Enhanced Methane Uptake under Light Conditions in an Alpine Tundra Ecosystem

Alpine tundra ecosystems are widely regarded as small but persistent sinks of atmospheric methane (CH₄), yet it remains unclear how ongoing climate-driven shifts in vegetation composition and productivity will alter CH₄ exchange. As a result, predicting whether the alpine tundra will act as a CH₄ sink or source in the future requires an understanding of the governing mechanisms and links between vegetation CH₄ production and consumption. To address this gap, we explored the drivers and magnitude of CH₄ and carbon dioxide (CO₂) fluxes across fine scale alpine tundra vegetation gradients in Kaska First Nations Ancestral territory, now known as northern British Columbia. Using a systematic grid approach, we measured fluxes and environmental parameters from 100 plots over a 3-day period during peak growing season. Our design captured dominant vegetation types and key transition zones of microclimatic gradients across a south facing alpine slope. We found that CH₄ uptake was greater under light vs dark chamber conditions across most plant functional types, suggesting a link between photosynthesis and CH₄ uptake. Our light-only chamber condition statistical model further indicated that CH₄ uptake covaries most strongly with net ecosystem exchange, soil temperature, and nutrient availability (Cu, P, and total N). Together, these results suggest that climate-driven changes in vegetation structure and productivity may alter CH₄ uptake strength in alpine tundra ecosystems, underscoring the importance of resolving plant-soil processes for predicting future CH₄ dynamics.