Robert Korzeniewicz, Marlena Baranowska, Bartosz Bułaj, Weile Chen, Szymon Czajkowski, Maria Hauke-Kowalska, Anna Ilek, Grzegorz Iszkuło, Wojciech Kowalkowski, Adrian Łukowski, Andrzej Mazur, Joanna Mucha, Radosław Witkowski, Marcin Zadworny
Root morphology, carbohydrate pools, and mycorrhizal associations of silver fir across contrasting canopy conditions
Dendrobiology 2026, vol. 96: 34-53
https://doi.org/10.12657/denbio.096.004
Abstract:
The widespread decline of Norway spruce has led to larger gaps in the canopy of Central European mountain forests, potentially affecting the regeneration of shade tolerant silver fir (Abies alba Mill.). We examined whether greater light availability in canopy gaps influences the morphology of fir needles and fine roots, their carbohydrate concentrations, and their fungal associations, as trees may respond to environmental changes in both their canopy and in their belowground interactions. We compared small patches of fir trees under a closed canopy and low light conditions with regenerating patches growing in gaps with greater light transmission (i.e. canopy gap). We quantified understory photosynthetically active photon flux density (PPFD%), soil water storage, shoot apical dominance, needle specific leaf area (SLA), fine root traits (AD- average diameter, SRL- specific root length, SRA- specific root area), root and leaf tissue nitrogen (N), non-structural carbohydrates (TNC), and characterized root-associated fungi via ITS2 sequencing. Canopy gaps had 1.5 times higher PPFD and reduced soil water storage. Silver fir individuals in canopy gaps also displayed greater apical dominance, thinner roots, and longer SRL and greater SRA compared with individuals under a closed canopy. Contrary to our expectations, the concentrations of soluble sugars and total non-structural carbohydrates were higher under the closed canopy. Meanwhile, gap saplings exhibited higher tissue nitrogen levels in both roots and needles. Light availability also influenced belowground symbiosis as canopy gaps saplings hosted a more diverse ectomycorrhizal fungal community (higher α-diversity), whereas the long-distance morphotype of Boletus occurred under a closed canopy and covaried positively with carbohydrate pools and negatively with SRL. These linked changes illustrate a shift from carbon conservative, symbiont supported growth in shaded patches to more acquisitive root strategies in canopy gaps.
Keywords: Abies alba, Picea abies decline, mixed montane forests, canopy gaps, resource acquisition strategies,
ectomycorrhizal fungi, fine roots