Soil N mineralization and nitrification in relation to nitrogen solution chemistry in a small forested watershed |
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Authors: | Alan R. Hill Michael Shackleton |
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Affiliation: | (1) Department of Geography, York University, Toronto, Ontario, M3J 1P3, Canada |
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Abstract: | Spatial variations in soil processes regulating mineral N losses to streams were studied in a small watershed near Toronto, Ontario. Annual net N mineralization in the 0–8 cm soil was measured in adjacent upland and riparian forest stands using in situ soil incubations from April 1985 to 1987. Mean annual rates of soil N mineralization and nitrification were higher in a maple soil (93.8 and 87.0 kg.ha–1) than in a pine soil (23.3 and 8.2 kg.ha–1 ). Very low mean rates of mineralization (3.3 kg.ha–1) and nitrification (3.4 kg.ha–1) were found in a riparian hemlock stand. Average NO3-N concentrations in soil solutions were 0.3–1.0 mg.L–1 in the maple stand and >0.06mg.L–1 in the pine stand. Concentrations of NO3–N in shallow ground water and stream water were 3–4× greater in a maple subwatershed than in a pine subwatershed. Rapid N uptake by vegetation was an important mechanism reducing solution losses of NO3–N in the maple stand. Low rates of nitrification were mainly responsible for negligible NO3–N solution losses in the pine stand. |
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Keywords: | nitrogen mineralization nitrate nitrification soil water ground water streams |
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