温度和水分变化对冻土区泥炭地土壤氮循环功能基因丰度的影响

以大兴安岭多年冻土区泥炭地为研究对象，通过室内模拟增温实验，研究温度升高对不同深度（0-150 cm）土壤氮循环功能基因丰度的影响。同时针对0-20 cm和20-40 cm土壤设置两个水分处理，分别为土壤原始含水量和淹水状态，研究水分变化对表层土壤氮循环功能基因丰度的影响。结果表明温度升高显著提高了活动层（0-60 cm）、过渡层（60-80 cm）、永冻层（80-100 cm）中nifH、nirK基因丰度，温度升高显著提高了活动层（0-40 cm）和过渡层（60-80 cm）中nirS基因丰度。温度升高显著提高了过渡层（60-80 cm）NH₄⁺-N和较深永冻层（140-150 cm）NO₃^--N的含量，但降低了过渡层（60-80 cm）NO₃^--N和较深永冻层（120-150 cm）NH₄⁺-N的含量，相关性分析表明，NH₄⁺-N含量与nifH和nirS基因丰度呈显著正相关，NO₃^--N含量与nirK基因丰度呈显著正相关，说明温度升高能够通过改变微生物丰度促进过渡层固氮作用和反硝化作用。在增温条件下，淹水处理使表层土壤nirS和nirK基因丰度及NH₄⁺-N含量降低，但提高了NO₃^--N含量，说明淹水造成了过度还原的条件使反硝化底物浓度降低，降低反硝化微生物活性进而抑制了土壤反硝化作用。该结果对于明确未来气候变化影响下冻土区泥炭地土壤氮循环过程具有重要意义。

Effects of temperature and moisture changes on functional gene abundance of soil nitrogen cycle in permafrost peatland

We sampled peatland soil columns in the Great Hing''an Mountains and studied the effect of temperature increasing on nitrogen cycle related functional gene abundance at different depths(0-150 cm) by indoor simulation incubation. We set up two moisture treatments, including soil original moisture content and flooding condition at 0-20 cm and 20-40 cm, to study the effect of moisture on nitrogen cycle related functional gene abundance in 0-20 cm and 20-40 cm. Temperature increasing significantly increased the abundance of nifH, nirK gene in active layer(0-60 cm), transition layer(60-80 cm) and permafrost layer(80-100 cm). Temperature increasing significantly increased the abundance of nirS gene in active layer(0-40 cm), and transition layer(60-80 cm). Temperature increasing increased the content of soil NH₄⁺-N in transition layer(60-80 cm) and NO₃^--N in permafrost layer(140-150 cm), while reduced the content of NO₃^--N in transition layer(60-80 cm) and NH₄⁺-N in permafrost layer(120-150 cm). Correlation analysis showed that NH₄⁺-N had significantly positive correlation with nifH and nirS gene abundance, and NO₃^--N had significant positive correlation with nirK gene abundance. These results indicated that temperature increasing promoted the nitrogen fixation and denitrification processes in transition layer(60-80 cm) by changing microbial abundance. Under the flooding condition, the abundance of nirS and nirK and the content of NH₄⁺-N in surface soil were decreased, while the content of NO₃^--N in surface soil increased obviously. The concentration of denitrifying substrate was decreased by flooding, the denitrifying microbial activity was inhibited by flooding, and inhibited soil denitrification. The results are of great significance for clarifying the nitrogen cycle process under climate change in the future.