title: Nitrogen and carbon dynamics in C3and C4estuarine marsh plants grown under elevated CO2in situ.
abstract: Carbon dioxide concentrations were elevated in three estuarine communities for an entire growing season. Open top chambers were used to raise CO2concentrations ca. 336 ppm above ambient in monospecific communities of Scirpus olneyi (C3) and Spartina patens (C4), and a mixed community of S. olneyi, S. patens and Distichlis spicata (C4). Nitrogen and carbon concentration (% wt) of aboveground tissue was followed throughout growth and senescence. Green shoot %N was reduced and %C was unchanged under elevated CO2in S. olneyi. This resulted in a 20%-40% increase in tissue C/N ratio. There was no effect of CO2on either C4species. Maximum aboveground N (g/m2) was unchanged in S. olneyi, indicating that increased productivity under elevated CO2was dependent on reallocation of stored N. There was no change in the N recovery efficiency of S. olneyi in pure stand and a decrease in the mixed community. Litter C/N ratio was not affected by elevated CO2suggesting that decomposition and N mineralization rates will also remain unchanged. Continued growth responses to elevated CO2could, however, be limited by the ability of S. olneyi to increase the total aboveground N pool.
authors.affiliation: Smithsonian Environmental Research Center, Box 28, 21037, Edgewater, MD, USA.
authors.forename: P S
authors.initials: PS
authors.lastname: Curtis
authors.affiliation: Smithsonian Environmental Research Center, Box 28, 21037, Edgewater, MD, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Drake
authors.affiliation: Smithsonian Environmental Research Center, Box 28, 21037, Edgewater, MD, USA.
authors.forename: D F
authors.initials: DF
authors.lastname: Whigham
keywords: Carbon dioxide; Nitrogen; Scirpus; Spartina; Wetlands