest mosaics. We find an insufficient evidence base is available to allow for a meaningful synthesis of low-intensity management effects in historically managed secondary forests, with studies varying widely in scale and reported outcomes. We outline an agenda for the research community to achieve a systematic evaluation of scale-dependent effects of traditional forest management on biodiversity.

Ignoring non‐English‐language studies may bias ecological meta‐analyses

“…(2013), and Spake et al. (2019). Koshida and Katayama (2018) included 64 effect‐size estimates from 35 studies on the effects of rice‐field abandonment on biodiversity.…”

“…Data provided by Spake et al. (2019) included effect sizes representing forestry impacts on the species richness and abundance of three population groups: ground‐layer plants; saplings and seedlings; and invertebrates. Sufficient numbers of both English‐ and Japanese‐language studies were available for meta‐analyses of thinning impacts on the abundance of ground‐layer plants, and saplings and seedlings.…”

“…From Spake et al. (2019), we used 65 effect‐size estimates: 41 from six English‐language studies and 24 from three Japanese‐language studies on the effect of thinning on abundance of ground‐layer plants (“plant forestry meta‐analysis” from hereon; Table 1 and Appendix ), and 41 effect‐size estimates: 26 from six English‐language studies and 15 from four Japanese‐language studies on the effect of thinning on abundance of saplings and seedlings (“sapling forestry meta‐analysis” from hereon; Table 1 and Appendix ).…”

“… The two meta‐analyses in Spake et al. (2019) used some studies in common, and thus, the total number of studies does not equate to the sum of studies used in each meta‐analysis. Meta‐analysis article: a published article (paper) that conducted at least one relevant meta‐analysis.…”

Regional variability in landscape effects on forest bird communities

“…The nation of Japan provides a unique opportunity to test for regional variation in avian community responses to local landscape pattern (Yamaura et al 2011;Spake et al 2019b). Around two thirds of Japan is forested, with varying degrees of landscape pattern from forest to agricultural and urban land uses, leading to high variability in landscape-level forest cover, and consequently varying degrees of the diversity of different land cover types.…”