Press release 06.02.2006
Narrow-crowned spruce might be suitable for growing as a fibre-crop tree with short-term rotation. When the normal-crowned and narrow-crowned forms of spruce were compared, the narrow-crowned spruce used its per-unit-area of growth more efficiently. This means that higher planting densities could be used for narrow-crowned spruce seedlings. These findings were reported in a study made at the Finnish Forest Research Institute (Metla).
The largest natural stand of narrow-crowned spruce, or pendula spruce (Picea abies forma pendula), is located in Mäntsälä, Southern Finland, where approximately twenty pendula spruces grow in one stand. The branches of pendula spruce are thin hanging and its maximum crown width is less than a metre.
Clones and progenies of 13 to18-year-old pendula spruces and normal-crowned spruces were compared on a test site in southern Finland. The stem fresh weight of pendula spruce was observed to be less than that of normal-crowned spruce. Conversely, the mean harvest index calculated of the total above-ground biomass of pendula spruce was clearly greater than that of normal-crowned spruce.
No significant differences were observed in the characteristics of paper made from the different crown-type trees. Fibres were somewhat longer and more uniform in pendula spruce.
No significant differences were observed in incidents of root rot between the different crown-type trees. Interestingly, inter-tree competition seemed to decrease the incidence of root rot.
Financial calculations showed that the pendula spruce plantations were slightly more profitable than planting normal-crowned spruce. A rotation period of 30 years without thinning was used for pendula spruce, whereas the silvicultural forest management guidelines were followed for normal-crowned spruce.
A challenge in adopting the results in practice involves development of efficient seed and seedling breeding methods for pendula spruce. In plant production, cuttings or some other growth-related production method must be used, which inevitably causes higher than normal seedling production costs.