Abstract
Long-term measurements of CO2 exchange between coastal wetlands and the atmosphere are necessary to improve our understanding of the role these ecosystems play in the global carbon cycle, and the response of these systems to environmental change. We conducted research to adapt and evaluate tower-based conditional sampling as a method for measuring net CO2 exchange (NCE) at the ecosystem scale on a continuous basis. With conditional sampling, NCE is determined from the product of the standard deviation of vertical wind velocity, the difference in CO2 concentration between updrafts and downdrafts in the constant flux portion of the boundary layer above the surface, and an empirical coefficient. We constructed a system that used a sonic anemometer to measure vertical wind velocity (w) and control a high-speed three-way valve that diverted air from updrafts and downdrafts into separate sample lines, depending on the direction ofw. an infrared gas analyzer was used to measure the concentration difference. The conditional sampling system was installed and tested in a marsh in the Nueces River Delta near Corpus Christi, Texas, as part of a long-term study of effects of freshwater inflow on CO2 flux. System accuracy was evaluated by comparing conditional sampling measurements of water vapor flux with independent estimates obtained with the Bowen ratio method. Average daily flux estimates for the two methods agreed to within 13%. Measurements showed that freshwater inflow due to flooding of the Nueces River increased NCE by increasing CO2 assimilation and decreasing CO2 efflux. Over a 65-d period, daily NCE varied from a maximum gain of 0.16 mol CO2 m−2 d−1 during flooding to a maximum loss of −0.14 mol CO2 m−2 d−1 when the marsh dried. Our study showed that conditional sampling was well suited for quantifying CO2 exchange in coastal wetlands on a diel, daily, and seasonal basis.
Similar content being viewed by others
Literature Cited
Baker, J. M., J. M. Norman, andW. L. Bland 1992. Field-scale application of flux measurement by conditional sampling.Agricultural and Forest Meteorology 62:31–52.
Baldocchi, D. 1994. A comparative study of mass and energy exchange rates over a closed C3 (wheat) and an open C4 (corn) crop: II. CO2 exchange and water use efficiency.Agricultural and Forest Meleorology 67:291–321.
Beverland, I. J., D. H. O’Neil, S. L. Scott, andJ. B. Moncrieff. 1996. Design, construction and operation of a flux measurement system using conditional sampling technique.Atmospheric Environment 18:3209–3220.
Businger, J. A. andS. P. Oncley. 1990. Flux measurement with conditional sampling.Journal of Atmospheric and Oceanic Technology 7:349–352.
Cellier, P. andA. Olioso. 1993. A simple system for automated long-term Bowen ratio measurement.Agricultural and Forest Meteorology 66:81–92.
Curtis, P. S., B. G. Drake, P. W. Leadley, W. J. Arp, andD. F. Whigham. 1989. Growth and senescence in plant communities exposed to elevated CO2 concentrations on an estuarine marsh.Oecologia 78:20–26.
Desjardins, R. L. 1977. Description and evaluation of a sensible heat flux sensor.Boundary-Layer Meteorology 11:147–154.
Drake, B. G. 1992. A field study of the effects of elevated CO2 on ecosystem processes in a Chesapeake Bay wetland.Australian Journal of Biology 40:579–595.
Drake, B. G. andP. W. Leadley. 1991. Canopy photosynthesis of crops and native plant communities exposed to long-term elevated CO2 treatment.Plant Cell and Environment 14:853–860.
Drake, B. G., P. W. Leadley, W. J. Arp, D. Nassiry, andP. S. Curtis. 1989. An open top chamber for field studies of elevated atmospheric CO2 concentration on saltmarsh vegetation.Functional Ecology 3:363–371.
Drake, B. G., M. S. Muehe, G. Peresta, M. A. Gonzàlez-Meler, andT. Matamala. 1996. Acclimation of photosynthesis, respiration and ecosystem carbon flux of a wetland on Chesapeake Bay, Maryland, to elevated atmospheric CO2 concentration.Plant and Soil 187:111–118.
Gifford, R. M., J. L. Lutze, andD. Barrett. 1996. Global atmospheric change effects on terrestrial carbon sequestration: Exploration with a global C- and N-cycle model (CQUESTN).Plant and Soil 187:369–387.
Goulden, J. L., J. W. Munger, S.-M. Fan, B. C. Daube, andS. C. Wofsy. 1996. Measurements of carbon sequestration by long-term eddy covariance: Methods and a critical evaluation of accuracy.Global Change Biology 2:169–182.
Ham, J. M. andA. K. Knapp. 1998. Fluxes of CO2, water vapor, and energy from a prairie ecosystem during the seasonal transition from carbon sink to carbon source.Agricultural and Forest Meteorology 89:1–14.
Happell, J. D. andJ. P. Chanton. 1993. Carbon remineralization in a north Florida swamp forest: Effects of water level on the pathways and rates of soil organic matter decomposition.Global Biogeochemical Cycles 7:475–490.
Houghton, R. A. andG. M. Woodwell. 1980. The Flax Pond ecosystem study: Exchanges of CO2 between a salt marsh and the atmosphere.Ecology 61:1434–1445.
Kaimal, J. C. andJ. J. Finnigan. 1994. Atmospheric Boundary Layer Flows: Their Structure and Measurement. Oxford University Press, New York.
Kim, J. andS. B. Verma. 1991. Modeling canopy photosynthesis: Scaling from a leaf to canopy in a temperate grassland ecosystem.Agricultural and Forest Meteorology 57:187–208.
Kimball, B. A. andR. D. Jackson. 1979. Soil heat flux, p. 211–229.In B. J. Barfield and J. F. Gerber (eds.), Modification of the Aerial Environment of Plants. American Society of Agricultural Engineers, St. Joseph, Michigan.
Koch, G. W. andH. A. Mooney. 1996. Carbon Dioxide and Terrestrial Ecosystems. Academic Press, New York.
McInnes, K. J., C. S. Campbell, andJ. L. Heilman. 1998. Separation and dispersion of conditionally sampled eddies through an intake tube.Agronomy Journal 90:845–850.
Moncrieff, J. B., Y. Malhi, andR. Luening 1996. The propagation of errors in long-term measurement of land-atmosphere fluxes of carbon and water.Global Change Biology 2::231–240.
Pattey, E., R. L. Desjardins, andP. Rochette. 1993. Accuracy of the relaxed eddy-accumulation technique, evaluated using CO2 flux measurements.Boundary-Layer Meteorology 66:341–355.
Pulliam, W. M. 1993. Carbon dioxide and methane exports from a southeastern floodplain swamp.Ecological Monographs 63:29–53.
Raymond, P. A., N. F. Caraco, andJ. J. Cole. 1997. Carbon dioxide concentration and atmospheric flux in the Hudson River.Estuaries 20:381–390.
Rochette, P., R. L. Desjardins, E. Pattey, andR. Lessard. 1995. Crop net carbon dioxide exchange and radiation use efficiency in soybean.Agronomy Journal 87:22–28.
Rochette, P., R. L. Desjardins, E. Pattey, andR. Lessard. 1996. Instantaneous measurement of radiation and water use efficiencies of a maize crop.Agronomy Journal 88:627–635.
Schmid, H. P. 1994. Source areas for scalars and scalar fluxes.Boundary-Layer Meteorology 67:293–318.
Smith, C. J., R. D. DeLaune, andW. H. Patrick, Jr. 1983. Carbon dioxide emission and carbon accumulation in coastal wetlands.Estuarine, Coastal and Shelf Science 17:21–29.
Sources of Unpublished Materials
Baker, J. T. Personal communication. United States Department of Agriculture-Agricultural Research Service, Beltsville Area Research Center-West, 10300 Baltimore Boulevard, Beltsville, Maryland 20705.
Dunton, K. H. Personal communication. Marine Science Institute, The University of Texas, 750 Channel View Drive, Port Aransas, Texas 78373.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Heilman, J.L., Cobos, D.R., Heinsch, F.A. et al. Tower-based conditional sampling for measuring ecosystem-scale carbon dioxide exchange in coastal wetlands. Estuaries 22, 584–591 (1999). https://doi.org/10.2307/1353046
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.2307/1353046