Complementary effects of sorption and biochemical processing of dissolved organic matter for emerging structure formation controlled by soil texture

Abstract

BackgroundPercolating dissolved organic matter (DOM) from the topsoil is considered the main source of subsoil organic carbon (OC) in temperate soils, but knowledge about its influence on OC storage and structure‐forming processes is limited.AimsWe conducted a 30‐day incubation experiment with artificial soils to study the effects of percolating DOM and soil texture on OC turnover and initial structure formation.MethodsArtificial soils with contrasting texture, but identical mineral composition, were used to mimic subsoil conditions, where mineral surfaces free of OM come into contact with percolating DOM. After the incubation, we assessed the solution exchange, OM covers on minerals, microbial community and OC turnover, and aggregate formation and stability.ResultsA higher sand content caused a lower porosity, accompanied by a lower moisture content. In contrast, the OC retention (21% of the OC input), microbial activity, and community size were unaffected by soil texture. The OM covered 10% of the mineral surfaces within an otherwise OC‐free mineral matrix. The formation of large, water‐stable aggregates occurred in all soils, but was pronounced in the clay‐rich soils (58% mass contribution), which also supported a higher mechanical stability of the aggregates.ConclusionsThe initial retention and microbial mineralization of DOM are decoupled from pore sizes and soil solution exchange but are driven by the mineral composition and OC input. The biochemical processing of the percolating DOM can induce large aggregates. Here, the presence of fine mineral particles enhances the formation and mechanical stability of the aggregates, irrespective of their surface charge or sorptive properties.

Structure–function co‐evolution during pedogenesis—Microaggregate development and turnover in soils

“…These were complemented by experimental pedogenesis studies (cf. Bucka et al, 2019;Lehmann et al, 2018;Pronk et al, 2012;Ritschel et al, 2023): The dynamic relocation experiment explored the stability of microaggregates against physicochemical stress under dynamic flow conditions, and the nuclei-framing experiment examined the aggregate formation processes without mechanical disturbance (e.g., Bucka et al, 2019Bucka et al, , 2024.…”

The “extra pinch” of pseudosand to enhance tropical biogeochemical processes understanding

“…Consequently, it is not surprising that the approach to identify and characterize aggregates and their sizes could appear vague or not very systematic (Baveye, 2021; Letey, 1991; Young et al., 2001). But even if an exact determination of where or when aggregates originate and how they evolve or stabilize between snapshots is not feasible, we can still identify the mechanisms and processes that lead to (dis)aggregation (e.g., Bucka et al., 2024; Martin et al., 1955; Roosch et al., 2024) and derive the impact of aggregates on fluxes of energy and matter.…”