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Publication Type J
Authors Saunders, C. J., J. P. Megonigal and J. F. Reynolds
Title Comparison of belowground biomass in C-3- and C-4-dominated mixed communities in a Chesapeake Bay brackish marsh
Source Plant and Soil
Abstract Below ground biomass is a critical factor regulating ecosystem functions of coastal marshes, including soil organic matter (SOM) accumulation and the ability of these systems to keep pace with sea-level rise. Nevertheless, below ground biomass responses to environmental and vegetation changes have been given little emphasis marsh studies. Here we present a method using stable carbon isotopes and color to identify root and rhizomes of Schoenoplectus americanus (Pers.) Volk. ex Schinz and R. Keller (C-3) and Spartina patens (Ait.) Muhl. (C-4) occurring in C-3- and C-4-dominated communities in a Chesapeake Bay brackish marsh. The functional significance of the biomass classes we identified is underscored by differences in their chemistry, depth profiles, and variation in biomass and profiles relative to abiotic and biotic factors. C-3 rhizomes had the lowest concentrations of cellulose (29.19%) and lignin (14.43%) and the lowest C:N (46.97) and lignin:N (0.16) ratios. We distinguished two types of C-3 roots, and of these, the dark red C-3 roots had anomalously high C:N (195.35) and lignin:N (1.14) ratios, compared with other root and rhizome classes examined here and with previously published values. The C-4-dominated community had significantly greater below ground biomass (4119.1 g m(-2)) than the C-3-dominated community (3256.9 g m(-2)), due to greater total root biomass and a 3.6-fold higher C-3-root:rhizome ratio in the C-4-dominated community. C-3 rhizomes were distributed significantly shallower in the C-4-dominated community, while C-3 roots were significantly deeper. Variability in C3 rhizome depth distributions was explained primarily by C-4 biomass, and C-3 roots were explained primarily by water table height. Our results suggest that below ground biomass in this system is sensitive to slight variations in water table height (across an 8 cm range), and that the reduced overlap between C-3 and C-4 root profiles in the C-4-dominated community may account for the greater total root biomass observed in that community. Given that future elevated atmospheric CO2 and accelerated sea-level rise are likely to increase C-3 abundance in Atlantic and Gulf coast marshes, investigations that quantify how patterns of C-3 and C-4 below ground biomass respond to environmental and biological factors stand to improve our understanding of ecosystem-wide impacts of global changes on coastal wetlands.
Publication Date Feb
Year Published 2006
Volume 280
Issue 1-2
Beginning Page 305-322
Unique Article Identifier ISI:000235575900028
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