Epsilon Archive for Student Projects

Abstract

Natural properties of Norway spruce (Picea abies) and birch (Betula spp.)suggest a good ecological ability to form a stratified mixture with birch in a upper and spruce in a lower stratum. Maintaining birch as the shelter over planted spruce in the beginning of rotation
might result in higher overall yield than spruce monocultures. Other advantages such as
higher ecological stability, increased biodiversity and better economic performance have
been demonstrated by studies in other Northern European countries.

A stratified mixture of Norway spruce and silver birch and pure Norway spruce stand growing on fertile sites in north-east of Latvia were the study objects. The main objective of the study was to evaluate silvicultural aspects and economic performance of the mixed stand and make a comparison to spruce monoculture.

Production of spruce alone was 19, 15 and 14 % lower in the mixed stand compared to spruce monoculture over simulated rotations of 60, 80 and 100 years, respectively. However, birch shelter, which was removed latest at age 42 years, produced substantial wood volume, and overall yield was 8, 5 and 5 % higher in the mixed stand for the respective rotations. More frequent frost induced damage was observed in the pure spruce stand, however, whipping damages were evident in the mixed stand. Economic outcome, in
terms of land expectation value, was higher for management alternatives in the mixture.