Abstract:Predicted changes in global and regional climate resulting from increasing atmospheric CO2 concentrations and other greenhouse gases have raised concerns about the likely impacts of precipitation and temperature on plant water use. Understanding effects of environmental changes on vegetation needs to explore the mechanism of the exchanges of energy, water vapour and CO2 between vegetation and the atmosphere. Transpiration is an important component of this exchange for it‘s the major pathway for both water and energy leaving the forest ecosystem. At present, sapflow techniques are being increasingly used to monitor tree responses to rapid changing environment instantly and continuously. It demonstrates a reliable and accurate approach to study tree water use in changing environment. In this paper, the methods of scaling sapflow from tree to stand are firstly summarized, then key research progress on tree/stand water use in response to environmental changes by sapflow measurements is reviewed, coving: (1) Effects of elevated CO2 concentration on tree/stand water use, stoma conductance and crown structure. Effects of environmental factors on tree/stand water use under elevated CO2 concentration. (2) Response patterns of tree transpiration to rainfall event, stand transpiration response to water stress through the throughfall exclusion experiments (3) Physiological meanings of stem water storage. Sapflow techniques will be still the main methods in studying plant water relationship in future for scientists due to their simplicity, high accuracy and reliability, and relatively low cost.