Browsing by Author "Wilson, B"

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    Land-use affects the radiocarbon age, storage and depth distribution of soil organic carbon in Eastern Australia
    (European Geosciences Union, 2015-01-01) Hobley, E; Wilson, B; Hua, Q
    Land-use has been shown to affect soil organic carbon (SOC) storage, with natural systems generally storing larger quantities of SOC than anthropogenically managed systems in surface soils. However, these effects are often difficult to detect deeper in the soil profile. Little is known regarding the effects of land-use on the radiocarbon age of SOC, both at the surface and deeper in the soil profile. We investigated the storage, radiocarbon content and depth distribution of soil organic carbon from across the state of NSW, Australia. A total of 100 profiles were analysed for total SOC concentration at numerous depths (up to 1 m) and a machine learning approach implementing tree ensemble methods was used to identify the key drivers of SOC depth distribution. Surface SOC storage was strongly associated with climate (predominately precipitation, to a lesser degree relative humidity and temperature), whereas SOC depth distribution was predominately influenced by land-use, soil type and to a lesser extent temperature. A subset of 12 soil profiles from a range of climate zones were analysed for radiocarbon content with a view to contrasting three land-use systems: natural, cleared/grazed and cropped. Radiocarbon content was affected strongly by land-use, with effects most pronounced at depth. Native systems appeared to have the youngest carbon throughout the profile, with cropped and grazed systems having older SOC. Radiocarbon content was also strongly associated with SOC content. Our results indicate that natural systems act as a carbon pump into the soil, injecting young, fresh organic carbon which is vertically distributed throughout the profile. In contrast, managed systems are deprived of this input and are depleted in SOC at all depths, leading to higher radiocarbon ages throughout the profile. © Author(s) 2015.
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    Relationship between land-use, soil organic carbon depth distribution and radiocarbon age New South Wales, Australia
    (University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-09) Hobley, E; Wilson, B; Hua, Q
    Not provided to ANSTO Library.
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    Soil organic carbon in eastern Australia
    (American Geophysical Union (AGU), 2016-12-14) Hobley, E; Baldock, JA; Hua, Q; Wilson, B
    We investigated the drivers of SOC dynamics and depth distribution across eastern Australia using laboratory analyses (CN, fractionation, radiocarbon) coupled with modelling and machine learning. At over 1400 sites, surface SOC storage was driven by precipitation, whereas SOC depth distribution (0-30 cm) was influenced by land-use. Based upon these findings, 100 sites were selected for profile analysis (up to 1 m) of SOC and its component fractions - particulate (POC), humus (HOC) and resistant (ROC) organic carbon. Profile SOC content was modelled using an exponential model describing surface SOC content, SOC depth distribution and residual SOC at depth and the drivers of these parameters investigated via machine learning. Corroborating previous findings, surface SOC content was highly influenced by rainfall, whereas SOC depth distribution was influenced by land-use. At depth, site properties were the most important predictors of SOC. Cropped sites had significantly lower SOC content than native and grazed sites at depth, indicating that land-use influences SOC content throughout the profile. The machine learning algorithms identified depth as the key control on the proportion of all three fractions down the profile: POC decreased whereas HOC increased with increasing depth. POC was strongly linked with total SOC but HOC and ROC were driven more by climate and soil physico-chemical properties. Human influences (land-use and management) were not important to the fractions, implying that the controls humans can exert on SOC stability may be limited. A subset of 12 soil profiles was analysed for 14C. Radiocarbon content was affected strongly by land-use, with effects most pronounced at depth. Native systems had the youngest carbon down the profile, cropped systems had the oldest SOC. All fractions reacted to land-use change down the soil profile, indicating a lack of stability when the whole profile is viewed. These results indicate that natural systems act as a carbon pump into the soil, injecting young, fresh organic carbon down the entire profile. In contrast, managed systems are deprived of this input and are depleted in SOC at all depths. Our results strongly suggest that SOC storage in the region is input driven. © AGU 2016