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Journal of Arid Land >

2024 , Vol. 16 >Issue 6: 768 - 778

DOI: https://doi.org/10.1007/s40333-024-0017-z

Research article

Extreme drought with seasonal timing consistently promotes CH4 uptake through inconsistent pathways in a temperate grassland, China

  • ZHANG Wenwen 1, 2 ,
  • PAN Yue 1 ,
  • WEN Fuqi 3 ,
  • FU Juanjuan 1 ,
  • HAO Yanbin 3 ,
  • HU Tianming 1 ,
  • YANG Peizhi , 1, *
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  • 1College of Grassland Agriculture, Northwest A&F University, Yangling 712100, China
  • 2Binzhou Institute of Technology, Weiqiao-UCAS (University of Chinese Academy of Sciences) Science and Technology Park, Binzhou 256606, China
  • 3College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
*YANG Peizhi (E-mail: )

Received date: 2024-03-05

  Revised date: 2024-04-23

  Accepted date: 2024-05-15

  Online published: 2025-08-13

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Abstract

Methane (CH4) is a potent greenhouse gas that has a substantial impact on global warming due to its substantial influence on the greenhouse effect. Increasing extreme precipitation events, such as drought, attributable to global warming that caused by greenhouse gases, exert a profound impact on the intricate biological processes associated with CH4 uptake. Notably, the timing of extreme drought occurrence emerges as a pivotal factor influencing CH4 uptake, even when the degree of drought remains constant. However, it is still unclear how the growing season regulates the response of CH4 uptake to extreme drought. In an effort to bridge this knowledge gap, we conducted a field manipulative experiment to evaluate the impact of extreme drought on CH4 uptake during early, middle, and late growing stages in a temperate steppe of Inner Mongolia Autonomous Region, China. The result showed that all extreme drought consistently exerted positive effects on CH4 uptake regardless of seasonal timing. However, the magnitude of this effect varied depending on the timing of season, as evidenced by a stronger effect in early growing stage than in middle and late growing stages. Besides, the pathways of CH4 uptake were different from seasonal timing. Extreme drought affected soil physical-chemical properties and aboveground biomass (AGB), consequently leading to changes in CH4 uptake. The structural equation model showed that drought both in the early and middle growing stages enhanced CH4 uptake due to reduced soil water content (SWC), leading to a decrease in NO3--N and an increase in pmoA abundance. However, drought in late growing stage primarily enhanced CH4 uptake only by decreasing SWC. Our results suggested that seasonal timing significantly contributed to regulate the impacts of extreme drought pathways and magnitudes on CH4 uptake. The findings can provide substantial implications for understanding how extreme droughts affect CH4 uptake and improve the prediction of potential ecological consequence under future climate change.

Key words： extreme climate; greenhouse gas; methane; methanotrophs; soil inorganic nitrogen

Cite this article

ZHANG Wenwen , PAN Yue , WEN Fuqi , FU Juanjuan , HAO Yanbin , HU Tianming , YANG Peizhi . Extreme drought with seasonal timing consistently promotes CH4 uptake through inconsistent pathways in a temperate grassland, China[J]. Journal of Arid Land, 2024 , 16(6) : 768 -778 . DOI: 10.1007/s40333-024-0017-z

1 Introduction

Global warming, caused by greenhouse gases, has significantly changed global precipitation pattern (IPCC, 2021; Zhou et al., 2022), and as a result, drought or seasonal drought has become one of the hot topics within the realm of global climate change (Mao et al., 2024; Xu et al., 2024). Methane (CH4), being a major contributor to the greenhouse effect, has a global warming potential that is 28-36 times more potent than carbon dioxide (CO2) over a span of a hundred years (Tian et al., 2014; Zhang et al., 2018; Zheng et al., 2020). Currently, the average concentration of CH4 in the atmosphere has reached 1.86 mg/kg, which increases 259.0% of the pre-industrial level, making a large contribution to global warming and climate change (i.e., drought) (Heimann, 2011; IPCC, 2021). The balance between global sources and sinks of CH4 has already been disrupted (Dlugokencky et al., 2011). Well-aerated soils, as the second-largest CH4 sink, consume approximately 26-42 Tg CH4/a (Dutaur and Verchot, 2007; Kirschke et al., 2013), contributing significantly to the global CH4 balance. Given the high susceptibility of soil CH4 uptake to drought, it is critical to study the impacts of drought on CH4 uptake.
To date, numerous studies have investigated how soil CH4 uptake responds to variations in precipitation, and the results indicate that a reduction in precipitation stimulates soil CH4 uptake (Billings et al., 2000; Borken et al., 2000; Davidson et al., 2008; Brechet et al., 2019; Chamberlain et al., 2020). However, several studies have also indicated that drought can significantly affect the processes of carbon and nitrogen (N) cycling within ecosystems on land (Knapp et al., 2002; Knapp et al., 2014), thereby causing a reduction in CH4 uptake (Blankinship et al., 2010; Yue et al., 2021), and providing further feedback on climate change (Easterling et al., 2000; IPCC, 2013). The process of CH4 oxidation in soil is mediated by methanotrophs, with methane monooxygenase (MMO) constituting the most substantial biological reservoir. The subunit genes of MMO, especially the pmoA found in most methanotrophs, are currently considered the most commonly used biomarkers for studying methanotrophs (Kolb, 2003; Tentori et al., 2020). The methanotroph activity is more susceptible to dry conditions than to wet ones (Shukla et al., 2013). Hence, comprehending the influence of drought changes on CH4 uptake in arid areas and associated microbial mechanisms holds significant implications for predicting future carbon cycling and its feedback effects on climate change.
Previous research had mostly concentrated on the impacts of long-term rainfall trends on CH4 response, with limited exploration of the effects of extreme droughts and their timing on CH4 uptake. Ecological consequences of extreme climate events vary depending on their seasonal timing (Hu et al., 2021). Besides, drought in growing season may impact the ecosystem's structure and functionality (Li et al., 2021). Prior research indicated that seasonal timing of drought regulates soil moisture, carbon and N cycles, and biomass (Wu et al., 2020; Canarini et al., 2021; Deng et al., 2021). However, how the seasonal timing regulates the response of soil CH4 uptake to extreme drought remains unclear.
In our study, we carried out a manipulative experiment in a semi-arid steppe in Inner Mongolia Autonomous Region, China. We observed CH4 uptake and pmoA abundance of native vegetation communities in grassland to investigate the impact of extreme drought events occurring during different growing stages on CH4 uptake. We hypothesized that: (1) extreme drought events would increase CH4 uptake regardless of seasonal timing; and (2) the magnitudes and pathways of drought impacts on CH4 uptake are reliant seasonal timing.

2 Material and methods

2.1 Study area

The study area (44°18′N, 116°45′E; 1079 m a.s.l) is located in a semi-arid grassland of Inner Mongolia Autonomous Region, China. The experiment, established on the Maodeng Pasture, is based on extreme climate events and biodiversity platform of the Animal Ecology Research Station of the Chinese Academy of Sciences. The dominant species are Leymus chinensis (Trin. ex Bunge) Tzvelev, Agropyron cristatum (L.) Gaertn., Cleistogenes squarrosa (Trin.) Keng, and Carex duriuscula C. A. Mey. Average annual precipitation is 350-450 mm. Soil type in this area is chestnut soil, which is composed of 60.0% sand, 18.0% clay, and 17.0% silt.

2.2 Experimental design

According to long-term rainfall records from the climate database of local meteorological station (Xilin Gol League Meteorological Administration) throughout the span of 1953-2018, we defined a period of 50 consecutive days without effective rainfall (single rainfall amount <3 mm) as extreme drought. We divided the growing season in the study area into early (25 April-13 June), middle (14 June-3 August), and late (4 August-25 September) stages depending on continuous phenological observation. According to classification above, we set up four treatments of drought in the main plots with three replications: drought in early, middle, and late growing stages, and control. In total, there were 12 plots, each occupying an area of 2 m×2 m and 1 m intervals between plots. The extreme drought treatment was achieved by covering the plots with rain shelters to prevent natural rainfall (Zheng et al., 2023).

2.3 CH4 flux measurement

CH4 flux was measured 3 times each month during growing season in 2021 using static chamber sampling-gas chromatography method (Li et al., 2016). Prior to the experiment, we installed a waterproof stainless-steel frame with an area of 50 cm×50 cm and a height of 10 cm, which contained a water channel inside. Gas samples were gathered utilizing a stainless-steel static chamber in the morning, with dimensions of 50 cm in length, 50 cm in width, and 50 cm in height, which was encased in a thick thermal insulation foam plastic. A previous study conducted at this area indicated that CH4 fluxes from 09:00 to 12:00 (LST) represented the daily average values in this grassland (Dong et al., 2020). During the sampling period, we used a 50 mL syringe equipped with a three-way stopcock to extract gas samples from the container at 0, 10, 20, 30, and 40 min. Subsequently, these samples were analyzed using a gas chromatography system (Agilent 7890A GC System, Agilent Technologies Inc., Palo Alto, USA) to determine CH4 concentrations.
After the samples were collected, we measured their CH4 concentrations. The analysis of CH4 concentration used a one-time injection, dual-valve, and dual-column separation gas path, and was detected by flame ionization detector and electron capture detector of the gas chromatography. The calculation formula is as follows (Liu et al., 2014):
F = ρ × h × d c d t × 273.15 273.15 + T ,
where F is the CH4 flux (mg C/(m2•h)); ρ is the CH4 gas density (μg/m3); h is the height of chamber (m); dc/dt is the linear slope of CH4 concentration change with respect to time during measurement period; and T is the average air temperature inside the chamber during sampling (°C).

2.4 Soil property measurement

During the process of measuring CH4 flux, soil temperature measurement was conducted employing a thermometer (TL-883, Tonglixing Technology Co. Ltd., Shenzhen, China).
Soil water content (SWC) was measured three times per month utilizing Time Domain Reflectometry (TDR 300, Spectrum Technologies Inc., Aurora, USA) equipped with a 20-cm probe. Three soil cores were obtained from each quadrant at a depth range of 0-10 cm for soil sampling (each with a diameter of 3 cm) and then combined. Prior to combining, we sieved plant litter and roots using a 2-mm sieve. During transit, the soil samples were stored on ice within a low-temperature container. Once transported, they were promptly stored at a temperature of -80°C for later analysis. We measured the amount of inorganic N in each sample. The soil samples underwent extraction using 2 M KCl, and the extracts were analyzed for ammonium-N (NH4+-N) and nitrate-N (NO3--N) using a continuous flow ion auto-analyzer (AutoAnalyzer3, Seal Analytical, England, UK).

2.5 Deoxyribonucleic acid (DNA) extraction and quantitative polymerase chain reaction (qPCR)

For the extraction of DNA, we followed the provided instructions and used the Power Soil DNA Isolation Kit (MOBIO Laboratories, Carlsbad, USA), and 0.5 g of fresh soil was utilized. Subsequently, the quality of the extracted soil DNA was evaluated with a NanoDrop 2000 UV-Vis spectrophotometer (Thermo Fisher Scientific, Wilmington, USA). We chose to use the Eppendorf Masterpiece realplex sequence detection device (Eppendorf-Netheler-Hinz, Hamburg, Germany) for quantitative polymerase chain reaction (qPCR). We constructed standard curves using plasmid DNA in a series of ten-fold dilutions. The primer sets utilized for amplifying the pmoA were 5′-GGNGACTGGGACTTCTGG-3′ and 5′-CCGGMGCAACGTCYTTACC-3′. The qPCR reaction mixture, totaling 20.0 μL, comprised 1.0 μL of DNA template, 0.2 μL each of the forward and reverse primers, 10.4 μL of a mixture containing Rox dye and Takara SYBR®Premix Ex Taq™ (Perfect RealTime; TaKaRa Bio Inc., Dalian, China), and 8.4 μL of sterile water. After thoroughly mixing the reaction solution, we dispensed 20.0 μL into each well of a 96-well plate. To detect potential contamination, we included a negative control by dispensing 19.0 μL of the qPCR reaction solution (without DNA template) into a designated well. The pmoA gene sequential reaction conditions were as follows: an initial denaturation at 95°C for 30 s, followed by 40 cycles at 95°C for 30 s, 60°C for 45 s, and 68°C for 45 s, with a final extension at 80°C for 30 s (Zheng et al., 2023).

2.6 Statistical analysis

For the native vegetation community, we used a two-way analysis of variation (ANOVA) and a mixed-effects model (Lme function in NLME package of the R software v.4.1.1) to test and analyze the impact of drought in early, middle, and late growing stages on CH4 uptake, NH4+-N, NO3--N, and pmoA abundance. Prior to performing an ANOVA, we evaluated the normality of error terms utilizing Kolmogorov-Smirnov test, and if the errors were not normally distributed, we applied a square-root transformation to the data. Subsequently, we evaluated homoscedasticity, or the equality of variances, by employing the Levene test. We employed a mixed-effects model to examine the effects of drought on early, middle, and late growth stages of an artificial population. Duncan's test was employed to evaluate the disparities in the mean values of these variables, considering varying drought treatments and species compositions within the same year. A P<0.05 level was judged statistically significant. The analyses above were performed using R software. In addition, a structural equation model (SEM) was used to analyze both the immediate and secondary effects of non-biological factors (SWC, soil available N, and aboveground biomass (AGB)) and biological factor (pmoA abundance). SEM analysis was conducted using AMOS v.24.0 software (IBM, SPSS, Armonk, USA).

3 Results

3.1 SWC

During various growth stages, the average SWC was significantly reduced by extreme drought. Average SWC during drought in early, middle, and late growing stages decreased by 15.0%, 28.0%, and 21.0%, respectively, compared with control (Fig. 1; Table 1). Negative impact of drought on SWC primarily occurred during treatment period, while SWC of drought in early and middle growing stages recovered to the level of control after treatment. In contrast, due to insufficient precipitation input during drought in late growing stage, SWC did not recover, thereby prolonging the persistence of extreme drought effects (Fig. 1).
Fig. 1 Variations in seasonal (a) and average (b) soil water content (SWC) under different drought treatments. Different lowercase letters in Figure 1b indicate significant differences among different treatments at P<0.05 level. Bars are standard errors. DE, DM, and DL are droughts in early, middle, and late growing stages, respectively. CK, control. The abbreviations are the same in the following figures.
Table 1 Effects of drought in early, middle, and late growing stages on SWC, NH4+-N, NO3--N, AGB, CH4 uptake, and pmoA abundance
Treatment SWC NH4+-N NO3--N
F P F P F P
DE 4.827 0.0370 8.272 0.0210 3.195 0.0410
DM 5.686 0.0250 0.113 0.7450 1.698 0.0300
DL 2.844 0.0700 1.471 0.2590 1.094 0.3260
Treatment AGB CH4 uptake pmoA
F P F P F P
DE 0.055 0.0550 6.292 0.0370 28.103 0.0410
DM 1.338 0.2820 7.455 0.0480 87.063 <0.0001
DL 7.345 0.0270 15.258 0.0400 45.627 0.0001

Note: DE, DM, and DL are droughts in early, middle, and late growing stages, respectively; SWC, soil water content; AGB, aboveground biomass; CH4, methane.

3.2 NH4+-N, NO3--N, pmoA abundance, and AGB

Effects of extreme drought on inorganic N, pmoA abundance, and AGB depended on seasonal timing (Table 1). Drought in early growing stage significantly increased NH4+-N content (P<0.05), while drought in middle and late growing stages did not have a significant influence on NH4+-N (Fig. 2a). NO3--N was reduced by drought in early and middle growing stages but did not affect by drought in late growing stage (Fig. 2b). Drought in three growing stages increased pmoA abundance and the most positive effects were found in drought in middle growing stage (Fig. 2c). AGB showed a decreasing trend under all drought treatments. However, decrease in AGB was statistically significant (P<0.05) only in drought in late growing stage (Fig. 2d).
Fig. 2 Variations in NH4+-N (a), NO3--N (b), pmoA gene copy number (c), and AGB (d) under different drought treatments. AGB, aboveground biomass. Different lowercase letters indicate significant differences among different treatments at P<0.05 level. Bars are standard errors.

3.3 CH4 uptake

CH4 uptake significantly increased under drought treatments (P<0.05). Drought in early, middle, and late growth stages increased CH4 uptake by 47.0%, 44.0%, and 58.0%, respectively, in comparison with the control (Fig. 3). However, there was no significant difference in average of CH4 uptake among drought treatments. During drought treatment period, there was a significant increase in CH4 uptake by 34.0%, 46.0%, and 66.0% under drought in early, middle, and late growing stages, respectively (Fig. 4). After drought treatment, CH4 uptake under drought in early and late growing stages quickly returned to ambient levels, while drought in middle growing stage maintained a higher level than control during short term (about 1 week) (Fig. 4). Specifically, extreme drought increased CH4 sink, and CH4 uptake under drought in late growing stage was greater than those in early and middle growing stages.
Fig. 3 Seasonal dynamics (a) and mean (b) of CH4 uptake under different drought treatments. Different lowercase letters in Figure 3b indicate significant differences among different treatments at P<0.05 level. Bars are standard errors.
Fig. 4 CH4 uptake before, during, and after drought treatments. (a), drought in early growing stage; (b), drought in middle growing stage; (c), drought in late growing stage. * indicates significant differences between treatments at P<0.05 level. Bars are standard errors.
Multiple regression analyses indicated that impact of drought in early growing stage on the rate of CH4 uptake was greater than those in middle and late growing stages with higher standardized regression coefficients (Table 2). However, drought in middle growing stage had a greater impact on pmoA abundance, as evidenced by a higher standardized regression coefficient (Table 2).
Table 2 Multiple regression analyses of drought on CH4 uptake and pmoA abundance
Regression equation R2 P SEDE SEDM
CH4 uptake=124.80+1.15SWC-0.98AGB+17.23DE+13.86DM 0.973 0.02 7.28 2.99
pmoA=3.25×107-1.72×106SWC+9.01×105AGB-1.82×107DE+3.27×107DM 0.989 0.02 1.42×107 1.10×107

Note: SE, standardized regression coefficient; DE and DM are droughts in early and middle growing stages, respectively.

3.4 Impact of abiotic and biotic factors on CH4 uptake

SEM analysis demonstrated that SWC had a detrimental impact on CH4 uptake and pmoA abundance across drought treatments. Besides, pmoA abundance and NO3--N were significantly negatively correlated with CH4 uptake under droughts in early and middle growing stages. However, this negative correlation was not significant under drought in late growing stage. AGB and NH4+-N showed no significant relationships with drought (Fig. 5).
Fig. 5 Structural equation model (SEM) showing effects of abiotic factors and biotic factors on CH4 uptake under drought in early (a), middle (b), and late (c) growing stages. Line with orange color indicates positive path coefficients, and line with green color indicates negative path coefficients. Solid and dashed lines represent significant and insignificant path coefficients, respectively. RMSEA, root mean square error of approximation; CFI, comparative fit index. *, significant at P<0.05 level; **, significant at P<0.01 level.

4 Discussion

4.1 Drought increased CH4 uptake regardless of seasonal timing

Results showed a significant increase in CH4 uptake caused by extreme drought, regardless of seasonal timing in our study (Fig. 1), thus supporting our first hypothesis, which is in accordance with previous research findings (Fest et al., 2015). Apparently, soil water content is the main driving factor of CH4 uptake (Hiltbrunner et al., 2012; Yu et al., 2017; Lemoine et al., 2018; Ni et al., 2019; Li et al., 2020), which affects both soil CH4 generation and CH4 oxidation (Xu et al., 2015). These findings provide more evidence that soil has a stronger capacity to oxidize CH4 as soil moisture decreases, which is the most important abiotic factor affecting CH4 oxidation under drought. Previous study observed that there was a bell-shaped relationship between soil moisture and CH4 uptake (Dijkstra et al., 2011; Zhang et al., 2021). Besides, low SWC inhibits the activity of methanotrophs (as indicated by biomarker gene pmoA), causing a reduction in CH4 oxidation capacity and consequently impeding soil CH4 uptake (Yarwood, 2018; Zhang et al., 2022). However, CH4 uptake and pmoA abundance, in this study, both showed an increase under drought treatments. Research has shown that the threshold value of soil CH4 uptake to SWC is 8.2% in the temperate grassland of Inner Mongolia (Mei, 2018). We found that SWC consistently decreased, reaching approximately up to 10.0% under drought treatments. It can be inferred that drought did not decrease SWC to a level that might inhibit CH4 uptake. Instead, it induced SWC closer to the threshold, thereby increasing soil CH4 uptake. Previous research has found that when SWC is less than 5.0%, methanotrophic bacteria cease to oxidize (van den Pol-Van Dasselaar et al., 1998). However, in our study, abundance of pmoA increased under drought treatments, indicating that drought did not suppress the activity of methanotrophs. The methanotroph's activity and the proportionate amount of CH4 availability would determine the ideal moisture for CH4 uptake (Zheng et al., 2024). This is because drought promotes soil aeration, which subsequently boosts the accessibility of CH4 and stimulates the oxidation of CH4 in the soil (Fest et al., 2015), even though the arid soil conditions limited the activity of methanotroph (Dijkstra et al., 2011). Therefore, we showed that all drought treatments grew up soil CH4 uptake, which maybe the reason that drought did not reduce SWC to a level inhibiting methanotroph's activity. This result implies that under future climate conditions, the occurrence of extreme drought events will further enhance CH4 sink in the growing season of native vegetation communities in the temperate semi-arid grassland of Inner Mongolia.

4.2 Effects of drought on CH4 uptake in different seasonal timing

Although drought in different growing stages increased CH4 uptake, the extent accorded to the seasonal timing. Compared with drought in middle and late growing stages, drought in early growing stage had the most positive effects on CH4 uptake (Table 2). This may be explained by the fact that, in comparison to the control, the drought in early growing stage had the least precipitation (33 mm) (166 mm in middle and 152 mm in late growing stage, respectively) and thereby led to the least reduction in SWC. A previous study indicated that plants under drought stress exude ethylene into the soil, which inhibits methane oxidation in the soil air (Zhou et al., 2013). From this, it may be inferred that the decrease in SWC under drought in early growing stage was less than those in middle and late growing stages. Therefore, when the plants were subjected to less drought stress, the emission of ethylene reduced and soil CH4 oxidation capacity increased.
In addition, soil inorganic N is also a major factor affecting CH4 uptake. The main forms of inorganic N in soil are NH4+-N and NO3--N (Binkley and Hart, 1989). Soil inorganic N may influence CH4 uptake by limiting the growth of methanotrophic bacteria or methane oxidase activity (Aronson et al., 2013). Drought in early and middle growing stages reduced soil NO3--N content by reducing soil moisture, indicating that drought can decrease NO3--N content in the soil (Fig. 5). Evidence has indicated that soil mineralization is promoted when soil moisture decreases and soil environment becomes arid (Cregger et al., 2014). However, soil mineralization induced by drought treatment solely stimulated an increase in NH4+-N content, while impeding the decrease of NO3--N content (Song et al., 2001). We found that drought-induced reduction in NO3--N content enhanced soil CH4 uptake, thereby promoting the process. Previous studies have suggested that N may hinder CH4 uptake (Bodelier and Laanbroek, 2004; Bodelier, 2011). This may be because NO3--N causing soil acidification or enriching soil Al3+, both of which can directly inhibit CH4 oxidation (Le and Roger, 2001). Besides, Al3+, which often exerts a strong toxic effect on soil pmoA, is also prone to enrichment in acidic soil and may inhibit the oxidation of CH4 in the soil. However, in our study, the effect of drought in late growing stage on NO3--N content was not significant.
Methanotroph activity, reflected by pmoA abundance, is also an important factor affecting CH4 uptake. About 90.0% of the global CH4 is consumed through chemical oxidation reactions in the atmosphere (Bousquet et al., 2006), while only 8.0% of the total atmospheric CH4 undergoes oxidation by dry soil. However, this biological pathway represents nature sole mechanism for consuming atmospheric CH4 and is widely recognized as the most effective means of regulating human-induced CH4 sink. The process of soil oxidation of CH4 is a complex biological process involving methanotroph (Bender and Conrad, 1992). We found pmoA abundance directly (Fig. 5a) or indirectly (Fig. 5b) affected CH4 uptake under drought in early and middle growing stages. However, CH4 uptake was mainly influenced by soil moisture under drought in late growing stage (Fig. 5c), indicating that the impact of pmoA abundance on CH4 uptake was not as significant as that of soil moisture under drought in late growing stage. This result was consistent with previous studies that evaluating CH4 oxidation activity in the soil based on pmoA abundance was not entirely possible (Sabrekov et al., 2019).

5 Conclusions

Extreme drought consistently promoted CH4 uptake regardless of seasonal timing. Moreover, drought in early growing stage more strongly affected CH4 uptake than those in middle and late growing stages. Extreme drought can directly affect CH4 oxidation capacity of soil in the temperate grassland of Inner Mongolia Autonomous Region by enhancing soil aeration and soil moisture, resulting in a significant and direct effect on this process. Additionally, reduced soil moisture led to a low NO3--N content, and high pmoA abundance promoted the oxidation capacity of soil CH4 under drought in early and middle growing stages. However, these mechanisms were not found under drought in late growing stage, indicating seasonal timing of drought regulated CH4 uptake. An increase in drought in the future would enhance CH4 sink in temperate grassland, which would result in the negative feedback to global climate warming.

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This study was funded by the National Natural Science Foundation of China (42041005, U20A2050, U21A20240), the Weiqiao-UCAS (University of Chinese Academy of Sciences) Special Projects on Low-Carbon Technology Development (GYY-DTFZ-2022-006), and the Fundamental Research Funds for the Central Universities (E1E40607).

Author contributions

Conceptualization: ZHANG Wenwen, PAN Yue, WEN Fuqi; Methodology: WEN Fuqi; Formal analysis: WEN Fuqi, ZHANG Wenwen, PAN Yue; Writing - original draft preparation: ZHANG Wenwen, PAN Yue; Writing - review and editing: ZHANG Wenwen, PAN Yue, HAO Yanbin; Visualization: ZHANG Wenwen, PAN Yue; Funding acquisition: HAO Yanbin; Resources: HAO Yanbin; Supervision: HAO Yanbin, FU Juanjuan, HU Tianming, YANG Peizhi. All authors approved the manuscript.

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