An examination of the interaction between climate, soil and leaf area index in a Quercus ilex ecosystem

Abstract

-In Mediterranean-type ecosystems, water availability is one of the most significant variables that regulates whole plant leaf area. An equilibrium should exist between climate, soil and leaf area in such water-limited conditions. The aim of this study was to identify the relations between leaf area index (LAI), environment (climate, soil) and fluxes (water, carbon) in Mediterranean evergreen oak (Quercus ilex L.) ecosystems. To achieve this objective, 50-years simulations were performed using the FOREST-BGC model by varying LAI for a reference site and for different climates and soil water holding capacities (SWC). Transpiration, drought stress, net photosynthesis and canopy water use efficiency (WUE) were examined on a yearly basis for the last ten years of the simulation. Similar to other findings, our results show that LAI depends on site water availability, including both climate (precipitation, potential evapotranspiration) and soil factors (e.g. water storage capacity). Low SWC limit the development of the ecosystem. On high SWC soils, development is mainly limited by the climate. When LAI increases under constant SWC and climate conditions, the decrease in annual transpiration per unit of LAI is accompanied by an increase in drought stress. Equilibrium LAI maximizes carbon assimilation. For the reference site, the equilibrium LAI is close to the observed value, 3.25. The corresponding transpiration, assimilation and WUE are 375 mm, 1251 g C m -2 and 3.1 mmol CO 2 mol -1 H 2 O, respectively. For the different sites, there is an hyperbolic decline of WUE with increasing SWC. This implies that production efficiency per unit leaf area is higher in most water-limited environments. Our study shows that a model such as FOREST-BGC allows inter-relations between water balance, carbon balance and drought stress to be taken into account to better understand ecosystem LAI.leaf area index / hydrological equilibrium / water availability / climate / soil factor / Mediterranean-type ecosystem / Quercus ilex L. / evergreen oak Résumé -Interactions entre climat, sol et surface foliaire dans un écosystème à Quercus ilex. Dans les écosystèmes méditerranéens, la disponibilité en eau est une des variables les plus significatives qui régulent la surface foliaire. Un équilibre doit exister entre le climat, le sol et la surface foliaire dans ces conditions de limitation en eau. L'objectif de cette étude est d'identifier les relations entre l'indice foliaire (LAI), l'environnement (climat, sol) et les flux (eau, carbone) pour les écosystèmes à chêne sempervirent méditerranéen Quercus ilex L. Pour cela, des simulations de 50 ans ont été effectuées avec le modèle FOREST-BGC en faisant varier le LAI pour un site de référence et pour différents climats et capacités en eau du sol (SWC). La transpiration, la contrainte hydrique, la photosynthèse nette et l'efficacité d'utilisation de l'eau de la canopée (WUE) ont été examinées au niveau annuel pour les dix dernières années de la simulation. Le LAI dépend de la disponibilité en...

Effects of altitudinal gradients on leaf area index, soil microbial biomass C and microbial activity in a temperate mixed forest ecosystem of Northwestern Turkey

“…Because leaf surfaces are the primary sites of energy, gas and water exchanges and of important physiological processes such as photosynthesis, interception, transpiration, and evapotranspiration are a function of LAI. Hoff & Rambal (2003) have also indicated that with increasing LAI, drainage decreases while transpiration and interception increases. Therefore, the relatively high soil moisture content at 1200 m elevation might have been due to the lower LAI.…”

How drought severity constrains gross primary production(GPP) and its partitioning among carbon pools in a <i>Quercus ilex</i> coppice?

“…The functioning of Quercus ilex stands in the south of France was simulated by Hoff et al (2002) and Hoff and Rambal (2003) using the Forest-BGC model. C use rules in this simple model are implemented so as to follow an optimal trajectory: trees use C first into leaves and fine roots for maximizing productivity, while minimizing water limitation; finally, stems appear as an end product built with the remaining C. Other modeling exercises with Q. ilex ecosystems also retained water-related constraints for their C use rules.…”

Efecto de la fragmentación en la morfometría foliar y el ambiente de Quercus germana Schldl. & Cham. (Fagaceae) en Xalapa, Veracruz

“…Sin embargo, en el presente estudio solo se encontraron diferencias morfológicas sin relación significativa con las ambientales. Por lo tanto, las diferencias ambientales no parecen estar afectando a las características morfométricas de la misma manera en todos los sitios (Hoff & Rambal, 2003). Debido a la cercanía y origen común de las subpoblaciones de Q. germana, las diferencias morfológicas no deberían presentarse aun en ambientes distintos.…”

“…However, in this study, only morphological differences without significant relation to the environmental ones were found. Therefore, the environmental differences do not seem to affect the morphometric characteristics in the same manner in all locations (Hoff & Rambal, 2003). Due to the closeness and common origin of the sub-populations of Q. germana, the morphological differences should not be present even in different environments.…”