Effects of liming and nitrogen fertilization on emissions of CO₂ and N₂O from a temperate forest

Abstract

Fluxes of N 2 O and CO 2 were measured simultaneously in control, N ‐fertilized, and limed plots in a 145‐year‐old beech stand in the Solling area in Germany using an automated chamber method. The N ‐fertilized plot received annually 140 kg of nitrogen as NH 4 SO 4 since 1982; the limed plot was treated with 30 t/ha of dolomitic limestone once in 1982. On all plots, fluxes of N 2 O and CO 2 underwent strong diel, daily, and seasonal variations. For the control plot, N 2 O and CO 2 effluxes averaged about 1 mg N/m 2 /d and 2.9 g CO 2 /m 2 /d from October until May and 3 mg N/m 2 /d and 4.5 g CO 2 /m 2 /d from May until September. Annual fluxes for N 2 O and CO 2 were 5.6 kg N/ha/yr and to 3.2 t C/ha/yr, respectively. Nitrogen saturation of the system due to high rates of N deposition for several decades may be responsible for the high N 2 O losses. Liming drastically reduced the N 2 O emission to 1.5 kg N/ha/yr and increased the CO 2 emission to 4.1 t C/ha/yr, 5 years after the treatment. Changes in N 2 O/N 2 ratios are assumed to be the reason for the lower N 2 O emission. Fertilization increased the N 2 O emission, resulting in 7.8 kg N/ha/yr, whereas the effect on CO 2 emission with 3.8 t C/ha/yr was less pronounced.