LAUSR

Abstract Old-growth forests differ from managed forests by a generally higher biodiversity, larger carbon stores, and greater heterogeneity of aboveground structures. It is not known whether the aboveground structural diversity of old-growth forests is mirrored in root system structure, e.g. by greater root biomass, the occurrence of root gaps, and a different fine root morphology. We studied the fine root system of beech (roots Across the three primeval forest stages, fine root biomass tended to peak in the optimum stage, but the difference was not significant, and no alteration in fine root morphology across the stages was detected. Fine root necromass increased significantly from the initial to the terminal stage, pointing at higher fine root mortality and/or reduced root decomposition in forest patches with many senescent trees and canopy gaps. Yet, soil fertility did not decrease toward the terminal stage of forest development. From the fine root biomass data, no root gaps could be detected in the terminal stage, perhaps due to rapid gap colonization by beech saplings. We conclude that the structural differences between the fine root systems of beech primeval and production forest were relatively small. Canopy heterogeneity seems to be a less important factor determining root distribution in the primeval forest than soil heterogeneity, which can be high in production forests as well.