The applicability of commonly-used tracers in identifying eroded organic matter sources

Abstract

Tracing decomposition of organic carbon sources can balance carbon budget and reduce soil erosion targetedly. However, tracers may provide inaccurate source information, possibly due to the instability of organic matter under different land use types. Little is known about which stable tracer to choose based on different erosion scenarios. We, therefore, evaluated the availability of three commonly-used tracers techniques (i.e., bulk stable isotopes, fluorescence proxies and stoichiometric ratios) under different mixed end-members (i.e., Woodland, arable land and grassland) via a laboratory-scale controlled experiment. Combining fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC), Bayesian isotope mixing model and three evaluation criteria. Bulk stable isotopes (δ13C, δ15N) were considered to be the most suitable tracers for terrestrial organic matter sources tracing (Most of the R2 > 0.85, % difference < 10%), especially under Arable land-Woodland (A-W) mixed end-member, followed by traditional tracers (C/N, DOC). Unfortunately, the fluorescent indices were not suitable for terrestrial organic matter sources tracing, due to the similarities between different terrestrial organic matter sources, especially under Grassland-Woodland (G-W) mixed end-member (Most of the P-value > 0.05, % difference > 10%). Our results recommend that when selecting a tracer, not only the stability of the tracer should be considered, but also the difference among eroded organic matter sources. This study provides new insights into the validation of commonly-used tracers in identifying eroded organic matter sources accurately.