Climate signals in a multispecies tree-ring network from central and southern Italy and reconstruction of the late summer temperatures since the early 1700s

A first assessment of main climatic drivers modulating the tree-ring maximum latewood density (MXD) and the tree-ring width (RW) along the whole Italian Peninsula and north-eastern Sicily was performed including 27 forest sites of conifers (RW, and MXD) and of broadleaves (only RW). Tree-ring data were compared by means of correlation analysis with monthly and seasonal variables of temperature, precipitation and standardized precipitation index (used to characterize the meteorological drought) against each species-specific site chronology and against the Highly Sensitive to Climate (HSTC) chronologies (based on selected indexed individual series). We find that climate signals in MXD are stronger and more stable over time than in RW. In particular, conifer MXD variability is directly influenced by late summer (August, September) temperature and inversely influenced by summer precipitation and drought (SPI at timescale of 3 months). Conifer RW evidence an influence of previous summer climate variables (temperature and drought), whereas broadleaf RW is more influenced by summer precipitation and drought of the current growing season. The reconstruction of late summer temperature for the Italian Peninsula for the last 300 yr, based on the HSTC chronology of conifer MXD, shows stable model performances, underlining periods of climatic recrudescence around 1699, 1740, 1814, 1909, 1939 CE and well following the variability of the instrumental record. Considering 20 yr low-pass filtered series, the reconstructed temperature record deviates always <1°C from the instrumental record. These deviations probably occur because of precipitation patterns and drought stress that also influence the tree-ring MXD. The reconstructed temperature variability is valid for a west-east oriented region comprising Sardinia, Sicily and the western Balkan area along the Adriatic coast.