氮素水平对潮土氨氧化微生物和硝化作用的影响

为了明确不同氮素水平对土壤硝化作用和氨氧化微生物的影响，特别是高氮水平下氨氧化细菌(AOB)和氨氧化古菌(AOA)的响应特异性，以潮土为供试土壤，以尿素和硫酸铵作为氮源，设置5个氮素水平(以N计，分别为0、150、300、600、1 200 mg·kg^-1,相应地，记为N0、N150、N300、N600、N1200),进行28 d的微宇宙培养，研究不同氮素水平下尿素和硫酸铵对土壤AOB、AOA丰度和土壤硝化作用的影响。结果表明，添加氮肥显著(P<0.05)降低了土壤pH值，至培养结束时(28 d),土壤pH值随氮素水平增加而降低。培养结束时，各加氮处理的土壤NH⁺₄-N含量都处于较低水平(0.72～2.01 mg·kg^-1)。与N0处理相比，添加尿素或硫酸铵增加了AOB amoA基因拷贝数，且AOB amoA基因拷贝数随氮素水平增加而增加；但施用氮肥对AOA amoA基因拷贝数无显著影响。土壤平均净硝化速率随氮素水平的增加而增加，且同一氮素水平下，尿素处理的土壤平均净硝化速率高于硫酸铵处理。相...

Effects of nitrogen levels on ammonia oxidizers and nitrification in fluvo-aquic soil

To clarify the effects of nitrogen (N) levels on soil nitrification and ammonia oxidizers, especially the response of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) to high N levels, a 28-day microcosm incubation test was conducted to investigate the effect of urea and ammonium sulfate on the abundance of AOB, AOA and soil nitrification in fluvo-aquic soil. Soils were added with N levels of 0, 150, 300, 600, 1 200 mg kg^-1, which were termed as N0, N150, N300, N600 and N1200, respectively. The results showed that soil pH was significantly (P<0.05) decreased with N addition as compared with N0 treatment, and soil pH decreased with the increasing N levels at the end of incubation (28 d). Soil $NH_{4}^{+}$-N concentrations reached a relatively low level at the end of incubation with N addition, which was ranged from 0.72 to 2.01 mg kg^-1. Compared to the N0 treatment, addition of urea or ammonium sulfate increased the AOB amoA gene copies, which increased with the increasing N levels. Meanwhile, AOA amoA gene copies did not respond to N additions. The average net nitrification rate increased with the increasing N levels, and it was higher with urea addition than that with ammonium sulfate addition under the same N level. Pearson correlation analysis demonstrated that soil $NO_{2}^{-}$-N+$NO_{3}^{-}$-N concentration was significantly (P<0.05) positively correlated with AOB amoA gene copies other than AOA amoA gene copies, indicating that AOB dominated the soil nitrification in fluvo-aquic soil. Overall, high-level N additions did not inhibit but stimulate the nitrification of fluvo-aquic soil, and the nitrification was dominated by AOB. The results could provide theoretical support for N fertilizer management in fluvo-aquic soil.