Response Of Greenhouse Gas Fluxes To The Addition Of Nitrogen And Phosphorous In Subtropical Fir Forest

Global change is a major challenge for human being today, and the most concerned issues are greenhouse effect and global warming. In the past century, global warming is the main feature of the significant global change, as the global average surface temperature increased from0.3to0.6℃,Forests is the main part of the terrestrial ecosystems,and forest soil is an important source and sink of CO2, CH4, N2O and other greenhouse gases. Research of the effect of nitrogen deposition on greenhouse gas emission/absorption of forest soil has become a hot issue. China has become on of the world’s top three nitrogen deposition concentration areas, and with the rapid economic growth, the amount of nitrogen deposition will continue to rise. But there were few research about the effect of nitrogen deposition on the main greenhouse gases fluxes.This study was carried out at Shixi forest of Qianyanzhou station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences. Using the most common method for sampling and analyzing gas sample, the static chamber-gas chromatography method, we studied the greenhouse gas fluxes of the fir forest soil, exploring the response pattern of the major greenhouse gases of nitrogen and phosphorus addition and the mechanism of greenhouse gas fluxes of forest soil. This experiment was laid in July2012in Shixi forest, Guanxi town, Taihe County, Ji’an City, Jiangxi province. We laid24plots, with each plot’s area of20m x20m. It had six treatments:no fertilizer (CK), P fertilizer (P), nitrogen (N1),high nitrogen (N2),low nitrogen and phosphorus (N1P),high nitrogen and phosphorus (N2P),and every treatment had4replicates. After long-term monitoring, the conclusions are as follows:1、Fertilization affected surface CO2flux,and the CO2fluxes showed an obvious seasonal variation,highest flux in summer,lowest in winter. Treatments of low nitrogen and phosphorus,low nitrogen did not change surface CO2flux significantly, the high nitrogen treatment reduced soil CO2emissions by22%,compared with the control plots. Mean while,phosphorus and high nitrogen and phosphorus reduced the CO2emission rate.2,Qianyanzhou fir forest soil acted as a sink of methane,and in the measurement period, there were significant seasonal variation. Methane absorption ability is high in mid-August to mid-October, and it was lower in the winter. When the spring came, the absorption of methane started growth gradually. The application of nitrogen fertilizer inhibited the absorption of methane.3、High nitrogen and high nitrogen and phosphorus significantly improved surface N2O emissions (P<0.01). low nitrogen and low nitrogen plus phosphorus increased surface N2O emissions, but did not reach the level of significance. The effect of fertilization on the N2O emissions was mainly observed in the early stages of fertilization, within a week after fertilization, nitrogen fertilization will lead to an obvious peak of N2O, and as time goes on, N2O emissions decreased until there was no significant difference compared with the blank.