Leo Heikurainen

Luonnontilaisten soiden metsien kasvu lisääntynyt

Heikurainen L. Luonnontilaisten soiden metsien kasvu lisääntynyt.

Tiivistelmä

In the late 1950's, the Department of Peatland Forestry at the University of Helsinki established a peatland protection area in the parish of Orivesi. The paper reports some results concerning the increment of tree stands in the area and the possible influence from a relatively distant drainage scheme. The area under study amounted to 500 ha and was later surrounded to the east and west by drained peatland forests. The first site was initially drained in 1961, the second with its location behind the esker, was drained at different times in the 1930's and 1950's (see Fig. 1). In 1961, 20 sample plots (20 x 20 m) were built on the area for educational purposes, 14 of which represent forest covered peatland site types. Growth increment data concerning the tree stand of the sample plots was measured three times in the 20 years since establishment (see Tables 1 and 2). It is generally believed that the increment of a forest stand on a virgin peatland area is very small and equivalent only to the natural drain of the stand. Growth data representing the situation in the 60's indicates a slight increase in the volume of the growing stock, an increase which is comparable to the average achieved for Southern Finland (Heikurainen 1971). The growth data for the 70's reveals a surprising increase in the increment of most sample plots. Seeking an explanation for the considerable increase in tree growth on peatlands supposedly in their natural condition, the author came to the conclusion that the neighbouring drainage, although situated at some distance from the area in question - in this instance several hundreds of meters - had hydrological consequences which nonetheless modified the virgin peatland ecosystem. This change caused the improvement in forest growth in the surrounding areas. The author stresses that this observation may have a wider interpretation since the improving effect of forest drainage on forest growth may extend beyond the area intended for drainage. In other words the change in vegetation, tree stand etc. resulting from forest drainage may be more powerful than previously expected and could affect an area originally intended for preservation in natural condition (natural conservation areas). It is possible for virgin ecosystems to be influenced several hundreds of meters from the drainage area.

Vastaanotettu 31.10.2017 Julkaistu 1.1.1982

Katselukerrat 1060

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