LITTER PRODUCTION AND NUTRIENT RESORPTION IN WESTERN RED CEDAR AND WESTERN HEMLOCK FORESTS ON NORTHERN VANCOUVER-ISLAND, BRITISH-COLUMBIA

Fine litter fall and concentrations of N and P in green foliage and fo liar litter were measured in three species over 1 year in two forest t ypes at three sites on northern Vancouver Island to explore the hypoth esis that differences in nutrient use and cycling between the dominant tree species on each forest type contribute to differences in forest floor nutrient availability. Total annual aboveground fine litter fall was significantly higher in second-growth, windstorm-derived 85-year- old stands of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and am abilis fir (Abies amabilis (Dougl.) Forbes) forests (4137 kg.ha(-1)) t han in adjacent old-growth forests of western red cedar (Thuja plicata Donn) and western hemlock (3094 kg.ha(-1)) occurring on similar sites . Cedar had significantly lower N concentration in green foliage (9.3 mg.g(-1)) and litter (4.3 mg.g(-1)) than the other species in each for est type. Hemlock had a higher litter N concentration in the hemlock - amabilis fir type (8.3 mg.g(-1)) than in the cedar-hemlock type (6.4 mg.g(-1)). Cedar resorbed a significantly higher percentage of N durin g leaf senescence (76%), than hemlock in the cedar-hemlock type (64%), hemlock in the hemlock - amabilis fir type (51%), or amabilis fir (18 %). Nitrogen-use efficiency (litter-fall mass/litter N) was considerab ly higher in cedar (235 kg litter/kg N) than in the other species in e ither forest type (90-156 kg litter/kg N). These results suggest that differences within and between species in the two types in nutrient us e and the amount of nutrients cycling through the litter fall and inte rnal redistribution pathways are contributing to lower rates of nutrie nt cycling and forest floor nutrient availability in the cedar-hemlock type.