Ecologist: Up-And-Coming Forests Will Remain Important Carbon Sinks

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“There’s a conventional theory that aging forests, for a variety of reasons, store less carbon over time. We contend that that may be true in certain systems that are less species-rich. But in our forests in the Midwest, the tree species we will end up with are much different from what we started with,” said Peter Curtis, professor and chair of evolution, ecology and organismal biology at Ohio State and a lead investigator on this research.

“We argue that in this case, as forests age, they get rejuvenated with younger individuals of different species – a more complex and diverse community will be replacing the old guard. They may even outdo the boomer generation and be more productive.”

Curtis and colleagues base their predictions on preliminary findings from a project in which they have accelerated the generational shift in part of a forest in northern Michigan. By cutting strips of bark from thousands of aspen trees to hasten their death, the scientists are able to observe the characteristics of the trees that will replace this 100-year-old cohort.

So far, the scientists are finding that the canopy created by the newcomers’ leaves use light more efficiently to manufacture carbohydrates and release oxygen through photosynthesis than did the aspen canopy that preceded it. The researchers also are able to use sophisticated instruments to quantify nitrogen cycling in the transitioning forest, and observe that nitrogen losses throughout the system are small even with the death of thousands of trees. As long as nitrogen remains available – within tree wood and leaves as well as in the soil – for the trees to renew themselves annually, the forest will continue to function as an effective carbon sink.

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