Seasonal variations in carbon dioxide exchange in an alpine wetland meadow on the Qinghai-Tibetan Plateau

摘要

Alpine wetland meadow could functions as a car-bon sink due to it high soil organic content and low decom-position. However, the magnitude and dynamics of carbon stock in alpine wetland ecosystems are not well quantified. Therefore, understanding how environmental variables affect the processes that regulate carbon fluxes in alpine wetland meadow on the Qinghai-Tibetan Plateau is critical. To address this issue, Gross Primary Production (GPP), Ecosystem Respiration (R_(eco)), and Net Ecosystem Exchange (NEE) were examined in an alpine wetland meadow using the eddy covariance method from October 2003 to December 2006 at the Haibei Research Station of the Chinese Academy of Sciences. Seasonal patterns of GPP and Reco were closely associated with leaf area index (LAI). The R_(eco) showed a positive exponential to soil temperature and relatively low Reco occurred during the non-growing season after a rain event. This result is inconsistent with the result observed in alpine shrubland meadow. In total, annual GPP were estimated at 575.7, 682.9, and 630.97 g Cm~(-2) in 2004, 2005, and 2006, respectively. Meanwhile, the R_(eco) were equal to 676.8, 726.4, 808.2 g C m~(-2), and thus the NEE were 101.1, 44.0 and 173.2 g C m~(-2). These results indicated that the alpine wetland meadow was a moderately source of carbon dioxide (CO_2). The observed carbon dioxide fluxes in the alpine wetland meadow were higher than other alpine meadow such as Kobresia humilis meadow and shrubland meadow.