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

Abstract

We used the eddy covariance method to measure the CO 2 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 CO 2 uptake and release derived from the diurnal course of CO 2 flux ( F CO 2 ) 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 CO 2 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 CO 2 uptake during the measurement period indicated that the alpine ecosystem might behave as a sink of atmospheric CO 2 during the growing season if the carbon lost due to grazing is not significant. The daytime CO 2 uptake was linearly correlated with the daily photosynthetic photon flux density each month. The nighttime averaged F CO 2 showed a positive exponential correlation with the soil temperature, but apparently negative correlation with the soil water content.