Fig. 4From: Effect of nitrogen addition on soil CO2 efflux and fine root biomass in maple monocultures of the hyrcanian regionRelationships between soil CO2 efflux and fine root biomass measured at different N addition (N0: Control, N1: 5, N2: 10, and N3:15 g N m−2 year−1); Std. Err. Est Standard Error of Estimate, NRSME normalized RMSEBack to article page