Dynamics of Soil Organic Carbon and Total Nitrogen in Particulate and Mineral-Associated Organic Matter Fractions under Different Continuous Land Use Patterns Across Europe

Abstract

Soil organic matter (SOM) fractions have a strong influence on biogeochemical cycles and carbon sequestration. However, land use practices significantly affect the distribution of SOM fractions by altering soil's carbon stabilization mechanisms. Hence, a comprehensive understanding is essential about the responses of carbon and nitrogen content in particulate organic matter (POM) and mineral-associated organic matter (MAOM) under different land uses. In this study, we aimed to study the distribution and changes of particulate organic carbon (POC), mineral-associated organic carbon (MAOC), nitrogen in particulate organic matter (NPOM), and nitrogen in mineral-associated organic matter (NMAOM) under three different land uses (cropland, grassland, and woodland) that remained same from 2009 to 2018. The European Land Use/Land Cover Area Frame Survey (LUCAS) topsoil database of 2018 containing SOM physical fractionation was used for predicting the POC, MAOC, NPOM, and NMAOM for the remaining samples by machine-learning approach. The results indicated that soils with less disturbances (e.g. grassland and woodland) had higher POC in both years compared to croplands. Also, the higher MAOC and NMAOM in grassland in both years dictated grassland's higher capacity to store stable forms of OC and N; however, the changes (from 2009 to 2018) of C and N in mineral contents in grassland were lesser than woodland soil, which could be due to the faster decomposition of POC and limited MAOC formation in grassland. This investigation justifies that land use practices can influence the stability of carbon pools and sequestration capacity by enhancing the amount of MAOM. However, the inclusion of soil microbial activities and their impacts on the stability and transformation of POM and MAOM in future researches might improve the understanding of the C and N cycle in these fractions even more.