Interactive effects of species, simulated grazing, and below-ground resources on competitive outcome among three prairie grasses1

摘要

We investigated how grass competition is influenced by which species are involved, and the levels of grazing, water (W) availability, and nitrogen (N) availability, as a way to understand how competition influences the dynamics of prairies. We conducted a DeWit greenhouse competition experiment in fall 2003 with these three common C^sub 4^ grasses native to Oklahoma prairies: little bluestem (Schizachyrium scoparium), sideoats grama (Bouteloua curtipendula), and indiangrass (Sorghastrum nutans). These grasses were subjected to three clipping treatments to simulate grazing, two W treatments, and two N treatments. We found that: (1) for little bluestem, different aspects of growth were reduced by intraspecific competition, by interspecific competition with sideoats grama, and by the high clipping treatment, but both W addition and N addition increased growth; (2) for sideoats grama, growth was reduced by clipping, but W addition, N addition, and W addition × low clipping increased growth, and (3) for indiangrass, growth increased with W addition and with N addition, but was reduced by intraspecific competition. We conclude that grass seedlings were more affected by the identity of the competitor species and by clipping than by levels of W and N, that intraspecific competition dominated over interspecific competition, and that species × clipping was the most significant interaction effect. [PUBLICATION ABSTRACT]