title: Effects of atmospheric ammonia and ammonium sulphate on Douglas fir (Pseudotsuga menziesii).
abstract: Three-year-old Douglas firs (Pseudotsuga menziesii) were fumigated with 180 microg m(-3) NH3 or clean (charcoal-filtered) air. During these fumigations the plants received 15 mm artificial rain weekly, supplemented with 20, 500 or 2500 micromol litre(-1) (NH4)2SO4. Exposure to NH3 and NH4+ for 14 weeks resulted in a change of the nutrient status of the needles. The most remarkable effect was the increase in the N/K ratio, due to both uptake of N and leaching of K. The action of NH3 was stronger than that of NH4+. Both NH3 and (NH4)2SO4 affected the epicuticular wax layer and decreased mycorhiza frequency. Following fumigation and artificial rain treatments, needles were incubated for 8 h in a medium containing 0, 50, 250, 500 and 2500 micromol litre(-1) (NH4)2SO4. Almost no exchange of Ca, Mg and K for NH4+ was found. Therefore this ion exchange probably explains only a minor part of the changes in nutrient status of the whole trees.
authors.affiliation: Research Institute for Plant Protection, Department of Ecology, PO Box 9060, 6700 GW Wageningen, The Netherlands.
authors.forename: L J
authors.initials: LJ
authors.lastname: Van der Eerden
authors.forename: L J
authors.initials: LJ
authors.lastname: Lekkerkerk
authors.forename: S M
authors.initials: SM
authors.lastname: Smeulders
authors.forename: A E
authors.initials: AE
authors.lastname: Jansen