Long-Term NDVI Monitoring of Relict Beech (Fagus sylvatica L.) Forests in Mediterranean Historic Landscapes: Evidence of Vegetation Resilience Patterns

Mediterranean historic landscapes include relict forest ecosystems that preserve significant ecological and biocultural legacies while providing insights into ecosystem resilience under climate change. Among these, low-elevation beech forests (Fagus sylvatica L.) represent climatically marginal populations whose persistence depends on favorable local environmental conditions. This study assessed the resilience of four relict beech forests in the Tolfa-Cerite area (northern Latium, Central Italy) using a 38-year Landsat NDVI time series (1984–2022) integrated with climatic and bioclimatic data. Seasonal NDVI dynamics were reconstructed through a Monte Carlo optimization approach to evaluate long-term vegetation trajectories, summer productivity, and phenological changes. Results revealed a general decline in annual NDVI across all stands, consistent with increasing temperatures and decreasing precipitation. In contrast, summer NDVI remained stable or increased in several forests, indicating the maintenance of canopy greenness during the Mediterranean summer season. These findings suggest that local environmental heterogeneity, including volcanic substrates, favorable hydrological conditions, and microclimatic buffering, enhances resilience despite increasing drought pressure. Several relict beech forests maintained vegetation functioning despite increasing climatic stress, supporting their interpretation as potentially resilient ecosystems and candidate climate refugia within Mediterranean historic landscapes. The study highlights the value of long-term Earth Observation data for assessing ecosystem resilience, identifying climate refugia, and supporting adaptive conservation strategies under climate change.