Cambial phenology, wood formation and temperature thresholds in two contrasting years at high altitude in southern Italy
Annie Deslauriers (1, 2), Sergio Rossi (1, 3), Tommaso Anfodillo (1) and Antonio Saracino (4)
1. Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, viale dell’Università 16, 35020 Legnaro
(PD), Italy / 2. Corresponding author () / 3. INRA, UMR 1092 Laboratoire d’Étude des Ressources Forêt-Bois (LERFOB), 54000 Nancy, France / 4. Dipartimento di Arboricoltura, Botanica e Patologia Vegetale, Università di Napoli “Federico II”, via Università 100, 80055
Portici (NA), Italy / Received October 24, 2007; accepted December 21, 2007; published online April 1, 2008
Summary
Xylogenesis was monitored during 2003 and 2004 in a timberline environment in southern Italy to assess links between temperature,
cambial phenology and wood formation on a short-time scale. Wood microcores were collected weekly from May to October from
10 trees of Pinus leucodermis Ant., histological sections were cut with a rotary microtome and anatomical features of the developing and mature tracheids
were observed and measured along the growing tree ring. Spring 2003 was hotter than spring 2004, with temperatures up to 2.6
°C above historical means. The hotter conditions resulted in an earlier onset of cambial activity and all differentiation
phases of about 20 days, resulting in an increased duration of xylogenesis of about 23 days. Air and stem temperatures at
which xylogenesis had a 0.5 probability of being active were calculated with logistic regressions fitted on binary responses.
In both years, similar thresholds were estimated with daily mean values of 8.2 and 9.5 °C for air and stem temperatures, respectively.
The observed convergent responses of cambium phenology to temperature during the two contrasting springs confirm the key role
of this environmental factor in determining the onset and duration of wood formation in timberline areas. The intra-annual
dynamics of ring-width increase differed between years, with significantly narrower rings formed in 2004 than in 2003. These
differences were mainly related to cell size because larger earlywood tracheids were produced in 2003. This study demonstrates
the plasticity of tree-ring formation in response to high temperatures as a result of modifications in the onset and duration
of differentiation.
