Amazon Basin Drought Doubled Tree Mortality To 4-7%, Cut Carbon Uptake by 1.4 Billion Tons
Severe drought five years ago caused an observed doubling in the rate of tree mortality in the Amazon rainforest, according to a study published in the journal Nature on Wednesday. In addition, the drought caused the forest to take up about 1.4 billion tonnes less carbon dioxide from the atmosphere.
The Amazon forest acts as a carbon sink, because trees suck the greenhouse gas CO2 out of the atmosphere as they grow, during photosynthesis, converting this to plant matter including bark, wood and roots. The Nature article showed how droughts may disrupt this carbon sink, both as a result of reduced photosynthesis and tree die-back. The study may be a concern, if climate change in future caused more frequent, severe droughts.
The main finding of the study was that trees still grew even during a severe drought, but that was at the expense of using energy for tissue maintenance, defence and putting aside sugars against future stresses.
Weakened maintenance may have contributed to greater death tree mortality observed in the years following the drought, the authors said. They found that rates of tree mortality at least doubled in the drought-affected areas, to 4-7%, from a long-term trend of 1.6%.
EDIT
http://www.rtcc.org/2015/03/05/amazon-drought-led-to-doubling-of-tree-mortality/
