Deadwood density, C stocks and their controlling factors in a beech-silver fir mixed virgin European forest

• Published in: Forest ecology and management 2023-07, Vol.539, p.121007, Article 121007
• Main Authors: Petritan, Ion Catalin, Mihăilă, Victor-Vasile, Yuste, Jorge Curiel, Bouriaud, Olivier, Petritan, Any Mary
• Format: Article
• Language: English
• Subjects: Carbon estimation; Decay classes; Logs and snags; Species-specific deadwood density
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2023.121007

•Dry deadwood density for silver fir and European beech among different decomposition classes was assessed in a virgin forest.•Dry density is species-specific and decreases with decomposition advancing stronger for beech compared to fir.•Estimated carbon sequestered as deadwood varied greatly (from 0.36 to 41.16 MgC ha−1, mean value of 15.96) within the virgin forest.•Local estimate of dead wood density per species and decomposition class is necessary for a higher accuracy of deadwood necromass estimation. Deadwood is a fundamental structural and functional component of forests, with a crucial role in supporting forest biodiversity, nutrient and carbon cycling. Precise deadwood density estimates and its relation to environmental factors are necessary to evaluate the biomass and carbon stocked in this component. In this study, we estimated dry deadwood density for two different tree species, silver fir (Abies alba) and European beech (Fagus sylvatica) and for three snags and five logs decomposition classes in a virgin mixed beech-fir forest in the Southern Carpathians. The goal was to assess how deadwood density is influenced by different abiotic (moisture, elevation, slope, aspect) and wood-related factors (rottenness, position along the piece, contact with the soil). For snags, the mean dry density showed a reduced variability within decomposition classes (484–326 kg.m−3 for beech and 374–319 kg.m−3 for fir), compared to the logs (486–139 kg.m−3 for beech and 359–161 kg.m−3 for fir). While the mass moisture varied slowly in the first three decay classes (around 60–80 %), it increased sharply in the last two decay classes of logs (>140 % in the fourth class and > 350 % in the last one). The rottenness increased with the decay class in a similar way for both species. The contact of logs with the soil influenced positively the moisture, but the position of the sampling within the piece did not play any significant role in the variability of density. Based on density estimates per decay classes we estimated that the carbon (C) stored in deadwood varied greatly among the 21 plots from 0.36 to 41.16 MgC ha−1, with a mean value of 15.96 ± 2.36 (±SE) MgC ha−1. Our study suggests that volume-based calculations might yield biased quantitative estimates of C stored in deadwood unless a local estimate of dead wood density corrected per species and decomposition class is applied. Moreover, the use of an averaged value of dry density instead of value for each decay cla