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Small trees offer hope for tropical forests

Small trees offer hope for tropical forests

Drought in the Amazon affects trees more severely, as they are more likely to die from hydraulic failure. Credit: David Bartholomew

New research shows that small trees that grow in drought conditions can form the basis of more drought-resistant rainforests.

Severe and prolonged droughts are becoming more common in the Amazon, often killing large trees that form the forest canopy.

But a new study led by the University of Exeter suggests that small trees adapt better to drought and can grow into a new generation to help rainforests survive.

Using data from a long-term drought experiment in Brazil, the researchers found that small trees respond positively to the extra light they receive when larger trees die, increasing their capacity for photosynthesis and growth despite the lack of water.

“Conditions in the Amazon are shifting due to climate change and trees will have to adapt if they are to survive,”

; said lead author David Bartholomew of the Exeter Institute for Global Systems.

“Our findings show that small trees are more able to change their physiology in response to changes in the environment than their larger neighbors.

“Growing in drought conditions, these trees can develop traits that will help them cope with future droughts – even after they are fully grown.

Small trees offer hope for tropical forests

Under prolonged drought conditions, the dense canopy becomes more open and more light reaches the lower layers of the forest. Credit: David Bartholomew

“Ultimately, this could allow them to form the next generation of canopy trees, leading to greater overall resilience in the forest.”

The study examines trees in a 15-year experiment with the Amazon drought, in which clear plastic panels capture 50% of rainfall.

The researchers took samples of 66 small trees (1-10 cm in diameter at a height of 1.3 m from the ground) and 61 large trees (over 20 cm in diameter) in the area of ​​the drought experiment and in the nearby control area without excluding precipitation.

Small trees in the land area show increased capacity for photosynthesis (Jmax 71%, Vcmax 29%), 32% more leaf respiration and 15% more leaf mass per area compared to small trees in the control area.

“This long-term experiment has shown that large trees are quite vulnerable to drought and are unlikely to survive if droughts continue to become more common and severe,” said Bartholomew, Ph.D. student of NERC GW4 + doctoral training for partnership.

“However, relatively little is known about the reaction of small trees to underground trees, which could be vital in determining the future of tropical forests.

Small trees offer hope for tropical forests

The drought experiment stopped 50% of the water from reaching the ground. Credit: David Bartholomew

“The underground tree of an intact rainforest is usually a dark and humid environment.

“Trees found in low light conditions usually reduce their photosynthetic ability to conserve resources.

“However, if droughts cause larger trees to die, these trees will have to adapt to both declining water availability and increased light.

“Our research suggests they have a remarkable ability to do this.”

The responses of tree species in the study varied, with some showing strong adaptability and others very little.

More research is needed to understand how this could change the makeup of the famous diverse Amazon rainforest in the future.

The document published in the magazine Plant, cells and environment, is entitled: “Small tropical forest trees have a greater capacity to adapt carbon metabolism to long-term drought than large canopy trees.”

Some tree species retain stored water, restrict root growth to survive three months without water

More info:
David C. Bartholomew et al., Small tropical forest trees have a greater capacity to adapt carbon metabolism to long-term drought than large canopy trees, Plant, cells and environment (2020). DOI: 10.1111 / pce.13838

Provided by the University of Exeter

Quote: Small trees offer hope for tropical forests (2020, August 5), extracted on August 6, 2020 from https://phys.org/news/2020-08-small-trees-rainforests.html

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