2.4.2 Synchrony estimation
We employed two methods to estimate growth synchrony, one to estimate intraspecific variation in climate sensitivity of individual trees, the second to estimate the climate sensitivity of whole assemblages.
Tree-level growth synchrony was estimated by calculating the Pearson’s correlation coefficient correlating between the RWI series of individual trees with the species-specific RWI chronology of their corresponding stand. This was done for the two most abundance species in the Carpathians, P . abies and F . sylvatica.These correlation coefficients were used as direct estimators of tree-level growth synchrony for all tree-level analyses.
We derived a second synchrony metric to provide point estimates of growth synchrony that integrate structural and compositional variability. To do so, we estimated the correlation among the RWI series of all overstory trees, regardless of species, co-occurring within forest inventory plots and averaged over these correlation coefficients to estimate the mean interseries correlation (\(\overset{\overline{}}{r}\)) for each inventory plot. By restricting this second synchrony metric exclusively to individuals from the overstory competition category, analyses better reflect relationships between synchrony and forest productivity. The overstory competition class comprised over 90% of forest basal area, thus our estimates of\(\overset{\overline{}}{r}\) are not influenced by abundant understory trees that contribute marginally to forest biomass production, but could greatly influence \(\overset{\overline{}}{r}\) estimates.