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Reduced early growing season freezing resistance in alpine treeline plants under elevated atmospheric CO 2
Author(s) -
MARTIN MELISSA,
GAVAZOV KONSTANTIN,
KÖRNER CHRISTIAN,
HÄTTENSCHWILER STEPHAN,
RIXEN CHRISTIAN
Publication year - 2010
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2009.01987.x
Subject(s) - vaccinium myrtillus , phenology , vaccinium , growing season , bilberry , scots pine , biology , botany , horticulture , pinus <genus>
Abstract The frequency of freezing events during the early growing season and the vulnerability to freezing of plants in European high‐altitude environments could increase under future atmospheric and climate change. We tested early growing season freezing sensitivity in 10 species, from four plant functional types (PFTs) spanning three plant growth forms (PGFs), from a long‐term in situ CO 2 enrichment (566 vs. 370 ppm) and 2‐year soil warming (+4 K) experiment at treeline in the Swiss Alps (Stillberg, Davos). By additionally tracking plant phenology, we distinguished indirect phenology‐driven CO 2 and warming effects from direct physiology‐related effects on freezing sensitivity. The freezing damage threshold (lethal temperature 50) under ambient conditions of the 10 treeline species spanned from −6.7±0.3 °C ( Larix decidua ) to −9.9±0.6 °C ( Vaccinium gaultherioides ). PFT, but not PGF, explained a significant amount of this interspecific variation. Long‐term exposure to elevated CO 2 led to greater freezing sensitivity in multiple species but did not influence phenology, implying that physiological changes caused by CO 2 enrichment were responsible for the effect. The elevated CO 2 effect on freezing resistance was significant in leaves of Larix, Vaccinium myrtillus , and Gentiana punctata and marginally significant in leaves of Homogyne alpina and Avenella flexuosa . No significant CO 2 effect was found in new shoots of Empetrum hermaphroditum or in leaves of Pinus uncinata, Leontodon helveticus, Melampyrum pratense , and V. gaultherioides . Soil warming led to advanced leaf expansion and reduced freezing resistance in V. myrtillus only, whereas Avenella showed greater freezing resistance when exposed to warming. No effect of soil warming was found in any of the other species. Effects of elevated CO 2 and soil warming on freezing sensitivity were not consistent within PFTs or PGFs, suggesting that any future shifts in plant community composition due to increased damage from freezing events will likely occur at the individual species level.