The interaction between xylem phenology and climate assesses forest growth and productivity and carbon storage across biomes under changing environmental conditions. We tested the hypothesis that patterns of wood formation are maintained unaltered despite the temperature changes across cold ecosystems. Wood microcores were collected weekly or biweekly throughout the growing season for periods varying between 1 and 13 years during 1998-2014 and cut in transverse sections for assessing the onset and ending of the phases of xylem differentiation. The data set represented 1321 trees belonging to 10 conifer species from 39 sites in the Northern Hemisphere and covering an interval of mean annual temperature exceeding 14 K. The phenological events and mean annual temperature of the sites were related linearly, with spring and autumnal events being separated by constant intervals across the range of temperature analysed. At increasing temperature, first enlarging, wall-thickening and mature tracheids appeared earlier, and last enlarging and wall-thickening tracheids occurred later. Overall, the period of wood formation lengthened linearly with the mean annual temperature, from 83.7 days at -2 °C to 178.1 days at 12 °C, at a rate of 6.5 days °C-1 . April-May temperatures produced the best models predicting the dates of wood formation. Our findings demonstrated the uniformity of the process of wood formation and the importance of the environmental conditions occurring at the time of growth resumption. Under warming scenarios, the period of wood formation might lengthen synchronously in the cold biomes of the Northern Hemisphere.

Biotechnical Faculty University of Ljubljana Jamnikarjeva 101 Ljubljana 1000 Slovenia

Département des Sciences Fondamentales Université du Québec à Chicoutimi 555 boulevard de l'Université Chicoutimi QC G7H 2B1 Canada

Department of Agricultural Sciences University of Naples Federico 2 Corso Umberto 1 Napoli 80138 Italy

Department of Physical Geography and Geoecology Charles University Prague Ovocný trh 3 5 Prague 116 36 Czech Republic

Dipartimento Territorio e Sistemi Agro Forestali Università degli Studi di Padova Legnaro 2 35122 PD Italy

Institute of Botany Leopold Franzens University of Innsbruck Sternwartestrasse 15 Innsbruck 6020 Austria

Key Laboratory of Alpine Ecology and Biodiversity Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100101 China

Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems South China Botanical Garden Chinese Academy of Sciences 723 Xingke Road Tianhe District Guangzhou 510650 China

LERFoB INRA AgroParisTech F 54000 Nancy France

Natural Resources Institute Finland PO Box 18 Vantaa 01301 Finland

Oeschger Centre for Climate Change Research Bern CH 3012 Switzerland

Provincial Key Laboratory of Applied Botany South China Botanical Garden Chinese Academy of Sciences 723 Xingke Road Tianhe District Guangzhou 510650 China

Slovenian Forestry Institute Vecna pot 2 Ljubljana 1000 Slovenia

Swiss Federal Research Institute WSL Birmensdorf CH 8903 Switzerland

Citace poskytuje Crossref.org

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