Abstract: There is an increasing need to restore urban ecosystems, which face habitat loss and degradation at higher rates than ecosystems in non-urban areas. However, few studies have tested the consequences of ecological restoration practices in urban contexts. Urban areas are distinct from non-urban areas; they support diverse, often novel, species assemblages in addition to altered environmental conditions and landscape contexts relative to non-urban systems. However, most studies testing the consequences of ecological restoration are conducted in non-urban areas. Thus, it’s unclear if we can extend current knowledge and tools from restoration ecology to urban systems. We lack understanding of fundamental questions, like: how do local and landscape factors structure variation in restoration outcomes in urban settings? To identify these factors, we surveyed 30 urban prairie restoration plantings across three cities in southern Michigan. We collected plant community abundance and composition data in five, 1x1m plots along a 20m transect within each planting. Additionally, we collected site condition data (e.g., soil attributes) and quantified landscape context as the percentage of urban land surrounding each site. Variation in plant community composition across these urban plantings was related primarily to site-level factors, such as soil compaction, texture, and water holding capacity. Non-prairie species responded primarily to the age of the restoration plantings; there was a decrease in both richness (p < 0.05) and abundance (p < 0.05) of non-prairie species with age. This finding is inline with non-urban contexts; target and non-target plant species tend to respond to different sets of factors within the same planting site. Although there were no significant predictors of prairie species richness or abundance, there was some evidence that sites with warmer winters and summers supported lower richness of prairie species (p < 0.08) and older sites supported greater prairie species abundance (p < 0.1). We found the most support for site-level underlying environmental variation driving differences in community composition among restorations. Surprisingly, it appears that unlike findings in some non-urban studies, surrounding landscape structure was not an important force shaping urban plant community composition. Together these findings identify specific factors structuring restoration outcomes in urban contexts, and illustrate the importance of abiotic site conditions, not surrounding landscape context, for shaping plant community composition.
