Tracking how energy flows within and across ecosystems is imperative for understanding interactions among biogeochemical cycles. Aquatic ecosystem metabolism is inextricably linked to the terrestrial landscape, with many lakes getting over 50% of their carbon from terrestrial sources. Nonetheless, there are few large scale measurements of actual carbon export from terrestrial ecosystems. Instead, scientists have relied on a mass balance approach to estimate the quantity of carbon coming into aquatic ecosystems based on estimates of riverine carbon delivery to the ocean. This approach has left many unanswered questions related to the controls on terrestrial organic matter export, both in terms of quantity and quality. Here I used Water Extractable Organic Carbon (WEOC) to estimate potential terrestrial carbon export and to understand the mechanisms controlling these exports. Results from extractions performed at 19 grassland sites across the United States suggested that 1-5% of their total soil carbon was in the water extractable organic carbon pool. In addition, this work suggested that soils selectively retained nitrogen and phosphorus, with less organic nutrient export relative to organic carbon to aquatic ecosystems. These data demonstrated the usefulness of measuring water extractable organic matter (WEOM) on broad spatial scales to gain a better understanding of both the amounts and types of organic matter that are available for export from terrestrial ecosystems.
University of Minnesota M.S. thesis. February 2015. Major: Water Resources Science. Advisor: Dr. James B. Cotner. 1 computer file (PDF); v, 39 pages.
Thompson, Seth K..
Extractability of carbon, nitrogen, and phosphorus in United States grasslands.
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