Earthworms as catalysts in the formation and stabilization of soil microbial necromass

Angst, Gerrit; Frouz, Jan; Groenigen, J.W. van; Scheu, Stefan; Kögel‐Knabner, Ingrid; Eisenhauer, Nico

doi:10.1111/gcb.16208

Cited by 40 publications

(15 citation statements)

References 112 publications

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“…Additionally, the wheat straw in the present study had low nutrient contents, which may further limit the contribution of earthworms to nutrient availability. Despite the weak earthworm effects on crop growth in present study, it is still important to promote and protect earthworm populations in agricultural systems, as they have been shown repeatedly to play a crucial role in maintaining soil functions, such as nutrient cycling, water infiltration, and soil aggregate and C stability through feeding, burrowing, and casting (Lavelle et al 1998 ; Coleman et al 2017 ; Angst et al 2022 ).…”

Section: Discussionmentioning

confidence: 82%

Climate-dependent plant responses to earthworms in two land-use types

Liu,

Eisenhauer,

Scheu

et al. 2023

Oecologia

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Plant nutrient uptake and productivity are driven by a multitude of factors that have been modified by human activities, like climate change and the activity of decomposers. However, interactive effects of climate change and key decomposer groups like earthworms have rarely been studied. In a field microcosm experiment, we investigated the effects of a mean future climate scenario with warming (+ 0.50 °C to + 0.62 °C) and altered precipitation (+ 10% in spring and autumn, − 20% in summer) and earthworms (anecic—two Lumbricus terrestris, endogeic—four Allolobophora chlorotica and both together within 10 cm diameter tubes) on plant biomass and stoichiometry in two land-use types (intensively used meadow and conventional farming). We found little evidence for earthworm effects on aboveground biomass. However, future climate increased above- (+40.9%) and belowground biomass (+44.7%) of grass communities, which was mainly driven by production of the dominant Festulolium species during non-summer drought periods, but decreased the aboveground biomass (− 36.9%) of winter wheat. Projected climate change and earthworms interactively affected the N content and C:N ratio of grasses. Earthworms enhanced the N content (+1.2%) thereby decreasing the C:N ratio (− 4.1%) in grasses, but only under ambient climate conditions. The future climate treatment generally decreased the N content of grasses (aboveground: − 1.1%, belowground: − 0.15%) and winter wheat (− 0.14%), resulting in an increase in C:N ratio of grasses (aboveground: + 4.2%, belowground: +6.3%) and wheat (+5.9%). Our results suggest that climate change diminishes the positive effects of earthworms on plant nutrient uptakes due to soil water deficit, especially during summer drought.

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Section: Discussionmentioning

confidence: 82%

Climate-dependent plant responses to earthworms in two land-use types

Liu,

Eisenhauer,

Scheu

et al. 2023

Oecologia

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show abstract

“…Additionally, the wheat straw in the present study had low nutrient contents, which may further limit the contribution of earthworms to nutrient availability. Despite the weak earthworm effects on crop growth in present study, it is still important to promote and protect earthworm populations in agricultural systems, as they have been shown repeatedly to play a crucial role in maintaining soil functions, such as nutrient cycling, water in ltration, and soil aggregate and C stability through feeding, burrowing, and casting (Lavelle et al 1998;Coleman et al 2017;Angst et al 2022).…”

Section: Earthworm Effectsmentioning

confidence: 86%

Climate-dependent plant responses to earthworms in two land-use types

Liu,

Eisenhauer,

Scheu

et al. 2023

Preprint

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Plant nutrient uptake and productivity are driven by a multitude of factors that have been modified by human activities, such as climate change and the activity of decomposers. However, interactive effects of climate change and key decomposer groups like earthworms have rarely been studied. In a field microcosm experiment we investigated the effects of a mean future climate scenario for the period between 2070 and 2100 in Germany with warming and altered precipitation and earthworms (anecic - Lumbricus terrestris, endogeic - Allolobophora chlorotica and both together) on plant biomass and stoichiometry in two contrasting land-use types (intensively-used meadow with four forage grass species and conventional farming). In contrast to previous studies we found little evidence for earthworm effects on aboveground biomass. However, future climate increased above- (+ 40.9%) and belowground biomass (+ 44.7%) of grass communities, which was mainly driven by production of the dominant Festulolium species during periods outside the projected summer drought, but slightly decreased the aboveground biomass (-36.9%) of winter wheat. Projected climate change and earthworms interactively affected the N content and C:N ratio of grasses. Earthworms enhanced the N content thereby decreasing the C:N ratio in grasses, but only under ambient climate conditions. The future climate treatment generally decreased the N content of grasses and winter wheat, resulting in an increase in plant C:N ratio. Our results suggest that climate change diminishes the positive effects of earthworms on plant nutrient uptakes due to soil water deficit, especially during summer drought.

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“…Mucus–mineral associations likely accumulate in those earthworm‐formed structures that often outlast their creators (Brown et al., 2000). In addition, earthworms are discussed to indirectly contribute to carbon stabilization during bioturbation by transferring, for example, plant generated OM or SOM into microbially easily accessible fractions (e.g., mucus; Brown et al., 2000) and, thus, increase microbial bio‐/necro‐mass on organo–mineral associations and aggregates (Angst et al., 2022). In our experiments, the fraction of CEM that is not adsorbed to mineral surfaces might contribute to this indirect stabilization mechanism as it will remain available for microbial degradation.…”

Section: Discussionmentioning

confidence: 99%

The functional role of earthworm mucus during aggregation

Guhra,

Wonneberger,

Stolze

et al. 2023

J. Plant Nutr. Soil Sci.

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BackgroundSoil organisms influence pedogenesis on a molecular level through the production of biopolymers which interact with soil minerals depending on their molecular properties. Specifically, biopolymers impact structure formation by inhibiting aggregation as a separation agent or promoting aggregation as a bridging agent. Mucus is a biopolymer excreted by earthworms that consists mainly of proteins, polysaccharides, and, to a lesser extent, lipids. However, despite earthworms’ fundamental contribution to soil quality and structuring via bioturbation, the role of mucus in aggregation still has to be unraveled.AimsOur study explores the role of cutaneous earthworm mucus (CEM) of Lumbricus terrestris L. for the formation of organo–mineral associations and aggregates, a sub‐process of pedogenesis.MethodsWe conducted batch experiments with goethite and CEM at different pH values and varying CEM concentrations to form mucus–goethite associations. Employing the newly formed mucus–goethite associations, we explored the (homo‐/hetero‐)aggregation with quartz particles as a function of the loading of surfaces with mucus‐C and CEM concentrations in solution.ResultsOur results suggest that the molecular structure of CEM constituents (especially proteins) is sensitive to pH. We found that the adsorption of CEM to goethite depends on pH and concentration. Polysaccharides of CEM adsorbed preferentially under acidic conditions (pH 3) and at low CEM concentration (6 mg mucus‐C L–1). In contrast, stronger adsorption of proteins was observed at higher CEM concentrations (30 mg mucus‐C L–1). In subsequent aggregation experiments, the hetero‐aggregation rate of organo–mineral associations and quartz decreased at low C‐loadings. Conversely, the rate increased at high loadings compared to the CEM‐free reference. Furthermore, electrostatic/steric repulsion (separation agent) inhibited the aggregation between goethite particles at high CEM concentrations in the solution (mineral/mucus ratio of 17). However, at a low CEM supply (mineral/mucus ratio of >83), CEM took the role of a bridging agent.ConclusionsThe composition, function, and (im‐)mobilization of CEM and corresponding organo–mineral associations in earthworm‐influenced soil structures are shaped by the structure/reactivity of CEM affected by environmental parameters. Formation and aggregation of mucus–mineral associations contribute to nutrient/carbon storage and are involved in the structure formation in soil.

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Earthworms as catalysts in the formation and stabilization of soil microbial necromass

Cited by 40 publications

References 112 publications

Climate-dependent plant responses to earthworms in two land-use types

Climate-dependent plant responses to earthworms in two land-use types

Climate-dependent plant responses to earthworms in two land-use types

The functional role of earthworm mucus during aggregation

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