Using a weighted Voronoi diagram for forest thinning proposals and skidding trail layouts for teak plantations in Thailand

Timber skidding is one of the many causes of destruction or damage to forest stands. Any sustainable forestry system requires a suitable skidding trail layout that minimises damage to trees and soils as well as economic losses. Imagery of six teak plantation plots in Thong Pha Phum was captured with a DJI Mavic Pro unmanned aerial vehicle and further processed with Agisoft Metashape software. Single trees could be distinguished in the canopy height model thus created, and understory trees for thinning from below were identified from a weighted Voronoi diagram. This approach does not include a field survey and therefore needs to include an assessment of the health and quality of the trees, but it can be considered as a basis for accelerating the process of marking trees for thinning. Rasterisation was applied to produce an estimate of tree density based on Kernel Density Estimation. Given the irregular spacing of the teak trees, a subjective approach was applied to plot a skidding trail layout, with the emphasis on shortening skidding distances and reducing potential damage to soils and remaining trees. This study could help to improve access to forest stands by improving the quality of skidding and reducing damage to standing trees and to the timber itself.