Tree-Ring Growth Trends of Abies alba Mill: Possible Adaptations to Climate Change in Marginal Populations of Central Italy

Abstract

A dendroclimatic analysis was used to assess the climate-growth relationships of Abies alba Mill. over the last century in marginal populations of Central Italy. Tree-ring cores were collected in five mixed silver fir forests at low and high-elevation sites of the Apennines range in Tuscany and Marches. Regular and moving correlations functions were applied to tree-ring width series and monthly climate gridded data. Principal component analysis displayed groups of chronologies with similar growth patterns, discriminating for altitude and geographical location. Climate-growth relationships showed the positive influence of late-spring and summer precipitations and the negative effect of summer temperatures. Stands growing within the optimal altitude range for the species showed a positive and a decreasing negative influence of spring and summer temperatures, respectively. At the highest site (1375 m asl) the positive effect of previous year spring-summer precipitation and summer temperature of both previous and current year became scarce or null. Results suggest that the shifting influence of summer precipitation on tree-rings growth from July to August of the previous year is a possible response of silver fir to the significant reduction of spring precipitation and general temperature increase throughout the 20th century.