Climatic fluctuations and forestry in Lapland Eljas Pohtila
Pohtila, E. 1980. Climatic fluctuations and forestry in Lapland. - Holarct. Ecol. 3: 91-98. Climatic fluctuation is a serious problem for forestry in Lapland. Some indications about the nature and causal relationships of such fluctuation have been discussed. Cyclic variation can be explained by a "memory" in the atmosphere, variation in the Moons's gravitation, and solar activity. The index of atmospheric circulation over the northern hemisphere was the most effective climatic parameter in explaining the growth variation of Scots pine. E. Poh tila, The Finnish Forest Res. Inst., Rovaniemi Res. S tation, E teläran ta 55, SF-96300 Rovaniemi 30, Finland.
Significance of fluctuation
All biological produetion in Lapland is eharaeterized by a large yearly variation. One important eause of this is elimatie fluetuation. Experienees in grain eultivation fully justify us speaking about the "climatie hazard fae tor" (Hustich 1947, Fig. 1). Analogous eatastrophies to those oeeurring in grain eultivation are rare in timber growing, but not unknown. For instanee in 1901-02, an adverse climatie fluetuations eaused serious damage to the pine Pinus silvestris L. stands of Lapland (Mikola 1952). The summer of 1901 was exeeptionally warm, and subsequently the following year's leader shoots grew for a longer time than usual. As the summer 1902 was late and very eool, the shoots did not have enough time to lignify before the onset of winter and were dam aged by frost. The serious losses of artificially regener ated pine stands in the 1960's, as well as the devastation of fell birehes in 1965-66 were obviously the eonse quenees of parallel climatie fluetuations (Etholen 1972, Kallio and Lehtonen 1973). In reforestation in Lapland, climatie problems oeeur as early as the seed formation phase. Seed produetion of Seots pine requires two growing seasons from flowering to seed formation. In the north the abundanee of flow ering and seed erop is mainly eontrolled by tempera ture; the growing season both preeeding and following the flowering period must be warm (Sarvas 1971). In order to get enough cones to make gathering worth-
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Fig. 1. Dependence of the "clin;tatic hazard faetor" defined by Hustich (1947) on latitude in finland. Criterion vafiables are the relative annual crop value of rye (.) and the annual radial growth of Scots pine (0) and Norway spruce (,0,). Cv varia tion coefficient,
