Soil properties following clearcut harvesting and wildfire and their relationship with regeneration in the Québec Boreal forest

A comparison of the soil fertility and relationships between soil fertility and early regenerating vegetation were examined following clearcut harvesting and wildfire in the black spruce-feathermoss zone of west-central Quebec. During the summer of 1997, sampling was conducted in wildfires burnt 2, 14, and 21 years ago, stands clearcut within +/-3 years of each fire, and undisturbed control stands. At each site an estimation of vegetative cover of each species present and a volumetric sample of the forest floor (FH), and mineral soil (0--10 cm) were collected from at least 8 fire and cut sites and at least 4 control sites in each study area. The comparison between the soil fertility of stands clearcut and burnt suggested that important differences exist following these two disturbance types in the boreal forest. The forest floor of clearcut sites had greater dry mass, mass of total nutrients and mineralized N than fire or control sites, whereas fire sites generally had higher pH and concentrations of total nutrients than clearcut or control sites. Partitioning of the variance of the vegetation data between soil fertility and general site characteristic variables was carried out to evaluate the direct influence of post-disturbance soil fertility on the composition of regenerating vegetation. All explanatory variables accounted for 53.6% of the variance, of which 23.2% was exclusively attributed to soil fertility variables. Disturbance severity is suggested as an important factor, directly affecting the initial composition of the regenerating vegetation, and indirectly affecting soil fertility and stand productivity in the later stages of regeneration