Veli-Pekka Ikonen

Modelling the structural growth of Scots pine with implications for wood quality

Abstract A model for simulating the growth and development of individual Scots pines ( Pinus sylvestris L.) is presented in terms of three-dimensional structure of the tree as determined by the influence of local light conditions on branch growth, with implications for the properties of the wood. The basic computational unit for structural growth is the shoot. Each shoot produces new shoots with dimensions related to the amount of direct and diffuse radiation intercepted in the parent shoot and supplied by other shoots in the crown. The calculation procedure utilises the spatial distribution of shoots produced by the growth process (location, azimuth, inclination), and the structure of the shoots determined in terms of the density, angle and length of the needles. The allocation of tree biomass amongst the needles, branches and stem is basically related to the allocation of the growth of forming shoots between the shoot axis and the needles under the control of the hierarchical position of the parent shoot, branch age and the height of the tree. The growth, death and pruning-off of shoots and branches are modelled over the life span of the tree using time step of 1 year, taking special care to identify the location of green and dead knots in the wood. The properties of the stem are further described in terms of the stem form, wood density and heartwood, which are modelled in the context of the overall growth of the tree. The computation produces the three-dimensional distribution of ring widths, density and heartwood in the stem, i.e. from the pith to stem surface and from the stem base to tree top. The model produces quite a realistic crown and stem structure for simulated Scots pines regardless of the life span of the tree. Furthermore, the model is capable of calculating quite accurately, e.g. average wood density values for any section of wood within a tree.

Linking tree stem properties of Scots pine (Pinus sylvestris L.) to sawn timber properties through simulated sawing

Abstract We demonstrate how tree stem properties may be linked to the properties of sawn timber through simulation of the structural growth of the tree and of the sawing of the stem into pieces subjected to quality grading. In this context, the growth and development of individual Scots pines ( Pinus sylvestris L.) is presented in terms of the three-dimensional structure of the tree crown as determined by the influence of local light conditions on branch growth, with implications for the distribution of the properties of the stem and wood such as stem form and knots. The three-dimensional distribution of these properties allows one to saw the stem into logs and further into sawn pieces which can be graded based on quality. The part of the stem to be cut into logs is defined by the height of the stump (felling height) and the diameter of a stem fulfilling the minimum top diameter for a log acceptable for sawing. The stems are characterised by means of the number of logs obtainable for sawing, the length of the logs, the top and butt diameters of the logs, their volume and their taper. The wood is characterised for sawing mainly in terms of the occurrence of knots and their size and quality (sound, dead). The sawing algorithm checks the knots in terms of diameter and quality and calculates the grade and value of each piece. This procedure is repeated log by log, and a summary of the sawing is made covering the whole stand, with a report on the total yield and value of the sawn timber obtained from each stand. The performance of the sawing simulator was demonstrated with the example computations on sawing for Scots pine trees. As a result, the quality of sawn timber was found higher in an unthinned stand than in the thinned stands. On the other hand, the sawing yield from individual 100-year-old tree from the thinned stand was larger than from a tree of the same age in an unthinned stand, because of its larger size.

Effects of climate change on optimised stand management in the boreal forests of central Finland

In boreal conditions, climate change is expected to increase mean annual temperature and precipitation, increasing forest growth and productivity in managed forests. In this study, we aimed at finding out how climate change affects the optimal management of Scots pine-, Norway spruce- and silver birch-dominated stands on sites of varying fertility (high-herb, mesic and sub-xeric sites) in the boreal forests of central Finland. The objective function was to maximise net present value (NPV), considering the future incomes from timber sales and costs of forest operations. The results showed that under the gradually changing climate, the optimised management schedules differed from those observed under the current climate. In Norway spruce- and birch-dominated stands, cuttings were done earlier under the changing climate than under the current climate, while in Scots pine-dominated stands they were delayed under the changing climate. The optimised management schedules also varied, depending on tree species and site fertility types. Under the changing climate, both timber production and NPV increased compared to the current climate, regardless of species and site fertility type.

Modelling the distribution of diameter growth along the stem in Scots pine

This paper presents an empirical model for the distribution of diameter growth along the stem in Scots pine (Pinus sylvestris L.) and for the consequent stem form over time. First, the distribution of annual mass growth in the stem is determined as a function of the total annual growth in stem mass, current stem mass and the distribution of the latter along the stem. Second, the distribution of diameter growth is obtained by converting the fraction of annual growth in the stem mass at a given height in the stem into the thickness of the annual ring at the same height. Application of the model to Scots pine data sets including both young and mature trees not used in parameter estimation showed that the model was capable of reconstructing the distribution of diameter growth from the stem butt to the apex and from the pith to the stem surface at any height in the stem in both young and mature trees. The resulting empirical model was also linked to a physiological, process-based model in order to study its performance in a simulated stand. Simulations representing trees grown in unthinned and thinned Scots pine stands with trees of different status (from dominant to suppressed) showed that the response in tree growth to thinning in terms of the distribution of diameter growth along the stem was quite realistic relative to measured data.

Modeling the SAR response of pine forest in Southern Finland

Ground data, biologically accurate model trees, an optical mosaic, a ground digital elevation model, and a top surface model for a forested site at Tuusula, Southern Finland have been used to construct a natural model forest. Model calculations include the SAR imaging process and predict SAR image structure. CARABAS low frequency SAR images of the forested site are compared with SAR image calculations, and fractional Brownian motion based texture images. Simulated intensities and textures agree well with observation.

Effects of using certain tree species in forest regeneration on volume growth, timber yield, and carbon stock of boreal forests in Finland under different CMIP5 projections

We studied how the use of certain tree species in forest regeneration affected the volume growth, timber yield, and carbon stock of boreal forests in Finland under the current climate (1981–2010) and recent-generation global climate model (GCM) predictions (i.e., multi-model means and individual GCMs of CMIP5), using the representative concentration pathways RCP4.5 and RCP8.5 over the period 2010–2099. Forest ecosystem model simulations were conducted on upland national forest inventory plots throughout Finland. In a baseline management regime, forest regeneration was performed by planting the same tree species that was dominant before the final cut. In alternative management regimes, either Scots pine, Norway spruce, or silver birch were planted on medium-fertility sites. Other management actions over rotation were done as in a baseline management. Compared to baseline management, an increased planting of birch resulted in relative sense highest increase in the volume growth, timber yield, and carbon stock in forests in the south, especially under severe climate projections (e.g., multi-model mean RCP8.5, and GCMs such as HadGEM2-ES RCP8.5 and GFDL-CM3 RCP8.5). This situation was opposite for Norway spruce. In the north, the volume growth, timber yield, and carbon stock of forests increased the most under severe climate projections (e.g., multi-model mean RCP8.5 and CNRM-CM5 RCP8.5), regardless of tree species preference. The magnitude of the climate change impacts depended largely on the geographical region and the severity of the climate projection. Increasing the cultivation of birch and Scots pine, as opposed to Norway spruce, could be recommended for the south. In the north, all three species could be cultivated, regardless of the severity of climate change.

Ensiharvennuksen ja puun metsikköaseman vaikutus männyn sädekasvuun ja puuaineen tiheyteen

Seloste artikkelista: Peltola, H., Kilpelainen, A., Sauvala, K., Raisanen, T. & Ikonen, V.-P. 2007. Effects of early thinning regime and tree status on the radial growth and wood density of Scots pine. Silva Fennica 4 (3): 489-505.