Butterfly and floral community dynamics at a native prairie agrofuel research site

Agrofuel production in the Midwest has historically relied upon monoculture food crops (Zea mays and Glycine max) that do little to support biodiversity or maintain soil and water quality. The University of Northern Iowa’s Tallgrass Prairie Center is investigating the feasibility of establishing and harvesting diverse mixes of native prairie vegetation for use as a sustainable agrofuel. In 2009 48 research plots were established on three soil types, on land with a \u3e30 year history of row crop production in Black Hawk County, IA. Each plot was seeded with one of four native prairie agrofuel crops: (1) Switchgrass1, (2) Grasses5 (5 warm season grass species), (3) Prairie16 (16 species of grasses, legumes, and forbs), or (4) Prairie32 (32 species of grasses, legumes, forbs, and sedges). Research plots were actively managed with a three-year rotation (establishment/no management, burn, harvest), and in 2013 and 2014 a significant portion of the research site experienced early summer flooding. I monitored floral and butterfly communities present on site from 2010 through 2014 and hypothesized that more diverse floral communities would support more abundant and diverse butterfly communities. Butterflies were ~3.6 times more abundant, ~1.4 times more species rich, and more diverse in Prairie16 and Prairie32 than Switchgrass1 and Grasses5; however butterfly abundance, richness and diversity in Prairie16 and Prairie32 did not diverge as the site matured as predicted. Sown flowers were more species rich and diverse, but not more abundant in Prairie32 than Prairie16. Flooding frequency and duration was a strong predictor of sown floral abundance, richness and diversity; which in turn influenced butterfly abundance. My research suggests that the widespread adoption of diverse assemblages of native prairie plants as agrofuel crops would provide higher quality habitat for butterflies than native, grass-only agrofuel feedstocks