Spatiotemporal reconstruction of anthropogenically accelerated soil creep: Bâlea glacial valley, Făgăraş Mountains, Romanian Carpathians

• Evaluation of soil creep was performed on an anthropogenic slope. • 108 tree-ring series were obtained, and a 35-year chronology was constructed. • Creep is influenced by geology, slope, precipitation, and frosty cycles. • Presence of creep is indicated by young trees and their ’pistol-butted’ form. • Spatial pattern of creep-disturbed trees was tested using Moran’s I index. Soil creep is a slow gravitational process. It differs from other catastrophic slope processes such as landslides, snow avalanches, and rockfalls in its dynamics and character. However, it can significantly affect tree growth. Creep movements can be analyzed based on the tree rings. This study analyzed the dynamics and spatiotemporal activity of creep in the Bâlea glacial valley (Southern Carpathians) under the Transfăgărășan highway on an anthropogenic slope, using tree rings to define the spatiotemporal activity of creep and assess its potential driving and triggering factors. The dendrogeomorphological analysis included 54 Norway spruces ( Picea abies (L.) Karst). A total of 118 tree-ring series were obtained, and a 35-year chronology was constructed based on the eccentric growth of tree rings and reaction wood, with a mean recurrence interval of 17.4 years. The spatial pattern of the disturbed trees in the event years was tested using Moran’s I index. The presence of creep in this area is indicated by the stems of young trees taking on a ’d’ shape or a ’pistol-butted’ form, as well as the predominant inclination of the stems downslope direction. This inclination is not chaotic, as is typical of forests affected by landslides. The manifestation of creep is influenced by pre-existing factors, such as the substrate consisting of crystalline shale and the blanket of rubble arranged in the direction of the slope, as well as causal factors, such as the slope and precipitation. Precipitation falling within 24 h during June or July and intervals with frosty cycles from November to December and January to March were also contributing factors.