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<p>Water-level fluctuations significantly impact carbon cycling in shallow-water wetlands by altering the decomposition of emergent plant litter. This study investigated how environmental conditions affect litter decomposition and fungal communities across a water-level gradient in the Baiyangdian wetland. Standardized litter bags were incubated in soil from three distinct habitats, viz. <i>Phragmites australis</i> (reed) platforms, water-land ecotones, and permanently flooded areas, to investigate the degradation of litter components, transformation of soil carbon, and the driving mechanisms of soil fungal communities during a 240-day litter decomposition period. The results indicated that water-land ecotone conditions significantly enhanced litter decomposition (<i>k</i> = 0.066) and promoted the accumulation of recalcitrant carbon fractions, as evidenced by a marked increase in the proportion of alkyl carbon (Alkyl C) from 45.37% to 58.82%. In contrast, prolonged flooding inhibited hydrolase activities, resulting in reduced carbon conversion efficiency, with O-alkyl carbon (O-alkyl C) decreasing by only 4.20%. However, flooding favored the physical accumulation of soil organic carbon (SOC), which increased by 1.87%. Fungal communities exhibited distinct network topological structures under varying water-level regimes, with the highest proportion of positive correlations (77.88%) observed in the water-land ecotone. Water-level drove a marked shift in the dominant fungi, most notably a dramatic rise of <i>Westerdykella</i> under the water-land ecotone. Structural equation modeling further revealed that water-level fluctuations significantly affected litter residual mass (<i>β</i> =  −0.896, <i>p</i> &lt; 0.001) and soil properties (<i>β</i> = 0.766, <i>p</i> &lt; 0.05). These environmental changes altered fungal network topology and shaped key enzyme activities, ultimately shaping carbon cycling pathways. These findings provide critical insights into the mechanisms by which environmental factors and microorganisms jointly modulate wetland plant litter decomposition and carbon cycling.</p>

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Impact of water-level fluctuations on Phragmites australis decomposition and carbon cycling: the role of fungal network topology

  • 期刊论文

  • 发表日期：

    2026年6月28日

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  • Hongjie Wang,
  • Yifan Liu,
  • Xueqing Xiao,
  • Jiaxin Liu,
  • Siqi Yu,
  • Shangwei Wang,
  • Hui Li,
  • Ling Liu

摘要

Water-level fluctuations significantly impact carbon cycling in shallow-water wetlands by altering the decomposition of emergent plant litter. This study investigated how environmental conditions affect litter decomposition and fungal communities across a water-level gradient in the Baiyangdian wetland. Standardized litter bags were incubated in soil from three distinct habitats, viz. Phragmites australis (reed) platforms, water-land ecotones, and permanently flooded areas, to investigate the degradation of litter components, transformation of soil carbon, and the driving mechanisms of soil fungal communities during a 240-day litter decomposition period. The results indicated that water-land ecotone conditions significantly enhanced litter decomposition (k = 0.066) and promoted the accumulation of recalcitrant carbon fractions, as evidenced by a marked increase in the proportion of alkyl carbon (Alkyl C) from 45.37% to 58.82%. In contrast, prolonged flooding inhibited hydrolase activities, resulting in reduced carbon conversion efficiency, with O-alkyl carbon (O-alkyl C) decreasing by only 4.20%. However, flooding favored the physical accumulation of soil organic carbon (SOC), which increased by 1.87%. Fungal communities exhibited distinct network topological structures under varying water-level regimes, with the highest proportion of positive correlations (77.88%) observed in the water-land ecotone. Water-level drove a marked shift in the dominant fungi, most notably a dramatic rise of Westerdykella under the water-land ecotone. Structural equation modeling further revealed that water-level fluctuations significantly affected litter residual mass (β =  −0.896, p < 0.001) and soil properties (β = 0.766, p < 0.05). These environmental changes altered fungal network topology and shaped key enzyme activities, ultimately shaping carbon cycling pathways. These findings provide critical insights into the mechanisms by which environmental factors and microorganisms jointly modulate wetland plant litter decomposition and carbon cycling.