Strong temperature dependence and no moss photosynthesis in winter CO2 flux for a Kobresia meadow on the Qinghai–Tibetan plateau

We examined the CO2 exchange of a Kobresia meadow ecosystem on the Qinghai–Tibetan plateau using a chamber system. CO2 efflux from the ecosystem was strongly dependence on soil surface temperature. The CO2 efflux–temperature relationship was identical under both light and dark conditions, indicating that no photosynthesis could be detected under light conditions during the measurement period. The temperature sensitivity (Q10) of the CO2 efflux showed a marked transition around −1.0 °C; Q10 was 2.14 at soil surface temperatures above and equal to −1.0 °C but was 15.3 at temperatures below −1.0 °C. Our findings suggest that soil surface temperature was the major factor controlling winter CO2 flux for the alpine meadow ecosystem and that freeze–thaw cycles at the soil surface layer play an important role in the temperature dependence of winter CO2 flux.