N2O losses result in underestimation of in situ determinations of net N mineralization

Closed tubes are commonly used for soil incubations in the field to determine net nitrogen mineralization (NNM). This study showed that gaseous losses of N in the form of N2O during this type of field incubations can lead to substantial underestimations of NNM. NNM was not underestimated in a 146-year-old beech stand, but underestimated by 15% in a gap of the same stand, by 6% in a limed stand and by 80% in a limed gap. Compared to closed chamber measurements, N2O output of the incubated tubes was on average 6, 90, 300 and 570% higher in the stand, the gap, the limed stand and the limed gap, respectively. CO2 respiration was enhanced in all tubes between 80% (stand) and 260% (gap), indicating a higher microbial activity after insertion of the tubes into the soil.