Soil microbes respond to four-year warming and precipitation alteration

The alpine grasslands of the Tibetan Plateau store 23.2 Pg soil organic
carbon (SOC), which becomes susceptible to microbial degradation with
climate warming. However, accurate prediction of how the soil carbon (C)
stock changes under future climate warming is hampered by our limited
understanding of below-ground complex microbial communities. Here, we show
that 4 years of warming strongly stimulated methane (CH4) uptake by 93.8%
and aerobic respiration (CO2) by % in the soils of alpine grassland
ecosystem. Due to no significant effects of warming on net ecosystem CO2
exchange (NEE), the warming-stimulated CH4 uptake enlarged the carbon sink
capacity of whole ecosystem. Furthermore, precipitation alternation didn’t
alter such warming effects, despite the significant effects of
precipitation on NEE and soil CH4 fluxes were observed. Metagenomic
sequencing revealed that warming led to significant shifts in the overall
microbial community structure and the abundances of functional genes,
which contrasted to no detectable changes after 2 years of warming.
Carbohydrate utilization genes were significantly increased by warming,
corresponding with significant increases in soil aerobic respiration.
Increased methanotrophic genes and decreased methanogenic genes were
observed under warming, which significantly (R2 = 0.59, P < 0.001)
correlated with warming-enhanced CH4 uptakes. Furthermore, 212
metagenome-assembled genomes (MAGs) were recovered, including many
populations involved in the degradation of various organic matter and a
highly-abundant methylotrophic population of the Methyloceanibacter genus.
Collectively, our results provide compelling evidence that specific
microbial functional traits for CH4 and CO2 cycling processes respond to
climate warming with differential effects on soil greenhouse gas
emissions. Alpine grasslands may play huge roles in mitigating climate
warming through such microbially-enhanced CH4 uptake.