摘要:为探究森林土壤微生物呼吸对温度的敏感性及其影响因素，在太白山选取典型的4个不同海拔的林带（锐齿栎林、辽东栎林、红桦林、牛皮桦林）的0-10 cm表层土壤为对象，分别在15、25、35℃下进行控温培养实验并测量其土壤呼吸速率、微生物量和胞外酶活性等指标。结果表明：1）在1-20 d与20-72 d时的微生物呼吸速率分别呈现波动下降趋势与缓慢下降趋势，相比于其初始速率平均下降了68%与90%；表明高温在短期内促进土壤呼吸；2）太白山地区土壤温度敏感系数（Q₁₀）随温度的升高而降低；3）在培养过程中，出现15℃和25℃下微生物量先增多后减少，35℃下微生物量一直减少的现象，并且胞外酶是影响土壤微生物呼吸的重要因素，其中BG（β-葡萄糖苷酶）是胞外酶中最重要的影响因子；4）培养72 d以后，BG已无法为微生物生长繁殖提供充足的碳，在25℃和35℃下，由BX（β-木糖苷酶）提供的碳已成为微生物生长繁殖的重要碳源之一。在15℃和25℃下，N是培养前期限制土壤呼吸的因素，C是后期限制因素；在35℃下，N一直是限制土壤呼吸的因素。在15℃和35℃下，土壤呼吸不存在P限制；在25℃的培养前期，P是限制土壤呼吸的因子，而在培养后期不存在P限制。本研究结果阐明抑制土壤碳排放的关键在于抑制土壤微生物呼吸，揭示了在胞外酶驱动下的土壤碳循环特征，为准确预测全球未来气候变化的趋势提供理论基础。



Abstract:Soil microbial respiration is a major source of CO₂ efflux to the atmosphere from forest ecosystems and plays a decisive role in predicting future global climate change. A typical temperate forest ecosystem, the Taibai Mountain contains a mosaic of stands with various attitudes. The objective of the present study was to investigate the trends and influencing factors of microbial respiration in temperate forest soils without external carbon input. In the Taibai Mountain, 0-10 cm topsoil of typical forest belts of different altitudes (Quercus aliena var. acuteserrata, Q. liaotungensis, Betula albosinensis, and B. albosinensis var. septentrionalis) were sampled and incubated at 15 ℃, 25 ℃, and 35 ℃. The microbial respiration rate showed a fluctuating downward trend and a slowly decreasing trend at Days 1-20 and Days 20-72, with a 68% and 90% decrease compared to the initial rate, respectively. Thus, high temperature promoted soil respiration in the short term whereas it retarded soil respiration in the long term. The temperature sensitivity index (Q₁₀) of the soil in the Taibai Mountain decreased with warming. Microbial biomass increased initially and then decreased during the incubation at 15 ℃ and 25 ℃, whereas it decreased throughout the incubation at 35 ℃. Furthermore, BG (β-1,4-glucosidase) was the most important extracellular enzyme affecting microbial respiration. After 72 days of incubation, BG failed to provide adequate carbon for microbial growth and reproduction. At 25 ℃ and 35 ℃, the carbon provided by BX (β-1,4-xylosidase) became one of the most important carbon sources for microbial growth and reproduction. At 15 ℃ and 25 ℃, N was the limiting factor for soil respiration during the early incubation stage and C was the limiting factor for the later stage; at 35 ℃, N was the limiting factor of soil respiration throughout the incubation. At 15 ℃ and 35 ℃, there was no P limitation for soil respiration; however, P was a limiting factor for soil respiration during the early incubation stage at 25 ℃. The results of this study demonstrated that the key to limiting soil carbon emissions is to retard soil microbial respiration, with extracellular enzymes significantly influencing soil microbial respiration.





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