%0 Research article
%T Carbon dioxide exchange of Scots pine shoots as estimated by a biochemical model and cuvette field measurements
%A Aalto, Tuula
%D 1998
%J Silva Fennica
%V 32
%N 4
%R doi:10.14214/sf.674
%U https://silvafennica.fi/article/674
%X A biochemical model was used to calculate CO2 fluxes to Scots pine  shoots in two boreal measurement stations, Hyytiälä in southern Finland  (61°51’N, 24°17’E) and Värriö in northern Finland (67°46’N, 29°35’E).  The results of the model were compared with cuvette measurements  performed in field conditions. A differential equation for change in gas  concentration inside a closed cuvette was constructed and solved in  order to obtain conductances and fluxes. The results were generally in a  good agreement, the correlation coefficients varied from 0.74 to 0.95.  Some discrepancies were also found. The model followed more intensively  changes in temperature. This could be seen in northern Finland  measurements at low temperatures (< 18 °C). The modelled temperature  response indicated low fluxes at low temperatures, but measurements did  not show any decrease. The irradiation response was relatively similar  in both measuring sites and according to the model. Cuvette measurements  showed slightly smaller quantum yields as a result from shading of the  needles. The temperature dependences of the biochemical model parameters  Jmax and Vc(max) were re-evaluated from the field measurements. The  results for Vc(max) agreed well with earlier estimations, while the  results for Jmax indicated relatively high values at low temperatures  especially in northern Finland. Exponential fitting produced also  substomatal concentrations of CO2, which agreed quite well with the  model. The daily minimum of substomatal/ambient concentration ratio  varied from 0.4 to 0.8.