氨氧化是氮的生物地球化学循环的关键步骤,土壤是全球氮通量的重要生态系统。世界上大约25%的土壤是碱性的。虽然硝化作用在农业碱性土壤中得到了更广泛的研究,人们对自然的了解较少,未施肥的碱性土壤。在这项研究中,负责氨氧化的微生物和几个环境因素(季节,温度,氨浓度,和水分含量)在pH值为8.36至8.77的碱性森林土壤中进行了研究。氨氧化细菌(AOB),氨氧化古细菌,和Comammox存在,属于亚硝基螺旋体属和亚硝基螺旋体属的AOB,最初占总细菌群落的<0.01%,对土壤中添加的氨反应迅速。不同季节间的硝化速率没有显著差异,但是原位田间硝化速率与实验室微观世界中的硝化速率之间存在显着差异。令人惊讶的是,硝化发生在许多测试条件下,但是任何可识别的氨氧化剂组的丰度都没有可检测到的增加。这项研究提出了有关低丰度微生物在微生物过程中的作用以及零或非常低的微生物生长与代谢活动重合的情况的问题。此外,这项研究提供了对未施肥碱性土壤硝化的见解,并支持先前的研究,发现AOB在补充氨的碱性土壤中起着重要作用,包括农业生态系统。
Ammonia oxidation is a key step in the biogeochemical cycling of nitrogen, and soils are important ecosystems for nitrogen flux globally. Approximately 25% of the world\'s soils are alkaline. While
nitrification has been studied more extensively in agricultural alkaline soils, less is known about natural, unfertilized alkaline soils. In this study, microorganisms responsible for ammonia oxidation and several environmental factors (season, temperature, ammonia concentration, and moisture content) known to affect nitrification were studied in an alkaline forest soil with a pH ranging from 8.36 to 8.77. Ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea, and comammox were present, and AOB belonging to genera Nitrosospira and Nitrosomonas, originally comprising <0.01% of the total bacterial community, responded rapidly to ammonia addition to the soil. No significant difference was observed in
nitrification rates between seasons, but there was a significant difference between in situ field
nitrification rates and rates in laboratory microcosms. Surprisingly,
nitrification took place under many of the tested conditions, but there was no detectable increase in the abundance of any recognizable group of ammonia oxidizers. This study raises questions about the role of low-abundance microorganisms in microbial processes and of situations where zero or very low microbial growth coincides with metabolic activity. In addition, this study provides insights into
nitrification in unfertilized alkaline soil and supports previous studies, which found that AOB play an important role in alkaline soils supplemented with ammonia, including agricultural ecosystems.