Biomass Allocation of Two Types of Prairie Vegetation used for Bioretention in Urban Compacted Soil.

Soil compaction restricts plant productivity and soil drainage. In the urban landscape, alternative types of vegetation have been suggested to mitigate the effects of soil compaction through belowground interactions with soil structure. Prairie plants with productive root systems have been promoted for increasing the infiltration of urban stormwater via bioretention while mediating urban compaction, yet these responses have not been quantified. We investigated how soil compaction typical of urban development altered the allocation of biomass in two species of prairie plants characterized by different rooting patterns. We compared a tap-rooted species (Ratibida pinnata, yellow coneflower) and a fibrous-rooted species (Heliopsis helianthoides, early sunflower) that typically establish well after planting and exhibit aggressive growth. All plants were grown in the greenhouse in planting containers (0.07 m³) receiving a soil treatment typical of residential developments in Madison, WI. In half of the containers, we increased the bulk density of a sandy loam from 1.4 to 1.9 Mg m^-3 at a depth of 0.15-0.33 m. We monitored aboveground growth on a weekly basis and measured belowground biomass and root distributions via destructive harvest at the end of the growing season. We report the results of this experiment along with inferences on how these plants might be used for bioretention in urban ecosystems.