Abstract
As regards chemical composition, foliar litter appears to be the most studied group of litter. The main organic litter compounds are cellulose, a group of hemicelluloses and lignin, the latter often measured as acid unhydrolyzable residue (AUR). In addition, there are several polymeric compounds including suberins, tannins, and cutins. Concentrations of the main nutrients vary heavily with litter species. For some species/genera (e.g., pine spp.), we may see that in newly shed litter concentrations of nitrogen (N), phosphorus (P), sulfur (S), and potassium (K) increase with increasing mean annual temperature (MAT) and actual evapotranspiration (AET), whereas manganese (Mn) in pine litter has been shown to decrease. For spruce (Picea) needle litter, no such effect of climate has been observed. Still, an increase in N concentration with MAT/AET appears to be a general phenomenon covering most investigated species. AUR concentration has been positively related to litter N concentration. It appears that AUR concentrations are higher in coniferous litter than in broadleaf, whereas those for N are higher in broadleaf litter.