"We found that trees in warmer, drier climates are essentially coughing instead of breathing," said Max Lloyd assistant research professor of geosciences at Penn State and lead author on the study recently published in Proceedings of the National Academy of Sciences. "They are sending CO2 right back into the atmosphere far more than trees in cooler, wetter conditions."
I think it means the trees still absorb carbon dioxide. However, it's written in a way that it could also mean the trees are pumping carbon dioxide out. It sounds much more extreme.
as is the current regime of C3 photosynthesis is promiscuous, and involvves O2 photorespiration in some proportion.
temperature beyond nominal range will increase the incorporation of O2 and begin 'starving' the plant.
what this means is-- trees plants etc lose thier carbon sinking ability beyond a threshold temperature, it is detrimental, and they consume increased quantities of O2 , and have to spend energy to eliminate the product
The laboratory conditions that allow us [you included] to observe this phenomenon are no longer an extreme, or a laboratory demonstration.
It's such a complex system. I'm reminded of how wrong eminent physicist Freeman Dyson's thinking CO2 being a net benefit because it's "plant food". https://en.wikipedia.org/wiki/Freeman_Dyson
"We found that trees in warmer, drier climates are essentially coughing instead of breathing," said Max Lloyd assistant research professor of geosciences at Penn State and lead author on the study recently published in Proceedings of the National Academy of Sciences. "They are sending CO2 right back into the atmosphere far more than trees in cooler, wetter conditions."
http://dx.doi.org/10.1073/pnas.2306736120