Spring initiation and autumn cessation of boreal coniferous forest CO2 exchange assessed by meteorological and biological variables
Article first published online: 26 AUG 2009
©2009 The Authors Journal compilation © 2009 Blackwell Munksgaard
Volume 61, Issue 5, pages 701–717, November 2009
How to Cite
THUM, T., AALTO, T., LAURILA, T., AURELA, M., HATAKKA, J., LINDROTH, A. and VESALA, T. (2009), Spring initiation and autumn cessation of boreal coniferous forest CO2 exchange assessed by meteorological and biological variables. Tellus B, 61: 701–717. doi: 10.1111/j.1600-0889.2009.00441.x
- Issue published online: 15 OCT 2009
- Article first published online: 26 AUG 2009
- (Manuscript received 18 February 2009; in final form 17 August 2009)
We studied the commencement and finishing of the growing season using different air temperature indices, the surface albedo, the chlorophyll fluorescence (Fv/Fm) and the carbon dioxide (CO2) tropospheric concentration, together with eddy covariance measurements of CO2 flux. We used CO2 flux data from four boreal coniferous forest sites covering a wide latitudinal range, and CO2 concentration measurements from Sammaltunturi in Pallas. The CO2 gas exchange was taken as the primary determinant for the growing season to which other methods were compared.
Indices based on the cumulative temperature sum and the variation in daily mean temperature were successfully used for approximating the start and cessation of the growing season. The beginning of snow melt was a successful predictor of the onset of the growing season. The chlorophyll fluorescence parameter Fv/Fm and the CO2 concentration were good indicators of both the commencement and cessation of the growing season. By a derivative estimation method for the CO2 concentration, we were also able to capture the larger-scale spring recovery. The trends of the CO2 concentration and temperature indices at Pallas/Sammaltunturi were studied over an 11-yr time period, and a significant tendency towards an earlier spring was observed. This tendency was not observed at the other sites.