A high-resolution approach for the spatiotemporal analysis of forest canopy space using terrestrial laser scanning data

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Forest canopies and tree crown structures are of high ecological importance. Measuring canopies and crowns by direct inventory methods is time-consuming and of limited accuracy. High-resolution inventory tools, in particular terrestrial laser scanning (TLS), is able to overcome these limitations and obtain three-dimensional (3D) structural information about the canopy with a very high level of detail. The main objective of this study was to introduce a novel method to analyze spatiotemporal dynamics in canopy occupancy at the individual tree and local neighborhood level using high-resolution 3D TLS data. For the analyses, a voxel grid approach was applied. The tree crowns were modeled through the combination of two approaches: the encasement of all crown points with a 3D α-shape, which was then converted into a voxel grid, and the direct voxelization of the crown points. We show that canopy occupancy at individual tree level can be quantified as the crown volume occupied only by the respective tree or shared with neighboring trees. At the local neighborhood level, our method enables the precise determination of the extent of canopy space filling, the identification of tree–tree interactions, and the analysis of complementary space use. Using multitemporal TLS data recordings, this method allows the precise detection and quantification of changes in canopy occupancy through time. The method is applicable to a wide range of investigations in forest ecology research, including the study of tree diversity effects on forest productivity or growing space analyses for optimal tree growth. Due to the high accuracy of this novel method, it facilitates the precise analyses even of highly plastic individual tree crowns and, thus, the realistic representation of forest canopies. Moreover, our voxel grid framework is flexible enough to allow for the inclusion of further biotic and abiotic variables relevant to complex analyses of forest canopy dynamics.

Original languageEnglish
JournalEcology and Evolution
Issue number13
Pages (from-to)6800-6811
Number of pages12
Publication statusPublished - 07.2018

Bibliographical note

Funding Information:
This research was carried out as part of the BEF-China project financed by the German Research Foundation (DFG FOR 891/1-3, HA 5450/1-2, OH 198/2-3). We are grateful to all members of BEF-China for their support, to Moritz Hansen and Elisabeth Mohrdiek for their valuable assistance with the scanning, and to Simon Hein, Norman DD堀ring, and Inga Frehse for their support in the preprocessing tree extractions. Carsten Hess is grateful for the financial support provided by the Graduate School of the Leuphana University of Lüneburg.

Publisher Copyright:
© 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

    Research areas

  • Ecosystems Research - canopy packing, change detection, crown modeling, multitemporal coregistration, remote sensins, time series, voxel grid