Declining trends in long-term Pinus pinea L. growth forecasts in Southwestern Spain

Warmer and drier climate is among the main factors of the declining processes reported and expected for the future in the Mediterranean forest ecosystems. Pinus pinea is one the main Mediterranean conifers and its largest populations are in SW Spain, providing multifunctional services. The sensitivity of this species to drought is known, but the potentiality of its productivity to decline in SW Spain has not been yet assessed. We modeled P. pinea growth with climate covariates and a large set of tree ring chronologies from the beginning of the 20th century to the 2010s. Then we forecast annual increments over the period 2030–2100 using regionalized estimates of a global change model in three scenarios of greenhouse gas concentration. The climatic conditions between winter and mid spring were the most significant for the model. The climate predictions indicated an increase of potential water stress, and our forecasts described downturn trends of the annual growth, more accentuated in the scenario with the highest emissions and temperatures. These are the first long-term forecasts of growth of P. pinea in SW Spain. Our model cannot be directly applied at higher latitudes, where previous studies have shown differences in climate-growth relationships, but provides a benchmark for research and forestry of the potential climate-driven decrease of productivity of the P. pinea populations in the Southern Iberian Peninsula.