02186nas a2200181   4500008004100000245008700041210006900128300001300197490000800210520154700218653002701765653001201792653002901804653002001833100002101853700001801874856011201892       1995                        eng d00aAmmonia volatilization during drought in perennial C4 grasses of tallgrass prairie0 aAmmonia volatilization during drought in perennial C4 grasses of  a361 -3650 v1013 aWe measured foliar NH3 volatilization as part of our study of the decrease (up to 40%) in shoot N concentration during drought in three perennial C4 grasses of tallgrass prairie. Volatilization of recently expanded leaves was quantified using cuvettes and acid traps for Spartina pectinata, Andropogon gerardii, and Schizachyrium scoparium, a mesic, intermediate, and xeric species, respectively. In general, volatilization decreased during drought, approaching zero as stomates closed, and increased with plant N status and drought tolerance. Prior to drought, NH3 volatilization was greater in xeric than mesic species (179 and 131 vs. 115 ng m-2 s-1 for individual leaves of S. scoparium and A. gerardii vs. Sp. pectinata). During a 2–3 week drought, whole-shoot volatile N losses can exceed 5% of total plant N in these species, accounting for 2–10% of the decrease in shoot percent N (again, xeric > mesic). Drought-induced N retranslocation of shoot N to roots and rhizomes is responsible for c. 63% of the decrease in percent N in Sp. pectinata, 28% in A. gerardii, and 8% in S. scoparium. The remainder of the decrease in percent N is attributable to growth dilution of existing shoot N, accounting for 34, 65, and 87% of the decrease in shoot percent N during drought in Sp. pectinata, A. gerardii, and S. scoparium, respectively. Thus, the relative importance of volatilization, retranslocation, and dilution in decreasing foliar percent N during drought in prairie grasses is species dependent and related to drought tolerance.10aAmmonia volatilization10aDrought10aNitrogen Prairie grasses10aRetranslocation1 aHeckathorn, S.A.1 aDeLucia, E.H.  uhttp://knz.lternet.edu/content/ammonia-volatilization-during-drought-perennial-c4-grasses-tallgrass-prairie