Biogeographic differences in shoot elongation pattern among European Scots pine populations

Results are presented of shoot elongation of 10-year-old trees of 19 European Pinus sylvestris populations growing in a provenance experiment in central Poland. Populations exhibited different shoot elongation patterns with montane southern (40-44°N) and lowland northern (58-60°N) populations having lower growth rates and earlier onset of growth cessation than those from the central lowland part (47-55°N) of European species' range. Average absolute growth rates ranged from 6.6 mm per day for populations of southern origin to 9.2 mm per day for populations from central Europe. Shoot elongation period explained ca. 50-60% and differences in growth rate from 40 to 50% of total differences in annual increment among population groups. There was a linear relationship (r²=0.73, P<0.0001) between mean annual temperature (m.a.t.) of seed origin and mean relative growth rate. Populations originating from seeds collected in colder regions (3-6° m.a.t.) had shorter shoot elongation periods than those from warmer (7-10°C m.a.t.) environments. The duration of the shoot elongation period alone explained 86% of total height variation at age 10 years in this experimental site and from 42 to 80% variation in five other sites (in Poland and Croatia) established with same seed lots. Shoot elongation period was negatively related to the proportion of mass allocated to roots, underlying a possible linkage between shoot phenology and below-ground growth.