Navigation Links
Drought and fire in the Amazon lead to sharp increases in forest tree mortality
Date:4/17/2014

Ongoing deforestation and fragmentation of forests in the Amazon help create tinderbox conditions for wildfires in remnant forests, contributing to rapid and widespread forest loss during drought years, according to a team of researchers.

The findings show that forests in the Amazon could reach a "tipping point" when severe droughts coupled with forest fires lead to large-scale loss of trees, making recovery more difficult, said Jennifer Balch, assistant professor of geography, Penn State.

"We documented one of the highest tree mortality rates witnessed in Amazon forests," Balch said. "Over the course of our experiment, 60 percent of the trees died with combined drought and repeated fire. Our results suggest that a perfect firestorm, caused by drought conditions and previous fire disturbance, crossed a threshold in forest resistance."

Balch noted that climate change is expected to warm the air in the Amazon region by several degrees and substantially reduce regional precipitation, making understanding the interactions between droughts and fires even more important. "However, even before any prediction of Amazon climate warming occurs, our study demonstrates that drought and fire are already driving forest dieback," she said.

The eight-year study is the largest and longest-running fire experiment in tropical forests. The team of researchers burned 50-hectare forest plots in the southeastern Amazon, a region prone to the effects of climate change.

The plots were burned every year, every three years or not at all. The timeframe for the study included 2007, a year of severe drought. By comparing the tree deaths for the plots each year, the researchers could assess the effect of drought on fire intensity and tree deaths.

"Drought causes more intense and widespread fires," said lead author Paulo Brando, Instituto de Pesquisa Ambiental da Amaznia, Carnegie Institution for Science and Woods Hole Research Center. "Four times more adult trees were killed by fire during a drought year, which means that there was also more carbon dioxide released to the atmosphere, more tree species loss and a greater likelihood of grasses invading the forest."

The researchers found that fragmented forests are more susceptible to the negative impacts of drought and fire and that drought leads to an increase in fuel such as leaves and branches. The findings are key, in part, because most climate change models have not included the impacts of fires on Amazonian forests.

"Basically, none of the models used to evaluate future Amazon forest health include fire, so most of these predictions grossly underestimate the amount of tree death and overestimate overall forest health," said Michael Coe, Woods Hole Research Center.

Fire as a forest management tool can contribute to an increase in severe fires because the resulting thinner canopy leads to dryer forest conditions. This lack of humidity does not dampen fires but does encourage airflow between fields and forests. Fragmented forests also have more edge space, which is susceptible to both fire and invasive grasses -- another potential fuel.

"These forests are tough and can take a lot, but if drought reaches a certain level, big trees begin to die," said Daniel Nepstad, Earth Innovation Institute, who also co-led the study. "We now know that severe drought also makes fires more intense, creating a second tree mortality threshold."

The researchers conclude in today's (April 14) issue of Proceedings of the National Academy of Science that "efforts to end deforestation in the Amazon must be accompanied by programs and policies that reduce the accidental spread of land management fires into neighboring forests and effectively control forest fires when started."

The results are important because large portions of the Amazon forest already experience droughts and are susceptible to fire -- they are broken into smaller blocks by agriculture and they are close to humans, who are the predominant source of fire in the Amazon. The researchers analyzed NASA satellite data to provide regional context for results from the experimental burns.

"In 2007, fires in Southeast Amazonia burned 10 times more forest than in an average climate year -- an area equivalent to a million soccer fields," said Douglas Morton, NASA.

"These smaller forest fragments have more edges than large blocks of forest, which exposes them to the hotter, dryer conditions in the surrounding landscape and makes them more vulnerable to escaped fires," said co-author Marcia Macedo, Woods Hole Research Center.

By 2011, around 8 percent of Southeast Amazonia's forests were less than 328 feet from an agricultural or pasture clearing. This lattice-like network of degraded forest edges is now extremely susceptible to future fire.


'/>"/>

Contact: A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
Source:Eurekalert  

Related biology news :

1. UC geographers develop a system to track the dynamics of drought
2. Pilot Islamic-compliant livestock insurance product in Africa pays pastoralists in drought-prone Kenya
3. Drought and downing equal vulture supermarkets
4. Amazon rainforest more able to withstand drought than previously thought
5. New book addresses consequences of drought in arid regions
6. Researchers discover protein that helps plants tolerate drought, flooding, other stresses
7. Drought, river fragmentation forcing endangered fish out of water, biologist finds
8. Monsoon failure key to long droughts in Southwest
9. Plants adapt to drought but limits are looming, study finds
10. Drought in the Horn of Africa delays migrating birds
11. Plant stress paints early picture of drought
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Drought and fire in the Amazon lead to sharp increases in forest tree mortality
(Date:2/2/2017)... -- Central to its deep commitment to honor the ... Prize Foundation today announced the laureates of the ... in their respective fields of Life Sciences and ... recognized with the 2017 Japan Prize for original ... the advancement of science and technology, but also ...
(Date:1/26/2017)... 2017  Crossmatch, a leading provider of security and ... at combatting fraud, waste and abuse in assistance operations ... Action on Disaster Relief conference in Panama ... agencies and foreign assistance organizations throughout Latin ... are a largely unacknowledged problem in the foreign assistance ...
(Date:1/24/2017)... PHILADELPHIA , Jan. 24, 2017  It ... a baby,s sock that monitors vital signs and ... instance, an infant,s oxygen saturation level drops. But ... undue alarm to parents, with no evidence of ... "These devices are marketed aggressively to parents of ...
Breaking Biology News(10 mins):
(Date:2/24/2017)... Feb. 24, 2017  Aethlon Medical, Inc. (Nasdaq: ... by its Chairman and CEO, Jim Joyce . ... Security Conference last Saturday, Bill Gates warned ... more people than nuclear weapons. Mr. Gates expressed his ... intelligence agencies, that scientific terrorists have access to the ...
(Date:2/24/2017)... Inc. (NASDAQ: CBPO) ("China Biologic" or the "Company"), a leading ... financial results for the fourth quarter and fiscal year of ... Total sales in the fourth quarter of ... 13.6% in USD terms to $77.6 million from $68.3 million ... profit increased by 13.3% to $46.8 million from $41.3 million ...
(Date:2/23/2017)... ... February 23, 2017 , ... BellBrook Labs is formalizing a ... array of biochemical analyses critical for Lead Discovery. The company’s Lead Discovery ... programs, including inhibitor potency and selectivity, mechanism of action, and inhibitor residence times ...
(Date:2/23/2017)... Feb. 23, 2017  Imanis Life Sciences announced ... of oncolytic vaccinia viruses for virotherapy research. These ... of Genelux,s proprietary, vaccinia virus-based technology platform for ... enter into a partnership with Genelux to offer ... viruses for use in research," said Dr. ...
Breaking Biology Technology: