LITTER MASS-LOSS RATES IN LATE STAGES OF DECOMPOSITION AT SOME CLIMATICALLY AND NUTRITIONALLY DIFFERENT PINE SITES - LONG-TERM DECOMPOSITION IN A SCOTS PINE FOREST .8.

The patterns of some chemical changes and litter mass-loss rates were investigated for a variety of types of decomposing litter in pine fore sts under different climatic conditions and at sites with different nu trient status. A mixed deciduous forest was also compared. In initiall y chemically identical Scots pine needle litter incubated under differ ent climatic conditions, the lignin concentration increased faster as a function of accumulated mass loss when the climatic conditions promo ted a higher initial mass-loss rate. Also under artificially created c onditions, e.g., after fertilization and irrigation, the same phenomen on occurred. Litter mass-loss rates decreased during decomposition as lignin concentrations increased. The relative decrease was significant ly larger at sites with a climate that promoted an initially higher ma ss-loss rate. At the same lignin concentration, however, the mass-loss rate was significantly lower in drier and colder conditions, viz. cli matic conditions that promote a lower initial mass-loss rate. Neverthe less, at very high lignin concentrations that lignin clearly dominated over climate as a rate-regulating factor. A possible consequence of t his observation could be a higher rate of organic matter accumulation at sites that initially promote a high initial mass-loss rate for litt er than at sites with conditions that give lower initial rates, at lea st for a given species of litter.