Experimental field estimation of organic nitrogen formation in tree canopies |
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Authors: | J.N. Cape L.J. Sheppard A. Crossley N. van Dijk Y.S. Tang |
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Affiliation: | Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK |
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Abstract: | The content of organic N has been shown in many studies to increase during the passage of rain water through forest canopies. The source of this organic N is unknown, but generally assumed to come from canopy processing of wet or dry-deposited inorganic N. There have been very few experimental studies in the field to address the canopy formation or loss of organic N. We report two studies: a Scots pine canopy exposed to ammonia gas, and a Sitka spruce canopy exposed to ammonium and nitrate as wet deposition. In both cases, organic N deposition in throughfall was increased, but only represented a small fraction (<10%) of the additional inorganic N supplied, suggesting a limited capacity for net organic N production, similar in both conifer canopies under Scottish summertime conditions, of less than 1.6 mmol N m−2 mth−1 (equivalent to 3 kg N ha−1 y−1). |
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Keywords: | Organic nitrogen Wet deposition Dry deposition Throughfall Nitrogen budget |
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