Mechanisms of Species Loss and Biotic Homogenization in Forest Herb Communities II.

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Mechanisms of Species Loss and Biotic Homogenization in Forest Herb Communities II. Waller, Donald M. University of Wisconsin-Madison Historical data for northern forests and southern prairies of Wisconsin reveal systematic declines over the past 50 years in rare species and species richness. Several mechanisms might account for these losses including shifts in disturbance regimes, invading weedy exotics, overabundant herbivores, stress from acid deposition and climate change. This project will test these potential mechanisms by examining detailed patterns of change in understory plant communities. This project exploits a unique data set compiled by Curtis and colleagues in the early 1950's that provides accurate baseline data on species occurrences and abundances across hundreds of sites. More than 70 forest sites in southern Wisconsin will be resurveyed to determine the nature, rates, and causes of ecological change in these communities. These results will be compared to the historical Curtis data to chart changes in over-story and under-story composition, invasions by exotics, and rates of species loss and biotic homogenization. Overall, 11 alternative mechanisms of species loss (succession, fire suppression, invasion by exotics, climate change, grazing by deer, etc.) will be tested. Detailed site histories and GIS analyses of some sites will allow an assessment of local disturbance history and landscape context. This project exploits a unique historical data set to identify the mechanisms causing plant community changes. It will pinpoint declining species and greatly expand understanding of how overall community composition responds to local and regional conditions. Such results are of broad significance to forest and wildlife managers charged with managing forests, exotics, and keystone herbivores like deer. Finally, the project would support outreach efforts to natural resource managers, educators, and the public to ensure that these results gain broad attention and appropriate responses.