Increased frequency and intensity of drought episodes as a consequence of current and predicted climatic changes require an understanding of the intra-specific variability in structural and physiological characteristics of forest trees. Adaptive plasticity and genotypic variability are considered two of the main processes by which trees can either be selected or can acclimate to changing conditions. We tested for the relative importance of genotypic variability, phenotypic plasticity and their interaction by comparing the growth and physiological performance of 15 provenances of Scots pine (Pinus sylvestris L.), under two contrasting irrigation regimes. Selected provenances representing the distribution range of the species in Anatolia, Turkey, were contrasted with seed sources spanning the range from Spain to the UK, in Europe. We found a strong latitudinal differentiation among the 15 provenances for survival after drought, largely the result of the higher mortality of some western and central European provenances. Differentiation in diameter and height growth was also clear with the worst provenance coming from Western Europe (UK). Among the Turkish provenances, the more extreme southern high-elevation populations showed greater survival and lower growth rates overall. Differences in growth and survival were related to differences in photosynthetic pigment and nutrient contents and in the photosynthetic efficiency of photosystem II. Plasticity was strongest for growth characters and pigment contents.

Kızılçam kurağa dayanıklı olması ve hızlı büyümesi nedeniyle, Türkiye'de ağaçlandırmalarda kullanılan en önemli ağaç türüdür. Ancak bu türün kurak-soğuk alanlar ve yükseklerde yayılışındaki en önemli engel dondur. Bu çalışmada kızılçamın doğal yayılış alanı içerisinde ve dışında tesis edilen orijin deneme sahalarındaki (Antalya ve Ankara) bazı orijinlerin dona dayanıklılıkları araştırılmıştır. Antalya ve Ankara'daki orijin denemelerinden ocak ayı sonunda dokuz orijininin son yıl sürgünleri örneklenmiştir. Çalışma Tesadüf Parselleri Deneme Deseninde yürütülmüş olup düşük sıcaklıklar muameleleri oluşturmuştur. Kontrol grubu düşük sıcaklığa maruz bırakılmamıştır.