Carbon and water cycles, as the two fundamental ecological processes, are critically important for global change studies. However, in coupling the two processes, few previous efforts are found to base their assumptions on the plant eco-physiology. With the observation data obtained through LI-6400 System and eddy covariance system of ChinaFLUX, this study analyses the eco-physiology mechanism of the coupling relationship between photosynthesis and transpiration at leaf level by understanding the variation of plant photosynthesis, stomatal behaviors, transpiration and water use efficiency; the implications of environmental factors such as light intensity (PPFD), CO₂ concentration and air temperature on plant photosynthesis, stomatal conductance, transpiration and water use efficiency; and the coupling relationship among plant photosynthesis, stomatal conductance and transpiration.

It further clarifies the eco-physiology relationship between water and carbon cycles at ecosystem level from a perspective of ecosystem photosynthesis, transpiration, water use efficiency and control mechanism. Some models are also developed, such as the Synthesized model of Photosynthesis-Transpiration based on the Stomatal Behaviors, and Water-use Efficiency Model (SMPTSB), Forest landscape Productivity Model (FLPM), and Grassland Landscape Productivity Model (GLPM) at Landscape Level. Apart from these models, some other process-based models, including BEPS, VPM and EVLCO, are tested and enhanced.

Therefore, these studies, together with the spatialization of climatic factors, provide a reasonable theoretical basis for developing new models on the interactions between water and carbon cycles in terrestrial ecosystems and for understanding the biological control of water and carbon cycles in soil-vegetation-atmosphere continuous.

By Qiufeng WANG