Granivores, exclosures, and seed banks: harvester ants and rodents in sagebrush-steppe

Experiments were conducted to assess the influences of granivores on the seed bank in sagebrush-steppe. Rodent and/or ant exclosures were established at two distances from five harvester ant mounds. Monthly soil samples were collected from the exclosures, and from open access areas at two distances to ascertain changes in the seed bank. Seed dish experiments were conducted monthly to establish a maximum seed removal rate. Rodents were trapped monthly. More seeds were recovered from rodent exclosures than from ant exclosures. Seed banks changed temporally and spatially, with more seeds recovered in September and at 6 m from mounds. Rodents removed seeds more rapidly from seed dishes than did ants. Ants removed more seeds from dishes closest to the nests. Rodents may have a larger impact on the local seed bank than harvester ants. Ant activities, other than seed consumption, may have more influence on vegetation.