Depth distribution of SOM stock in fine-textured soils of Hungary

The soil cover of the world stores more carbon than that present in biomass and in the atmosphere, so the depth and distribution of soil organic matter (SOM) might be important in point of carbon sequestration and climate change mitigation. Texture, among several other factors, plays an important role in the distribution of SOM. Most national and the main international soil classification systems (Soil Taxonomy, World Reference Base for Soil Resources) have a separate unit for high clay content soils on the highest level of classification, as Vertisols. Due to the high swelling clay content, these soils open deep cracks when they are dry. During the process called “pedoturbation”, the high SOM content surface material falls into the cracks, where it accumulates and mixes with subsoil, and enhances the accumulation of SOM in great depth. Although the effect of texture on the stabilization, distribution and properties of SOM have been investigated, only little information is available on SOM distribution in high clay content soils. The objective of the present study was to analyze the vertical distribution of SOM in high clay content soils of Hungary. Our results, based on the investigations of the Hungarian TIM database supported the hypothesis that high clay content soils store significantly more SOM and in greater depth than other soils under similar climatic conditions