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<p>Methane (CH<sub>4</sub>) fluxes in permafrost regions are commonly represented as monotonic functions of temperature, despite pronounced seasonal hydrological variability and habitat heterogeneity. Here, using two years of in situ high-frequency measurements, we examined whether CH<sub>4</sub> fluxes exhibit trajectory-dependent temperature responses across a forest–wetland ecotone in a degrading permafrost landscape, and how hydrological and microbial processes modulated. We found that: (1) Wetland patches consistently acted as CH<sub>4</sub> sources, with an average flux of 5.14&#xa0;nmol&#xa0;m<sup>−2</sup>&#xa0;s<sup>−1</sup>, whereas forests exhibited seasonal source–sink shifts and a much lower mean flux of 0.08&#xa0;nmol&#xa0;m<sup>−2</sup>&#xa0;s<sup>−1</sup>. Importantly, phase-stratified segmented regressions revealed distinct, nonlinear temperature thresholds and hysteresis in wetlands, with contrasting CH<sub>4</sub>–temperature relationships during warming and cooling phases, while forests showed weaker trajectory dependence. (2) Across habitats and seasons, soil methanogenic communities varied more strongly than methanotrophic communities and explained a larger (35%) of CH<sub>4</sub> flux variability than methanotrophic attributes (21%) and soil properties (24%). (3) Soil moisture and inorganic nitrogen emerged as key factors linking hydrological conditions, microbial communities, and CH<sub>4</sub> dynamics. These findings demonstrate that CH<sub>4</sub> fluxes in permafrost ecotones are governed by the interaction of phase-dependent temperature responses, hydrological constraints, and microbial processes. Incorporating warming–cooling asymmetry and hydrological–microbial coupling may improve the prediction of CH<sub>4</sub> dynamics in heterogeneous permafrost landscapes undergoing thaw.</p>

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Temperature-dependent soil CH4 fluxes and their drivers across a forest–wetland ecotone in degrading permafrost, Northeast China

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月29日

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  • Xingfeng Dong ,
  • Chao Liu,
  • Miao Li,
  • Xiaodong Wu,
  • Haoran Man,
  • Zhichao Zheng,
  • Huiren Jiang,
  • Dongyu Yang,
  • Biao Li,
  • Ye Ma,
  • Guangying Zhao,
  • Shuying Zang

摘要

Methane (CH4) fluxes in permafrost regions are commonly represented as monotonic functions of temperature, despite pronounced seasonal hydrological variability and habitat heterogeneity. Here, using two years of in situ high-frequency measurements, we examined whether CH4 fluxes exhibit trajectory-dependent temperature responses across a forest–wetland ecotone in a degrading permafrost landscape, and how hydrological and microbial processes modulated. We found that: (1) Wetland patches consistently acted as CH4 sources, with an average flux of 5.14 nmol m−2 s−1, whereas forests exhibited seasonal source–sink shifts and a much lower mean flux of 0.08 nmol m−2 s−1. Importantly, phase-stratified segmented regressions revealed distinct, nonlinear temperature thresholds and hysteresis in wetlands, with contrasting CH4–temperature relationships during warming and cooling phases, while forests showed weaker trajectory dependence. (2) Across habitats and seasons, soil methanogenic communities varied more strongly than methanotrophic communities and explained a larger (35%) of CH4 flux variability than methanotrophic attributes (21%) and soil properties (24%). (3) Soil moisture and inorganic nitrogen emerged as key factors linking hydrological conditions, microbial communities, and CH4 dynamics. These findings demonstrate that CH4 fluxes in permafrost ecotones are governed by the interaction of phase-dependent temperature responses, hydrological constraints, and microbial processes. Incorporating warming–cooling asymmetry and hydrological–microbial coupling may improve the prediction of CH4 dynamics in heterogeneous permafrost landscapes undergoing thaw.