Dynamics of carbon sequestration in a coastal wetland using radiocarbon measurements

Coastal wetlands are sensitive to global climate change and may play an important role in the global carbon cycle. However, the dynamics of carbon (C) cycling in coastal wetlands and its response to sea level change associated with global warming is still poorly understood. In this study, we estimated the long‐term and short‐term rates of C accumulation, using C and C isotopic measurements of peat cores collected along a soil chronosequence, in a coastal wetland in north Florida. The long‐term C accumulation rates determined by examining the C inventory and the radioactive decay of radiocarbon as a function of depth in the peat cores decrease with time from ∼130 ± 9 g C/m2/yr over the last century to ∼13 ± 2 g C/m2/yr over the millennium timescale. The short‐term C accumulation rates estimated by examining the differences in the radiocarbon and C contents of the surfacial peat between archived (1985, 1988) and present (1996 and 1997) samples range from 42 to 193 g C/m2/yr in low marsh, from 18 to 184 g C/m2/yr in middle marsh, and from −50 to 181 g C/m2/yr in high marsh. The high end‐values of our estimated short‐term C accumulation rates are comparable to the estimated rates of C sequestration in coastal wetlands reported by Chmura et al. [2003] , but are significantly higher than our estimated long‐term rates in the marshes and are also much higher than the published rates of C sequestration in northern peatlands. The higher recent rates of C accumulation in coastal marshes, in comparison with the longer‐term rates, are due to slow but continuous decomposition of organic matter in the peat over time. However, other factors such as increased primary production in the coastal wetland over the last decades or century, due to a rise in mean sea level and/or CO2 and nitrogen fertilization effect, could also have contributed to the large difference between the recent and longer‐term rates. Our data indicate that salt marshes in this area have been and continue to be a sink for atmospheric carbon dioxide. Because of higher rates of C sequestration and lower CH4 emissions, coastal wetlands could be more valuable C sinks per unit area than other ecosystems in a warmer world.

[1]  Eric S. Menges,et al.  Patterns of Change in the Carbon Balance of Organic Soil-Wetlands of the Temperate Zone , 1986 .

[2]  David W. Kicklighter,et al.  Equilibrium Responses of Soil Carbon to Climate Change: Empirical and Process-Based Estimates , 1995 .

[3]  J. Barber.  Topics in photosynthesis vol 11 the photosystems structure function and molecular biology , 1992 .

[4]  L. R. Belyea,et al.  Temporal scale and the accumulation of peat in a Sphagnum bog , 1996 .

[5]  R. B. Jackson,et al.  The fate of carbon in grasslands under carbon dioxide enrichment , 1997, Nature.

[6]  J. N. Hutchinson.  The Record of Peat Wastage in the East Anglian Fenlands at Holme Post, 1848-1978 A.D. , 1980 .

[7]  W. Broecker,et al.  The Effect of Changing Land Use on Soil Radiocarbon , 1993, Science.

[8]  G. Burr,et al.  Converting AMS Data to Radiocarbon Values: Considerations and Conventions , 2001, Radiocarbon.

[9]  R. Delaune,et al.  Sedimentation rates determined by 137Cs dating in a rapidly accreting salt marsh , 1978, Nature.

[10]  R. Amundson,et al.  The impact of land use change on C turnover in soils , 1999 .

[11]  J. Barber.  The photosystems: structure, function and molecular biology. , 1992 .

[12]  Y. Hsieh.  Assessing aboveground net primary production of vascular plants in marshes , 1996 .

[13]  R. Knowles,et al.  METHANE AND CARBON DIOXIDE EVOLUTION FROM SUBARCTIC FENS , 1987 .

[14]  E. Gorham.  Northern Peatlands: Role in the Carbon Cycle and Probable Responses to Climatic Warming. , 1991, Ecological applications : a publication of the Ecological Society of America.

[15]  Y. Hsieh,et al.  Uncertainties and novel prospects in the study of the soil carbon dynamics. , 2002, Chemosphere.

[16]  E. B. Rastetter,et al.  Changes in C storage by terrestrial ecosystems: How C-N interactions restrict responses to CO2 and temperature , 1992 .

[17]  D. Donahue,et al.  Isotope-Ratio and Background Corrections for Accelerator Mass Spectrometry Radiocarbon Measurements , 1990, Radiocarbon.

[18]  W. Broecker,et al.  A strategy for estimating the impact of CO2 fertilization on soil carbon storage , 1993 .

[19]  R. Mark,et al.  Dynamics of Soil Carbon During Deglaciation of the Laurentide Ice Sheet , 1992, Science.

[20]  A. Cohen.  Petrography and Paleoecology of Holocene Peats from the Okefenokee Swamp-Marsh Complex of Georgia , 1974 .

[21]  Susan E. Trumbore,et al.  AGE OF SOIL ORGANIC MATTER AND SOIL RESPIRATION: RADIOCARBON CONSTRAINTS ON BELOWGROUND C DYNAMICS , 2000 .

[22]  James S. Clark,et al.  Terrestrial biotic responses to environmental change and feedbacks to climate , 1996 .

[23]  B. J. O'brien,et al.  Movement and turnover of soil organic matter as indicated by carbon isotope measurements , 1978 .

[24]  J. Southon,et al.  AMS 14C Measurements of Fractionated Soil Organic Matter: An Approach to Deciphering the Soil Carbon Cycle , 1989, Radiocarbon.

[25]  D. Cahoon,et al.  Accretion and canal impacts in a rapidly subsiding wetland II. Feldspar marker horizon technique , 1989 .

[26]  R. Tate.  Microbial Oxidation of Organic Matter of Histosols , 1980 .

[27]  M. Stuiver,et al.  Discussion: Reporting of 14 C Data , 1977 .

[28]  W. Schlesinger.  Evidence from chronosequence studies for a low carbon-storage potential of soils , 1990, Nature.

[29]  D. Cahoon,et al.  Global carbon sequestration in tidal, saline wetland soils , 2003 .

[30]  Patrick M. Crill,et al.  Carbon cycling in boreal wetlands: A comparison of three approaches , 1999 .

[31]  A. W. Damman.  Distribution and movement of elements in ombrotrophic peat , 1978 .

[32]  P. V. Sundareshwar,et al.  RESPONSES OF COASTAL WETLANDS TO RISING SEA LEVEL , 2002 .

[33]  R. Amundson,et al.  Carbon Cycling in Terrestrial Environments , 1998 .

[34]  P. Martikainen,et al.  CO2 fluxes from peat in boreal mires under varying temperature and moisture conditions. , 1996 .

[35]  J. Chanton,et al.  Radiocarbon evidence for the substrates supporting methane formation within northern Minnesota peatlands , 1995 .

[36]  R. S. Clymo,et al.  The Limits to Peat Bog Growth , 1984 .

[37]  S. Trumbore.  Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements , 1993 .

[38]  W. F. Tanner.  Florida Coastal Classification , 1960 .

[39]  Jeffrey P. Chanton,et al.  Greenhouse carbon balance of wetlands: methane emission versus carbon sequestration , 2001 .

[40]  Tim R. Moore,et al.  THE INFLUENCE OF WATER TABLE LEVELS ON METHANE AND CARBON DIOXIDE EMISSIONS FROM PEATLAND SOILS , 1989 .

[41]  Joyce E. Penner,et al.  Spatial and Temporal Patterns in Terrestrial Carbon Storage Due to Deposition of Fossil Fuel Nitrogen , 1996 .

[42]  A. Francez,et al.  Peat accumulation and peat decomposition after human disturbance in French and finnish mires , 1995 .

[43]  E. H. Stewart,et al.  Radiocarbon Chronology of the Florida Everglades Peat , 1969 .

[44]  P. Glaser.  Raised bogs in eastern North America - regional controls for species richness and floristic assemblages , 1992 .

[45]  R. Amundson,et al.  Radiocarbon Dating of Soil Organic Matter , 1996, Quaternary Research.

[46]  Jack J. Middelburg,et al.  Organic carbon isotope systematics of coastal marshes , 1997 .

[47]  D. Whitehead.  Late-Pleistocene Vegetational Changes in Northeastern North Carolina , 1981 .

[48]  J. Coleman,et al.  Elevated CO2 increases productivity and invasive species success in an arid ecosystem , 2000, Nature.

[49]  X. Niu,et al.  Seasonal and altitudinal variation in decomposition of soil organic matter inferred from radiocarbon measurements of soil CO2 flux , 2000 .

[50]  W. D. Billings.  CARBON BALANCE OF ALASKAN TUNDRA AND TAIGA ECOSYSTEMS: PAST, PRESENT AND FUTURE , 1987 .

[51]  R. Amundson,et al.  Rapid Exchange Between Soil Carbon and Atmospheric Carbon Dioxide Driven by Temperature Change , 1996, Science.

[52]  E. Davidson,et al.  Belowground cycling of carbon in forests and pastures of eastern Amazonia , 1995 .

[53]  G. Chmura,et al.  Variation in Surface Sediment Deposition on Salt Marshes in the Bay of Fundy , 2001 .

[54]  Yonghoon Choi,et al.  Vegetation succession and carbon sequestration in a coastal wetland in northwest Florida: Evidence from carbon isotopes , 2001 .

[55]  D. Schell,et al.  Carbon-13 and Carbon-14 Abundances in Alaskan Aquatic Organisms: Delayed Production from Peat in Arctic Food Webs , 1983, Science.

[56]  T. Vinson,et al.  Carbon pools and accumulation in peatlands of the former Soviet Union , 1995 .

[57]  S. Trumbore,et al.  Comparison of Fractionation Methods for Soil Organic Matter 14C Analysis , 1996, Radiocarbon.

[58]  D. Schindler,et al.  The biosphere as an increasing sink for atmospheric carbon: Estimates from increased nitrogen depostion , 1993 .