The effect fire frequency has on the passive carbon pool
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Because of the impact increased amounts of carbon dioxide are having on the climate, studying the global carbon cycle has generated significant concern and interest. Being one of the largest pools of carbon on the planet, stable soil organic matter (the passive carbon pool) held underground is important to study because of the potential soil may have to serve as a carbon reservoir. Never before has the passive pool been studied along a fire gradient with a long prescribed burn history. The passive carbon pool was quantified from an oak savanna in central Minnesota. Soil samples were collected from different annual prescribed burn plots part of an experiment that started in 1964 and fire frequencies ranging from 0.00-0.88 prescribed burn occurrences per year. Samples were also collected from nitrogen fertilizer (NH4NO3) enriched experiment gradient plots (0-50g/m2/year). Different physical and chemical fractionation methods were used to separate the passive carbon and the effectiveness to accurately isolate the pool was also analyzed. The passive carbon pool increased slightly with increased fire frequency (p- value= 0.319) and decreased with increasing nitrogen content (p- value= 6.77E-20). Also, chemical fractionation using hydrogen peroxide oxidation was very effective in removing fast cycling carbon. The results from this study showed that increase fire frequency did not significantly increase the size of the passive carbon pool and additional nitrogen in the soil decreased the passive carbon pool size.