The effect of native prairie on rain garden function and qualitative assessment of their implementation by homeowners

Background/Question/Methods Urban development often results in a modification of the native environment, particularly the pre-development hydrologic cycle. Efforts to remediate such impacts traditionally focus on engineered structures such as detention basins that typically go unnoticed and thereby disengage the public from participating in urban ecology. In contrast, urban rain gardens are a best management practice for disconnecting residences from the sewershed by treating stormwater on-site. Moreover, rain gardens directly engage the public; they are implemented within residential lawns and typically include landscaping plantings of prairie vegetation. However, few studies have examined their ecological effectiveness relative to vegetation type, nor the variation of implementation practices used by the public. First, we examined differences in soil bulk density, soil organic matter (SOM), and hydraulic conductivity in prairie gardens relative to adjacent turfgrass lawns. Second, we conducted a qualitative assessment of garden design and implementation. We sampled soil at twelve private residences located throughout Madison, Wisconsin where homeowners had established prairie gardens as part of their landscaping plan. We categorized sites by the age of prairie garden and by the age of residence. We collected qualitative data including site history, photography, planting lists, and maintenance practices.

Results/Conclusions

Preliminary results showed both development age and the presence of prairie vegetation contributed to building soil structure, particularly within the surface 18 centimeters. Older developments (homes built prior to the 1970s) tended to have lower bulk density, greater hydraulic conductivity, and less penetration resistance than newer sites. Prairie gardens exaggerated these changes by contributing SOM to soil structural development, as they possessed greater SOM (4.3%) than lawn (3.8%) and appeared to accumulate this SOM within macroaggregates (2000-250 μm). These results support the use of alternative plantings such as prairie vegetation in urban rain gardens and highlight the age of development on their effectiveness. In this presentation, I will present our findings related to our quantitative study, as well as the qualitative assessment of rain garden implementation.