title: Decline of acid-sensitive plant species in heathland can be attributed to ammonium toxicity in combination with low pH.
abstract: The effects of increasing ammonium concentrations in combination with different pH levels were studied on five heathland plant species to determine whether their occurrence and decline could be attributed to ammonium toxicity and/or pH levels. Plants were grown in growth media amended with four different ammonium concentrations (10, 100, 500 and 1000 micromol l(-1)) and two pH levels resembling acidified (pH 3.5 or 4) and weakly buffered (pH 5 or 5.5) situations. Survival of Antennaria dioica and Succisa pratensis was reduced by low pH in combination with high ammonium concentrations. Biomass decreased with increased ammonium concentrations and decreasing pH levels. Internal pH of the plants decreased with increasing ammonium concentrations. Survival of Calluna vulgaris, Deschampsia flexuosa and Gentiana pneumonanthe was not affected by ammonium. Moreover, biomass increased with increasing ammonium concentrations. Biomass production of G. pneumonanthe reduced at low pH levels. A decline of acid-sensitive species in heathlands was attributed to ammonium toxicity effects in combination with a low pH.
authors.affiliation: Section of Aquatic Ecology and Environmental Biology, Department of Ecology, Nijmegen University, Toernooiveld 1, 6525 ED, Nijmegen, the Netherlands. l.vandenberg@science.ru.nl
authors.forename: Leon J L
authors.initials: LJ
authors.lastname: van den Berg
authors.forename: Edu
authors.initials: E
authors.lastname: Dorland
authors.forename: Philippine
authors.initials: P
authors.lastname: Vergeer
authors.forename: Miron A C
authors.initials: MA
authors.lastname: Hart
authors.forename: Roland
authors.initials: R
authors.lastname: Bobbink
authors.forename: Jan G M
authors.initials: JG
authors.lastname: Roelofs
mesh_terms: D018533:Biomass; D017753:Ecosystem; D006863:Hydrogen-Ion Concentration; D019684:Magnoliopsida / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development; D018520:Plant Shoots / Q000254:growth & development; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000633:toxicity*; D012987:Soil / Q000032:analysis; D013045:Species Specificity; D013997:Time Factors
chemical_list: D000644:Quaternary Ammonium Compounds; D012987:Soil