Level 1 — Absolute Beginner
Scientists studied oak trees and found something surprising. Oak trees keep taking in carbon dioxide from the air even after they stop growing for the year.
Plants use sunlight to make food from carbon dioxide and water. This is called photosynthesis. People used to think trees only did this while they were growing new wood.
But the new study shows oak trees keep doing photosynthesis for months after their growth stops. At some places, this was up to 36 percent of all the carbon the tree took in that year.
This matters because trees help fight climate change by storing carbon. If growth and photosynthesis are not as connected as scientists thought, forests might store less carbon as wood than we expected.
- carbon dioxide
- a gas in the air that plants use to make food
- photosynthesis
- the process plants use to turn sunlight into food
- deciduous
- a type of tree that loses its leaves each year
- wood (growth)
- the hard material that makes up a tree's trunk and branches
- absorb
- to take something in
- climate change
- long-term changes in the Earth's weather patterns
- store (carbon)
- to keep something held inside, such as carbon in wood
- estimate
- to guess a number based on available information
Level 2 — Elementary
A new study published in Science Advances reveals that deciduous oak trees keep photosynthesizing and absorbing carbon dioxide for months after their annual wood growth has ended.
The research, titled 'Decoupled carbon assimilation and growth responses to aridity in temperate deciduous oaks,' tracked oak trees at sites in the eastern United States and California. At the eastern sites, growth typically ran from May through July, yet the trees kept photosynthesizing well into October, with roughly 36 percent of their yearly carbon uptake occurring after growth had already stopped.
At the California sites, oak growth ran from December through April and slowed by midsummer, but photosynthesis again continued afterward, accounting for about 26 percent of those trees' annual carbon intake.
The findings challenge a long-held assumption that photosynthesis and wood production move in lockstep, suggesting instead that the two processes are more loosely connected than previously believed, with implications for how much carbon forests actually lock away in wood.
- deciduous
- losing leaves annually, typically in autumn
- assimilation (biology)
- the process of absorbing and incorporating nutrients or carbon
- aridity
- dryness, especially a lack of rainfall
- temperate
- relating to a mild climate zone, neither very hot nor very cold
- annual (adjective)
- occurring once every year
- long-held
- believed for a long time
- lockstep
- moving together in exact coordination
- implication
- a likely consequence or effect of something
Level 3 — Intermediate
A study published in Science Advances, titled 'Decoupled carbon assimilation and growth responses to aridity in temperate deciduous oaks,' finds that oak trees continue photosynthesizing and drawing down atmospheric carbon dioxide for months after their annual wood growth ceases.
Researchers tracked oaks across sites in the eastern United States and California, discovering markedly different seasonal rhythms. At the eastern sites, radial growth generally proceeded from May through July, yet photosynthetic activity persisted well into October, with approximately 36 percent of the trees' annual carbon assimilation occurring after growth had already concluded.
At the California sites, by contrast, growth began in December and continued through April before tapering by midsummer, even as photosynthesis carried on afterward, accounting for roughly 26 percent of those trees' total annual carbon uptake.
The results undercut the long-standing assumption that photosynthesis and wood production are tightly coupled processes, indicating instead a considerable degree of decoupling with direct implications for climate modeling, since models that assume synchronized growth and carbon fixation may systematically overestimate how much carbon temperate forests ultimately sequester as woody biomass.
- assimilation
- the biological process of taking in and using a substance, such as carbon
- radial growth
- the outward growth of a tree trunk, increasing its diameter
- persisted
- continued to exist or occur over time
- tapering (verb)
- gradually decreasing
- undercut (figurative)
- to weaken or challenge the basis of an argument
- decoupling
- separating processes previously assumed to move together
- synchronized
- happening at the same time or rate
- sequester (carbon)
- to capture and store carbon long-term, removing it from the atmosphere
Level 4 — Advanced
A study published in Science Advances, titled 'Decoupled carbon assimilation and growth responses to aridity in temperate deciduous oaks,' demonstrates that oak trees continue photosynthesizing and drawing down atmospheric carbon dioxide for months after their annual radial growth has concluded.
Researchers tracked oaks across sites in the eastern United States and California, uncovering markedly divergent seasonal rhythms. At the eastern sites, radial growth generally proceeded from May through July, yet photosynthetic activity persisted well into October, with approximately 36 percent of the trees' annual carbon assimilation transpiring after growth had already ceased.
At the California sites, by contrast, growth commenced in December and continued through April before tapering by midsummer, even as photosynthesis carried on thereafter, accounting for roughly 26 percent of those trees' aggregate annual carbon uptake.
The results substantially undercut the long-standing assumption that photosynthesis and wood production constitute tightly coupled processes, revealing instead a considerable degree of decoupling with direct ramifications for climate modeling, since models predicated on synchronized growth and carbon fixation may systematically overestimate the quantity of carbon temperate forests ultimately sequester as woody biomass.
- divergent
- differing or developing in different directions
- transpiring (figurative)
- happening or occurring
- commenced
- began
- aggregate
- formed by combining several elements into a total
- ramifications
- consequences, often complex or far-reaching
- predicated
- based on or founded upon an assumption
- woody biomass
- the total mass of wood material produced by plants
- substantially
- to a great or significant extent
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