© 2007 Heron Publishing—Victoria, Canada
Six-year time course of light-use efficiency, carbon gain and growth of beech saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelterwood
Philippe Balandier (1, 2), Herve Sinoquet (3), Ela Frak (3, 4), Rita Giuliani (3, 5), Marc Vandame (3), Sylvestre Descamps (3), Lluis Coll (1, 6), Boris Adam (3), Bernard Prevosto (1, 7) and Thomas Curt (1, 7)
1. Cemagref of Clermont-Ferrand, Team of Applied Ecology of Woodlands, 24 avenue des Landais, BP 50085, F-63172 Aubière cedex,
France / 2. Corresponding author (philippe.balandier@cemagref.fr) / 3. INRA-Université Blaise Pascal, UMR PIAF, 234 avenue du Brézet, F-63100 Clermont-Ferrand, France / 4. Present address: INRA UEPF, B.P. 6, F-86600 Lusignan, France / 5. Present address: Dipartamento di Colture Arboree, University of Bologna, Viale Fanin 46, 40127 Bologna, Italy / 6. Present address: Centre Tecnològic Forestal de Catalunya, Catalonia, Pujada del Seminari s/n, 25280 Solsona, Spain / 7. Present address: Cemagref, Research Unit on Mediterranean Ecosystems and Risks, 3275 route Cézanne, CS 40061, F-13182 Aix-en-Provence,
France / Received June 6, 2006; accepted October 27, 2006; published online May 1, 2007
Summary
Two-year-old Fagus sylvatica L. saplings were planted under the cover of a Pinus sylvestris L. stand in the French Massif Central. The stand was differentially thinned to obtain a gradient of transmitted photosynthetically
active radiation (PARt; 0–0.35). Eighteen Fagus saplings were sampled in this gradient, and their growth (basal stem diameter increment) was recorded over six years. Over
the same period, morphological parameters (leaf area, number and arrangement in space) were monitored by 3D-digitization.
Photosynthetic parameters were estimated with a portable gas-exchange analyzer. Photosynthesis was mainly related to light
availability, whereas sapling morphology was mainly driven by sapling size. Annual stem diameter increment was related to
the amount of light-intercepting foliage (silhouette to total leaf area ratio (STAR) × total sapling leaf area (LA)) and light
availability above the saplings (PARt). However, light-use efficiency, i.e., the slope of the relationship between STAR × LA × PARt and stem diameter increment, decreased over time as a result of a relative decrease in the proportion of photosynthetic tissues
to total sapling biomass.
Keywords:
forest regeneration, leaf nitrogen content, photosynthetic parameters, silhouette to total leaf area ratio (STAR).
