Maintaining a Pine Legacy in Itasca State Park
Eric K. Zenner
JeriLynn E. Peck
Itasca
State Park, located in the northern central portion of Minnesota, is challenged with maintaining a pine forest covertype, yet regeneration failures may allow much of the park to succeed to northern hardwoods. Efforts to improve pine regeneration and growth have included deer exclosures and prescribed burning to reduce competing vegetation. We revisited Itasca’s MaryLake deer exclosure 66 years after establishment to compare stand development, structure, and white pine (Pinus strobus L.) regeneration and growth with that of adjacent plots that have been: (1) untreated and (2) recently repeatedly under-burned. Overstory structure and composition was similar among all three treatments, and mid- and understory structures were similar in the treatments subject to deer browse. Sapling and midstory white pine were only present in the exclosure. White pine regeneration was present in all treatments and most abundant in the burned treatment, but was restricted to the smallest height class and consistently overtopped by the shrub layer. Regeneration, sapling, and midstory layer tree densities were highest within the deer exclosure, as was white pine height growth. The untreated plot lacked young pine and will likely succeed to northern hardwoods with a shrub understory. The three-fire sequence of the burned treatment increased the abundance of white pine regeneration at this site, but may require additional measures to control competing vegetation to allow that regeneration to ascend into the sapling layer.
Forty-seven Year Changes in Vegetation at the Apostle Islands: Effects of Deer on the Forest Understory
Erika L. Mudrak
Sarah E. Johnson
Donald M. Waller
White-tailed deer (Odocoileus virginianus Zimmerman) have been labeled a keystone herbivore in forests of the midwestern United States, particularly as deer have increased over the past century due to forest fragmentation, reduction of natural predators, reduced hunting, and mild winters. Deer browsing in the Apostle Islands National Lakeshore has had a pronounced effect on formerly large continuous patches of reproductive Canada yew (Taxus canadensisMarshall). In order to compare understory plant communities in 2005 to those at sites sampled in 1958, we resurveyed 32 forest sites on islands that remained free of deer throughout this period, on islands that retained deer, and on islands that gained or lost deer. Multivariate analyses reveal that deer have strong effects on the type of change in the forest understory. Plant communities on sites with long-term deer pressure are becoming increasingly different from those on sites that have never had deer. Four new understory species were detected at these sites, two other species increased by more than 20%, while eight decreased by more than 20%. While grasses and sedges were favored on sites that maintained or gained deer, perennial forbs declined conspicuously on these sites. The recovery of understories on islands where deer were removed suggests that such actions can effectively restore suitable habitat conditions for certain species sensitive to deer herbivory.