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-Leaf morphology was assessed in nine mixed oak stands (Quercus petraea and Q. robur) located in eight European countries. Exhaustive sampling was used in an area of each stand where the two species coexisted in approximately equal proportions (about 170 trees/species/stand). Fourteen leaf characters were assessed on each of 5 to10 leaves collected from the upper part of each tree. Three multivariate statistical techniques (CDA, canonical discriminant analysis; PCA, principal component analysis; MCA, multiple correspondence analysis) were used in two different ways: first on the total set of leaves over all stands (global analysis) and second, separately within each stand (local analysis). There was a general agreement of the results among the statistical methods used and between the analyses conducted (global and local). The first synthetic variable derived by each multivariate analysis exhibited a clear and sharp bimodal distribution, with overlapping in the central part. The two modes were interpreted as the two species, and the overlapping region was interpreted as an area where the within-species variations were superimposed. There was no discontinuity in the distribution or no visible evidence of a third mode which would have indicated the existence of a third population composed of trees with intermediate morphologies. Based on petiole length and number of intercalary veins, an "easy to use" discriminant function applicable to a major part of the natural distribution of the species was constructed. Validation on an independent set of trees provided a 98% rate of correct identification. The results were interpreted in the light of earlier reports about extensive hybridization occurring in mixed oak stands. Maternal effects on morphological characters, as well as a lower frequency or fitness of hybrids in comparison with parent species could explain the maintenance of two modes, which might be composed of either pure species or pure species and introgressed forms. morphology / leaf / Quercus robur / Quercus petraea / taxonomyRésumé -La différenciation morphologique des feuilles entre Quercus robur et Quercus petraea est stable à travers les peuplements mé-langés de chênes de l'ouest européen. La variabilité de la morphologie foliaire a été etudiée dans neuf peuplements mélangés de chênes (Quercus petraea et Q. robur) en Europe sur la base d'un échantillon exhaustif moyen de 170 arbres/espèce/peuplement. Trois méthodes d'analyses multivariables ont été utilisées (ACD : analyse canonique discriminante ; ACP : analyse en composantes principales ; AFC : analyse factorielle des correspondances). Les trois méthodes aboutissent à des résultats congruents. La première variable synthétique de chaque méthode se Ann. For. Sci. 59 (2002)

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. SUMMARY(1) The partitioning of incident precipitation into throughfall, stemflow and interception loss was assessed in a 14-year-old Picea sitchensis plantation in South Scotland. The tree crowns overlapped to form a dense canopy with 25, 44, 28 and 3% of ground area covered respectively by foliage from one, two, three and four trees. All main branches sloped down inwards to the tree trunk.(2) Over a single calendar year the incident precipitation was 1639 mm. Stemflow accounted for 27% of this, throughfall 43% and interception loss, estimated by difference, accounted for 30%. Percentage stemflow was consistent throughout the year but, during the winter period (January-March), throughfall increased to 57% and interception loss decreased to 15%.(3) The amount of stemflow for individual trees was positively correlated (P=0 05) with the projected area of tree crowns.(4) The amount of throughfall was greatest close to the tree trunks and between trees in the same row, particularly for intermediate levels of rainfall (20-40 mm week -).(5) The spatial pattern of throughfall parallels the distribution of fine roots in the soil.

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