Summer and winter embolism in oak: impact on water relations

Tyree, Mt; Cochard, Hervé

doi:10.1051/forest:19960201

Cited by 152 publications

(127 citation statements)

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“…Conifers exhibit another extreme situation because they do not seem to suffer at all from winter embolism. It has been argued that freezing-induced embolism can limit the growth, survival, and geographic distribution of plant species [64,94,110,134]. These studies suggest a link between xylem anatomy and the vulnerability to frost: the larger the conduit, the higher the vulnerability [42].…”

Section: Winter Embolismmentioning

confidence: 89%

“…It is worth noting that even 100 percent loss of conductivity of branches may be nonlethal for Quercus species. While most branches died at a soil water potential of -5 MPa, resprouting can occur from roots and some axial buds [134]. Eventually, figure 9D gives the only known example, so far, of what is called "vulnerability segmentation".…”

Section: Examples Of Vulnerability Curvesmentioning

confidence: 99%

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Hydraulic architecture of trees: main concepts and results

2002

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-Since about twenty years, hydraulic architecture (h.a.) is, doubtless, the major trend in the domain of plants (and especially trees) water relations. This review encompasses the main concepts and results concerning the hydraulic of architecture of trees. After a short paragraph about the definition of the h.a., the qualitative and quantitative characteristics of the h.a. are presented. This is an occasion to discuss the pipe model from the h.a. point of view. The second part starts with the central concept of embolism and give a review of important experimental results and questions concerning summer and winter embolism. The last part deals with the coupling between hydraulic and stomatal conductances. It discusses the theoretical and experimental relationships between transpiration and leaf water potential during a progressive soil drought, the increase of soil-root resistance and its consequences in term of xylem vulnerability, the factors controlling the daily maximum transpiration and how stomates can prevent "run away embolism". In conclusion different kinds of unsolved questions of h.a., which can be a matter of future investigations, are presented in addition with a classification of trees behaviour under drought conditions. To end, an appendix recalls the notions of water potential, pressure and tension.hydraulic architecture / cohesion-tension theory / summer embolism / winter embolism / drought resistance Résumé -Architecture hydraulique des arbres : concepts principaux et résultats. Sans aucun doute, depuis une vingtaine d'années, l'architecture hydraulique (a.h.) est devenue une approche majeure dans le domaine des relations plantes-eau (et particulièrement pour les arbres). Cette revue présente les principaux concepts et résultats concernant l'a.h. Après un bref paragraphe sur la définition de l'a.h., les caractéristiques qualitatives et quantitatives définissant l'a.h. sont passées en revue. À cette occasion le « pipe model » est discuté du point de vue de l'a.h. La seconde partie commence avec le concept central d'embolie et continue avec une présentation des principaux résultats et questions touchant l'embolie estivale et l'embolie hivernale. La dernière partie analyse le « couplage » entre les conductances hydraulique et stomatique. Il y est discuté des relations théoriques et expérimentales entre la transpiration et le potentiel hydrique foliaire durant la mise en place d'une sécheresse progressive du sol, de l'augmentation de la résistance sol-racines et de ses conséquences en terme de vulnérabilité du xylème, des facteurs contrôlant la transpiration maximale journalière et de quelle manière les stomates peuvent prévenir l'emballement de l'embolie. La conclusion fait état de différentes questions non résolues, qui pourraient faire l'objet de recherches futures et esquisse une classification du comportement des arbres vis-à-vis de la sécheresse. Pour finir, un appendice rappelle les notions de potentiel hydrique, de pression et de tension.architecture hydraulique / théorie de la cohé...

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Section: Winter Embolismmentioning

confidence: 89%

Section: Examples Of Vulnerability Curvesmentioning

confidence: 99%

Hydraulic architecture of trees: main concepts and results

2002

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“…I), with heavy frosts in the first quarter that were more influential on the trees in the Calañas plot as revealed by the physiological measurements. These frosts could have led to bud freezing [10] and to a considerably decreased xylem hydraulic conductivity [34,36]. Notwithstanding the unfavourable climatic conditions of that year, the water potential of the oaks never fell below -3.70 MPa in San Bartolomé, but reached -4.10 MPa in Calañas.…”

Section: Discussionmentioning

confidence: 99%

Influence of pruning and the climatic conditions on acorn production in holm oak (Quercus ilex L.) dehesas in SW Spain

et al. 2008

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-Acorn production by Quercus ilex L. ssp. ballota (Desf.) Samp. in SW Spain was assessed, and variations between years and the influence of pruning on it were examined. To this end, an experimental study was conducted at two different sites (Calañas and San Bartolomé, in the province of Huelva) where trees were subjected to traditional (light, moderate or heavy) pruning and also to a new (crown-regeneration) pruning method. Acorn yield was quantified over a period of 5 years in the Calañas plot and 4 in the San Bartolomé plot, and found to average at 95.61 ± 0.76 g DM/m 2 , which is equivalent to 6.5 ± 0.05 kg DM/tree; however, yield figures varied markedly between years depending on the particular climatic conditions. The average acorn production was correlated with the water potential in mid summer (end of July); the annual, spring and autumn rainfall; and the actual evapotranspiration for the period from September (previous year) to August. No significant differences in acorn production between traditional pruning intensities were detected; in fact, there were only hints that heavy pruning might result in decreased acorn yields. The new pruning method used, crown-regeneration, seems promising with a view to increasing acorn yield; however, it should be tested on larger sample sizes before any final conclusions can be drawn in this respect. Based on the results, the present health status of holm oaks in southwestern Spain (a result of sustained decline) and the low value of firewood -which used to be a very important source of income from pruning a few decades ago -, the authors recommend reducing the frequency and intensity of pruning in the dehesas of the study area.holm oak / acorn production / pruning / masting Résumé -Influence de la taille et des conditions climatiques sur la production de glands par le chêne vert (Quercus ilex L.) en dehesas dans le sud ouest de l'Espagne. La production de glands par Quercus ilex L. ssp. ballota (Desf.) Samp. dans le sud ouest de l'Espagne a été mesurée, et l'influence de la taille sur les variations interannuelles a été examinée. Dans ce but, une étude expérimentales a été conduite dans deux sites (Calañas et San Bartolomé dans la province de Huelva) où des arbres ont été soumis à une taille traditionnelle (légère, modérée ou forte) et aussi à une nouvelle méthode de taille (régénération de couronne). La production de glands a été quantifiée sur une période de 5 ans sur le site de Calañas et de 4 ans sur celui de San Bartolomé et était en moyenne de 95,61 ± 0,76 g de matière sèche/m 2 , ce qui équivaut à 6,5 ± 0,05 kg de matière sèche/arbre. Cependant la production a varié de façon marquée entre années en relation avec les particularités climatiques. La moyenne de production de glands était corrélée avec le potentiel hydrique au milieu de l'été (fin juillet) ; avec les précipitations annuelles, du printemps et de l'automne, et avec l'évapotranspiration pour les périodes allant de septembre (année précédente) à août. Aucune différence significative de productio...

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“…The purpose of this study was to investigate the seasonal patterns of xylem embolism and xylem transport properties in Quercus pubescens and Quercus ilex trees growing in a natural mixed coppice stand in conditions of severe water stress (summer 1993 and 1994), by evaluating the vulnerability of both species to water stress-induced embolism (Tyree & Cochard, 1996). We also attempted to relate embolism to the time course of total tree hydraulic resistance and tree water status.…”

Section: mentioning

confidence: 99%

Vulnerability of xylem to embolism in relation to plant hydraulic resistance in Quercus pubescens and Quercus ilex co‐occurring in a Mediterranean coppice stand in central Italy

Tognetti

Longobucco

Raschi³

1998

New Phytologist

110

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The seasonal patterns of xylem embolism and xylem transport properties in Quercus pubescens Willd. and Quercus ilex L. trees growing in a natural mixed coppice stand in conditions of severe water stress were investigated. Xylem embolism was evaluated in both dehydrating branches and in apical twigs during a whole year. Measurements of xylem water potential were conducted from predawn to sunset on selected sunny days. On the same days, diurnal courses of leaf conductance were monitored. Measurements of half‐hourly sap flow were made by the heat‐pulse technique throughout the summer. At the onset of summer, a sharp decrease in water potential was observed in both species. Full recovery of water potentials was observed for both species after the first major rainfall event in September. Both experienced serious embolism throughout the year, ranging between minima of c. 60% (expressed as percentage loss of hydraulic conductivity) after the rains in autumn and after bud burst in spring, and maxima of c. 80% during summer and after freezing‐thawing events during the winter season. A significant negative linear relationship was found between water potential and xylem embolism in branches dehydrating in air for Q. pubescens and Q. ilex. Q. pubescens had greater efficiency in hydraulic transport (higher specific conductivity and leaf specific conductivity) by the xylem than Q. ilex. In June, leaf conductance was high early in the morning and decreased gradually during the day. Midday depression of leaf conductance, as a result of high evaporative demand combined with water deficit, was observed in both species. In August, leaf conductance of both species was greatly reduced, as water potential dropped to extremely low values, and the stomata were almost completely closed during the afternoon. No hysteresis resulting from plant capacitance was observed in the relationship between shoot water potential and sap flow. Q. pubescens exhibited very high values of whole‐tree hydraulic resistance between July and September, whereas Q. ilex generally showed lower values. The effect of soil moisture depletion on the relationship between sap flow and shoot water potential appears as a lowering of water potential at zero flow. A significant decrease of whole‐tree hydraulic resistance in both species was observed with the onset of the autumn, preceding the partial recovery of twig hydraulic conductivity. The results demonstrate that both Q. pubescens and Q. ilex, although highly tolerant of severe water stress and tissue dehydration, operate at the limits of safety which are surpassed under severe droughts, and prolonged climatic stress might predispose these Quercus species to decline.

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Summer and winter embolism in oak: impact on water relations

Cited by 152 publications

References 17 publications

Hydraulic architecture of trees: main concepts and results

Hydraulic architecture of trees: main concepts and results

Influence of pruning and the climatic conditions on acorn production in holm oak (Quercus ilex L.) dehesas in SW Spain

Vulnerability of xylem to embolism in relation to plant hydraulic resistance in Quercus pubescens and Quercus ilex co‐occurring in a Mediterranean coppice stand in central Italy

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