Dear all,

chances and limits of European Beech species under climate change-conditions are intensively discussed and became the subject of controversial debate. My question is the following:

Is there any eco-physiological evidence for limitation of European beeches relating to Atlantic climate, in particular to increasingly moderate winter temperatures?

Indications might be:

(1)    The absence of Oriental Beech (Fagus orientalis) in the coastal lowland zone of the eastern part of Black Sea Region (Euxine-Colchic region of NE Anatolia)

(2)    The absence of European Beech (Fagus sylvatica) in the Hibernian region of Ireland

The Hibernian climate stations (Cork, Klillarney) appear to have similar monthly temperatures for January (+6 to +7°C) like the Euxine-Colchic Stations at the Black Sea coastal region (e.g., Ünye, Girezun, Rize). In either cases, beeches give way to other basic forest genera like deciduous oaks and chestnuts and admixed evergreen laurophyllous taxa like Ilex, Hedera, Arbutus, Rhododendron.

I am of course aware, that the absence of Beech in Ireland is commonly interpreted by its insufficient biological dispersion and its late postglacial arrival. However, I would like to raise the question, if Holocene history / incomplete dispersal of European beech are solely responsible for its northwestern limitation.

I would like to postulate, that there is also an eco-physiological limitation of European beeches relating to Atlantic climate, in particular to mild winter temperatures. Deciduous oaks and chestnuts, which are adapted to long-lasting growing seasons (“macrothermophilous species) and evergreen laurophyllous taxa, which are adapted to almost year-round growing season (“megathermophilous species”) should benefit from mild winters, while “mesothermophilous species” like the European beeches would require a distinct dormant season for their stable metabolism. Increasingly mild winters might cause higher respiration losses and stress factors of adverse carbon balance (relationship between photosynthesis and cellular respiration), which might reduce vitality and strength of European beeches in competition to macro- and megathermophilous species.

Is there any physiological data which prove my theory? Are there any threshold values for upper limits of monthly winter temperatures / temperatures of the coldest quarter for physiological and ecological existence of European beeches?

I really appreciate any help you can provide.

Thanks, Helge