New Publication: Tree mortality in Amazonian floodplains

Floodplains in the Amazon

Recently we mentioned that drowned trees along the Uatumã River a likely the cause for enhanced methane emissions measured at ATTO. Now Angélica Resende and her co-authors investigated how changes in flooding regimes impact tree mortality in floodplains. So they compared two sites in the Amazon basin.

Along the Jaú River, the floodplain environment is still largely undisturbed. Along the Uatumã near ATTO, on the other hand, the flooding regime has been altered by the implementation of the Balbina hydroelectric plant further upstream. The construction of the dam flooded an area of 2,400 km2 of native forest.

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Understanding nighttime methane emissions

Methane in the Amazon

Methane emissions are smaller than those of CO2, and methane abundance in the atmosphere is much smaller. But methane is much more efficient in trapping heat than CO2 is, making it a very important greenhouse gas. Like CO2, methane is emitted by the burning of fossil fuels but it also has many natural sources. They include thawing permafrost and wetlands.

This is where the Amazon rainforest comes into play. The Amazon and its tributaries are bordered by wetlands of continually flooded forest. In addition, river levels swell significantly during the wet season and seasonally flood large areas of otherwise dry forest.

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Transport of black carbon-rich smoke from Africa to the Amazon

When forests burn those fires produce a lot of smoke. And that smoke usually contains soot, also called “black carbon”. Black carbon particles are aerosols that absorb radiation and as such can warm the Earth’s atmosphere and climate. But we still have much to learn about aerosols, their properties, and distribution in the atmosphere. One of those things is the question of how black carbon emitted from biomass burning in Africa (i.e. forests, grasslands, savannas etc.) is transported across the Atlantic and into the Amazon basin, and what role it plays there. Bruna Holanda and her co-authors tackled this by combining data from the northeastern Amazon collected with the HALO research aircraft during the ACRIDICON-CHUVA campaign in September 2014, with long-term data from ATTO.

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When do fungi release their spores?

Fungal spore emissions are an important contributor to biogenic aerosols, but we have yet to understand under what conditions fungi release their spores. Nina Löbs and co-authors developed a new technique to measure emissions from single organisms and tested this out at ATTO and with controlled lab experiments. They published their results in the Open Access Journal Atmospheric Measurement Techniques.

large tropical fungi
Fungi of the species Rigidoporus microporus, on which they studied fungal spore emissions. © Sebastian Brill / MPI-C

Aerosols play an important role in various atmospheric processes, and in particular in cloud formation. Therefore it is important to know how they are produced.

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Atmospheric conditions during convective storms over the tropical rainforest

Convective storms often occur the tropics and have the potential to disturb the lower part of the atmosphere. They might even improve the venting of trace gases out of the forest canopy into the atmosphere above. To better understand these processes, Maurício Oliveira and co-authors used the infrastructure at ATTO to study storm outflows during nighttime. They published the results in a new paper in the Open Access Journal Atmospheric Chemistry and Physics.

Why does it rain so frequently in the tropics? The reason is a mixture of many factors, but most importantly it’s very warm and very humid most of the time.

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