Effects of land use type and incubation temperature on greenhouse gas emissions from Chinese and Canadian soils

Abstract

Land use type is an important factor influencing greenhouse gas emissions from soils, but the mechanisms involved in affecting potential greenhouse gas (GHG) emissions in different land use systems are poorly understood. Since the northern regions of Canada and China are characterized by cool growing seasons, GHG emissions under low temperatures are important for our understanding of how soil temperature affects soil C and N turnover processes and associated greenhouse gas emissions in cool temperate regions. Therefore, we investigated the effects of temperature on the emission of N2O, CO2, and CH4 from typical forest and grassland soils from China and Canada. The soils were incubated in the laboratory at 10°C and 15°C under aerobic conditions for 15 days. The results showed that land use type had a large impact on greenhouse gas emissions. The N2O emissions were significantly higher in grassland than in forest soils, while CO2 emissions were higher in forest than in grassland soils. Grassland soils were weak sources of CH4 emission, while forest soils were weak sinks of atmospheric CH4. The global warming potential of forest soils was significantly greater than that of grassland soils. Soil pH, C/N ratio, and soluble organic carbon concentrations and clay content were dominant factors influencing the emissions of N2O and CO2, respectively. Increasing temperature from 10°C to 15°C had no effects on CH4 flux, but significantly increased N2O emissions for all studied soils. The same pronounced effect was also found for CO2 emission from forest soils. Indications from this study are that the effects of land use type on the source–sink relationship and rates of GHG emissions should be taken into consideration when planning management strategies for mitigation of greenhouse gas emissions in the studied region, and temperature changes must be taken into account when scaling up point- or plot-based N2O and CO2 flux data to the landscape level due to large spatial and temporal variations of temperature that exist in the field. The reader is cautioned about the limitation with incubation studies on a limited number of samples/locations, and care need to be exercised to extrapolate the result to field conditions.