Drone-borne ground-penetrating radar reveals spatiotemporal moisture dynamics in peatland root zones

Peatlands are important ecosystems, providing essential ecological services, such as carbon storage and biodiversity support. However, they are endangered by degradation due to land use and climate change. Their moisture status is a key factor, as it substantially impacts carbon storage and decomposition. Therefore, it is essential to accurately characterize, map, and monitor peatland moisture. This study assessed the potential of drone-borne Ground-penetrating radar (GPR), combined with full-wave inversion, to study peatland moisture. We applied this technique to a peatland in the Belgian Hautes Fagnes previously degraded by reforestation. We conducted GPR measurements over 4.5 ha for one and a half years, producing 19 different peatland root-zone moisture maps at a 5 m resolution. Our results demonstrate that this method can track moisture changes over the study site, with an overall temporal correlation of 0.71 with ground-based moisture sensors, but is less reliable in nearly saturated areas. The spatial correlation with ground-based probes is lower (0.23), due to the high micro-variability of moisture and the use of kriging interpolation to generate maps, resulting in a spatial mismatch as GPR measurements were not collected directly above the probes. We applied statistical clustering techniques on the moisture maps to delineate homogeneous moisture classes that align well with other specific site characteristics (peat depth, vegetation types, Normalized Difference Water Index and surface temperature). This technique shows potential for planning and monitoring peatland restoration efforts and provides a new and valuable approach for peatland moisture studies to complement existing satellite- and other drone-based methods.