Age-dependent response to extreme Mediterranean climate in annual rings of brant’s oak (Quercus brantii Lindl.)

Abstract

Abstract:The relationship between tree-ring growth and climate in Quercus brantii, a widespread and dominant tree species in Zagros-Anti-Taurus Mountains, was investigated by both age-dependent and independent approaches. A total number of 118 trees were sampled in a region where severe Mediterranean climate prevailed. An overall chronology plus three age-dependent chronologies of <80, 80 to 160 and >160 years old were constructed to study growth-climate relationships based on an integrated approach of principle component stepwise regression followed by complementary response function analysis. High age heterogeneity of overall chronology diminished its climatic signals and growth priority was significantly presented in the models. Biennial and triennial precipitation variations were highly related with annual tree ring growth of young and old oaks, respectively. However, hot growing season negatively affected all age-dependent chronology indices. By increasing tree ages the negative effects of warm autumn prior to growth decreased and late winter fall became a limiting climatic factor in old trees. Results of response function analysis also revealed that all oak trees from each age classes were sensitive to increasing April temperature. It's anticipated that, regarding the trends of late frost, this species will face with many challenges in this region and similar areas.