Mixed stands in Nordic countries - a challenge for the future

Mixed stands are the most frequent type of stand in Nordic countries. A mixture of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) is the most common stand type in the region. But for most foresters and persons familiar with forestry, a mixed stand implies a conifer species and at least one broad-leaved species. Management and silviculture of mixed stands of conifers and broad-leaves has increased rapidly during the last 15 years. Efficient management of mixed stands increases profits for the owner as well as wood quality in the stand. Practical examples of how to manage mixed stands of birch (Betula pendula Roth and Betula pubescens Ehrh.) and Norway spruce are now available. In Finland, Norway and Sweden this is a common alternative to management of pure stands of conifers. In Norway, as well as mixed stands of birch and spruce, there are examples of mixed stands of European aspen (Populus tremula L.) and Norway spruce. Existing yield information for mixed stands is based on studies of stands which were managed improperly prior to the start of the study. The yield for birch at 35 years of age was 100 m(3) ha(-1). The growth of Norway spruce was reduced by 10% compared with spruce growing in pure spruce stands. In a mixed stand of European aspen and Norway spruce growing on farm land, the 36-year-old aspen overstory produced 480 m(3) ha(-1). The spruce understory had a reduced yield compared with pure spruce stands. Depending on the biofuel price and the market for utilisation of biofuel the forest owner might use the broad-leaves as biofuel. Some studies indicate that the harvested biomass yield of birch in a mixed stand of birch and spruce could be 48 t d.w.ha(-1). (C) 2002 Elsevier Science Ltd. All rights reserved.