Simulated Nitrogen Deposition Reduces the Concentration of Soil Base Cations in Acer velutinum Bioss. Plantation, North of Iran

The effect of simulated N deposition on concentration of soil base cations and net N mineralization was studied in Acer velutinum Bioss. plantation in Hyrcanian forest, North Iran. Nine plots were established in May 2015 and three N addition treatments were designed: N0 (control), N1 (50 kg N ha−1 year−1), and N2 (100 kg N ha−1 year−1), respectively. NH4NO3 solution was monthly sprayed on the forest floor during 1 year starting from May 2015. Soil pH, EC, organic carbon (OC), and concentrations of total N, \( {\mathrm{NO}}_3^{-} \), \( {\mathrm{NH}}_4^{+} \), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were measured. Nitrogen treatments significantly decreased soil pH and EC. The concentration of N in N2 was significantly greater than N0 (control). Compared to N0, the soil P, K, Ca, and Mg decreased in N treatments, but soil OC, \( {\mathrm{NO}}_3^{-} \), and \( {\mathrm{NH}}_4^{+} \) increased. Net N mineralization rates were positive but showed no significant difference between treatments. As the first work in Iranian Hyrcanian forests, this study showed that the concentration of soil nutrients can be changed under N additions in this area, and these new results can be considered as suitable data for predicting and modeling future trees’ growth and forest ecosystems’ production in Hyrcanian forests.