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GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 17, NO. 2, 1071, doi:10.1029/2002GB002023, 2003

Gross primary production and light response parameters of four Southern Plains ecosystems estimated using long-term CO₂-flux tower measurements

Tagir G. Gilmanov

Department of Biology and Microbiology, South Dakota State University, Brookings, South Dakota, USA

Shashi B. Verma

School of Natural Resource Sciences, University of Nebraska at Lincoln, Lincoln, Nebraska, USA

Phillip L. Sims

Southern Plains Range Research Station, USDA-Agricultural Research Service, Woodward, Oklahoma, USA

Tilden P. Meyers

Atmospheric Turbulence and Diffusion Division, NOAA/ARL, Oak Ridge, Tennessee, USA

James A. Bradford

Southern Plains Range Research Station, USDA-Agricultural Research Service, Woodward, Oklahoma, USA

George G. Burba

School of Natural Resource Sciences, University of Nebraska at Lincoln, Lincoln, Nebraska, USA

Andrew E. Suyker

School of Natural Resource Sciences, University of Nebraska at Lincoln, Lincoln, Nebraska, USA

Abstract

Gross primary production (GPP) is one of the most important characteristics of an ecosystem. At present, no empirically based method to estimate GPP is available, other than measurements of net CO₂ exchange and calculations of respiration. Data sets from continuous CO₂ flux measurements in a number of ecosystems (Ameriflux, AgriFlux, etc.) for the first time provide an opportunity to obtain empirically based estimates of GPP. In this paper, using the results of CO₂ flux tower measurements during the 1997 season at four sites in Oklahoma (tallgrass prairie, mixed prairie, pasture, and winter wheat crop), we describe a method to evaluate the average daytime rate of ecosystem respiration, R_d, by estimation of the respiration term of the nonrectangular hyperbolic model of the ecosystem-scale light-response curve. Comparison of these predicted daytime respiration rates with directly measured corresponding nighttime values, R_n, after appropriate length of the night and temperature correction, demonstrated close linear relationship, with 0.82 ≤ R² ≤ 0.98 for weekly averaged fluxes. Daily gross primary productivity, P_g, can be calculated as P_g = P_d + R_d, where P_d is the daytime integral of the net ecosystem CO₂ exchange, obtained directly from measurements. Annual GPP for the sites, obtained as the sum of P_g over the whole period with P_g > 0 were: tallgrass prairie, 5223 g CO₂ m⁻²; winter wheat, 2853 g CO₂ m⁻²; mixed prairie, 3037 g CO₂ m⁻²; and pasture, 2333 g CO₂ m⁻². These values are in agreement with published GPP estimates for nonforest terrestrial ecosystems.

Received 9 December 2002; accepted 5 May 2003; published 20 June 2003.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1610 Global Change: Atmosphere (0315, 0325); 1615 Global Change: Biogeochemical processes (4805); 3210 Mathematical Geophysics: Modeling.

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Citation: Gilmanov, T. G., S. B. Verma, P. L. Sims, T. P. Meyers, J. A. Bradford, G. G. Burba, and A. E. Suyker (2003), Gross primary production and light response parameters of four Southern Plains ecosystems estimated using long-term CO₂-flux tower measurements, Global Biogeochem. Cycles, 17(2), 1071, doi:10.1029/2002GB002023.

Copyright 2003 by the American Geophysical Union.