A 22-year study on the effects of mammalian browsing on forest succession following a clearcut in northern lower Michigan

Tree stems were systematically sampled in 1983, 1988 and 1999 in a 1977 clearcut in the Pigeon River State Forest, Michigan. All stems were identified to species and recorded as living or dead and browsed or unbrowsed by mammalian herbivores, based on inspection of twigs and buds. Tree species richness increased in the study area, mostly due to the presence of several wind dispersed species previously not recorded. The abundance of all trees collectively declined over the study period as the clearcut aged and the relative abundance of the most preferred (and most common) browse species in 1983 declined to 0.0 by 1999. There was no evidence that mammalian herbivores were using the clearcut for feeding in 1999, suggesting decline of use as preferred species declined. About half the study area sampled in 1999 was dominated by herbaceous species, whereas the entire area was dominated by young woody growth in earlier years. The results collectively suggest that high degrees of sustained browsing affect community structure and composition by lowering abundance of more preferred species over time.