Temperature sensitivity of soil carbon and nitrogen mineralization: impacts of nitrogen species and land use type

Climate warming, nitrogen (N) deposition and land use change are some of the drivers affecting ecosystem processes such as soil carbon (C) and N dynamics, yet the interactive effects of those drivers on ecosystem processes are poorly understood. This study aimed to understand mechanisms of interactive effects of temperature, form of N deposition and land use type on soil C and N mineralization. We studied, in a laboratory incubation experiment, the effects of temperature (15 vs. 25 A degrees C) and species of N deposition (NH4 (+)-N vs. NO3 (-)-N) on soil CO2 efflux, dissolved organic C (DOC) and N (DON), NH4 (+)-N, and NO3 (-)-N concentrations using intact soil columns collected from adjacent forest and grassland ecosystems in north-central Alberta. Temperature and land use type interacted to affect soil CO2 efflux, concentrations of DON, NH4 (+)-N and NO3 (-)-N in most measurement times, with the higher incubation temperature resulted in the higher CO2 efflux and NH4 (+)-N concentrations in forest soils and higher DON and NO3 (-)-N concentrations in grassland soils. Temperature and land use type affected the cumulative soil CO2 efflux, and DOC, DON, NH4 (+)-N and NO3 (-)-N concentrations. The form of N added or its interaction with the other two factors did not affect any of the C and N cycling parameters. Temperature and land use type were dominant factors affecting soil C loss, with the soil C in grassland soils more stable and resistant to temperature changes. The lack of short-term effects of the deposition of different N species on soil C and N mineralization suggest that maybe there was a threshold for the N effect to kick in and long-term experiments should be conducted to further elucidate the species of N deposition effects on soil C and N cycling in the studied systems.