The effects of recreation disturbance on subalpine seed banks in the RockyMountains of Montana

We investigated the soil seed bank in a subalpine ecosystem with patchy dis turbance from camping. Soil cores were collected from three site types, hea vily impacted, lightly impacted, and undisturbed, that differed in area of bare ground and depth of surface organic matter. We hypothesized that the d ensity and composition of the seed bank would vary with depth of surface or ganic matter and distance from established vegetation. Seedling emergence w as determined in the greenhouse. Seed density was significantly lower on di sturbed sites, averaging 441 seeds/m(2) on heavily impacted sites, 1495 see ds/m(2) on lightly impacted sites, and 4188 seeds/m(2) on undisturbed sites . Seed density declined exponentially with distance from established vegeta tion and increased with depth of surface organic matter. The number of spec ies present did not vary across site types, but 10 species that occurred on lightly impacted and undisturbed sites were not present on heavily impacte d sites. We concluded that disturbance that causes removal of surface organ ic matter can affect natural revegetation by lowering the density of propag ules and affecting the species represented in the seed bank.