Characterization of dissolved organic matter distribution in forestland and farmland of mollisol based on untargeted metabolomics

Characterization of mollisol soil DOM by untargeted metabolomics is possible. The polarity of the extractants determines the polarity of the extracted DOM. Land use patterns affect the biological functions and co-network interaction of DOM. Mollisol soil is a major contributor to food production. Clarification of the molecular characteristics of dissolved organic matter (DOM) will contribute to the overall understanding and management of mollisol soil. However, the complexity of DOM poses a challenge to understanding its molecular characteristics. In this study, we investigated the molecular characteristics of DOM (< 1 000 Da) in mollisol soils with different soil use patterns (forestland and dryland) based on untargeted metabolomics. Here, we confirmed the feasibility of untargeted metabolomics for the molecular characterization of DOM in mollisol soils. DOM in forestland is mainly derived from plant metabolites, and DOM can perform more biological functions. However, DOM in dryland has complex composition and has powerful co-occurrence network interactions due to human activities. Water has better extraction efficiency for polar DOM, while organic reagents can efficiently extract lipid-like DOM, but the polarity of the extractant has less influence on the DOM than the soil physicochemical properties. Meanwhile, 14-dihydroxyzeatin screened based on metabolomics can be used as a potential indicator for corn land. Therefore, untargeted metabolomics can be an effective method to characterize the DOM molecules of mollisol soil, which provides new insights for management of mollisol soil and sustainable agricultural development.