Silver birch climatic adaptation and geographical variation of growth

Long-distance transfer of birch seeds is not worthwhile

The geographical variation of the silver birch growth, quality and adaptive traits were examined in this study. The native origins of silver birch and the ones imported to Finland were compared in field tests in different parts of the country. Long transfers of seeds from the south to the north led to high mortality and, on the surviving seedlings, recurrent frost damage of crowns, split trunks, bushy-like weak growth and later, poor quality of the stem. On the other hand, when the northern geographical origins were transferred long distances to the south, they grew slower than the local, southern ones. In southern Finland a safe seed transfer distance was 150 d.d. (degree days) when measured as a sum of effective temperature (over +5 ºC).

Origins from Estonia and northern Latvia produced slightly higher volumes than local domestic stands, but the ones imported from the Baltic countries had a higher frequency of various stem defects. Browsing damade by European elk was observed to be more frequent in origins imported to Finland from more southern latitudes than in the native ones.

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