Tree litter production in coniferous old-growth forests on organic soils

Canopy litterfall is a vital component of forest ecosystems, facilitating nutrient and organic carbon transfer to the soil. Understanding litterfall dynamics in forests is crucial for assessing carbon fluxes at the national level and refining carbon balance estimations. However, information about aboveground litterfall dynamics in old-growth forests remains scarce. The aim of the study was to characterize the annual litterfall carbon input in coniferous old-growth forests on drained and undrained organic soils. In total, 12 old-growth Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) forests stands with the age range of 146 – 171 years were selected. Using cone-type litter traps, we obtained data on litterfall volumes over a one-year period. Our findings reveal that old-growth forest annual carbon input from litterfall exceeds estimates of mature forest stands aboveground litterfall. In drained sites, mean annual litter carbon input reached 2.80 ± 0.29 t ha⁻¹ yr⁻¹, while in undrained sites, it amounted to 2.17 ± 0.17 t ha⁻¹ yr. Basal area and deadwood showed a close positive correlation with annual litter carbon input, underscoring the peculiarities of late successional forest stand carbon dynamics. Total stand basal area as easily measurable forest inventory parameter was the best predictor of annual litter C input for practical application.