Impact of land-use management on nitrogen transformation in a mountain forest ecosystem in the north of Iran

Soil inorganic N is one of the most important soil quality indexes, which may be influenced by land-use change. The historical conversion of land-use from native vegetation to agriculture resulted in sharp declines in soil N dynamics. This study was conducted to determine the soil inorganic N concentrations and net N mineralization rate in four common types of land-uses in the mountain forest area in the north of Iran, namely arable land, pine plantation, ash plantation, and beech stand. The soil samples were taken from top mineral soil layer (5 cm) in each site randomly (n=6) during August- September 2010. Beech stand and ash plantation showed significantly higher total nitrogen compared with arable land and pine plantation, while extractable NH4+-N concentration was significantly greater in Beech stand compare to arable soils (p<0.05). No significantly difference was found in Net N mineralization, net nitrification and net ammonification rates among different land-uses. Results showed that net N mineralization and ammonification were occurred just in the soil of Ash plantation during the incubation time. Our findings suggested that conversion of Hyrcanian forests areas to pine plantation and agricultural land can disrupt soil natural activities and affect extremely soil quality.