Winter browsing by moose (Alces alces) in a forested mountainous landscape of west–central Sweden

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Abstract
Browsing ecology involving ungulates and their food resource is complex as consumption may reflect responses to various factors, such as quantity and quality of browse species. This study investigated winter browsing by moose Alces alces in a mountainous landscape of west–central Sweden, characterized by Norway spruce Picea abies production forests with high inclusion of deciduous species. Field data on tree species abundances as well as fresh and previous browsing were collected along moose tracks and control transects, to answer our questions regarding browse selection in relation to availability. The data were analyzed using mainly modelling (generalized linear mixed models) approaches. The results revealed greater amounts of available food trees (< 5 m) in young compared to older forests and along moose tracks compared to control transects. Downy birch Betula pubescens was the most abundant independent of forest age class and transect type (i.e. tracks versus controls). Quantitatively, the key winter browse in the study area was a mix of deciduous species, primarily downy birch and willows (Salix spp.) complemented by Eurasian aspen Populus tremula and grey alder Alnus incana. In young forest, aspen, rowan Sorbus aucuparia and willows were the most selected species, while common juniper Juniperus communis was the least selected. In older forest, alder was most selected, followed by willows and rowan, while aspen and downy birch were the least selected, except for spruce and lodgepole pine Pinus contorta. According to Jacobs selectivity index, downy birch, was underused while aspen, rowan and willows were overused in relation to their frequencies. The latter are often limited in today's cultivated forest landscape and thus an increased amount of those species may be utilized to a higher degree by moose than an increase of downy birch. No effect from snow depth was detected and browsing on dwarf shrubs was not observed.

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