IMPACTS OF MECHANICAL SITE PREPARATION ON FOLIAR NUTRIENTS OF PLANTEDWHITE SPRUCE SEEDLINGS ON MIXED-WOOD BOREAL FOREST SITES IN ALBERTA

The impacts of different methods of mechanical site preparation (MSP) on performance and foliar nutrition of planted white spruce (Picea gla uca (Moench) Voss) seedlings were examined at two mixed-wood boreal fo rest sites (Judy Creek, Fox Creek) in Alberta, Canada. The treatments included three types of MSP: disc trench, ripper plough, and bladed, t he latter including thin and thick microsites (based on depth of remai ning organic matter); as well as a harvested-control (no MSP). Seedlin gs were planted in June 1991, four months after MSP, and foliar N, P, K, Ca, Mg, S, Mn, Fe, and Al were assessed in the second and third gro wing seasons (13, 25, and 28 months later). Nutrient concentration and relative (among treatments) foliar nutrient content scaled up to the level of the whole seedling were examined. Following analysis of varia nce, significant responses were interpreted using vector analysis. MSP did not significantly affect seedling survival, height or unit needle weight. There was a non-significant trend of higher foliar biomass fo r seedlings in MSP areas than for control seedlings. Overall, the impa ct of MSP on foliar nutrient status on these sites was minimal. The on ly consistent positive effect of MSP on seedling nutrition was increas ed foliar Mg concentrations in blade-thin sites at Fox Creek. Indicati ons of possible negative impacts of MSP include: increased Fe and Al c oncentrations in MSP areas at both sites; reduced P and K concentratio ns at both sites; and reduced Mn concentration and content at one site . The ripper treatment had the greatest positive effect on foliar nutr ient status (P, K, Mn concentration). Blading (particularly blade-thin ) resulted in the lowest concentrations of foliar P, K and Mn and the greatest increases in foliar Fe and Al. (C) 1998 Elsevier Science B.V.