Effects of Basal-Resource Augmentation on Intraguild Predation and Decomposition in a Soil Food Web

Intraguild predation (IGP) is a ubiquitous omnivory module that can be a bottom-up and top-down force in community structuring. A two-year experiment was completed at The Morton Arboretum in Lisle, IL to answer, how does artificial basal resource enhancement change soil microarthropod community structure and role of IGP as a community-structuring force, and how do these changes affect microbial activity? Two hundred 1 m2-plots received one of three levels of detrital enhancement intended to increase the abundance of saprophytic fungi. A large increase in abundance of small-sized fungivore prey observed both at the end of year 1 and year 2. The mite family Parasitidae, a large predator, increased in abundance in response to fungivores at the end of year 1. At the end of year 2, the increase large predator abundance was more pronounced. Path analyses revealed IGP was the most influential structuring force in the Low-level enhancement group at the end of year 1. In year 2, IGP was observed in all treatment groups and was the only significant interaction in Low-level treatment plots. A proxy for microbial activity, cotton strip tensile strength loss (CSTL), was highest in High-level enhancement plots than any other treatment, followed by Low-level enhancement plots. A path analysis revealed that fungivores in communities receiving Low-levels of enhancement had a negative effect on CSTL. This suggests strong inhibition of microbial activity resulting from a combined effect of lesser microbial growth from Low enhancement plus intraguild predation that reduced predation on the fungivore common resource.