Articles containing the keyword 'geometry'

A method for the measurement of the three-dimensional (3D) architecture of trees was applied to describe two 20-year-old walnut trees, one of them is a timber tree while the other is a fruit tree. The method works at the shoot level and simultaneously describes the plant topology, the plant geometry and the shoot morphology. The method uses a 3D digitiser (3SPACE® FASTRAK®, Polhemus Inc.) associated with software DiplAmi designed for digitiser control and data acquisition management. Plant images may be reconstructed from the data set by using the ray tracing software POV-Ray. Visual comparison between photographs of the walnut trees and images synthesised from digitising was satisfactory. Distribution of basal shoot diameter, as well as leaf area and fruit distributions for both the timber and the fruit tree were non-uniformly distributed in the crown volume. Gradients were likely to be related to the light distribution within the tree. This is in agreement with previous experimental results on several tree species, and also with the predictions of tree architecture models based on light-vegetation interactions.

• Sinoquet, E-mail: hs@mm.unknown
• Godin, E-mail: cg@mm.unknown
• Rivet, E-mail: pr@mm.unknown

The problems caused by the temporal and spatial microvariation in irradiance during field measurements of photosynthesis are studied. It is concluded on the basis of variation analyses based on irradiance data measured in a Scots pine (Pinus sylvestris L.) stand that the microvariation should be measured by integrating it over the measurement time and space.

However, the curvlinearity of the light response of photosynthesis results in biased estimates when linear integration (mean irradiance) is used. The significance of the bias is examined using a simulation technique on irradiance material. Whether the actual integral of photosynthesis can be approximated with mathematical method is next studied. The method gave satisfactory results only for a low curvature response, but the latter method was applicable also to the high curvature response. However, both methods presuppose that the mean and variance are known. Measurement of the variance is based on integration of the second power.

A new method, where the nonlinearity problem is avoided, is presented to measure fluctuation of the irradiance. The method enables the shoot geometry to be taken into account and it is also applicable to transpiration studies.

The PDF includes a summary in Finnish.

• Smolander, E-mail: hs@mm.unknown

In this paper, we present a new methodology that directly extracts the geometry of woody features (wood and bark) and foliage from 3D data originating from terrestrial laser scans. Our goal was to enhance the precision of radiative transfer models for modelling tree shading by using highly resolved 3D tree models. The approach was tested on a single apple tree (Malus domestica (Suckow) Borkh.) in a peri-urban setting and was validated by utilising an open-source radiative transfer model and comparing the simulation output with in-situ measurements of photosynthetically active radiation (PAR) as well as simulations utilizing turbid voxels of 0.2 m and 1 m edge length. The in-situ measurements of 60 PAR sensors showed a correlation coefficient (r) of 0.92 with the simulated light intensities for the reconstructed polygons which was higher than for the voxel-based approaches (0.2 m:  r = 0.85, 1 m: r = 0.73). We were able to demonstrate that our approach effectively simulates light extinction through the canopy. This innovative method has the potential to easily provide detailed insights into high resolution radiation patterns within forests, which are connected to multiple ecosystem functions like species and habitat diversity.

• Frey, Chair of Forest Growth and Dendroecology, University of Freiburg, Freiburg im Breisgau, Tennenbacher Str. 4, 79106 Freiburg, Germany https://orcid.org/0000-0001-7895-702X E-mail: julian.frey@wwd.uni-freiburg.de
• Schindler, Chair of Forest Growth and Dendroecology, University of Freiburg, Freiburg im Breisgau, Tennenbacher Str. 4, 79106 Freiburg, Germany https://orcid.org/0000-0003-2972-1920 E-mail: zoe.schindler@wwd.uni-freiburg.de
• McClatchy, Chair of Forest Growth and Dendroecology, University of Freiburg, Freiburg im Breisgau, Tennenbacher Str. 4, 79106 Freiburg, Germany E-mail: patrickjmcclatchy@gmail.com
• Morhart, Chair of Forest Growth and Dendroecology, University of Freiburg, Freiburg im Breisgau, Tennenbacher Str. 4, 79106 Freiburg, Germany https://orcid.org/0000-0003-1874-5011 E-mail: christopher.morhart@wwd.uni-freiburg.de
• Larysch, Chair of Forest Growth and Dendroecology, University of Freiburg, Freiburg im Breisgau, Tennenbacher Str. 4, 79106 Freiburg, Germany https://orcid.org/0000-0002-1191-5770 E-mail: elena.larysch@wwd.uni-freiburg.de
• Seifert, Chair of Forest Growth and Dendroecology, University of Freiburg, Freiburg im Breisgau, Tennenbacher Str. 4, 79106 Freiburg, Germany; Department of Forest and Wood Science, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa https://orcid.org/0000-0002-9611-6272 E-mail: thomas.seifert@wwd.uni-freiburg.de