Experimental Study On The Response Of Plant And Soil Of Betula Ermanii Forest To Nitrogen Deposition, Changbai Mountain

In recent decades, emissions of nitrogen compounds into the atmosphere by human activity increased. This has led to significant increases in atmospheric nitrogen deposition. Increased nitrogen deposition can lead to a series of ecological and environmental problems. Forest ecosystem is a major recipient of nitrogen deposition and forest ecosystem plays an important role in maintaining global ecological balance. It is very significant to study the effects of nitrogen deposition on forest ecosystems.Experimental area is located in Betula ermanii forest in Changbai Mountain. We selected three communities: Betula ermanii-crab communities, Betula ermanii-Veratrum communities and Betula ermanii-Deyeuxia angustifolia communities. The experiment is divided into two parts: field experiments and laboratory experiments. Field experiment is to add nitrogen fertilizer in Betula ermanii forest when plants grow. To discusses the different effects of different level and different forms of nitrogen deposition on forest ecosystem, we selected three forms of nitrogen fertilizer, mix-N(NH4NO3), NH4+-N[(NH4)2SO4], NO3--N(KNO3), and set four nitrogen deposition gradients: 0 gNm-2a-1, 5 gNm-2a-1, 10 gNm-2a-1, 15 gNm-2a-1. Laboratory experiment is to add nitrogen in the soil samples and then put them in an incubator. We choose the mix-N and select three level of nitrogen deposition: low, medium and the high.The results of the experiment show that the increased nitrogen deposition have obvious effects on plant growth, community structure and soil fertility. Main conclusions are:(1) Increased nitrogen deposition promotes the growth of the plant, expect the Betula ermanii. The plant height, leaf area and biomass of crab grass, Veratrum and Deyeuxia angustifolia have increased markedly because of the application of nitrogen fertilizer. And the growth of Deyeuxia angustifolia increased most significantly.(2) The increase in nitrogen deposition will result in decreased soil organic matter content.(3) The increase in nitrogen deposition will result in increase of content of total nitrogen and available nitrogen in soil. Increased nitrogen deposition will have an impact on soil nitrogen transport and transformation. It can improve the effectiveness of nitrogen in soil.(4) Increased nitrogen deposition will reduce the phosphorus content in soil. And the more nitrogen deposition lead to the total phosphorus reduced more. On the whole, the trend of the available phosphorus and is similar with the total phosphorus.(5) The difference of the influence of nitrogen deposition on plant and soil is not obvious.