title: Experimental field estimation of organic nitrogen formation in tree canopies.
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)).
authors.affiliation: Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK. jnc@ceh.ac.uk
authors.forename: J N
authors.initials: JN
authors.lastname: Cape
authors.forename: L J
authors.initials: LJ
authors.lastname: Sheppard
authors.forename: A
authors.initials: A
authors.lastname: Crossley
authors.forename: N
authors.initials: N
authors.lastname: van Dijk
authors.forename: Y S
authors.initials: YS
authors.lastname: Tang
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D000397:Air Pollution / Q000706:statistics & numerical data; D000641:Ammonia / Q000737:chemistry; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D028222:Picea / Q000737:chemistry / Q000378:metabolism; D028223:Pinus / Q000737:chemistry / Q000378:metabolism; D011891:Rain / Q000737:chemistry; D013223:Statistics as Topic; D014197:Trees / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D000641:Ammonia; D009584:Nitrogen