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.
Driftwood is woody debris that is floating on the sea or brought onto the shore by the sea. It can have a natural origin but often it originates from human activities. Driftwood has a significant ecological role as a microhabitat for a large range of species. Dead‐wood‐associated aphyllophoroid fungi on driftwood have been studied rather little globally, and there are hardly any studies conducted in the Baltic Sea. We studied the diversity and ecology of polypores and corticioids growing on driftwood (man‐made logs) on the shores of the Finnish SW‐archipelago. In total, 394 driftwood logs were surveyed for visible fungal sporocarps. We found altogether 145 species (1023 records) of which approximately three‐fourths were corticioids. The driftwood logs hosted several rare and noteworthy species, such as one new corticioid species, 16 nationally rare species, and 40 new species to the region. The five most common species accounted for one‐third of all observations, whereas 82 species (11% of all records) were recorded only once or twice. Larger logs hosted, on average, more species compared to small‐diameter logs. The mean number of species increased significantly when comparing the logs in the first and the middle stages of decay. Our results show that driftwood logs can host a wide variety of species and they provide an important substrate for many dead‐wood‐associated fungi, including species of conservation concern and species with restricted ecological requirements. Driftwood hosted several species that have not been previously found in the archipelago forests, and the logs clearly enrich the fungal diversity in the area. Our results encourage to increase dead wood for fungi in coastal forests where it has been dramatically decreased as a result of strong hemeroby.
Because many currently protected forests are former timber production areas, restoration activities are often used to re-establish their natural structures. In this experimental study, we monitored the establishment of tree seedlings in previously managed but currently protected Scots pine (Pinus sylvestris L.) dominated stands in boreal forests 5 years after restoration measures. The study included eight study areas (115 sample plots) in southern Finland. We compared seedling abundance between five study groups: untreated control forest, unburned canopy gap, burned full-canopy forest, burned canopy gap, and thinned and burned forest. Density of tree seedlings was highest in burned canopy gaps (mean 25.4 seedlings/100 m 2 compared with 6.0 seedlings/100 m 2 in control sites). In particular, birch (Betula spp.) and Scots pine were significantly more abundant within burned canopy gaps than in unburned gaps. We conclude that opening within-stand canopy gaps, especially in combination with prescribed burning, can be useful in forest restoration as the gaps diversify age-class structure and tree species composition of single-cohort pine stands.
Résumé :Puisque plusieurs forêts actuellement protégées sont d'anciennes aires de production ligneuse, des activités de restauration sont souvent utilisées pour rétablir leur structure naturelle. Dans cette étude expérimentale, nous avons suivi l'établissement de semis d'arbres dans des peuplements de la forêt boréale dominés par le pin sylvestre (Pinus sylvestris L.), précédemment aménagés mais maintenant protégés, cinq ans après l'application de mesures de protection. L'expérience comportait huit aires d'étude (115 placettes échantillons) situées dans le sud de la Finlande. Nous avons comparé l'abondance des semis parmi cinq groupes d'étude : forêt témoin non traitée, trouée non brûlée, forêt avec un couvert fermé brûlée, trouée brûlée et forêt éclaircie et brûlée. La plus forte densité de semis d'arbres a été observée dans les trouées brûlées (moyenne de 25,4 semis/100 m 2 comparativement à 6,0 semis/100 m 2 dans le groupe témoin). En particulier, le bouleau et le pin sylvestre étaient significativement plus abondants dans les trouées brûlées comparativement aux trouées non brûlées. Nous concluons que les ouvertures du couvert d'un peuplement, surtout si elles sont combinées à un brûlage dirigé, peuvent être utiles à la restauration forestière parce que les trouées diversifient la structure des classes d'âge et la composition arborescente des pinèdes constituées d'une seule cohorte d'arbres. [Traduit par la Rédaction] Mots-clés : brûlage dirigé, régénération forestière, utilisation du feu pour restaurer la forêt, pin sylvestre.
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