Forest biodiversity monitoring: the example of bird survey in Finland and their responses to forest habitat at multiple scales | Suivi de la biodiversité forestière : l'example du suivi des oiseaux en Finlande and leurs réponses à l'habitat forestier à plusieurs échelles

International audience

English. Long-term biodiversity and forest habitat surveys are scarce and, therefore, precious to study the land management-biodiversity relationship. The response of biodiversity to habitat heterogeneity measured at a fine resolution and on a landscape scale, is not yet fully understood due to the lack of such habitat mapping on a global scale. In Finland, standardized national bird transects and forest structure data have been available since 2009. We explore how these data can be used to better understand the forest habitat-biodiversity relationship at various scales and indirectly inform about the effects of management practices. We mobilize 566 bird transects, multisource national forest inventory, and disturbance map to investigate the bird assemblage responses to landscape habitat heterogeneity (i.e., composition and configuration). We characterize landscapes based on land cover and forest habitat diversity (e.g., mean patch size, area of old and broadleaf forests, age class diversity, etc.). We also implement habitat functional heterogeneity indices such as richness, evenness, and the Rao’s Q index, based on vegetation structural features (i.e., tree canopy closure, mean tree diameter, age, height, vegetation type). We study bird assemblages through species compositions but also included functional traits and specialization indices. We hypothesize a positive response of taxonomic and functional biodiversity to both landscape compositional and configurational habitat heterogeneities. We expect to see a greater effect of compositional heterogeneity, particularly when studied through the functional prism of vegetation structure. We also expect that the amounts of old forests (i.e., ≥ 100 years) and broadleaf forests (i.e., ≥ 80 % of broadleaf tree volume) have a positive effect on forest bird species, since they are scarce in Finnish landscapes but associated with multiple key (micro-)habitats (e.g., deadwood, large old trees, tree-related microhabitats). In contrast, we expect mixed effects of disturbances: quadratic effect of the natural disturbance severity to the overall bird community, while amount of clear-cuts in landscape should have negative effects on forest bird species but could also represents opportunities for open-land species.