Figure 9. Conceptual model of a hypothesis to explain the higher δ15N of soils from hot and/or dry ecosystems.
Hot and/or dry ecosystems might not have a greater proportion N lost to fractionating (gradient arrow) vs. non-fractionating (solid arrow) losses. Note, arrows not to scale. Instead, as a result of having organic matter that has been decomposed to a greater degree and/or greater clay concentrations, soils from hot and/or dry ecosystems might simply have a greater proportion of their N in mineral-associated organic matter, which is enriched in 15N relative to non-mineral-associated organic matter.