<p><strong>Project Overview</strong></p><p>Re-growing forests across the North Temperate Zone presently remove about 15% of fossil fuel carbon dioxide (CO₂) emissions. &nbsp; It is unclear, however, how long and to what extent these forests will continue to sequester CO₂ and thereby offset a major fraction of human-derived CO₂ emissions. Recent measurements suggest that, in contrast to the long-held idea that ecosystem CO₂&nbsp; uptake declines to zero with time, forests can continue storing carbon for centuries after establishment. Changes in nitrogen cycling patterns and rates are needed, however, to support tree growth and carbon storage as forests shift from dominance by early to late successional tree species. <img alt="Zoomed image of a mushroom" src="/research/sites/default/files/forestResearch_nitrogenCycling.jpg" style="width: 275px; margin: 5px; float: right; height: 206px;" title="Nitrogen Cycling at the University of Michigan Biological Station" />This project investigates mechanisms by which nitrogen cycling limits or enhances carbon uptake using stable nitrogen isotope studies in a 72-acre experimental forest in northern Michigan where losses of maturing, early successional tree species are being accelerated by stem girdling. Carbon uptake by the experimental forest is being compared to a nearby non-manipulated forest using biometric and atmospheric measurements by collaborators under separate funding. The NSF-supported research here focuses on nitrogen exchanges between late-successional tree species, their fungal symbionts and soils as they control forest carbon balances.<br /><br /> Results will provide a more complete understanding of controls on forest growth across successional stages and will improve predictions of temperate forest CO2 uptake and carbon balances. The study will serve as a resource for &ldquo;K-Gray&rdquo; environmental education and insights derived from this research will inform decisions of policymakers and resource managers regarding forest carbon sequestration and provision of ecosystem services.&nbsp;</p>