Soil carbon storage and stabilisation in andic soils: A review

• SOM-stabilisation and -destabilisation in andic soils are controlled by soil pH.
• NMR spectra in deep andic soils revealed important contribution of alkyl C.
• Microbial-derived products rather charred materials are stabilised in andic soils.
• Al and Fe oxides are the main stabilising agents in andic soils.
• A metal:C ratio of 0.18 is the upper limit by SOM-complex formation in andic soils.

Andic soils contain a large amount of stabilised soil organic matter (SOM). The present study aims to review and integrate the determining factors and mechanisms of SOM stabilisation in andic compared with other (non-andic) soil types. We have reviewed recent literature regarding the nature of SOM and its stabilisation processes in the top- and sub-soil to address and discuss the interaction between the SOM and the mineral phase. The carbon (C) storage capacity by the metal-humus-complex formation of volcanic soils is also evaluated. The most important stabilisation processes are related to the incorporation and decomposition of microbial-derived C along with the changing C storage capacity with increasing soil development. The priming and destabilisation of adsorbed SOM are crucial mechanisms influencing the soil C sequestration in subsoils. The C storage capacity of andic soils was closely related to the Na-pyrophosphate extractable Al and Fe. The upper boundary for SOM saturation with Al and Fe was a molar metal:C ratio of 0.18. The influence of climate, mineralogy and soil disturbances on the SOM storage capacity of andic soils also require further attention.