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Photos & texts by Sabina Burrascano is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.5 Italy License.
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Boreal and mediterranean plants shaking hands!

Silver birch (Betula pendula) is a tree tipical of the boreal region. It is spread widely in Northern Europe from Norway to Siberia and Kazakistan towards east, and to Basque region towards west. The southern most populations occur along Italian peninsula.

Betula pendula treesIn Italy this species is rather common in the Alps becoming rarer and along the peninsula, where it is limited to isolated patches characterized by particular microclimatic and edaphic conditions.

This distribution is related to the climatic history of the Quaternary period. Pollen analyses show how this species was widespread in the Italian peninsula just after the last glaciation. Then a more oceanic climate favoured other tree species, e.g. European beech (Fagus sylvatica).

One of this isolated patches with very peculiar conditions is the Caldara di Manziana. It is an ancient volcanic crater where in the lowest part air moisture compensates for Mediterranean summer drought and a patch of silver birch forest occurs.

On the slopes, just above this patch,  the deciduous oaks Quercus cerris and Q. frainetto give rise to a definitely more mediterranean community.

On the edge of the birch patch you can also see a strictly mediterranean shrub of the leguminosae family Adenocarpus complicatus that is not so common in central Italy for its preference for siliceous substrata. All of this is rather peculiar, just as seeing the birch white trunks just north of Rome!

Adenocarpus complicatus legume

Betula pendula bark

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