Effects of a three-year warming on the growth and nutritional status of the young generation of silver fir (Abies alba Mill.) in the Western Carpathians

Abstract

Climate warming significantly affects forest ecosystems, altering site conditions and threatening main forest-forming species. Norway spruce (Picea abies (L.) H.Karst) stands in the Central Europe are declining due to climate change, necessitating alternative silvicultural strategies. Silver fir (Abies alba Mill.), shade-tolerant species with the potential to form multi-storey stands, has been proposed as a potential replacement. However, its response to warming in spruce-dominated stands remains unclear. This study presents results from a three-year in situ climate experiment in the Western Carpathians, where soil warming of 0.5 °C simulated future climate conditions. Dendroclimatic and biogeochemical approaches were used to assess the effects of warming on the growth and nutrient status of young silver fir trees, growing as a young generation in a decaying spruce stand. Results indicate that while initial height and diameter growth were not significantly affected by warming, a declining growth trend emerged after three years, suggesting that temperature conditions exceeded the species' optimal range. Furthermore, warming reduced main macro- and micronutrient concentrations in fir needles, especially calcium (Ca), phosphorus (P), potassium (K), magnesium (Mg), copper (Cu) and manganese (Mn), which are essential for physiological processes and stress resistance. Stoichiometric analyses revealed shifts in carbon (C), nitrogen (N) and P ratios, indicating possible nutrient imbalances. The results highlight the vulnerability of young fir trees to warming and suggest that future forest adaptation strategies must consider both physiological responses and site conditions. Long-term studies are needed to determine the sustainability of silver fir as a replacement species in mountain ecosystems.