Gross ammonification and C mineralization was much larger in the beech than in the spruce soil, while gross nitrification was in the same order of magnitude. Gross ammonification, nitrification and C
mineralization almost ceased at 4 C, but already increased at 1 C. Net ammonification in Oi/Oe
horizons was low at 4 and 1 C and increased strongly between þ2 and þ8 C. Net nitrification was
low in both soils, but increased in the spruce soil at temperatures >2 C whereas no temperature
response occurred in the beech soil.
Apparent Q10 values of gross ammonification and C mineralization in the temperature range of 4 to þ8 C were in the range of 3e18. Q10 were lowest in soil horizons of low substrate quality. The ratio of C mineralization to gross ammonification varied between 0.5 and 2.9, suggesting preferential mineralization of N rich organic substrates or rapid turnover of the N pool in microbial biomass. Rising winter
temperatures might have substantial effects on net N mineralization, but effects decrease with soil depth, likely due to decreasing substrate quality of soil organic matter.
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