Mr Jinquan Li1,2, Dr Ming Nie2, Dr Elise Pendall1
1Western Sydney University, Sydney, Australia, 2Fudan University, Shanghai, China
Greenhouse gas (GHG) fluxes from soils play crucial roles in regulating the Earth’s surface temperature. However, our understanding of the effect of land-cover and soil depth on the potential GHG fluxes and their temperature sensitivities (Q10) is limited, which consequently increases the uncertainty to predict GHG exchange between soils and the atmosphere. Here we present an incubation study of soils with contrasting characteristics from three land-cover types (wetland, grassland, and forest) and soil depths (0–10, 10–20, and 20–30 cm) from the Cumberland Plain near Sydney, Australia. Overall, potential GHG fluxes and their Q10 values differed significantly among land-cover types and soil depths. CO2 and N2O emissions were highest in wetland followed by grassland and forest soils, and they decreased with soil depth. In contrast, CH4 uptake was highest in grassland followed by forest and wetland soils, and it increased with soil depth. Combining the three major GHGs, the global warming potential in wetland was higher than that in grassland and forest. Moreover, Q10 values of CO2 and N2O emissions were highest in wetland and lowest in forest, while Q10 value of CH4 uptake showed the opposite pattern. Q10 values of GHG fluxes all increased with soil depth. Across different land-cover types and soil depths, GHG flux rates were controlled by substrate quantity and quality; Q10 values of CO2 and N2O were controlled by soil texture, while substrate quantity and quality affected Q10 value of CH4. These results suggest that the large carbon stocks in wetland soils are vulnerable to loss and thus may amplify climate warming; upland soils are crucial CH4 sinks and thus potentially mitigate climate change. In addition, the greater temperature sensitivities of potential GHG fluxes in subsoil should be accounted for in carbon and nitrogen cycling models.
Elise Pendall is Professor of Soil Science at Western Sydney University and serves as Theme Leader for the Soil Biology and Genomics research group at Hawkesbury Institute for the Environment. She studies responses of biogeochemical cycling to climate change, ecological disturbances and land management. She uses field and lab experiments and modelling to evaluate linkages between aboveground and belowground ecosystem components and how they regulate carbon, water and nutrient cycling in forests, grasslands, and crops.