Characteristics and modelling of canopy conductance and transpiration of Platycladus orientalis (L.) Franco in Loess Plateau of China

Abstract

Estimating plant water use is an important step in assessing the effects of increasing vegetation cultivation on the hydrological cycle especially in arid and semi-arid regions. In this study, meteorological measurements combined with sap flow techniques provided a low-cost option to study the canopy physiological transpiration of Platycladus orientalis response to environmental factors on a continuous basis. Canopy transpiration (E c) was measured by thermal dissipation method of Granier, and canopy conductance (g c) was calculated by inverting the Penman-Monteith equation. The results showed that the transpiration of P. orientalis was strongly controlled by stomatal conductance, and g c was a comprehensive and compounded environmental variable. An improved Jarvis-type model, based on a series of environmental control functions, explained 85% of the variation observed in g c. Cross validation showed that this model provided good predictions of canopy conductance and 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. © 2011 Academic Journals.