Comparative studies of the water relations and the hydraulic characteristics in Fraxinus excelsior, Acer pseudoplatanus and A. opalus trees under soil water contrasted conditions

Abstract

-Plant water relationships and hydraulic characteristics were measured for two species of the genus Acer that co-occur with Fraxinus excelsior, but differ in their habitat preference with respect to soil moisture: Acer pseudoplatanus is restricted to wet habitats, whereas Acer opalus occurs on drier sites. The data obtained showed significantly lower hydraulic conductance and lower vulnerability to embolism in the drought-tolerant species, Acer opalus, than in the water prefering species Acer pseudoplatanus. Similar differences in hydraulic conductance and xylem vulnerability to embolism were also found under dry acclimated conditions for Fraxinus excelsior trees, indicating that the hydraulic differences observed might be attributable to the contrasting soil water conditions of the sites. The possible physiological and ecological significance of such differences are discussed, in relation to habitat preference and the distribution of each species.hydraulic conductance / xylem embolism / drought tolerance / Acer pseudoplatanus / Acer opalus / Fraxinus excelsior Résumé -Étude comparée des relations hydriques et des caractéristiques hydrauliques chez Fraxinus excelsior, Acer pseudoplatanus et Acer opalus dans différents milieux secs et humides. Ce travail concerne l'étude des relations hydriques et la détermination des caractéristiques hydrauliques chez deux espèces du genre Acer, présentes fréquemment dans les espaces naturels en compagnie de Fraxinus excelsior, mais différant dans leur mode de distribution en fonction de la disponilité de l'eau du sol : Acer pseudoplatanus se rencontre sur des sols bien alimentés en eau, Acer opalus a une préférence marquée pour les milieux secs. Les résultats obtenus montrent, chez Acer opalus, l'espèce tolérante à la sécheresse, que la conductance hydraulique et la vulnérabilité à la cavitation sont moins fortes que chez Acer pseudoplatanus, l'espèce des zones humides. Des modifications identiques de la conductance hydraulique et de la vulné-rabilité à la cavitation s'observent également chez Fraxinus excelsior pour l'espèce acclimatée aux milieux secs, ce qui semble indiquer que ces changements des caractéristiques hydrauliques pourraient être associés aux conditions hydriques des milieux. Ces résultats sont analysés au plan physiologique et écologique en relation avec le mode de distribution de ces espèces dans leur environnement respectif.conductance hydraulique / embolie du xylème / tolérance à la sécheresse / Acer pseudoplatanus / Acer opalus / Fraxinus excelsior Ann. For. Sci. 58 (2001) [723][724][725][726][727][728][729][730][731] 723

Survival and acclimatation ofPopulus nigrato drier conditions after damming of an alpine river, southeast France

“…This hydraulic behaviour can be related to that of F. excelsior, a species that frequently occurs with poplar trees. Ash trees have a broad ecological amplitude [16,17,23,24], the same for maple trees [31], particularly because they can acclimatize to limited water availability by increasing their resistance to cavitation [14]. As demonstrated in this study, poplar species did not have this adaptation potential of hydraulic architecture.…”

“…Xylem water potentials (Ψ xylem ) were estimated by measuring the water potential of leaves that had been enclosed in aluminium foil and a plastic bag early in the morning [3,32]. Hydraulic conductivity was measured on twigs obtained from branches collected in the morning from mature trees using the procedure described by Lemoine et al [14]. The branches were enclosed in black airtight plastic bags to reduce water loss through transpiration and quickly brought to the laboratory for hydraulic analysis.…”

Leaf water status and stem xylem flux in relation to soil drought in five temperate broad-leaved tree species with contrasting water use strategies

“…Korn (2004) reported similar values on sycamore. Lemoine et al (2001) found remarkably high (less negative) daily minima of Ψ L in A. pseudoplatanus which they explained by a high shoot hydraulic conductivity. This matches well to our findings of a particularly high root-to-leaf hydraulic conductivity in sycamore.…”

“…In F. excelsior, Lemoine et al (2001) found the minimum threshold of leaf water potential to vary between -1.5 and -2.8 MPa depending on habitat, water supply and drought acclimation. Other authors reported loss of hydraulic conductivity starting with water potentials of -2 MPa (Cochard et al, 1997;Crombie et al, 1985).…”

Hydraulic conductance of root and shoot measured with the transient and dynamic modes of the high-pressure flowmeter

“…The importance of investigating hydraulic properties of trees is highlighted by recent studies showing that they may play a role in ecological strategies of species and that they can underlie the response to environmental changes [5,10]. For instance, pioneer species like Acer saccharinum and Juglans regia were vulnerable to cavitation, exhibited hydraulic segmentation and showed high hydraulic conductance (k), whereas established species like Quercus species and Pinus contorta were less vulnerable and presented a relatively low k [23].…”