title: Growth and community responses of alpine dwarf shrubs to in situ CO₂ enrichment and soil warming.
abstract: • Rising CO₂ concentrations and the associated global warming are expected to have large impacts on high-elevation ecosystems, yet long-term multifactor experiments in these environments are rare. • We investigated how growth of dominant dwarf shrub species (Vaccinium myrtillus, Vaccinium gaultherioides and Empetrum hermaphroditum) and community composition in the understorey of larch and pine trees responded to 9 yr of CO₂ enrichment and 3 yr of soil warming at the treeline in the Swiss Alps. • Vaccinium myrtillus was the only species that showed a clear positive effect of CO₂ on growth, with no decline over time in the annual shoot growth response. Soil warming stimulated V. myrtillus growth even more than elevated CO₂ and was accompanied by increased plant-available soil nitrogen (N) and leaf N concentrations. Growth of Vaccinium gaultherioides and E. hermaphroditum was not influenced by warming. Vascular plant species richness declined in elevated CO₂ plots with larch, while the number of moss and lichen species decreased under warming. • Ongoing environmental change could lead to less diverse plant communities and increased dominance of the particularly responsive V. myrtillus in the studied alpine treeline. These changes are the consequence of independent CO₂ and soil warming effects, a result that should facilitate predictive modelling approaches.
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Alpine Ecosystems, Flüelastrasse 11, CH-7260 Davos, Switzerland.|Institute of Botany, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Dawes
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8093 Birmensdorf, Switzerland.
authors.forename: Frank
authors.initials: F
authors.lastname: Hagedorn
authors.affiliation: Institute of Botany, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zumbrunn
authors.affiliation: Centre d'Ecologie Fonctionnelle & Evolutive, CEFE-CNRS, 1919 Route de Mende, F-34293 Montpellier Cedex 5, France.
authors.forename: Ira Tanya
authors.initials: IT
authors.lastname: Handa
authors.affiliation: Centre d'Ecologie Fonctionnelle & Evolutive, CEFE-CNRS, 1919 Route de Mende, F-34293 Montpellier Cedex 5, France.
authors.forename: Stephan
authors.initials: S
authors.lastname: Hättenschwiler
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Alpine Ecosystems, Flüelastrasse 11, CH-7260 Davos, Switzerland.
authors.forename: Sonja
authors.initials: S
authors.lastname: Wipf
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Alpine Ecosystems, Flüelastrasse 11, CH-7260 Davos, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Rixen
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology*; D029791:Ericaceae / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D018515:Plant Leaves / Q000033:anatomy & histology; D018520:Plant Shoots / Q000254:growth & development; D012987:Soil / Q000737:chemistry; D013557:Switzerland; D013696:Temperature; D029796:Vaccinium / Q000254:growth & development / Q000502:physiology*
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D009584:Nitrogen