Semiarid grassland responses to short-term variation in water availability
- 130 Downloads
Standing crop and species composition in semiarid grassland are linked to long-term patterns of water availability, but grasslands are characterized by large single-season variability in rainfall. We tested whether a single season of altered water availability influenced the proportions of grasses and shrubs in a semiarid grassland near the northern edge of the North American Great Plains. We studied stands of the clonal shrub snowberry (Symphoricarpos occidentalis) and adjacent grassland dominated by the native grasses Stipa spartea and Bouteloua gracilis. Rain was excluded and water supplied in amounts corresponding to years of low, medium, and high rainfall, producing a 2 − 4-fold range in monthly precipitation among water supply treatments. There were ten replicate plots of each water treatment in both snowberry stands and grassland. Grass standing crop increased significantly with water availability in grassland but not inside snowberry stands. Total standing crop and shrub stem density increased significantly with water supply, averaged across both communities. In contrast, water had no effect on shrub standing crop or light penetration. In summary, our finding that water has significant effects on a subset of components of grassland vegetation is consistent with long-term, correlational studies, but we also found that a single season of altered water supply had no effect on other important aspects of the ecosystem.
Unable to display preview. Download preview PDF.
- Bowers J.E. and Turner R.M. 2002. The influence of climatic variability on local population dynamics of Cercidium microphyllum (foothill paloverde). Oecologia 130: 105–113.Google Scholar
- Carpenter A.T. and West N.E. 1987. Indifference of mountain big sagebrush growth to supplemental water and nitrogen. Journal of Range Management 40: 448–451.Google Scholar
- Looman J. and Best K.K. 1987. Budd's flora of the Canadian prairie provinces. Publication 1662, Agriculture Canada, Research Branch, Hull, Canada.Google Scholar
- Owensby C.E., Hyde R.W. and Anderson K.L. 1970. Effects of clipping and supplemental nitrogen and water on loamy upland bluestem range. Journal of Range Management 23: 341–346.Google Scholar
- Tilman D. 1990. Constraints and tradeoffs: toward a predictive theory of competition and succession. Oikos 58: 3–15.Google Scholar