Browse-Mediated Succession by Deer and Elk 40 Y After a Clearcut in Northern Lower Michigan

Abstract

In 2017 we sampled tree stems in a clearcut generated in 1977 in the Pigeon River State Forest, Michigan and compared results to three previous sampling periods completed in 1983, 1988, and 1999, respectively. Trees were recorded by species, height class, and whether or not stems had been browsed by mammalian herbivores and whether stems were alive or dead. The results show the most preferred browse tree species when the clearcut was young (bigtooth aspen) was completely absent by 1999 and thereafter, and tree species richness increased over time. Elk were still using the area in 2017, as shown by the presence of pellet groups and sightings in the clearcut and nearby, but little noticeable browse damage was seen in 1999 or 2017, and tree mortality was negligible in 2017. A total of 22 tree species were identified across the time period, but only five species were recorded as present in all years. A total of 11 species were recorded in 1 y only: six in 1999 and five in 2017. Many species were rare, as defined by relative abundances of <0.01, and relative abundances varied a great deal across time. Stochastic dispersal, establishment, and mortality events likely explain many of these observations, given high mortality rates of seedlings and small saplings due to browsing earlier in succession, and competition for light or other resources as trees aged over time.