Earthworm Populations Research Articles

Earthworm eco-physiological characteristics and quantification of earthworm feeding in vermifiltration system for sewage sludge stabilization using stable isotopic natural abundance

Previous studies showed that the presence of earthworm improves treatment performance of vermifilter (VF) for sewage sludge stabilization, but earthworm eco-physiological characteristics and effects in VF were not fully investigated. In this study, earthworm population, enzymatic activity, gut microbial community and stable isotopic abundance were investigated in the VF. Results showed that biomass, average weight, number and alkaline phosphatase activity of the earthworms tended to decrease, while protein content and activities of peroxidase and catalase had an increasing tendency as the VF depth. Earthworm gut microbial communities were dominated by Gammaproteobacteria, and the percentages arrived to 76–92% of the microbial species detected. 15N and 13C natural abundance of the earthworms decreased with operation time, and increased as the VF depth. Quantitative analysis using δ15N showed that earthworm feeding and earthworm–microorganism interaction were responsible for approximately 21% and 79%, respectively, of the enhanced volatile suspended solid reduction due to the presence of earthworm. The finding provides a quantitative insight into how earthworms influence on sewage sludge stabilization in vermifiltration system.

Deciduous woodland exposed to elevated atmospheric CO2 has species-specific impacts on anecic earthworms

Elevated atmospheric CO2 induced reductions in litter quality can adversely affect earthworms. However, this understanding is based on laboratory rather than field research and relates to single earthworm and tree species. Here earthworm populations were investigated under Alnus glutinosa, Betula pendula, and Fagus sylvatica in a Free Air Carbon dioxide Enrichment field experiment. Litters from this experiment were also fed to Lumbricus terrestris L. at two rates with live weight change and cast properties assessed. Elevated CO2 (580ppmv) reduced litter N (−12%) with a corresponding increase in C:N ratio, especially for A. glutinosa. In the field, elevated CO2 caused a shift in overall population composition, mainly characterised by reduced anecic biomass (–25%); endogeic and epigeic species were less affected. CO2 effects on total biomass were most pronounced for A. glutinosa (e.g. field total biomass −47% vs. −11% overall). Growth of L. terrestris was lower when fed elevated CO2 litter (−18%), although increased inputs of A. glutinosa litter mitigated this effect. In mesocosms, fresh cast respiration was lower (−14%) for elevated CO2 litter, an effect more pronounced for A. glutinosa (−24%). When normalised for C content, elevated CO2 effects on cast respiration were again negative and most marked for A. glutinosa litter. Litter N concentration, and possibly ease of litter mineralisation were factors affecting litter resource quality Litter N and P concentrations varied with A. glutinosa>B. pendula>F. sylvatica; F. sylvatica had the highest cellulose content. Field earthworm biomass was higher under A. glutinosa compared with B. pendula and F. sylvatica (+17 and +70%, respectively); live weight increased with A. glutinosa litter in the feeding trial almost three times more than for B. pendula, whereas it decreased for F. sylvatica. Cast respiration was highest for A. glutinosa, intermediate for B. pendula (ca. −36%) and lowest for F. sylvatica (ca. −78%). Earthworm responses to elevated CO2 were complex, being characteristic of individual tree and earthworm species; responses were more adverse for trees with higher quality litter and for anecic earthworms.

THE INFLUENCE OF RED WORMS (E. FOETIDA) ON COMPOST’S FERTILIZING PROPERTIES

Composting is becoming a more and more common way of biodegradable waste disposal. Composts should be characterized by high content of nutrients and low amount of pollutants. Vermicompost is a compost produced by overpopulated culture of earthworm Eisenia foetida (Savigny 1826). World scientific literature states that vermicompost has a high fertilizing value which often exceeds such value of conventional composts. The results showed that vermicompost has a much higher fertilizing value than the compost produced by the traditional pile method. However, prism vermicompost created with the participation of a less concentrated population of earthworms has an intermediate value as a fertilizer (nitrogen and heavy metals), it could be assessed as a lower value product due to the lower content of potassium and phosphorus than the material obtained without earthworms.

Effects of silver nanoparticles (NM‐300K) onLumbricus rubellusearthworms and particle characterization in relevant test matrices including soil

The impact of silver nanoparticles (AgNP; at 0 mg Ag/kg, 1.5 mg Ag/kg, 15.4 mg Ag/kg, and 154 mg Ag/kg soil) and silver nitrate (AgNO3 ; 15.4 mg Ag/kg soil) on earthworms, Lumbricus rubellus, was assessed. A 4-wk exposure to the highest AgNP treatment reduced growth and reproduction compared with the control. Silver nitrate (AgNO3 ) exposure also impaired reproduction, but not as much as the highest AgNP treatment. Long-term exposure to the highest AgNP treatment caused complete juvenile mortality. All AgNP treatments induced tissue pathology. Population modeling demonstrated reduced population growth rates for the AgNP and AgNO3 treatments, and no population growth at the highest AgNP treatment because of juvenile mortality. Analysis of AgNP treated soil samples revealed that single AgNP and AgNP clusters were present in the soil, and that the total Ag in soil porewater remained high throughout the long-term experiment. In addition, immune cells (coelomocytes) of earthworms showed sensitivity to both AgNP and AgNO3 in vitro. Overall, the present study indicates that AgNP exposure may affect earthworm populations and that the exposure may be prolonged because of the release of a dissolved Ag fraction to soil porewater.

Effect of tillage on earthworms over short- and medium-term in conventional and organic farming

Earthworms play an important role in many soil functions and are affected by soil tillage in agricultural soils. However, effects of tillage on earthworms are often studied without considering species and their interactions with soil properties. Furthermore, many field studies are based on one-time samplings that do not allow for characterisation of temporal variation. The current study monitored the short (up to 53 days) and medium term (up to 4 years) effects of soil tillage on earthworms in conventional and organic farming. Earthworm abundances decreased one and three weeks after mouldboard ploughing in both conventional and organic farming, suggesting direct and indirect mechanisms. However, the medium-term study revealed that earthworm populations in mouldboard ploughing systems recovered by spring. The endogeic species Aporrectodea caliginosa strongly dominated the earthworm community (76%), whereas anecic species remained <1% of all earthworms in all tillage and farming systems over the entire study. In conventional farming, mean total earthworm abundance was not significantly different in reduced tillage (153m−2) than mouldboard ploughing (MP; 130m−2). However, reduced tillage in conventional farming significantly increased the epigeic species Lumbricus rubellus from 0.1m−2 in mouldboard ploughing to 9m−2 averaged over 4 years. Contrastingly, in organic farming mean total earthworm abundance was 45% lower in reduced tillage (297m−2) than MP (430m−2), across all sampling dates over the medium-term study (significant at 3 of 6 sampling dates). Reduced tillage in organic farming decreased A. caliginosa from 304m−2 in mouldboard ploughing to 169m−2 averaged over 4 years (significant at all sampling dates). Multivariate analysis revealed clear separation between farming and tillage systems. Earthworm species abundances, soil moisture, and soil organic matter were positively correlated, whereas earthworm abundances and penetration resistance where negatively correlated. Variability demonstrated between sampling dates highlights the importance of multiple samplings in time to ascertain management effects on earthworms. Findings indicate that a reduction in tillage intensity in conventional farming affects earthworms differently than in organic farming. Differing earthworm species or ecological group response to interactions between soil tillage, crop, and organic matter management in conventional and organic farming has implications for management to maximise soil ecosystem functions.

Acclimation of earthworms to chemicals in anthropogenic landscapes, physiological mechanisms and soil ecological implications

Because earthworms sustain soil functioning and fertility, there is a need to advance the knowledge of their adaptation potential to chemicals in anthropogenic landscapes. Our hypothesis is that there is acclimation to organic chemicals (pesticides) in earthworms that durably persist under conventional farming in anthropogenic landscapes. The adaptation capability of two populations of earthworms (Aporectodea caliginosa) having a different chemical exposure history, – one originating from 20 years of organic farming (naïve population) and another from 20 years of conventional farming (pre-exposed population) – to cope with soil organic pollutant (Opus®, epoxiconazole a worldwide used fungicide) were investigated. Several complementary metabolic and energetic endpoints were followed, and cast production was assessed as a behavioural biomarker related to earthworms ecological role for the soil. Basal metabolism reflected by respiration rate was increased in both fungicide-exposed worms compared to controls. Glycogen resources were decreased in the same proportion in the two populations but more rapidly for the naïve (7 days) than for the pre-exposed population (28 days). Soluble protein and most amino-acids contents increased in the pre-exposed population only, suggesting a detoxification mechanism. Metabolomic profiles showed a cut-off between fungicide-exposed and control groups in the pre-exposed earthworms only, with an increase in most of the metabolites. Exposure to a low dose of epoxiconazole increased cast production of pre-exposed earthworms, and this resulted in an increase in pesticide disappearance. As far as we know, this is the first study which evidenced there is an acclimation to an agricultural chemical in earthworms derived from conventional farming that also relates to a change in their burrowing behaviour, and for which larger consequences for the soil ecosystem need to be addressed. This original finding is of major interest in the frame of ecosystem resilience to global changes. Whether this physiological adaptation is a general pattern of response against fungicides or other pesticides would need to be confirmed with other molecules and agricultural contexts.

Wild boar density drives Metastrongylus infection in earthworm.

Larvae of Metastrongylus spp. lungworms infect wild boar (Sus scrofa) definitive hosts through earthworms (Lumbricidae). We compared the abundance and Metastrongylus spp. larval infection measures of earthworms between two areas (both in Zselic, Hungary, 2012) characterized by markedly different wild boar population densities. Estimated wild boar density was 0.03 animal/ha in free range area and 1.03 animal/ha in enclosure. The mean abundance of earthworm populations (mostly Allolobophora, Aporrectodea, and Lumbricus spp.) was assessed by analysing 140-140 soil samples. The assesment of Metastrongylus spp. larval infection measures was based on cca 100-100 earthworms derived from the two areas. The abundance of earthworms and their Metastrongylus spp. larval infection measures (prevalence and mean intensity) were significantly lower in the free range than in the enclosure. Furthermore, using a finer scale within the enclosure, we compared wild boar feeding sites (n = 30) to other sites (n = 75). Earthworm populations were significantly more abundant and carried significantly more prevalent and more abundant larval lungworm infections at the former sites. These results suggest that high wild boar density and forage supplementation in enclosures increase both the abundance and the larval Metastrongylus infections of earthworms.

Impact of land protection in soil quality properties and in earthworm biomass in Venezuelan savannas

We studied soil parameters and the earthworm biomass and density in a protected savanna (PS) from fire and cattle raising for more than forty years located at Estacion Biologica de los Llanos, Venezuela (EBLL), and an adjacent non-protected savanna (NS) under frequent burning and agricultural activities, located less than 1 km apart. Earthworm sampling was carried out at the end of the dry season (April), and at the peak of the wet season (July-August) using a hand sorting extraction method. In each plot, five to seven sampling units were selected corresponding to soil monoliths of 25x25x30 cm. The main physical, chemical, microbial (biomass) and enzymatic activities of soils in both systems were estimated. The presence of an abundant litter layer under the tree canopies in the PS have increased the soil water retention capacity, the organic-C, C-microbial biomass, dehydrogenase activity and fertility levels respect NS. This may allow for an increase in the density and biomass of earthworms in the PS compared with the adjacent NS. The systems were characterized by abundance in juvenile individuals belonging to the Glossoscolecidae family; two different morphotypes of the genus Aicodrilus were registered. Earthworms found were located in an endo-anecic ecological category. Results suggest that, agricultural management in savannas by modification of physical and biochemical soil properties can decrease an important fraction of pedofauna, particularly their earthworm communities. However, earthworm populations and soil quality indicators can be restored after long-term protection.

STRUKTUR POPULASI CACING TANAH DI HUTAN SEKUNDER DAN AGROFORESTRI KOPI DESA KUTAGUGUNG KECAMATAN NAMAN TERAN KABUPATEN KARO

Research on the structure population of earthworm in secondary forest and coffee agroforestry Kutagugung Village, District Naman Teran, Karo, North Sumatra was conducted in January 2013. The aim of research was to determinate type earthworm, populations and its relation to environmental conditions. The method used is purposive random sampling with square method, hand sorting and environmental conditions (temperature, pH, rH, C-organik, N, P dan K). Amynthas sp., Pheretima sp. and Pontoscolex corethrurus found at both locations, while Peryonix sp. only found in coffee agroforestry. The highest density found in coffee agroforestry (283.73 ind/m2) followed by secondary forest (78.93 ind/m2). Types of earthworm bioindicator in secondary forest is Pontoscolex corethrurus (KR= 60.81%, FK= 60%) and Pheretima sp. (KR= 36.49%, FK= 53%), whereas in the coffee agroforestry only found Pontoscolex corethrurus (KR= 91.73%, FK= 100%). Pearson correlation analysis results indicate the number of individual earthworms were significantly positively correlated to the secondary forest soil pH (P= 0.544, α= 0.05). Keywords: coffee agroforestry, district karo, earth worm, population, secondary forest

Contribution of anecic earthworms to biopore formation during cultivation of perennial ley crops

Abstract Large sized biopores (diameter >2 mm) in the subsoil can be created by tap roots, which leave voids after their decay, or by the burrowing activity of anecic earthworms which may benefit from the temporary lack in tillage in perennial cropping systems. However, the interactions between root growth and earthworm activity in the process of biopore formation during perennial ley cropping are not well understood. The aim of this field study was to quantify the development of the abundance of the anecic earthworm Lumbricus terrestris and the biopore density during the cultivation of lucerne ( Medicago sativa L.), chicory ( Cichorium intybus L.) and tall fescue ( Festuca arundinacea Schreb.) grown for either one, two or three years. An increased abundance of L. terrestris was already recorded after two years of continuous ley when compared with one year cultivation. The ley crop species had only minor influence on the abundance of L. terrestris . Biopore densities of both diameter classes under study (2–5 mm and >5 mm) were not significantly affected by the duration of ley cropping. In contrast, biopore densities were influenced by ley crop species. More biopores of diameter class 2–5 mm were recorded after chicory than after fescue. Lucerne cropping resulted in intermediate biopore density. Additionally, in an incubation experiment under field conditions, we quantified whether L. terrestris preferentially created new biopores or colonized abandoned, previously existing ones. After three weeks of incubation, one third of the adult individuals incubated in the experimental area created new biopores at 0.4 m soil depth. A similar percentage of individuals colonized previously existing biopores, partially widening the lumen of smaller sized biopores. The remaining individuals remained in the topsoil. Sub-adult individuals rarely formed new pores. Half of the introduced sub-adults remained in the topsoil. We conclude that in crop rotations new biopores can be generated during perennial ley cropping by taproot systems of ley crops, but that a two to three- year period without tillage is not sufficient for populations of anecic earthworms to make a marked contribution to biopore density in the subsoil. The relevance of anecic earthworms for altering physical and chemical properties of biopores during ley cropping still needs further investigation.

Triclocarban, triclosan and its transformation product methyl triclosan in native earthworm species four years after a commercial-scale biosolids application

Triclocarban (TCC), triclosan (TCS) and methyl triclosan (Me-TCS) were detected in soil and the native population of earthworms of an agricultural field in Ottawa, Canada, about four years after a commercial-scale application of biosolids. In soil that received biosolids, TCC and TCS were detected at median concentrations of 13.0 and 1.5ng/g soil (d.w.), respectively, while Me-TCS, the transformation product of triclosan, was detected at a six-fold higher median concentration than its precursor. In earthworms collected at the biosolids-amended field-plot about four years post application, Me-TCS was also detected at higher concentrations (26 to 114ng/g tissue d.w.) than TCS (16–51ng/g) and TCC (4–53ng/g). These data provide evidence that not only parent compounds but also their transformation products need to be considered in faunal bioaccumulation studies. Moreover, the preliminary results for pooled earthworm samples from different ecological groups suggest that the degree of bioaccumulation of biosolids-associated contaminants may depend on the habitat and feeding behavior of the organisms.

Earthworms Produce phytochelatins in Response to Arsenic

Phytochelatins are small cysteine-rich non-ribosomal peptides that chelate soft metal and metalloid ions, such as cadmium and arsenic. They are widely produced by plants and microbes; phytochelatin synthase genes are also present in animal species from several different phyla, but there is still little known about whether these genes are functional in animals, and if so, whether they are metal-responsive. We analysed phytochelatin production by direct chemical analysis in Lumbricus rubellus earthworms exposed to arsenic for a 28 day period, and found that arsenic clearly induced phytochelatin production in a dose-dependent manner. It was necessary to measure the phytochelatin metabolite concentrations directly, as there was no upregulation of phytochelatin synthase gene expression after 28 days: phytochelatin synthesis appears not to be transcriptionally regulated in animals. A further untargetted metabolomic analysis also found changes in metabolites associated with the transsulfuration pathway, which channels sulfur flux from methionine for phytochelatin synthesis. There was no evidence of biological transformation of arsenic (e.g. into methylated species) as a result of laboratory arsenic exposure. Finally, we compared wild populations of earthworms sampled from the field, and found that both arsenic-contaminated and cadmium-contaminated mine site worms had elevated phytochelatin concentrations.

Effects of green manure herbage management and its digestate from biogas production on barley yield, N recovery, soil structure and earthworm populations

In repeatedly mown and mulched green manure leys, the mulched herbage contains substantial amounts of nitrogen (N), which may only slightly contribute to the following crops’ nutrient demand. The objective of the present work was to evaluate the effect of alternative strategies for green manure management on the yield and N recovery of a subsequent spring barley crop, and their short term effects on soil structure and earthworm populations. A field trial was run from 2008 to 2011 at four sites with contrasting soils under cold climate conditions. We compared several options for on-site herbage management and the application of anaerobically digested green manure herbage. Depending on the site, removal of green manure herbage reduced the barley grain yield by 0% to 33% compared to leaving it on-site. Applying digestate, containing 45% of the N in harvested herbage, as fertilizer for barley gave the same yields as when all herbage was mulched the preceding season. Overall, the apparent N recovery was enhanced from 7% when all herbage was mulched, to 16% when returned as digestate. A positive effect on earthworm density and biomass was seen after one season of retaining mulch material, rather than removing it. Digestate did not affect the earthworm population, but contributed to higher soil aggregate stability. In conclusion, for spring barley production after green manure ley, the digestate strategy increased N recovery and reduced the risk of N losses. The yield of the succeeding barley crop yield was reduced when N in herbage was not returned as mulch or digestate.

Reduction of pesticide use can increase earthworm populations in wheat crops in a European temperate region

Agricultural intensification has led to reduced soil biodiversity in arable lands. The potential benefits from organic farming and from low-input cropping systems have not yet been precisely assessed. Earthworm, having important agro-ecological functions, may be affected by pesticide applications, especially those species living mainly in the surface soil layer. We used a five-year experimental database including conventional and organic cropping systems to establish simple relationships between the Treatment Frequency Index – a phytosanitary indicator of pesticide pressure – and the abundance of three important earthworm species. We found that insecticides have more negative influence on earthworm species than herbicides and fungicides, and that species living in the soil's surface layer were the most affected by pesticides. Density of these earthworm species could be multiplied by a factor 1.5–4 if the Treatment Frequency Index was halved, as is currently required by some European regulations. Our results thus demonstrate that a reduction in pesticide application would increase earthworm population density in agricultural fields.

Curve numbers for long-term no-till corn and agricultural practices with high watershed infiltration

The Curve Number (CN) method is an engineering and land management tool for estimating surface runoff from rainstorms. We investigated CN under continuous long-term no-till corn (<i>Zea mays</i> L.; watershed WS191) and compared it with other potentially high infiltration agricultural practices using data from three experimental watersheds (average area = 0.74 ha [1.83 ac]) at the North Appalachian Experimental Watershed (NAEW) near Coshocton, Ohio. Practices compared were wheat (<i>Triticum aestivum</i> L.) and first- and second-year meadow as part of a 4-year corn–wheat–meadow–meadow rotation (CWMM), continuous meadow, and continuous no-till corn, mulch-tilled corn, and conventionally tilled corn (i.e., moldboard plow). Double-mass curves of runoff for no-till and permanent meadow documented the significant and immediate reduction in runoff from the no-till management. Runoff was generated at a rate of 4.9 mm y⁻¹ (0.19 in yr⁻¹) during the no-till period compared with permanent pasture at 44 mm y⁻¹ (1.73 in yr⁻¹) (no-till was 11% of the meadow rate). The asymptotic CN (CNi) for the 48-year record of continuous no-till corn practice at WS191 decreased substantially to 66.3 (−24.3 CN units) from the period of conventional corn in rotation on the same site. The Natural Resources Conservation Service handbook value for no-till CN was 16 CN units larger at 82. The larger than expected reduction in CN was probably due the presence of a thriving earthworm population and numerous earthworm-created macropores that enhance infiltration. The CN for the mulch-tilled corn culture treatment (74.6) was lower than conventional corn (90.6 largest) by 16 CN units. CN was surprisingly high (77.4) for a watershed in continuous meadow, which was similar to mulch-tilled corn. The wheat years in rotation also had some of the smallest CN values (63.7), suggesting a smaller CN for a practice similar to that used in organic agriculture today. Continuous no-till corn had a slightly larger CN (66.3) than meadow (61.9) in the CWMM rotation, suggesting that simple grass establishment can be as effective as long-term no-till to reduce runoff. CN of approximately 60 was the lowest found. The results are applicable for areas of similar terrain, management practices, geology, soils, subsoil permeability, and climate of the NAEW watersheds. Differences between handbook and measured CN suggest that local values are more representative than handbook values.

An energy budget agent-based model of earthworm populations and its application to study the effects of pesticides

Earthworms are important organisms in soil communities and so are used as model organisms in environmental risk assessments of chemicals. However current risk assessments of soil invertebrates are based on short-term laboratory studies, of limited ecological relevance, supplemented if necessary by site-specific field trials, which sometimes are challenging to apply across the whole agricultural landscape. Here, we investigate whether population responses to environmental stressors and pesticide exposure can be accurately predicted by combining energy budget and agent-based models (ABMs), based on knowledge of how individuals respond to their local circumstances. A simple energy budget model was implemented within each earthworm Eisenia fetida in the ABM, based on a priori parameter estimates. From broadly accepted physiological principles, simple algorithms specify how energy acquisition and expenditure drive life cycle processes. Each individual allocates energy between maintenance, growth and/or reproduction under varying conditions of food density, soil temperature and soil moisture. When simulating published experiments, good model fits were obtained to experimental data on individual growth, reproduction and starvation. Using the energy budget model as a platform we developed methods to identify which of the physiological parameters in the energy budget model (rates of ingestion, maintenance, growth or reproduction) are primarily affected by pesticide applications, producing four hypotheses about how toxicity acts. We tested these hypotheses by comparing model outputs with published toxicity data on the effects of copper oxychloride and chlorpyrifos on E. fetida. Both growth and reproduction were directly affected in experiments in which sufficient food was provided, whilst maintenance was targeted under food limitation. Although we only incorporate toxic effects at the individual level we show how ABMs can readily extrapolate to larger scales by providing good model fits to field population data. The ability of the presented model to fit the available field and laboratory data for E. fetida demonstrates the promise of the agent-based approach in ecology, by showing how biological knowledge can be used to make ecological inferences. Further work is required to extend the approach to populations of more ecologically relevant species studied at the field scale. Such a model could help extrapolate from laboratory to field conditions and from one set of field conditions to another or from species to species.

Inadequate taxonomy and highly divergent COI haplotypes in laboratory and field populations of earthworms used in ecotoxicology. A case study

DNA barcoding was used to investigate the phylogenetic delimitations of Eisenia sp. populations used in ecotoxicological research in South Africa. A total of three focal groups (used in published works) and two non-focal groups were assessed. These focal groups, including two laboratory cultures and one field population, have been referred to as Eisenia fetida in the literature. A previous molecular study had already helped to establish that one of the two laboratory groups was a population of E. fetida’s sister species E. andrei. In the present contribution, analyses of the COI gene revealed that the taxonomy of the remaining laboratory and field populations had also been incorrectly assigned since all the generated sequences grouped unequivocally with published sequences of E. andrei. Very high sequence divergence (>25% K2P) found within E. andrei could signal the occurrence of hitherto undescribed cryptic species. These findings are discussed with an emphasis on the possible consequences of using poorly identified earthworms or specimens with high molecular divergence in ecotoxicological bioassays. It is not clear whether unbeknownst to the researchers, the use of cryptic species in bioassays could jeopardise the quality of ecotoxicological investigations. Early evidence suggests that cryptic oligochaete species may respond differently to metal toxicity. The need for comparative ecotoxicological studies between E. andrei and E. fetidais also evidenced, especially in the light of recent numerous reports of cryptic oligochaete species. Ecotoxi-cologists are consequently encouraged, whenever possible, to make use of available genomic technologies to screen their laboratory stocks and available field populations for any molecular distinctiveness.

Earthworm population responses to deciduous forest soil acidity and vegetation cover

This paper shows results of earthworm specimens and biomass investigation in relationship to vegetation cover and soil pH values in sixty plots in broadleaved forests of Gaume region, south Belgium. Standard combination of behavioural and direct methods to catch earthworm specimens were used during the fieldwork – soil and earthworm samples were taken to the lab for pH measurement and species determination. The investigation revealed no significant influence of vegetation cover, but the fact that pH very strongly influenced the density and biomass of earthworms. Variables number of earthworms and earthworm biomass were strongly correlated with each other; therefore only the biomass was used as dependent variable in the statistical tests.Results from this study are useful for updating data of species living in acid forests in Europe and for following studies on forest production and forests soil fertility. soil fauna; biodiversity; acidification; species ecology; abundance; biomass

Slow recovery of earthworm populations after heavy traffic in two forest soils in northern France

To determine the role of earthworms in regenerating compacted zones, it is essential to consider their capacity to colonise these zones. This study aimed to determine the short-term (3–4 years) response of earthworm populations to heavy traffic in two forest soils, at Azerailles (AZ) and Clermont-en-Argonne (CA) in north-eastern France. Earthworm populations were recorded immediately and for 3–4 years after heavy traffic by a 8-wheel drive forwarder with a load of about 23 Mg at AZ and 17 Mg at CA. To test the capacity of earthworms to recolonise traffic plot from the edges, an extra sampling was performed at the border of the traffic plots at AZ. Heavy traffic had a detrimental impact on the density and biomass of three earthworm functional groups. At AZ, earthworm populations, dominated by endogeic species, followed by anecic and epigeic species, had not fully recovered four years after compaction. The absence of statistically significant colonisation by the three functional groups from control to traffic plots indicated that the soil habitat was not yet favourable. At CA, earthworm populations, represented exclusively by epigeic species, had fully recovered three years after compaction, suggesting that the soil habitat was already suitable for them. This strong dependence on soil habitat quality is discussed and may be one reason for variation in the recovery rate of earthworms after compaction reported in the literature. In conclusion, this study did not support the hypothesis that earthworms play a role in regenerating soil structure the first few years following forest-soil compaction.

Factors Affecting Distribution of Earthworms in Kashmir Valley: A Multivariate Statistical Approach

Soil characteristics influence earthworm population dynamics, species distribution and community structure. According in the present study an attempt was made to determine the soil physiochemical factors influencing earthworms of Kashmir valley with a view to improve the soil productivity by enhancing earthworm diversity under different pedoecosystems. Data collection on 15 soil parameters from 20 earthworm inhabiting sites revealed significant variation within and among the sites in soil temperature (F23, 19 = 148.83, 9.71; P < 0.05), moisture (F23, 19 = 16.91, 46.20; P < 0.05), pH (F19 = 47.21; P < 0.05), electrical conductivity (F23, 19 = 11.67, 87.13; P < 0.05), sodium (F23, 19 = 2.46, 211.25; P < 0.05), potassium (F19 = 22.91; P < 0.05), calcium (F19 = 15.90; P < 0.05), magnesium (F23, 19 = 1.76, 104.51; P < 0.05), organic carbon (F23, 19 = 64.60, 222.50; P < 0.05), organic nitrogen (F23, 19 = 4.59, 3.81; P < 0.05) and phosphorous (F23, 19 = 5.11, 137.87; P < 0.05). Aporrectodea caliginosa trapezoides and A. rosea rosea exhibited wide range of distribution whereas Octolasion cyaneum, A. c. trapezoides and A. parva showed restricted distribution. Hierarchical cluster analysis grouped 20 earthworm collection sites into three clusters—earthworm absent sites, low earthworm diversity sites and moderate earthworm diversity sites. Principal component analysis assisted from the data set of 20 sites, resulting into four latent factors accounting for 77.95 % of total variance, identified the factors affecting earthworm communities are mainly related to physical habitat factor, chemical factor, soil texture factor and growth factor, each accounting for 26.41, 20.16, 18.25 and 13.13 % of total variance respectively.