PARENT SESSION
Poster Session #32: Plant Ecology I.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Colonization and species richness in grassland: effects of micro-site availability, resource supply and seed availability.

Dickson, Tim¹, Foster, Bryan¹, ¹

ABSTRACT- Understanding how local processes interact with the species pool to regulate community composition and diversity is a major objective in community ecology. We established a field experiment in a northeastern Kansas grassland to investigate the relative roles of micro-site availability, local soil resource supply (water) and seed availability in regulating plant establishment and small-scale species richness. We applied a 2 x 2 x 2 factorial arrangement of treatments to 64, 1 x 1 m field plots. Treatments included two levels of micro-site manipulation (moderate surface soil disturbance; no soil disturbance); two levels of irrigation (irrigation; no irrigation); and two levels of seed addition of 32 grassland species selected from the regional species pool (seeds added; no seeds added). In the first year of the study, irrigation significantly increased seedling establishment and small-scale species richness, both in the absence and presence of seed addition. Seed additions significantly increased seedling establishment and species richness, both in the non-irrigated and irrigated plots, however, the magnitude of these effects were substantially greater in the irrigated plots. Although disturbance influenced the establishment of particular species, it had little impact on overall seedling establishment rates and species richness. The results suggest that species colonization rate and small-scale species richness in this grassland are constrained by species availability and local resource supply.

KEY WORDS: colonization, grassland, species availability, species richness