Comparing height growth and biomass production of black spruce trees in logged and burned stands

The strategy of using advanced layering for regenerating logged black spruce stands has become a common practice. Compared with natural post-fire black spruce stands, this strategy may alter stand structure with a possible change in stand productivity. Using harvested tree data from sample plots established in burned and logged stands, 50 years after disturbance, and on similar soils, we compared the structure, height growth, and biomass allocation of both types of stands. Stem analysis revealed that black spruce trees in logged stands reached their maximum height growth later and at a concomitant lower level than black spruce trees in burned stands. Biomass production was comparable between stand types but was reduced when ericaceous shrubs were abundant. Compared to natural post-fire stands, logged stands present a shift of biomass allocation to branches and to leaves. These mechanisms are interdependent and represent the tree adjustment to the altered structure in logged stands characterised by the fragmented canopy with the increase of ericaceous shrubs cover and of organic layer thickness.