Assessing soil degradation status in croplands: insights from the variations in soil particulate organic carbon fraction

Intensified soil use and management practices have led to serious soil degradation in the world’s croplands, compromising their ability to provide food and ecosystem services. Under the United Nations Sustainable Development Goals framework, “change in soil C stock” has been adopted as a key indicator to assess the degree and extent of cropland degradation. Among the underlying drivers that can cause soil C losses, reduced inputs of organic substrates, tillage-induced soil structural destabilization and erosion-associated lateral matter transfer are regarded as key processes that not only diminish the bulk C content, but also alter the soil C composition of functionally distinct fractions.

In this study, we attempt to analyze the relationship between soil degradation and soil C dynamics from a "beyond bulk” perspective. We selected two study sites, one in Northeast China and one in the Belgian Loam Belt, that share similar bulk soil C content, soil texture and parent materials, but contrasting degrees of soil degradation at regional scale. We will present results on (i) the response of soil aggregate stability, as a measure of soil degradation, to varying bulk C content, as well as to particulate and mineral-associated organic C fractions; (ii) how varied organic inputs and soil erosion intensity could affect the fraction of soil particulate organic carbon that has important control over the level of aggregate stability.