Variable temperature effects of Open Top Chambers at polar and alpine sites explained by irradiance and snow depth

• Published in: Global Change Biology
• Main Authors: Bokhorst, Stef, Huiskes, Ad, Aerts, Rien, Convey, Peter, Cooper, Elisabeth J., Dalen, Linda, Erschbamer, B., Gudmundsson, Jon, Hofgaard, Annika, Hollister, Robert D., Johnstone, Jill, Jonsdottir, Ingibjorg S., Lebouvier, Marc, Van De Vijver, Bart, Wahren, Carl-Henrik, Dorrepaal, Ellen
• Other Authors: Department of Animal and Plant Sciences Sheffield, University of Sheffield Sheffield, Netherlands Institute of Ecology, Dept of Systems Ecology, University of Amsterdam Amsterdam (UvA), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Arctic and Marine Biology, University of Tromsø (UiT), Division of Biodiversity and Climate Change, Directorate for Nature Management, Institute of Botany Innsbruck, University of Innsbruck, Agricultural University of Iceland, Norwegian Institute for Nature Research (NINA), Grand Valley State University, University of Saskatchewan Saskatoon (U of S), University of Iceland Reykjavik, Ecosystèmes, biodiversité, évolution Rennes (ECOBIO), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Department of Bryophyta and Thallophyta - National Botanic Garden of Belgium, National Botanic Garden of Belgium, Research Centre for Applied Alpine Ecology, La Trobe University Melbourne, Climate Impacts Research Centre (CIRC), Umeå University, NOSR; BAS; European Commission; Norwegian Svalbard Soc.; NPI; Univ Innsbruck; Club Allegra Munich; IPEV, projet TARANTELLA
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: alpine; Antarctic; Arctic; climate change; extreme weather; freeze-thaw; PAR; snow; temperature variation; tundra; warming experiment; wind; geo; envir; Antarc*; Climate change; Tundra
• Online Access: https://doi.org/10.1111/gcb.12028; https://hal.archives-ouvertes.fr/hal-00780688

International audience Environmental manipulation studies are integral to determining biological consequences of climate warming. Open Top Chambers (OTCs) have been widely used to assess summer warming effects on terrestrial biota, with their effects during other seasons normally being given less attention even though chambers are often deployed year-round. In addition, their effects on temperature extremes and freeze-thaw events are poorly documented. To provide robust documentation of the microclimatic influences of OTCs throughout the year, we analysed temperature data from 20 studies distributed across polar and alpine regions. The effects of OTCs on mean temperature showed a large range ( 0.9 to 2.1 °C) throughout the year, but did not differ significantly between studies. Increases in mean monthly and diurnal temperature were strongly related (R2 = 0.70) with irradiance, indicating that PAR can be used to predict the mean warming effect of OTCs. Deeper snow trapped in OTCs also induced higher temperatures at soil/vegetation level. OTC-induced changes in the frequency of freeze- thaw events included an increase in autumn and decreases in spring and summer. Frequency of high- temperature events in OTCs increased in spring, summer and autumn compared with non-manipulated control plots. Frequency of low-temperature events was reduced by deeper snow accumulation and higher mean temperatures. The strong interactions identified between aspects of ambient environmental conditions and effects of OTCs suggest that a detailed knowledge of snow depth, temperature and irradiance levels enables us to predict how OTCs will modify the microclimate at a particular site and season. Such predictive power allows a better mechanistic understanding of observed biotic response to experimental warming studies and for more informed design of future experiments. However, a need remains to quantify OTC effects on water availability and wind speed (affecting, for example, drying rates and water stress) in combination with ...