Epsilon Open Archive

Abstract

Large herbivores are important drivers of ecosystem processes, affecting plant species richness and composition, primary productivity, habitat structure as well as nutrient cycling. Large herbivore activities may therefore have important indirect effects on other plants and animals in the same ecosystem. The effect of herbivore activity on ecosystem processes varies with habitat productivity, herbivore selectivity, herbivore density and may be modified by different wildlife management practices. Therefore indirect effects of herbivores may also vary with these factors. In this thesis, I focus on indirect effects of moose (Alces alces) on plants and animals in the boreal forest and how these effects are modified by moose density, habitat productivity and supplementary winter feeding of moose. I studied effects of moose density and habitat productivity on species composition, growth and reproduction in the field layer vegetation and on abundance and family richness of flower-visiting insects. I also studied effects of a gradient in moose density around supplementary winter feeding stations for moose on bird species richness, abundance and reproduction. Selective moose browsing on preferred species affected species composition in the field layer vegetation, increasing abundance and reproduction in unbrowsed plant species, and decreasing abundance and reproduction in browsed species. Moose browsing in the tree canopy increased light availability and flowering in the field layer as well as family richness of Hymenoptera at sites with high productivity. Moose winter browsing around supplementary feeding stations led to reduced species richness and abundance of insectivorous birds and birds nesting at browsing height. Furthermore, high moose densities led to lower reproduction and food availability for great tits (Parus major), and higher reproduction and food availability for pied flycatchers (Ficedula hypoleuca). Supplementary feeding stations for moose brought nutrients into the system and had a positive effect on species richness and abundance of insectivorous birds, and the size of insect prey. These results show that moose activity can have indirect effects on plants and animals through changed resource availability and habitat structure, and that these effects are modified by habitat productivity and supplementary feeding of moose.