A mathematical model linking tree sap flow dynamics to daily stem diameter fluctuations and radial stem growth

Abstract

To date, models for simulating sap flow dynamics in individual trees with a direct link to stem diameter variation include only the diameter fluctuation driven by a change in stem water storage. This paper reports results obtained with a comprehensive flow and storage model using whole-tree leaf transpiration as the only input variable. The model includes radial stem growth based on Lockhart's equation for irreversible cell expansion. It was demonstrated that including growth is essential to obtaining good simulation results. To model sap flow dynamics, capacitance of storage tissues was assumed either constant (i.e., electrical analogue approach) or variable and dependent on the water content of the respective storage tissue (i.e., hydraulic system approach). These approaches resulted in different shapes for the desorption curve used to calculate the capacitance of storage tissues. Comparison of these methods allowed detection of specific differences in model simulation of sap flow at the stem base (F(stem)) and stem diameter variation (D). Sensitivity analysis was performed to select a limited subset of identifiable parameters driving most of the variability in model predictions of F(stem) and D Both the electrical analogue and the hydraulic system approach for the flow and storage model were successfully calibrated and validated for the case of a young beech tree (Fagus sylvatica L.). Use of an objective model selection criterion revealed that the flow and storage model based on the electrical analogue approach yielded better predictions.

Biomass productivity and water use relation in short rotation poplar coppice (Populus nigra x P. maximowiczii) in the conditions of Czech Moravian Highlands

“…Moreover, e.g. Hsiao and Acevado (1974), Hinckley and Lassoie (1981), Barbaroux and Breda (2002), Steppe et al (2006), Zweifel et al (2006) explain that during drier periods when the stem water defi cit occurs, new cells which are still created do not immediately expand, but a release of the low pressure conditions in the cambium suddenly enlarges the already existing cells to their mature sizes. This means that, within a certain period of time and for a range of water defi cit, growth is not inhibited but just delayed.…”

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

“…A process-based description of these processes (i.e. Sperry et al, 1998;Steppe et al, 2006) is being tested and should reduce the effect of the tuning parameter and eventually allow its removal from the model. For the time being, the modulator m ψ was tuned manually against the species distribution map to obtain a match between the simulated and observed species distributions.…”

The Forecasting Plant Trend That Is Appropriate in the Storage of Carbon Dioxide to Fight Global Warming in the Area of Nonthaburi

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