Physiology of dominant grasses in prairie restoration: The effect of population seed source on plant performance

Selected genotypes (i.e. cultivars) of dominant C₄ grasses are commonly used in tallgrass prairie restorations despite their potential dissimilarity to local seed sources. Because dominant species play a crucial role in community structure and ecosystem function, population source may have consequences for diversity, productivity, and ultimately restoration success. A greenhouse experiment was conducted to compare the physiology of cultivar and non-cultivar population sources of dominant prairie grasses Andropogon gerardii, Schizachyrium scoparium, and Sorghastrum nutans. Net photosynthesis (A_net) was measured 3 times throughout the growing season. Above, below and total net primary production (ANPP, BNPP, NPP) were measured prior to senescence. A_net was similar between population sources in the early and middle part of the growing season, but was higher in cultivars of A. gerardii and S. nutans late in the growing season (P<0.05). We found evidence for intraspecific variation in ANPP (P = 0.001) and total NPP (P = 0.05) in S. nutans and S. scoparium, but no difference in BNPP or root:shoot ratios between cultivars and non-cultivars. Patterns of ANPP did not reflect patterns of A_net because A_net varied most at peak biomass. Our results demonstrate variation in seasonal carbon assimilation rates due to differences in phenology between cultivar and non-cultivar prairie grasses of the same species. Population source selection may act as a potential filter on community and ecosystem assembly through intraspecific variation in physiology and production of dominant species used in restoration.