Decomposition of boreal forest litters from central Alberta under laboratory conditions

Abstract

Decomposition of foliage litter from jack pine (Pinusbanksiana Lamb.), white spruce (Piceaglauca (Moench) Voss), balsam fir (Abiesbalsamea (L.) Mill.), green alder (Alnuscrispa (Ait.) Pursh.), two feathermosses (Hylocomiumsplendens (Hedw.) B.S.G., Pleuroziumschreberi (Brid.) Mitt.), and a lichen (Cladinamitis (Sandst.) Hale & W. Culb.) was examined by measuring weight loss at 5-week intervals during a 35-week laboratory incubation (constant moisture, 23 °C). Weight loss by most litter types was more precisely described by a two-component than a one-component exponential decay model. Decomposition of lichen was best described by a one-component model as is consistent with the chemical and structural homogeneity of this litter. Decay rate was not correlated with concentration of C, N, soluble tannin or lignin, C:N ratio, or lignin:N ratio, although weight loss and lignin:N ratio were correlated in a combined data set that included data from published literature. Cutting pine needles into 1-cm lengths doubled initial decomposition rates, indicating that physical constraints associated with litter structure exert a strong influence on decomposition. Such structural controls limit the use of litter chemistry to predict decomposition rates. Relative differences in decomposition rates among litter types appeared to be reflected in forest floor properties, suggesting that plant species play different roles in the control of decomposition-related ecosystem processes.