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Temperature controls ecosystem CO 2 exchange of an alpine meadow on the northeastern Tibetan Plateau
Author(s) -
SAITO MAKOTO,
KATO TOMOMICHI,
TANG YANHONG
Publication year - 2009
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2008.01713.x
Subject(s) - eddy covariance , ecosystem , plateau (mathematics) , environmental science , climate change , growing season , atmospheric sciences , ecosystem respiration , physical geography , ecology , geography , biology , geology , mathematical analysis , mathematics
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 CO 2 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 ( T s5 ) had the greatest effect on daily variation in ecosystem CO 2 exchange all year around, whereas photosynthetic photon flux density (PPFD) had a high direct effect on daily variation in CO 2 flux during the growing season. The combined effects of temperature and light regimes on net ecosystem CO 2 exchange (NEE) could be clearly categorized into three areas depending on the change in T s5 : (1) almost no NEE change irrespective of variations in light and temperature when T s5 was below 0 °C; (2) an NEE increase (i.e. CO 2 released from the ecosystem) with increasing T s5 , but little response to variation in light regime when 0 °C≤ T s5 ≤8 °C; and (3) an NEE decrease with increase in T s5 and PPFD when T s5 was approximately >8 °C. The highest daily net ecosystem CO 2 uptake was observed under the conditions of daily mean T s5 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 CO 2 exchange in this alpine meadow ecosystem and may play an important role in the ecosystem carbon budget under future global warming conditions.