Stage-Specific Responses to Warming in Trojan Fir Across Early Life Stages: Germination, Seedling Survival, and...

Understanding the early life-stage responses of tree species to climate change is critical for predicting forest regeneration success and guiding conservation and management efforts. We investigated the effects of temperature, cold stratification, and light on germination and early seedling performance of Abies nordmanniana subsp. equi-trojani (Trojan fir), an endangered endemic tree from north-western Anatolia (Türkiye). Germination was tested under fixed (10°C, 15°C, 20°C, 25°C, 30°C) and alternating (15°C/25°C, 20°C/30°C) incubation temperatures with and without cold stratification. Early seedlings were monitored for 10 days under controlled, nutrient-free agar conditions. Our results show that while higher fixed and alternating temperatures enhance germination, early seedling survival declined at the warmest temperature (30°C), and root growth peaked at 20°C and decreased at higher temperatures. Cold stratification significantly improved germination across all temperature regimes, reducing the need for warmer incubation temperatures to achieve high germination. Light had a limited effect on overall germination. These findings indicate stage-specific responses to warming, as warmer conditions favor germination, whereas cooler conditions favor early seedling survival and root allocation. Consequently, successful regeneration assessments and conservation planning should consider both germination and early seedling stages, alongside local thermal contexts, when evaluating the impacts of climate change on Trojan fir.