Characterizing Spatiotemporal Variability of Methane Uptake across a Climate Transect in Inner Mongolia Steppe

Grassland soils are important biological sink for atmospheric methane (CH₄), but the strength of CH₄ uptake remains uncertain due to large spatiotemporal variation and the lack of in situ measurements at regional scale. Here, we report the temporal and spatial patterns of CH₄ uptake across a 1200 km transect in Inner Mongolia steppe ecosystems, ranging from meadow steppe in the east plain to typical and desert steppe on the west plateau. In general, the temporal pattern of CH₄ uptake followed a unimodal curve during the growing season, with peak values observed in August. Soil moisture was the dominant factor explaining the temporal pattern of CH₄ uptake. Across the transect, CH₄ uptake showed a skewed unimodal spatial pattern, with the peak rate observed in the typical steppe site and the west plateau generally showing higher uptake rates than the east plain. Together, growing season mean temperature, growing season precipitation, soil pH, and soil total carbon explained 54% of the variance in regional CH₄ uptake, with growing season mean temperature being the dominant driver. These findings are important for model development to more precisely estimate the soil CH₄ sink capacity in arid and semi-arid regions.