Assessing Physiological Performances of Quercus suber L. After Cork Stripping and Kaolin Application

Cork oak (Quercus suber L.) forests play a crucial role in the Mediterranean region, providing essential ecological, social, and economic services. Increasing pressure from wildfires, pests, diseases, and climate change has led to a progressive decline of these ecosystems, making the development of innovative post-stripping management strategies urgent. This study evaluates the effectiveness of kaolin application on cork oak trees immediately after cork removal in a mixed forest in Sant Celoni (Barcelona, Spain). Short- and long-term physiological responses were assessed through stomatal conductance and chlorophyll fluorescence (OJIP test), while sap flux density (Js) was continuously monitored over a four-month period (July–October 2023) using IoT-based TreeTalker® Cyber (Nature 4.0 s.r.l., Viterbo, Italy). Proximal vegetation indices (Normalized Difference Vegetation Index, NDVI; and Normalized Difference Red Edge, NDRE) were also evaluated but showed no significant differences among treatments (p > 0.05). Kaolin-treated trees (K) maintained significantly higher photosynthetic performance and stem water transport capacity compared to untreated stripped trees (nK), with effects persisting up to 140 days after stripping. These findings support kaolin application as a viable and low-cost tool for mitigating post-stripping physiological stress in cork oak forest management. Further research across multiple sites and consecutive harvesting cycles is recommended to fully assess its long-term implications for tree vitality and cork productivity.