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For biomass forestry in the inland parts of southern and central Finland, the obvious choice of willow species is Salix myrsinifolia. However, selection of clones of indigenous species has not yet been completed and more research and selection is needed. In the Piipsanneva old peatland trial, indigenous species of willow, mostly clones of S. myrsinifolia and S. phylicifolia, were compared in terms of biomass production, coppicing, height growth and diameter distributions. In this trial, the mean annual biomass production was not particularly high; more important results were attained in the ranking of clones. This trial strengthens the hypothesis that, over the long term, the biomass production of S. myrsinifolia is higher than that of S. phylicifolia. It was supposed that behind the highest yield there was a clone with uniform quality, one whose diameter distribution would be narrow and positively skewed. Comparisons of parameters of Weibull functions showed that the distributions of the best clones were wide, indicating that those clones use the whole growth space better than these with narrow distribution.

In sections 1-3 of this report, brief reviews are presented of the genus Salix and its use (especially for biomass) in Finland. In section 4, the results from early breeding programmes in Finland (1910-79) are analysed. In section 5, selection of biomass willows in the 1980s is reviewed. Some 63 exotic willow clones (mainly S. burjatica and S. viminalis) from Sweden were screened at the Kopparnas willow research site, S. Finland, from 1983 to 1989. S. viminalis showed consistently high yields. The yield variation of S. burjatica was large because of an outbreak of rust (Melampsora sp.), followed by lowered winter hardiness. Three S. viminalis clones were recommended for S. Finland: 78-0-183 (Sweden), E7888 (Somero, Finland) and 78-0-21 (Sweden). Selection of indigenous species and clones was based mainly on a collection of 375 clones of the Foundation of Forest Tree Breeding and a collection of 566 clones of the Finnish 4H-organization. The clones were grown at Suomusjarvi, Nurmijarvi, Kannus and Haapavesi. S. myrsinifolia was the most productive; 5 clones were recommended: E6631 (Kulaa), K2322 (Heinavesi), E6695 (Hartola), V75 (Mikkeli) and V78 (Loppi). S. phylicifolia was the second most productive species and the most promising clones were E6682 (Juva), V766 (Pieksamaki) and V754 (Kuru). Willow hybridization studies have also been carried out. Further intraspecific crossings of geographically distant S. myrsinifolia clones are recommended. Based on research results from 1910 to 1990, S. viminalis is recommended for biomass forestry in S. Finland and S. myrsinifolia is recommended for research in other areas. A list of Salix species, subspecies, varieties, forms, hybrids and synonyms is given in an appendix (pp. 44-58).

Four different methods of truncation selection were studied in a population consisting of a large number of unrelated full sib families of equal size: phenotype selection, family selection, within-family selection and combined index selection (optimal weighting of individual and family performance to get the best prediction of breeding value). Methods were developed for calculating diversity (ârelative effective family numberâ) for the different selection methods. Numerical calculations were made for genetic gain and diversity. Model assumptions are additive gene control and normal distribution. Phenotypic was good at high heritabilities and between family at low heritabilities. Loss of diversity was strongly dependent on selection method and selection strength. Compared at the same diversity, genetic gain was lower for combined index compared to phenotypic. There is a need for methods combining the goals gain and diversity. The PDF includes an abstract in Finnish.

Possibilities of developing suitable willow ( spp.) clones for short-rotation forestry on mined peatlands in the north-western area of Finland were studied in a field experiment in which 300 willow clones were tested during 1985â87. Most of the tested clones started to grow from cuttings on limed and fertilized peat soil. L. clones of southern origin had a higher leafless above ground biomass production than the well adapted control clone and the local Finnish willows, but their winter hardiness was not satisfactory. The growth habit of some southern willows was also better than that of the control clone. It was also possible to select clones with good sprouting capacity. There were few Calisb. clones of Finnish origin, which had better cold tolerance than all other willows tested and higher biomass production than that of the control clone. The most critical factor to be selected for this is the optimal combination of winter hardiness and biomass production. This is attempted by selecting clones on the basis of this experiment for a breeding program.SalixSalix viminalisSalix myrsinifolia

Harvest index and number of associated traits were measured in a 16-year-old Scots pine ( L.) progeny test based on full-sib families. It was found that harvest index is a highly heritable trait and that a number of yield components are positively correlated with it. It is suggested that harvest index and tree ideotypes should be the basis of selection in cultivated trees. It is emphasized that an integrated approach to tree improvement including silviculture, soil science, industrial and economic constraints and tree breeding is a prerequisite for maximal response.Pinus sylvestris

Metsänhoitajien jatkokurssit : 1952. 7.