Drivers of arboreal lichen community structure and diversity on Abies balsamea and Betula alleghaniensis in the Avalon Forest Ecoregion, Newfoundland

Abstract

There is debate about what drives and maintains the structure of arboreal lichen communities and the relative importance of substrate vs. local environment. Here, we examined which lichen species are unique to two tree species [Abies balsamea (L.) Mill. and Betula alleghaniensis Britton] in the boreal forests of the Avalon Peninsula, Newfoundland, and which environmental variables are most important for lichen colonization and community structure. We collected data on lichen diversity from tree boles along with environmental data (tree size, bark pH, canopy cover) for each tree and each site. Multivariate analyses were used to determine the relationship between community structure and environmental data. The results show that a diverse range of tree characteristics are needed to support a diverse range of lichen species. Certain stands, such as old B. alleghaniensis stands, are more suitable to host a unique community of lichens than others. These results can inform land managers on the Avalon, recommending strategies for protected areas and providing forest harvest guidelines that limit clear-cutting of A. balsamea to maintain a diverse community structure and limit harvest of B. alleghaniensis trees in sites less optimal for lichen growth. These baseline data can also be used to monitor changes caused by moose browse and selective harvesting, two locally important threats to lichen diversity.