Presence Of Earthworms Research Articles

The effects of roots and earthworms on aggregate size distribution and their associated carbon under contrasting soil types and soil moisture conditions

Soil’s potential as a carbon sink is uncertain due to biotic and abiotic interactions. Soil aggregates are important carriers of organic carbon (OC), and clarifying the response of aggregates and their associated OC to plant roots and earthworms can better understand the carbon cycle in terrestrial ecosystems. Herein, we determined the regulatory role of plant roots (Lolium perenne) and earthworms (Metaphire tschiliensis) in isolation and in combination on aggregate size distribution and their associated OC and readily oxidizable OC (ROOC) under contrasting soil types (Phaeozems and Anthrosols) and soil moisture conditions (constant wetting, CW; wetting–drying cycle repeated four times, 4WD) by a laboratory microcosm experiment. Results showed that earthworm presence significantly increased plant biomass by 30 % and 221 % in Phaeozems and Anthrosols, respectively (p < 0.05). For Phaeozems, plant alone (P) and plant and earthworm in combination (PE) had lower proportion of large aggregate (5–8 and 2–5 mm) than bare soil (CK) under 4WD condition (p < 0.05). For Anthrosols, the PE treatment decreased the proportion of 5–8 and 2–5 mm aggregate by 45 % and 25 %, respectively, under CW condition, and decreased the proportion of 5–8 mm aggregate by 37 % under 4WD condition (p < 0.05). Moreover, the proportion of 5–8 and 2–5 mm aggregate in P treatment was lower under CW condition (6.92 % and 22.13 %) but was higher under 4WD condition (11.49 % and 32.55 %) than those in CK (14.69 % and 29.91 %; 8.85 % and 20.56 %) (p < 0.05). Our results further indicated that the PE treatment had relatively higher OC and ROOC contents, especially for small aggregates in Anthrosols. The study indicates that plant roots and earthworms significantly influence aggregate turnover and the carbon cycle, with soil type and moisture playing a crucial role.

Influence of earthworms on the mobility and bioavailability of metals, metalloids and radionuclides in historically contaminated soil

While soil characteristics such as pH, cation exchange capacity and organic matter are known to influence the mobility of pollutants in soil and the transfer to vegetation, far less attention has been paid to the possible non-trophic influence of organisms on pollutant transfer to other species. When pollutants are present in a bound unavailable form in the mineral or organic fraction, they can be made available through bio-weathering and decomposition of organic material. Within this study, the impact of earthworms on the mobility of metal(loid)s and radionuclides in soil and their transfer to vegetation was evaluated and the pathways through which earthworms work were studied. Soil from a Belgian field, historically contaminated with metal(loid)s and radionuclides, was used and microcosm systems were applied to mimic the natural interactions between soil, earthworms (Lumbricus terrestris) and vegetation (Lolium perenne). Metal and radionuclide concentrations were determined in soil, pore water and grass. In addition, soil pH, (chromophoric) dissolved organic matter, the ionic composition of pore water and the soil microbial activity were analysed. In general, earthworm presence significantly increased the concentration of most pollutants in soil pore water. This could be a direct consequence of decreased soil pH and increased humification. The latter also lead to higher nutrient concentrations in pore water that were depleted in the root zone due to high accumulation by plants. Indications were found for earthworm-induced effects on the soil microbial activity. The results show that earthworm activity can increase leaching of metal(loid)s and radionuclides and enhance dispersion into the environment and transfer to other biota and the food chain. Biologically induced release or remobilization of pollutants in the soil should therefore be considered in the context of risk assessment and site management strategies.

Effects of biodegradable microplastics coexistence with biochars produced at low and high temperatures on bacterial community structure and phenanthrene degradation in soil

The increasing use of biodegradable plastics may result in more serious pollution of microplastics which often coexist with biochar in soil, this will affect how organic pollutants move and transform in the soil. This work investigated the effect of biodegradable polybutylene adipate-co-terephthalate (PBAT) coexistence with biochars produced at temperatures of 400 and 700 °C (W4 and W7) on soil bacterial communities and phenanthrene degradation. The results showed that coexistence of PBAT and biochar paticles greatly boosted the relative abundance of Nocardioides while decreased the relative abundance of Sphingomonas as compared to soils with a single addition of PBAT or biochar. Changes in soil Eh values were the most influential factor in bacterial communities (more than 40% contribution). The degradation ratio of phenanthrene when PBAT coexisted with W7 (39.6 ± 3.6%) was not significantly different from the treatment with a single W7 addition (35.0 ± 2.3%, P＞0.05), and was related to phenanthrene degradation in the adsorbed state of W7 in soil. In contrast, the degradation ratio of phenanthrene in PBAT coexisting with W4 (35.1 ± 3.5%) was intermediate between that of single PBAT (49.8 ± 0.9%) and W4 (13.7 ± 5.8%) treatments. This was primarily due to changes in the experiment's initial bioavailable phenanthrene content. Furthermore, after the introduction of earthworms, phenanthrene degradation ratio in coexistence treatments were very similar to that described above in the absence of earthworms. Except for two treatments that contain W7, phenanthrene degradation ratio in the other treatments was increased by the presence of earthworms (up to 23%), which is related to the enhanced relative abundance of polycyclic aromatic hydrocarbon-degraders. Our findings indicated that PBAT coexistence with high-temperature or low-temperature biochar had a completely different impact on bacterial communities and phenanthrene degradation in soil.

Forecasting Oligochaeta Abundance using the Apparent Electrical Conductivity of Irrigated Soils with Reclaimed Wastewater: Evidence from Corso, Algeria

Background: The main objective of this paper is to study the possibility of using the measurement of apparent electrical conductivity (ECa) to estimate Oligochaeta (earthworm) density in irrigated soils treated with reclaimed wastewater. Additionally, the study sought to analyze the impact of using reclaimed wastewater for irrigation on earthworm density in the study area. Methods: Earthworm sampling was carried out at thirty emplacements within the study area during two measurement campaigns. Soil ECa was measured by (EM38). Result: The results showed that irrigation with reclaimed wastewater promotes the abundance of earthworms (earthworm density). Indeed, sites irrigated with reclaimed wastewater have higher earthworm densities compared to sites irrigated with conventional water. The results also show a strong correlation between ECa and earthworm density (R2 greater than 0.7). The Wilcoxon test indicates a non-significant difference between measured earthworm densities and those predicted by ECa (p greater than 0.5). This result confirms the effectiveness of the EMI technique as a tool to evaluate the spatial variability of soil biological parameters. These results collectively suggest that ECa represents a real possibility of reducing the number of earthworm samplings, whil ensuring the reliability of the estimates of real values of earthworm density and their surface spatial distribution. ECa could therefore be a useful tool to spatialize and predict the presence of earthworms in soil irrigated by reclaimed wastewater.

Earthworms alleviate microplastics stress on soil microbial and protist communities

Microplastic (MP) pollution can exert significant pressure on soil ecosystems, however, the interactive effects of MPs on soil bacterial, fungal and protist communities remains poorly understood. Soil macrofauna, such as earthworms, can be directly affected by MPs, potentially leading to a range of feedbacks on the soil microbial community. To address this, we conducted a microcosm experiment to examine the effects of conventional (i.e., polyethylene, polystyrene) and biodegradable MPs (i.e. PBAT, polylactic acid) on the structure of the soil bacterial, fungal, and protist communities in the presence or absence of earthworms. We found that MP contamination negatively affected the diversity and composition of soil microbial and protist communities, with smaller-sized conventional MPs having the most pronounced effects. For example, compared with the unamended control, small-sized polyethylene MPs both significantly reduced the Shannon diversity of soil bacteria, fungi, and protist by 4.3 %, 37.0 %, and 9.1 %, respectively. Biodegradable MPs increased negative correlations among bacteria, fungi, and protists. However, earthworms mitigated these effects, enhancing the diversity and altering the composition of these communities. They also increased the niche width and stability of the soil microbial food web network. Our study indicated that earthworms help attenuate the response of soil microorganisms to MPs stress by influencing the diversity and composition of soil microorganisms and soil physicochemical properties and underscores the importance of considering macrofauna in MPs research.

Enhancing zinc biofortification and mitigating cadmium toxicity in soil–earthworm–spinach systems using different zinc sources

Cadmium (Cd) pollution poses significant threats to soil organisms and human health by contaminating the food chain. This study aimed to assess the impact of various concentrations (50, 250, and 500 mg·kg–1) of zinc oxide nanoparticles (ZnO NPs), bulk ZnO, and ZnSO4 on morphological changes and toxic effects of Cd in the presence of earthworms and spinach. The results showed that Zn application markedly improved spinach growth parameters (such as fresh weight, plant height, root length, and root-specific surface area) and root morphology while significantly reducing Cd concentration and Cd bioconcentration factors (BCF-Cd) in spinach and earthworms, with ZnO NPs exhibiting the most pronounced effects. Earthworm, spinach root, and shoot Cd concentration decreased by 82.3 %, 77.0 %, and 75.6 %, respectively, compared to CK. Sequential-step extraction (BCR) analysis revealed a shift in soil Cd from stable to available forms, consistent with the available Cd (DTPA-Cd) results. All Zn treatments significantly reduced Cd accumulation, alleviated Cd-induced stress, and promoted spinach growth, with ZnO NPs demonstrating the highest Cd reduction and Zn bioaugmentation efficiencies compared to bulk ZnO and ZnSO4 at equivalent concentrations. Therefore, ZnO NPs offer a safer and more effective option for agricultural production and soil heavy metal pollution management than other Zn fertilizers.

Earthworm influence on soil aggregate distribution and protected carbon at managed forest sites in Vermont, USA

The long-term effect of non-native earthworm species on forest soil carbon storage is not clear. While initial invasion into earthworm-free soils stimulates carbon losses, there is evidence that carbon stabilization in soil aggregates is enhanced. Fourteen managed forest sites throughout Vermont were sampled to identify and enumerate earthworms, and determine soil aggregate distribution and physically protected carbon. Most of these sites were northern hardwoods reforested in the mid-20th century after agricultural land use. Soil at six 50 × 50 cm subplots at each site was sampled to a depth of 20 cm below the Oe horizon and the mineral soil fractionated into free microaggregates (<250 μm), small macroaggregates (250–2000 μm), and large macroaggregates (>2000 μm). Microaggregates were then isolated from the macroaggregates and organic carbon determined. Mean earthworm numbers below the Oe horizon at each site ranged from 0 to 313 individuals m−2 and ten different species were identified, representing all earthworm ecotypes. Four sites had no earthworms in the soil layer sampled, three sites had earthworms in every subplot with up to six different species, and seven sites had subplots both with and without earthworms. When subplots were grouped by number of species present, there was a trend towards a greater fraction of the mineral soil in macroaggregates containing greater protected carbon, and a lower fraction of free microaggregates. A paired t-test of subplots from the seven sites with variable earthworm presence showed significant differences in the same trends and there was significantly greater mineral soil total carbon and protected carbon in the subplots with earthworms. These results are consistent with recent research into earthworm effects on soil carbon stabilization. While initial invasion likely resulted in a negative carbon balance, our findings suggest that earthworms can enhance transfer of carbon into physically protected pools in these forest soils.

Indirect effect of earthworms on wheat-aphid interactions

Studies on interactions between plants and belowground organisms, or between plants and aboveground organisms, are numerous and highlight their importance in understanding ecosystem functioning. However, these two compartments are rarely studied together, despite the direct link formed by the plant itself. Soil organisms can influence interactions between plants and herbivores by changes in plant growth and chemistry. Under controlled conditions the influence of earthworms and aphids on wheat was investigated. The effect of earthworms on aphid reproduction was also investigated, to demonstrate the indirect plant-trait-mediated effects. We showed a significant effect of both above and belowground organisms on wheat. Interestingly, nitrogen content was higher in the presence of aphids (1.63 ± 0.07 %,) or earthworms alone (1.58 ± 0.04 %) and even higher in presence of both (2.07 ± 0.07 %). Moreover, we showed a strong effect of earthworms on aphid reproduction rates which are almost twice as high as in the absence of earthworms where we observed a reproduction rate of 32 individuals per day compared with 57 in the presence of earthworms. The presence of aphids led to a 16 % reduction in above-ground biomass compared with the control (1.83 ± 0.08 g vs 2.19 ± 0.09 g for the control), while the presence of earthworms led to an 46 % increase (3.20 ± 0.12 g vs 2.19 ± 0.09 g), and the presence of both organisms had no significant effect on the above-ground biomass of wheat compared with the control (2.39 ± 0.08 g vs 2.19 ± 0.09 g). These results could have implications for pest management, as they indicate that the presence of earthworms compensate the negative effect of aphids on plant biomass, probably by acting on nutrient uptake and plant defensive traits. By addressing the effects of earthworms on both the pest performances and plant traits, we highlight the need for further research on the indirect effects of below-ground compartments on pest performance. This study builds towards a better understanding of the interaction between soil, plant and pests and highlights the importance to study the pest management with a holistic view of agroecosystems.

Earthworms promote crop growth by enhancing the connections among soil microbial communities

Abstract Earthworms benefit plant growth and play a vital role in shaping soil microbial communities. However, how earthworms modify the soil microorganisms and thus affect plant growth is still unclear. Although fertilizers alter the assembly of microbial communities, further investigations are required to test the effect of fertilizer type on the relationship between earthworms, soil microbial communities and plants. We evaluated the role of earthworms in soil microorganisms and maize plant growth characteristics under organic or chemical fertilizers in field and greenhouse experiments. We explored the relationships between earthworms, soil microbial community and plant growth under different fertilizer types. We found that the presence of earthworms promoted plant growth, increased the amount of plant root exudates, and enhanced the connections between rhizosphere bacterial, fungal and protist communities. Both earthworms and fertilizer application significantly changed the structure of soil bacterial, fungal and protist communities. The complexity of the soil microbial community network increased under organic, compared to chemical fertilizer application. The greenhouse experiment showed that the effect of earthworms on plant growth was weakened when maize plants were grown in sterilized soil under organic or chemical fertilizers. Synthesis and applications: Our study provides solid evidence that earthworms largely depend on soil microorganisms for their effects on plants under the application of different fertilizer conditions. This may provide new insights into reducing the amounts of fertilizer used by enhancing the role of earthworms and soil microorganisms.

Biological Indicators of Resilience in Mixed and Monoculture Musaceae Production Systems

Objective: To examine the impact of intraspecific diversity on the biological resilience and biodiversity of Musaceae production systems against pests and diseases in the Ecuadorian tropics, thereby improving the environmental sustainability of these agricultural systems. Theoretical Framework: Key concepts such as biological resilience, intraspecific diversity of Musaceae, and their relationship with soil health and pest and disease control were explored. The importance of mixed production systems versus monocultures in Musaceae agriculture was discussed. Method: An experimental design with completely randomized blocks was adopted in two locations (El Carmen and La Maná), comparing mixed and monoculture production systems. Three repetitions were used to collect data on the presence of arthropods, earthworms, and soil microorganisms, evaluating their diversity and quantity as indicators of biological resilience and environmental quality. Results and Conclusions: Mixed systems demonstrated greater biodiversity, particularly in the presence of Collembola, earthworms, and various beneficial microorganisms, indicating higher resilience and soil health compared to monocultures. Intraspecific diversity in mixed systems significantly contributes to the sustainability and resilience of Musaceae agroecosystems, suggesting a more resilient and ecologically sustainable production model for tropical agriculture. Originality/Value: This study provides empirical evidence on how intraspecific diversity and mixed production systems can enhance resilience and biodiversity in Musaceae crops, offering sustainable alternatives to face contemporary agricultural challenges in the Ecuadorian tropics.

Optimizing Vermicomposting Methods Involves Improving Efficiency, Maximizing Nutrient Retention and Minimizing Environmental Impacts: A Review

Vermicomposting is a sustainable and eco-friendly approach to organic waste management and fertilizer production. Earthworms are fundamental to the delivery of a range of soil ecosystem services such as nutrient cycling and water management, which in turn affects crop development and yield.In fact, one study states the presence of earthworms in soils can increase crop yields by an average of 25% and total crop biomass by 21%. Comparing the production efficiency between the upper pit and windrow method for vermicomposting involves considering several factors including processing capacity, labor requirements, processing time, and resource utilization.

Evaluating drained water quality in a pilot worm-sludge treatment reed bed planted with Arundo donnas in the Mediterranean climate

This study evaluated the impact of incorporating earthworms (Eisenia fetida) on the drained water quality from a sludge treatment reed bed. The experiment encompassed four setups of treatment beds in two replicates: planted with Arundo donax and addition of earthworms, planted without earthworms, unplanted with earthworms, and treatment bed without plants nor earthworms as control. The units were fed every two weeks with mixed sewage sludge, a blend of primary and secondary sludge over 24 cycles. The mixed sewage sludge had mean dry and volatile solid contents of 24.71 g.DS.L−1 (± 13.67) and 19.14 g.VS.L−1 (± 10.29) resulting a sludge loading rate of 43.59 kg.DS.m−2.year−1 (± 14.49). The inclusion of earthworms in the planted unit reduced release masses of total suspended solids, chemical oxygen demand, nitrate and phosphorous by 43, 45, 75 and 45 % compared to the planted unit. Plant biomass production increased by 43 % with the earthworm presence. The removal efficiency of the units improved after a ramp-up phase (after six months feeding) of which the concentration of TSS, COD and Escherichia coli met limits for water reuse while nitrogen components and phosphorous surpassed the limits. The planted unit with earthworms removed 99 and 99 % of TSS and COD, respectively. Overall, water loss namely through evapotranspiration and earthworm hydration need, positively correlated with pollutant concentration, and earthworm-planted unit had 46 % higher water loss compared to control unit.

Agroforestry Systems of Cocoa (Theobroma cacao L.) in the Ecuadorian Amazon

Agroforestry systems in the Ecuadorian Amazon play a vital role in environmental conservation and the promotion of sustainable agriculture. Therefore, it is crucial to demonstrate the benefits of the associated species within these production systems. This study aimed to assess the impact of agroforestry systems on cocoa yield, carbon sequestration, earthworm presence, and the nutritional contribution of companion species linked to cocoa (Theobroma cacao L.) cultivation under agroforestry systems. The research was conducted at INIAP’s Central Experimental Station of the Amazon using a randomized complete block design with three replications. The agroforestry arrangements were: (1) monoculture; (2) forest (Cedrelinga cateniformis Ducke); (3) fruit forest (Bactris gasipaes Kunth); (4) service (Erythrina poeppigiana (Walp.) O.F.Cook); and (5) forest + service (E. poeppigiana + C. cateniformis). The results indicated that agroforestry systems showed better results than the monoculture in terms of yield (532.0 kg ha−1 compared to 435.4 kg ha−1) and total stored carbon (33.0–42.0 t ha−1 compared to 39.6 t ha−1). Additionally, agroforestry systems provided higher levels of Mg, B, and Ca, contributing to both crop yield and the presence of earthworms. These findings suggest a positive influence of companion species, improving soil nutrition through biomass incorporation and promoting environmental benefits (carbon sequestration). Therefore, agroforestry systems will support sustainable cocoa production in the Ecuadorian Amazon.

Application of Arabidopsis thaliana in the Remediation of Soil Pollution : Evidence from the Earthworm-Microbe-Arabidopsis System

ABSTRACT Presence of cadmium in soil affects the growth status of plants; research on the underlying mechanism has focused on its lethal and sublethal consequences in plants, ignoring the impacts of soil organisms. Therefore, this study designed a microorganism – earthworm – plant ecosystem, investigated the influence of Cd (0, 0.3, 1.0, and 3.0 mg kg−1) on the growth of Arabidopsis thaliana in the presence of earthworms (Eisenia fetida), and revealed the mechanisms from the perspective of altered relationships among different soil organisms. In this study, there was no significant difference in the death rate of earthworms with low Cd addition concentration, but the microorganisms in earthworms and soil microorganisms changed, abundance of Actinomycetes in soil increased, while Planctomycetes decreased, Mycobacterium in the gut of Eisenia fetida decreased under Cd stress. Microorganisms affect soil pH, which in turn affects soil physicochemical properties and the form of cadmium in soil. Compared with the control, soil pH significantly decreases under cadmium stress, Under 0.3 mg kg−1 treatment, soil total nitrogen, available phosphorus and total potassium are 181.11, 5.09, 51.90, and 7.55 mg kg−1, respectively, They were significantly higher than control group. Improved the growth environment of Arabidopsis thaliana and promoted the absorption of Cd in soil which affected the proportion of available Cd in the soil (when Cd was added at 1.0 mg kg−1, the proportion of available Cd in the soil decreased significantly from 95.05% to 49.40%). A. thaliana also absorbed more Cd, which increased Cd toxicity, and the reproductive growth of A. thaliana was enhanced, while vegetative growth was weakened.Compared with the control group (278.11 mg), the biomass of A. thaliana decreased significantly to 189.83 mg when Cd was supplemented at 0.3 mg kg−1. Therefore, the activities of and interactions among earthworms, plants, and microorganisms play important roles in reducing soil heavy metals and improving soil properties.

Effects of Nano-zero-valent Iron and Earthworms on Soil Physicochemical Properties and Microecology in Cadmium-Contaminated Soils

The capacity of nano-zero-valent iron (nZVI) and soil animals to remediate heavy metal–contaminated soil has been widely studied. However, the synergistic effect of soil animals and nZVI has not been thoroughly investigated. Here, we studied the combined effect of earthworms and nZVI on soil physicochemical properties and microecology during remediation of cadmium (Cd)–contaminated soil. The results showed that although amendment with nZVI reduced earthworm survival and biomass, the combination of nZVI and earthworms was effective at reducing the available Cd (ACd) content of soil and improving its quality. ACd most effectively reduced by 75.3% in the presence of earthworms under the 0.25% nZVI combination. Meanwhile, the combined action of earthworms and nZVI significantly improved soil properties and increased the diversity of soil microorganisms. In the earthworm-free system, nZVI reduced ACd by increasing soil pH and the abundance of Stenotrophobacter in Cd-contaminated soil, in addition to the co-precipitation and adsorption reported in previous studies. Correlation analysis revealed that the combination of nZVI and earthworms synergistically decreased ACd by decreasing soil OM and increasing the relative abundance of Opitutus and Gemmatta. Overall, our study indicates that the combination of nano-zero-valent iron and earthworms is a potential system for in situ remediation of Cd-contaminated soils and provides a deep understanding of the mechanisms involved in remediation.

Perbandingan Struktur Komunitas Cacing Tanah Megadrilli pada Ekosistem Alami dan Ekosistem Buatan

Earthworms are an important component of soil ecosystems. The presence of earthworms in a habitat can enhance the quality of the soil, both in its physical, chemical, and biological properties. This research has the purpose to analyze the comparison of earthworm density found in natural ecosystems and artificial ecosystems. The determination of location points is done using the Cluster Sampling method, which includes both natural and artificial ecosystems. Sampling is conducted using the line transect method along a 100-meter length in 20 plots. The earthworm collection method involves the use of square and hand sorting methods. Data analysis includes density values, frequency, diversity index, and the Morisita index, as well as statistical analysis using an independent sample T-Test to determine the significance of the difference in earthworm abundance between the two locations. Five species of megadrillic earthworms were identified, classified into two ecological categories: epigeic and endogeic. In the natural ecosystem, there were five species, namely Pheretima capensis (epigeic), P. corethururus (endogeic), Pheretima sp.1 (epigeic), Megascolex sp. (endogeic), and Pheretima sp.2 (epigeic). Meanwhile, in the artificial ecosystem, three species were found, which are P. capensis (epigeic), P. corethururus (endogeic), and Pheretima sp.2 (epigeic). The density of megadrillic earthworms in the natural ecosystem (567.8 individuals/m2) is significantly higher compared to the artificial ecosystem (242.5 individuals/m2). The relative frequency of earthworms in the natural ecosystem is divided into 3 categories: Rare (Assesory), Common (Constant), and Very Common (Absolute), whereas in the artificial ecosystem, there are 2 categories: Common (Constant) and Very Common (Absolute). The diversity index of earthworms in the natural ecosystem tends to be higher (H' = 1.236) than in the artificial ecosystem (H' = 0.885). The distribution pattern of megadrillic earthworms in the natural ecosystem is clustered, while in the artificial ecosystem, it is random.

Effect of an organophosphorus insecticide, soil texture and earthworm species on the turnover of soil, gut and cast microbiota during the earthworm's gut transit

The growing usage of plant protection products in agroecosystems questions their unintentional deleterious effects on non-target organisms such as earthworms and their related ecological function. The aim of this study was to investigate the turnover of soil microbiota during the gut transit of two endogeic earthworms (Aporrectodea caliginosa and Allolobophora chlorotica) and how it is possibly affected by the organophosphorus insecticide ethyl-parathion (Pt). We measured prokaryotic and micro-eukaryotic community composition and abundances using two different soil types in the continuum of bulk soil, gut and casts samples collected during and after one week exposure to Pt. The presence of earthworm and Pt had limited effects on the soil microbiota, although Pt altered temporarily soil microbial abundances in the presence of earthworms, not in their absence. The earthworms’ gut harbored a remarkably low prokaryotic diversity, dominated by two molecular Operational Taxonomic Units (mOTUs) affiliated to Rhodococcus and Pseudarthrobacter. Contrastingly, gut micro-eukaryotic communities were maintained at diversity levels similar to that of the soil, yet Pt augmented their diversity and changed their composition. Fresh casts collected out of the soil revealed evident variation of abundance, diversity and community composition according to the soil origin and the earthworm species. In particular, following gut transit casts were enriched with Bacteroidia and γ-Proteobacteria while depleted of Acidobacteria. Exposure to Pt increased the diversity and relative abundance of depleted mOTUs, which paves the way for future investigations on the role of Pt in rising microbial consumption due to an over-excitation of gastrointestinal motility.

Cascading effects of earthworm invasion increase graminoid density and rodent grazing intensities.

Human-mediated dispersal of non-native earthworms can cause substantial changes to the functioning and composition of ecosystems previously earthworm-free. Some of these earthworm species have the potential to "geoengineer" soils and increase plant nitrogen (N) uptake. Yet the possible consequences of increased plant N concentrations on rodent grazing remains poorly understood. In this study, we present findings from a common garden experiment with two tundra communities, meadow (forb dominated) and heath (shrub dominated), half of them subjected to 4 years of earthworm presence (Lumbricus spp. and Aporrectodea spp.). Within four summers, our earthworm treatment changed plant community composition by increasing graminoid density by, on average, 94% in the heath vegetation and by 49% in the meadow. Rodent winter grazing was more intense on plants growing in soils with earthworms, an effect that coincided with higher N concentrations in plants, indicating a higher palatability. Even though earthworms reduced soil moisture, plant community productivity, as indicated by vegetation greenness (normalized difference vegetation index), was not negatively impacted. We conclude that earthworm-induced changes in plant composition and trophic interactions may fundamentally alter the functioning of tundra ecosystems.

Earthworms do not increase greenhouse gas emissions (CO2 and N2O) in an ecotron experiment simulating a three-crop rotation system

Earthworms are known to stimulate soil greenhouse gas (GHG) emissions, but the majority of previous studies have used simplified model systems or lacked continuous high-frequency measurements. To address this, we conducted a 2-year study using large lysimeters (5 m2 area and 1.5 m soil depth) in an ecotron facility, continuously measuring ecosystem-level CO2, N2O, and H2O fluxes. We investigated the impact of endogeic and anecic earthworms on GHG emissions and ecosystem water use efficiency (WUE) in a simulated agricultural setting. Although we observed transient stimulations of carbon fluxes in the presence of earthworms, cumulative fluxes over the study indicated no significant increase in CO2 emissions. Endogeic earthworms reduced N2O emissions during the wheat culture (− 44.6%), but this effect was not sustained throughout the experiment. No consistent effects on ecosystem evapotranspiration or WUE were found. Our study suggests that earthworms do not significantly contribute to GHG emissions over a two-year period in experimental conditions that mimic an agricultural setting. These findings highlight the need for realistic experiments and continuous GHG measurements.

Earthworms facilitate stabilization of both more-available maize biomass and more-recalcitrant maize biochar on mineral particles in an agricultural soil

Agricultural soils have lost enormous amounts of soil organic matter (SOM) as the result of conventional agriculture. Nowadays, returning plant biomass in the form of crop residues is used as an efficient strategy to increase the amount of SOM. In addition, earthworms help increase the SOM content by transforming OM into stable forms. There is, however, limited information on how earthworms transform and stabilize various forms of crop residues and what the potential feedbacks on soil quality are. In a five-month laboratory manipulation experiment, we added maize biomass and/or biochar to a temperate agricultural soil both in the presence and absence of earthworms and carried out physical fractionation to analyse the stabilization of OM either as aggregate-occluded particulate OM (oPOM) or mineral-associated OM (MAOM).We show that the combination of maize biomass, maize biochar and earthworms proved to be highly efficient in increasing the OM content in agricultural soils and that earthworms can simultaneously enhance both OM decomposition and stabilization. In the absence of earthworms, the OM was stabilized more in the oPOM fraction, suggesting that both maize substrates acted as aggregation agents. In the presence of earthworms, however, maize substrates were stabilized more in the MAOM fraction, either through direct sorption as plant-derived substrates or as microbial necromass, suggesting that earthworms facilitate stabilization of both more-available maize biomass and more-recalcitrant maize biochar on mineral particles. We provide evidence that plant-derived rather than microbial-derived MAOM is present in the earthworm-affected agricultural soil and is thus important in increasing the SOM content and stability.