Earthworm Density Research Articles

Does earthworm density change the quality of degraded volcanic soil?

Earthworms, as ecosystem engineers, are known to inoculate organic residues with microorganisms, consuming and processing mineral soil and its organic matter, which may lead to changes in soil quality. We conducted a field experiment, in randomized complete blocks, using soil mesocosms incubated with 4 different densities of earthworms: L1 = 100 earthworms m−2, L2 = 500 earthworms m−2, L3 = 1000 earthworms m−2, and C0 = control without earthworms. All earthworm populations consisted of epigeic, endogeic and anecic earthworms in a ratio of 2:3:3, respectively. The earthworms used were Lumbricus rubellus, Octolasium cyaneum, Aporrectodea calliginosa, and Lumbricus friendi. Physical (aggregate stability and structure heterogeneity), chemical (pH CaCl2, Mineral-N, Olsen-P, exchangeable K+, Ca+2, Mg+2, Na+ and Al) and biological indicators (microbial biomass) were assessed to evaluate the changes in soil quality. After applying an equivalent of 18 tons ha−1 of aged horse manure to each mesocosm, soils were sampled at two depths: 0–25 cm and 25–50 cm and on two occasions: prior to inoculating the soil with earthworms, T0, and 96 days after the soil was inoculated with earthworms, T1. Earthworms were found to increase soil mineral nitrogen (NO3 + NH4) and exchangeable calcium (Ca+2) and decrease exchangeable aluminum (Al+3) and soil microbial biomass (g C g−1). These results could imply that earthworms promote the mineralization of organic nitrogen, increase the cation content, and decrease the solubility of the principal toxic elements in soil (Al+3). Finally, the incorporation of earthworms at the 0–25 cm depth proved to increase the quality of the degraded soil, which was reflected in the chemical quality parameters.

Effects of the tropical endogeic earthworm Pontoscolex corethrurus on the horizontal dispersal of soil nematodes

Free-living nematodes are key organisms that greatly enhance plant growth and nutrient uptake. In contrast, plant-parasitic nematodes are considered a major pest group in agriculture. The effect of nematodes, either positive or negative, on plant productivity depends on their ability to disperse in soils. Understanding the dispersal process of nematodes is therefore crucial but is still poorly documented. The aim of this study was to examine the effects of the endogeic tropical earthworm Pontoscolex corethrurus on the horizontal dispersal of nematodes in Ferralsols in Madagascar. A microcosm experiment was conducted under controlled laboratory conditions. Two factors modulating dispersion were studied: (i) the earthworm density with three modalities (without, five or ten individuals) and (ii) the duration of the experiment with two modalities (four and eight weeks). The results showed that P. corethrurus favored the horizontal dispersal of nematodes. This is mainly a dispersal mechanism through the earthworm casts that they deposit in the soil or on the soil surface during their movements. The total abundance of dispersed nematodes increased with the earthworm density and the duration of the experiment. Cephalobidae dominated the trophic structure of the dispersed nematodes, similar to the original populations. However, the original populations had a higher taxonomic diversity than the dispersed nematode communities. These results indicate that P. corethrurus, through dispersion, influences the spatial and temporal distribution, abundance and structure of nematode communities in the soil.

Earthworm activity effectively mitigated the negative impact of microplastics on maize growth

Microplastic pollution can have detrimental effects on soil environments and inhibit crop growth. Earthworms, known as soil engineers, promote crop growth, but their role and impact on the amelioration of microplastic-polluted soil is not yet clear. In this study, we investigated the impact and pathways of earthworm activity on microplastic-contaminated soil by introducing varying densities (without earthworm:0, low-density: 1, medium-density: 2, high-density: 5 ind column−1) of earthworms (epi-endogeic) into soil contaminated with two types of microplastics: polyethylene and polyvinyl chloride. Our results showed that earthworms all survived in soil polluted with two types of microplastics. Meanwhile, earthworm activity increased nutrient content and enzyme activity by 0.2–36.1% and 2.9–34.3%, respectively, and significantly increased soil microbial biomass and community diversity index. Earthworm activity also decreased antioxidant enzyme activity and promoted maize plant growth, including agronomic traits such as plant height, biomass, root length, and root surface area. Furthermore, the nutrient content of maize organs increased by 1.1–29.7%. Partial least squares models confirmed that earthworm activity alleviated the stress effect of microplastic pollution on plant growth by improving soil structure, fertility, and microbial abundance and diversity. The greatest effect on maize growth was observed with the improvement of soil physical-chemical properties. Our results suggest that medium densities of earthworms have the greatest soil improvement effect and provide an important basis for bioremediation of farmland contaminated by microplastics and promoting green and efficient development in agriculture.

The temporal profile of GH1 gene abundance and the shift in GH1 cellulase-producing microbial communities during vermicomposting of corn stover and cow dung.

Vermicomposting is a promising method for corn stover management to achieve bioresource recovery and environmental protection. Most β-glucosidases, which limit the cellulose degradation rate during vermicomposting of corn stover, belong to glycoside hydrolase family 1 (GH1). This study was conducted with different earthworm densities to quantify the GH1 gene abundance and investigate the evolution of GH1 cellulase-producing microbial communities using qPCR and pyrosequencing. The results showed that β-glucosidase activity, GH1 gene abundance, TOC, and microbial communities carrying the GH1 gene were affected by processing time and earthworm density. After introducing earthworms, β-glucosidase activity increased to 1.90-2.13 U/g from 0.54 U/g. The GH1 gene abundance of treatments with earthworms (5.82E+09-6.70E+09 copies/g) was significantly higher than that of treatments without earthworms (2.48E+09 copies/g) on Day 45. Earthworms increased the richness of microbial communities. The relative abundances of Sphingobium and Dyadobacter, which are dominant genera harboring the GH1 gene, were increased by earthworms to peak values of 23.90% and 11.20%, respectively. Correlation analysis showed that Sphingobium, Dyadobacter, Trichoderma, and Starkeya were positively associated with β-glucosidases. This work sheds new light on the mechanism of cellulose degradation during vermicomposting at the molecular level.

Kepadatan Populasi Cacing Tanah (Haplotaxida: Lumbricina) Sebagai Bioindikator Kesuburan Tanah Di Kebun Nusantara PT. Cinquer Agro Nusantara

Earthworms (Haplotaxida: Lumbricina) are bioindicators of soil fertility. Agricultural systems applied to an agricultural area can affect the presence of earthworms there. This study aims to determine the density of earthworms in plantations owned by PT. Cinquer Agro Nusantara with Agroforestry-Organic, Monoculture-Semiorganic, Polyculture-Organic, Monoculture-Organic, and farmer-owned plantations with Monoculture-Inorganic system. The plot is determined with line transect method and samples of earthworms are taken with hand sorting method. Data analysis was carried out with ANOVA and Post Hoc T-Test with Bonferroni correction. The results showed that the density of earthworms in pepper plantations with Agroforestry-Organic, Monoculture-Semi-organic, Polyculture-Organic, and Monoculture-Organic farming systems is significantly greater than pepper plantations with Monoculture-Inorganic farming system.

Impacts of long-term organic production on soil fauna in boreal dairy and cereal farming

Intensified arable farming results in fewer functional groups of soil biota with decreased biodiversity. Organic farming with slurry fertilization and long crop rotation cycles favors soil fauna diversity under tropical and temperate conditions. Faunal responses to agricultural practices in northern latitudes may, however, differ from those in southern latitudes due to different soil types, climatic conditions, and intensity of management. We investigated the abundance and diversity of soil fauna communities (nematodes, microarthropods, enchytraeids and earthworms) in a boreal sandy soil in replicated organically and conventionally cultivated field blocks that simulated cultivation in a cereal farm and in a forage producing dairy farm. In addition to traditional methods, we investigated nematode diversity using DNA metabarcoding. The results show that organic production system did not unequivocally result in higher abundance and diversity of soil fauna compared with conventional production systems, neither in the cereal nor the dairy farming type. Instead, abundances of all soil fauna groups were typically higher in the dairy than in the cereal farming type irrespective of production system. This holds up for all functional groups of nematodes except omnivores, all four orders of Acari present, two out of the six families of Collembola, the total number of enchytraeids and density of earthworms. Nematode diversity, measured as average ZOTU number, was in conventionally cultivated cereal farming type an order of magnitude lower than in other production and farming type combinations. Of the various differences between farming types, the crop species was the most important one as it defines the management practice and thus the soil conditions where soil biota lives. Our findings underline that when comparing soil faunal communities under organic and conventional cultivation, the differences between farming types need to be considered in addition to the production system as they can have an overriding importance across the food web.

Soil functional indicators in different development stages of an oak (Quercus castaneifolia C.A. Mey.) stand

As the remaining widespread Tertiary forests, the Hyrcanian forest of northern Iran, together with the south-eastern forests of Azerbaijan, are the last habitat ecosystems for chestnut-leaved oak species (Quercus castaneifolia C.A. Mey.) in the world. The present study aimed to investigate the influence of oak forest stands with different development stages (i.e. initial, optimal and decay) on soil functional indicators, i.e. fertility and biological activities, in Loveh forest, northern Iran. During the summer season, a total of 18 forest floor and topsoil samples (30 × 30 × 10 cm) from each development stage were transferred to the laboratory. In order to obtain a temporal pattern of soil climate, biota and microbial characteristics, samples were also collected during the autumn season. Concerning the independent individual factors, including development stage, season, and development stage × season, two-way ANOVA and general linear models as well as a PCA were applied. The first factor explained the observed variations in the total earthworm density (36.3 %) and biomass (33.5 %), acarina (47.3 %), nematodes (52.3 %), protozoa (54.6 %), bacteria (60.9 %), fungi (53.4 %), basal respiration (35.9 %), substrate-induced respiration (37.2 %), microbial biomass C (25.7 %), microbial biomass N (35.4 %), and the ratio of microbial biomass C to microbial biomass N (18.8 %). In contrast, the season factor explained changes in soil water content (31.2 %), temperature (22.6 %) and collembola density (59.7 %). Based on heat plots (as a part of the principal component analysis output) of studied properties, the decay stage of the oak stand created hot spots of soil functional indicators in the study area. Although all forest stand stages of the oak have an important ecological role, and place value in the evolutionary process, the old-growth (i.e. decay) stage is crucial for the soil functions exhibiting the highest fertility and biological relevance. As a management strategy, forest decision-makers may be advised to introduce diverse tree species into the stands, especially in areas with patchy canopy, and thus enhance forest soil microbial activity, nutrient cycles and, finally, variation of soil properties within the area (pedodiversity).

Linked disturbance in the temperate forest: Earthworms, deer, and canopy gaps.

Despite the large body of theory concerning multiple disturbances, relatively few attempts have been made to test the theoretical assumptions of how and if disturbances interact. Of particular importance is whether disturbance events are linked, as this can influence the probability and intensity of ecological change. Disturbances are linked when one disturbance event increases or decreases the likelihood or extent of another. To this end, we used two long-term, multi-disturbance experiments in northern Wisconsin to determine whether earthworm invasion is linked to canopy gap creation and white-tailed deer browsing. These three disturbances are common and influential within North American temperate forests, making any interactions among them particularly important to understand. We expected both deer and canopy gaps to favor invasive earthworms, particularly species that live close to or on the soil surface. However, we found only partial support of our hypotheses, as both deer exclosures and canopy gaps decreased earthworms in each experiment. Further, earthworm density increased the most over time in areas far from the gap center and in areas with deer present. Deer exclosures primarily decreased Aporrectodea and Lumbricus species, while gaps decreased Dendrobaena and Lumbricus species. Our findings show that earthworm invasion is linked to deer presence and gap-creating disturbances, which provides new insight in multiple disturbance theory, aboveground-belowground dynamics, and temperate forest management.

Soil macrofauna under laying hens’ grazed fields in two different agroecosystems in Portugal

Abstract Although chickens can improve the chemical properties of soil through the deposition of excreta, their effects on soil macrofauna are poorly known. This work assessed the effects of grazing indigenous laying hens on soil macrofauna of two agroecosystems in Portugal: an organic horticultural field and a conventional orchard. At the horticultural field, laying hens were used to control weeds and the results were compared with those of two other weed control treatments: mechanical (rototiller) and thermal (flame weeding). At the orchard, the effects of hens were compared to that of the orchard understory vegetation, as a control. Soil epigeic macrofauna was collected in both locations, and earthworms were only collected in the horticultural field. Relative to the other treatments, grazing in the horticultural field increased the density of earthworms in the medium term (ranging from 150 to 625 earthworms/m2), without harming the density and diversity of epigeic macrofauna. However, at the orchard, the grazed soils presented lower soil epigeic macrofauna diversity, as well as significantly lower density of spiders than the control (4.67 vs 8.67 individuals/sample, respectively). These results suggest that the grazing effects can be affected by several factors, including the type of agroecosystem and farm management. Further research is required to optimize grazing management in different farming systems, considering animal density and grazing duration, thus ensuring the best contributions of chickens to soil fertility.

Effects of Hydrologic Regime Changes on a Taxonomic and Functional Trait Structure of Earthworm Communities in Mountain Wetlands.

Disturbances, both natural and anthropogenic, influence the patterning of species and species traits. The shift in species composition and distribution pattern of functional traits can demonstrate if the community is resistant, sensitive or resilient to the disturbance. Based on species- and trait-based approaches, we examined the response of the earthworm community to changing hydrologic conditions caused by the artificial drainage of mountain fens, in which cumulative effects of disturbance events over space and time are much less dynamic than in riverine wetlands. We hypothesized that the drainage-related changes of mountain fen peat soils have an effect on the earthworm community composition and its functional structure. We assume that the shift in species composition and value of community-weighted functional traits reflect changes in the resilience or resistance of the earthworm community to environmental change. Our results demonstrate that the total density of earthworms was almost three times lower under drained conditions compared to natural ones. Artificial drainage of fens had a neutral effect on the species-based diversity indices. However, there were species-specific traits that responded to hydrologic changes and which led to the species' replacements and to the co-occurrence of eurytopic, surface-browsing and more drought- and low-pH-resistant earthworm species in the drained fens. Based on these results, we conclude that abiotic-based environmental filtering was the main process responsible for sorting earthworms according to species and traits in the disturbed hydrologic conditions. The greater earthworm functional trait variations in semi-natural hydrologic conditions emphasizes the impact of transient dynamics in an altered disturbance regime on the earthworm assembly. Results also showed that in the changing hydrologic conditions of mountain fens, the functional trait approach revealed only slightly more predictive power than the taxonomic one, but it proved better with processes responsible for earthworm species filtering.

Impact of No-Tillage on Soil Invertebrate Communities in the Southern Forest Steppe of West Siberia: Preliminary Research

The aim of our study is to assess changes in soil macroinvertebrate biodiversity when conventional tillage (CT) is replaced by no-tillage (NT) in agroecosystems of the southern part of the West Siberian forest steppe. The research was conducted in the Novosibirsk region at the end of May 2017, May 2018, and in June 2018. The agricultural plots with CT and NT were located close to each other on identical soils, at a distance of about 200 m from the nearest forest shelterbelts. NT technology has been applied on the experimental plot since 2007. Sampling of invertebrates was conducted in two ways, namely soil sampling and pitfall trapping. The majority of basic physicochemical properties of soil were the same or similar between the CT and NT plots. However, depending on the type of tillage, different soil invertebrate communities had already developed in the control (CT) and experimental (NT) plots during this time. The community of the CT plot includes a large number of flying predatory Carabidae species typical of early successional stages (such as Bembidion properans and B. quadrimaculatum, Poecilus spp.) and phytophages, i.e., larvae of Elateridae. The NT plot has significantly higher density and species richness of earthworms (Eisenia nordenskioldi and synanthropic E. fetida in the NT plot versus one individual of E. nordenskioldi in the CT plot). The NT plot has a significantly richer and more abundant assemblage of spiders (especially in spring) and a poor assemblage of insect predators (except for the superdominant ground beetle Poecilus cupreus and the subdominant P. versicolor in summer 2018). Large numbers of larvae of some carabids (e.g., Amara consularis) were found in the NT soil, suggesting that they complete a full life cycle in this habitat.

Recycling and valorization of distilled grape marc through vermicomposting: a pilot-scale study

The present study sought to evaluate the effectiveness of vermicomposting for the valorization of distilled grape marc, one of the main solid by-products of the winery sector during a 56-day pilot-scale trial. The increase in the density and biomass of earthworms (Eisenia andrei) during the earlier stages of the process reflected the suitability of the distilled marc (Vitis vinifera L. cv. Mencía) as feedstock in order to sustain large earthworm populations on a pilot-scale level. Supporting this, from 14 days onwards the pH of Mencía distilled marc fell within weak-alkaline levels and the electrical conductivity was between 0.21 and 0.11 mS cm−2 providing optimum conditions for earthworm growth. A rapid decrease in microbial activity as well as in the content of total polyphenols, both indicative of stabilized materials was also recorded after 14 days of vermicomposting. Moreover, the content of macro- and micronutrients in the end product matched with those considered to have the quality criteria of a good vermicompost with respect to plant health and safe agricultural use. Altogether, it underlines the feasibility of vermicomposting as an environment-friendly approach for the biological stabilization of distilled grape marc fulfilling both environmental protection and fertilizer production.

Tree-distance and tree-species effects on soil biota in a temperate agroforestry system

AimsCropland agroforestry systems are land-use systems with numerous environmental advantages over monoculture croplands including promotion of soil life. This study aimed to investigate tree-species and tree-distance effects on soil biota in a temperate agroforestry system.MethodsOur study was conducted at a paired alley-cropping and monoculture cropland system. The tree rows of the agroforestry system comprised of blocks of poplar Fritzi Pauley, poplar Max 1 or black locust. Within the agroforestry system, soil microbial and earthworm communities were collected along transects spanning from the center of the tree rows into the crop rows. Archaea, bacteria, and fungi were quantified using real-time PCR. The community composition of fungi and earthworms was deciphered using amplicon sequencing and morphological identification, respectively.ResultsTree rows promoted the abundance of bacteria and earthworms, which we attribute mainly to tree litter input and the absence of tillage. Fungal community composition was altered by the tree rows, resulting in an increased proportion of ectomycorrhizal fungi in the tree-row associated mycobiome. The proportion of Blumeria graminis, the causal agent of powdery mildew, increased with increasing distance from the trees. We suggest that enhanced microbial antagonism, increased earthworm densities and/or altered microclimate contributed to the suppression of B. graminis in vicinity of the trees. Tree-species effect had a minor influence on the abundance and composition of soil communities at our study site.ConclusionsIn comparison to monoculture cropland, agroforestry benefits the abundance, diversity, and function of soil biota and may enhance soil suppressiveness.

Effects of Energy Crop Monocultures and Sewage Sludge Fertiliser on Soils and Earthworm Community Attributes

Biomass is one of the most significant renewable energy sources. Doubts arise from large-area plantations of energy monocultures, which can lead to the depletion of, and a decrease in, soil biodiversity. Community association analyses of Lumbricidae may help to indicate environmental change. Therefore, the study objectives were to determine the qualitative and quantitative diversity of Lumbricids in plantations of energy crops—basket willow (Salix viminalis L.), foxglove tree (Paulownia tomentosa Steud.), and black locust (Robinia pseudoacacia L.)—by investigating the following cultivation treatments: SV and SVSS—S. viminalis without (w/o) and with the addition of sewage sludge to the soil (+SS); PT and PTSS—P. tomentosaw/o and + SS; RP and RPSS—R. pseudoacaciaw/o and +SS; and MW—meadow community. A significantly higher density (p < 0.05) and biomass (p < 0.05) of earthworms were found in the SV and SVSS plantations than in other sites. The application of sewage sludge contributed to a significant increase in the mean number and biomass of all Lumbricids within cultivations of S. viminalis and R. pseudoacacia, which were significantly higher than those in the control site. This work suggests that woody energy crop production with an appropriate selection of plants and fertilisation can be a favourable habitat for the development of earthworm populations.

Effect of Imidacloprid and Chloropyrifos Toxicity on Earthworm Amynthas alexandri Under Laboratory Conditions

Aim: To highlight the impact of commonly used insecticides on earthworms as they represent the largest fraction of soil biomass. Earthworms were exposed to different concentrations of insecticides using a contact filter paper test method. Materials and Methods: Acute toxicity was tested for 48 hr using a filter paper contact toxicity test (Whatman filter paper no.1). After 48 hexposure, morphological changes and DNA Damage were observed and the treated earthworms were fixed with 10% (w/v) for 24 h in formalin solution for the histological test. Results: Based on Median lethal concentration, the insecticides applied at the field recommended dose in the study are classified as super toxic in the contact filter toxicity test. The highest mortality was caused by Imidacloprid and found to be the most toxic. Conclusion: Insecticides even when used at field recommended doses cause lethal effects on various activities of earthworms including DNA damage and reduced reproductive potential leading to a poor density of earthworms including poor soil fertility. The altered morphological and histological changes were also observed when earthworms get direct or indirect exposure to insecticides. Therefore, it is important to standardize and rationalize the use of pesticides simultaneously a higher degree of awareness and education as needed at all levels including the vendors and producers of pesticides.

Multidimensional stoichiometric mismatch explains differences in detritivore biomass across three forest types.

The ecological stoichiometry theory provides a framework to understand organism fitness and population dynamics based on stoichiometric mismatch between organisms and their resources. Recent studies have revealed that different soil animals occupy distinct multidimensional stoichiometric niches (MSNs), which likely determine their specific stoichiometric mismatches and population responses facing resource changes. The goals of the present study are to examine how long-term forest plantations affect multidimensional elemental contents of litter and detritivores and the population size of detritivores that occupy distinct MSNs. We evaluated the contents of 10 elements of two detritivore taxa (lumbricid earthworms and julid millipedes) and their litter resources, quantified their MSNs and the multidimensional stoichiometric mismatches, and examined how such mismatch patterns influence the density and total biomass of detritivores across three forest types spanning from natural forests (oak forest) to plantations (pine and larch forests). Sixty-year pine plantations changed the multidimensional elemental contents of litter, but did not influence the elemental contents of the two detritivore taxa. Earthworms and millipedes exhibited distinct patterns of MSNs and stoichiometric mismatches, but they both experienced severer stoichiometric mismatches in pine plantations than in oak forests and larch plantations. Such stoichiometric mismatches led to lower density and biomass of both earthworms and millipedes in pine plantations. In other words, under conditions of low litter quality and severe stoichiometric mismatches in pine plantations, detritivores maintained their body elemental contents but decreased their population biomass. Our study illustrates the success in using the multidimensional stoichiometric framework to understand the impact of forest plantations on animal population dynamics, which may serve as a useful tool in addressing ecosystem responses to global environmental changes.

Earthworm community structure and population dynamics at Minkong forest of Mokokchung, Nagaland, India

Aim: The present study was undertaken to assess the seasonal variations of density, biomass and community characteristics of earthworms in two different types of forest at Minkong area, Mokokchung. Methodology: The survey was conducted during the period from January 2019-February 2020 in two areas viz., mixed forest and plantation. Standard methods were followed to determine the ecological categories of earthworms, density and biomass, relative abundance and species richness as well as for determination of different soil parameters viz., pH, moisture, bulk density, organic carbon, total and available nitrogen, available phosphorus and potassium. Results: 12 number earthworm species viz., Amynthas corticis (Kinberg), Amynthus gracilis (Kinberg), Drawida assamensis (Gates), Drawida hodgarti (Stephenson), Drawida nepalensis (Michaelsen), Drawida sp., Eutyphoeus assamensis (Stephenson), Eutyphoeus festivus (Gates) Metaphire houlleti (Perrier), Perionyx excavatus (Perrier), Perionyx simlaensis (Michaelsen) and Pontoscolex corethurus (Müller) were recorded. Dominant earthworm species in both the areas were D. nepalensis, P. excavatus, Drawida sp. and E. festivus. The Shannon diversity, Simpson diversity and Pielou’s species evenness were 2.17, 0.87 and 0.87 in mixed forest and 2.05, 0.86, 0.86 in plantation. The earthworm density and biomass were greater in plantation (276.74 ind m-2 and 338.47g m-2) compared to mixed forest (230.52 ind m-2 and 254.55 g m-2). Interpretation: As earthworm community characteristics differ depending on the type of forest, therefore, earthworm’ sdiversity and its indices can be used as an ecological indicator of anthropogenic disturbances and can help designing conservation programs for reclaiming the depleted areas. Key words: Biomass, Earthworm diversity, Minkong, Relative abundance, Subtropical ecosystem

Positive or neutral effects of biochar-compost mixtures on earthworm communities in a temperate cropping system

Biochar is increasingly considered an efficient amendment to improve soil fertility and store carbon in soils for climate change mitigation. However, few field studies have evaluated biochar impacts on soil fauna and especially earthworms in temperate areas despite their importance for soil structure and laboratory-based evidence of potential adverse effects. We investigated the effects of three biochars (from rapeseed, miscanthus and compost reject) in mixture with a green waste compost on the abundance and composition of earthworm communities during a three-year field experiment in northern France. Compost alone or biochar-compost mixtures were applied at 11.7 t dry matter ha−1 and compared to equivalent mineral fertilization. Biochar-compost mixtures did not affect total earthworm density and biomass, while contrasting effects concerning specific ecological groups were observed. Compost addition increased juvenile endogeic earthworm density roughly one month after amendment while no adverse short-term effects of biochar-compost mixtures were observed. Two years after amendment application, anecic earthworm density was higher for the mixture with compost and biochar from compost rejects, which also resulted in the highest soil organic carbon concentrations. We conclude that biochar-compost mixtures at low but more economically viable biochar application rates could be used as an increasingly understood beneficial soil amendment under temperate climate conditions without adverse effects on earthworm communities.

Impact of Aboveground Vegetation on Abundance, Diversity, and Biomass of Earthworms in Selected Land Use Systems as a Model of Synchrony between Aboveground and Belowground Habitats in Mid-Himalaya, India

The population status and biomass of earthworms were studied in three different land use systems of pasture (Pa), silvopasture (SP), and mixed evergreen forest (MEF) from 2019–2020 in the Solan district of Himachal Pradesh, India. The aim of this study was to assess the population status of earthworms and investigate how different land use systems influence their abundance, diversity, and biomass. Earthworms and soil were sampled using the Tropical Soil Biology and Fertility (TSBF) method in all seasons (winter, spring, summer, monsoon, and autumn). The physicochemical properties of the soil were analyzed to evaluate their effects on the diversity, biomass, and density of animals. The diversity status parameters, such as the Shannon diversity index (H′), Margalef richness index (R), evenness (J′), and dominance index (D), were computed. A total of seven earthworm species, belonging to four families, namely, Amynthas corticis, Aporrectodea rosea, Drawida japonica, Eisenia fetida, Metaphire birmanica, Metaphire houlleti, and Lennogaster pusillus, were identified from all three land use systems. The lowest Shannon diversity index (H′), Margalef index (R), and evenness (J′) index values were registered in MEF (H′ = 0.661, R = 0.762, J′ = 0.369) compared to those in Pa (H′ = 1.25, R = 1.165, J′ = 0.696) and SP (H′ = 0.99, R = 0.883, J′ = 0.552), implying that MEF is the least diversified land system. In contrast, the highest dominance index (D) value was registered in MEF (Pa = 0.39, SP = 0.53, MEF = 0.67), which again showed that MEF is the least diversified land system. The highest values of abundance and biomass were recorded in MEF (754.15 individuals m−2 and 156.02 g m−2), followed by SP (306.13 individuals m−2 and 124.84 g m−2) and Pa (77.87 individuals m−2 and 31.82 g m−2). Both the density and biomass of earthworms increased from Pa to MEF (Pa < SP < MEF). This study is novel because it revealed that the diversity and productivity (biomass and abundance) values of earthworms were negatively correlated (as diversity increased, productivity decreased; as diversity decreased, productivity increased). The total values of abundance and biomass of earthworms in the three land use systems indicated perfect synchrony between aboveground and belowground habitats, whereas the diversity values revealed that MEF was dominated by one or two species and the least diversified. Therefore, for sustainable belowground productivity, aboveground conservation is recommended, and vice versa, regardless of diversity.

Changes in soil carbon mineralization related to earthworm activity depend on the time since inoculation and their density in soil

Earthworms play a key role in soil carbon mineralization, but their effect is highly uncertain and suspected to vary as a function of several factors, particularly the earthworm density and time from earthworm inoculation. We conducted a meta-analysis considering these factors based on 42 experiments comparing carbon mineralization in the absence and presence of earthworms at different times. The results reveal an average carbon mineralization increase of 24% (sd 41%) in the presence of earthworms with an initial median earthworm density of 1.95 mg/g soil DM (Dry Mass) (sd 48%). We show that carbon mineralization due to earthworms was related to their density and time from inoculation. From a simple regression model using these two variables, the estimated impact of earthworms on carbon mineralization was 20% increase from 0 to 60 days and 14% decrease at day 350 for a density of worms commonly found in soils (0.5 mg/g soil DM). Finally, we proposed a simple equation that could be used in organic matter decomposition models that do not take macrofauna into account.