01969nas a2200193   4500008004100000245008300041210006900124300001300193490000800206520136600214653001901580653002101599653002001620653001901640653001701659100001701676700001601693856006601709       2014                        eng d00aContrasting sensitivities of two dominant C4 grasses to heat waves and drought0 aContrasting sensitivities of two dominant C4 grasses to heat wav  a721 -7310 v2153 a<p>Heat waves and droughts are predicted to increase in frequency and intensity with climate change. However, we lack a mechanistic understanding of the independent and interactive effects of severe heat and water stress for most ecosystems. In a mesic tallgrass prairie ecosystem, we used a factorial experimental approach to assess ecophysiological and productivity responses of two dominant C4 grasses, Andropogon gerardii and Sorghastrum nutans, to a season-long drought and a mid-summer heat wave at four intensities. We hypothesized that drought would have greater impacts than heat waves, that combined effects would be greater than either factor alone, and that the dominant grasses would differ in their responses to heat and water heat stress. We detected significant reductions in photosynthesis, leaf water potential, and productivity with drought but few direct responses to the heat waves. Surprisingly, there was no additive effect of heat and water stress on any plant response. However, S. nutans was more sensitive than A. gerardii to drought. In this grassland, water stress will likely dominate photosynthetic and productivity responses caused by discrete drought and heat wave events, rather than direct or additive effects of heat stress, with differential sensitivity in these grasses altering future ecosystem structure and function.</p>10aClimate change10aClimate extremes10aMesic grassland10aphotosynthesis10aproductivity1 aHoover, D.L.1 aSmith, M.D.  uhttps://link.springer.com/article/10.1007%2Fs11258-014-0345-8