Evaluation of strategies for conserving biodiversity in temperate and boreal forests

Halting biodiversity loss and the associated decline of ecosystem functioning is one of the greatest challenges faced by mankind. The globally adopted Aichi Biodiversity Targets for 2011-2020, issuing from the 10th Conference of the Parties of the Convention on Biological Diversity, represent the strongest global commitment to this challenge. For forest ecosystems, biodiversity decline can be halted only with i) sustainable management of multifunctional production forests (Target 7), ii) formation of well-connected systems of protected areas (Target 11), and iii) forest restoration (Target 15). Reaching these targets for the world’s forests requires a sound empirical understanding of the functioning and the relative importance of forests under different management regimes. Indeed, environmental policy should be informed by robust scientific evidence. This thesis addresses knowledge gaps that exist in the evidence-base for sustainable forest management and conservation in temperate and boreal forests. Chapter 2 quantifies the recovery rates of different functional groups of beetles, lichens and fungi to forest restoration measures in temperate and boreal regions across the world. A systematic review and meta-analysis identifies functional-group-specific relationships in the response of species richness to stand age after forest disturbance, with some groups requiring around a century of stand continuity for recovery to old-growth levels. The slow recovery of these functional groups makes old-growth forest an effectively irreplaceable biodiversity resource that should be exempted from restoration offset initiatives. Chapter 3 compares the biodiversity value of overmature even-aged planted and old-growth forest stands for ectomycorrhizal fungi in the New Forest National Park, UK. Overmature plantations are those beyond economic maturity, acquiring some of the structural characteristics of old-growth forests and there is increasing interest in their setting aside as a means of preserving species associated with old-growth forests. Analysis of 3 years of field data shows that setting aside of overmature planted forest is an effective means of conserving ectomycorrhizal communities associated with old-growth forests, given temporal continuity in the order of a century. This holds out particular promise for historically deforested regions such as the UK, where little old-growth forest remains and much planted forest exceeds a century in age. Chapter 4 investigates the relative importance of abiotic and biotic drivers of carabid functional trait diversity and composition for coniferous production forests across the UK. Analysis of the dataset of the UK Forestry Commission’s Biodiversity Assessment Project (BAP 1995-1999) contradicts previous studies in showing that ground vegetation diversity is not an important determinant of carabid functional diversity. This result suggests that restoration of plant communities, a major goal of forest restoration efforts, will not necessarily enhance carabid diversity in coniferous plantations. Canopy cover was the most important variable, tending to drive down carabid diversity. Chapter 5 collates an evidence base that will inform forest biodiversity conservation and policy-making in Japan. Four management interventions, outlined in Japan’s National Biodiversity Strategy, are assessed by systematic review and meta-analysis for their impacts on species richness, abundance and composition. The work provides general guidance for forest biodiversity conservation in Japan, and it highlights a major knowledge gap in a widely used contemporary intervention known as ‘satoyama’.