Fine root biomass and nutrient content in a black spruce peat soil with and without alder

Vertical distribution of fine root biomass and nutrient content was examined within a black spruce (Picea mariana) stand growing on a boreal peat soil in northeastern Ontario. The influence of site physical and chemical properties on fine root biomass production was assessed. More then 80% of the fine roots were present in moss plus the top 10 cm of peat where nutrients and aeration are most favourable. The fine root biomass (W/V) was significantly higher with alder (5.9 kg m −3 ) (Alnus rugosa) as understory vegetation compared to non-alder locations (2.9 kg m −3 ). Total nutrient content in fine roots was 54, 3.2, 5.4, 63 and 5.7 kg ha −1 on the alder site and 20, 1.4, 2.3, 28 and 4.2 kg ha −1 of N, P, K, Ca, and Mg on the non-alder site, respectively. The mass (W/V) of nutrients in fine roots was strongly dependent upon the availability of nutrients in the peat. Fine root content had a strong positive relationship with peat available P and exchangeable K contents suggesting that P and K may be limiting nutrients for black spruce in this peat soil.