Rôle des compartiments de la drilosphère des vers de terre dans la dynamique du carbone organique des sols tropicaux
Year: 2025
Type: dissertation
Abstract: Earthworms, as ecosystem engineers, play a pivotal role in soil organic carbon (SOC) dynamics through the creation of the drilosphere—the soil domain shaped by their burrowing, feeding, and casting activities. While surface casts have been relatively well studied, other compartments such as belowground casts and burrow linings remain understudied, particularly in tropical soils where earthworm diversity is high. Moreover, the consequences of species interactions for SOC stabilization and mineralization are still poorly understood. The aim of this thesis was to disentangle the contribution of tropical earthworm species and their interactions to SOC storage and CO₂ emissions across drilosphere compartments. Mesocosm and incubation experiments were conducted with Vietnamese soils and earthworms, combining physical fractionation (POM vs. MAOM), isotopic tracing, CO₂ flux measurements using a Micro Gas Chromatograph, and X-ray computed tomography to characterize the mass, composition, and stability of carbon in drilosphere structures. The results provide four major insights. First, drilosphere compartments differ strongly in their capacity to stabilize or release carbon: subsurface structures such as burrow walls promoted carbon persistence, while surface casts acted as transient hotspots of microbial activity and carbon loss. Second, species identity was decisive, as contrasting tropical earthworm species generated distinct balances between SOC stabilization and mineralization through the properties of the compartments they formed. Third, interspecific interactions enhanced SOC storage: mixed-species assemblages produced synergistic, non-additive effects on carbon accrual. Finally, the so-called earthworm dilemma - whether earthworms act as net carbon sources or sinks - proved to be context-dependent, shaped by compartment type, environmental conditions, and community composition. This thesis advances our mechanistic understanding of SOC persistence by showing that carbon stability is not an intrinsic property of organic matter but emerges from interactions among biological activity, spatial localization within the soil matrix, and species diversity. The findings highlight the drilosphere as a critical regulator of carbon cycling in tropical soils and demonstrate that biodiversity must be integrated into soil carbon models. From this perspective, management practices that conserve or promote earthworm diversity in agroecosystems could enhance soil fertility and contribute to carbon sequestration under global change.
Source: theses.fr (ABES)
Author: Dang, Xuan Hoang
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDGs: Life on land, Climate action
Open Access status: green
OpenAlex ID: W7128936171
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