Stabilization of soil organic carbon in microaggregates under contrasting land uses in Alfisols and Oxisols

Abstract

Soil microaggregates play a key role in stabilization of soil organic carbon (SOC) and influence dynamics of SOC in terrestrial ecosystem. SOC can be stabilized in microaggregates through physical, physico-chemical and biochemical protection mechanisms. The study of SOC stabilization mechanisms poses a number of challenges. Firstly, all these mechanisms operate simultaneously in nature and, secondly there are significant methodological constraints of separating SOC fractions with different turnover times. Moreover, the importance of various stabilization mechanisms varies considerably in different climates, soil types and management systems. The overarching hypotheses of the study were (i) physical protection of SOC is a dominant SOC stabilization mechanism in soil microaggregates over physico-chemical protection (ii) land use and soil type determines the relative importance of different stabilization mechanisms. The specific objectives of the research work were to investigate (i) the SOC stabilization in water stable aggregates (ii) microbial decomposition of SOC and its relationship with chemical composition of SOC and pore geometry of microaggregates (iii) the mean residence time of SOC in microaggregates and (iv) the influence of land uses on the distribution and stabilization of SOC in microaggregates. Two soil types were investigated, Alfisols and Oxisols, both located on the Northern Tablelands, NSW, Australia.