The majority of global forest area is considered neither forest plantation nor formally protected. In these forests multiple-use prevails and forests have the potential to be managed sustainably while providing multiple ecosystem goods and services. However, in practice, management in these forest areas is usually intensive, often securing the provision of a single commodity: wood biomass. This management leads to forest simplification, disregarding forest multi-functionality, biodiversity conservation and ecosystem services provided by forest biodiversity.
In this thesis, I evaluate the effect of increasing forest functional heterogeneity on biodiversity and multiple ecosystem services in managed boreal forests. My research takes advantage from a large-scale, replicated ecological experiment initiated in Finland in 2000, where forest structure was manipulated following disturbance guided management, with several retention levels at harvesting in combination with prescribed fire in 24 study sites.
The results show that local scale heterogeneity mediated by fire and high retention improves lingonberry yield and performance in burnt harvested forests. Dead wood and post-fire soil structure from these forests are beneficial for bee abundance and diversity, through an increase in nesting resources. Early successional burned forests exhibit increased levels of parasitoid functional diversity driven by higher structural complexity of vegetation mediated by disturbance.
At a landscape scale, old-growth forests provide with abundant bilberry cover, spring flowering and berry yield, offering complementarity of flowering resources for pollinators nesting on post-harvest forests. Habitat diversity generated by old-growth forests, variable tree retention and fire intensity, promotes pollinator spatial and temporal turnover, especially in burned harvested forests, and large-scale parasitoid functional trait diversity.
In conclusion, emulation of forest disturbance at harvesting, together with the preservation of natural old-growth forests increase functional heterogeneity in managed boreal forests and hold promise for reconciling production forestry with sustainable forest management, provision of critical ecosystem services and biodiversity conservation.