NITROGEN MINERALIZATION AND H+ TRANSFERS IN A SCOTS PINE (PINUS-SYLVESTRIS L) FOREST SOIL AS AFFECTED BY LIMING

H+ production due to N uptake in a mature Scots pine stand subjected to high NHS deposition was previously estimated to amount to approx. 2.2 kmol ha(-1) y(-1). The question whether H+ transfers related to N mineralization (ammonification and nitrification) offset or corroborate this proton production is investigated in the present research. To determine N mineralization, soil cores were used of which both ends were closed with layers of ion exchange resin (IER) to prevent influx and efflux of ions. The effect of liming on N mineralization and the resulting H+ production was investigated in 7 incubation periods of each ca. 8 wk. Because of its high mobility NO3 accumulated in both IER layers at the expense of that in the incubated forest floor and mineral soil. Net N mineralization in the soil cores as a whole amounted to 40 and 77 kg N ha(-1) in 384 d in the control and limed plots, respectively. In both treatments ca. 65% of mineralized N was nitrified. H+ production due to N mineralization amounted to approx. 1.2 kmol ha(-1) y(-1) in the control and limed plots. Liming reduced the amount of C in the forest floor, but not forest floor mass, because of an increased mixing with mineral particles.