Enchytraeid and earthworm communities along a pollution gradient near Olkusz (southern Poland)

The effect of heavy metal pollution on Oligochaeta (Enchytraeidae and Lumbricidae) populations was studied along a pollution gradient in vicinity of Olkusz (southern Poland). The study sites, which differed in metal concentrations in the humus layer, were established in mixed-pine forests 3.5 km, 2.5 km, 3.9 km, 7.9 km and 31.9 km (reference site) from the source of pollution (zinc smelter). Enchytraeid and earthworm population density and species composition were determined from soil sampled four times from the study sites. Enchytraeidae populations consisted of nine genera and 18 species. The dominating enchytraeid species in all study sites was Cognettia sphagnetorum (approx. 90%), except for the most polluted site, where Enchytraeus, Fridericia and Henlea were the most common species diversity and heterogeneity were the highest in the most polluted site. The highest mean densities were found in the reference site (16,333 individuals m^?2) and lowest in the most polluted site (3932 individuals m^?2). Earthworm populations consisted of three epigeic species, and the most abundant one was Dendrobaena octaedra. Earthworms densities in all sites sampled were low. The concentrations of Zn, Pb and Cd in: humus layer, and in enchytraeids and earthworms, were the highest for the most polluted site and decreased with distance from pollution source. Density of Enchytraeidae and body loads of metals in Enchytraeidae and Lumbricidae can be employed for biomonitoring.     

A multi-scale study of soil macrofauna biodiversity in Amazonian pastures

The influence of three spatially hierarchical factors upon soil macrofauna biodiversity was studied in four pasture plots in eastern Amazonia. The first factor was the local depth of the soil. The second factor was the ground cover type on the soil samples (bare ground, grass tufts, dead trees lying on the ground). The third factor was the dimensions of the grass tufts sampled (size and shape). The effect of each factor upon the morphospecies richness and density of total soil macrofauna was analysed. Detailed results are given for earthworms, termites, ants, beetles and spiders. All factors significantly affected the morphospecies richness and/or density of the soil macrofauna. The type of ground cover had the strongest influence, affecting the total richness and density of the soil macrofauna and of almost all the groups represented. The soil depth affected only the density of the termites and the global morphospecies richness. Interactions between soil depth and ground cover type affected the total macrofauna morphospecies richness and the density of the earthworms. The dimensions of the grass tuft influenced the global morphospecies richness, the morphospecies richness of the ants and the density of the spiders.     

Spatial patterns of grasses influence soil macrofauna biodiversity in Amazonian pastures

Grasslands are often characterized by small-scale spatial heterogeneity due to the juxtaposition of grass tufts and bare ground. Although the mechanisms generating plant spatial patterns have been widely studied, few studies concentrated on the consequences of these patterns on belowground macrofauna. Our objective was to analyze the impact of grass tuft (Brachiaria bryzantha cv. marandu) spatial distribution on soil macrofauna diversity in Amazonian pastures, at a small scale (less than 9 m²). Soil macrofauna was sampled among B. bryzantha tufts, which showed a variable spatial distribution ranging from dense to loose vegetation cover. The vegetation configuration explained 69% of the variation in total soil macrofauna density and 68% of the variation in total species richness. Soil macrofauna was mainly found in the upper 10 cm of soil and biodiversity decreased with increasing distances to the nearest grass tuft and increased with increasing vegetation cover. The size of the largest grass tuft and the micro-landscape connectivity also had a significant effect on biodiversity. The density and species richness of the three principal soil ecological engineers (earthworms, ants and termites) showed the best correlations with vegetation configuration. In addition, soil temperature significantly decreased near the plants, while soil water content was not influenced by the grass tufts. We conclude that soil macrofauna diversity is low in pastures except close to the grass tufts, which can thus be considered as biodiversity hotspots. The spatial arrangement of B. bryzantha tussocks influences soil macrofauna biodiversity by modifying soil properties in their vicinity. The possible mechanisms by which these plants could affect soil macrofauna are discussed.     

Mixed-species legume fallows affect faunal abundance and richness and N cycling compared to single species in maize-fallow rotations

Rotation of nitrogen-fixing woody legumes with maize has been widely promoted to reduce the loss of soil organic matter and decline in soil biological fertility in maize cropping systems in Africa. The objective of this study was to determine the effect of maize-fallow rotations with pure stands, two-species legume mixtures and mixed vegetation fallows on the richness and abundance of soil macrofauna and mineral nitrogen (N) dynamics. Pure stands of sesbania (Sesbania sesban), pigeon pea (Cajanus cajan), tephrosia (Tephrosia vogelii), 1:1 mixtures of sesbania + pigeon pea and sesbania + tephrosia, and a mixed vegetation fallow were compared with a continuously cropped monoculture maize receiving the recommended fertilizer rate, which was used as the control. The legume mixtures did not differ from the respective pure stands in leaf, litter and recycled biomass, soil Ca, Mg and K. Sesbania + pigeon pea mixtures consistently increased richness in soil macrofauna, and abundance of earthworms and millipedes compared with the maize monoculture (control). The nitrate-N, ammonium-N and total mineral N concentration of the till layer soil (upper 20 cm) of pure stands and mixed-species legume plots were comparable with the control plots. Sesbania + pigeon pea mixtures also gave higher maize grain yield compared with the pure stands of legume species and mixed vegetation fallows. It is concluded that maize-legume rotations increase soil macrofaunal richness and abundance compared with continuously cropped maize, and that further research is needed to better understand the interaction effect of macrofauna and mixtures of organic resources from legumes on soil microbial communities and nutrient fluxes in such agro-ecosystems.     

Effects of heavy metals on the structure and functioning of detritivore communities in a contaminated floodplain area

The aim of this study was to determine the effects of heavy metal pollution on the structure and functioning of detritivore soil communities that consist of isopods, millipedes and earthworms, in 15 heavily polluted flood plain soils, located in the delta area of the rivers Rhine and Meuse, in the Netherlands. The 15 study sites represent a gradient in Zn, Cu and Cd concentrations. The structural attributes of the detritivore community, which were assessed, were the species richness and densities in the field sites. The functioning of the detritivore community was studied by determining organic matter decomposition using litter bags and feeding activity with the bait-lamina method. Concentrations of Cd, Cu and Zn were measured in soil, pore water and 0.01 M CaCl₂ extracts of the soil, in adult earthworms and plant leaves. Results show that metal pollution is not a dominating factor determining the species richness and densities of the selected detritivore groups, although the biomass of the earthworm Lumbricus rubellus was positively and significantly correlated to Zn concentrations in pore water and 0.01 M CaCl₂ extracts. Litter decomposition was significantly and positively correlated to detritivore biomass and 0.01 M CaCl₂ extractable Cd concentrations in soil and negatively to pH-CaCl₂, although the range of pH values was very small. It can be concluded that in spite of high metal levels in the soil, bioavailable concentrations are too low to result in clear negative effects on the structure and functioning of detritivores in the Biesbosch, the Netherlands.     

Earthworm colonisation of abandoned arable soil polluted by copper

The distribution, density and biomass of earthworms were investigated at the copper polluted site, Hygum (Denmark). In 1994, shortly after farming of the area was abandoned, only four earthworm species were present and their distribution was restricted to areas where copper concentration did not exceed 200 mg kg^?1 dry soil. Sixteen years later (in 2010), without any agricultural activity, ten species of earthworms were found, in particular, epigeic species were present where soil copper concentrations reached >1000 mg kg^?1 dry soil.     

The effects of reduced-impact logging practices on soil animal communities in the Deramakot Forest Reserve in Borneo

The effectiveness of reduced-impact logging practices on the maintenance of biodiversity in Borneo has been recognized for some organisms (e.g., mammals). We investigated the effects of reduced-impact logging and conventional selective logging practices on biodiversity by using soil fauna as indicators of disturbance. The study sites were the production forests of the Deramakot Forest Reserve and the Tangkulap Forest Reserve in Sabah, Malaysian Borneo (5°14–30′ N, 117°11–36′ E). We compared macro- and mesofauna in a pristine forest with no logging, a reduced-impact logged forest in Deramakot Forest Reserve, and a conventionally logged forest in Tangkulap Forest Reserve.The mean density of soil macrofauna (excluding ants) did not differ significantly among the three forest categories (nested ANOVA, p > 0.05). This tendency was also seen in the density and species richness of Oribatida and Collembola, which showed little difference among forest categories. Nonmetrical multidimensional scaling (NMS) ordination diagrams revealed a different community composition in conventionally logged forest sites compared with the other sites. The scores for the NMS first or second axis of soil fauna were correlated with one or more of the values for density, diversity, and species composition of trees. A RELATE test showed the congruence between trees and the Collembola and Oribatida community composition between sites. The results implied that the soil fauna community composition was related to tree communities. In conclusion, the impacts of logging on decomposers in the soil animal communities have been mitigated by the introduction of reduced-impact logging in Deramakot Forest Reserve through the protection of tree vegetation. It is important to consider monitoring the influence of selective logging on soil fauna with regard to the dynamics of the species (or group) composition because total density and species (or group) richness of soil fauna displayed only a marginal response to the different logging practices.     

The effect of some air pollutants on the vertical distribution of mites (Acari) in soils of young Scots pine forests in Poland

The effect of heavy metals and nitrogen air pollution on the vertical distribution of mites in soils in about 20 year old Scots pine forests was investigated. A high concentration of heavy metals greatly reduced the density and species richness of mites, especially in the Of/h and AEes horizons, whereas a low concentration increased the density in all soil horizons, compared with the control plots. A high concentration of nitrogen pollution reduced slightly the density of mites in all soil horizons, while lower concentrations increased their density: a medium concentration in the Ol and Of/h horizons, and a low concentration in the Ol horizon.     

Schwermetallbelastung von Aporrectodea caliginosa (Oligochaeta,Lumbricidae) im Raum Kiel

Heavy metal content in Aporrectodea caliginosa (Oligochaeta, Lumbricidae) in the city of Kiel (Germany, Schleswig-Holstein) In November 1995 the content of lead, cadmium, copper and zinc in earthworms of the Aporrectodea caliginosa species was investigated at 28 sites of the Kiel area, as well as at one reference site (Belauer See, ca. 20 kilometres south of Kiel), and compared with the heavy metal content in the soil taken from all those sites. As for the lead and copper content, a positive correlation could be established between the earthworms and the soil. However, the lead content in the earthworms did not depend only on its amount in the soil, but also on soil pH and calcium content. Their copper content decreased exponentially as weight increased. The content of lead, cadmium and copper in A. caliginosa suggested an influence of urban soil pollution on the heavy metal content in earthworms. According to the grouping of heavy metal content in the earthworms, which was done in the course of the research work, the city of Kiel ranges among a minor to a medium degree of pollution caused by the investigated heavy metals.     

Species abundance distribution of collembolan communities in forest soils polluted with heavy metals

The species frequency of collembolan communities along a gradient of heavy metal pollution in soil of pine forest soils was studied. Sampling plots were established in forests 1, 3, 5, 8, 11, 68 and 148 km from the Miasteczko Śląskie zinc smelter. At each plot the plant associations, physicochemical characteristics of soil, and collembolan species composition and abundance were examined. The structure of collembolan communities was analyzed with regard to species distribution, testing geometric series, broken-stick, logarithmic series, log-normal and negative binomial distribution models. Most of the collembolan communities occurring both in contaminated and in uncontaminated soils had structure similar to a negative binomial distribution. In the samples from the oldest forest, the species frequencies could also be fitted to a log-normal distribution. The species frequency model was independent of the degree of soil pollution. Under the assumption of a negative binomial distribution of Collembola from soil samples, it is possible to estimate the theoretical number of collembolan species in the habitats studied. The difference between estimated and empirical numbers of species (the number of species not revealed in samples) was linearly correlated with metal concentrations in soil, indicating the elimination of a number of rare species from severely polluted forests.     

The effect of two endogeic earthworm species on zinc distribution and availability in artificial soil columns

The objective of this study was to determine the impact of earthworm bioturbation on the distribution and availability of zinc in the soil profile.Experiments were carried out with Allolobophora chlorotica and Aporrectodea caliginosa in 24 perspex columns (∅ 10 cm), filled with 20-23 cm non-polluted soil (OM 2%, clay 2.9%, pH 0.01 M CaCl₂ 6.4), that was covered by a 3-5 cm layer of aged zinc spiked soil (500 mg Zn/kg dry soil) and another 2 cm non-polluted soil on top. After 80 and 175 days, columns were sacrificed and each cm from the top down to a depth of 15 cm was sampled. Earthworm casts, placed on top of the soil, were collected. Each sample was analyzed for total and CaCl₂-exchangeable zinc concentrations.Effects of earthworm bioturbation were most pronounced after 175 days. For A. chlorotica, total and CaCl₂-exchangeable zinc concentrations in the polluted layers were lower with than without earthworms. Total zinc concentrations in the non-polluted layers were higher in columns with earthworms. Casts of A. chlorotica collected on the soil surface showed slightly higher total zinc concentrations than non-polluted soil. Casts were found throughout the whole column. For A. caliginosa there were no differences in total zinc concentration between columns with and without earthworms. CaCl₂-exchangeable zinc concentrations in the polluted layers were lower for columns with earthworms. Casts were mainly placed on top of the soil and contained total zinc concentrations intermediate between those in non-polluted and polluted soil layers.This study shows that different endogeic earthworm species have different effects on zinc distribution and availability in soils. A. chlorotica transfers soil throughout the whole column, effectively mixing it, while A. caliginosa decreases metal availability and transfers polluted soil to the soil surface.     

Seasonal and land-use induced variations of soil macrofauna composition in the Western Ghats, southern India

Soil macrofauna was surveyed in six sites characterised by different vegetation types on five occasions in the Western Ghats, India. Sampling sites included a primary forest, a weakly disturbed forest (slightly logged in the past), a highly disturbed forest (intensively logged), an Acacia auriculiformis plantation (8 years old), a pasture with high density of Phoenix humilis and a pasture without P. humilis. We showed that both land management and temporal variability induced significant changes in the soil macrofauna. Forest sites hosted larger densities of soil macroorganisms. The effect of seasons was apparent as some clear modifications in the fauna composition occurred. Some groups like earthworms mainly exhibited temporal variability whereas others like millipedes were chiefly affected by land management options. The seasonal rhythms of soil macrofauna were poorly expressed in the pasture plots and the Acacia plantation, but were particularly clear in the forest sites. This interaction between land management and temporal patterns may be explained by some changes in the species composition associated with certain land-uses. Our approach was based on a between-within classes PCA that proved particularly useful by providing statistical tests and a hierarchy of land management and temporal rhythm effects.     

Genetic and ecological impacts of heavy metal and flooding stress on the earthworm Lumbricus rubellus in floodplains of the Rhine river

In the highly polluted river Rhine system, earthworms face environmental stress resulting from flooding and elevated heavy metal concentrations in the floodplain soil. Previous field studies have revealed adaptation to flooding for the earthworm species Lumbricus rubellus as this species matures at a lower weight in floodplain sites with a high frequency of flooding compared to less frequently flooded sites. Also heavy metals have effects on L. rubellus and heavy metals are influencing the genetic composition of this species. In this study, it was tested whether flooding and heavy metals had an impact on the genetic composition of L. rubellus living in floodplains along the river Rhine system. Earthworms were sampled at three sites previously studied along the river to assess earthworm diversity, biomass, density, and individual weight, and developmental status of L. rubellus. The genetic variation by means of isozymes was studied for 175 individuals. The results showed lowest density of L. rubellus adult and sub-adult life-stages and lowest individual weight of these life-stages at the frequent inundated site. The genetic composition, however, showed no effects of flooding on the genetic composition, but effects of heavy metals could not be ruled out.     

Effects of heavy metals on the litter consumption by the earthworm Lumbricus rubellus in field soils

Aim of this study was to determine effects of heavy metals on litter consumption by the earthworm Lumbricus rubellus in National Park the “Brabantsche Biesbosch”, the Netherlands. Adult L. rubellus were collected from 12 polluted and from one unpolluted field site. Earthworms collected at the unpolluted site were kept in their native soil and in soil from each of the 12 Biesbosch sites. Earthworms collected in the Biesbosch were kept in their native soils. Non-polluted poplar (Populus sp.) litter was offered as a food source and litter consumption and earthworm biomass were determined after 54 days. Cd, Cu and Zn concentrations were determined in soil, pore water and 0.01 M CaCl₂ extracts of the soil and in earthworms. In spite of low available metal concentrations in the polluted soils, Cd, Cu and Zn concentrations in L. rubellus were increased. The litter consumption rate per biomass was positively related to internal Cd and Zn concentrations of earthworms collected from the Biesbosch and kept in native soil. A possible explanation is an increased demand for energy, needed for the regulation and detoxification of heavy metals. Litter consumption per biomass of earthworms from the reference site and kept in the polluted Biesbosch soils, was not related to any of the determined soil characteristics and metal concentrations.     

Heavy metal levels in earthworms of a forest ecosystem influenced by traffic and air pollution

Soils of a forest ecosystem in Berlin (West) are highly polluted by Pb and less polluted by Cd and Cu. Pb levels in earthworm species depend primarily on soil type and only secondarily on the distance from a highway crossing the forest. The dominating species Lumbricus rubellus and Dendrobaena octaedra show different body burdens especially of Cd. Liming the forest soils decreases the Pb concentrations significantly. Only in D. octaedra has body weight been found to be related to Pb; Pb has been increased from 50 mg kg^–1 in small to 250 mg kg^–1 in large specimens; Cu has been regulated at a more or less constant absolute level (about 0.4 pg per specimen). This species obviously regulates or accumulates the three metals in different ways. Centipedes as predators of earthworms in the sites show markedly less pollution of Pb and Cd (about 2.5 and 0.6 mg kg^–1) than the worms, but higher concentrations of the essential Cu (about 40 mg kg^–1). The use of earthworms as indicators of heavy metal pollution should take into account the biology of the various species, the soil type, the type and amount of organic matter as well as chemical parameters such as pH value or basic anions.     

Effects of metal pollution on soil macroinvertebrate burrow systems

A reduction in the numbers of macroinvertebrates present in soil may have a negative effect on soil structure, infiltration rates, and gas exchanges. Soil pollution by metal is known to have a detrimental effect on soil macrofauna. The aim of the present study was to evaluate (1) direct and indirect effects of soil pollution on soil macroinvertebrate bioturbation and (2) effects of the two macroinvertebrate communities found in a polluted and a nonpolluted area (one supposed sensitive, the other tolerant to metals) on burrow systems parameters. Macroinvertebrate porosity was studied using X-ray tomography. Three-dimensional reconstructions and characterisation of the burrow system were obtained using image analysis. Results showed that metal pollution principally affected the spatial distribution of macropores (more macropores were found near the soil surface) and the shape of the burrow system (branching rate was higher in the polluted soil), whereas soil macroinvertebrate composition principally affects burrow density parameters (the number of burrows was higher for the sensitive macroinvertebrate community).     

Evaluating the efficiency of sampling methods in assessing soil macrofauna communities in arable systems

The soil fauna is often a neglected group in many large-scale studies of farmland biodiversity due to difficulties in extracting organisms efficiently from the soil. This study assesses the relative efficiency of the simple and cheap sampling method of handsorting against Berlese–Tullgren funnel and Winkler apparatus extraction. Soil cores were taken from grassy arable field margins and wheat fields in Cambridgeshire, UK, and the efficiencies of the three methods in assessing the abundances and species densities of soil macroinvertebrates were compared. Handsorting in most cases was as efficient at extracting the majority of the soil macrofauna as the Berlese–Tullgren funnel and Winkler bag methods, although it underestimated the species densities of the woodlice and adult beetles. There were no obvious biases among the three methods for the particular vegetation types sampled and no significant differences in the size distributions of the earthworms and beetles. Proportionally fewer damaged earthworms were recorded in larger (25 × 25 cm) soil cores when compared with smaller ones (15 × 15 cm). Handsorting has many benefits, including targeted extraction, minimum disturbance to the habitat and shorter sampling periods and may be the most appropriate method for studies of farmland biodiversity when a high number of soil cores need to be sampled.     

Earthworms in Chromolaena odorata (L.) King and Robinson (Asteraceae) fallows along a chronosequence: Changes in community structure and identification of persistent and indicator species

The species Chromolaena odorata (Asteraceae) is a notorious invasive shrub spreading throughout West and Central Africa and as such, there is a need to determine its environmental impact, particularly on soil biodiversity and functioning. Indeed, soil organisms such as earthworms are known to strongly influence soil properties and biogeochemical cycles. This study, conducted in Central Côte d’Ivoire, aims to investigate the temporal dynamics of earthworm communities in C. odorata fallows of different ages and to identify associated indicators and persistent species. Three distinct classes of fallows identified by local farmers, were considered: young (1–3 years, C1), medium-aged (4–8 years, C2) and old (>9 years, C3). Each of the classes included four plot replicates where earthworms were sampled using the Tropical Soil Biology and Fertility (TSBF) 25 cm × 25 cm × 30 cm soil monolith method. The study of earthworm communities was focused on density, biomass, diversity and complementarity. Indicator values (IndVals) were used to identify indicator species of the classes of fallows. The shrub exerted a mixed influence on earthworms depending on the functional group, with litter feeders and polyhumics declining over time as a result of a reduction of the litter availability on the soil surface. The species richness was significantly greater in C1 than in the other classes although the Shannon–Weaver's index did not vary significantly. However, a cluster analysis performed on densities highlighted marked differences between C2 and the two other classes in terms of community composition. Indicator species were found for C1 and C2. The geophagous Millsonia omodeoi has emerged as a persistent species as its density and biomass steadily increased so that it became the dominant species in old fallows. The roles of litters and soil parameters in influencing earthworm communities are discussed.     

Compacted soil affects soil macrofauna populations in a semi-arid environment in central Queensland

Population densities of soil macrofauna were assessed in a field experiment with annually compacted treatments (applied to whole plots) and management treatments to repair initially compacted soil. Earthworms accounted for about half the macrofauna recovered during the experiment. Compaction of wet surface soil (water content>plastic limit) by agricultural machinery generally reduced numbers of macrofauna and earthworms. Annual compaction with a 10 Mg axle load on wet soil reduced mean macrofauna numbers from 70 to 15 m⁻² and mean earthworm numbers from 41 to 2 m⁻². Annual compaction with 6 Mg on soil drier than the plastic limit to a depth of 0.08 m had no adverse effect on the soil macrofauna. A 3-year pasture ley had more macrofauna (211 m⁻²) than a control treatment under cropping (29 m⁻²) but numbers declined when cropping was resumed.