Greenhouse gas emissions in saline, waterlogged soils of Western Australia
Mann, S., Kalleshwari, R.K., Bell, R.W. and Waddell, B. (2012) Greenhouse gas emissions in saline, waterlogged soils of Western Australia. In: Eurosoil 2012: Soil Science for the Benefit of Mankind and Environment. 4th International Congress of the European Confederation of Soil Science Societies (ECSSS), 2 - 6 July, Bari, Italy.
Patterns of greenhouse gas emissions from saline soils are difficult to predict since low biological productivity combined with variable waterlogging regimes may cause contrasting effects on the emissions of CO2, N2O, CH4 and C2H2. Moreover, there is a need to understand the effect of revegetation in recovering salinised/sodic soils, sequestration of soil C and thereby increase in biological activity and its effect on patterns of GHG emissions. An incubation study was conducted to examine the effect of organic material addition (salt bush leaf incorporated at 0 or 7.5 t ha-1) to a saline soil (EC 1:5 58.7 mS cm-1) while maintaining water levels at 0 (complete saturation), 10 cm or 15 cm below the soil surface. Low rates of CO2 emission were found without organic matter addition although initially the highest rates were found when water level was 10 cm below the soil surface. With OM addition there was an immediate and sustained increase in CO2 emission especially when the water level was at 10 or 15 cm depth. Acetylene (C2H2) emissions were 1-2 orders of magnitude lower than those of CO2, but generally followed the same pattern of response. Rates of C2H2 emission were very low in unamended soil but six- to eightfold higher with added OM. Methane emissions were lower, being 1-2 orders of magnitude lower than that of acetylene. Addition of organic matter only intermittently stimulated emission of CH4 with no significant effect of water level. In unamended soil, low rates of N2O emission were recorded. Addition of organic material increased the emission of N2O during the first 2-3 days after addition with the cumulative loss being highest with water level at 15 cm. Decreases in extractable NH4-N and NO3-N levels were recorded in soils amended with organic material and also in unamended soils after 15 days of incubation. Addition of organic material increased soil microbial biomass carbon, and organic carbon status increased after 15 days of incubation at varying water levels. Lack of C substrate was the dominant limitation for greenhouse gas emissions on saline soil, overriding the effects of soil water regime. The greenhouse gas emissions from the saline soils were dominated by CO2 loss and were dependent on the input of decomposable C. These results suggest that revegetation by increasing available C substrate on saline soils may increase their greenhouse gas emissions.
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|Murdoch Affiliation:||School of Environmental Science|
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