Journal Article

Timing and duration of European larch growing season along altitudinal gradients in the Swiss Alps

Lea Moser, Patrick Fonti, Ulf Büntgen, Jan Esper, Jürg Luterbacher, Julia Franzen and David Frank

in Tree Physiology

Volume 30, issue 2, pages 225-233
Published in print February 2010 | ISSN: 0829-318X
Published online December 2009 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpp108
Timing and duration of European larch growing season along altitudinal gradients in the Swiss Alps

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The 2007 European larch (Larix decidua Mill.) growing season was monitored along two elevational transects in the Lötschental valley in the Swiss Alps. Phenological observations and weekly microcore sampling of 28 larch trees were conducted between April and October 2007 at seven study sites regularly spaced from 1350 to 2150  m a.s.l. on northwest- and southeast-facing slopes. The developmental stages of nearly 75,000 individual cells assessed on 1200 thin sections were used to investigate the links between the trees’ thermal regimes and growth phases including the beginning and ending of cell enlargement, wall thickening and maturation of the stem wood. Needles appeared ~3–4 weeks earlier than stem growth. The duration of ring formation lasted from mid-May to the end of October, with the length of the growing season decreasing along elevation from 137 to 101 days. The onset of the different growing seasons changed by 3–4 days per 100  m elevation; the ending of the growing season, however, appeared minimally related to altitude. If associated with the monitored altitudinal lapse rate of −0.5  °C per 100 m, these results translate into a lengthening of the growing season by ~7  days per degree Celsius. This study provides new data on the timing and duration of basic growth processes and contributes to quantification of the impacts of global warming on tree growth and productivity.

Keywords: elevational transect; forest growth; growing season length; phenology; temperature lapse rate; xylogenesis

Journal Article.  4678 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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