Biomass allocation and growth of young black spruce (<i>Picea mariana</i> (Mill.) B.S.P.) trees

Accurately predicting biomass allocation to below- versus above-ground tree parts is crucial in estimating carbon stocks in forest ecosystems. A 9-year outdoor experiment was conducted to analyze the variations in biomass allocation in below- and above-ground parts in black spruce trees growing at the edge or at the center of a raised garden bed. Dry biomass, length, and radial growth of stems, branches, and roots were measured as well as the annual above-ground growth for the five most recent years prior to harvesting. We found that more than 90% of dry biomass was allocated to the above-ground tree parts whereas less than 10% was allocated to the root system. Strong correlations were found between the different tree parts regardless of the tree’s position in the delimited growth area. Annual growth variables declined from 2018 to 2022, likely due to increased competition for resources. The dry biomass of the woody root and the root surface close to the stem were well correlated to the above-ground tree parts (varying between 45% and 95%). Thus, the strong link between the root system and the above tree parts is confirmed.