Human influence on organic carbon fractions down the soil profile? - Dr Eleanor Hobley

Wednesday 22nd July 2015

We investigated the stability of whole profile soil organic carbon (SOC) based upon three mid-infrared predicted fractions – particulate organic carbon (POC), humus organic carbon (HOC) and resistant organic carbon (ROC) – at 100 sites across Eastern Australia. Our aim was to identify the controls on SOC stability down the whole soil profile, in particular relating to climate, site and human influences. To do this we used three data-mining algorithms (randomForests, gradient boosting machines and multiplicative adaptive regression splines) to identify and assess the controls on the relative proportions of the three fractions down the soil profile. Depth was the key control on all three fractions, with the proportion of POC decreasing, and the proportion of HOC carbon increasing with increasing depth. SOC was strongly linked with POC, suggesting that the soils in the region are input driven. HOC and ROC were controlled additionally by climate and soil physico-chemical properties, with SOC being less important to these fractions. Human influences (land-use and management) were not important to the fractions, implying that the controls humans can exert on SOC stability in these environments may be limited.