Fig. 2
From: Seasonal dynamics of stem N2O exchange follow the physiological activity of boreal trees
Seasonal courses of basic environmental variables. The variables were measured at the SMEAR II station from June 2014 to May 2015: (a) Daily mean air temperature within the forest stand at 8 m height; (b) daily mean soil temperature and (c) soil volumetric water content (VWC), both in C1-horizon (38–60 cm in depth); and (d) daily sum of photosynthetically active radiation (PAR). The open circles represent monthly means (± standard error), and the black circles indicate monthly means ( ± standard error) calculated for the flux measurement days only. The period of continuous snow cover (from mid-December 2014 to early April 2015) is indicated in Fig. 2b
