Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2002
Publication Date: October 1, 2002
Citation: PETERS, D.C. RECRUITMENT POTENTIAL OF TWO PERENNIAL GRASSES WITH DIFFERENT GROWTH FORMS AT A SEMIARID-ARID TRANSITION ZONE. AMERICAN JOURNAL OF BOTANY. 2002. V. 89. P. 1616-1623. Interpretive Summary: Recruitment of perennial grasses following disturbance is a critical process in remediation of rangelands following shrub invasion. In this study, we examined two aspects of recruitment (seed production, presence of seeds in the soil) for two dominant grasses found in arid and semiarid regions of the Southwest: blue grama (Bouteloua gracilis) and black grama (Bouteloua eriopoda). We found that black grama plants produce more seeds with lower viability than blue grama plants, and fewer black grama seeds were found in the soil compared with blue grama seeds. In addition, black grama plants growing in communities co-dominated by shrubs had the fewest seeds produced with the lowest viability and storage in the soil. These differences in recruitment along with published differences in rates of seedling establishment and vegetative spread, may explain, at least in part, localized patterns in species dominance in the presence of disturbances.
Technical Abstract: The objective of this study was to quantify differences in recruitment potential (seed production, seed presence in the soil) for two congeneric perennial grasses (Bouteloua gracilis, Bouteloua eriopoda [Poaceae]) that dominate adjacent arid and semiarid grassland biomes. It was hypothesized that these species have different recruitment strategies at the biome transition zone that are related to differences in their growth form and longevity. Recruitment potential for each Bouteloua species was compared in patches dominated by one or both species or codominated by the invasive shrub, Larrea tridentata (Zygophyllaceae). Regional variation in recruitment was examined for B. gracilis for cases in which comparable data were available in the literature for a site located within the semiarid grassland biome. The short-lived stoloniferous species B. eriopoda produced more seeds per plant than the long-lived bunchgrass B. gracilis, yet seed viability (<60%) and presence in the soil were lower. Mean viability of B. gracilis was higher (>90%) than that of B. eriopoda, and a greater percentage of seeds produced on a square meter basis was found in the soil (10¿25%). Similar patterns were found for both species in all grass-dominated patches. Bouteloua eriopoda plants growing in patches codominated by L. tridentata produced fewer seeds per plant with lower viability, and fewer seeds were found in the soil compared to grass-dominated patches. Regional comparisons found greater seed production per square meter and more seeds in the soil for B. gracilis at the transitional site compared with a cooler, wetter site located within the semiarid grassland biome. These differences in recruitment potential along with published differences in rates of seedling establishment and vegetative spread may explain, at least in part, localized patterns in species dominance.