Fine root biomass of Scots pine stands differing in age and soil fertilityin southern Finland

The biomass of small and large fine roots (less than or equal to 2 mm and 2 -5 mm in diameter, respectively) in mineral soils of southern Finland was c ompared with estimated foliage biomass in the same stands. Study material w as collected from stands differing in site fertility and age. The humus lay er was deeper at the more fertile sites than at the less fertile sites. Fin e root density was greater in humus than in mineral soil, and the fine root density in mineral and humus layers was greater at the less fertile sites than at the more fertile sites. Although the amount of fine root biomass wa s not correlated with any commonly recorded stand characteristic, small fin e root biomass was proportional to foliage biomass for both site types. The coefficient of proportionality was larger for the less fertile sites than for the more fertile sites, supporting the theory of functional balance. A similar relationship could not be established for the large fine roots. A t rend of increasing fine root:needle mass ratio with stand age was observed for stands on the less fertile sites.