Geophysics-based landslide zonation explains spatial variability in tree-ring growth disturbances

Complex landslides contain internally heterogeneous zones that may respond differently to reactivation, complicating tree-ring based chronologies of slope activity. This study combines dendrogeomorphological analysis with electrical resistivity tomography (ERT) to test whether geophysics-based zonation could explain the spatial variability of tree-ring disturbances within a large complex landslide. ERT profiles and geomorphological mapping delineated three mechanically distinct zones: a downslope shallow-landslide sector ( S zone ), a moisture-rich gap infilled by weakly consolidated material ( G zone ), and an adjacent compact block with tension cracks ( B zone ). In total, 200 Norway spruce ( Picea abies (L.) H. Karst) were analysed for reaction wood (RW) and abrupt growth suppression (GS). RW intensity was quantified for each affected ring and GS classified by relative ring-width reduction. RW clearly dominates across the landslide. The S zone shows the highest stem inclinations and RW intensities, indicating enhanced shallow deformation, whereas RW duration is similar among zones. GS occurs everywhere but is proportionally most frequent in the B zone . Correlation analyses show that in the S and G zones , RW intensity and duration relate significantly to stem inclination, while no significant relationships appear in the B zone . These results demonstrate that internal landslide heterogeneity, as delineate by ERT, is reflected in tree-ring responses. Geophysics-based zonation offers an effective framework for interpreting growth disturbances and improves dendrogeomorphic reconstructions of complex slope movements. • Geophysics-based zonation reveals three contrasting landslide zones. • Combining geophysics and tree rings reveals internal landslide variability. • Reaction wood dominates in all three zones. • Growth suppression is dependent on the tree position.