Loss and Recovery Patterns in Soil N, P, and K Pools Following Different Levels of Biomass Removal in Boreal, Upland Soils.

With a fast growing interest in using forest biomass for energy production, concerns regarding soil nutrient supply and tree productivity have also been heightened.  In this context, the objectives of this long-term study were: 1) to compare the temporal changes in soil N, P, K pools resulting from different biomass harvest intensities conducted in boreal upland, black spruce-dominated site types, and 2) to determine if any of the detected soil changes were correlated to patterns in planted seedling growth or foliar nutrition.  Five sites (2 – outwash sand ; 3 – loamy till) were experimentally harvested (replicated stem only, whole-tree, whole-tree + blade, uncut control) in 1994/5 and remeasured periodically through to year 20. Application of all treatments resulted in initial (year 3) declines in N, P, K soil pools (SO = WT < WT + B).  Recovery was more rapid on the richer loam sites, particularly for N (by year 7).  In general, the magnitude of soil nutrient loss was greater and the rate of recovery slower on the infertile sandy sites.  Similarly, P and K losses were greater and recovery times extended compared to N, except for the bladed treatment.