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    Author(s): Mark E. Fenn; Mark A. Poth; Joseph D. Terry; Timothy J. Blubaugh
    Date: 2005
    Source: Canadian Journal of Forest Research 35:1464-1486
    Publication Series: Miscellaneous Publication
    PDF: Download Publication  (891 KB)


    Net fluxes of nitrogen (N) mineralization and nitrification were measured in situ on a monthly basis for 3 years at a high (HN) and low (LN) N deposition site in the San Bernardino Mountains, California. Mean N mineralization fluxes in the forest floor and top 10 cm of mineral soil were 19.0 and 59.8 kg N·ha–1·year–1 at LN and HN, respectively. Mean net nitrification fluxes were 11.2 and 55.9 kg N·ha–1·year–1 at LN and HN, respectively. Relative nitrification (the percent N mineralized that was nitrified) was generally lower under Pinus ponderosa Dougl. ex P. & C. Laws. (or Pinus jeffreyi Grev. & Balf.) canopies than under Quercus kelloggii Newb. or open canopies. The rate of net N mineralization was the key factor for predicting the rate of net nitrification. Fertilization with 50 and 150 kg N·ha–1 at LN significantly increased the rates of net mineralization and net nitrification. At HN fertilization had no significant effect on net nitrification. We conclude that at low-deposition sites increased nitrification occurs in the short term in response to added N, but that sustained elevated net nitrification is driven by the accumulation of N-enriched litter and soil organic matter in conjunction with chronic throughfall N deposition inputs.

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    Fenn, Mark E.; Poth, Mark A.; Terry, Joseph D.; Blubaugh, Timothy J. 2005. Nitrogen mineralization and nitrification in a mixed-conifer forest in southern California: controlling factors, fluxes, and nitrogen fertilization response at a high and low nitrogen deposition site. Canadian Journal of Forest Research 35:1464-1486

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