Earthworms increase the stability of soil organic carbon
Earthworms stimulate microorganisms to produce more stabilised carbon in the soil. (Picture: A. Murray)
Earthworms burrow through the soil, mixing mineral particles, organic material and mucus, and settle microorganisms and their substrates in so-called "castings". This stimulates the growth of microorganisms whose dead remains (necromass) are then stabilised in the earthworm balls, resulting in more stabilised soil carbon. (Picture: Angst et al., 2022, Global Change Biology)
Novel concept helps managing soils as a carbon sink
Report by Dr Gerrit Angst, postdoctoral researcher of the Experimental Interaction Ecology at iDiv and Leipzig University and first author:
Leipzig/Budweis/Munich. Earthworm activity stimulates microorganisms to accelerate the production of more stabilised soil organic carbon. This is the conclusion from a synthesis of recent literature collated by a team led by researchers from the German Centre for Integrative Biodiversity Research (iDiv), Leipzig University, the Czech Academy of Sciences, and the Technical University of Munich. Based on this synthesis, the authors developed a novel concept of the role of earthworms in soil organic carbon dynamics that aids management of soils as a carbon sink. The study has recently been published in Global Change Biology.
Earthworms were recognised as a central component of ecosystems with distinct effects on their environment as early as 1881 by Charles Darwin. More recent research indicates that earthworms, as "ecosystem engineers", strongly influence the soil’s greenhouse gas balance and the soil carbon budget via burrowing and the creation of cast aggregates. Despite their widely accepted relevance to soil processes in many ecosystems, earthworms have not found their way into any recent conceptualisation of soil organic carbon dynamics. "This was very surprising to us and certainly narrows down the potential to manage soils as a carbon sink in the face of global change", says Dr Gerrit Angst, lead author of the article from iDiv and Leipzig University. The international author team, comprised of researchers from Germany, the Czech Republic, and The Netherlands thus developed a novel concept that aligns recent ideas on soil organic carbon formation with the activity of earthworms.
Recently, scientists have been recognising that the dead remains of microorganisms (or microbial necromass) represent a central component of soil organic carbon. The formation of this necromass is thought to be strongly dependent on efficient microbial growth, which is in turn related to the decomposability of the organic matter these microbes feed on. "Based on recent experimental evidence, we argue that earthworms reduce the relevance of the decomposability of pre-existing organic matter to microbial necromass formation. Earthworms achieve this by creating favourable conditions for microbial growth in their casts", explains Angst. Such casts are rich in nutrients and represent an intimate mixture of earthworm-excreted, easily decomposable mucus, organic matter, and mineral particles, such that potential nutrient and carbon limitations are alleviated and microbes and their substrates co-located. Microbial biomass is thus efficiently built up, and upon microbial death, the microbial necromass is stabilised within the cast structures by interaction with mineral particles.
Based on this concept, soils affected by earthworms can be expected to harbour higher amounts of microbial necromass resistant to external disturbances as compared to soils devoid of earthworms. This may be specifically relevant in soil areas not commonly considered hotspots of microbial carbon formation, such as areas remote from the plants’ root zone or deeper soil layers. Co-senior author of the study, Prof Nico Eisenhauer from iDiv and Leipzig University concludes: "Management strategies seeking to increase the resistance of soil organic carbon in the face of climate change may therefore want to involve measures that foster earthworm abundance."
This research was, among others, supported by the Deutsche Forschungsgemeinschaft (DFG; AN 1706/2-1)
Original publication:
(Scientists with iDiv affiliation in bold)
Angst, G., Frouz, J., Scheu, S., van Groenigen, J.W., Kögel-Knabner, I. & Eisenhauer, N. (2022): Earthworms as catalysts in the formation and stabilization of soil microbial necromass. Global Change Biology. DOI: 10.1111/GCB.16208
Contact:
Dr Gerrit Angst
Experimental Interaction Ecology
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Leipzig University
SoWa Research Infrastructure and Institute of Soil Biology, Czech Academy of Sciences
Phone: +49 341 9739179
Email: gerrit.angst@idiv.de
Web: www.idiv.de/en/profile/1575.html
Urs Moesenfechtel, M.A.(speaks English and German)
Media and Communications
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Phone: +49 341 9733106
Email: urs.moesenfechtel@idiv.de
Web: www.idiv.de/en/profile/1464.html
