Christine Deleuze, François Houllier. (1997). A transport model for tree ring width. Silva Fennica vol. 31 no. 3 article id 5622. https://doi.org/10.14214/sf.a8523

Keywords: carbon; optimization; tree growth; stem taper; allocation; environment; wood distribution; functional balance; Münch’s theory; partitioning; process-model; reaction-diffusion; Thornley's model; silvicultural treatments

Abstract | View details | Full text in PDF | Author Info

Process-based tree growth models are recognized to be flexible tools which are valuable for investigating tree growth in relation to changing environment or silvicultural treatments. In the context of forestry, we address two key modelling problems: allocation of growth which determines total wood production, and distribution of wood along the stem which determines stem form and wood quality. Growth allocation and distribution are the outcome of carbon translocation, which may be described by the Munch theory. We propose a simpler gradient process to describe the carbon distribution in the phloem of conifers. This model is a reformulation of a carbon diffusion-like process proposed by Thornley in 1972. By taking into account the continuity of the cambium along the stem, we obtain a one-dimensional reaction-diffusion model which describes both growth allocation between foliage, stem and roots, and growth distribution along the stem. Distribution of wood along the stem is then regarded as an allocation process at a smaller scale. A preliminary sensitivity analysis is presented. The model predicts a strong relationship between morphology and foliage-root allocation. It also suggests how empirical data, such as stem analysis, could be used to calibrate and validate allocation rules in process-based growth models.

Deleuze, E-mail: cd@mm.unknown
Houllier, E-mail: fh@mm.unknown

article id 5470, category Article

Juha Heiskanen, Jukka Laitinen. (1992). A measurement system for determining temperature, water potential and aeration of growth medium. Silva Fennica vol. 26 no. 1 article id 5470. https://doi.org/10.14214/sf.a15629

Keywords: peat; diffusion; measuring methods; matric potential; oxygen; sensors; growth media

Abstract | View details | Full text in PDF | Author Info

A measurement system developed for the parallel and real-time measurement of temperature, matric potential and oxygen diffusion rate (ODR) of a growth medium was assessed. The system consisted of a portable computer, a datalogger, temperature sensors, tensiometers and an ODR-meter with Pt-sensors.

For the measurements, proper sensor contact with the growth medium was needed. For matric potential measurement, appropriate shape and material of the tensiometer tips should be selected for different measurement purposes. The determination of oxygen diffusion rate is based on single, non-continuous measurements. The ODR-measurement required special care with the insertion and handling of the electrodes and selection of applied voltage. The ODR-measurement of a coarse peat medium was applicable only at matric potentials > -5 kPa. This measurement system was shown to be useful and suitable for accurate determination of thermal-, water- and aeration conditions of a growth medium under greenhouse conditions.

The PDF includes an abstract in Finnish.

Heiskanen, E-mail: jh@mm.unknown
Laitinen, E-mail: jl@mm.unknown

Category : Research article

article id 652, category Research article

M. J. Youngman, G. D. Kulasiri, I. M. Woodhead, G. D. Buchan. (1999). Use of combined constant rate and diffusion model to simulate kiln-drying of Pinus radiata timber. Silva Fennica vol. 33 no. 4 article id 652. https://doi.org/10.14214/sf.652

Keywords: simulation; timber drying; diffusion; constant drying-rate

Abstract | View details | Full text in PDF | Author Info

This paper presents the use of a combined constant drying-rate and diffusion model to simulate the drying of Pinus radiata timber under kiln-drying conditions. The constant drying-rate and diffusion coefficients of the model, which control the drying rate of individual pieces of timber, were determined from calibrating the model against the experimental drying curves obtained under the kiln-drying conditions. The experimental drying curves were obtained from the gravimetric measurements of the moisture content of timber during kiln drying. Statistical relationships were developed for the constant drying-rate and the diffusion coefficients of the model as functions of kiln temperature and the dry basis density of timber. To determine the effects of variability of timber, a simulation scheme was developed based on the model, the probability distribution of the density of timber, the equations for the constant drying-rate coefficient and the diffusion coefficient. The model and the associated simulation method provides a simple way to estimate the drying time of a stack of timber using parameters determined from experimental results for the specific timber kiln.

Youngman, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand E-mail: mjy@nn.nz
Kulasiri, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand E-mail: kulasird@tui.lincoln.ac.nz
Woodhead, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand E-mail: imw@nn.nz
Buchan, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand E-mail: gdb@nn.nz

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