古尔班通古特沙漠生物土壤结皮对氨氧化微生物生态位的影响

生物结皮作为荒漠地表的重要覆被类型, 在荒漠生态系统的氮素循环中扮演重要角色。融雪期为古尔班通古特沙漠生物结皮的复苏和生长提供了充足的水分, 也成为该沙漠氮素固定和转化的重要时期, 但该时期生物结皮如何影响驱动氨氧化转化的微生物群落动态尚未明确。因此, 我们利用荧光定量PCR (fluorescent quantitative PCR, qPCR)方法分析融雪期生物结皮与去除结皮不同土层(0-2, 2-5, 5-10和10-20 cm)氨氧化菌群丰度特征, 结合潜在硝化速率和土壤理化参数, 探究融雪期生物结皮对荒漠土壤氮素转化作用。结果表明: 氨氧化古菌(ammonia-oxidizing archaea, AOA)是古尔班通古特沙漠土壤优势氨氧化菌, 生物结皮对0-2 cm层土壤中AOA、氨氧化细菌(ammonia-oxidizing bacteria, AOB) amoA基因丰度具有显著抑制作用(P < 0.01), 对10-20 cm层土壤中AOA amoA基因丰度具有显著促进作用(P < 0.01)。冗余分析(redundancy analysis, RDA)表明, AOA、AOB amoA基因丰度主要受土壤含水量和铵态氮含量的影响, 占总条件效应的54.90%。氨氧化速率分析发现, 去除生物结皮显著降低古尔班通古特沙漠土壤硝化作用潜力(P < 0.001), 证实生物结皮对荒漠土壤氮素转化具有重要的调控作用。综上所述, 古尔班通古特沙漠氨氧化微生物的分布规律受环境因子调控, 特别是生物结皮可以通过调节土壤含水量和铵态氮含量影响AOA和AOB的空间生态位分化, 促进沙漠土壤的硝化作用。

Biocrusts impact niche separation of ammonia oxidizing microorganisms in the Gurbantunggut Desert,northwestern China

Aims: Biological soil crusts(Biocrusts) are complex assemblages of lichens, bryophytes, cyanobacteria, fungi, and heterotrophic microbial organisms in the top few centimetres of desert soils. Biocrusts perform important ecological roles in the nitrogen cycle of desert ecosystems. In desert ecosystems, water sources are vital, and the seasonal melting snow in early spring resurrects biocrusts in the Gurbantunggut desert and begins nitrogen fixation. However, little is known about how biocrusts impact nitrifier distributions across the landscape, specifically ammonia oxidation archaea(AOA) and ammonia oxidation bacteria(AOB). Methods: We used fluorescent quantative PCR(qPCR) methods to characterize AOA and AOB amoA gene abundances at different soil depths(0–2, 2–5, 5–10 and 10–20 cm) in biocrust and biocrust-removal soils. Desert nitrification potential and soil physicochemical parameters were researched to understand biocrust impacts on the desert soil nitrogen cycle. Results: The AOA amoA gene abundance was remarkably larger than that of AOB across all soil samples. ANOVA results showed that biocrusts significantly affected AOA and AOB amoA gene abundance(P < 0.01) while PNR results indicated that biocrust removal significantly reduced soil nitrification potential(P < 0.001), which confirmed that biocrusts play an important role in regulating nitrogen transformation in the Gurbantunggut desert. A redundancy analysis confirmed that soil moisture and NH4+-N were the key environmental factors affecting niche separation of AOA and AOB in desert soil. Conclusion: Biocrusts coupled with oil moisture and NH4+-N affected differential distribution of ammonia oxidizing microorganisms in the temperate desert in the early spring.