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.