Articles containing the keyword 'shape'

There exists an algorithm for construction interpolating quadratic splines which preserves the monotony of the data. The taper curves formed with this algorithm, QO-splines, have many good qualities when a sufficient number of measured diameters of a tree is available. In fact, they may even be superior to certain shape preserving taper curves, MR-splines. This algorithm can be modified to preserve also the shape of the data. In the present paper, the quality of taper curves constructed by a new shape preserving from of the algorithm is examined. For this purpose, taper curves are formed for different sets of measurements and their properties are compared with the ones of QO-splines and MR-splines. The results indicate that these new shape-preserving taper curves are in general better than QO-splines and MR-splines even if the differences may be small in many cases. The superiority is the clearer the less measurements are available.

The PDF includes an abstract in Finnish.

• Lahtinen, E-mail: al@mm.unknown

The shape of Scots pine (Pinus sylvestris L.) knots close to the pith of butt logs was investigated. 1,100 knots were split in a vertical direction, and their shape was measured. Knot diameter and branch angle were calculated at a distance of 40 mm from the pith of the stem. The mean diameter of all the knots in the material was 14 mm, and the branch angle 70°. Regression analysis was used to devise a formula for predicting branch angle on the basis of knot diameter. Knot size and branch angle were negatively correlated. Especially the shape of larger knots was curved. Knots achieved their maximum diameter at distance of 4–5 cm from the stem pith. The branch wood was almost completely situated above the formation point of the branch.

The PDF includes an abstract in Finnish.

• Pietilä, E-mail: jp@mm.unknown

Finnish tree species have adapted differently to heavy snow loads that occur especially in fell areas in Kuusamo and Salla as well as Maanselkä area in Sotkamo and Rautavaara in Northern Finland. Norway spruce (Picea abies Karst. L) is adapted better than Scots pine (Pinus sylvestris L.). The aim of this study was to investigate how crown and stem form of Norway spruce in the snow damage area of Maanselkä area differ from other areas in the same region.  

Relatively broad crown at the base of the stem, quickly tapering crown and narrow and even upper crown were typical for trees growing in the snow damaged areas. The higher the altitude is, the stronger tapering the crown is. The tapering begins usually in a height of 4-5 meters. Even the stem diameter begins to taper strongly at this height. In the areas where heavy snow does not cause snow damage, top of crown is broader. Also, in the snow damage areas the damaged trees seem to have broader crown shape than the trees with little damages.  

Height of the trees decreases in the snow damage areas compared to forests in lower altitudes, which can be caused both by wind and snow load. 

The article includes a German summary. 

• Mikola, E-mail: pm@mm.unknown

This study examines the alternatives to include crown base height (CBH) predictions in operational forest inventories based on airborne laser scanning (ALS) data. We studied 265 field sample plots in a strongly pine-dominated area in northeastern Finland. The CBH prediction alternatives used area-based metrics of sparse ALS data to produce this attribute by means of: 1) Tree-level imputation based on the k-nearest neighbor (k-nn) method and full field-measured tree lists including CBH observations as reference data; 2) Tree-level mixed-effects model (LME) prediction based on tree diameter (DBH) and height and ALS metrics as predictors of the models; 3) Plot-level prediction based on analyzing the computational geometry and topology of the ALS point clouds; and 4) Plot-level regression analysis using average CBH observations of the plots for model fitting. The results showed that all of the methods predicted CBH with an accuracy of 1–1.5 m. The plot-level regression model was the most accurate alternative, although alternatives producing tree-level information may be more interesting for inventories aiming at forest management planning. For this purpose, k-nn approach is promising and it only requires that field measurements of CBH is added to the tree lists used as reference data. Alternatively, the LME-approach produced good results especially in the case of dominant trees.

• Maltamo, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: matti.maltamo@uef.fi
• Karjalainen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: tomimkarjalainen@gmail.com
• Repola, Natural Resources Institute of Finland (Luke), Natural resources, Eteläranta 55, FI-96300 Rovaniemi, Finland E-mail: jaakko.repola@luke.fi
• Vauhkonen, Natural Resources Institute of Finland (Luke), Bioeconomy and environment, Yliopistokatu 6, 80100 Joensuu, Finland E-mail: jari.vauhkonen@luke.fi

Accurate assessment of canopy structure is crucial in studying plant-environment interactions. The advancement of functional-structural plant models (FSPM), which incorporate the 3D structure of individual plants, increases the need for a method for accurate mathematical descriptions of leaf shape. A model was developed as an improvement of an existing leaf shape algorithm to describe a large variety of leaf shapes. Modelling accuracy was evaluated using a spatial segmentation method and shape differences were assessed using principal component analysis (PCA) on the optimised parameters. Furthermore, a method is presented to calculate the mean shape of a dataset, intended for obtaining a representative shape for modelling purposes. The presented model is able to accurately capture a large range of single, entire leaf shapes. PCA illustrated the interpretability of the parameter values and allowed evaluation of shape differences. The model parameters allow straightforward digital reconstruction of leaf shapes for modelling purposes such as FSPMs.

• Coussement, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium; Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium E-mail: jonas.coussement@ilvo.vlaanderen.be
• Steppe, Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium E-mail: kathy.steppe@ugent.be
• Lootens, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium E-mail: peter.lootens@ilvo.vlaanderen.be
• Roldán-Ruiz, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium; Department of Plant Biotechnology and Bioinformatics, Faculty of Sciences, Ghent University, Technologiepark Zwijnaarde 927, B-9052 Zwijnaarde, Belgium E-mail: isabel.roldan-ruiz@ilvo.vlaanderen.be
• De Swaef, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium E-mail: tom.deswaef@ilvo.vlaanderen.be

Short day (SD) treatment is used as a dormancy induction in forest tree seedling nurseries in the boreal forest zone. However, SD treatment has caused early bud burst in the following spring, which may expose the seedlings to spring frosts. Because the mechanisms affecting earlier bud burst in SD treated seedlings are not fully understood yet, here we have studied the effect of SD treatment on the structure of buds in Norway spruce [Picea abies (L.) Karst.] seedlings. Seedlings were exposed to SD treatments or natural (CTRL) light and photoperiod in July in a nursery in Central Finland. The experiments included two lots of seedlings over two summers and the analyses were done under a stereo microscope. SD treatment advanced initiation of bud scales and formation of needle primordia, and thus the formation period was shorter in CTRL seedlings. In mature buds, no differences in primordial shoots were found between the treatments, whereas notable differences were found in bud scales. The SD buds had fewer and shorter bud scales than the CTRL buds. This led to significantly shorter bud scale complex and, consequently, to shorter buds in SD than in CTRL seedlings. Buds and needles matured earlier in SD treated seedlings. In the following spring, the primordial shoots started to elongate in both treatments around mid-May, when the SD buds started to break down, whereas CTRL buds started to break down in late May. The fewer number and shorter height of protective bud scales may expose buds to harsh winter temperatures and early loss of scales may predispose the SD buds to spring frosts.

• Luoranen, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, Juntintie 154, FI-77600 Suonenjoki, Finland E-mail: jaana.luoranen@luke.fi
• Sutinen, E-mail: sirusuti@gmail.com

• Ferrarese, College of Forestry and Conservation, The University of Montana, Missoula, MT, USA; (present) Center for the Environmental Management of Military Lands, 1490 Campus Delivery, Colorado State University, Fort Collins, CO 80523, USA E-mail: jena.ferrarese@colostate.edu
• Affleck, College of Forestry and Conservation, University of Montana, Missoula, MT, USA E-mail: david.affleck@cfc.umt.edu
• Seielstad, College of Forestry and Conservation, University of Montana, Missoula, MT, USA E-mail: carl.seielstad@firecenter.umt.edu

• Henke, Department Ecoinformatics, Biometrics & Forest Growth, University of Göttingen, 37077 Göttingen, Germany E-mail: mhenke@uni-goettingen.de
• Huckemann, Institute of Mathematical Stochastics, University of Göttingen, 37077 Göttingen, Germany E-mail: huckeman@math.uni-goettingen.de
• Kurth, Department Ecoinformatics, Biometrics & Forest Growth, University of Göttingen, 37077 Göttingen, Germany E-mail: wk@informatik.uni-goettingen.de
• Sloboda, Department Ecoinformatics, Biometrics & Forest Growth, University of Göttingen, 37077 Göttingen, Germany E-mail: bslobod@web.de

• Maltamo, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: matti.maltamo@joensuu.fi
• Peuhkurinen, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: jp@nn.fi
• Malinen, Finnish Forest Research Institute, Joensuu Research Unit, FI-80101 Joensuu, Finland E-mail: jm@nn.fi
• Vauhkonen, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: jv@nn.fi
• Packalén, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: pp@nn.fi
• Tokola, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: tt@nn.fi