Intra-annual height increment of Pinus sylvestris at high latitudes in Finland.
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.
Salminen
Hannu
H
Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland. hannu.salminen@metla.fi
Jalkanen
Risto
R
D001110:Arctic Regions; D003081:Cold Climate; D005387:Finland; D008954:Models, Biological; D017440:Photoperiod; D041605:Pinus sylvestris / Q000254:growth & development*; D012621:Seasons; D013696:Temperature