Seed movements and seedling fates in disturbed sagebrush steppe ecosystems: Implications for restoration

Understanding species establishment patterns and community structure follow ing disturbance, and developing effective restoration methods requires know ledge of both the movements and fates of seeds. I used a restoration experi ment in a severely disturbed sagebrush steppe ecosystem near Kemmerer, Wyom ing to examine the effects of soil surface characteristics and seed morphol ogy on seed entrapment and retention, and the effects of soil surface chara cteristics on soil water potential and seedling emergence and survival. See ds of native species with awns, mucilaginous seedcoats, wings, hairy pappi, or no appendages were sown over soil surface treatments consisting of silt y loam sail, sand, gravel, surface mulch, shrub mimics, and large and small holes. Seeds that lacked appendages and that had small surface areas did n ot exhibit significant horizontal movement or redistribution. Seeds with ap pendages that resulted in exposure of a large surface area to the wind did exhibit significant redistribution, despite apparent adaptations for seed b urial or retention. When the entire seed population was considered, the eff ectiveness of the treatments for trapping and retaining seeds was large hol es > small holes greater than or equal to gravel greater than or equal to s hrub mimics > soil greater than or equal to sand. Surface mulch neither gai ned nor lost seeds. The most effective treatments for seedling emergence ha d among the least negative soil water potentials and included large holes, surface mulch, and sand. Gravel provided an inadequate growing medium, and both shrub mimics and small holes accumulated fine-textured soils resulting in highly negative water potentials and low seedling emergence. Once a see dling emerged, the probability of survival was reasonably high (56.3% over 2 yr) regardless of treatment. This study indicates that soil surfaces that trap and retain high densities of seeds with large surface areas may have little or no effect on seeds with small surface areas, and may or may not r esult in high seedling emergence and survival. Restoring diverse native eco systems requires creating soil surface features that can trap and retain se eds with varying morphologies as well as provide favorable conditions for s eedling establishment.