Carbon stocks and micromorphology of organic matter in riparian soils of three high mountain ecosystems: Iztaccihuatl volcano

Abstract

Riparian soils are recognized as important regions of long-term carbon storage. However, different hydromorphological factors along riparian gradients, as well as land use, can influence the distribution and concentration of soil organic carbon (SOC). The objective of this study was to evaluate the concentrations of SOC in catenas of riparian soils and to characterize soil organic matter (SOM) at the micromorphological level in three riparian ecosystems of Iztaccihuatl volcano (grasslands, forests, and agricultural zone). At each site, disturbed and undisturbed samples were collected in soil profiles along a catenary perpendicular to the stream. In the laboratory, COS was determined in the fine soil fraction and soil organic matter (SOM) micromorphology was described in thin sections. COS varied according to vegetation and land use (grassland 38.95 kg m-2 > forest 34.40 kg m-2 > agricultural zone 17.77 kg m-2). The highest values in COS occur in soils closer to the stream up to 68.92 kg m-2. SOM presents different organic residues and stages of decomposition and with higher abundance in the riparian subsoil where hydromorphism conditions limit its mineralization. Riparian soils have a greater potential to accumulate carbon (halophytic and autochthonous) than adjacent uplands. Likewise, degradation of these ecosystems has an impact on carbon storage and their role in climate change mitigation.