CHANGES IN ROOT BIOMASS AFTER WATER-LEVEL DRAWDOWN ON PINE MIRES IN SOUTHERN FINLAND

Changes in living and dead root biomass were monitored in the successi on created by drainage for forestry on six sites from undrained to 55- yr-old drained tall-sedge pine mires in southern Finland. This was don e to evaluate the role of root biomass in carbon cycling in drained pe atland ecosystems. The total living Scots pine (Pinus sylvestris L.) r oot and stump biomass varied from 190 g m(2) on an undrained site to 3 060 g m(2) on the oldest drained site. The pine fine root biomass reac hed the maximum level within 22 yrs of drainage with a pine stand volu me of 81 m(3) ha(-1). The pine coarse root and stump biomass increased with the age of the stand, comprising 90% of the total living root bi omass on the 55-yr-old drained site. The drainage also increased the r oot biomass of field layer species; however, the roots of sedges were replaced by those of shrubs and trees. The dead fine root biomass was smallest on the two oldest drained sites, which could have resulted fr om a higher decomposition rate after improved aeration in the surface peat.