Abstract
As the atmospheric carbon dioxide (CO2) increases substantially, the spatial distribution of atmospheric CO2 should be considered when estimating the effects of CO2 on the carbon and water cycle coupling of terrestrial ecosystems. To evaluate this effect on future ecohydrological processes, the spatial-temporal patterns of CO2 were established over 1951 - 2099 according to the IPCC emission scenarios SRES A2 and SRES B1. Thereafter, water use efficiency (WUE) was used (i.e., Net Primary Production/Evaportranspiration) as an indicator to quantify the effects of climate change and uneven CO2 fertilization in China. We carried out several simulated experiments to estimate WUE under different future scenarios using a land process model (Integrated Biosphere Simulator, IBIS). Results indicated that the geographical distributions of averaged WUE have considerable differences under a heterogeneous atmospheric CO2 condition. Under the SRES A2 scenario, WUE decreased slightly with a 5% value in most areas of the southeastern and northwestern China during the 2050s, while decreasing by approximately 15% in southeastern China during the 2090s. During the period of the 2050s under SRES B1 scenario, the change rate of WUE was similar with that under SRES A2 scenario, but the WUE has a more moderate decreasing trend than that under the SRES A2 scenario. In all, the ecosystems in median and low latitude areas had a weakened effect on resisting extreme climate event such as drought. Conversely, the vegetation in a boreal forest had an enhanced buffering capability to tolerate drought events.
Highlights
Terrestrial ecosystems are of particular importance within the global carbon and water cycles because of the large carbon sequestrated in plants and the large hydrological effects by evaportranspiration (Alo et al 2008a; Bell et al 2010)
The Integrated Biosphere Simulator (IBIS) simulation driven by IPCC future climate data and spatial-temporal variability of atmospheric CO2 show that spatial patterns of Water Use Efficiency (WUE) are in similar agreement with other study results (Zhu et al 2011)
This study represents a first attempt to assess the future changes of WUE with the goal of understanding the interactions between carbon and water resources under climate change and spatial heterogeneity of atmospheric CO2 in China
Summary
Terrestrial ecosystems are of particular importance within the global carbon and water cycles because of the large carbon sequestrated in plants and the large hydrological effects by evaportranspiration (Alo et al 2008a; Bell et al 2010). Changes in the carbon and water cycle couplings of terrestrial ecosystems could have significant responses to environmental factors such as temperature, precipitation, and atmospheric CO2 (Arneth et al 2010). Water Use Efficiency (WUE), as a key indicator for the carbon and water cycle coupling of terrestrial ecosystems, is used to describe the trade-off between water loss and carbon gain in the process of plant photosynthesis (LeHouerou 1984; Baldocchi 1994) and perhaps reflect responses of plants to environmental stress on ecosystem processes (Huxman et al 2004). The increased CO2 concentration is important for future adaptation of WUE because it may directly stimulate plant photosynthesis and indirectly reduce plant water consumption through regulating stomatal conductance (Baldocchi 1997)
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