South China Institute of Botany Gets Grant of Key Program from Natural Science Foundation of China on Forest Transpiration

With previous projects funded by Natural Science Foundation of China (NSFC), Chinese Academy Science Knowledge Innovative Program and Natural Science Foundation of Guangdong Province, the Research Group of Ecosystem Physiology, headed by Prof. ZHAO Ping, has conducted research on plantation water use and H2O/CO2 exchange fluxes between forest canopy and atmosphere. This year they applied and successfully won a grant of key program from NSFC based on the long-term research effort. The coming new fund will mainly focus on the coordinated regulation of forest transpiration with special references to vegetation restoration and global warming.

Climate warming alters the rainfall pattern at local scales. Meanwhile the large area re-vegetation inevitably causes impact on local water budget. How forests regulate transpiration in order to adapt to the new distribution pattern of water and to maintain effective water use is a pressing issue needing to be addressed. The response of canopy stomatal conductance (Gs), a determinant for efficiency of forest transpiration, to evaporative demand is affected by tree hydraulic architecture. Because of the complexity of forest canopy, the vapor exchange between forest and atmosphere is in most cases decoupled. Therefore it could hardly describe the regulation of water flux accurately if only based on stomatal changes.

The new project hypothesizes that hydraulic conductance and canopy stomatal conductance of trees jointly control the response of forest water use to evaporative demand in coordination of water potential threshold of tree. To reveal the mechanism of coordinated regulation of forest transpiration by Gs and hydraulic conductance, the leaf gas exchange, sap flow, micrometeorological as well as other environmental factors will be integrated to investigate the decoupling coefficient between canopy and atmosphere. The effect of hydraulic conductance calculated from sap flow and leaf-to-soil water potential gradient on the response sensitivity of Gs to vapor pressure deficit will also be studied. It is expected that research results might help to assess the potential ecological effect of forest on water resource use under the future climate scenarios.