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  • Thumbnail for Effects of Wildfire on Biogeochemical Cycling in Ponderosa Pine Ecosystems
    Effects of Wildfire on Biogeochemical Cycling in Ponderosa Pine Ecosystems by Sherman, Ross Burchenal

    The frequency and severity of wildfires in the western United States is increasing, due primarily to a warming climate and unnaturally dense forests caused by policies of fire suppression. Ponderosa pine ecosystems, which historically have been subjected to mostly low severity ground fires, are now experiencing a drastically different fire regime. Carbon and nitrogen stocks, base cations, and strong acid anions were analyzed in response to wildfire severity in the Hayman and Waldo Canyon burn scars, located northeast of Colorado Springs, CO. Results show signs of persisting ecosystem disturbance twelve years after the Hayman Fire occurred, and two years after the Waldo Canyon Fire. Most notably, we observed depleted stocks of carbon and nitrogen in soil samples, as well as decreasing dissolved organic carbon (DOC) in response to percent of watershed disturbed. Base cations (K+, Na+, Mg2+, Ca2+) and sulfate (SO42-) were generally found to increase in response to percent burned at the less severe burn parameters, while nitrate showed a significant positive response to percent of watershed burned at high severity. These relationships suggest that ponderosa pine ecosystems are regenerating more slowly in response to this more severe fire regime, and questions remain about the forests’ ability to act as a reliable carbon sink.