LAGOMORPHS AND THE DISPERSAL OF SEEDS INTO COMMUNITIES DOMINATED BY EXOTIC ANNUAL WEEDS

Large areas of western rangeland are presently dominated by alien annu al weeds such as Bromus tectorum (cheatgrass). These communities resis t succession to perennial communities primarily because the annuals ar e competitively superior to establishing perennial seedlings and they promote fires that favor weeds over perennials. Succession may be furt her slowed, however, by low rates of seed dispersal into annual grassl ands. We investigated the role of lagomorphs (Sylvilagus muttallii, Nu ttall's cottontail; S. audubonii, desert cottontail; and Lepus califor nicus, black-tailed jackrabbit) in seed dispersal across an ecotone be tween an open juniper woodland and an annual grassland. We collected p ellets along five 100 x 2-m transects parallel to the ecotone: 50 m in to woodland, border, and 20 m, 50 m, and 100 m into grassland. We sear ched pellets for juniper seeds visually and for any other species thro ugh germination from crushed pellets after cold, moist stratification. Pellets were not evenly distributed across transects, but there was n o trend with respect to position of transect. Juniperus osteosperma (U tah juniper) was the most abundant seed. Both the number of juniper se eds and the proportion of pellets with juniper seeds decreased steadil y from a high in woodland to absence at 100 m into grassland. Only 2 d icot seedlings emerged from pellets, 1 Salsola pestifer and 1 unknown that died prior to identification. Consequently, there was little seed movement into the grassland; 72% of all seeds were collected from eit her woodland or border transects. Lagomorphs apparently do not effecti vely replenish the native perennial seed pool of cheatgrass-dominated disturbances at Dugway.