LITTER QUALITY AND ITS POTENTIAL EFFECT ON DECAY-RATES OF MATERIALS FROM CANADIAN FORESTS

Decomposition is influenced by a wide array of factors including macro climate, microclimate, soil biota, soil nutrients, substrate piece siz e and substrate quality. To separate the influence of some of these fa ctors a 10-year study, the Canadian Intersite Decomposition Experiment , was established in 1992 to measure the decay of 11 standard litter t ypes on a range of forest types at 21 sites across Canada. As part of the study we analysed the initial elemental contents (N, P, S, K, Ca, Mg) and carbon (C) fractions (extractables, cellulose, hemicellulose, lignin) by C-13 NMR and wet chemical proximate analysis in a total of 37 primarily foliar litter types representative of the range of specie s found at, the different CIDET sites. Litter types especially non-con ifer species varied greatly in their qualities. Principal component an alyses showed that the litter types could be distinguished by the elem ental macronutrient contents through the ratio of N+P+K:S, by proximat e chemical analyses through the ratio of water soluble:acid fractions, and by NMR through the ratio of O-alkyl:alkyl C. Litter quality data was used in three simple models of litter decay to predict how the mas s toss of the different litter types could vary. Two models using a li near or single exponential decay equation and litter lignin and N cont ent predicted a 2-5 fold difference in total mass loss for the differe nt litter types. A third model using a summed exponential decay equati on for three chemical fractions and a ligno-cellulose index predicted that for all but one litter type, variation in mass loss between types would be less than a 20%.