The Amazon rainforest is the largest terrestrial reservoir or “sink” for carbon dioxide, a gas that has been linked to climate change. Through photosynthesis, the Amazon absorbs 1.5 billion tons of carbon dioxide from the atmosphere every year in a process that requires input of nitrogen. That nitrogen, for the most part, comes from a process called nitrogen fixation – essentially microbes pulling nitrogen form the air into the soil.
Rodrigues’ team gathered samples of soil from the Fazenda Nova Vida site in Rondonia, Brazil, one of three states in the country that accounted for more than 85 percent of deforestation from 1996 to 2005. They analyzed soil from a primary forest, a pasture established in 2004 and a secondary forest that resulted from the abandonment of a pasture in 1999.
The team used DNA analysis, specifically the nifH gene that is characteristic of diazotrophs, to measure the communities in the samples.
Rodrigues said researchers were surprised to find a ten-fold increase in the number of diazotrophic microorganisms in the pasture established in 2004, when compared to the primary forests. They theorize the pasture ecosystems rely on the diazotrophs more for nitrogen because of the continuous grazing from cattle, requiring constant regrowth of grasses.
“We observed a complete shift in the diazotrophic microbial community composition in response to the Amazon rain forest conversion to a pasture,” Mirza said. “These differences an be attributed to the shift in the above ground plant community because we did see partial recovery of diazotroph community composition in the secondary forest, which have more plant species as compared to pasture.”
Mirza said researchers are continuing their work with more more sophisticated sequencing technologies and in-depth sampling.
Other co-authors on the new paper include Chotima Potisap, a visiting Ph.D. student from Khon Kaen University in Thailand; Klaus Nüsslein, professor of microbiology at the University of Massachusetts; and Brendan J.M. Bohannan, professor at the Institute of Ecology and Evolution, University of Oregon.
The paper is titled “Response of Free-Living Nitrogen Fixing Microorganisms to Land Use Change in the Amazon Rainforest” and is available online here: http://aem.asm.org/content/early/2013/10/21/AEM.02362-13.full.pdf+html.
Despite worries about the effect these changes to the microbial communities may have on the carbon cycle, Rodrigues said there are some encouraging results. After pastures were abandoned and a secondary forest grew, partial restoration of the original diazotrophic communities was achieved, researchers said.
Growth of secondary forest is ongoing for about 50 percent of the abandoned pastures in the Amazon, but more needs to be done to encourage secondary forests and limit deforestation in the first place, Rodrigues said.
“There is still time to recover if we act now,” he said.
An Agriculture and Food Research Initiative grant from the U.S. Department of Agriculture supported the work detailed in the paper.
The University of Texas at Arlington is a comprehensive research institution of more than 33,300 students and 2,300 faculty members in the epicenter of North Texas. It is the second largest institution in The University of Texas System. Total research expenditures reached almost $78 million last year.
Traci Peterson | EurekAlert!
Environmental DNA uncovers biodiversity in rivers
30.08.2016 | Universität Zürich
New approach for environmental test on livestock drugs
27.07.2016 | Universität Zürich
Scientists and engineers striving to create the next machine-age marvel--whether it be a more aerodynamic rocket, a faster race car, or a higher-efficiency jet...
Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.
In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...
Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.
Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...
Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...
A nanocrystalline material that rapidly makes white light out of blue light has been developed by KAUST researchers.
25.08.2016 | Event News
24.08.2016 | Event News
12.08.2016 | Event News
30.08.2016 | Ecology, The Environment and Conservation
30.08.2016 | Power and Electrical Engineering
30.08.2016 | Life Sciences