Differences of Latvia’s silver birch (Betula pendula Roth.) provenances
2012
Gailis, A., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Augustovs, J., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Purvins, A., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Jansons, A., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
Birch is one of the most widespread tree species in Latvia (30% from the area). During the past century it was not viewed as valuable tree species in most of the countries around the Baltic Sea, therefore limited number of experiments were carried out. In Latvia, intensive breeding process of the species was started from the year 1995 with selection of candidate stands, their inventories and selection of plus trees for establishment of seed orchards and progeny trials. Currently these two seed orchards cover almost all the demand for birch seeds that has been constantly growing mainly due to afforestation of former arable lands and, in recent years, also planting in forest. Established progeny trials can provide information not only for selection of new set of tested seed orchard clones, but also general trends in comparison of provenances across Latvia. Aim of the study is to analyze the differences and geographical patterns of provenances. Material was collected from plus trees and good quality trees from 37 stands representing all regions of Latvia. In 3 trials altogether 921 open-pollinated family was used, majority of them were represented in two (331) or all three (316) trials, but portion (274) only in one trial. Therefore number of families per site ranges from 613 to 653. Design was either large block plots (32 trees) in 4 replications or single tree plots. All trials were established on abandoned agricultural land with initial spacing 2×2 m or 2×2.5 m using one-year-old container plants. For the analysis only 6 or 10 highest trees per block-plot or family were used. Results reveal that average tree height in different test sites reaches 6.3 m to 7.6 m, diameter of the thickest branch up to two meters height is on average 10mm and branch angle in the middle part of the green crown 45°. Frequency of trees with spike knots varies greatly among trials due to both genetic and environmental reasons: from 14% up to 38%.
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