放牧对黄土高原典型草原冬季牧场甲烷氧化菌类群及活性的影响

Grazing Effect on Activity and Diversity of Soil Methanotrophs in Winter Pastures of the Loess Plateau

土壤甲烷氧化菌是大气甲烷(CH_(4))氧化的唯一生物汇。放牧能通过影响甲烷氧化菌的丰度和多样性来调控草地土壤的甲烷氧化活性。采集黄土高原典型草地冬季牧场中不同强度连续放牧的土壤样本,通过室内培养和高通量测序的方法测定不同放牧强度下土壤甲烷氧化活性以及土壤甲烷氧化菌的组成和丰度变化规律。结果表明,该草地是CH4汇,中放牧强度(MG)和高放牧强度(HG)增加了甲烷氧化速率。同时,与未放牧(CK)相比,MG和HG的甲烷氧化菌的平均丰度也显著增加。高通量测序结果显示,放牧对甲烷氧化菌的多样性有显著影响,不同放牧强度下均以USCγ为优势类群,同时存在少量的甲基暖菌属(Methylocaldum)和甲基孢囊菌属(Methylocystis)。皮尔森(Pearson)相关性分析表明,甲烷氧化速率(MOR)与土壤的水分含量和硝态氮的含量存在显著正相关(P<0.05),与USCγ的绝对数量存在极显著的正相关关系(P<0.01),这说明USCγ在该草地甲烷吸收过程中起主要作用。本研究证明了放牧可提升黄土高原典型草地的甲烷汇功能。

【Objective】Soil methanotrophs are the only biological sink of atmospheric methane(CH4).Grazing can regulate the methane oxidation activity of the soil by affecting the abundance and diversity of soil methanotrophs.【Method】In this study,we collected soil samples in winter pasture from different intensities of continuous grazing on typical grasslands in the Loess Plateau and used laboratory incubation and high-throughput sequencing to determine methane oxidation activity,composition and abundance of soil methanotrophs.【Result】The results showed that the grassland was CH4 sink,and the medium grazing(MG)and high grazing(HG)intensity increased the rate of methane oxidation.Meanwhile,the mean abundance of methanotrophs in HG and MG also increased significantly compared with CK.The results of high-throughput sequencing showed that grazing had a significant impact on the diversity of methanotrophs,Upland soil cluster gamma(USCγ)was the dominant methanotrophic group under different grazing intensities,and a small amount of Methylocaldum and Methylocystis were also present.Pearson correlation analysis showed that methane oxidation rate(MOR)showed a significant positive correlation with soil moisture content and 3 NO--N content(P<0.05),and significantly positively correlated with the absolute amount of USCγ(P<0.01),which indicated that USCγplayed a major role in the process of methane uptake in this grassland.【Conclusion】This study proved that grazing can improve the methane sink function of typical grasslands in the Loess Plateau.