With a renewed and fast growing interest in using forest woody biomass for energy production, concerns regarding nutrient loss and impacts to soil quality have also been heightened. In this context, the objectives of the current study were: 1) to document changes occurring to components of the soil N pool resulting from different biomass harvest intensities conducted, and 2) to determine if any of the detected changes in soil N indices are correlated to patterns in planted seedling growth or foliar nutrition.

Nine sites black spruce stands were selected to cover a range of edaphic conditions from outwash sands to peatlands. In 1994/5, experimental harvests were conducted that provided a range in biomass removal from no removal of logging debris to a complete removal treatment. In the fall of 2005 (10 years since harvest), soil samples were collected from the forest humus layer and upper B horizon (10-15 cm) to determine TC, TKN, DOC, TSN MB-C and MB-N, and mineralizable N. In addition, planted black spruce seedlings located in close proximity to the soil sampling pits were clipped for foliar N.

When comparing the harvest treatments, there was a consistent downward trend in most soil parameters in association with increased biomass removal. However, it was primarily the complete biomass removal treatment that was consistently lower, with the TL, Chip, and FT treatments being very similar to each other. Foliar N, in contrast, was strongly influenced by site type, although some significant harvest treatment effects were also detected. Of the soil parameters measured, mineralizable N had the highest correlation to the foliar N measurements. This is an easily applied, rapid technique that should be considered as part of a soil quality monitoring protocol when evaluating the sustainability of emerging new biomass harvesting alternatives.