Biomass Modeling in European Beech and Norway Spruce Plantations: An Opportunity to Enhance the Carbon Market and Climate Sustainability

This study examines the differences in growth patterns, biomass accumulation, and carbon storage between planted European beech and Norway spruce in the Western Carpathians, Slovakia. Two approaches were used to analyze young forest trees and stands: destructive tree sampling and repetitive tree measurements. Biomass modeling was conducted for individual tree components and entire trees, demonstrating that stem diameter and height were strong predictors of biomass. Notably, beeches exhibited greater tree biomass than spruces when analyzed at the same stem diameter, whereas the opposite trend was observed when tree height was used as the predictor. At the stand level, biomass modeling incorporated the mean diameter, mean height, or stand age. Two primary tree components were analyzed: woody parts, which store carbon long term, and foliage, which stores carbon for shorter periods. Stand age emerged as the most reliable predictor, providing real-time estimates of biomass and carbon storage. At a maximum modeled stand age of 12 years, beech biomass stock was 18 Mg ha−1, compared to 58 Mg ha−1 for spruce (uniform tree spacing of 2.0 × 2.0 m for both species was considered). Correspondingly, carbon storage values were 9 Mg ha−1 for beech and 29 Mg ha−1 for spruce, demonstrating a threefold difference in favor of spruce. The study also examined the biomass transition to necromass, specifically foliage litter loss. Over 12 years, spruce stands shed 10.3 Mg ha−1 of needle litter, while beech stands lost 5.4 Mg ha−1. A 12-year-old beech stand fixed-carbon (necromass in form of foliage litter was not included) equivalent to about 30 Mg CO2 per ha, while a spruce stand of the same age fixed nearly 107 Mg CO2 per ha. The carbon storage in live trees translates into financial values about EUR 2000 per ha for beech and over EUR 7000 per ha for spruce, highlighting an economic advantage for spruce in carbon sequestration markets as part of climate sustainability efforts. However, in practice, these differences could be partly reduced through denser (more than double) planting of beech compared to spruce.