Use of modeled photosynthesis and decomposition to describe tree growth at the northern tree line

• Published in: Tree Physiology
• Main Authors: Berninger, Frank, Hari, Pertti, Nikinmaa, Eero, Lindholm, Markus, Meriläinen, Jouko
• Format: Text
• Language: English
• Published: Oxford University Press 2004
• Subjects: Original Articles; Subarctic
• Online Access: http://treephys.oxfordjournals.org/cgi/content/short/24/2/193; https://doi.org/10.1093/treephys/24.2.193

Growth of subarctic Scots pine ( Pinus sylvestris L.) trees was investigated by a combination of process-based models and dendroecological approaches. Tree ring width indices were strongly autocorrelated and correlated with simulated photosynthetic production of the previous year and with organic matter N mineralization of the current year. An autoregressive model, with photosynthesis and N mineralization as external inputs, explained growth of the trees well. However, relationships for the period 1950–1992 differed significantly from relationships for the period 1876–1949; the slope of the regression of tree ring width index and photosynthesis was lower for the 1950–1992 period. Also, the autocorrelation structure of the data changed. First-order autocorrelation decreased and second-order autocorrelation increased from the earlier to the later period. This means that growth is becoming less sensitive to variations in photosynthetic production, whereas the relationships between growth and N mineralization are remaining fairly constant. We postulate that, although photosynthesis has increased in response to increasing CO 2 concentrations, tree growth rate cannot parallel the increase in photosynthesis because potential growth rate is limited directly by temperature.