Temperature and soil moisture dependence of N mineralization in intact soil cores

The combined effect of temperature (10, 20 and 25°C) and soil moisture (30, 200 and 1700 kPa) on net N mineralization was examined using undisturbed soil samples in laboratory incubations. Simulations with a mechanistic model of soil anaerobiosis were made to assess the effect of temperature and soil moisture on soil aeration, which also affects N mineralization. The rate of net N mineralization showed a high variability, and 57% of this variation was associated with factors other than temperature and moisture. N mineralization was more responsive to temperature than it was to moisture. Two models based on the Arrhenius and the Q10 functions described well the experimental data and indicated a temperature-moisture interaction affecting N mineralization. When the measured rates were corrected to take into account only the calculated aerobic fraction of the soil, a good fit with both models was still obtained. This implies that the Arrhenius and the Q10 functions do not discriminate between the direct effect of temperature on N mineralization and the indirect effect associated to soil aeration. The use of these functions to describe N mineralization in undisturbed samples requires information on the aeration status of the soil.