冬季增温和减雪对黄土高原典型草原土壤养分和细菌群落组成的影响

冬季增温和积雪变化可改变土壤-微生物系统结构和功能。微生物作为陆地生态系统关键生物因子, 发挥着调控土壤养分循环的重要作用, 并对环境扰动, 特别是冬季气候变化十分敏感。开展半干旱区典型草原土壤养分和微生物特性对冬季气候变化的响应研究, 对预测未来气候变化情景下草地生态过程和功能变化意义重大。该研究以宁夏云雾山国家级自然保护区半干旱草原为研究对象, 于冬季布设增温、减雪、增温减雪互作及对照4种处理, 探究了黄土高原典型草原0-5 cm土层土壤养分、酶活性、土壤细菌群落组成对冬季温度和积雪变化的响应规律。结果表明: (1)冬季增温、减雪及互作均提高了0-5 cm土壤温度, 降低了土壤相对湿度, 但却显著增加了土壤冻融循环次数; (2)与对照相比, 不同处理整体上降低了微生物生物量及其多样性, 降低了土壤β-1,4-葡萄糖苷酶(BG)、β-1,4-N-乙酰基氨基葡萄糖苷酶(NAG)、碱性磷酸酶(AKP)活性, 增加了土壤有机碳、全氮、速效磷及铵态氮含量, 硝态氮含量有所下降; (3)研究区土壤细菌以酸杆菌门、变形菌门、放线菌门、芽单胞菌门为主, 优势菌纲以酸杆菌纲、γ-变形杆菌纲、嗜热油菌纲及σ-变形菌纲为主。冗余分析显示, 速效磷含量对细菌群落构成影响最显著, 对群落变异的解释度为21.3%。总之, 冬季气候变化可通过影响土壤温湿度, 特别是冻融循环进而作用于土壤养分循环、酶活性和土壤细菌多样性变化, 这些结果对丰富和拓展气候变化对草地生态系统影响过程与机制的认识, 准确预测典型草原中长期动态变化具有重要意义。

Influences of warming and snow reduction in winter on soil nutrients and bacterial communities composition in a typical grassland of the Loess Plateau

Aims Variations in temperature and snow accumulations in winter will change the structure and function of the soil-microbial system. As a key biological factor in the terrestrial ecosystem, microorganisms play an important role in regulating soil nutrient cycles. However, they are very sensitive to environmental disturbances, especially to winter climate changes. It is in great need to study the response of soil nutrients and microbial properties of typical semi-arid grasslands to climate change in winter, in order to predict the ecological process and functional changes of grassland ecosystem in the long term. Methods In the present study, the semi-arid grassland in the Yunwushan National Nature Reserve in Ningxia Province was taken as the research object. The four treatments including warming (W), snow reduction (S), interaction of warming and snow reduction (WS), and control (CK) were set to explore the responses of soil nutrients, enzyme activities and soil bacterial communities in the 0-5 cm soil layer of the typical grassland of the Loess Plateau to variations in winter temperature and snow cover. Important findings Our results indicated that: (1) Warming, snow reduction and their interaction in winter increased the 0-5 cm soil temperature, lowered the relative humidity of the soil, but significantly increased the number of soil freeze-thaw cycles. (2) Compared with the control, other different treatments generally reduced the microbial biomass and bacterial diversity, which led to reduced activity of soil β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG) and alkaline phosphatase (AKP). The content of soil organic carbon, total nitrogen, available phosphorus, and nitrate nitrogen in the soil increased, while the content of nitrate nitrogen decreased. (3) The soil bacterial species in the study area were mainly Acidobacteria, Proteobacteria, Actinobacteria and Gemmatimonadetes. The dominant bacteria at the class level included Acidobacteria, γ-Proteobacteria, Thermophiles and σ-Proteobacteria. Redundancy analysis (RDA) results showed that available phosphorus (AP) content had the most significant impact on the bacterial community composition, with an explanation rate of 21.3% for the community variation. In conclusion, winter climate change can significantly affect soil temperature and humidity, especially the freezing and thawing cycles, which might further influence soil nutrients cycles, enzyme activities, and soil bacterial diversity. These results are of great significance for enriching and expanding the understanding of the process and mechanism of climate change on grassland ecosystem, as well as predicting the mid and long-term dynamic changes of typical grassland ecosystems.