04.16.2019

How inland waters 'breathe' carbon — and what it means for global systems

Journal of Geophysical Research: Biogeosciences, they conclude that these variances are likely due to the fact that forested streams tend to be steeper, creating greater turbulence that, in turn, promotes gas releases. Meanwhile, in wetland streams those inputs were more likely to be carried downstream farther from their source, said Kelly Aho, a doctoral candidate at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the study. “When you think about what a wetland looks like, it makes sense: wetlands are really flat, which is why water and organic matter may accumulate there,” Aho said. “As a result, during a rainstorm those wetlands and their soils are a source of greenhouse gases.” “But,” she added, “gas concentrations represent only half the equation.” The release of gases from rivers and streams also depends on the gas transfer velocity, or the rate at which gases move across the air-water boundary. A lack of turbulence tends to produce a lower gas transfer velocity and slower rates. So while greenhouse gas concentrations in wetland streams will increase suddenly during a rainstorm, those gases are more likely to remain trapped in the flatter, less turbulent streams until they encounter steeper terrain farther downstream. Understanding these dynamics, Aho said, will be critical in order to develop more accurate carbon cycle projections and climate models — particularly as extreme weather events are projected to increase in the coming decades. “If a researcher is looking at carbon sequestration from a local perspective, they might be just monitoring what goes in and out vertically within a plot of land,” she said. “But if that area includes a wetland stream, for instance, the gases are likely to flow away from the plot they’re looking at; the carbon may be released into the atmosphere outside of their point of view, so you may totally miss it. So it’s important to think about this idea of lateral transport. “That’s why streams and rivers are so interesting,” she added. “They’re moving solutes across the landscape, so we have to take that into account.”   This article appeared on the EurekAlert! website at https://www.eurekalert.org/pub_releases/2019-04/ysof-hi041619.php]]>

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