Factors Affecting Abundance of Beaver Dams in Forested Landscapes

Mathilde Lapointe St-Pierre
Julie Labbé
Marcel Darveau
Louis Imbeau
Marc J. Mazerolle

Beavers are ecosystem engineers that contribute to landscape heterogeneity in North American boreal forests. Despite the importance of beavers on landscapes, beaver distribution is still poorly understood, particularly at large spatial scales and in different ecoregions. The goal of our study was to determine the main environmental features affecting beaver dam abundance across ecoregions. We quantified the spatial distribution of beaver dams in Quebec forests using 257 systematically distributed provincial forestry maps, in which we sampled 1025 plots of 25 km2 in an area several orders of magnitude larger than in previous studies. The study area, covering over 300,000 km2, spanned over six ecoregions (Appalachians, Meridional Laurentians, Central Laurentians, Abitibi and James Bay Lowlands, Mistassini, and Anticosti Island). We constructed 17 candidate regression models using a negative binomial distribution with variables based on different hypotheses to explain beaver dam abundance. The mean stream gradient was the top variable influencing dam abundance, followed by the cover of non-forested land. However, there was substantial variability among ecoregions, as the models that included the random effect of hardwood cover and non-forested cover ranked higher than models without these variables. We conclude that such regional variation in factors affecting dam distribution patterns should be taken into account when establishing beaver management plans.