Irrigating cork oaks until maturity in the context of climate change: Current insights from long-term experimental plots

Abstract

Cork oak (Quercus suber L.) is of major importance in the coastal regions of the western Mediterranean basin. However, its widespread chronic decline is compromising the long-term sustainability of its main product, the cork. Fertirrigation has emerged as a potential strategy to accelerate growth and reduce the time to first cork harvest, being discontinued once trees reach their productive stage. This study synthesizes the rationale, methodology, and results from long-term experimental plots in Portugal, where cork oaks were subjected to different irrigation regimes, soil conditions, and management practices. Findings demonstrate that irrigation can advance the first cork debarking to around 14 years after plantation, while promoting more homogeneous stand development. Water requirements increase over time and may reach an efficient threshold of 140 m³ ha⁻¹ per week when trees are near the first debark. However, its success depends on edaphic suitability and adaptive management to prevent adverse outcomes, such as root dependence or pest pressure. Economic analyses indicate that fertirrigation is generally advantageous until the second harvest, except when installation and maintenance costs are exceptionally high. Irrigation suppression demonstrated that trees can adapt to rainfed conditions. From an environmental perspective, irrigation should be restricted to suitable soils and rely exclusively on surface water sources. Beyond productivity, irrigated cork oak stands provided broader ecosystem services, including carbon sequestration and biodiversity enhancement. Ultimately, fertirrigation should be considered a temporary support tool that strengthens cork oak establishment and competitiveness, paving the way for resilient and sustainable forests under Mediterranean climate change scenario