Soil nitrogen mineralization and its sensitivity to temperature and moisture in temperate peatlands under different land-use management practices

The availability of soil nitrogen determines many functions of terrestrial ecosystems, in particular, primary plant productivity, which affects both the plant yield and carbon sequestration. Climate change will lead to shifts in soil temperature and moisture; therefore, to create a more accurate forecast of ecosystem sustainability, it is important to understand how these indicators control nitrogen mineralization in soils. We studied the effect of temperature and moisture on the net ammonification and net nitrification processes in temperate peatlands of central Russia under 4 land-use types: regular plowing for 50 and 100 years, post-agrogenic reforestation for 50 years, and a near-pristine birch forest. During a laboratory incubation experiment, we found that net nitrogen mineralization was significant at all combinations of temperatures and moisture levels. Net nitrification was the main process for nitrogen mineralization, although net ammonification was also possible at low incubation temperatures. The highest rate of net mineralization was typical of forest peatlands, and the lowest rate was typical of arable sites, which were associated with the differences in the quantity, quality and regularity of the incoming plant litter. Despite significant differences in the rate of net nitrification between plots with different land-uses, the temperature sensitivity coefficient of this process was nearly the same for all peatlands and was close to 2; therefore, we did not find evidence of the effect of the organic matter quality on the temperature sensitivity of net nitrification. The moisture level also did not affect the temperature sensitivity of this process. In general, it was found that fluctuations in soil temperature and moisture with climate change will not cause a sharp increase in net nitrification in peatlands, which will prevent the soil from losing nitrogen with runoff or in the form of gaseous compounds, such as N2O.