The effect of light acclimation of single leaves on whole tree growth and competition - an application of the tree growth model ALMIS

Abstract

-Black alder (Alnus glutinosa L. (Gaertn.)) is a light-demanding, fast growing tree species, widespread but always restricted to wet habitats. Because no sun and shade leaves can be distinguished within the alder crown, the question arises whether these specific photosynthetic characteristics may contribute to alder's low competitiveness. A functional-structural tree growth model ("ALMIS"), based on an object oriented approach, was developed and parameterized using data from extensive investigations of an alder forest in Northern Germany. The basic model structure is described, especially focusing on carbon dynamics. ALMIS was used to study the effects of light acclimation of single leaves on whole plant growth and competition. Different photosynthetic types were simulated to grow either in isolation or in competition which each other. When grown in isolation over an extended period, a model tree with exclusively shade leaves accumulated less total biomass than one with exclusively sun leaves, but a tree with the capacity to acclimate the leaves to the low light conditions in the inner crown grew the most. Inter-tree competition enhanced the advantage of leaf acclimation for whole plant growth.functional-structural growth model / photosynthesis / acclimation / shade leaves / Alnus glutinosa Résumé -Effets de l'adaptation des feuilles à la lumière sur la croissance globale de l'arbre et la compétition -une application du modèle de croissance ALMIS. L'Aulne noir (Alnus glutinosa L. (Gaertn.)) est une espèce à croissance rapide exigeante en lumière. Elle est répandue, mais toujours localisée aux habitats humides. Comme il n'est pas possible de différencier dans la canopée les feuilles d'ombre de celles de lumière, la question se pose de savoir si ses caractéristiques photosynthétiques peuvent contribuer à la faible compétitivité de l'Aulne. Un modèle de croissance à fonction structurelle (ALMIS), basé sur l'approche orientée objet, a été développé et paramétrisé à partir des données résultant d'une investigation extensive dans une forêt d'aulne dans le Nord de l'Allemagne. La structure du modèle de base est décrite, spécialement pour la partie dynamique du carbone. ALMIS a été utilisé pour étudier les effets de l'adaptation des feuilles à la lumière sur la croissance globale et la compétition. Différentes conditions photosynthétiques ont été simulées pour la croissance, soit en condition isolée, soit en condition de compétition entre elles. Dans le cas de la croissance en condition isolée pour une longue période, le modèle d'arbre avec uniquement des feuilles d'ombre accumule moins de biomasse totale que ceux avec uniquement des feuilles de lumière. Mais un arbre qui aurait la capacité d'adaptation de ses feuilles aux conditions de lumière au sein de sa canopée aurait une meilleure croissance. La compétition entre arbre améliore les avantages de l'adaptation des feuilles vis-à-vis de la croissance globale de la plante.

Spatial heterogeneity of ecosystem carbon fluxes in a broadleaved forest in Northern Germany

“…Only stationary data after Foken & Wichura (1996) with u * higher than 0.4 m s −1 were used for this analysis. The equation for ecosystem respiration was used to calculate canopy assimilation ( F P ) from the daytime fluxes: Canopy assimilation was then fitted against global radiation measured above the canopy by means of a tangens hyperbolicus function (von Stamm, 1994; Eschenbach, 2000): where k is an empirical coefficient describing the initial slope of the light response curve and I is the PPFD (μmol Phot m −2 s −1 ). Since PPFD and global radiation are closely related and the PPFD sensor above the canopy had several gaps in 2002, we used global radiation for the curve fitting and gap filling.…”

“…Canopy assimilation was then fitted against global radiation measured above the canopy by means of a tangens hyperbolicus function (von Stamm, 1994; Eschenbach, 2000):…”

“…For Black Alder, no biometric equations relating biomass or volume to DBH were available. Therefore, data were applied from Eschenbach (1995), who made a biomass census for a complete Alder tree. The Alder trees, in the Alder-Ash stand of our study, grew at a similar site and were at comparable stage of age to the Alder trees studied by Eschenbach (1995).…”

Enhanced possibilities for analyzing tree structure as provided by an interface between different modelling systems

“…During the last years it has become evident that a precise description of the morphological construction of the growing tree and its competitive environment, and a linkage between structural and process-based components, are required for modelling tree growth (Bassow et al 1990). The result were so-called functional-structural tree models (FSTMs) (Perttunen et al 1996, Kurth and Sloboda 1997, Reffye et al 1997, Balandier et al 2000, Bosc 2000, Eschenbach 2000, Jallas et al 2000, Sievänen et al 2000 which treat morphological entities of a tree as interacting units, each equipped with its own geometrical, physical and physiological characteristics. They are becoming increasingly popular as research tools in botany, agronomy and forest science.…”

Incorporating Lindenmayer systems for architectural development in a functional-structural tree model

“…modelling diffusion of substrates). In a number of model or modelling tools, the suitable combination of methods to deal effectively with both architecture and physiology has been addressed (Kurth, 1999;Eschenbach, 2000;Karwowski and Prusinkiewicz, 2003;Yan et al, 2004). The development of models, where the architecture and functioning interact, is of key importance for better understanding the structural dynamics of trees.…”