Climate-tree-growth relationships of Quercus cerris and Q. pubescens growing in simpatry in the National Park of Pollino (Basilicata region, southern Italy)

In order to improve the ecological understanding of Quercus cerris and Q. pubescens, a comparative dendroecological investigation was carried out. In addition a master chronology (1497-2004) of Quercus spp. was developed using some old beams. The study site is located in a mesic area at 3 km from the village of Terranova di Pollino (PZ) in southern Italy (Basilicata Region) and contains one of the oldest and largest oak stands growing in Italy (more than 250 years, wider than 2 m at breast height). The influence of climate was assessed comparing total ring width indices with monthly mean temperature (Tmean) and Precipitation (P) registered at Teana (PZ) and Campotense (CS) meteorological stations, respectively, from 1924 to 2000. Response functions were performed for two periods: (1925-1972) and (1953-2000) to analyse how the growth-climate relationships changed throughout time and to detect these changes in the climatic response of Quercus spp. A negative relationship with Tmean (during winter and summer) and a positive one with summer precipitation were detected. These results clearly indicate that summer drought is one of the main limiting factors in Quercus spp. growth in the study site.