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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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Simulation Conference, 1996. Proceedings. Winter; 02/1996
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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).
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P Smith,
G.J. Nabuurs,
I. A. Janssens,
S. Reis,
G. Marland,
J.F. Soussana,
T.R. Christensen,
L. Heath,
M. Apps,
V. Alexeyev, [......],
Y Huang,
E. Jobbagy,
D. Murdiyarso,
J Ni,
A. Nobre,
C Peng,
A. Walcroft,
S Q Wang,
Y Pan, G.S. Zhou
[show abstract]
[hide abstract]
ABSTRACT: Humans utilise about 40% of the earth¿s net primary production (NPP) but the products of this NPP are often managed by different sectors, with timber and forest products managed by the forestry sector and food and fibre products from croplands and grasslands managed by the agricultural sector. Other significant anthropogenic impacts on the global carbon cycle include human utilization of fossil fuels and impacts on less intensively managed systems such as peatlands, wetlands and permafrost. A great deal of knowledge, expertise and data is available within each sector. We describe the contribution of sectoral carbon budgets to our understanding of the global carbon cycle. Whilst many sectors exhibit similarities for carbon budgeting, some key differences arise due to differences in goods and services provided, ecology, management practices used, land-management personnel responsible, policies affecting land management, data types and availability, and the drivers of change. We review the methods and data sources available for assessing sectoral carbon budgets, and describe some of key data limitations and uncertainties for each sector in different regions of the world. We identify the main gaps in our knowledge/data, show that coverage is better for the developed world for most sectors, and suggest how sectoral carbon budgets could be improved in the future. Research priorities include the development of shared protocols through site networks, a move to full carbon accounting within sectors, and the assessment of full greenhouse gas budgets
Climatic Change 88 (2008) 3-4.
