© 2005 Heron Publishing—Victoria, Canada
Variation in needle longevity is related to needle-fascicle production rate in Pinus sylvestris
Margus Pensa (1, 2, 3) and Risto Jalkanen (1)
1. Rovaniemi Research Station, Finnish Forest Research Institute, P.O. Box 16, Rovaniemi FIN-96301, Finland / 2. North-East Estonian Department, Institute of Ecology, Tallinn Pedagogical University, Pargi 15, Jõhvi 41537, Estonia / 3. Corresponding author (margus.pensa@metla.fi) / Received October 6, 2004; accepted February 12, 2005; published online August 1, 2005
Summary
Latitudinal variation in needle longevity of conifers in response to climatic variability is a well-known phenomenon, but
its significance has only rarely been studied. Scots pine (Pinus sylvestris L.) stands were investigated in four locations in Lapland (northern Finland and northern Sweden, 67–68° N) and in four locations
in Estonia (59° N) to test the hypothesis that plasticity in needle longevity results in similar needle biomass per foliated
shoot length across latitudes. The needle-trace method (NTM) revealed the dynamics of needle fascicles attached to stem shoots.
Long-term mean needle age was 2 years greater in Lapland than in Estonia. In both regions, mean needle age was strongly and
negatively related to yearly needle-fascicle production rate relative to the number of needles on the same shoot axis. Although
significantly fewer needle-fascicles were produced annually in trees in Lapland than in Estonia, the overall number of fascicles
attached to the stem shoots, needle-fascicle density and individual needle dry mass did not differ between regions. Consequently,
needle biomass per foliated shoot length was similar in trees in both regions. Thus, our results support the theory that plasticity
in needle longevity helps Scots pine to compensate for reduced needle production so that the same foliar biomass per shoot
is retained under a wide range of growth conditions.
Keywords:
intra-specific variation, latitude, mean needle age, needle biomass, needle dynamics, needle-trace method.
