Spatial distribution of fine-roots in boreal forests in eastern Sweden

Investigations were carried out in six forest types in areas surrounding two Swedish nuclear power plants (Forsmark and Laxemar). The aim of the investigation was to determine the spatial distribution of fine-root biomass (live), necromass (dead) and standing crop (live + dead) and to test the use of the live/dead ratio as a vitality criterion. Soil cores were taken to depths with insignificant amounts of roots. The total amount of fine-root biomass (< 1 mm in diameter) of tree species in the soil profile was 267, 317 and 235 g m(-2) for the Forsmark and 137, 371 and 50 g m(-2) for the Laxemar sites. The related necromass was 119, 226 and 184 g m(-2) and 87, 245 and 271 g m(-2). The biomass in the humus layer was 47, 7 and 48% for the Forsmark and 34, 26 and 7% for the Laxemar sites, as a percentage of the total live + dead fine roots in the soil profile. The related necromass in the humus layer was 13, 2 and 30% for the Forsmark and 13, 2 and 28% for the Laxemar sites. The live/dead ratio decreased with depth for both tree- and field-layer species and seems to be a most powerful vitality criterion of fine roots.