Midwestern oak savannas are among the rarest ecosystems in North America. While these systems were historically fairly common across the Midwestern United States and Canada, a combination of land use change and fire suppression has led to significant habitat loss-- it is estimated that less than one percent of the pre-European settlement oak savanna remains on the landscape. As a result, many species associated with oak savanna systems have become threatened or endangered, such as the Karner Blue butterfly (Lycaeides melissa samuelis), frosted elfin (Callophrys irus), and Persius duskywing (Erynnis persius). In addition, the removal of fire from the landscape has resulted in the mesophication of many oak-dominated systems and a loss of early-successional oak habitat across the Eastern United States. In the context of global environmental change, it is becoming increasingly important to understand the structure and function of rare ecosystems, especially in the context of changing disturbance regimes. In addition, climate change is likely to alter the geographic ranges and distribution of suitable habitat for a number of taxa. Because resources are often limited in conservation and restoration efforts, effectively identifying the most viable sites for management is critically important, in both the short- and long-term. In this context, the work presented here explores the plant community composition of Michigan oak savannas, their response to different management approaches, and the use of the Karner Blue butterfly and other rare species as focal points for site selection at the management-scale, and regionally in the context of climate change. As a whole, the results of this work address several knowledge gaps regarding oak savannas, and Michigan oak savannas in particular. Results suggest that sites within the same oak savanna community type can have quantifiably distinct plant communities as a result of differences in disturbance regime. The demonstrated importance of disturbance frequency and type is further illustrated in a restoration experiment, where results suggest that shear cutting trees may be the most effective mechanical harvesting approach for meeting local management goals. In addition to site-level characteristics, this work indicates that both landscape-level environmental factors as well as climatic factors are important in defining habitat suitability for the Karner Blue, an important and endangered oak savanna indicator species. Finally, this research suggests that climate change is likely to have variable but significant (in terms of conservation) effects on the distribution and accessibility of suitable habitat for three rare oak savanna butterflies.
University of Minnesota Ph.D. dissertation. August 2015. Major: Natural Resources Science and Management. Advisor: Linda Nagel. 1 computer file (PDF); vi, 230 pages.
Using Observational, Experimental, and Focal Species Approaches to Inform the Adaptive Management of Oak Savanna Ecosystems in Western Michigan, USA.
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