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

Global Change Biology - Tập 15 Số 1 - Trang 221-228 - 2009
Makoto Saito1, Tomomichi Kato2, Yanhong Tang3
1Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba 305‐8506, Japan
2Ecosystem Change Research Program, Frontier Research Center for Global Change, Japan Agency for Marine–Earth Science and Technology, Yokohama, Kanazawa 236-0001, Japan,
3National Institute for Environmental Studies, Tsukuba 305–8506, Japan

Tóm tắt

AbstractAlpine 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≤Ts5≤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.

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Global Change Biology

Tập 15 Số 1

221-228

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