Genetic variation in frost tolerance, juvenile growth and timber production in Russian larches (Larix Mill.)

Larch (Larix sp Mill.) is an important component in boreal montane and subalpine forests in the northern hemisphere. Macrofossils of larch in the Scandinavian mountains prove the existence of larch in Scandinavia after the last ice age, Siberian or Russian larch is now considered as an indigenous tree species of Sweden. The larches of Russia are of interest for their production potential and wood quality. The aim of this thesis was to determine frost resistance, juvenile growth, stem straightness and branch traits in a 5-year-old combined provenance/progeny test with Larix sukaczewii, L. sibirica, L. gmelinii and L. cajanderi originating from Russia and tested on three sites in Sweden. An evaluation of genetic parameters in this half-sib family material was also made. The yield in 37-86 year old field tests of L. sukaczewii and Russian larch hybrids was also evaluated. The results indicate that larches from western Russia, L. sukaczewii were least damaged in the artificial freezing test, had highest survival in the field trials and had the best stem quality. The most northern provenances of this species had, however, poorer growth and lower survival, especially on the southern test site. L. sibirica from central Siberia and continental provenances of L. cajanderi and L. gmelinii were not adapted to any of the sites. Among provenances of L. gmelinii and L. cajanderi those with more maritime origin showed generally better adaptation than those from more continental areas. Geographic and climatic variables of provenance origin were important for the performance of the provenances. At the southern test site, provenances from northern latitudes and strongly continental areas in Russia showed poor growth and survival. On the two test sites located in harsh climates, provenances originating in climates similar to the test sites showed best survival. This means a northern transfer of 2-3 latitudes for the most northern site. The yield in 37- 40 year-old L. sukaczewii was higher than Picea abies, Pinus sylvestris and Betula pendula on two test sites in central Sweden. In northern Sweden one provenance from Arkhangelsk showed higher yield after 50 years compared to one provenance from the central Ural Mountains. L. sukaczewii of Raivola origin demonstrated a wide ecological range with a yield of about 7 m3/ha/year for 76 years, in a local continental climate in central Sweden and a maritime site in northern Norway. Small test plots with the hybrid L. decidua x L. sukaczewii had substantially higher production than L. sukaczewii