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Tagir G. Gilmanov,
L. Aires,
Z. Barcza,
V. S. Baron,
L. Belelli Marchesini,
J. Beringer,
D. Billesbach,
D. Bonal,
J. Bradford,
E. Ceschia, [......],
K. Pinter,
C. Pio,
M. Reichstein,
M. J. Sanz,
R. Scott,
J. F. Soussana,
P. C. Stoy,
T. Svejcar,
Z. Tuba,
Guangsheng Zhou
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Tagir G. Gilmanov,
L. Aires,
Z. Barcza,
V. S. Baron,
L. Belelli Marchesini,
J. Beringer,
D. Billesbach,
D. Bonal,
J. Bradford,
E. Ceschia, [......],
K. Pinter,
C. Pio,
M. Reichstein,
M. J. Sanz,
R. Scott,
J. F. Soussana,
P. C. Stoy,
T. Svejcar,
Z. Tuba,
Guangsheng Zhou
[show abstract]
[hide abstract]
ABSTRACT: Grasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO2 exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO2 fluxes in a sagebrush-steppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167–183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grünwald, K. Havránková, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J. M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11:1424–1439). Maximum values of the quantum yield (α = 75 mmol · mol−1), photosynthetic capacity (Amax = 3.4 mg CO2 · m−2 · s−1), gross photosynthesis (Pg,max = 116 g CO2 · m−2 · d−1), and ecological light-use efficiency (ϵecol = 59 mmol · mol−1) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO2. Maximum values of gross primary production (8 600 g CO2 · m−2 · yr−1), total ecosystem respiration (7 900 g CO2 · m−2 · yr−1), and net CO2 exchange (2 400 g CO2 · m−2 · yr−1) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO2, with mean net uptake of 700 g CO2 · m−2 · yr−1 for intensive grasslands and 933 g CO2 · m−2 · d−1 for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO2, this does not imply that they are necessarily increasing their carbon stock.
Rangeland Ecology & Management 01/2010; 63. · 1.46 Impact Factor
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T. G. Gilmanov,
L. Aires,
Z. Barcza,
V. S. Baron,
L. Belelli,
J. Beringer,
D. Billesbach,
D. Bonal,
J. Bradford,
E. Ceschia, [......],
K. Pinter,
C. Pio,
M. Reichstein,
M. J. Sanz,
R. Scott,
J. F. Soussana,
P. C. Stoy,
T. Svejcar,
Z. Tuba,
G. S. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Grasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO2 exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO2 fluxes in a sagebrushsteppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167-183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grunwald, K. Havrankova, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J.M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11: 1.424-1439). Maximum values of the quantum yield (alpha = 75 mmol.mol(-1)), photosynthetic capacity (A(max) = 3.4 mg CO2 . m(-2).s-1), gross photosynthesis (P-g,P-max = 1.16 g CO2 . m(-2).d(-1)), and ecological light-use efficiency (epsilon(ecol) = 59 mmol . mol(-1)) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO2. Maximum values of gross primary production (8 600 g CO2 . m(-2).yr(-1)), total ecosystem respiration (7 900 g CO2 . m(-2).yr(-1)), and net CO2 exchange (2 400 g CO2 . m(-2).yr(-1)) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO2, with mean net uptake of 700 g CO2 . m(-2).yr(-1) for intensive grasslands and 933 g CO2 . m(-2).d(-1) for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO2, this does not imply that they are necessarily increasing their carbon stock.
Rangeland Ecology & Management. 01/2010; 63(1):16-39.
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[show abstract]
[hide abstract]
ABSTRACT: We present a synthesis of long-term measurements of CO2 exchange in 2 US Intermountain West sagebrush-steppe ecosystems. The locations near Burns, Oregon (1995-2001), and Dubois, Idaho (1996-2001), are part of the AgriFlux Network of the Agricultural Research Service, United States Department of Agriculture. Measurements of net ecosystem CO2 exchange (Fc) during the growing season were continuously recorded at flux towers using the Bowen ratio-energy balance technique. Data were partitioned into gross primary productivity (Pg) and ecosystem respiration (Re) using the light-response function method. Wintertime fluxes were measured during 1999/2000 and 2000/2001 and used to model fluxes in other winters. Comparison of daytime respiration derived from light-response analysis with nighttime tower measurements showed close correlation, with daytime respiration being on the average higher than nighttime respiration. Maxima of Pg and Re at Burns were both 20 g CO2·m-2·d-1 in 1998. Maxima of Pg and Re at Dubois were 37 and 35 g CO2·m-2·d-1, respectively, in 1997. Mean annual gross primary production at Burns was 1111 (range 475-1715) g CO2·m-2·y-1 or about 30% lower than that at Dubois (1602, range 963-2162 g CO2·m-2·y-1). Across the years, both ecosystems were net sinks for atmospheric CO2 with a mean net ecosystem CO2 exchange of 82 g CO2·m-2·y-1 at Burns and 253 g CO2·m-2·y-1 at Dubois, but on a yearly basis either site could be a C sink or source, mostly depending on precipitation timing and amount. Total annual precipitation is not a good predictor of carbon sequestration across sites. Our results suggest that Fc should be partitioned into Pg and Re components to allow prediction of seasonal and yearly dynamics of CO2 fluxes.
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T. Gilmanov,
L. Aires,
Z. Barcza,
V. S. Baron,
L. Belelli,
J Beringer,
D. Billesbach,
D. Bonal,
J. Bradford,
E. Ceschia, [......],
K. Pinter,
C. Pio,
M. Reichstein,
M. J. Sanz,
R. Scott,
J. Soussana,
P. Stoy,
T. Svejcar,
Z. Tuba,
G. S. Zhou
Rangeland Ecology & Management, v.63, 16-39 (2010).
