© 2007 Heron Publishing—Victoria, Canada
Intra-annual height increment of Pinus sylvestris at high latitudes in Finland
Hannu Salminen (1, 2) and Risto Jalkanen (1)
1. Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland / 2. Corresponding author (hannu.salminen@metla.fi) / Received October 17, 2006; accepted January 8, 2007; published online June 1, 2007
Summary
Intra-annual height growth of Scots pine (Pinus sylvestris L.) in four stands was followed for up to four growing seasons (2000–2003) in the northern boreal zone in Lapland. Elongation
of the leader shoot correlated with temperature sum expressed as degree-days. Total length of the leader shoot correlated
with growth rate but not with duration of the height-growth period. The longer the annual shoot at the end of the season,
the greater the height increment per degree- and growing day. Height-growth cessation was defined as the date when 95% of
the total shoot length was achieved. In all stands and all years, height growth ceased when, on average, 41% of the relative
temperature sum of the site was achieved (range of variation 38–43%). The relative temperature sum was calculated by dividing
the actual temperature sum by the long-term mean for the site. Our results suggest that annual height growth is finished when
a location-specific temperature sum threshold is attained.
Keywords:
growth cessation, growth rate, phenology, Scots pine, temperature, tree line.
