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| Titel |
Mechanisms underlying the spatial variation of WUE among terrestrial ecosystems in China |
| VerfasserIn |
Xianjin Zhu, Guirui Yu, Qiufeng Wang, Zhongmin Hu, Han Zheng, Junhua Yan, Huimin Wang, Fenghua Zhao, Junhui Zhang, Peili Shi, Yingnian Li, Liang Zhao, Yanbin Hao |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094315
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| Publikation (Nr.) |
 EGU/EGU2014-9719.pdf |
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| Zusammenfassung |
| Enhancing carbon uptake in terrestrial ecosystems is an alternative approach in mitigating
climate change, which needs consume amounts of water. Meanwhile, water cycle and carbon
cycle are closely coupled. Analyzing this coupling could improve our knowledge in
understanding the processes of water and carbon cycles.
Water use efficiency (WUE), here defined as the ratio of gross primary productivity (GPP)
and evaportranspiration (ET), representing the coupling relationship between carbon and
water cycles in terrestrial ecosystems, reflects the water requirement for carbon uptake.
Investigating the spatial pattern of WUE and its underlying mechanisms can provide insight
into the relationships between carbon and water cycles in terrestrial ecosystems and the
supportive capacity of water resources for carbon uptake.
Based on the eddy covariance measurements in 8 sites of ChinaFLUX, we analyzed the
spatial pattern of annual WUE (defined as the ratio of annual total GPP to annual total ET)
and its underlying mechanisms among forest ecosystems, grassland ecosystems and all types
of ecosystems. As ET was comprised by evaporation (E) and transpiration (T), we
used the Shuttleworth-Wallace model, a dual sources model, to separate ET into
E and T. Then WUE was divided into GPP/T and T/ET, which was affected by
ecophysiological processes and physical processes, respectively. By 1) approximating
photosynthesis rate and transpiration by GPP and T, 2) neglecting resistance by
the boundary layer and 3) approximating leaf temperature by air temperature, we
introduced inherent water use efficiency (IWUE) to represent the intrinsic water use
efficiency at the ecosystem level. Then WUE was divided into IWUE, 1/VPD and
T/ET.
Results indicate that the spatial pattern and the underlying mechanisms were distinct
different among ecosystem types. Among forest ecosystems in the North-South Transect of
East-China (NSTEC), the spatial variation of WUE was mainly affected by the variation of
1/VPD. However, among grassland ecosystems in the Chinese Grassland Transect (CGT),
T/ET was the main component determining the spatial variation of WUE. Across all
ecosystem types, IWUE and T/ET played an important role in shaping the spatial variation of
WUE. |
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