Ecological effects of disturbance-based restoration in boreal forests

Abstract

The degradation and disappearance of natural ecosystems and habitats -including forestsis one of the most important factors behind the current global decline in biological diversity. Since most of terrestrial biodiversity is found in forests, restoration of these ecosystems or their natural characteristics has been proposed as one of the main strategies to counteract global species loss.In this thesis, I examined the ecological effects of forest restoration in disturbancedriven boreal conditions. The applied restoration methods (prescribed burning; creation of canopy gaps; dead wood restoration) used natural forest disturbances as the reference point. Specifically, I focused on the effects that restoration has on tree species composition, ageclass structure, and the amount and diversity of dead wood in forest ecosystems. In addition to examining the changes in these structural attributes, I investigated dead-wood-associated fungal communities in the restored substrates, and assessed whether dead wood restoration could be used to conserve rare and threatened fungal species.Of the examined restoration treatments, the combination of prescribed burning and the creation of canopy gaps was found to be the most promising measure for the restoration of age-class structure and tree species composition in pine-dominated forests. Dead wood restoration -by artificially creating standing and fallen large-diameter dead trees -clearly enhanced the amount of dead wood in both pine and spruce dominated forests. Although dead wood restoration increased the abundance of fungal species in the examined forests, all aspects of the qualitative variation in dead wood was found to be difficult to restore in the short-term, since the restored dead wood was mainly in the initial stage of decomposition. The use of various restoration treatments (e.g. the creation of both standing and fallen dead wood) can compensate for some of the missing variation in fungal communities in the restored substrates.Based on my results, disturbance-based restoration produces promising results by the rapid re-introduction of some of the most important structural attributes that have been lost from forests previously managed for timber production. Although the findings in this thesis show the clear positive effects that restoration has on the re-creation of naturally occurring forest characteristics, it appears difficult to restore all the inherent variability of natural forests. A particular challenge originates from the extended time scale of the natural processes, which have created and maintained the full array of ecological structures in forests, including the generally slow processes of stand succession and wood decomposition. To build a more comprehensive understanding of the potential of forest restoration for the conservation of endangered forest-associated species, a substantially longer monitoring period of restored forests would be useful in future studies.

Dynamics of biodiversity-rich deciduous trees and microhabitats in boreal forests

“…To better resemble natural disturbances and increase species richness and the number of threatened species in managed forests, suggestions are often made to base forest management on natural ecosystem dynamics (Attiwill 1994;Kuuluvainen 2009). In practice, this is widely applied by leaving retention trees during clearcutting operations (Gustafsson et al 2010), as well as by carrying out various cutting methods within the managed landscape and the creation of high stumps (Pasanen 2017;Pasanen et al 2019). Another practice is to apply prescribed burning, which has proven to be highly effective for nature conservation (e.g.…”

Impacts of fire in active and passive restorations on boreal forest soils and vegetation

“…Boreal forests are naturally disturbance-driven ecosystems. Consequently, the disturbance ecology of boreal forests could provide an excellent template or model for planning and studying restoration activities (Pasanen 2017). Understanding the inherent disturbance dynamics of the boreal forest biome is also a prerequisite for its management as a complex adaptive system facing global directional change, such as increases in temperature (Gauthier et al 2015).…”