Effects of landuse change on CH4 soil-atmospheric exchange in alpine meadow on the Tibetan Plateau

Degradation of shrub meadows and reclamation of alpine meadows may heavily affect the soil sink for atmospheric methane (CH₄), but this is poorly understood. Therefore, in situ measurements of atmospheric CH₄ consumption were conducted in four landuse types: natural alpine meadow (NM), Elymus nutans pasture (EP), herbaceous meadow in shrub (HS), and a P. fruticosa shrub meadow (PS) within two years. CH₄ fluxes were measured using static chambers and gas chromatography. All four types of land use showed atmospheric CH₄ sink throughout the two years, with mean soil CH₄ consumption rates at 24.6±10.9, 33.8±15.0, 39.8±10.3, and 28.1±12.1 µg CH₄·m⁻²·hr⁻¹ for NM, EP, PS, and HS, respectively. Soil CH₄ consumption increased by 40% by reclamation from NM to EP, while it decreased by 30% by degradation from PS to HS. Soil CH₄ consumption in four types of land use was significantly correlated with temperature at 5 cm depth (P<0.01) and the soil water-filled pore space (WFPS) (P<0.05). Temperature showed stronger effects on soil CH₄ consumption than WFPS, except in NM. UV radiation was positively correlated with soil CH₄ consumption with increasing temperature and decreasing soil moisture. These findings indicate that a decrease in the grazing pressure in shrub meadows and increase in the area of artificial pasture reclaimed from alpine meadows would enhance the CH₄ sink in alpine meadows on the Tibetan Plateau.