Biophysical effects on the interannual variation in carbon dioxide exchange of an
alpine meadow on the Tibetan Plateau
Lei Wang1, Huizhi Liu1, Jihua Sun2, and Yaping Shao31LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 2Meteorological Observatory of Yunnan Province, Kunming 650034, China 3Institute for Geophysics and Meteorology, University of Cologne, Cologne, 50937, Germany
Received: 29 Nov 2016 – Accepted for review: 22 Dec 2016 – Discussion started: 23 Dec 2016
Abstract. Eddy covariance measurements from 2012 to 2015 were used to investigate the interannual variation in carbon dioxide exchange and its control over an alpine meadow on the southeast margin of the Tibetan Plateau. The annual net ecosystem exchange (NEE) from 2012 to 2015 was −114.2, −158.5, −159.9 and −212.6 g C m−2 yr−1 and generally decreased with the mean annual air temperature (MAT). An exception occurred in 2014, which had the highest MAT. This was attributed to higher ecosystem respiration (RE) and similar gross primary production (GPP) in 2014 because the GPP increased with MAT but became saturated due to the photosynthesis capacity limit. In the spring (March to May) of 2012, lower air temperature (Ta) and drought events delayed grass germination and reduced GPP. In the late wet season (September to October) of 2012 and 2013, the lower Ta in September and its negative effects on vegetation growth caused earlier grass senescence and significantly lower GPP. This indicates that the seasonal pattern of Ta greatly affected the annual total GPP, which is consistent with the result of the homogeneity-of-slopes model. The model shows that the climatic seasonal variation explained 48.6 % of the GPP variability, and the percentage of climatic interannual variation and the ecosystem functional change were 9.7 % and 10.6 %, respectively.
Wang, L., Liu, H., Sun, J., and Shao, Y.: Biophysical effects on the interannual variation in carbon dioxide exchange of an
alpine meadow on the Tibetan Plateau, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1059, in review, 2016.