01831nas a2200133   4500008004100000245014300041210006900184300001300253490000800266520125600274100001901530700002001549856012801569       2001                        eng d00aResponses of the co-dominant grassland species Andropogon gerardii and Sorghastrum nutans to long-term manipulations of nitrogen and water0 aResponses of the codominant grassland species Andropogon gerardi  a159 -1670 v1453 aThe availability and distribution of essential resources such as water and nitrogen are changing on a global scale and it is important to determine the effects of such alterations on dominant and subdominant species in ecosystems. We examined the effects of long-term additions of water and nitrogen on leaf-level ecophysiological characteristics of the tallgrass prairie codominants Andropogon gerardii (big bluestem) and Sorghastrum nutans (Indian grass). Both species responded to irrigation with increased water potentials and to fertilization with decreased water potentials. Only in S. nutans, however, were net photosynthesis and stomatal conductance greater in response to both water and nitrogen addition. In contrast, A. gerardii, which currently is more abundant than S. nutans, was relatively unresponsive to resource manipulations. If net photosynthesis is positively related to plant productivity, as has been shown for tallgrass prairie species, the differential photosynthetic responses of these two grasses suggests that their patterns of abundance may change in the future if resource availability is altered. These results are also inconsistent with the historical assumption that these two grasses are “ecological equivalents.”1 aSilletti, A.M.1 aKnapp, Alan, K.  uhttp://knz.lternet.edu/content/responses-co-dominant-grassland-species-andropogon-gerardii-and-sorghastrum-nutans-long-term