From delayed succession to alternative successional trajectory: How different moose browsing pressures contribute to forest dynamics following clear‐cutting

Abstract

AbstractAimsSelective browsing can be a chronic disturbance that reduces the survival, growth and reproduction of individual species and shapes the composition and structure of plant communities. Along with other disturbances that perturb the forest ecosystem, browsing may thus affect forest regeneration and successional trajectories after an acute perturbation such as clear‐cutting. However, effects of different browsing pressures on plant species, communities and ultimately succession remain hard to predict.MethodsWe implemented a browsing exclusion experiment (n = 15 sites) along a gradient of moose browsing pressure to investigate how this factor influenced the early‐successional trajectory of boreal forests following clear‐cutting in eastern Canada. We used Principal Response Curve analyses to compare the trajectory of the plant communities depending on site‐specific moose browsing pressure and analyzed the trajectory of individual species leveraging these curves.ResultsOur results show that all browsing pressures lead to alterations in plant communities when compared to exclosures, but the effect was stronger under heavier browsing pressure. Under heavier browsing pressure, we observed a lower ground cover of balsam fir, an increased ground cover of raspberry, reaching more than 60%, and a lower abundance of saplings for balsam fir, birches and rowan.ConclusionsThis study demonstrated that forest response to browsing is a function of local browsing pressure and that moose mainly slowed forest succession toward a closed canopy. However, heavier browsing pressure, through reduced sapling abundance and the resulting increased cover of competitive raspberry, may delay forest succession and push the ecosystem toward an alternative successional trajectory. As heavy selective browsing can interact with anthropogenic disturbances to determine forest succession, we recommend strong integration of the forest and wildlife management sectors to promote sustainability.