Vegetation Associated with Nest Sites of Western Harvester Ants (Pogonomyrex occidentalis Cresson) in a Semiarid Grassland

Abstract

We evaluated the effects of western harvester ants (Pogonomyrex occidentalis Cresson) on short-term revegetation on their nest sites in a semiarid grassland in northeastern Colorado [USA]. Storage of germinable seeds in the soil of nest sites, biomass of plants around nest sites, longevity of nest sites and effects of date of nest abandonment were studied. Perennial plants dominated the nest sites 1 year after abandonment, whereas annuals dominated the seed bank on the nest sites. Significant differences in plant recovery and seed storage occurred on the cone-shaped mound and the surrounding circular disk. Significantly more annuals occurred on the mound than on the disk reflecting the significantly greater number of seeds of annuals stored in the mound compared to the disk. The perennial grass Bouteloua gracilis (H.B.K.) Lag. ex Griffiths, which dominates most shortgrass communities, was not found on abandoned nest sites nor were its seeds stored in the soil of the mound or disk.