Decomposition of white spruce litter decreased and soil organic matter concentration varied along a valley-to-krummholz elevational gradient in the Chugach Mountains of south-central Alaska. Litter origin did not affect litter decomposition, and proximity of litter to alders increased decomposition only at the treeline. Soil respiration rates increased with temperature in all soils. For the organic horizons there was a pattern of increasing rates with elevation except for valley soils which had the highest rate of respiration. Soil respiration patterns for the mineral horizon were qualitatively similar to those from the organic horizon. Average summer organic soil ammonium concentrations at the forest limit and in the valley were five times greater than those in the krummholz. In the mineral soil the pattern was the same but the elevational decline was less steep and the concentrations lower. Nitrate was generally absent. Total summer nitrogen mineralization in the organic horizons decreased by a factor of five with elevation from valley soils to the treeline but increased slightly again in krummholz soils. In the mineral horizons the values, which are substantially lower than those of the organic horizons, showed a pattern of decrease with elevation (except that valley and forest limit soils were about equal). Nitrification appeared to be generally insignificant. Neither differences in soil moisture nor in mean July soil temperatures could explain elevational trends. However, valley and forest limit soils warmed up more rapidly in spring and cooled down less rapidly in fall than did treeline and krummholz soils. Available nitrogen concentrations and mineralization rates correlated strongly both with soil degree-days and elevation.
