Comparing soil profiles of adjacent forest stands with contrasting tree densities: lichen woodlands vs. black spruce–feathermoss stands in the continuous boreal forest

Abstract

We studied mature and adjacent open lichen–spruce woodlands (LWs) and closed-canopy spruce–feathermoss stands (FMs) growing under similar edaphic conditions in the continuous boreal forest zone in Quebec (Canada). A total of six pairs of stands were investigated by profile sampling. Stem density, basal area, and biomass were about four times greater in FMs than in LWs on an area basis. In the humus layer, total stocks of C and N and of exchangeable K, Ca, Mg, Al, and Na were 1.4–2.3 times larger in FM than in LW soils. The first 30 cm and the first metre of mineral soils in LWs and FMs displayed similar available nutrient pools except for total C stocks, which were more than twice as large in FM as in LW soils in these soil layers. For the whole profile, total stocks of C and N and stocks of exchangeable Ca and Mg were 1.3–2.6 times larger in FM than in LW soils. These results highlight the low intrinsic fertility of LW soils, primarily due to the humus layer, but also the importance of the biological control of C, N, and mineral nutrients in these boreal soils.