Morphological and functional variability in the root system ofQuercus ilexL. subject to confinement: consequences for afforestation

Abstract

-We examined root morphological and functional differences caused by restrictions imposed to vertical growth in the root system of holm oak (Quercus ilex L.) seedlings to assess the consequences of using nursery containers in the development of a confined root system for this species. Thus, root morphological, topological and functional parameters, including hydraulic conductance per leaf unit surface area (K RL ), were investigated in one-year seedlings cultivated in three PVC tubes differing in length (20, 60 and 100 cm). Longer tubes showed greater projected root area, root volume, total and fine root lengths, specific root length (SRL) and K RL values than did shorter tubes. On the other hand, the length of coarse roots (diameter > 4.5 mm) and the average root diameter were greater in shorter tubes. The strong positive correlation found between K RL and SRL (r = +0.69; P < 0.001) indicated that root thickness was inversely related to water flow through the root system. We concluded that root systems developed in longer tubes are more efficient for plant water uptake and, therefore, changes in root pattern produced in standard forest containers (i.e. about 20 cm length) may in fact prevent a proper establishment of the holm oak in the field, particularly in xeric environments.Quercus ilex L. / root hydraulic conductance / root morphology / afforestation Résumé -Variabilité morphologique et fontionnelle du système racinaire de Quercus ilex L. soumis au confinement : conséquences pour les reboisements. Nous avons examiné les différences morphologiques et fonctionnelles qui ont été induites par des restrictions imposées au développe-ment vertical des racines de plantules de chêne (Quercus ilex L.). Les paramètres morphologiques, topologiques et fonctionnels du système racinaire, et aussi la conductivité hydraulique par unité de surface foliaire (K RL ), ont été recherchés sur des plantules d'une année cultivées dans des tubes de PVC de différentes longueurs (20, 60 et 100 cm). Les tubes les plus longs présentent des surfaces projetées de racines, des volumes racinaires, des longueurs de racines fines et totales, des longueurs spécifiques SRL et des K RL supérieurs à ceux des tubes courts. Inversement, dans les tubes courts se trouvent des racines de plus fortes sections avec les longueurs les plus grandes de grosses racines (diamètre > 4,5 mm). La forte corrélation positive trouvée entre K RL et SRL (r = +0, 69 ; P < 0, 001) a indiqué que la grosseur de la racine est inversement proportionnelle au flux d'eau transporté. On conclut que les systèmes racinaires développés dans des tubes plus longs sont plus efficaces dans l'extraction de l'eau et, par conséquence, les modifications dans le modèle du développement des racines qui ont été produites dans les conteneurs standards (e.g. environ 20 cm de longueur) pouvaient empêcher l'établissement approprié du chêne in situ, surtout dans des environnements à fortes contraintes hydriques.Quercus ilex L. / conductance hydraulique racinaire / morphologie racinaire...

Root traits explain different foraging strategies between resprouting life histories

“…higher SRL and SVR; see also Silva et al 2002, andGuerrero-Campo et al 2006), but also they had a more efficient allocation pattern when only the most absorptive root region is considered. Roots with high SRL or profusely branched roots had potentially higher transport efficiency (Fitter 1986;Huang and Eissenstat 2000;Pemán et al 2006;Hernández et al 2010; see details in the Introduction). Therefore, our results suggest that the greater hydraulic efficiency recently found for R-Rhamnaceae species of the Californian chaparral (Pratt et al 2010) could be a widespread pattern in fire-prone ecosystems.…”

“…In addition, plants with high SRL tend to show higher root hydraulic conductance per leaf unit surface area (Pemán et al 2006) or per stem cross-section area (Hernández et al 2010). Consequently, plants with high SRL (considering either the whole root system or only fine roots) show high uptake rates of water (Eissenstat 1991), nitrogen (Reich et al 1998) and phosphorus (Comas et al 2002).…”

Morphological traits and water use strategies in seedlings of Mediterranean coexisting species

“…The positive correlation between SRL and K As indicates that the root systems characterized by less massive roots per unit length have a higher hydraulic conductance. Previous significant correlations between root morphology parameters as SRL and hydraulic conductivity in herbaceous and woody species have also been reported (Rieger and Litvin 1999;Pemán et al 2006), highlighting the role of root architecture in plant water status. Indeed, root structure has been related to the variability in physiological traits, including the vulnerability to cavitation in Mediterranean shrubs of California (Jacobsen et al 2005(Jacobsen et al , 2007a.…”

“…We undertook a comparative nursery experiment with seven coexisting Mediterranean shrubs that encompass the range of dominant strategies in the study area (i.e., different leaf and stem habit, and different post-fire strategy). We hypothesized that coexisting species diverge in their set of traits related to water use strategies, and that root system traits determine different water use strategies (Huang and Eissenstat 2000;Pemán et al 2006). We examined allocation to aboveground and belowground tissues, root system morphology and water-relation traits.…”

Évaluation d’un modèle semi-empirique pour la prédiction de la biomasse des racines fines dans la végétation composite et complexe d’une zone boisée

“…Because roots of woody species in dry environments are known to reach deep soil horizons [16] in each transect eight soil core samples (from randomly selected locations) were taken to a depth of 100 cm, using a 100 mm internal diameter steel corer, thus yielding a total of 40 root core samples per site. Core samples at the xeric site were taken at: 0−15, 15−30, 30−50, 50−75 and 75−100 cm depth increments.…”