Wildfire and prescribed burning impact moose forage availability and browsing levels in the northern boreal forest

Abstract

Fire regimes and herbivore densities have in parts of the boreal been heavily impacted by human activities with consequences for vegetation, forage supply and ungulate use. In this study, we evaluate the effects of natural wildfires and prescribed burning on moose forage availability, use, and browsing in northern Sweden. We studied three wildfire locations, adjacent controls, and five prescribed burns 12 years after fire. To compare forage availability and browsing levels we combined related variables with Principal Component Analyses and used the first axis in a regression analysis. The wildfire locations had a different composition of forage compared with the controls with less forage in the field layer and more woody browse and deciduous saplings. Forage availability was best explained by the occurrence of fire and differed between wildfire and the unburned control areas. Browsing levels were higher in wildfire locations compared with unburned controls. Prescribed burns varied substantially and could resemble both unburnt control and wildfire in terms of forage availability and browsing. We conclude that prescribed burning as a restoration action potentially can improve forage availability, particularly of deciduous species, if they mimic the impact of wildfires in terms of larger area burned and high fire severity.