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Accueil du site → Doctorat → Allemagne → 2009 → The drought tolerance limit of European beech (Fagus sylvatica L.) stands on Mt. Olympus, NC Greece

Albert-Ludwigs Universität Freiburg im Breisgau (2009)

The drought tolerance limit of European beech (Fagus sylvatica L.) stands on Mt. Olympus, NC Greece

Xystrakis, Fotios

Titre : The drought tolerance limit of European beech (Fagus sylvatica L.) stands on Mt. Olympus, NC Greece

Auteur : Xystrakis, Fotios

Université de soutenance : Albert-Ludwigs Universität Freiburg im Breisgau

Grade : Doctor rer. nat. 2009

Résumé
To evaluate the effects of climate change, the distribution limits of species have to be assessed. In this thesis the drought-tolerance threshold of European beech on calcareous soils at Mt. Olympus in NC Greece was estimated. The results provide valuable information concerning the ability of beech to dominate and form viable stands in regions with similar environmental conditions. The analysis of the drought-tolerance limit of beech was studied at its (near-)natural limits with the more drought-tolerant Pinus nigra stands. Data was collected from 108 plots which were arranged in 36 triplets running along transects in beech stands, through the ecotone and in black pine stands. The transects were positioned at various aspects and elevation zones on the mountain. The interplot spacing along each transect was about 40 m. All vascular taxa were recorded using the Londo scale and environmental variables, mainly components of the soil water balance model (available soil water storage capacity ; actual and potential evapotranspiration, moisture deficit, precipitation), were estimated for each plot. TWINSPAN was used for the ground-flora classification and indirect (non-metric multidimensional scaling) and direct (CCA) gradient analyses provided insights into the relationship between the vegetation patterns and the environmental variables. Finally, discriminant analysis and classification trees provided the dominant variables controlling the distribution of the vegetation units as well as the drought-related threshold of the beech-related vegetation units. The results demonstrated a dominant gradient from “dry” pine-related plots towards beech-related plots on sites reflecting more favourable moisture conditions. The analysis of the threshold of the occurrence of vegetation units revealed that the actual evapotranspiration and the moisture deficit are the driving factors of the vegetation pattern, thereby indicating that for the assessment of drought-intensity, edaphic and climatic components of drought have to be equally considered. Beech-related vegetation units are predicted to dominate on sites reflecting actual evapotranspiration rates > 276.5 mm while pine-related vegetation units mostly on sites with actual evapotranspiration rates < 276.5 mm and moisture deficit > 312.5 mm during the three drier months (June-July-August). The quantified drought threshold for the occurrence of beech at Mt. Olympus provides valuable input information for further modelling and management.

Mots Clés : Drought , Vegetation , Threshold , Soil water Balance , Climate , European Beech , Fagus sylvatica

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Page publiée le 31 août 2010, mise à jour le 12 mai 2019