Fig. 2From: Effect of nitrogen addition on soil CO2 efflux and fine root biomass in maple monocultures of the hyrcanian regionSeasonal variations (mean ± SD; n = 3 per month) of soil CO2 efflux measured at different level of N addition (N0: Control, N1: 5, N2: 10, and N3:15 g N m−2 year−1)Back to article page