AIRTREE v2.0: predicting ecosystem services provided by Italian urban parks under climate change scenarios

In an era of climate change and increasing air pollution, accurately quantifying forest ecosystem services-particularly in urban and peri-urban contexts-is essential. Species selection for these areas requires identifying trees that are both climate-resilient and effective at carbon sequestration and pollutant removal. We present an upgraded version of the AIRTREE v1.0 multi-layer canopy model to assess ecosystem services provided by urban parks placed in 43 Italian sites established under a national reforestation program. Simulations were performed under two climate scenarios (Representative Concentration Pathways, RCP4.5 and RCP8.5) projected for 2054. The analysis focused on Net Primary Productivity (NPP), ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO), sulphur dioxide (SO₂), particulate matters PM₁₀ and PM₂.₅, as well as Biogenic Volatile Organic Compounds (BVOCs), including isoprene and monoterpenes. Model reliability was tested against five Italian Integrated Carbon Observation System sites with measured carbon fluxes. Model calibration showed rapid convergence and robust performance, with high accuracy for gross primary productivity (Kling-Gupta Efficiency, up to 0.90). Sensitivity analysis highlighted photosynthetic capacity (e.g., Vcmax) driving NPP as the dominant control in Alpine and Continental biogeographic regions, whereas stomatal regulation and water stress parameters were more influential in Mediterranean sites. Across both climate scenarios, southern Mediterranean areas consistently showed the highest NPP. Under RCP8.5, NPP significantly increased (+9%), along with evapotranspiration (+8%) and BVOC emissions, while O₃ and NO₂ decreased and PM₁₀ slightly increased. Species-specific responses confirmed strong functional heterogeneity, with Sorbus torminalis maximising O₃ uptake, Pinus halepensis excelling in PM removal and Quercus pubescens showing high carbon sequestration. As an open-access tool, AIRTREE v2.0 provides robust support for evaluating ecosystem services under current and future climate scenarios.