Kustaa Seppälä , Matti Keltikangas

Alikasvostaimistot Pohjanmaan ojitusalueiden hieskoivikoissa

Seppälä K., Keltikangas M. Alikasvostaimistot Pohjanmaan ojitusalueiden hieskoivikoissa.

Tiivistelmä

It is known from earlier studies that many different types of peatland become afforested or naturally reforested fairly rapidly after drainage has been carried out. Peatlands, which initially develop into birch stands are common in the Ostrobothnian drainage areas. The occurrence of under-storey seedlings their species distribution and development potential in such Betula pubescenis stands 15—35 years after drainage are examined in this study. Details of the study material, which consisted of 204 sample plots, are given in Table 1., and the location of the sample plots is shown in Fig. 1. Fifteen circles, each one square meter large, were systematically marked out in each sample plot and the number of seedlings of different tree species growing in the circles subsequently counted. One seedling per circle, which was found to be the best as regards size and development potential, was chosen as the dominant seedling. The tree species, height, age and degree of development potential of the dominant seedlings were all noted. In addition, the ground vegetation in each circle was analyzed. The means for the number of seedlings at each sample plot were calculated in groups according to drainage age, site fertility and geographical area (Table 1). The results show that the ability of a site to produce seedlings has been retained rather well, in places where drainage had even been carried out a long time ago, if the conditions otherwise have been favourable. The number of seedlings capable of development appears, on average, to be satisfactory. The number of coni-feroys seedlings capable of development in sites of the southern part of the studied area in sufficient for the formation of new stand. However, in northern Ostrobothnia, the number, on average, was so small, that a fully stocked seedling stand could only be obtained by resorting to a large admixture of birch seedlings. The variation in the data is large and thus the means give only limited information about the phenomena studied. Table 2 shows the proportion of sample plots where the number of seedlings capable of develop-ment satisfies the accepted minimum requirements. It can be seen that in the southern part of the research area understorey seedling growth capable of development is found in two sites out of three. The reasons for the great differences between the areas did not become apparent in this study.

Vastaanotettu 31.10.2017 Julkaistu 1.1.1978

Katselukerrat 534

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