Carbon dioxide exchange between the atmosphere and an alpine meadow ecosystem on the Qinghai–Tibetan Plateau, China

We used the eddy covariance method to measure the CO2 exchange between the atmosphere and an alpine meadow ecosystem (37°29–45′N, 101°12–23′E, 3250 m a.s.l.) on the Qinghai–Tibetan Plateau, China in the 2001 and 2002 growing seasons. The maximum rates of CO2 uptake and release derived from the diurnal course of CO2 flux (FCO2) were −10.8 and 4.4 μmol m−2 s−1, respectively, indicating a relatively high net carbon sequestration potential as compared to subalpine coniferous forest at similar elevation and latitude. The largest daily CO2 uptake was 3.9 g C m−2 per day on 7 July 2002, which is less than half of those reported for lowland grassland and forest at similar latitudes. The daily CO2 uptake during the measurement period indicated that the alpine ecosystem might behave as a sink of atmospheric CO2 during the growing season if the carbon lost due to grazing is not significant. The daytime CO2 uptake was linearly correlated with the daily photosynthetic photon flux density each month. The nighttime averaged FCO2 showed a positive exponential correlation with the soil temperature, but apparently negative correlation with the soil water content.