Fine root dynamics in a Norway spruce forest (Picea abies (L.) Karst) in eastern Sweden

The annual dynamics of live and dead fine roots for trees and the field layer species and live/dead ratios were investigated at a coniferous fern forest (Picea abies L. Karts) in Sweden. Our methods of estimating the average amount of fine roots involved the periodic sampling of fine roots in sequential cores on four sampling occasions. The highest live/dead ratio was found in the upper part of the humus layer for both tree and field-layer species and decreased with depth. Most tree fine roots on the four sampling occasions were found in the mineral soil horizon, where 86, 81, 85 and 89% of < 1 mm and 89, 88, 89 and 92% of < 2 mm diameter of the total amounts of live fine roots in the soil profile were found. The mean amounts of live fine roots of tree species for the total soil profile on the four sampling occasions was 317, 150, 139 and 248 g m(-2) for < 1 mm and 410, 225, 224 and 351 g m(-2) for < 2 mm diameter fine roots. The related amount of dead fine roots was 226, 321, 176 and 299 g m(-2) and 294, 424, 282 and 381 g m(-2), respectively. Average amounts of live and dead fine-roots and live/dead ratios from other Picea abies forest ecosystems were within the range of our estimates. The production of fine roots, < 1 and < 2 mm in diameter, estimated from the annual increments in live fine roots, was 207 and 303 g m(-2). The related accumulation of dead fine roots was 257 and 345 g m(-2), The turnover rate of tree fine roots < 1 mm in diameter in the total soil profile amounted to 0.7 yr(-1) for live and 0.8 yr(-1) for dead fine roots. The related turnover rates for tree fine roots < 2 mm were 0.4 yr(-1) and 0.7 yr(-1). Our data, although based on minimum estimates of the annual fluxes of live and dead fine roots, suggests a carbon flow to the forest soil from dead fine-roots even more substantial than from the needle litter fall. Fine-root data from several Picea abies forest ecosystems, suggest high turnover rates of both live and dead tree fine-roots.