Abstract

Topic: Moose and forestry

Investigating the interaction between herbivory and winter conditions on forest succession

Marguerite Morissette¹, Pierre Etcheverry², Jean-Pierre Tremblay³

Département de Biologie, Université Laval - Parc national Forillon, Parcs Canada - Centre d'études de la forêt (CEF), Université Laval, 1501, avenue de la Médecine, Université Laval, CA
Parc national Forillon, Parcs Canada, Gaspé, Québec, Canada
Département de Biologie, Centre d'études de la forêt (CEF), Centre d'études nordiques (CEN), Université Laval

Abstract
Forest management practices, predator extirpation, and harvesting restrictions can increase moose populations, which may ultimately result in long-term and irreversible changes in forest habitat. The selective and chronic pressure of moose on regenerating stems can alter succession and lead to alternative forest states, such as open areas dominated by tolerant and unbrowsed species. Winter conditions modulate browsing pressure by limiting moose movement and reducing food availability. This interaction of moose and snow cover on regeneration, however, remains understudied. This is particularly the case in forest gaps formed by natural disturbances, as the impact of moose is typically studied in logged forest. Our objective is to assess the role of moose browsing and winter conditions in the succession regime in mixed yellow or white birch – balsam fir stands in Forillon National Park (FNP), Quebec, a protected area where moose is abundant and where there is neither wolf nor hunting. To reach this objective, we characterized the composition and structure of regeneration in 55 small (< 1000 m²) natural forest gaps. As opposed to expectation in balsam fir dominated stands, our results revealed a low abundance of balsam fir, with communities being dominated by mountain maple and red-osier dogwood, two shrub species relatively tolerant to browsing. We then characterized historical moose browsing pressure on plant communities. Most forest gaps demonstrated historical pressure from sustained browsing. Finally, we assessed the role of snow on moose browsing by defining the main determinants of snow accumulation patterns and associating them with the browsing pressure determinants. Forest gaps higher in altitude were associated with higher snow depth and were more prone to be dominated by mountain maple. Contrary to expectation, higher snow depth did not seem to attenuate the impact of moose. In conclusion, we confirmed that the abundant moose population in FNP impacted the regeneration of natural forest gaps by documenting changes in forest composition already in effect. In small canopy gaps, those changes seem to be unaffected by snow conditions. To further those results, we aim to study larger persistent gaps where snows patterns are more variable and more susceptible to modulate moose impacts.