Joan Campbell

The objective of this study was to compare nutrient concentration, distribution, and select components of nutrient budgets for aspen, jack pine, and black spruce forest ecosystems at the BOReal Ecosystem Atmosphere Study, southern and northern study areas near Candle Lake, Saskatchewan and Thompson, Manitoba, Canada, respectively. The vegetation in the aspen, black spruce, and jack pine stands contained 70-79%, 53-54%, and 58-67% of total ecosystem carbon content, respectively. Soil nitrogen, calcium, and magnesium content comprised over 90% of the total ecosystem nutrient content, except for Ca and Mg content of the southern black spruce stand and Ca content of the southern aspen stand which were less than 90%. Annual litterfall N content was significantly greater for trembling aspen than for jack pine or black spruce, and was generally greater, but not significantly, for the southern than for the northern study area. Aboveground net primary production was positively correlated to annual litterfall N content for the BOREAS forests, and for all boreal forests. Annual aboveground nutrient requirements were significantly greater for trembling aspen than for jack pine or black spruce forests. Annual aboveground N requirements ranged from 37-53, 6-14, and 6-7 kg N ha-1 yr-1 for trembling aspen, jack pine, and black spruce forests, respectively. The greater nutrient requirements of deciduous than evergreen boreal forests was explained by a greater annual production of biomass and lower use efficiency of nutrients. Nutrient cycling characteristics of boreal forests were influenced by climate and forest type, with the latter having a greater influence on litterfall N, annual nutrient requirements, nutrient mean residence time, and nutrient distribution.