Nicole+Craig+Thesis

Abstract
In Dane County, Wisconsin, where prairies and savannas once dominated the landscape, rain gardens are being utilized with increasing frequency in restoration efforts to counteract the damaging impacts of urbanization upon the natural hydrologic cycle. However, little is known about the biological or social properties of rain gardens, how they compare to the natural systems they attempt to emulate, or how they are accepted in urban and residential societies. To examine the biotic and social aspects of Dane County rain gardens, I investigated temporal variations in microbial communities in experimental rain gardens, performed a Dane County-wide assessment of biotic and physical properties of rain gardens, lawns, and prairies, and conducted a social survey to evaluate rain garden owners’ attitudes toward and understanding of their rain gardens’ appearance and function.

In a study of temporal variations in microbial communities, I characterized microbial community composition in two experimental rain gardens over a six month-period using membrane lipid analysis. I found that rain garden microbial communities, while not directly related to plant diversity, appeared to be affected by plant phenology as microbial community composition experienced seasonal shifts. Most notably, the summer/fall seasonal community shift corresponded with increased relative abundance for the protozoal lipid indicator, which was thought to be related to increased water content within the rain gardens. Experimental rain gardens were also found to have microbial communities distinct from those found in other rain gardens, as well as restored prairies, suggesting the impact of soil legacy effects.

In order to examine variations among rain gardens on a county-wide scale, I studied the relationships between microbial communities, soil habitat, and rain garden construction variables for 45 rain gardens within Dane County Rain garden microbial communities had variations evident on the county-wide scale that were related to spatial, temporal, soil habitat, and rain garden construction variables. For instance, as rain garden vegetation cover (a rain garden construction variable) increased, arbuscular mycorrhizal fungi relative abundance increased, a trend that was also related to increased rain garden age. In this study, lawns and prairies were also sampled to assess the ability of rain gardens to mimic more natural systems below-ground and gauge rain gardens’ ‘below-ground restoration’ success. I found that rain garden and lawn microbial communities are both bacterially dominated, while prairie microbial communities are fungally dominated, suggesting that rain gardens are not quite completed prairie restorations. However, rain garden microbial communities appear to more closely resemble prairie communities with time, suggesting that further work should be performed upon these rain gardens as they mature in order to track community composition changes and gauge restoration success.

Finally, I examined social characteristics of Dane County rain gardens through an examination of rain garden owners’ attitudes and opinions. Little is known about why owners install rain gardens, the resources they invest in this process, or how they learn about rain gardens. Rain gardens are being implemented with increasing frequency and many local organizations are promoting rain garden installation to homeowners, which I found to be influential in shaping owners’ knowledge about rain gardens. I also found that rain garden owners have positive opinions of their rain gardens’ appearance and performance and most owners invest large amount of time, money, and labor in their rain gardens. From these results, I recognize the importance of local organizations in the dissemination of rain garden information and offer recommendations to improve future rain garden promotion to Dane County residents, particularly regarding rain garden aesthetics.