CANOPY TRANSPIRATION RESPONSE TO ENVIRONMENTAL VARIATIONS IN PLATYCLADUS ORIENTALIS: PROPERTIES AND MODELLING

Regrowth of tall, dense forests consumes more water, with the result that catchment yield may decline and even soil desiccation occurred especially in the semi-arid Loess Plateau of China. In this study, meteorological measurements combined with sap flow techniques provided a low-cost option to study the rates of water uptake by individual trees of Platycladus orientalis response to environmental factors on a continuous basis. A series of environmental control functions: vapour pressure deficit, solar radiation and air temperature were used to characterize canopy transpiration (E-c). A Jarvis-type model, modified to directly estimate the E-c rather than canopy conductance, explained 89% of the variation observed in E-c. Cross validation shows that this model provided good predictions of canopy transpiration for P. orientalis. Such a methodology offers a reasonable estimation of water use in the determination of water balance for land water resources planning, vegetation management and impact assessments of rehabilitation.