Influences on Understory Plant Communities in Mesic Uplands of the Chequamegon National Forest, Wisconsin
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Date
2011-12Author
Nelson, Helana L.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
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Show full item recordAbstract
Recently, researchers have shown that understory communities in northern
Wisconsin are converging in composition, a process termed homogenization. They have
also identified possible mechanisms for homogenization including whitetail deer
herbivory and exotic earthworm introductions. Homogenization can result from species
losses, introductions, or both, and may contribute to changes in diversity over time. This
study focused on documenting changes in understory plant communities in mesic uplands
of the Chequamegon National Forest in northern Wisconsin since the early 1990’s, and
identifying possible influences of such changes. Permanent plots, originally established
by the U.S. Forest Service, were revisited in the summers of 2008 and 2009. Data were
collected on understory vegetation, earthworm abundance, and deer browsing in both
managed and unmanaged forests, which were compared to previous measurements from
1990-1992. Species richness and diversity (H’) were not statistically different from the
early 1990s. Present diversity and richness did not differ between managed and control
units. Exotic species were not common, averaging <1 per unit. Neither increasing
earthworm biomass nor increasing deer browse pressure impacted richness or diversity.
However, the relationship between earthworm abundance and richness was nearly
significant. Management did not contribute to increased compositional similarity over
the study period. However, there was a 22% convergence in relative abundance and
composition over the study period. Forest managers should be aware of the observed
increases in community similarity and monitor potential drivers of homogenization.
Future monitoring efforts in the Chequamegon should take into account changes in plant
assemblages, sensitive species and growth forms, in addition to measures of diversity.