Abstract: In order to determine the effects of increased nitrogen deposition on soil organic carbon and nutrients in mixed broadleaved-Korean pine forest in Xiaoxing’an Mountains, China, a simulated nitrogen deposition field experiment was conducted from June 2008 to August 2010. Four nitrogen treatments (control, low, medium and high nitrogen) used CO(NH₂)₂ solution of 0, 30, 60 and 120 kg·hm^-2·a^-1. We collected 0-20, 20-40, 40-60 cm soil samples and measured soil organic carbon (SOC), total nitrogen (TN), alkali-hydrolyzable N(HN), available phosphorus (AP) and available potassium (AK) in June and October, 2009 and 2010. For two years experiments, we found that SOC and TN contents decreased with the increase of soil depth. Low and medium nitrogen treatments significantly increased SOC, HN and AK contents (P<0.05). While, medium, high nitrogen treatments significantly reduced AP content (P<0.05), and there was no significant changes of the TN before and after simulated nitrogen deposition field experiment (P>0.05). Regression analysis showed that significant positive associations were found between the SOC and TN, HN, AP, AK (P<0.001). The study suggests that continuous nitrogen deposition may increase the soil organic carbon pool and soil fertility in the mixed broadleaved-Korean pine forest ecosystem.

Key words: nitrogen deposition, mixed broadleaved-Korean pine forest, soil organic carbon, soil nutrients