Potential canopy influences on the isotopic composition of nitrogen and sulphur in atmospheric deposition

• Published in: Oecologia 1997-02, Vol.109 (4), p.600-607
• Main Authors: Heaton, T.H.E, Spiro, B, Robertson, S.M.C. (Natural Environment Research Council, Keyworth (United Kingdom). Isotope Geosciences Lab.)
• Format: Article
• Language: English
• Subjects: ABSORCION DE SUSTANCIAS NUTRITIVAS; ABSORPTION DE SUBSTANCES NUTRITIVES; AIR POLLUTION; Ammonia; Animal, plant and microbial ecology; Applied ecology; ATMOSFERA; ATMOSPHERE; Atmospherics; AZOTE; AZUFRE; Biological and medical sciences; CANOPY; CONIFERALE; CONIFERALES; COUVERT; CUBIERTA DE COPAS; Ecosystem Ecology; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Forest canopy; Fundamental and applied biological sciences. Psychology; Gases; ISOTOPE; ISOTOPES; ISOTOPOS; N/N S/S ratios; Nitrates; NITROGEN; Nitrogen sulphur isotopes; NITROGENO; Non agrochemicals pollutants; NUTRIENT UPTAKE; Phytopathology. Animal pests. Plant and forest protection; POLLUTION ATMOSPHERIQUE; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; POLUCION DEL AIRE; Quaternary ammonium compounds; Rain; SOUFRE; Sulfur; SULPHUR; Throughfall; Trees
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s004420050122

Isotopic studies of nitrogen and sulphur inputs to plant/soil systems commonly rely on limited published data for the15N/^{14}\text{N}$and34S/32S ratios of nitrate, ammonium and sulphate in rainfall. For systems with well-developed plant canopies, however, inputs of these ions from dry deposition or particulates may be more important than rainfall. The manner in which isotopic fractionation between ions and gases may lead to dry deposition and particulates having15N/^{14}\text{N}$or34S/32S ratios different from those of rainfall is considered. Data for rainfall and throughfall in coniferous plantations are then discussed, and suggest that: (1) in line with expectations, nitrate washed from the canopy has15N/^{14}\text{N}$ratios higher than those in rainfall; (2) the15N/^{14}\text{N}$ratios of ammonium washed from the canopy are variable, with high ratios being found for canopies of higher pH in conditions of elevated ambient ammonia gas concentrations; and (3) in accord with expectations and previous work,34S/32S ratios of sulphate washed from the canopy are not substantially different from those in rainfall. The study suggests that if atmospheric inputs are relevant to isotopic studies of the sources of nitrogen for canopied systems, then confident interpretation will require analysis of these inputs.