Forest biodiversity and ecosystem services from spruce-birch mixtures: The potential importance of tree spatial arrangement

• Published in: Environmental Challenges
• Main Authors: Adam Felton, Annika M. Felton, Hilde Karin Wam, Johanna Witzell, Märtha Wallgren, Magnus Löf, Johan Sonesson, Matts Lindbladh, Christer Björkman, Kristina Blennow, Michelle Cleary, Mats Jonsell, Maartje J. Klapwijk, Mats Niklasson, Lisa Petersson, Jonas Rönnberg, Åsa Ode Sang, Fredrika Wrethling, Per-Ola Hedwall
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2022
• Subjects: Biological diversity; Ecosystem services; Forestry; Mixed-forest stand; Tree plantations; Species conservation; Environmental sciences; GE1-350; Norway; Fennoscandian
• Online Access: https://doi.org/10.1016/j.envc.2021.100407; https://doaj.org/article/5df90b9d25c742d09c70c8f0d1f3d6a2

There is increasing empirical support for the biodiversity and ecosystem service (ES) benefits of mixed-species production forests. However, few studies control for the spatial arrangement of the trees within mixtures to determine the influence that clustering the tree species (patch scale mixtures), versus evenly dispersing them (intimate scale mixtures), may have for biodiversity and ES outcomes. To highlight the potential implications of altering tree spatial arrangement in mixtures, and the need to fill related knowledge gaps, here we provide a qualitative multi-disciplinary overview of ecological and socio-economic drivers with the potential to alter biodiversity, ecosystem services, and management-related outcomes from patch versus intimate scale mixtures. We focused our overview on even-aged mixtures of Norway spruce (Picea abies) and birch (Betula pendula or B. pubescens) in Sweden, which enabled us to contrast findings within a biogeographical and silvicultural setting. Specifically, we targeted implications for biodiversity (understory vascular plants, epiphytic lichens, saproxylic beetles, birds), biomass production, harvesting costs, management ease, recreation and aesthetics, cervid game, as well as abiotic and biotic risks (wind, fire, pathogens, pests, browsing damage). In the absence of direct empirical evidence, we primarily relied on expert inference from theory and relevant empirical studies sourced from the Fennoscandian region, and further afield if needed. Collectively these efforts allowed us to develop a number of informed hypotheses indicating that for spruce-birch mixtures in this region, patch scale mixtures may have the potential to favour the diversity of several forest dependant taxonomic groups, cervid game and reduce harvesting costs, whereas intimate mixtures may have the potential to reduce pathogen and pest damage, and likewise, potentially benefit production outcomes. Current knowledge was too limited, inconsistent or context dependant to even tentatively infer outcomes for ...