Influence of lammas shoots on height of young Scots pines in Latvia
Latvian State Forest Institute ‘Silava’, Rigas 111, LV2169 Salaspils, Latvia
Scots pine is a commercially important tree species in northern Europe. Climate changes in combination with genetics cause differences in the tree growth rhythm, including the formation of lammas shoots. The aim of the study was to assess the relation between the occurrence of lammas shoots and the height of young Scots pines and its implications in tree breeding. Tree height was repeatedly measured, and the presence of lammas shoots was assessed at the end of the 4th through 8th growing seasons in two open-pollinated progeny trials (Daugmale and Norupe, both including the same 61 families) in the central part of Latvia. The proportion of trees with lammas shoots (max. 23%) decreased over the observation years. In both trials, at the age of 7 years, trees that had formed lammas shoot during at least one of the observed years were significantly (P < 0.001) higher than trees with no lammas shoots: 226 ± 3.5 cm vs 213 ± 3.3 cm in Norupe and 146 ± 3.9 cm vs 121 ± 1.9 cm in Daugmale, respectively. When only dominant trees (1,000 ha-1) were considered, the height superiority of trees with lammas shoots remained in Daugmale (trial with highest proportion of trees with lammas shoots), but not in Norupe. The earliest formed lammas shoots (assessed in the 4th growing season) had the strongest effect on the tree height. A correlation between the mean height and the proportion of trees with lammas shoots in the particular family was not found (P > 0.05).