Increasing carbon dioxide in the atmosphere teaches old oaks new tricks


Date:
October 4, 2021
Source:
University of Birmingham
Summary:
Mature oak trees will increase their rate of photosynthesis by
up to a third in response to the raised CO2 levels expected to be
the world average by about 2050, new research shows.



FULL STORY ========================================================================== Mature oak trees will increase their rate of photosynthesis by up to
a third in response to the raised CO2 levels expected to be the world
average by about 2050, new research shows.


==========================================================================
The results, published in Tree Physiology, are the first to emerge from a
giant outdoor experiment, led by the University of Birmingham in which an
old oak forest is bathed in elevated levels of CO2. Over the first three
years of a ten-year project, the 175-year-old oaks clearly responded to
the CO2 by consistently increasing their rate of photosynthesis.

Researchers are now measuring leaves, wood, roots, and soil to find out
where the extra carbon captured ends up and for how long it stays locked
up in the forest.

The increase in photosynthesis was greatest in strong sunlight. The
overall balance of key nutrient elements carbon and nitrogen did not
change in the leaves. Keeping the carbon to nitrogen ratio constant
suggests that the old trees have found ways of redirecting their elements,
or found ways of bringing more nitrogen in from the soil to balance the
carbon they are gaining from the air.

The research was carried out at the Free-Air CO2 Enrichment (FACE)
facility of the Birmingham Institute of Forest Research (BIFoR) in close collaboration with colleagues from Western Sydney University who run a
very similar experiment in old eucalyptus forest (EucFACE). BIFoR FACE
and EucFACE are the world's two largest experiments investigating the
effect of global change on nature.

Birmingham researcher Anna Gardner, who carried out the measurements,
said "I'm really excited to contribute the first published science
results to BIFoR FACE, an experiment of global importance. It was
hard work conducting measurements at the top of a 25 m oak day after
day, but it was the only way to be sure how much extra the trees were photosynthesising." Professor David Ellsworth, EucFACE lead scientist,
said "Previous work at EucFACE measured photosynthesis increased by up
to a fifth in increased carbon dioxide. So, we now know how old forest
responds in the warm-temperate climate that we have here in Sydney,
and the mild temperate climate of the northern middle latitudes where Birmingham sits. At EucFACE we found no additional growth in higher CO2,
and it remains to be seen if that will be the case for BIFOR as well." Professor Rob MacKenzie, founding Director of BIFoR, said "It's a
delight to see the first piece of the carbon jigsaw for BIFoR FACE
fall into place. We are sure now that the old trees are responding
to future carbon dioxide levels. How the entire forest ecosystem
responds is a much bigger question requiring many more detailed
investigations. We are now pushing ahead with those investigations." ========================================================================== Story Source: Materials provided by University_of_Birmingham. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. A Gardner, D S Ellsworth, K Y Crous, J Pritchard, A R MacKenzie. Is
photosynthetic enhancement sustained through three years of elevated
CO2 exposure in 175-year-old Quercus robur? Tree Physiology, 2021;
DOI: 10.1093/treephys/tpab090 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211004104107.htm

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