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Productivity

Biomass production rates of more than 20 tons per hectare and year were reported after 3 to 5 year of growth in fertilized experimental willow stands grown in Sweden. However, biomass yields in commercial willow plantations grown in southern and central Sweden are usually in the range 5 to 15 tons per hectare and year, with great variation between growers and sites. In the near future, the mean yields in commercial willow plantations are expected to significantly increase, due to the more frequent use of improved hybrid varieties and better management of the plantations.

The breeding work on hybrid aspen in Sweden has been going on since the first hybrid was produced over 50 years ago. The productivity of the material has increased, from about 16 m3 per hectare and year, to an estimated level of about 25 m3 per hectare and year with the now selected and recommended plant material.

productivity figures

The effect of genetic breeding and selection work on hybrid aspen productivity in Sweden. From the initial plant material the mean annual increment reached about 16 m3per hectare and year of stem wood in stands on fertile soils. From plant material selected during the 1980's about 20 m3 per hectare and year could be expected. A selection of the 15 most superior clones, i.e. the commercial selection today, will probably result in a production level of about 25 m3 per hectare and year of stem wood as an average.

Knowledge of possible production levels for poplar is fairly unknown for North-European conditions. The experience is also based mainly on a single clone, OP42. However, the few comparisons made so far indicate that poplar seems to have a slightly higher average growth rate than what has been recorded for hybrid aspen.