Site and environmental legacies shape the growth–climate response of silver fir along a climatic and elevational gradient in Austria

Abstract

Silver fir (Abies alba Mill.) is a key forest tree species in Central Europe growing commonly in mixtures with beech and spruce. In forest sciences, the species has received wide attention due to the complex forest decline phase peaking in the late 1970s and the early 1980s in Central Europe, highlighting the negative effects of air pollution of that time. In the era of accelerating climate change with its adverse effects becoming apparent, the species is gaining renewed interest, especially for its further admixing potential to more resilient forest stands. In our study, we investigate the low-frequency radial growth patterns and changes, as well as the interannual variations and the corresponding climatic signal manifested in the tree-ring width chronologies of seven monospecific stands of silver fir. The study sites represent a broad climatic and elevational gradient along the distribution of the species. We compared the identified changes to recent climatic trends with more frequent dry periods since the 1980s, with specific attention to the timescale of the preceding forest decline phenomena. Following decades of radial growth decrease, culminating in severe decline at some sites, a quick recovery and increasing growth marked a period after the early 1980s, regardless of tree age and most pronounced at lower-elevation sites. The period of growth depression and recovery was accompanied by weakened or altered interannual climatic signals. During the recent decades, mean growth has been decreasing again at lower-elevation sites coinciding with drier conditions and shows signs of similar tendencies at some of the humid sites. A recent strengthening of the hydroclimatic signal, however, was not uniform in its timing among the sites. The interpretation of the results can help to further assess the resilience of silver fir to environmental stress, at the crossroads of past legacies, current and predicted challenges.