Birds and butterflies respond to soil-induced habitat heterogeneity in experimental plantings of tallgrass prairie species managed as agroenergy feedstocks in Iowa, USA

Authors: MYERS, MARK - University Of Northern Iowa; MASON, JAMES - University Of Northern Iowa; HOKSCH, BENJAMIN - University Of Northern Iowa; Cambardella, Cynthia; PFRIMMER, JARRETT - South Dakota State University

Submitted to: Journal of Applied Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2015
Publication Date: 7/19/2015
Citation: Myers, M.C., Mason, J.T., Hoksch, B.J., Cambardella, C.A., Pfrimmer, J.D. 2015. Birds and butterflies respond to soil-induced habitat heterogeneity in experimental plantings of tallgrass prairie species managed as agroenergy feedstocks in Iowa, USA. Journal of Applied Ecology. 52(5):1176-1187. doi: 10.1111/1365-2664.12503.

Interpretive Summary: Agricultural production and homogenization of land management practices over the past century have resulted in wide-spread loss of plant and animal biodiversity. Current and projected expansion of bioenergy crop production in the Midwestern USA has the potential to dramatically alter agricultural land use. This study provides field data on short-term changes in plant, bird and butterfly community characteristics after several perennial bioenergy production systems were established on three distinct soil types in north-central Iowa. We found that bird and butterfly communities responded to soil-induced changes in habitat heterogeneity. For instance, low-diversity grass-dominated plots on sandy loam soil had more bare ground with shorter, less dense vegetation compared to vegetation on loam and clay loam soils. Consequently, bird communities on sandy loam soil were dominated by species preferring open ground and sparse vegetation for foraging and nesting, whereas loam and clay loam communities were dominated by birds preferring taller, more dense vegetation. Our results demonstrate that perennial bioenergy crops established with identical seed mixes and uniform management practices developed different habitat characteristics for different soil types and the animal communities were structured in response to this heterogeneity. The findings also have important implications for grassland restoration and biodiversity conservation in landscapes dominated by agriculture. Our results suggest that if particular animal species are being targeted for conservation, identifying soil types that will support the establishment and/or growth of plants in a manner that yields the particular habitat characteristics required by the target species should be a primary consideration in assessing and selecting potential sites for restoration and management. These results will provide information to land managers for development and implementation of bioenergy cropping systems that enhance biodiversity in the Midwest.

Technical Abstract: The positive association between habitat heterogeneity and species diversity has been well-documented for many taxa at various spatial and temporal scales, and the maintenance of habitat heterogeneity in agricultural landscapes has been promoted as a key strategy in efforts to conserve biodiversity. We conducted a large-scale field experiment to study the direct effects of soils on vegetation composition and structure and their indirect effects on bird and butterfly communities in experimental plantings of native tallgrass prairie species managed as agroenergy crops in Iowa, USA. In 2009, we sampled surface soil properties in 48 research plots established on three soil types (Flagler sandy loam, Waukee loam, and Spillville-Coland complex) in seven agricultural fields with a >20 year history of annual row crop cultivation. We randomly seeded each plot with one of four vegetation treatments containing one, five, 16, or 32 species of perennial tallgrass prairie plants. In 2010, the first growing season where seeded native perennials dominated the plant community, we monitored habitat characteristics and surveyed bird and butterfly communities in the plots. Bird and butterflies responded to soil-induced habitat heterogeneity in the experimental plots in a similar manner. Neither bird nor butterfly abundance, species richness, or community diversity varied among the three soil types; however, there were significant vegetation treatment × soil type interactions when comparing bird and butterfly community composition among plots. Low-diversity grass-dominated plots on sandy loam were characterized by more bare ground with shorter, less dense vegetation and sparse litter accumulation compared to vegetation on loam and clay loam plots. Consequently, bird assemblages on sandy loam were dominated by species preferring open ground and sparse vegetation for foraging and nesting, whereas assemblages on loam and clay loam were dominated by birds preferring taller, more dense vegetation with abundant litter. In high-diversity forb-rich plots, not only vegetation structure but also the species composition of forbs in bloom varied among soil types, which affected butterfly community composition. Our results demonstrate that perennial agroenergy crops established with identical seed mixes and uniform management practices developed variable habitat characteristics due to underlying edaphic variation and that animal communities were structured in response to this heterogeneity. Our results highlight the importance of considering soils in the selection of sites for grassland restoration in agricultural landscapes, and we suggest that variation in habitat characteristics resulting from differences in soil properties may be an overlooked source of heterogeneity in plantings of native perennials managed as agroenergy crops in the Midwestern U.S.