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

Autor(es)

Humberto R. da Rocha ^[1] ; Helber C. Freitas ^[2] ; Rafael Rosolem ^[3] ; Robinson I.N. Juárez ^[4] ; Rafael N. Tannus ^[5] ; Marcos A. Ligo ^[6] ; Osvaldo M. R. Cabral ^[7] ; Maria A.F. Silva Dias ^[8]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. IAG. Departamento de Ciências Atmosféricas - Brasil

^[2] Universidade de São Paulo. IAG. Departamento de Ciências Atmosféricas

^[3] Universidade de São Paulo. IAG. Departamento de Ciências Atmosféricas

^[4] Universidade de São Paulo. IAG. Departamento de Ciências Atmosféricas

^[5] Universidade de São Paulo. IAG. Departamento de Ciências Atmosféricas

^[6] EMBRAPA Meio Ambiente

^[7] EMBRAPA Meio Ambiente

^[8] Universidade de São Paulo. IAG. Departamento de Ciências Atmosféricas

• Tipo de documento: Artigo Científico
• Fonte: Biota Neotropica; v. 2, n. 1, p. 1-11, 2002-00-00.
• Área do conhecimento: Ciências Exatas e da Terra - Geociências
• Assunto(s): Fotossíntese Carbono Mudança climática Savana Cerrado

Resumo

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. (AU)

• Processo FAPESP: 99/11215-9 - Interação biosfera-atmosfera em ecossistemas naturais e agroecossistemas: um monitoramento sobre cana-de-açúcar e cerrado
• Beneficiário: Humberto Ribeiro da Rocha
• Modalidade de apoio: Auxílio à Pesquisa - Programa BIOTA - Regular