Measurements of CO2 exchange over a woodland savanna (Cerrado Sensu stricto) in southeast Brasil

Rocha, Humberto R. da; Freitas, Helber C.; Rosolem, Rafael; Juárez, Robinson I.N.; Tannus, Rafael N.; Ligo, Marcos A.; Cabral, Osvaldo M. R.; Dias, Maria A.F. Silva

doi:10.1590/S1676-06032002000100009

Abstracts

The technique of eddy correlation was used to measure the net ecosystem exchange over a woodland savanna (Cerrado Sensu stricto) site (Gleba Pé de Gigante) in southeast Brazil. The data set included measurements of climatological variables and soil respiration using static soil chambers. Data were collected during the period from 10 October 2000 to 30 March 2002. Measured soil respiration showed average values of 4.8 molCO2 m-2s-1 year round. Its seasonal differences varied from 2 to 8 molCO2 m-2s-1 (Q10 = 4.9) during the dry (April to August) and wet season, respectively, and was concurrent with soil temperature and moisture variability. The net ecosystem CO2 flux (NEE) variability is controlled by solar radiation, temperature and air humidity on diel course. Seasonally, soil moisture plays a strong role by inducing litterfall, reducing canopy photosynthetic activity and soil respiration. The net sign of NEE is negative (sink) in the wet season and early dry season, with rates around -25 kgC ha-1day-1, and values as low as 40 kgC ha-1day-1. NEE was positive (source) during most of the dry season, and changed into negative at the onset of rainy season. At critical times of soil moisture stress during the late dry season, the ecosystem experienced photosynthesis during daytime, although the net sign is positive (emission). Concurrent with dry season, the values appeared progressively positive from 5 to as much as 50 kgC ha-1day-1. The annual NEE sum appeared to be nearly in balance, or more exactly a small sink, equal to 0.1 0.3 tC ha-1yr-1, which we regard possibly as a realistic one, giving the constraining conditions imposed to the turbulent flux calculation, and favourable hypothesis of succession stages, climatic variability and CO2 fertilization.

Cerrado; savanna; photosynthesis; soil respiration; carbon sequestration; eddy correlation

A técnica de correlação dos vórtices turbulentos (eddy correlation) foi utilizada para se estimar a produtividade líquida do ecossistema (PLE) em uma área de Cerrado Sensu stricto, no sítio experimental da Gleba Pé de Gigante, no sudeste do Brasil. O conjunto de dados coletados incluiu também medidas de variáveis climatológicas e de respiração do solo com câmaras estáticas, no período de 10 de Outubro de 1999 a 30 de Março de 2002. A respiração do solo média anual foi de 4.8 molCO2m-2s-1, com diferenças sazonais que variaram entre 2 a 8 molCO2 m-2s-1 durante a estação seca (Abril a Agosto) e na estação chuvosa, respectivamente, por um padrão de sensível correlação com a temperatura (Q10=4.9) e umidade do solo. Com base nos fluxos atmosféricos de CO2, a PLE mostrou uma variabilidade no ciclo diurno grandemente controlada pela radiação solar, umidade e temperatura do ar. Na escala sazonal, a umidade do solo foi uma variável de alta correlação com a PLE, que aparentemente induziu a queda de folhedo, redução da atividade fotossintética e da respiração do solo. O sinal da PLE foi negativo (sumidouro) na estação chuvosa e no início da estação seca, com taxas de -25 kgCha-1dia-1, e máximos de até 40 kgCha-1dia-1. Na estação seca o sinal foi positivo (emissão), o que foi revertido logo no início das chuvas. No fim da estação seca, em dias de grande estresse hídrico, ainda observou-se a resposta da fotossíntese na escala do ecossistema, mesmo tendo sido positiva a PLE. Paralelamente ao decorrer da estação seca, a PLE progressivamente aumentou de 5 até 50 kgCha-1dia-1. A soma annual da PLE mostrou-se aproximadamente balanceada, tendo sido no entanto, sob um viés de maior precisão, um pequeno mas significativo sumidouro de 0.1 0.3 tCha-1ano-1. Consideramos a hipótese de um pequeno sumidouro como possivelmente realista, dadas às restringentes correções impostas no cálculo dos fluxos turbulentos, e algumas hipóteses favoráveis de sucessão de estágios do Cerrado, fertilização de CO2 atmosférico e variabilidade climática.

Cerrado; savana; fotossíntese; respiração; sequestro de carbono; correlação dos vórtices turbulentos

ARTICLES

Measurements of CO₂ exchange over a woodland savanna (Cerrado Sensu stricto) in southeast Brasil

Humberto R. da Rocha^I; Helber C. Freitas^I; Rafael Rosolem^I; Robinson I.N. Juárez^I; Rafael N. Tannus^I; Marcos A. Ligo^II; Osvaldo M. R. Cabral^II; Maria A. F. Silva Dias^I

^IDepartamento de Ciências Atmosféricas, IAG/Universidade de São Paulo

^IIEMBRAPA Meio Ambiente

ABSTRACT

The technique of eddy correlation was used to measure the net ecosystem exchange over a woodland savanna (Cerrado Sensu stricto) site (Gleba Pé de Gigante) in southeast Brazil. The data set included measurements of climatological variables and soil respiration using static soil chambers. Data were collected during the period from 10 October 2000 to 30 March 2002. Measured soil respiration showed average values of 4.8 molCO₂ m^-2s^-1 year round. Its seasonal differences varied from 2 to 8 molCO₂ m^-2s^-1 (Q₁₀ = 4.9) during the dry (April to August) and wet season, respectively, and was concurrent with soil temperature and moisture variability. The net ecosystem CO₂ flux (NEE) variability is controlled by solar radiation, temperature and air humidity on diel course. Seasonally, soil moisture plays a strong role by inducing litterfall, reducing canopy photosynthetic activity and soil respiration. The net sign of NEE is negative (sink) in the wet season and early dry season, with rates around -25 kgC ha^-1day^-1, and values as low as 40 kgC ha^-1day^-1. NEE was positive (source) during most of the dry season, and changed into negative at the onset of rainy season. At critical times of soil moisture stress during the late dry season, the ecosystem experienced photosynthesis during daytime, although the net sign is positive (emission). Concurrent with dry season, the values appeared progressively positive from 5 to as much as 50 kgC ha^-1day^-1. The annual NEE sum appeared to be nearly in balance, or more exactly a small sink, equal to 0.1 0.3 tC ha^-1yr^-1, which we regard possibly as a realistic one, giving the constraining conditions imposed to the turbulent flux calculation, and favourable hypothesis of succession stages, climatic variability and CO₂ fertilization.

Key Words: Cerrado, savanna, photosynthesis, soil respiration, carbon sequestration, eddy correlation.

RESUMO

A técnica de correlação dos vórtices turbulentos (eddy correlation) foi utilizada para se estimar a produtividade líquida do ecossistema (PLE) em uma área de Cerrado Sensu stricto, no sítio experimental da Gleba Pé de Gigante, no sudeste do Brasil. O conjunto de dados coletados incluiu também medidas de variáveis climatológicas e de respiração do solo com câmaras estáticas, no período de 10 de Outubro de 1999 a 30 de Março de 2002. A respiração do solo média anual foi de 4.8 molCO₂m^-2s^-1, com diferenças sazonais que variaram entre 2 a 8 molCO₂ m^-2s^-1durante a estação seca (Abril a Agosto) e na estação chuvosa, respectivamente, por um padrão de sensível correlação com a temperatura (Q₁₀=4.9) e umidade do solo. Com base nos fluxos atmosféricos de CO₂, a PLE mostrou uma variabilidade no ciclo diurno grandemente controlada pela radiação solar, umidade e temperatura do ar. Na escala sazonal, a umidade do solo foi uma variável de alta correlação com a PLE, que aparentemente induziu a queda de folhedo, redução da atividade fotossintética e da respiração do solo. O sinal da PLE foi negativo (sumidouro) na estação chuvosa e no início da estação seca, com taxas de -25 kgCha^-1dia^-1, e máximos de até 40 kgCha^-1dia^-1. Na estação seca o sinal foi positivo (emissão), o que foi revertido logo no início das chuvas. No fim da estação seca, em dias de grande estresse hídrico, ainda observou-se a resposta da fotossíntese na escala do ecossistema, mesmo tendo sido positiva a PLE. Paralelamente ao decorrer da estação seca, a PLE progressivamente aumentou de 5 até 50 kgCha^-1dia^-1. A soma annual da PLE mostrou-se aproximadamente balanceada, tendo sido no entanto, sob um viés de maior precisão, um pequeno mas significativo sumidouro de 0.1 0.3 tCha^-1ano^-1. Consideramos a hipótese de um pequeno sumidouro como possivelmente realista, dadas às restringentes correções impostas no cálculo dos fluxos turbulentos, e algumas hipóteses favoráveis de sucessão de estágios do Cerrado, fertilização de CO₂ atmosférico e variabilidade climática.

Palavras-chave: Palavras chave: Cerrado, savana, fotossíntese, respiração, sequestro de carbono, correlação dos vórtices turbulentos.

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Texto completo disponível apenas em PDF.

5. Acknowledgements

We acknowledge the Fundação de Amparo à Pesquisa e Desenvolvimento do Estado de São Paulo (FAPESP) (Projeto 99/11215-9) and the Conselho Nacional de Pesquisa e Desenvolvimento (CNPq) ( Projetos 469492/2000 and 000522082/97) for funding the activities of this work. We thank the collaboration with the Instituto Florestal/SMA/SP to carry on the logistics and use of facilities at the Vassununga State Park, and particularly Eng. Everton Ribeiro (Vassununga State Park chief) for conducting the local support. We would like also to thank Humberto Mesquita and Marisa Bittencourt (IB/USP) for helping on the site selection and site information.

6. References

Date Received 03-01-2002

Revised 06-20-2002

Accepted 06-30 2002

A n h u f , D . , T . M o t z e r , R . Rollenbeck,B.Schroder,J.Szarzinsky 1999. Water budget of the Surumoni crane site (Venezuela). Selbyana, 20:1, 179-185.
Batalha, M.A. 1997. Análise da vegetação da ARIE Cerrado Pé-de-Gigante. Dissertação de Mestrado. Instituto de Biociências / USP.
Castro E. A. and Kauffman J. B., 1998. Ecosystem struture in the Brazilian Cerrado: a vegetation gradient of aboveground biomass, root mass, and consumption by fire. Journal of Tropical Ecology, 14, 263-283
Collatz, G.J., J. T. Ball, C. Grivet, J.A.Berry, 1991. Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: a model that includes a laminar boundary layer. Agricultural and Forest Meteorology, 54: 107-136.
Collatz, G.J., M.Ribas-Carbo, J.A.Berry, 1992. Coupled photosynthesis-stomatal conductance model for leaves of C4 plants. Aust. J. Plant Physiol., 19: 519-538.
Coutinho, L.M. , 1978. O Conceito de Cerrado. Revista Brasileira de Botânica, 1, 17-23.
Delitti W. B. C. , Pausas J. G. , Burger D. M., 2001. Belowground biomass seasonal variation in two Neotropical savannahs ( Brazilian Cerrados) with different fire histories. Ann. For. Sci, 58, 713-721.
Davidson, E. A, L. V. Verchot, J. H. Cattanio, I. L. Ackerman, J. E. M. Carvalho. Effects of soil water content on soil respiration in forests and cattle pastures of eastern Amazonia. Biogeochemistry, 48: 53-69, 2000
Eiten, G. 1972. The cerrado vegetation of Brazil. The Botanical Review, 38, 201-341.
Finnigan, J.J., R. Clements, Y. Malhi, R. Leuning, and H.A. Clough, 2002. A re-evaluation of long-term flux measurement, Submitted to Boundary Layer Meteorology.
Goulden, M.L., J.W. Munger, S.-M. Fan, B.C. Daube, and S. 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.
Goulden, M. L., S.D. Miller, M.C. Menton, H.R. da Rocha, H.C. Freitas. 2002 Physiological Controls on Tropical Forest CO2 Exchange. Submitted to Ecological Applications.
Grace, J., Y. Malhi, J. Lloyd, J. McIntyre, A.C. Miranda, P. Meir, and H.S. Miranda. 1996. The use of eddy covariance to infer the net carbon dioxide uptake of Brazilian rain forest. Global Change Biology 2:208-217
LBA, 1996. The Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), Concise Experimental Plan. Compiled by the LBA Science Planning Group. Doccument available at CPTEC/INPE, Cachoeira Paulista, SP, Brazil.
M a l h i , Y . , A . D . N o b r e , J.Grace,B.Kruijt,M.G.P.Pereira,A.Culf,S.Scott. Carbon dioxide transfer over a central amazonian rain forest. Journal of Geophysical Research, 103, D24:31593-31612, 1998
Meir, P., J. Grace, A. Miranda and J. Lloyd. Soil respiration in a rainforest in Amazonia and in Cerrado in Central Brazil. In Amazonian Deforestation and Climate, eds J.Gash, C. Nobre, J. Roberts and R. Victoria, p. 319-329, 1996.
Miller, S.D., M.L. Goulden, M.C. Menton, H.R. da Rocha, and H.C. Freitas. 2002. Annual CO2 Exchange by a tropical Forest. (Journal of Ecological Applications, in press)
Miranda, A.C., H.S. Miranda, J. Lloyd, J. Grace, J.A., Francey,J.R., McIntyre, P. Meir, P. Riggan, R. Lockwood, J. Brass, 1997. Fluxes of carbon, water and energy over Brazilian cerrado: an analysis using eddy covariance and stable isotopes. Plant, Cell and Environment, 20: 315-328.
Mittermeyer,R.A.,N.Myers,C.G.Mittermeyer, 2000. Hotspots: earth's biologically richest and most endangered terrestrial ecoregions. Mexico City, CEMEX.
Moncrieff, J.B., J.M. Massheder, H. de Bruin, J.Elbers, T. Friborg, B. Heusinkveld, P. Kabat, S. Scott, H. Soegaard and A. Verhof 1997. A system to measure surface fluxes of momentum, sensible heat, water vapour and carbon dioxide. Journal of Hydrology, 189, 589-611.
Parkinson, K.J., 1981. An improved method for measuring soil respiration in the field. Journal of Applied Ecology, 18, 221-228.
Pivelo, V. R. and L.M. Coutinho, 1996. A qualitative successional model to assist in the management of Brazilian cerrados . Forest Ecology and Management, 87, 127-138
Ratter, J.A. 1992. Transitions between cerrado and forest vegetation in Brazil. In Nature and dynamics of forest-savanna boundaries, (eds P.A. Furley, J. Proctor and J.A. Ratter), p. 417-429. Chapman & Hall, London.
Rocha, H.R., M.L. Goulden, S.D. Miller, M.C. Menton, L.D.V.O Pinto, H.C Freitas, A.M.S. Figueira. 2002. Seasonality of water and heat fluxes over a tropical forest in eastern Amazonia. Submitted to Ecological Applications.
Rocha, H. R., O.M.R. Cabral, M.A.F. Silva Dias, M.A.Ligo, J.A. Elbers, H.C. Freitas, C. von Randow, O. Brunini, 2000. Atmospheric CO₂ fluxes and soil respiration over sugar cane in southeast Brazil. in Global Climate Change and Tropical Ecossystems, p. 405-414. eds. R. Lal, J. Kimble, B. Stewart, CRC Press, Boca Raton, FL.
Rocha, H. R. da, P.J. Sellers, C. J. Collatz, I.R. Wright, J. Grace, 1996a. Calibration and use of the SiB2 model to estimate water vapour and carbon exchanges in the Abracos' forest sites. in Amazon Deforestation and Climate, eds. J.C.H. Gash, C.A. Nobre, J.M. Roberts and R. Victória. John Wiley & Sons, Chichester, UK, p. 459-472.
Rocha, H.R. da, C.A. Nobre, J.P. Bonatti, I.R. Wright, I.R., P.J. Sellers. 1996b. A vegetation-atmosphere interaction study for Amazonian deforestation using field data and a single column model. Quarterly Journal of the Royal Meteorological Society: 122, 567-598, 1996.
Sakai, R.K., D.R. Fitzjarrald, and K.E. Moore. 2001. Importance of Low-frequency contributions to eddy fluxes observed over rough surfaces. Journal of Applied Meteorology, 40:2178-2191.
San Jose, J.J., M.L.Meirelles, R.Bracho and N Nikonova, 2001. A comparative analysis of the flooding and fire effects on the energy exchange in a wetland community (Morichal) of Orinoco Llanos. Journal of Hydrology, 242, 228-254.
Sellers, P. J., D.A. Randall, C.J. Collatz, J.A. Berry, C.B. Field, D.A. Dazlich, C. Zhang, G.D. Collelo, 1996. A revised land surface parameterization (SiB2) for atmospheric GCMs, Part I: Model formulation. J. Climate, 9, 676-705.
Silva, J.M.C. and J.Bates, 2002. Biogeographic patterns and conservation in south america cerrado: a tropical savanna hotspot. BioScience, 52(3):, 225-233.
Szarzinsky, J. and D.Anhuf 2001. Micrometeorological conditions and canopy energy exchange of a neotropical rain forest (Surumoni crane project - Venezuela). Plant ecology, 153, 231-239.
Trumbore, S. E., E. A Davidson, P. B. Camargo, D. C. Nepstad, L. A Martinelli. Below ground cycling of carbon in forests and pastures of eastern Amazonia. Global Biogeochemical Cycles, 9: 515-528, 1995
Vourlitis, G., N.Priante Filho, M.M.S.Hayashi, J.S.Nogueira,F.T.Caseiro and J.H.Campelo Jr, 2001. Seasonal variations in the net ecosystem CO2 exchange of a mature amazonian transitional tropical forest (Cerradão). Functional ecology, 15 338-395.
Vourlitis, G., N.Priante Filho, M.M.S.Hayashi, J.S.Nogueira,F.T.Caseiro and J.H.Campelo Jr, 2002. The role of seasonal variations in meteorology on the net CO2 exchange of a brazilian transitional tropical forest. In II Scientific Conference LBA (Large scale biosphere-atmosphere experiment in Amazonia), Manaus, 9-11 July, 2002.

Publication Dates

Publication in this collection
11 June 2013
Date of issue
2002

History

Accepted
30 June 2002
Reviewed
20 June 2002
Received
01 Mar 2002

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

[1] A n h u f , D . , T . M o t z e r , R . Rollenbeck,B.Schroder,J.Szarzinsky 1999. Water budget of the Surumoni crane site (Venezuela). Selbyana, 20:1, 179-185.

[2] Batalha, M.A. 1997. Análise da vegetação da ARIE Cerrado Pé-de-Gigante. Dissertação de Mestrado. Instituto de Biociências / USP.

[3] Castro E. A. and Kauffman J. B., 1998. Ecosystem struture in the Brazilian Cerrado: a vegetation gradient of aboveground biomass, root mass, and consumption by fire. Journal of Tropical Ecology, 14, 263-283

[4] Collatz, G.J., J. T. Ball, C. Grivet, J.A.Berry, 1991. Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: a model that includes a laminar boundary layer. Agricultural and Forest Meteorology, 54: 107-136.

[5] Collatz, G.J., M.Ribas-Carbo, J.A.Berry, 1992. Coupled photosynthesis-stomatal conductance model for leaves of C4 plants. Aust. J. Plant Physiol., 19: 519-538.

[6] Coutinho, L.M. , 1978. O Conceito de Cerrado. Revista Brasileira de Botânica, 1, 17-23.

[7] Delitti W. B. C. , Pausas J. G. , Burger D. M., 2001. Belowground biomass seasonal variation in two Neotropical savannahs ( Brazilian Cerrados) with different fire histories. Ann. For. Sci, 58, 713-721.

[8] Davidson, E. A, L. V. Verchot, J. H. Cattanio, I. L. Ackerman, J. E. M. Carvalho. Effects of soil water content on soil respiration in forests and cattle pastures of eastern Amazonia. Biogeochemistry, 48: 53-69, 2000

[9] Eiten, G. 1972. The cerrado vegetation of Brazil. The Botanical Review, 38, 201-341.

[10] Finnigan, J.J., R. Clements, Y. Malhi, R. Leuning, and H.A. Clough, 2002. A re-evaluation of long-term flux measurement, Submitted to Boundary Layer Meteorology.

[11] Goulden, M.L., J.W. Munger, S.-M. Fan, B.C. Daube, and S. 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.

[12] Goulden, M. L., S.D. Miller, M.C. Menton, H.R. da Rocha, H.C. Freitas. 2002 Physiological Controls on Tropical Forest CO2 Exchange. Submitted to Ecological Applications.

[13] Grace, J., Y. Malhi, J. Lloyd, J. McIntyre, A.C. Miranda, P. Meir, and H.S. Miranda. 1996. The use of eddy covariance to infer the net carbon dioxide uptake of Brazilian rain forest. Global Change Biology 2:208-217

[14] LBA, 1996. The Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), Concise Experimental Plan. Compiled by the LBA Science Planning Group. Doccument available at CPTEC/INPE, Cachoeira Paulista, SP, Brazil.

[15] M a l h i , Y . , A . D . N o b r e , J.Grace,B.Kruijt,M.G.P.Pereira,A.Culf,S.Scott. Carbon dioxide transfer over a central amazonian rain forest. Journal of Geophysical Research, 103, D24:31593-31612, 1998

[16] Meir, P., J. Grace, A. Miranda and J. Lloyd. Soil respiration in a rainforest in Amazonia and in Cerrado in Central Brazil. In Amazonian Deforestation and Climate, eds J.Gash, C. Nobre, J. Roberts and R. Victoria, p. 319-329, 1996.

[17] Miller, S.D., M.L. Goulden, M.C. Menton, H.R. da Rocha, and H.C. Freitas. 2002. Annual CO2 Exchange by a tropical Forest. (Journal of Ecological Applications, in press)

[18] Miranda, A.C., H.S. Miranda, J. Lloyd, J. Grace, J.A., Francey,J.R., McIntyre, P. Meir, P. Riggan, R. Lockwood, J. Brass, 1997. Fluxes of carbon, water and energy over Brazilian cerrado: an analysis using eddy covariance and stable isotopes. Plant, Cell and Environment, 20: 315-328.

[19] Mittermeyer,R.A.,N.Myers,C.G.Mittermeyer, 2000. Hotspots: earth's biologically richest and most endangered terrestrial ecoregions. Mexico City, CEMEX.

[20] Moncrieff, J.B., J.M. Massheder, H. de Bruin, J.Elbers, T. Friborg, B. Heusinkveld, P. Kabat, S. Scott, H. Soegaard and A. Verhof 1997. A system to measure surface fluxes of momentum, sensible heat, water vapour and carbon dioxide. Journal of Hydrology, 189, 589-611.

[21] Parkinson, K.J., 1981. An improved method for measuring soil respiration in the field. Journal of Applied Ecology, 18, 221-228.

[22] Pivelo, V. R. and L.M. Coutinho, 1996. A qualitative successional model to assist in the management of Brazilian cerrados . Forest Ecology and Management, 87, 127-138

[23] Ratter, J.A. 1992. Transitions between cerrado and forest vegetation in Brazil. In Nature and dynamics of forest-savanna boundaries, (eds P.A. Furley, J. Proctor and J.A. Ratter), p. 417-429. Chapman & Hall, London.

[24] Rocha, H.R., M.L. Goulden, S.D. Miller, M.C. Menton, L.D.V.O Pinto, H.C Freitas, A.M.S. Figueira. 2002. Seasonality of water and heat fluxes over a tropical forest in eastern Amazonia. Submitted to Ecological Applications.

[25] Rocha, H. R., O.M.R. Cabral, M.A.F. Silva Dias, M.A.Ligo, J.A. Elbers, H.C. Freitas, C. von Randow, O. Brunini, 2000. Atmospheric CO₂ fluxes and soil respiration over sugar cane in southeast Brazil. in Global Climate Change and Tropical Ecossystems, p. 405-414. eds. R. Lal, J. Kimble, B. Stewart, CRC Press, Boca Raton, FL.

[26] Rocha, H. R. da, P.J. Sellers, C. J. Collatz, I.R. Wright, J. Grace, 1996a. Calibration and use of the SiB2 model to estimate water vapour and carbon exchanges in the Abracos' forest sites. in Amazon Deforestation and Climate, eds. J.C.H. Gash, C.A. Nobre, J.M. Roberts and R. Victória. John Wiley & Sons, Chichester, UK, p. 459-472.

[27] Rocha, H.R. da, C.A. Nobre, J.P. Bonatti, I.R. Wright, I.R., P.J. Sellers. 1996b. A vegetation-atmosphere interaction study for Amazonian deforestation using field data and a single column model. Quarterly Journal of the Royal Meteorological Society: 122, 567-598, 1996.

[28] Sakai, R.K., D.R. Fitzjarrald, and K.E. Moore. 2001. Importance of Low-frequency contributions to eddy fluxes observed over rough surfaces. Journal of Applied Meteorology, 40:2178-2191.

[29] San Jose, J.J., M.L.Meirelles, R.Bracho and N Nikonova, 2001. A comparative analysis of the flooding and fire effects on the energy exchange in a wetland community (Morichal) of Orinoco Llanos. Journal of Hydrology, 242, 228-254.

[30] Sellers, P. J., D.A. Randall, C.J. Collatz, J.A. Berry, C.B. Field, D.A. Dazlich, C. Zhang, G.D. Collelo, 1996. A revised land surface parameterization (SiB2) for atmospheric GCMs, Part I: Model formulation. J. Climate, 9, 676-705.

[31] Silva, J.M.C. and J.Bates, 2002. Biogeographic patterns and conservation in south america cerrado: a tropical savanna hotspot. BioScience, 52(3):, 225-233.

[32] Szarzinsky, J. and D.Anhuf 2001. Micrometeorological conditions and canopy energy exchange of a neotropical rain forest (Surumoni crane project - Venezuela). Plant ecology, 153, 231-239.

[33] Trumbore, S. E., E. A Davidson, P. B. Camargo, D. C. Nepstad, L. A Martinelli. Below ground cycling of carbon in forests and pastures of eastern Amazonia. Global Biogeochemical Cycles, 9: 515-528, 1995

[34] Vourlitis, G., N.Priante Filho, M.M.S.Hayashi, J.S.Nogueira,F.T.Caseiro and J.H.Campelo Jr, 2001. Seasonal variations in the net ecosystem CO2 exchange of a mature amazonian transitional tropical forest (Cerradão). Functional ecology, 15 338-395.

[35] Vourlitis, G., N.Priante Filho, M.M.S.Hayashi, J.S.Nogueira,F.T.Caseiro and J.H.Campelo Jr, 2002. The role of seasonal variations in meteorology on the net CO2 exchange of a brazilian transitional tropical forest. In II Scientific Conference LBA (Large scale biosphere-atmosphere experiment in Amazonia), Manaus, 9-11 July, 2002.