Decomposition of Needle Litter in Pinus contorta and Pinus sylvestris Monocultures-a Comparison

A comparison was made for chemical composition and mass-loss rates between needle litters from Scots pine and lodgepole pine during a four-year period. Initial chemical composition differed. Thus lodgepole pine needle litter had higher concentrations of sulfuric-acid lignin, phosphorus, magnesium and manganese, whereas Scots pine needles were richer in soluble substances. No difference between species was noted in concentrations of nitrogen, calcium and potassium. In the early stages of decomposition (<1 yr and <30% mass loss) Scots pine needles decomposed faster than those of lodgepole pine (p<0.001); whereas in the later stages (>300 days) there was no difference in the decomposition rate. Combining both species, mass-loss rates were positively correlated to concentrations of water solubles and nitrogen, and negatively correlated to those of lignin. Mass-loss rate was correlated to phosphorus concentrations only within species. For lodgepole pine needles the early phase of decomposition appeared to be considerably shorter than for those of Scots pine. In later stages mass-loss rates were negatively correlated to concentrations of lignin for both individual and combined litter types. However, at the same concentration of lignin, mass loss and lignin loss were faster in lodgepole pine needles than in those of Scots pine.