Temperature dependency of methane emission from alkaline wetland under warming effect: Synergistic effects of soil properties and microbial community.

Alkaline wetlands, experienced large temperature changes seasonally and were sensitive to global climate changes. Climate warming altered biochemical cycling and further threatened ecosystem imbalance, affecting methane (CH₄) emissions budget. To reveal the complex interplay of soil properties and microbial communities governing CH₄ emissions responding to temperature changes in alkaline wetland, 60-day incubation experiments with temperature gradients (5°C, 18°C, 25°C, 35°C) were conducted using soil collected from Zhalong wetland in northern China. The results showed that CH₄ emission increased along with elevated temperature and peaked at 35°C with 169.10±65.42 mg C kg^-1 dry soil, 343.7-fold higher than that at 5°C. Increased NH₄⁺-N and dissolved organic carbon concentrations induced by elevated temperatures significantly regulated CH₄ emission (p<0.05). Hydrogenotrophic methanogens (Methanobacterium) exhibited greater sensitivity to temperature fluctuations than acetoclastic methanogens (Methanosarcina, Methanosaeta), and dominated in archaeal communities with proportion of 21.8% under low and moderate temperature. Moreover, the accelerated Fe reduction process stimulated enrichment of methanogen (Methanobacterium, 8.8%→9.3%) while suppressing methanotrophs (Candidatus _Methanoperedens, 5.0%→4.2%), thereby contributing to higher CH₄ emissions under rising temperature. Besides, upregulated methanogenic genes (mcrA, fwdA, cdhC, mtrH) contributed to increased CH₄ production at 35°C. This study deepened our understandings of CH₄ dynamics and microbial responses to temperature changes in Zhalong wetland, highlighting its potential role as microbe-driven CH₄ emission source under warming scenarios.