Biologists Uncover Forests' Unexpected Role In Climate Change
Arthur T Knackerbracket has processed the following story:
In a study published in the Proceedings of the National Academy of Sciences, Professor Richard Thomas and alumnus Justin Mathias (BS Biology, '13 and Ph.D. Biology, '20) synthesized published tree ring studies. They found that increases in carbon dioxide in the atmosphere over the past century have caused an uptick in trees' water-use efficiency, the ratio of carbon dioxide taken up by photosynthesis to the water lost by transpiration -- the act of trees "breathing out" water vapor.
"This study really highlights the role of forests and their ecosystems in climate change," said Thomas, interim associate provost for graduate academic affairs. "We think of forests as providing ecosystem services. Those services can be a lot of different things -- recreation, timber, industry. We demonstrate how forests perform another important service: acting as sinks for carbon dioxide. Our research shows that forests consume large amounts of carbon dioxide globally. Without that, more carbon dioxide would go into the air and build up in the atmosphere even more than it already is, which could exacerbate climate change. Our work shows yet another important reason to preserve and maintain our forests and keep them healthy."
Previously, scientists have thought that trees were using water more efficiently over the past century through reduced stomatal conductance -- meaning trees were retaining more moisture when the pores on their leaves began closing slightly under rising levels of carbon dioxide.
However, following an analysis using carbon and oxygen isotopes in tree rings from 1901 to 2015 from 36 tree species at 84 sites around the world, the researchers found that in 83% of cases, the main driver of trees' increased water efficiency was increased photosynthesis -- they processed more carbon dioxide. Meanwhile, the stomatal conductance only drove increased efficiency 17% of the time. This reflects a major change in how trees' water efficiency has been explained in contrast to previous research.
Journal Reference:
Justin M. Mathias, Richard B. Thomas. Global tree intrinsic water use efficiency is enhanced by increased atmospheric CO2 and modulated by climate and plant functional types [$], Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2014286118)
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