Long-term water dynamics in the Lascaux cave karst: Impact of tree removal

Quantifying the hydrological dynamics of unsaturated karst environments in relation to their native vegetation is a critical step in developing adaptation strategies. This study investigates the effect of tree removal on water dynamics in the Lascaux karst hill in southwestern France. Monthly electrical resistivity tomography surveys taken over a decade evaluated rock mass heterogeneity and water content. The influence of felled tree water use on the upper 1.2 m of rock mass was studied by assessing species-level sap flow measurements scaled to estimate site transpiration. Seasonal changes in resistivity ranged from 100 to 300 Ω·m, with peak values during summer and minima in winter. Interannual variability was notable, with the resistivity recorded in summer 2021 decreasing to 130 Ω·m due to above-average precipitation. The removal of 10% of the trees in November 2016 is followed by a 27% reduction in resistivity (up to 90 Ω·m) with strongest effects during summer. During the summer immediately following tree felling, the effect was even observed down to a depth of 5 m. More globally, water flow in the emergence airlock in Lascaux cave increased by 74 m³ annually after the trees had been felled, which is in the same order of magnitude as the 37 m³ reduction in water use estimated from sap flow measurement from the nine trees cut just above the cave. The study showed a direct interplay between vegetation and hydrological processes within karst environments and highlighted the importance of considering tree management when analyzing water storage reservoirs under 1 m below ground.

Duke Scholars

Author Jean Christophe Domec Environmental Natural Science