Below- and above-ground biomass, production and nitrogen use in Scots pine stands in eastern Finland

Abstract

The below- and above-ground biomass and the annual biomass production of sapling (15-year-old), pole stage (35-year-old) and mature (100-year-old) Scots pine ( Pinus sylvestris L.) stands were studied in eastern Finland. The fine-root (diameter<2 mm) biomass (including mycorrhizal root tips), necromass and biomass production were determined for the organic layer and the upper 30 cm mineral soil layer by soil core samplings. The biomass and the annual production of needles, cones, stemwood and stembark, branches (wood and bark), and coarse-roots were calculated for the whole stand using biomass measurements of different components of felled sample trees, and measurements of the tree stand. Below-ground biomass accounted for 25, 21 and 13% of the stand biomass in the sapling, pole stage and mature stands; 15, 7 and 2% consisting of fine-roots, respectively. The mean fine-root biomass was 220, 357 and 259 g/m 2 in the sapling, pole stage and mature stands. The mean annual fine-root biomass production was 165, 775 and 860 g/m 2, corresponding to 43, 59 and 60% of the total stand biomass production in the sapling, pole stage and mature stands, respectively. Thus, even though the proportion of fine-roots of the total tree biomass was not large, their growth accounted for a major part of stand biomass production. Fine-roots annually used 0.9, 4.1 and 4.5 g N/m 2 for biomass production in the sapling, pole stage and mature stands, respectively. This accounted for 45–63% of the nitrogen used annually in total stand biomass production. Needle production accounted for 27–34%, and production of the woody components 9–21% of the nitrogen used annually in biomass production.