| Summary: | What pattern do the great natural vegetation belts take when faced with the roughness of the wide spaces of Fennoscandia? In order to understand the evolution of landscapes under actual attenuated climatic forcing as well as the subsequent adaptation of the northern sylvatic and asylvatic systems, the author goes on a long trip through the boreal forest up to the high latitudes tundra. The ancient colonization of the Scandian Mountains by Picea excelsa, omnipresent and certified as early as the end of the late ice-age on some emerging shelters above the Scandinavian inlandsis, comes along with a high ecogenetic diversity of the conifer, especially the taiga of columnar Spruce which forms the most characteristic stand. Despite the hardiness of Picea excelsa, Pinus sylvestris is the one which really makes up, beyond the 70th parallel, the most northern evergreen forests. Upon these windy plateaus, the fickleness of the snow cover during long boreal winters could explain pro parte the pre-eminence of Scots Pine. Then the monospecific bush of Betula tortuosa borders, at residual arctic tundra limits, the shrubby vegetation of the end of the world. Below, the Mountain birch, also part of the polymorphic species Betula pubescens, forms wide hardwood belts as much in the subalpine level of Scandian Mountains as in the northern taiga which covers the Lapland Mounts. In conclusion, the zonation of northern forests in discussed, with special emphasis on the chief part played by the various taxa of Birch in the organization of boreal forests and the fluctuating forestlines in the frozen North of Western Europe. Quel agencement adoptent les grandes formations végétales naturelles confrontées à l’âpreté des immenses espaces de la Fennoscandie ? Comprendre aussi bien l’évolution des paysages sous forçage climatique en voie d’atténuation que l’adaptation subséquente des systèmes sylvatiques et asylvatiques nordiques, conduit l’auteur à un long cheminement à travers la forêt boréale jusqu’à la toundra des latitudes extrêmes. ...
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