Abstract
The goal of the study was to determine circadian movements of silver birch (Petula Bendula) branches and foliage detected with terrestrial laser scanning (TLS). The study consisted of two geographically separate experiments conducted in Finland and in Austria. Both experiments were carried out at the same time of the year and under similar outdoor conditions. Experiments consisted of 14 (Finland) and 77 (Austria) individual laser scans taken between sunset and sunrise. The resulting point clouds were used in creating a time series of branch movements. In the Finnish data, the vertical movement of the whole tree crown was monitored due to low volumetric point density. In the Austrian data, movements of manually selected representative points on branches were monitored. The movements were monitored from dusk until morning hours in order to avoid daytime wind effects. The results indicated that height deciles of the Finnish birch crown had vertical movements between -10.0 and 5.0 cm compared to the situation at sunset. In the Austrian data, the maximum detected representative point movement was 10.0 cm. The temporal development of the movements followed a highly similar pattern in both experiments, with the maximum movements occurring about an hour and a half before (Austria) or around (Finland) sunrise. The results demonstrate the potential of terrestrial laser scanning measurements in support of chronobiology.
Highlights
Terrestrial laser scanners have gone through rapid development during the past 10 years (Dassot et al, 2011)
The study scope was limited to analysis and quantification of the geometric movements
Possible mechanisms contributing to the branch and crown movement may be related to plant water balance
Summary
Terrestrial laser scanners have gone through rapid development during the past 10 years (Dassot et al, 2011) They produce accurate 3D point clouds of target objects often down to millimeter resolution. In addition to structural modeling and scene mapping, terrestrial laser scanning (TLS) data are widely used in engineering applications to monitor possible changes in the targeted objects or in a target area. Quantifying Birch Branch Displacement by TLS applications These include geodynamic processes such as landslide detection and monitoring (Travelletti et al, 2008; Ghuffar et al, 2013) and morphodynamic changes in coastal beaches (Lindenbergh et al, 2011), thermal karst formations (Barnhart and Crosby, 2013), or in riversides (Milan et al, 2007; Vaaja et al, 2011; Saarinen et al, 2013). TLS is being actively used in static forest and forest parameter mapping (Hopkinson et al, 2004; Moskal and Zheng, 2012; Liang, 2013), tree modeling (Fleck et al, 2004; Hosoi and Omasa, 2006; Bucksch and Fleck, 2011; Eysn et al, 2013; Raumonen et al, 2013), and in estimating forest biomass (e.g., Kaasalainen et al, 2014)
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