Temperature controls ecosystem CO₂ exchange of an alpine meadow on the northeastern Tibetan Plateau

• Published in: Global change biology Vol. 15; no. 1; pp. 221 - 228
• Main Authors: SAITO, MAKOTO, KATO, TOMOMICHI, TANG, YANHONG
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 2009; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: Alpine environments; alpine meadow; alpine meadows; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; carbon; Carbon dioxide; China; Climate change; CO2 fluxes; CO₂ fluxes; data collection; Ecology; Ecosystems; eddy covariance; eddy covariance method; Fluctuations; Fundamental and applied biological sciences. Psychology; General aspects; Global warming; Growing season; Light; Meadows; net ecosystem exchange; path analysis; photoperiod; Soil temperature; Synecology; Temperature; Temperature control; Temperature effects; Tibetan Plateau; China, People's Rep., Xizang, Tibetan Plateau; China; Grassland; path analysis; CO2 fluxes; Temperature; Carbon dioxide; Lawn; Environmental factor; alpine meadow; Exchange; Alpine vegetation; Eddy covariance method; Ecosystem; Qinghai-Xizang Plateau
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/j.1365-2486.2008.01713.x

Alpine ecosystems are extremely vulnerable to climate change. To address the potential variability of the responses of alpine ecosystems to climate change, we examined daily CO₂ exchange in relation to major environmental variables. A dataset was obtained from an alpine meadow on the Qinghai-Tibetan Plateau from eddy covariance measurements taken over 3 years (2002-2004). Path analysis showed that soil temperature at 5 cm depth (Ts₅) had the greatest effect on daily variation in ecosystem CO₂ exchange all year around, whereas photosynthetic photon flux density (PPFD) had a high direct effect on daily variation in CO₂ flux during the growing season. The combined effects of temperature and light regimes on net ecosystem CO₂ exchange (NEE) could be clearly categorized into three areas depending on the change in Ts₅: (1) almost no NEE change irrespective of variations in light and temperature when Ts₅ was below 0 °C; (2) an NEE increase (i.e. CO₂ released from the ecosystem) with increasing Ts₅, but little response to variation in light regime when 0 °C[less-than or equal to]Ts₅[less-than or equal to]8 °C; and (3) an NEE decrease with increase in Ts₅ and PPFD when Ts₅ was approximately >8 °C. The highest daily net ecosystem CO₂ uptake was observed under the conditions of daily mean Ts₅ of about 15 °C and daily mean PPFD of about 50 mol m⁻² day⁻¹. The results suggested that temperature is the most critical determinant of CO₂ exchange in this alpine meadow ecosystem and may play an important role in the ecosystem carbon budget under future global warming conditions.