DOI: 10.5061/dryad.9s4mw6mks
title: Soil microbes respond to four-year warming and precipitation alteration

description: 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 &lt; 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.
description: Soil temperature and moisture were
 automatically monitored by 5-TM probe sensors at the soil depth of 5 cm
 with an EM-to data logger (Meter, Inc., Pullman, WA, USA) in each
 plot.  Soil aerobic respiration (soil CO<sub>2</sub>
 flux) was automatically measured once an hour by the LI-8150 Multiplexer
 composed of LI -8100-104 long-term chambers (Li-Cor Inc., Lincoln, NE,
 USA) and a LI-8100 Automated soil CO<sub>2</sub> flux system
 (Wang<em> et al.</em>,
 2014). As for soil CH<sub>4</sub> fluxes, gas
 samples were collected from all plots twice or three times per month
 between 9:00 a.m. and 12:00 p.m. on sunny days (Qi et al., 2021).
 Specifically, a stainless steel collar was inserted 10 cm into the soil in
 each plot and a static opaque chamber (40 cm in length
 ´ 40 cm in width ´ 40 cm in height) was used to collect gas samples from soil at this site (Yuan<em> et al.</em>, 2021). At each measurement, 60 mL gas sample was collected in each plot and analyzed within 24 hours using gas chromatography (Agilent 7890A; Agilent Technologies, Santa Clara, CA, USA) to present a one-day average flux. Similar with soil CH<sub>4</sub> fluxes, ecosystem C fluxes were also measured twice or three times per month between 9:00 a.m. and 12:00 p.m. on sunny days (Qi<em> et al.</em>, 2021). We used a LI-6400 infrared gas analyzer (LI-COR, Inc., Lincoln, NE, USA) with a transparent chamber (0.4 m in length × 0.4 m in width × 0.6 m in height) to measure net ecosystem CO<sub>2</sub> exchange (NEE). Ecosystem respiration (ER) was measured by using the similar method with the transparent chamber covered by an opaque cloth. Gross ecosystem production (GEP) was estimated as the difference between NEE and ER (Qi<em> et al.</em>, 2021). In this study, the more negative NEE represents more CO<sub>2</sub> sequestration by terrestrial ecosystem.