Open access publications in the SLU publication database

Abstract

This thesis presents data on factors determining the occurrence and dynamics of hazel grouse populations at several spatial scales in five landscapes with different management regimes.
In a forested area with a low degree of habitat variation, the relationship between occurrence of hazel grouse and type of habitat was best explained at scales equal or larger than the home range, compared to smaller spatial scales. At this spatial scale the hazel grouse preferred spruce stands 20-69 years old and those older than 90 years, having 5-40% deciduous trees. More specifically the presence of hazel grouse in a habitat patch was positively influenced by a high amount of vertical ground cover, a rich field layer vegetation and the presence of alder.
At the landscape scale the occurrence of hazel grouse in habitat patches in intensively managed landscapes was negatively affected by increasing distance between suitable habitats both in an agriculture-dominated landscape and in a forestdominated landscape. The threshold distances for hazel grouse movements were about 200 m in the agricultural landscape and about 10 times longer in the forested landscape, suggesting a strong effect of different types of matrix. The dynamics of hazel grouse occurrence in habitat patches in the intensively managed forested landscape, were determined by distance to nearest suitable habitat patch, amount of cover in the habitat patch and habitat patch size. In a fine-grained less intensively managed landscape, using a 21-year long data set, habitat size and isolation were also found to strongly affect the presence of hazel grouse. Hazel grouse occupancy increased considerably in habitat patches larger than 10 ha. However, the effect of isolation occurred at a smaller spatial scale and was not induced by distance, instead it occurred as an avoidance of open land surrounding the habitat patch.
A high concordance, about 85%, between predicted and observed occurrence of hazel grouse was found when the models developed in the two differently managed forested areas were used on independent data from a third landscape.
The results presented in this thesis suggest that the hazel grouse is a poor disperser, avoids open areas, and has very specific habitat requirements, many of which conflict with production of coniferous pulp and timber. Theoretical aspects of landscape ecology and specific guidelines, including applicable measurements and evaluations of forest descriptions for maintaining the species in managed boreal landscapes, are discussed.