ALPINE SEEDLING ESTABLISHMENT - THE INFLUENCE OF DISTURBANCE TYPE

On the Beartooth Plateau, SW Montana, the authors compared soil temperatures, water potentials and nutrients on mineral soils of a gravel borrow area with those on highly organic soils of a Geum turf area. Seedling emergence, growth, and survival of 6 seeded species (Geum rossii, Artemisia scopulorum, Potentilla diversifolia, Sibbaldia procumbens, Deschampsia cespitosa, Festuca idahoensis) and emergence and survival of 5 unseeded species (Draba crassifolia, Draba incerta, Cerastium arvense, Arenaria rubella, Androsace septentrionalis) were evaluated. Seedling emergence was highly dependent on soil surface stabilization and reflected species life history traits. Growth of seedlings was slow, and varied among species and treatments: 0.005-0.04 and 0.02-0.20 g total mass after the 1st and 2nd growing seasons, respectively. Significantly higher total seedling mass was observed on cleared turf plots than on any of the borrow area treatments, and on fertilized than on not-fertilized plots on the borrow area. Seedling mortality of most species was much lower than previously found for alpine ecosystems, rarely exceeding 50% even after 2 yr. On the borrow area mulch increased survival, probably through microenvironmental amelioration. The nutrient pulse from fertilization increased mortality of several species, presumably by creating uplant nutrient demands in excess of availability during year 2. In general, there were larger differences among species in emergence and growth than in survival. -from Authors