摘要:温度在多种生物地球化学过程中起到关键的调节作用，是影响土壤硝化作用和微生物分布的重要因素之一。硝化过程的第1个步骤由氨氧化细菌（AOB）和氨氧化古菌（AOA）催化，然而，不同施氮量下，增温对硝化菌活性和丰度的影响尚不清楚。本研究基于2008年10月起设立于太行山山前平原的长期增温试验平台（高于地表 2 m的红外加热器使土壤温度升高1.5℃），于2018年5月对不施氮（N0）和施氮[N1，240 kg（N）·hm-2·a-1]下增温分别对0~10 cm和10~20 cm土壤硝化潜势（PNR）、AOA和AOB丰度的影响进行了研究。硝态氮（NO3--N和铵态氮（NH4+-N）含量用分光光度法测量，应用缓冲液培养法测定土壤PNR，提取土壤DNA后用实时荧光定量PCR技术测定功能基因AOA和AOB的丰度。结果表明：温度升高显著增加N1条件下PNR和NO3--N含量（P < 0.05），降低了N0条件下PNR和NO3--N含量，但差异不显著。N1条件下，增温土壤AOB丰度显著提高（P < 0.05）；N0条件下，增温土壤AOA丰度显著降低（P < 0.05）。与N0相比，N1条件下的AOA/AOB比值明显降低，表明增温加氮肥处理对AOB的生长刺激更强烈。在增温加施氮条件下，细菌（AOB）表现显著的正反应，在增温不施氮条件下，古菌（AOA）和AOB表现显著的负反应。本研究结果可为全球增温背景下进一步了解硝化活性和氨氧化微生物对增温和氮有效性的响应提供科学依据。
关键词:气候变暖/
硝化菌活性/
氨氧化微生物/
氮有效性
Abstract:The first step of nitrification (i.e., the oxidation of ammonia to nitrate) is catalyzed by nitrifiers, such as ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). However, the impact of soil warming on the activity and abundance of nitrifiers under different nitrogen (N) fertilization conditions remains poorly understood. A long-term field warming experiment has been conducted since October 2008 at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences in the North China Plain, during which soil temperature was increased by 1.5℃ using infrared heaters (power, 1 000 W) placed 2 m above the soil surface. In 2018, we investigated soils from the control (no warming) and warming treatment plots for potential nitrification rate (PNR), abundance of AOB and AOA at 10 cm and 20 cm soil depth under two N fertilization conditions:without N fertilization (N0) and with 240 kg(N)·hm-2·a-1 fertilization (N1). Soil PNR, nitrate (NO3--N), and ammonium (NH4+-N) contents were spectrophotometrically assessed, and the abundance of functional genes was investigated via real-time quantitative PCR. Warming increased PNR and NO3--N content under N1 treatment and decreased them under N0 treatment (P < 0.05). Moreover, warming significantly increased AOB abundance under N1 treatment (P < 0.05), whereas it decreased the abundance of both AOA and AOB under N0 treatment, at both soil depths. Compared with N0, N1 exhibited substantial decrease in AOA/AOB ratio, suggesting that compared with warming without N fertilization, warming with N fertilization exhibited higher stimulation of AOB growth than of AOA growth. Conclusively, this study suggests that AOB significantly and positively responded to warming with N fertilization, whereas both AOA and AOB significantly and negatively responded to warming without N fertilization. This study provides an understanding of nitrifier activity and the response of ammonia-oxidizing microorganisms to warming conditions and N availability.
Key words:Climate warming/
Nitrifier activity/
Ammonia-oxidizing microorganism/
N availability
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