Carbon balance and tree growth in a Fagus sylvatica stand

Abstract

-The objectives of this study were 1) to scale photosynthesis from leaf to crown and to tree scale, 2) to determine the proportion of assimilated carbon used for wood construction and whether the fraction of assimilation used for production varies among social classes and 3) to validate the approach by comparing assimilation estimates with independent measurements provided by the eddy covariance technique (EC). Measurements (growth and gas exchange) were performed in a 30-year-old Fagus sylvatica stand during the 1997 growing season on five sample trees of different crown classes (dominant, codominant and intermediate trees). A nonlinear relationship between net CO 2 assimilation and photosynthetically active radiation (PAR) was found for each sample trees. Canopy net CO 2 assimilation was then modelled over a period of non limiting soil water soil water content. Simulated gross assimilation scaled to stand level was in good agreement with stand measurements performed by EC. growth / carbon balance / photosynthesis / crown class / Fagus sylvatica L Résumé -Bilan de carbone et croissance dans un jeune peuplement de Fagus sylvatica. Les objectifs de cette étude étaient 1) d'estimer la photosynthèse à l'échelle de la couronne, puis à l'échelle de l'arbre à partir de mesures foliaires, 2) de déterminer la proportion du carbone assimilé utilisée pour la construction de bois et sa variation en fonction du statut social de l'arbre, 3) de valider l'estimation de l'assimilation en la comparant à une mesure indépendante (technique des corrélations turbulentes, EC). Les mesures (croissance et échanges gazeux) ont été effectuées pendant la saison de végétation 1997 sur cinq hêtres de 30 ans de statuts sociaux différents (dominant, codominant et dominé). Une relation non linéaire entre l'assimilation nette de CO 2 et le rayonnement photosynthetiquement actif (PAR) a été établie pour chaque arbre échantillon. L'assimilation nette de CO 2 à l'échelle de la couronne a ensuite été estimée pour une période sans stress hydrique. L'estimation de l'assimilation brute à l'échelle du peuplement à partir de mesures foliaires est en bon accord avec des mesures effectuées à l'échelle du peuplement par EC. croissance / bilan de carbone / photosynthèse / statut social / Fagus sylvatica L

Root biomass and biomass increment in a beech (Fagus sylvatica L.) stand in North-East France

“…These plots were used to inventory the stand after 1996 and 1997 growing seasons by measuring the girth and height of all the trees of each plot. However, a complete tree girth inventory of all the trees in the experimental stand was also performed before 1996 growing season [24].…”

“…Examination of trees of each crown class allowed an estimation of the girths corresponding to the lower bounds of the dominant, codominant and intermediate tree classes. On this basis, the inventory of the total stand revealed the following distribution of trees among crown classes [24]: 19.8% dominant (crown class 1), 33.0% codominant (crown class 2), 21.0% intermediate (crown class 3) and 30.9% suppressed (crown class 4).…”

“…Several research projects are being conducted to study CO 2 fluxes for different forest types around the world [1]. This study is part of a cooperative research project in which measurements of CO 2 fluxes at the tree and stand levels are conducted in a beech stand to investigate the ecophysiological factors governing carbon uptake and growth of trees [24]. Biomass increment estimations are compared with the carbon balance resulting from photosynthesis and respiration processes in a companion paper [17].…”

Beech (Fagus sylvatica L.) branches show acclimation of xylem anatomy and hydraulic properties to increased light after thinning

“…There were three types of branches: (i) upper branches exposed to full sunlight (= sun-exposed branches), (ii) lower branches were heavily shaded in 1998 by upper crown branches and surrounding trees (= shade branches) and (iii) branches exposed directly to full sun after thinning in 1999 (= thinned branches). More details about the stand structure are published elsewhere [7,12,[14][15][16] and microclimate is characterised in table I for each treatment. Branch morphology, xylem anatomy and water relations were measured on the five trees accessible from towers.…”

Spatial and seasonal variations in stem respiration of beech trees (Fagus sylvatica)

“…Stem diameter increment in the crown started at the end of April in 1997 [22] and ceased approximately on 20 August (DOY 232). In 1998, growth started ca.…”