Streams and Their Hyporheic Zones Substantially Influence Carbon Export from Pacific Northwestern Headwater Streams
Headwater streams comprise nearly 90 percent of the total length of perennial stream channels, worldwide. Algae and other organisms in these streams generate and remove carbon through in-stream primary production and respiration. Additionally, microbes in the hyporheic zone convert terrestrial organic carbon into carbon dioxide which is subsequently released to the atmosphere. Despite their potential importance, headwater streams are often neglected in global carbon budgets. Scientists measured these processes in detail in a stream draining a 96 hectares (237 acres) forested watershed in the H.J. Andrews Experimental Forest in western Oregon. They found that this small headwater stream, which represents only 0.4 percent of the watershed area, is a significant exporter of carbon to the atmosphere and river network to which it is connected. Because headwater streams are approximately 90 percent of the total global river length, small streams collectively might substantially contribute to the transformation and export of carbon with repercussions for the global carbon cycle.
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