Warming-driven treeline shifts in Ilgaz Mountain, Türkiye

Alterations in treeline ecotones within mountain ecosystems are widely recognized as sensitive indicators of climate change. This study investigates treeline dynamics in the Ilgaz Mountain region, Türkiye, over a 23-year period (2000–2023) by integrating high-resolution satellite imagery with long-term meteorological data. Treeline elevations were analyzed across different slope aspects to assess spatially heterogeneous responses to climatic variability. Our results reveal a statistically significant upward shift in the treeline on south-facing slopes, with the mean treeline elevation increasing from 2021 m to 2032 m (p < 0.05), while no significant shifts were detected on other aspects. Long-term climatic analyses indicate pronounced warming in the study area, with mean annual temperature increasing by approximately 1℃, particularly after 2010. Mann–Kendall trend analysis confirms a strong, significant positive temperature trend (τ = 0.522, p < 0.001). In contrast, annual precipitation shows no significant temporal trend (τ = 0.138, p = 0.36). Similarly, the De Martonne aridity index does not exhibit a statistically significant directional trend, although index values suggest a gradual transition from very humid to humid conditions at the treeline ecotone. The observed aspect-specific response to warming underscores the importance of local microclimatic and topographic controls in mediating treeline sensitivity to climate change, even over relatively short time periods. Overall, this study demonstrates the utility of high-resolution remote sensing techniques for delineating treeline boundaries and detecting landscape-scale changes in complex mountain environments.