Luca Bragazza1, Teemu Tahvanainen2, Lado Kutnar3, Håkan Rydin4, Juul Limpens5, Michal Hájek6, Philippe Grosvernier7, Tomáš Hájek8, Petra Hajkova6, Ina Hansen9, Paola Iacumin10, Renato Gerdol1. 1. Department of Natural and Cultural Resources, University of Ferrara, Corso Porta Mare 2, I-44100 Ferrara, Italy. 2. Department of Biology, University of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland. 3. Slovenian Forestry Institute, Department of Forest Ecology, Večna pot 2, SI-1000 Ljubljana, Slovenia. 4. Department of Plant Ecology, Evolutionary Biology Centre, Uppsala University, Villavägen 14, SE-75236 Uppsala, Sweden. 5. Department of Environmental Sciences, Wageningen University, Bornsesteeg 69, 6708 PD Wageningen, The Netherlands. 6. Department of Botany, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic. 7. LIN'eco, Ecological Engineering, PO Box 51, 2732 Reconvilier, Switzerland. 8. Faculty of Biological Sciences, Branišovskă 31, CZ-370 05 České Bud ě jovice, Czech Republic. 9. Department of Ecology, The Royal Veterinary and Agricultural University, Rolighedsvej 21, 1958 Frederiksberg, Denmark. 10. Department of Earth Sciences, University of Parma, Parco Area delle Scienze 157, I-43100 Parma, Italy.
Abstract
• We studied the effects of increasing levels of atmospheric nitrogen (N) deposition on nutrient limitation of ombrotrophic Sphagnum plants. • Fifteen mires in 11 European countries were selected across a natural gradient of bulk atmospheric N deposition from 0.1 to 2 g/m2 year-1 . Nutritional constraints were assessed based on nutrient ratios of N, phosphorus (P), and potassium (K) in Sphagnum plants collected in hummocks (i.e. relatively drier microhabitats) and in lawns (i.e. relatively wetter microhabitats). • Nutrient ratios in Sphagnum plants increased steeply at low atmospheric N input, but above a threshold of N deposition of c. 1 g/m2 year-1 the N : P and N : K ratios tended to saturation. Increasing atmospheric N deposition was also accompanied by a reduced retention of Ca and Mg in Sphagnum plants and a decreased stem volumetric density in hummock Sphagnum plants. • We suggest a critical load of N deposition in Europe of 1 g/m2 year-1 above which Sphagnum plants change from being N-limited to be K + P colimited, at N : P > 30 and N : K > 3.
• We studied the effects of increasing levels of atmospheric n class="Chemical">nitrogen (N) deposition on nutrient limitation of ombrotrophic Sphagnpan>um plants. • Fifteen mires inpan> 11 European countries were selected across a natural gradient of bulk atmospheric N deposition from 0.1 to 2 g/m2 year-1 . Nutritional constrainpan>ts were assessed based on nutrient ratios of N, n class="Chemical">phosphorus (P), and potassium (K) in Sphagnum plants collected in hummocks (i.e. relatively drier microhabitats) and in lawns (i.e. relatively wetter microhabitats). • Nutrient ratios in Sphagnum plants increased steeply at low atmospheric N input, but above a threshold of N deposition of c. 1 g/m2 year-1 the N : P and N : K ratios tended to saturation. Increasing atmospheric N deposition was also accompanied by a reduced retention of Ca and Mg in Sphagnum plants and a decreased stem volumetric density in hummock Sphagnum plants. • We suggest a critical load of N deposition in Europe of 1 g/m2 year-1 above which Sphagnum plants change from being N-limited to be K + P colimited, at N : P > 30 and N : K > 3.
Authors: O E Sala; F S Chapin; J J Armesto; E Berlow; J Bloomfield; R Dirzo; E Huber-Sanwald; L F Huenneke; R B Jackson; A Kinzig; R Leemans; D M Lodge; H A Mooney; M Oesterheld; N L Poff; M T Sykes; B H Walker; M Walker; D H Wall Journal: Science Date: 2000-03-10 Impact factor: 47.728