Variation in the amount and quality of litterfall in a Pinus sylvestris L. stand growing on a bog

Abstract

The amount and nutrient content of the above-ground litterfall was followed for 9 years in an unfertilized, PKMgB and NPKMgB fertilized Scots pine stand growing on a drained ombrotrophic bog in eastern Finland. The annual litterfall on unfertilized plots was 1995 kg ha-1, of which needles accounted for 74%. The effective temperature sum (threshold value + 5°C) explained 99% of the annual variation in the amount of needle litterfall when the data from one atypical year were excluded from the analysis. Nutrient concentrations were, except for Fe, higher in needle litter than in the other litterfall fractions. Nitrogen, P and K concentrations were low in autumn, and those of Ca and Mn high, possibly owing to variation in the mobility of elements during senescence. The annual litterfall input of N to the soil was 12.4 kg ha-1, and the corresponding values for P and K were 0.08 kg ha-1 and 1.81 kg ha-1, respectively. Fertilization reduced needle litterfall in the first year after treatment, but had no effect thereafter. The amount of other litterfall fractions was not affected by fertilization in any of the 9 years of the study. Nitrogen, P, K and B concentrations increased in the needle litter after both fertilization treatments. The results indicate long-term cycling of fertilizer nutrients on the site.