Climate triggers and growth effects of cold damage in silver fir (Abies alba Mill.) populations from Eastern Carpathians

At the eastern range limit of silver fir, there is moderate population differentiation in tolerance to frost damages. Differentiated management measures accounting for climate change are required, as some populations are not responding similar to drought and frost damage.

Under ongoing climate change, it is expected that in Europe 35% of forests will be at risk of frost, especially in the eastern part. In trees, frost effects are imprinted in rings and our study was conducted in juvenile individuals of silver fir from a trial comprising nine provenances from the eastern species distribution range. We analyzed the main characteristics of frost rings, their climate determinants and influence on height growth. Compared with other species, we found a slightly higher proportion of frost rings, and that the tracheid form was significantly influenced by the position within the ring and the intensity of damage. The climate covariates best explaining the frost damage in the initial and late frost rings were the March minimum temperature and the May mean temperature, respectively. A test of local adaptation indicated two characteristics related to the climatic determined late frost—the growing degree days accumulations until late frost and its day of the year, as significant triggers of the initial and late frost rings. In the initial frost ring, the height growth was negatively influenced by the proportion of annual rings affected over 50% by frost; in the late frost ring, an unexpected-positive influence on height growth of the proportion of total damaged annual rings was identified, possibly related to favorable growing seasons with prolonged autumn activity. Our study identified differentiation between provenances, which was more evident in the initial frost ring, suggesting maladaptation of eastern populations to frost-related events.