Tree Motion. Following the wind-induced swaying of arboreous individual using a GNSS receiver

Climate-induced stresses, more than in the past, expose trees to hazards possibly compromising their stability, with serious risk for people, objects, structures and infrastructures. In order to prevent trees falling phenomena, a constant improvement of the knowledge of relations between trees and meteorological events (trees-wind in particular) is crucial. Any new technology able to support research and monitoring in this direction must therefore be studied, tested, and finally adopted in order to create an infrastructure that would bring indisputable advantages from a social, economic and environmental point of view. The aim of this study is to test the applicability of GNSS receivers for monitoring wind-associated tree movements. The case study reported here refers to an experimental analysis carried out on an Italian stone pine (Pinus pinea L.). The analysis was carried out by applying a single-frequency GNSS receiver (an u-blox M6 evaluation kit available on the market at 300$) at the top of the tree and evaluating the results obtained in term of velocities and positions. Then, values obtained were correlated with wind characteristics by a sonic anemometer installed very close to the pine tree (within 15 meters), in order to independently record the impacting wind fields (velocity, direction). This allowed us to study the correlation between the wind velocity (cause) and tree movements (effect). Statistic outputs evaluation provides very promising results, showing the capability of this instrumental solution in the analysis of movement patterns. The study, indeed evidenced that accuracy of measurements and their relative errors are enough for the research purposes.