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 carbon sink due to it high soilorganic content and low decomposition. However, the magnitude and dynamicsof carbon stock in alpine wetland ecosystems are not well quantified.Therefore, understanding how environmental variables affect the processesthat regulate carbon fluxes in alpine wetland meadow on the Qinghai-TibetanPlateau is critical. To address this issue, Gross Primary Production(GPP), Ecosystem Respiration (R_eco), and Net Ecosystem Exchange (NEE) wereexamined in an alpine wetland meadow using the eddy covariance method fromOctober 2003 to December 2006 at the Haibei Research Station of the ChineseAcademy of Sciences. Seasonal patterns of GPP and R_eco were closelyassociated with leaf area index (LAI). The R_eco showed a positiveexponential to soil temperature and relatively low R_eco occurred duringthe non-growing season after a rain event. This result is inconsistent withthe result observed in alpine shrubland meadow. In total, annual GPP wereestimated at 575.7, 682.9, and 630.97 g C m−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. Theseresults indicated that the alpine wetland meadow was a moderately source ofcarbon dioxide (CO₂). The observed carbon dioxide fluxes in the alpinewetland meadow were higher than other alpine meadow such as Kobresia humilis meadow andshrubland meadow.