Importance of Dead Wood in Virgin Forest Ecosystem Functioning in Southern Carpathians

Dead wood (DW) is an important component of sustainable forest management and climate change mitigation. Three research plots (each with an area of 1 ha), located in virgin forests in the Southern Carpathians (Semenic P20, Retezat–Zănoaga, and Făgăraș–Șinca), were installed in order to study the synergies between DW and climate change mitigation effects. Data on the dendrometric characteristics of standing and lying DW, the species, and the degree of decay were recorded. The aboveground biomass (AGB) and carbon stock (CS) of the DW were also determined. The DW volume was between 48 m³·ha⁻¹ and 148 m³·ha⁻¹, with the total volume (dead and alive) ranging between 725 m³·ha⁻¹ and 966 m³·ha⁻¹. The DW volume distribution shows a decreasing trend, with the most suitable theoretical distributions for describing this being the lognormal, the 2P Weibull, and the 2P-Gamma. The AGB ranged between 17 t·ha⁻¹ and 30 t·ha⁻¹ and showed a decreasing trend according to altitude. The CS was between 8 t·ha⁻¹ and 14.33 t·ha⁻¹. A slow decomposition rate for the hardwood was identified by analyzing the relationship between the surface and volume of the DW. This highlighted the capacity of DW to store carbon for a long period of time.