Mountain ecosystems, contributing substantially to the global carbon (C) and nitrogen (N) biogeochemical cycles, are heavily impacted by global changes. Although soil respiration and microbial activities have been extensively studied at different elevation, little is known on the relationships between environmental drivers, microbial functions, and greenhouse gas fluxes (GHGs; carbon dioxide [CO], methane [CH] and nitrous oxide [NO]) in soils of different elevation. Here, we measured how GHG fluxes were linked to soil properties, soil organic matter (SOM) quantity and composition (the proportion of humic-like vs. protein-like OM), microbial biomass, enzyme activities and functional gene abundances in natural soils spanning an elevational gradient of ∼2400 m in Switzerland. Soil CO fluxes did not significantly vary from low (lowland zone) to higher (montane and subalpine zones) elevation forests, but decreased significantly (P<0.001) from the treeline to the mountain summit. Multivariate analyses revealed that CO fluxes were controlled by C-acquiring enzymatic activities which were mainly controlled by air mean annual temperature (MAT) and SOM quantity and composition. CH fluxes were characterized by uptake of atmospheric CH, but no trend was observed along the elevation. NO fluxes were also dominated by uptake of atmospheric NO. The flux rates remained stable with increasing elevation below the treeline, but decreased significantly (P<0.001) from the treeline to the summit. NO fluxes were driven by specific nitrifying and denitrifying microbial genes (ammonia-oxidizing A and NO-producing B), which were again controlled by SOM quantity and composition. Our study indicates the treeline as a demarcation point changing the patterns of CO and NO fluxes along the elevation, highlighting the importance of SOM quantity and composition in controlling microbial enzyme activities and GHG fluxes.

中文翻译：

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土壤有机质特性沿着海拔梯度驱动微生物酶活性和温室气体通量


山区生态系统对全球碳 (C) 和氮 (N) 生物地球化学循环做出了重大贡献，受到全球变化的严重影响。尽管人们对不同海拔的土壤呼吸和微生物活动进行了广泛的研究，但人们对环境驱动因素、微生物功能和温室气体通量（GHG；二氧化碳 [CO]、甲烷 [CH] 和一氧化二氮 [NO]）之间的关系知之甚少。 ）在不同海拔的土壤中。在这里，我们测量了温室气体通量如何与天然土壤中的土壤特性、土壤有机质 (SOM) 数量和成分（类腐殖质与类蛋白质 OM 的比例）、微生物生物量、酶活性和功能基因丰度相关。瑞士的海拔梯度约为 2400 米。从低海拔森林（低地地区）到高海拔森林（山地和亚高山地区），土壤二氧化碳通量没有显着变化，但从林线到山顶显着下降（P<0.001）。多变量分析表明，CO 通量受 C 获取酶活性控制，而 C 获取酶活性主要受空气年平均温度 (MAT) 和 SOM 数量和组成控制。 CH 通量以大气 CH 的吸收为特征，但沿海拔方向没有观察到趋势。 NO 通量也主要由大气 NO 的吸收决定。随着树线以下海拔的增加，通量率保持稳定，但从树线到山顶显着下降（P<0.001）。 NO 通量由特定的硝化和反硝化微生物基因（氨氧化 A 和 NO 产生 B）驱动，这些基因又受到 SOM 数量和组成的控制。 我们的研究表明，林线作为分界点改变了沿海拔高度的 CO 和 NO 通量模式，强调了 SOM 数量和组成在控制微生物酶活性和温室气体通量方面的重要性。