Red harvester ant nests impact soil compaction but not temperature in peri-urban habitats of the Lower Rio Grande Valley

Abstract

ABSTRACTAnts are vital ecosystem engineers that can influence soil properties, subsequent soil processes, and associated biota via underground nest construction. Harvester ants consume seeds and are often found in arid areas, frequently altering soil chemistry and bulk density of the soils in and around their nest sites. Many species of harvester ants also intentionally remove vegetation around nest openings, creating cones or discs of bare soil that may further alter soil temperatures. However, much of the work investigating the impacts of harvester ants on soil properties has occurred in shrubland and grassland settings rather than suburban environments. We aimed to determine ifPogonomyrmex barbatus(Smith) (Hymenoptera: Formicidae) nests in a suburban habitat in the Lower Rio Grande Valley in Texas similarly altered soil properties. First, we measured active nest disc size to determine changes and colony persistence. Then we assessed soil compaction and surface temperature along a gradient centered on the disc. We found that disc size did not increase throughout the two-year observation period and that nests with smaller discs were less likely to persist between years. While we did not observe any changes in surface temperature across the gradient, we found a significant increase in soil compaction with greater distance from the center of the disc. These data indicate that increased nest size increases the extent of soil impacted. The impacts of nests reducing soil compaction, particularly within a suburban landscape with precipitation run-off issues and a highly disturbed plant community should be addressed in future studies.