Winter browsing by moose (Alces alces) in a forested mountainous landscape of West-Central Sweden

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 vs. 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.