Environment Counts | Amazon carbon balance is found to be sensitive to drought
Author: Geoff Zeiss – Published At: 2014-02-27 01:05 – (1076 Reads)
The Amazon watershed stores a vast amount of carbon. Over the past two decades it has experienced increasingly higher temperatures and more frequent floods and droughts. This article reports annual carbon balances across the Amazon watershed, based on atmospheric carbon dioxide and carbon monoxide measurements for 2010 and 2011. Fortuitously 2010 was an extraordinarily dry year and 2011 was exceptionally wet in the Amazon. It was found that the carbon flux between the non-burned forest and the atmosphere was carbon neutral during the dry year. During the wet year, vegetation sequestered net 0.25â€‰Â±â€‰0.14 petagrams of carbon per year (Pgâ€‰Câ€‰/yr). Nature,506,76â€“80 (06 February 2014) doi:10.1038/nature12957
In the Amazon 2010 was an anomalously dry and 2011 was exceptionally wet.
Based on the atmospheric CO2 measurments it was determined that the Amazon watershed lost 0.48â€‰Â±â€‰0.18 petagrams of carbon per year (Pgâ€‰Câ€‰/yr) during the dry year but was carbon neutral (0.06â€‰Â±â€‰0.1â€‰Pgâ€‰Câ€‰/yr) during the wet year.
Taking into account carbon losses from fire by using carbon monoxide measurements, it was calculated that in the dry year the net carbon flux between the non-burned forest and the atmosphere was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25â€‰Â±â€‰0.14â€‰Pgâ€‰Câ€‰/yr/ This is consistent within the estimated error with the mean long-term intact-forest biomass sink of 0.39â€‰Â±â€‰0.10â€‰Pgâ€‰Câ€‰/yr previously estimated from forest censuses.
It is suggested that drought suppresses photosynthesis. Overall, the results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net carbon sequestration because of drought.
The article documents the response of a large fraction of the Amazonian vegetation to drought, with forest productivity stalled and large amounts of carbon released by fire in 2010. The Amazon basin returned to being a net carbon sink in 2011. But the results are cause for concern in the light of the recent increase in precipitation extremes and increasing temperatures. If these climate trends continue, future shifts in Amazon forest function, leading to reduced carbon uptake, are likely. This could exacerbate carbon losses as a result of direct human activities such as deforestation.
Nature,506,76â€“80 (06 February 2014) doi:10.1038/nature12957