Impacts Of Simulated Nitrogen Deposition On Soil Nitrogen Mineralization Rate In Betula Platyphylla Secondary Forest In Southern Of Daxing’an Mountains

In2013, we made a continuous investigation of soil N availability and N mineralization from May to September in Betula platyphylla ecosystem in Southern of Daxing’an Mountains by using close-top Incubation. In order to reveal the effects of different nitrogen input on soil nitrogen mineralization, we executed some treatments to the trees investigated including nitrogen input. Four N treatments, high N (40kg·hm-2·a-1)、Middle N(20kg·hm-2·a-1)、Low(10kg·hm-2·a-1)、Control(0kg·hm-2·a-1), were established in Betula platyphylla forests. We can summarize the above points as following:(1) Available nitrogen content was significantly different in growing season in Betula platyphylla forest. Available nitrogen content climbed to the top at July was96.03±1.73mg·kg-1and declined to the bottom at May, it was23.25±0.76mg·kg-1Ammonia nitrogen was the major form of inorganic nitrogen, and the proportion of NH4-N to the total inorganic was60%, NO3-N to the total inorganic was40%.(2) Input nitrogen to improve the Betula platyphylla forest soil nitrogen mineralization rates. Content of soil ammonium nitrogen, nitrate and effectively nitrogen increases with nitrogen deposition increased. Nitrogen deposition also increased soil ammonification rate, nitrification rate and nitrogen mineralization rate significantly, which the ammoniated rate is growth greater than the nitrification rate. Two-way ANOVA analysis showed that there was a significant interaction between January and N treatments (P<0.001).(3) Net nitrogen mineralization rate of soil has closely relation with organic carbon and total nitrogen, the contribution of total nitrogen to net nitrogen mineralization rate is10%—30%, organic carbon is40%—97%, and both of them have reached a very significantly level(P<0.001). Multiple regression analysis showed that organic carbon mineralization of nitrogen occupies the ratio between net mineralization rate is more closely than organic carbon.