Avaluació de l’ús dels anells de creixement del faig com a indicadors del canvi climàtic

Abstract

The present research is focused on the dendrocronologyc study of the climate change effect on beech-growth (Fagus sylvatica), in the Fageda d'En Jordà (Garrotxa). Two zones have been studied in function to their protection regime: the first catalogued as a Partial Nature Reserve (public managing) and the second catalogued as a Nature Park (private managing). The climatic variables chosen are the median temperature, the maximum temperature, the minimum temperature and precipitation. These climatic variables have been analysed considering different periods: annual, beech growing period (from March to August) and in de middle of beech growing period (April). The variables of growth studied are the width of the rings, the Increase of Basal Area (BAI) and the diameter. Also the age of individuals has been considered. Firstly, it has been evaluated if there was a variation of the climatic variables along the last 35 years. Straightaway, it has been analysed if there was a relationship between age and individuals growing. Finally, it has been determined if there is a linear regression between the climatic variables and the variables of individuals growth in the studied periods. The results obtained, indicate a significant increase in median temperature and in minimum temperature along the years studied, in all variables used (annual median, median of growing period March-August, or April median). It has also been observed a significant influence of individuals age on their ring width and their diameter. Finally it has been possible to notice a BAI reduction in the Natural Reserve due to the growing period median temperature increase, but above all due to the annual, beech growing period (March-August) or April minimum temperature increase