Disturbance‐mediated heterogeneity drives pollinator diversity in boreal managed forest ecosystems

Abstract

Intensive forest management, together with fire suppression, have decreased structural complexity and altered dynamics of boreal forests profoundly. Such management threatens forest biodiversity and can reduce the provision of ecosystem services. Although the importance of ecosystem services is widely acknowledged, conservation strategies are hindered by poor knowledge about diversity patterns of service provider species as well as on mechanisms affecting these assemblages at different spatial and temporal scales. In this study, we assessed the effect of disturbance management on forest pollinator communities. To do so, we used a large-scale ecological experiment conducted in the year 2000, where forest complexity was manipulated with different harvest regimes and prescribed fire. Results were consistent with a positive response of pollinators to increasing habitat heterogeneity driven by past disturbances. Harvested sites harbored a diverse pollinator community, and showed higher spatial and temporal turnover in species richness. Conversely, old-growth forest communities were a nested subset of harvested sites and contained half of their total diversity. Variation in community composition (β diversity) was primarily affected by species temporal turnover. Throughout the season, β diversity was controlled by fire and harvesting legacies, which provide environmental heterogeneity in the form of flowering and nesting resources over space and time. Conservation strategies may undervalue ecosystem services in dynamic, naturally disturbance-driven, landscapes when relying solely on undisturbed forests areas. However, maintaining natural dynamics in early successional forests, by emulating natural disturbances at harvesting, hold promise for the conservation of both biodiversity and ecosystem services in boreal forests.

Trade‐offs in berry production and biodiversity under prescribed burning and retention regimes in boreal forests

“…Moreover, our results support earlier studies that the conservational value of prescribed burning can be higher if performed in combination with retention forestry or in unlogged forests (e.g. Halme et al., ; Heikkala, Suominen, Junninen, Hämäläinen, & Kouki, ; Heikkala et al., ; Hyvärinen et al.,; Rodríguez & Kouki, ). However, the multifunctional benefits from prescribed burning can, with respect to these aspects, vary highly depending on species groups included, and positive effects that are valid for all measured variables cannot be warranted.…”

“…Moreover, our results support earlier studies that the conservational value of prescribed burning can be higher if performed in combination with retention forestry or in unlogged forests (e.g. Halme et al, 2013;Heikkala, Suominen, Junninen, Hämäläinen, & Kouki, 2014;Heikkala et al, 2016;Hyvärinen et al,2006;Rodríguez & Kouki, 2017 Grandpré, Gagnon, & Bergeron, 1993). Additionally, species richness as such is only one biodiversity target in managed multifunctional forests.…”

“…Fedrowitz et al., ; Halpern, Halaj, Evans, & Dovčiak, ; Johnson, Strengbom, & Kouki, ). Only a few studies have examined effects related to ecosystem services (Lazaruk, Kernaghan, Macdonald, & Khasa, ; Rodríguez & Kouki, , ), and to our knowledge, there are no previous studies examining the effects on NTFPs, or studies that have explored synergies and trade‐offs among the different values that these conservation measures are expected to deliver.…”

Wild bee diversity increases with local fire severity in a fire‐prone landscape

“…, Rubene et al. , Rodríguez and Kouki ). However, the landscape heterogeneity created by natural disturbances like wildfire is important for supporting pollinator diversity in space and time (Ponisio et al.…”

“…, Rubene et al. , Rodríguez and Kouki ) or have focused on small fires (Potts et al. , Bogusch et al.…”