The Influence of Fire and Other Environmental Factors on Terrestrial Gastropod Species Composition in an Oak-Hickory Woodland of West-Central Illinois

Abstract: Terrestrial gastropods are important herbivores, prey, and as decomposers in woodlands of the Midwestern USA. Vegetation structure and composition are dynamic and may influence gastropod abundance and distribution, but relationships among gastropod communities and environmental variables are understudied. We burned three treatment units in an oak-hickory woodland during 2004 and conducted additional burns on two of those treatment units, one in 2014 and the other in 2015. In May and August 2016, we collected leaf litter containing gastropods from transects within these three burn treatment units and used 19 environmental variables that were potentially important to gastropods. Environmental variables were associated with herbaceous and woody vegetation, ground cover, physiography, and burn history. We identified 14 species of gastropods at the study site. No significant environmental models were found for gastropod abundance, richness, effective number of species (based on Shannon entropy), or effective number of species (based on the Gini-Simpson index). Statistically significant associations among gastropods and environmental variables were seen in three species. Euchemotrema leaii was associated with areas having low coverage of shrubs and other perennials, and abundant leaf litter, whereas Neohelix alleni was positively associated with leaf litter and was abundant in areas with low total cover. Glyphyalinia indentata was associated with higher elevation transects, may be impacted by recent burning, and was found in areas with greater amounts of grasses and vines.