New research indicates that in the future, trees may store less carbon than expected
An observed decoupling of photosynthesis from growth suggests that increased carbon uptake does not necessarily translate into greater wood production
Columbia Climate School
It’s intuitive to think that if a tree is photosynthesizing, it’s also growing. But that’s not necessarily so—and a new study of oak trees, published in the journal Science Advances, found that even as they photosynthesize late into the year, their growth stops by mid-summer.
Much of the long-term carbon storage that forests provide depends on trees converting the carbon they absorb through photosynthesis into new wood. Many researchers have predicted that rising atmospheric carbon dioxide (CO2) levels will enhance photosynthesis and stimulate tree growth, putting some of that planet-warming carbon into long-term storage inside wood. However, the observed decoupling of photosynthesis from growth suggests that increased carbon uptake does not necessarily translate into greater wood production. Instead, some of the absorbed carbon may be used to produce foliage or used in short-lived metabolic processes rather than being locked away long term, reducing the amount of carbon stored in forests compared with previous expectations.
The finding has climate implications.
“Right now, most models assume that if you have photosynthesis, you have growth. We find that’s not the case,” says lead author Mukund Palat Rao, an ecoclimatologist at Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. “Just because there is more photosynthesis might not necessarily mean more tree growth in the future.”
During photosynthesis, plants absorb CO2 from the air and then use sunlight to power the conversion of CO2 and water into sugars. Oxygen is released back into the atmosphere while the carbon stays in the plant. In a tree, some of that carbon goes into the woody biomass of trunk, branches and roots. The rest goes into foliage and fruits and is temporarily stored as starch, or is converted into compounds that are released into the soil to feed microbial communities, make nutrients available for uptake and defend against pathogens.
Carbon stored in woody biomass may take decades, centuries or even millennia—depending on conditions—to re-enter the atmosphere, making it an important carbon sink. That also makes it important to understand the relationship between photosynthesis and tree growth. “Understanding how photosynthesis and growth are linked is very important from the perspective of understanding how forests will store carbon over long time scales,” says Rao.
Earlier research has suggested that carbon uptake and tree growth might not be synonymous, but detailed measurements were in short supply and the mechanisms unclear. To study the question, Rao and his colleagues used photosynthesis-detecting satellite imagery of trees at 137 sites across the eastern United States and California; readings from instruments that provided hour-by-hour measurements of treetop CO2 levels; and trunk-borne sensors that yielded real-time measurements of minute fluctuations in tree size. (Trees tend to expand at night as roots take up water, then shrink slightly in daytime as they transpire water, with the long-term trajectory adding up to growth.) They also drew on growth ring records and temperature data from 1950 to the present.
All this produced daily recordings of photosynthesis, carbon uptake and tree growth—and the researchers found that oak growth in their eastern sites generally took place from May through July, even though trees continued to photosynthesize well into October. Roughly 36 percent of all carbon assimilation through photosynthesis occurred after growth had stopped in late summer. At the California sites, oak grew from December through April, but growth slowed in mid-summer and ceased by August even as photosynthesis continued. About 26 percent of those trees’ annual carbon uptake occurred after growth ceased.
This makes mechanistic sense: when water is scarce, trees lose the internal water pressure they need to grow. “The moment you have dry and hot conditions, growth activity stops pretty instantly while photosynthesis seems to continue at a slightly decreased rate,” says Rao.
Some fraction of that post-growth carbon is used to kick-start growth the following year, says Rao. The rest is used to grow new leaves and roots or is oxidized to keep cells alive through winter. Exactly how much is sequestered long-term in woody biomass and how much is released at shorter time scales is unknown, but it seems likely that projections of trees growing larger and storing more carbon in a warmer, CO2-saturated world will need to be revisited.
The researchers also observed that the decoupling between photosynthesis and growth was especially pronounced in years when local climates were most variable, oscillating between extremes of wet and dry. This pattern is expected to become more common as the climate changes.
Rao and his colleagues are now studying whether the decoupling of photosynthesis and growth is taking place in other tree species, ecosystems and regions. Rao expects that decoupling will be found to varying degrees in different forest types and climates, but “I don’t really have answers yet,” he says. “There are many questions still left to address.”
Journal
Science Advances
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
New Research Indicates That in the Future, Trees May Store Less Carbon Than Expected
Article Publication Date
12-Jun-2026
Mountainous landscapes store far more carbon than previously thought, new research shows
The finding may help inform and support climate solutions
University of Oregon
Hilly and mountainous landscapes have a much greater ability to store carbon in the soil than previously thought, according to a new study co-led by scientists at the University of Oregon.
The finding, published June 12 in Science Advances, could help scientists better target natural approaches to addressing atmospheric carbon dioxide and other greenhouse gases that contribute to climate change.
Soil can hold onto carbon that might otherwise exist as atmospheric carbon dioxide, but the amount varies based on the soil’s thickness, texture and mineral composition.
“There was a misconception that mountainous areas would not hold much carbon because they’re so rapidly eroding and there’s not much soil,” said Josh Roering, an earth scientist at the UO. “What we’re saying is, it’s actually the opposite. These areas can be impressive reservoirs of soil organic carbon.”
The research was led by Brooke Hunter during her time as a doctoral student in Roering’s lab. Hunter is now an assistant professor at Appalachian State University.
“When we think about terrestrial carbon, soil contains more carbon than vegetation and the atmosphere combined,” Hunter said. “In order to have an accurate understanding of carbon budgets, we need to know how much carbon is in the soil and where it’s most concentrated.”
Geomorphology, Roering’s specialty, is the study of landforms and the processes that shape them, including the weathering of rock into soil and the erosion of soil from the landscape.
“We have our own form of bookkeeping to determine the rate at which rock is converted into soil and how long the soil hangs out before it is transported into rivers and beyond,” Roering said.
Mountainous areas have been understudied because it’s difficult to traverse the landscape and accurately measure the depth and composition of the soil.
That’s made it harder to protect areas that are good carbon reservoirs by, for example, maintaining tree cover to prevent erosion.
In addition, “there is a lot of movement these days on natural climate solutions for greenhouse gases,” Roering said. Examples include sprinkling minerals on the landscape to enhance rock weathering or seeding soils with nutrients so they better sequester carbon dioxide from the atmosphere.
Better information about the amount of carbon already in the landscape can help scientists more accurately determine how much carbon might be stored through these efforts.
The researchers studied the remnants of nearly 10,000 landslides in the Oregon Coast Range, ranging in age from 4 to 480,000 years, that have become stable repositories of soil and organic material. They augured holes into a representative half-dozen landslides to measure the density of carbon. From that data they created a timeline for all of the landslides and extrapolated a model to estimate carbon stored in landslides across the entire study area.
Their results show that scientists have dramatically underestimated the amount of organic carbon in the soil of landslides. While past models for carbon storage in soil have typically assumed soil depths of 30 centimeters, the researchers found that landslides often contain soil deposits more than 5 meters, or 16 feet, deep.
Thicker soils, they found, also contain higher carbon stocks than thinner soils. This is due to large amounts of fine-grained soils that provide more surface area to fix carbon due to thousands of years of weathering.
“These deep weathering zones are really good at holding carbon,” Roering said. “The older they are, the more weathered they are and the thicker they are, and the more carbon they can store.”
The researchers determined that stocks of carbon in the soil in deep-seated landslides are about twice as large as predicted by a previous global model. “Our research really emphasizes the importance of making better geomorphic maps and integrating our field with models making those predictions,” Roering said.
Much of the past work focused on flat agricultural regions where deposit and erosion of soil is more predictable. By using models that take into account the shape of the landscape and how it has changed over time, scientists can more accurately determine soil depth and carbon density in mountainous regions, potentially opening up new approaches to natural climate solutions.
“When it comes to soil management and natural climate solutions, there isn’t one miracle fix,” Hunter said. “Incorporating these models can help determine what specific methods might be effective at specific sites.”
Added Roering: “If you are going to manage the landscape for carbon, you would want to know where the areas with high amounts of carbon are and prioritize management practices that preserve them.”
Journal
Science Advances
Article Title
Widespread ancient bedrock landslide deposits facilitate deep weathering for storage and access of organic carbon
Article Publication Date
12-Jun-2026
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