摘要:以腾格里沙漠东南缘的典型荒漠植被为研究对象，通过遮雨棚和滴灌系统设置5个降水梯度，即极端干旱处理、中度干旱处理、对照、增水处理I和增水处理II，研究了荒漠土壤微生物量碳（MBC）、氮（MBN）和微生物碳氮比（MBC/MBN）对季节、降水和土壤深度的响应规律，以期为极端降水事件影响干旱荒漠区土壤微生物量碳、氮及其循环规律的深入研究提供科学依据。结果表明：（1） MBC、MBN和MBC/MBN对降水处理的响应存在差异，三者的变化范围为：230.14-272.87 mg/kg，13.82-17.58 mg/kg，19.78-36.06。其中，降水处理对MBC、MBN的影响显著，对MBC/MBN的影响不显著，在极端干旱处理下，MBC、MBN均显著高于其他降水处理；（2）两年间的MBC、MBN和MBC/MBN差异显著，2017年较2016年MBC、MNB显著减少，MBC/MBN显著增加；（3） MBC、MBN和MBC/MBN变化均表现季节性差异，变化范围分别为：153.31-337.09 mg/kg，7.89-22.29 mg/kg，14.82-46.04，其中MBC、MBN为春季最高、秋季最低，MBC/MBN为夏季最低、冬季最高；（4） MBC、MBN和MBC/MBN在土壤0-20 cm的变化范围为：232.57-265.15 mg/kg，14.00-17.93 mg/kg，24.37-32.07，其中土壤表层（0-5 cm） MBC、MBN显著高于中层土壤（5-10 cm）和下层土壤（10-20 cm），而不同土壤深度的MBC/MBN差异不显著。因此，在极端降水事件频发的全球气候背景下，极端干旱将影响荒漠生态系统MBC、MBN水平，进而对碳、氮平衡和循环过程产生影响，对这一问题的确切回答尚需长期系统监测研究。



Abstract:The change of global precipitation pattern has a great impact on the arid ecosystem. As an indicator of change of soil quality, soil microbes could reflect the material circulation ability, soil fertility, and plant productivity of the ecosystem. Soil microbial biomass carbon (MBC) and nitrogen (MBN) were very sensitive to precipitation changes. The typical desert vegetation on the southeast edge of Tengger Desert was selected as research object in this study. We aimed to provide the scientific basis for further study of microbial carbon and nitrogen and their cycling mechanism in desert ecosystem in the context of global climate change with extreme precipitation events. By using rain shelter and drip systems, five precipitation manipulation treatments were set up, namely extreme drought treatment, moderate drought, contrast, precipitation increasing treatment I, and precipitation increasing treatment II. The response characteristics of desert soil MBC, MBN, and MBC:MBN ratio to different seasons, precipitation and soil depth were studied. The results showed that (1) precipitation manipulation treatments had diverse effects on MBC, MBN, and MBC/MBN ratio. The variation ranges of MBC, MBN, and MBC/MBN ratio were 230.14-272.87 mg/kg, 13.82-17.58 mg/kg, and 19.78-36.06, respectively. Precipitation manipulation treatments had significant effects on MBC and MBN, but not on MBC/MBN ratio. Under extreme drought treatment, the values of MBC and MBN were significantly higher than that of other precipitation treatments. (2) The two-year variation of MBC, MBN, and the ratio of MBC/MBN were significant. Compared with 2016, MBC and MBN significantly decreased and MBC/MBN ratio increased in 2017. (3) MBC, MBN and the ratio of MBC/MBN showed distinct seasonal changes. The range of MBC, MBN, and the ratio of MBC/MBN were 153.31-337.09 mg/kg, 7.89-22.29 mg/kg, and 14.82-46.04, respectively. The highest values of MBC and MBN were in spring, and the lowest values in autumn, while MBC/MBN ratio was the lowest in summer and the highest in winter. (3) The range of MBC, MBN and MBC/MBN ratio in the soil depth of 0-20 cm were 232.57-265.15 mg/kg, 14.00-17.93 mg/kg, and 24.37-32.07, respectively. The MBC and MBN were significant different (P<0.01) among different soil layers, while the values of MBC and MBN in 0-5cm layer were higher than that in both 5-10 cm and 10-20 cm depths. No significant differences of MBC/MBN ratio were found among different soil layers. Therefore, under the global climate background of frequent extreme precipitation events, extreme drought will affect the MBC and MBN in desert ecosystem. Further, it will affect the balance and cycling of carbon and nitrogen, which needs further long-term systematic monitoring.





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