小兴安岭酸性泥炭土硝化作用的类型及其驱动因子

以小兴安岭酸性森林泥炭土为研究对象,通过加入10 mL·L^-1乙炔及不同浓度的外源硫酸铵(0、1.2、6.0 mmol N·kg^-1)进行硝化培养试验,探究酸性泥炭土中硝化作用类型及主要驱动因子.结果表明:无论有无外加氮源,酸性泥炭土均存在较强的矿化作用(0.9～1.4 mg N·kg^-1·d^-1),经过2周的培养均发生了硝化作用(0.4～0.6 mg N·kg^-1·d^-1),且不同浓度硫酸铵处理之间无显著差异;而乙炔处理虽有较强的矿化作用(0.8 mg N·kg^-1·d^-1),但未发生明显的硝化作用(0 mg N·kg^-1·d^-1),说明该酸性泥炭土以自养硝化为主,外源无机氮源浓度对硝化作用无显著影响,硝化底物NH₃的主要来源不是外源硫酸铵,更可能来源于土壤中有机氮的矿化.培养0～14 d,无论有无外加氮源,酸性泥炭土氨氧化细菌(AOB)和古菌(AOA)丰度均显著增加,但不同浓度硫酸铵处理间无显著差异,表明外源无机氮浓度对氨氧化微生物的生长无显著促进作用.与不加乙炔的对照相比,乙炔处理AOB和AOA丰度随时间均无显著变化,推测AOA与AOB在该酸性泥炭土的硝化过程中都可能起一定的作用.

Type and key drivers of nitrification for an acidic peat soil in Xiaoxing’an Mountain,China

Acidic forest peat soil in Xiaoxing’an Mountain was used to investigate the type and key drivers of nitrification by carrying out nitrification incubation after adding 10 mL·L^-1 C₂H₂ and different amounts of (NH₄)₂SO₄(0, 1.2, 6.0 mmol N·kg^-1). Results showed that strong mineralization (0.9-1.4 mg N·kg^-1·d^-1) and nitrification (0.4-0.6 mg N·kg^-1·d^-1) after 2 weeks of incubation were observed for both nitrogen and no nitrogen treatments, and no significant difference was observed for different (NH₄)₂SO₄ application treatments. For C₂H₂ treatment, there was relatively stronger mineralization (0.8 mg N·kg^-1·d^-1), but no obvious nitrification (0 mg N·kg^-1·d^-1). These results indicated that the nitrification in acidic peat soil was mainly autotrophic, and inorganic nitrogen application did not affect nitrification rate significantly. Results also implied that the substrate (NH₃) for nitrification was from the organic N mineralization, rather than the (NH₄)₂SO₄ application. Both ammonia-oxidizing bacteria (AOB) and archaea (AOA) abundances increased significantly during 0-14 d regardless of nitrogen application. However, no significant difference in AOB and AOA abundances for different (NH₄)₂SO₄ application treatments was observed, indicating that ammonia oxidizers did not respond positively to (NH₄)₂SO₄ application. Compared with the treatments without C₂H₂, AOB and AOA abundances did not change significantly during the incubation in C₂H₂ treatment, suggesting that both AOA and AOB were likely the key players in nitrification in the acidic peat soil.