At the top of the forest

In the news you might hear stories about carbon offsets, especially in the context of tree planting. How do scientists actually know how much carbon a forest is using? One of the major methods uses an eddy flux tower, which is what you see here. Dozens of meters above the forest floor, on a precarious scaffolding, are delicate instruments that measure wind speed, temperature, and carbon dioxide levels. By knowing the speed of the wind and a few properties of the atmosphere, scientists can estimate how much carbon dioxide is leaving or entering the forest. This lets us understand the role plants are playing in the global carbon cycle. Of course, instantaneous measurements of carbon gained and carbon lost are just part of the pictures – longer term studies have to also account for the decomposition of wood, the respiration of the soil, and many other factors. And more importantly, a forest is not just carbon – the services it provides to people extend far beyond carbon storage to things such as provisioning of clean water, buffering of stormwater runoff, maintenance of animal diversity, and so on.

Standing at the top of one of these towers you feel at home in the highest branches of the trees, with birds all around. But it’s not an experience for the queasy – these towers are built just strong enough to permit maintenance, so they sway in a several-foot radius if the wind picks up!

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