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Poster De Conférence Année : 2018

Earthworms affect biogeochemical cycling through their impact on carbon and nitrogen stabilization by mineral interactions

Résumé

Stabilization of organic matter (OM) is an important process controlling the coupling and decoupling of biogeochemical cycles and their role in mitigating climate change. Soil organisms, particularly earthworms, may greatly influence these processes through their potential impact on the interaction of OM with soil minerals ; a mechanism which may protect soil organic matter (SOM) at medium (years) and long (decades, centuries) time scales. The aim of this study was to use earthworms and pure minerals in order to enhance the formation of organo mineral interactions during a 6 month decomposition experiment. Our experimental approach was based on the comparison of OM decomposition without minerals and OM decomposition with minerals (70% fresh OM & 30% Montmorillonite). These treatments were establish with and without the simultaneous presence of two epigeic earthworm species (Eisenia andrei and Eisenia foetida). We used density fractionation of the end-products to isolate several fractions : water soluble OM, free particulate OM, mineral associated OM (>1.6 g cm3 and >1.8 g cm3). The fractions were characterised by elemental analyses, electron microscopy and Rock Eval pyrolyses to investigate the effect of earthworms on the allocation of C and N compared to treatments without worms. Presence of minerals led to the formation of organo-mineral complexes in the heavy fractions, while for pure OM treatments heavy fractions were absent. Indeed, the addition of minerals during the decomposition process resulted in the transfert of 70% of carbon and nitrogen from soluble and particulate OM to heavy fractions. With worms more C and N were allocated to the >1.8 g cm3 fractions as compared to treatments without worms. Indeed, worms led to highest C contribution in the 1.6-1.8 g cm3 fraction. Moreover, earthworm presence led to the formation of black cristalline particles in the heaviest fraction. Information about the morphology and stability of organo-mineral complexes will be presented. We conclude that the presence of earthworms impact biogeochemical cycling of C and N through influencing the stabilization of OM by interaction with minerals.
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Dates et versions

hal-02734044 , version 1 (02-06-2020)

Identifiants

  • HAL Id : hal-02734044 , version 1
  • PRODINRA : 477600

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Guillaume Le Mer, Justine Barthod, Marie-France Dignac, Cornelia Rumpel. Earthworms affect biogeochemical cycling through their impact on carbon and nitrogen stabilization by mineral interactions. 1st International Earthworm Congress (IEC 1), Jun 2018, Shangai, China. , 2018. ⟨hal-02734044⟩
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