Bryophyte Conservation in Managed Boreal Landscapes: Fourteen-Year Impacts of Partial Cuts on Epixylic Bryophytes

Jeffrey Opoku-Nyame,Alain Leduc,Nicole J Fenton

doi:10.3389/ffgc.2021.674887

Abstract

Clear cut harvest simplifies and eliminates old growth forest structure, negatively impacting biodiversity. Partial cut harvest has been hypothesized (1) to have less impact on biodiversity than clear cut harvest, and (2) to encourage old growth forest structures. Long-term studies are required to test this hypothesis as most studies are conducted soon after harvest. Using epixylic bryophytes as indicators, this study addresses this knowledge gap. Fourteen years after harvest, we examined changes in epixylic bryophyte community composition richness and traits, and their microhabitats (coarse woody debris characteristics and microclimate) along an unharvested, partial cuts and clear cuts harvest treatment in 30 permanent plots established in the boreal black spruce (Picea mariana) forests of northwestern Quebec, Canada. Our results were compared to those of an initial post-harvest study (year 5) and to a chronosequence of old growth forests to examine species changes over time and the similarity of bryophyte communities in partial cut and old growth forests. Coarse woody debris (CWD) volume by decay class varied among harvest treatments with partial cuts and clear cuts recording lower volumes of early decay CWD. The epixylic community was richer in partial cuts than in mature unharvested forests and clear cuts. In addition, species richness and overall abundance doubled in partial and clear cuts between years 5 and 14. Species composition also differed among treatments between years 5 and 14. Furthermore, conditions in partial cut stands supported small, drought sensitive, and old growth confined species that are threatened by conditions in clear cut stands. Lastly, over time, species composition in partial cuts became more similar to old growth forests. Partial cuts reduced harvest impacts by continuing to provide favorable microhabitat conditions that support epixylic bryophytes. Also, partial cut harvest has the potential to encourage old growth species assemblages, which has been a major concern for biodiversity conservation in managed forest landscapes. Our findings support the promotion of partial cut harvest as an effective strategy to achieve species and habitat conservation goals.

Highlights

Over the past two decades, partial cut harvest has gained global research interest due to its proposed biodiversity benefits compared to clear cut harvest (Franklin et al, 1997; Lindenmayer et al, 2012)
Residual stands with variable retention of merchantable stems left after partial cut harvest are hypothesized to serve as refugia and enhance species recovery after harvest (Franklin, 1993; Drever et al, 2006)
This study examined the efficacy of partial cut harvest to maintain epixylic bryophytes 14 years after harvest

Summary

Introduction

Over the past two decades, partial cut harvest has gained global research interest due to its proposed biodiversity benefits compared to clear cut harvest (Franklin et al, 1997; Lindenmayer et al, 2012). Numerous short-term studies have demonstrated the ability of partial cuts to generate favorable habitat conditions that support many forest species (Vanderwel et al, 2007; Caners et al, 2013; Fenton et al, 2013; Baker et al, 2016). This has ignited a lot of interest in long-term studies to better understand species recovery after partial cut harvest (Baker et al, 2015; Fedrowitz et al, 2014), as longitudinal studies in permanent plots can provide strong evidence of species recovery (Dynesius, 2015). Except for a few short-term studies (Man et al, 2008; Boudreault et al, 2013; Bose et al, 2015), no long-term studies have assessed this

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