Abstract:
Grazing exclusion (GE) is an effective measure for restoring degraded grassland ecosystems. However, the effect of GE on methane (CH4) uptake and production remains unclear in dominant bacterial taxa, main metabolic pathways, and drivers of these pathways. This study aimed to determine CH4 flux in alpine meadow soil using the chamber method. The in situ composition of soil aerobic CH4-oxidizing bacteria (MOB) and CH4-producing archaea (MPA) as well as the relative abundance of their functional genes were analyzed in grazed and nongrazed (6 years) alpine meadows using metagenomic methods. The results revealed that CH4 fluxes in grazed and nongrazed plots were -34.10 and -22.82 μg‧m-2‧h-1, respectively. Overall, 23 and 10 species of Types I and II MOB were identified, respectively. Type II MOB comprised the dominant bacteria involved in CH4 uptake, with Methylocystis constituting the dominant taxa. With regard to MPA, 12 species were identified in grazed meadows and 3 in nongrazed meadows, with Methanobrevibacter constituting the dominant taxa. GE decreased the diversity of MPA but increased the relative abundance of dominated species Methanobrevibacter millerae from 1.47 to 4.69%. The proportions of type I MOB, type II MOB, and MPA that were considerably affected by vegetation and soil factors were 68.42, 21.05, and 10.53%, respectively. Furthermore, the structural equation models revealed that soil factors (available phosphorus, bulk density, and moisture) significantly affected CH4 flux more than vegetation factors (grass species number, grass aboveground biomass, grass root biomass, and litter biomass). CH4 flux was mainly regulated by serine and acetate pathways. The serine pathway was driven by soil factors (0.84, p < 0.001), whereas the acetate pathway was mainly driven by vegetation (-0.39, p < 0.05) and soil factors (0.25, p < 0.05). In conclusion, our findings revealed that alpine meadow soil is a CH4 sink. However, GE reduces the CH4 sink potential by altering vegetation structure and soil properties, especially soil physical properties.
摘要:
放牧是恢复退化草地生态系统的有效措施。然而,在优势细菌类群中,GE对甲烷(CH4)吸收和产生的影响尚不清楚,主要代谢途径,以及这些途径的驱动因素。本研究旨在使用室内法测定高寒草甸土壤中的CH4通量。使用宏基因组方法分析了放牧和非放牧(6年)高山草甸中土壤需氧CH4氧化细菌(MOB)和产生CH4的古细菌(MPA)的原位组成及其功能基因的相对丰度。结果表明,放牧区和非放牧区的CH4通量分别为-34.10和-22.82μg‧m-2‧h-1。总的来说,确定了23种和10种I型和II型MOB,分别。II型MOB包含参与CH4摄取的优势细菌,以甲基囊菌为主要类群。关于MPA,在放牧的草甸中鉴定出12种,在非放牧的草甸中鉴定出3种,甲烷杆菌构成主要类群。GE降低了MPA的多样性,但将占优势的甲烷杆菌的相对丰度从1.47%增加到4.69%。I型MOB的比例,II型MOB,受植被和土壤因素影响较大的MPA分别为68.42、21.05和10.53%,分别。此外,结构方程模型揭示了土壤因子(有效磷,堆积密度,和水分)显著影响CH4通量超过植被因素(草种数,草地上生物量,草根生物量,和凋落物生物量)。CH4通量主要受丝氨酸和乙酸途径调节。丝氨酸途径受土壤因素驱动(0.84,p<0.001),而乙酸盐途径主要由植被(-0.39,p<0.05)和土壤因素(0.25,p<0.05)驱动。总之,我们的发现表明,高寒草甸土壤是CH4汇。然而,GE通过改变植被结构和土壤特性来降低CH4汇潜力,特别是土壤物理性质。