International Journal of Applied Earth Observations and Geoinformation (Jul 2024)
Root plates of uprooted trees − Automatic detection and biotransport estimation using LiDAR data and field mapping
Abstract
The availability of LiDAR data (including open-source data), combined with specialized algorithms, allows the use of these data to automatically detect landforms, vegetation and other objects. LiDAR point clouds have been frequently applied for the detection and evaluation of living trees but never for root plates of uprooted trees. However, tree uprooting is one of the most important biotic-abiotic interactions in temperate forests. This process leads to the formation of root plates, i.e., microrelief forms consisting of undecomposed tree root systems and the attached soil and rock particles. Root plates are involved in biotransport, i.e., the movement of soil and rock material by living organisms. The objective of this study was to develop an automatic method for root plate detection and volume (and thus biotransport) estimation based on LiDAR data. The study area included three Norway spruce-dominated plots located in two national parks in the Polish Carpathians. For validation, the author mapped the root plates using a GNSS receiver and measured their dimensions. We created the differential model presenting the height of root plates, fallen trunks, and dense understory vegetation by interpolating the last returns with a normalized height < 2 m. We automatically extracted the root plate locations and computed their volume using three ways of estimation. The method was built in R. Depending on the study plot, the root plate detection rates ranged from 70.3 % to 79.1 %. For different ways of estimation, the mean root plate volume varied in a range of 2.2–3.35 m3, while the mean biotransport reached 176.1–268.3 m3/ha. The method offers the best results for LiDAR data with a minimal density of 8 pts/m2. We recommend using this method for 1) protected Norway spruce stands and 2) windthrows with no or few young conifers. The method can be applied to 1) assess the amount and spatial distribution of root plates and 2) determine the degree of soil disturbance and transport of soil material. Applying point cloud data to investigate the effects of tree uprooting can improve the understanding of the scale and course of different environmental processes related to this phenomenon. In future studies, field root plate measurements and volume estimations could be independently confirmed by using LiDAR data and the method presented in this study.
