Drone-borne Ground-penetrating Radar time-lapse mapping reveals spatiotemporal moisture dynamics in peatlands

The moisture status of peatlands is an important factor, because it directly affects carbon dynamics. It is thus critical to characterize and understand the peatland moisture status, and to monitor its spatial and temporal variations. This study aims to evaluate the potential of drone-borne Ground-penetrating radar (GPR), used in combination with full-wave inversion, to study the spatial and temporal variability of peatland root-zone moisture. Following this, we aim to assess its benefits for peatland restoration applications. Our study site is a 4.5 ha peatland, located in the Belgian Hautes Fagnes, which was previously degraded by forestry activities. We conducted Ground-penetrating radar measurements every 2 to 4 weeks from May 2023 to September 2024, allowing us to produce 19 peatland soil moisture maps with a 5-meter resolution. Additionally, we collected reference soil moisture data using ground-based probes to enable comparison with the GPR results. Regarding temporal variability, the overall correlation between the GPR and the ground-based probes is 0.71, indicating that this method effectively captures overall moisture dynamics across the entire study site. In contrast, the spatial comparison between the GPR and the ground-based probes showed a lower correlation (0.23). This is partly caused by the high micro-variability of soil moisture, the spatial mismatch between the measurement methods, and their different characterization areas and depths. However, we show that the spatial data contained useful information content, when applying a spatial clustering analysis to produce maps of homogeneous moisture classes over the study site. Indeed, there was a good alignment of these clusters with other specific site characteristics, such as peat depth, surface temperature and vegetation composition. This clustering could be used to support the planning of restoration efforts. Finally, this study introduces a new approach for peatland root-zone moisture mapping and monitoring, and shows potential to guide and monitor peatland restoration strategies.