中文摘要：

施氮或氮沉降对土壤温室气体通量影响已有比较深入的研究,但施氮对不同有机碳水平的土壤温室气体通量影响及其差异的研究较少.本研究以我国南方广泛种植的桉树人工林为对象,采用野外控制实验和室内分析,比较研究4种施氮处理(对照C:0 kg·hm-2;低氮L:84.2 kg·hm-2;中氮M:166.8 kg·hm-2;高氮H:333.7 kg·hm-2)对土壤有机碳水平存在显著性差异的2块桉树林样地土壤-大气界面温室气体(CO2、N2O和CH4)通量的影响.结果表明:1施氮对CO2和N2O排放通量有明显'激发效应',氮肥施用一个月后各个施氮处理土壤CO2和N2O排放通量出现最大值,随着时间推移至生长季后期CO2和N2O排放通量逐渐降低,差异逐渐缩小.施氮对CH4吸收通量的影响不显著(P】0.05).2施氮强度和土壤有机碳水平均显著促进了CO2和N2O排放(P【0.001),但对CH4吸收没有显著影响(P】0.05);高土壤有机碳水平样地CO2和N2O排放通量显著高于低水平土壤有机碳样地(P【0.01).3施氮和土壤有机碳水平对CO2和N2O排放通量的影响存在显著的交互作用(P【0.05).与低土壤有机碳水平样地比较,高土壤有机碳水平样地CO2和N2O排放通量对施氮更为敏感:低氮水平就能显著促进CO2和N2O的排放.上述结果表明:施氮对桉树林温室气体排放通量的影响既与施氮强度有关,也与土壤有机碳水平密切相关.估算不同施氮水平下的温室气体通量变化时,由土壤有机碳不同带来的温室气体通量差异不可忽视.

英文摘要：

The effects of nitrogen fertilization or nitrogen deposition on soil greenhouse gases fluxes has been well studied, while little has been piloted about the effects of nitrogen application on soil greenhouse gas fluxes and its discrepancy with different soil organic carbon content. In our study, we conducted field control experiment in a young Eucalyptus plantation in Southeast China. We compared the effects of 4 levels of nitrogen fertilization ( Control:0 kg·hm -2; Low N:84. 2 kg·hm-2; Medium N:166. 8 kg·hm-2; High N:333. 7 kg·hm-2 ) on soil GHGs fluxes from 2 sites ( LC and HC) with significantly different soil organic carbon ( SOC) content ( P﹤0. 05). The results showed: ① Fertilization had significant priming effect on CO2 and N2O emission fluxes. One month after fertilization, both CO2 and N2 O had the flux peak and decreased gradually, and the difference among the treatments disappeared at the end of the growing season. However, fertilization had no significant effect on CH4 oxidation between the 2 sites. ② Fertilization and SOC were two crucial factors that had significant effects on CO2 and N2 O emission. Fertilization had a significant positive effect on CO2 and N2 O emission fluxes ( P ﹤0. 001 ) . CH4 oxidation rates decreased with the increasing N addition, but there was no statistical difference ( P ﹥0. 05 ) . The CO2 and N2 O emission fluxes were significantly higher in HC than those in LC ( P ﹤0. 01 ) . ③Fertilization and SOC had great interactive effect on CO2 and N2O emission (P﹤0. 05). Compared with fluxes in LC, the fluxes in HC were much more sensitive to N input: low N could remarkably stimulate the CO2 and N2 O emission. In conclusion, the effects of nitrogen fertilization on soil GHGs fluxes were not only in connection with the intensify of nitrogen, but also closely tied to the SOC content. When we assess the effects of nitrogen on soil GHGs fluxes, the difference induced by SOC should not be ignored.