4.5 Article

Large net CO2 loss from a grass-dominated tropical savanna in south-central Brazil in response to seasonal and interannual drought

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JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 121, 期 8, 页码 2110-2124

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AMER GEOPHYSICAL UNION
DOI: 10.1002/2016JG003404

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资金

  1. Universidade Federal de Mato Grosso (UFMT)
  2. Programa de Pos Graduacao em Fisica Ambiental (PPGFA) IF/UFMT
  3. Coordenacao de Aperfeicoamento de Pessoal do Ensino Superior (CAPES)
  4. U.S. National Science Foundation Office of International Science and Engineering [NSF-OISE-IRES 0968245]
  5. LBA project
  6. Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [201630/2015-0]
  7. Projeto Ciencia sem Fronteira

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The savanna vegetation of Brazil (Cerrado) accounts for 20-25% of the land cover of Brazil and is the second largest ecosystem following Amazonian forest; however, Cerrado mass and energy exchange is still highly uncertain. We used eddy covariance to measure the net ecosystem CO2 exchange (NEE) of grass-dominated Cerrado (campo sujo) over 3 years. We hypothesized that soil water availability would be a key control over the seasonal and interannual variations in NEE. Multiple regression indicated that gross primary production (GPP) was positively correlated (Pearson's r = 0.69; p< 0.001) with soil water content, radiation, and the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived enhanced vegetation index (EVI) but negatively correlated with the vapor pressure deficit (VPD), indicating that drier conditions increased water limitations on GPP. Similarly, ecosystem respiration (Reco) was positively correlated (Pearson's r = 0.78; p< 0.001) with the EVI, radiation, soil water content, and temperature but slightly negatively correlated with rainfall and the VPD. While the NEE responded rapidly to temporal variations in soil water availability, the grass-dominated Cerrado stand was a net source of CO2 to the atmosphere during the study period, which was drier compared to the long-term average rainfall. Cumulative NEE was approximately 842 gCm(-2), varying from357 gCm(-2) in 2011 to 242 gCm(-2) in 2012. Our results indicate that grass-dominated Cerrado may be an important regional CO2 source in response to the warming and drying that is expected to occur in the southern Amazon Basin under climate change.

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