LITTER DECOMPOSITION IN WESTERN RED CEDAR AND WESTERN HEMLOCK FORESTSON NORTHERN VANCOUVER-ISLAND, BRITISH-COLUMBIA

Litter decomposition and changes in N and organic chemicals were studi ed for 2 years in two forest types: old-growth western red cedar (Thuj a plicata Donn) and western hemlock (Tsuga heterophylla (Raf.) Sarge) and 85-year-old stands of western hemlock and amabilis fir (Abies amab ilis (Dougl.) Forbes) that developed after a major windstorm. We teste d the hypothesis that lower rates of mass loss and different patterns of nutrient release in decomposing litter could explain lower nutrient availability in the cedar-hemlock type. Decomposition rate of a stand ard litter substrate, lodgepole pine needles, was almost identical in the two forest types indicating that each type had similar microenviro nmental conditions for decomposers. Salal leaves had a lower lignin to N ratio and decomposed and released N more rapidly than the conifer l itters. Among the conifers, cedar had poorer litter quality (higher li gnin to N ratio), decomposed more slowly, and released considerably le ss N during the study. Cedar litter contributes to lower N availabilit y in cedar-hemlock forests, but other factors, such as lower external N cycling and complexing of N with secondary carbon compounds during l ater stages of decomposition, are also likely to have a major influenc e on N availability.