Amazonia and the modern carbon cycle: Lessons learned

Laboratório de Ecologia Isotópica-CENA/USP, Av. Centenário, 303, 13416-000, Piracicaba, SP, Brazil.
Oecologia (Impact Factor: 3.09). 06/2005; 143(4):483-500. DOI: 10.1007/s00442-005-0034-3
Source: PubMed

ABSTRACT In this paper, we review some critical issues regarding carbon cycling in Amazonia, as revealed by several studies conducted in the Large Scale Biosphere Atmosphere Experiment in Amazonia (LBA). We evaluate both the contribution of this magnificent biome for the global net primary productivity/net ecosystem exchange (NPP/NEE) and the feedbacks of climate change on the dynamics of Amazonia. In order to place Amazonia in a global perspective and make the carbon flux obtained through the LBA project comparable with global carbon budgets, we extrapolated NPP/NEE values found by LBA studies to the entire area of the Brazilian Amazon covered by rainforest. The carbon emissions due to land use changes for the tropical regions of the world produced values from 0.96 to 2.4 Pg C year(-1), while atmospheric CO2 inversion models have recently indicated that tropical lands in the Americas could be exchanging a net 0.62+/-1.15 Pg C year(-1) with the atmosphere. The difference calculated from these two methods would imply a local sink of approximately 1.6-1.7 Pg C year(-1), or a source of 0.85 ton C ha(-1) year(-1). Using our crude extrapolation of LBA values for the Amazon forests (5 million km2) we estimate a range for the C flux in the region of -3.0 to 0.75 Pg C year(-1). The exercise here does not account for environmental variability across the region, but it is an important driver for present and future studies linking local process (i.e. nutrient availability, photosynthetic capacity, and so forth) to global and regional dynamic approaches.

Download full-text


Available from: Antonio Donato Nobre, Sep 29, 2015
1 Follower
27 Reads
  • Source
    • "Ozone damage to vegetation reduces plant productivity , decreasing the amount of carbon absorbed by plants, and hence has an impact on climate via an indirect radiative forcing (Sitch et al., 2007). Tropical rainforests play an important role in the global carbon budget, as they cover 12 % of the earth's land surface and contain around 40 % of the terrestrial biosphere's carbon (Ometto et al., 2005; Taylor & Lloyd, 1992). It has been estimated that they may account for as much as 50 % of the global net primary productivity (Grace et al., 2001). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The HadGEM2 earth system climate model was used to assess the impact of biomass burning on surface ozone concentrations over the Amazon forest and its impact on vegetation, under present-day climate conditions. Here we consider biomass burning emissions from wildfires, deforestation fires, agricultural forest burning, and residential and commercial combustion. Simulated surface ozone concentration is evaluated against observations taken at two sites in the Brazilian Amazon forest for years 2010 to 2012. The model is able to reproduce the observed diurnal cycle of surface ozone mixing ratio at the two sites, but overestimates the magnitude of the monthly averaged hourly measurements by 5–15 ppb for each available month at one of the sites. We vary biomass burning emissions over South America by ±20, 40, 60, 80 and 100 % to quantify the modelled impact of biomass burning on surface ozone concentrations and ozone damage on vegetation productivity over the Amazon forest. We used the ozone damage scheme in the " high " sensitivity mode to give an upper limit for this effect. Decreasing South Amer-ican biomass burning emissions by 100 % (i.e. to zero) reduces surface ozone concentrations (by about 15 ppb during the biomass burning season) and suggests a 15 % increase in monthly mean net primary productivity averaged over the Amazon forest, with local increases up to 60 %. The simulated impact of ozone damage from present-day biomass burning on vegetation productivity is about 230 TgC yr −1. Taking into account that uncertainty in these estimates is substantial , this ozone damage impact over the Amazon forest is of the same order of magnitude as the release of carbon dioxide due to fire in South America; in effect it potentially doubles the impact of biomass burning on the carbon cycle.
    Atmospheric Chemistry and Physics 03/2015; 15(14):2791-2804. DOI:10.5194/acp-15-2791-2015 · 4.88 Impact Factor
  • Source
    • "La cantidad de absorción de carbono varía sustancialmente con la localización (Ometto et al., 2005). Se estimaron las mayores tasas de absorción en mediciones del crecimiento de los árboles en Perú y Ecuador (Phillips et al., 1998, 2004); por desgracia, no hay torres en estas localidades para realizar medidas de correlación de vórtices comparables. "
  • Source
    • "The carbon balance of Amazonian forests is a matter of global concern because any significant shift towards gain 47 or loss would translate into climatically significant amounts of atmospheric carbon dioxide (Ometto et al. 2005). 48 Forests gain or lose carbon as a result of a balance between rates of tree growth and recruitment on one side and 49 mortality on the other. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Increasing areas of Amazonian forest are coming under flood stress due to dam construction and greater variability in river flood levels due to climate change. The physiological responses of Amazonian trees subjected to flooding are important to understand the consequences of these changes. Irradiance response curves for photosynthesis obtained from ten tropical tree species growing in flooded areas were used to fit three empirical models. The study was done in floodplains along the Uatumã River, both upstream and downstream of the Balbina Hydroelectric Dam in Brazil’s state of Amazonas (01°55′S; 59°28′W). Ten species were studied. Models compared were: non-rectangular hyperbola, rectangular hyperbola, and exponential. All models were quantitatively adequate for fitting the response of measured data on photosynthesis to irradiance for all ten species in the non-flooding and flooding periods. Considerable variation was found among the model estimates of maximum photosynthesis (P nmax), dark respiration (R d) and apparent quantum yield of photosynthesis (α). For photosynthesis, the two hyperbolas overestimated P nmax while EXP presented more realistic values. For estimating R d, RH presented the most realistic values. To avoid unrealistic value estimates of R d, we recommend adding measured R d values to the regressions. The results suggest that the EXP model presented the most realistic P nmax and α values, and, in spite of less accuracy in fitting photosynthetic irradiance curves than the RH model, it can be recommended for accessing the information used in photosynthetic irradiance curves for the leaves of tropical trees growing in Amazonian floodplains or in areas that are artificially flooded by dams.
    Trees 02/2012; 27(1). DOI:10.1007/s00468-012-0788-2 · 1.65 Impact Factor
Show more