Current issue: 55(3)
Under compilation: 55(4)
Shifting cultivation, practiced earlier in Finland, was beneficial for grey alder (Alnus incana (L.) Moench). It can produce seeds early and the early growth of the seedlings is fast. Areas where shifting cultivation was intensive, the areas next to the fields were pure alder stands, next circle was Betula sp. dominated, beyond that could be found Scots pine (Pinus sylvestris L.), and finally Norway spruce (Picea abies (L.) H. Karst.). When shifting cultivation ended, Norway spruce became more common. Many young mixed stands had Norway spruce undergrowth and alder overgrowth. The aim of the study was to find out how the stands develop to spruce dominated stands, and how they should be managed.
The density of spruce undergrowth affects the further development of both spruce and alder. The number of alder stems decreases the faster the denser the spruce undergrowth is. Alder overgrowth slow down the early diameter and height growth of spruce compared to pure stands. Also the diameter and height growth of alder remains smaller in mixed stands. The basal area of spruce develops slowly in the beginning, increases significantly by the age of 30, and surpasses the growth of pure spruce stands in Oxalis-Myrtillus site type. Thus, Norway spruce do not suffer from growing in the undergrowth. In the first years, fast growing alder seedlings limits growth of ground vegetation and protects spruce seedlings from frost. Later thinning or removal of alder benefits spruce growth. The density of spruce undergrowth decides how much alder can be leaved in the stand. If the spruce undergrowth is thin, more alder can be left in the stand.
The PDF includes a summary in German.
About 40% forest in Finland are mixed stands that have birch (Betula pubescens and B. verrucosa) as one of the species. The aim of this research was to study the structure of root system of birch and compare it to the other main tree species in Finland.
The root systems were dug out and measured in 28 sample plots in Southern and Central Finland, representing different forest site types. Birch roots correspond 30‒100% of the volume of the stem, the largest root systems being in the sandy soils or peatlands. Also the longest lateral roots can be found at these sites. The size variation of root system of birch is larger than in Scots pine (Pinus sylvestris L.), and the vertical root system is in general smaller in birch. Birch seems to be better than pine able to adapt its root system to the existing conditions. The smallest root systems were found in the good forest site types, but the roots grow in the good sites denser than in the poor sites. The lateral roots of the main tree species in Finland, birch, Scots pine and Norway spruce (Picea abies (L.) H. Karst.) grow in different depths, which decreases the competition between the species. This finding gives support to cultivation of mixed stands.
The PDF includes a summary in English.