Litter Decomposition in a Subarctic Spruce‐Lichen Woodland, Eastern Canada

Abstract

The litter bag technique was used to examine the decomposition of six litter types (representing Picea mariana, Cladina stellaris, Betula glendulosa, and Ledum groenlandicum) and standard cellulose. The decomposition was measured over a 2—yr period, with tissue samples placed on a recently burnt site and on top of and beneath a lichen mat in a mature spruce—lichen woodland in northern Quebec. Mass losses after 2 yr were between 10 and 60%, with the largest losses occurring in B. glandulosa and L. groenlandicum leaves and the smallest in C. stellaris; 60—90% of the lst—yr mass loss occurs during the winter (September to June). The exponential decay constant k ranged from —0.05 to —0.53. There were few statistically significant differences in decomposition rate among the three sites. Of the chemical constituents analyzed, original concentrations of Ca, carbohydrate, P.K. and N were closely correlated either with the decomposition parameter k or with mass remaining after 1 or 2 yr. Ca, Mg, and k are rapidly lost from the decomposing tissues, except for C. stellaris. All the tissues, except B. glandulosa, showed an accumulation of N. associated with high C:N ratios. The results emphasize the importance of N to this ecosystem, in that it tends to remain immobilized in the litter, at least over the first 2 yr.