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Doctoral thesis, 2019

Emulating natural disturbances for the conservation of boreal forest birds

Versluijs, Martijn

Abstract

In the boreal biome, intensive forestry and fire suppression have led to the loss of natural disturbances regimes and changes in forest ecosystems at the landscape and local scale. A large proportion of the old-growth forests has been converted into even-aged single-species forests, with degraded understory layer and reduced availability of dead wood. This has resulted in the population decline of bird species that rely on structurally complex forest habitat. Restoring habitat structures by mimicking natural disturbance regimes can help to safeguard biodiversity. In this study I evaluated the effects of two ecological restoration measures – prescribed burning and gap cutting – on bird assemblage structure and breeding performance of the European pied flycatcher Ficedula hypoleuca in boreal forests. Additionally, I identified biodiversity indicators and tested how ecological restoration can affect their indicator value. Lastly, I characterized substrate preferences and foraging behavior as measured through foraging time of the Eurasian three-toed woodpecker Picoides tridactylus in forest stands subjected to prescribed burning and in unburned forests. Prescribed burning increased the abundance of long-distance migrants, ground breeders, strong cavity excavators and species preferring early-successional habitat. Furthermore, fire had positive effects on the body condition of nestlings of pied flycatchers, this suggest that local habitat quality improved. Gap cutting did not influence bird assemblage structures neither the reproductive output nor nestling body condition. The three-toed woodpecker and the Siberian jay Perisoreus infaustus were identified as potential biodiversity indicators among birds. However, after fire, the goldcrest Regulus regulus became the best predictor of high species richness. The main foraging substrate for three-toed woodpeckers can be characterized as freshly dead trees with a diameter breast height (DBH) of more than 15 cm. However, data on foraging behavior suggest that substrates in the 5-15 cm DBH range and living trees are important as well. The main conclusion from this study is that prescribed burning as a restoration treatment is an effective way to restore habitat for boreal forest birds in managed boreal forest landscapes. These results should encourage forest managers to reintroduce more fire in boreal forests as a complement to other conservation measures.

Keywords

Ecological restoration, prescribed burning, gap cutting, biodiversity indicators, breeding performance, foraging ecology

Published in

Acta Universitatis Agriculturae Sueciae
2019, number: 2019:13
ISBN: 978-91-7760-344-3, eISBN: 978-91-7760-345-0
Publisher: Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences

Authors' information

Versluijs, Martijn
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies

UKÄ Subject classification

Ecology
Forest Science

URI (permanent link to this page)

https://res.slu.se/id/publ/104075