摘要:以2年生马尾松（Pinus massoniana）盆栽苗土壤为对象，通过施氮肥模拟氮沉降对土壤理化性质、微生物群落结构及温室气体释放的影响，探明氮沉降对森林土壤温室气体释放的驱动机制。结果表明，模拟氮沉降处理显著提高了土壤速效氮含量和苗木根系氮含量；土壤微生物碳（SMBC）含量比对照显著下降78%，而土壤微生物氮（SMBN）则提高2.6倍。模拟氮沉降处理显著降低土壤中微生物群落总含量。施氮肥对马尾松土壤N₂O和CO₂的释放速率均有显著影响，增施氮肥不仅显著提高了土壤N₂O的释放速率，而且CO₂释放速率短期内也显著提高，但伴随微生物群落的下降，施肥后期CO₂释放速率表现下降趋势。相关分析表明，土壤CO₂和N₂O释放与土壤pH值、土壤温度、土壤湿度、土壤速效氮含量及SMBC、SMBN相关；逐步回归分析表明，土壤硝态氮含量的变化是驱动土壤温室气体释放的主导因子。3株种植单位土壤体积内根系生物量较高，增加了土壤水分的消耗速率和氮的吸收固定，因而减少N₂O的释放速率。以上研究阐明了氮沉降或过量施肥对土壤氮含量、土壤pH值、根系生物量及氮含量、土壤微生物群落结构等因子的影响，这些因子直接或间接影响土壤温室气体释放速率。氮沉降及施用氮肥是加快土壤温室气体（CO₂和N₂O）排放进程的重要因素。



Abstract:To understand the driving mechanism of nitrogen deposition on greenhouse gases-emission from forest soil, we studied soil physical and chemical properties, microbial community structure and greenhouse gas-emission of potted soil of two-years old Pinus massoniana, fertilized with nitrogen. The results showed that simulated nitrogen deposition treatment significantly increased soil available nitrogen and seedling root nitrogen level. Soil microbial carbon (SMBC) decreased by 78% compared with that of the control. In contrast, soil microbial nitrogen (SMBN) increased by 2.6 times from that of control. Simulated nitrogen deposition treatment significantly reduced the level of soil total microbials. Nitrogen application had a significant effect on the soil emission rates of N₂O and CO₂:the N₂O emission rate increased with higher level of nitrogen application, the CO₂ emission rate also increased in the short term but decreased at the later stage due to the significant decrease of soil microbials. Correlation analysis showed that soil pH, temperature, moisture, available nitrogen, SMBN and SMBC were all ralated to CO₂ and N₂O emission rates. Step-wise regression analysis showed that the amount of nitrate N was the dominant factor affecting soil CO₂ and N₂O flux. Larger amount of root in the soil from the three-plant pots was beneficial to absorb and reduce the excessive nitrogen in soil and decrease N₂O emission. In conclusion, our study illustrated the effects of nitrogen deposition or excessive N fertilization on soil nitrogen content, soil pH, root biomass and soil microbial community structure and other variables, which directly or indirectly affect the emission rate of soil greenhouse gas. Soil nitrate accumlation caused by N deposition or N fertilization or N fertilization is conductive to accelerating soil greenhouse gases (CO₂ and N₂O) emission.





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