Response of microbial enzymatic activity to earthworm species on soil (epi-anecic vs strict-anecic)

Abstract : As detritus feeders, earthworms are qualified as soil engineers and play a key role in the degradation of soil organic matter (SOM). Their contribution to this function is either direct by consuming dead organic matter or indirect by stimulating microbial communities in the soil (Brown, 1995). Most of the studies evaluating their contribution to this function were conducted at the level of three ecological categories (epigeic, anecic and endogeic). Each ecological category described in these studies is often represented by a single model species. However, the anatomical and physiological features of earthworms belonging to the same ecological category are different, which could modify their involvement in the degradation process of soil organic matter. Within the anecic earthworms, Jégou et al., (1998, 2000), based on studies from Bouché (1972, 1977), distinguished the strict anecic from the epi-anecic : strict anecic construct high density of non-permanent burrows and have low surface litter incorporation rates whereas the epi-anecic build permanent burrows into which they incorporate high quantities of fresh litter from the soil surface. These different behaviours could impact directly soil microbial activity by inducing changes in their habitat and impacting their production of extracellular enzymes contributing to different biogeochemical cycles (C, N, P) and thus to SOM decomposition. The objectives of this study were to determine and compare the contribution of different earthworm species within epi-anecic and strict anecic to the degradation of SOM through the analysis of soil enzymatic activity in their middens and burrows. To do this, an experiment using soil microcosms was conducted in 5 replicates to compare the impact of (1) three separate epi-anecic species (Lumbricus rubellus, L. centralis and L. terrestris), (2) three separate strict anecic species (Aporrectodea caliginosa meridionalis, A. nocturna and A. giardi) and (3) the mixing effects between these different species (by pairs of two species) on five enzymatic soil activities. Enzyme activities measured were (i) FDA (global soil activity), (ii) Beta-Glucosidase (carbon cycle), (iii) Cellulase (carbon cycle), (iv) Leucine Amino Peptidase (nitrogen cycle) and (v) Phosphatase (phosphorus cycle). Earthworms were fed with Lolium perenne during 30 days. Enzymatic activities were analysed at the end of the experiment (30 days) in middens and in the earthworm burrows and compared to those measured in microcosms of soil without earthworms (control). In monoculture and compared to the bulk soil (without earthworms), we observed that enzymatic activities were significantly stimulated in the presence of epi-anecic compared to strict-anecic species independently of the two micro-sites sampled (middens and earthworm burrows). These differences are more pronounced with FDA, Leucine Amino Peptidase and Beta-Glucosidase enzyme activities than with Cellulase and Phosphatase (respectively, +34, +57, +78 and +14, +8 %). Still in monoculture, no difference was found between species of the same ecological category. Interactions between earthworm species (intra- or inter-ecological category) on enzyme activity were mainly additive (functional redundancy). These initial results are in accordance with the grouping of the earthworms into functional groups initially based on morphological, physiological and ecological criteria that is thus consistent with the measurements of microbial activities carried out.
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Submitted on : Friday, August 2, 2019 - 5:20:01 PM
Last modification on : Sunday, August 4, 2019 - 1:19:06 AM

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  • HAL Id : hal-02262572, version 1

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Kevin Hoeffner, Mathieu Santonja, Daniel Cluzeau, Cécile Monard. Response of microbial enzymatic activity to earthworm species on soil (epi-anecic vs strict-anecic). 1st International Earthworm Congress, Jun 2018, Shanghaï, China. ⟨hal-02262572⟩

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