Fig. 5
From: Seasonal dynamics of stem N2O exchange follow the physiological activity of boreal trees
Seasonal N2O fluxes in tree stems and forest floor. N2O fluxes in stems of birch (a), spruce (b), and pine (c), and in forest floor (d) are presented at annual scale (black columns), for vegetation season (March–September, grey columns), and for dormant season (October–February, white columns). The fluxes (means ± standard error) are sums of N2O exchanged over one year, vegetation season, or dormant season, respectively, and expressed per m2 of stem or soil surface area. Positive flux values indicate N2O emission, negative values N2O uptake. Mean annual volumetric water contents ( ± standard error) of the plots were as follow: wet plot, 0.81 ± 0.02 m3 m−3; moderately wet plot, 0.40 ± 0.02 m3 m−3; and dry plot, 0.21 ± 0.01 m3 m−3. The dry plot did not have spruce or birch trees. Stem fluxes were measured from three trees per species at each plot (n = 3). Forest floor fluxes were measured at three positions at the wet and moderately wet plots (n = 3) and at six positions at the dry plot (n = 6). Statistically significant differences between fluxes over vegetation and dormant season at p < 0.05 are indicated by asterisks. The percentage contributions of fluxes over the vegetation and dormant season to the annual fluxes (defined as 100%) are indicated above the bars
