Moose population density and habitat productivity as drivers of ecosystem processes in northern boreal forests

摘要: Ungulates have traditionally been viewed as consumers of plants and prey for predators, but recent studies revealed that they also can a significant indirect impact on fundamental ecosystem processes biodiversity. In my thesis, I focus how moose (Alces alces) affect the boreal forests in Sweden. Because its wide distribution at present high population densities we expect to be important. The outcome depends density well habitat productivity, chose an experimental approach where simulated browsing, defecation urination different exclosures situated along forest productivity gradient. simulation was based review available literature. found morphology main food winter, Scots pine (Pinus sylvestris) birch (Betula pubescens B. pendula). highly dependent density. At “low” “moderate” densities, small non-significant effects were found, whereas large higher densities. concluded both foraging efficiency availability affected over extended time, production may steadily decrease level winter is limiting. Habitat type results. low productive sites had thus compensatory ability defoliation by moose. Birch seemed respond differently explanation might pines suffered from competition with deciduous trees richer sites. quantity quality (species mix) litter tree shrub layers habitat. Richer produced more (i.e. lower proportion conifer needles). decreased needles increased Despite browsing pressure pine, general time seems litter, reduced nutrient cycling long run. Decay rates dung appeared rather low, suggesting fertilizing effect low. However, disappeared fast due concealment vegetation, visibility negatively correlated production. coprophilous community colonizing species rich poorly known, abundance richness are interactions other organisms type. thesis show biodiversity Swedish forests, act important engineer. Productivity gradients consider when studying level. Based findings, suggest should done species, field bottom layers, soil properties, microclimate, connected faeces urine.