Elevational Variation and Temporal Dynamics of Needle Moisture Content in Pinus sylvestris L. Seedlings

This study evaluated the temporal variation and inter-population differences in needle moisture content of Scots pine (Pinus sylvestris L.) seedlings grown from five natural populations representing different altitudinal zones. The populations ranged from sea level to 2250 meters in elevation, and the seedlings were cultivated under uniform nursery conditions at the Faculty of Forestry, Karadeniz Technical University, for four years. Needle samples were collected monthly over a 23-month period from a total of 750 seedlings, and fresh and dry weights were recorded to calculate needle moisture content. Two-way analysis of variance (ANOVA) revealed that both population and sampling time had statistically significant effects (p < 0.05), whereas their interaction was not significant. The lowest mean needle moisture content was observed in the Çamburnu population (0–450 m), while the highest was recorded in Zigana-3 (1800–2250 m), suggesting that high-elevation populations may have developed more effective water retention strategies. Seasonally, higher moisture levels were recorded in winter and early spring, while a decline was observed during summer months due to increased temperatures. The relationship between needle moisture and weight parameters varied among populations. These findings indicate that needle moisture content is a physiologically sensitive parameter influenced by both environmental conditions and elevation-driven genetic variation. The results highlight the importance of prioritizing high-elevation populations in future afforestation efforts aimed at enhancing drought tolerance and climate change adaptation.