Diversity Of Earthworm Communities Research Articles

Structure and diversity of earthworm communities in long-term irrigated soils with raw effluent and treated wastewater

Abstract This study was conducted in two natural meadows: first, soils were irrigated with raw wastewater (SIRWW) and in the second, soils were irrigated with treated wastewater (SITWW). Earthworms were sampled in eight soil blocks spaced 10 m apart at each site. Earthworm community was characterized and compared using density, biomass, composition, structure, species richness, and diversity parameters. At both meadows, 459 earthworm individuals from two families and seven species were collected. The highest earthworm density and species richness were recorded at SIRWW. Nicodrilus caligenus was the most abundant species. Most of earthworm community parameters decreased significantly at SITWW. Only two species (N. caligenus and Octodrilus complanatus) were common between the two grasslands. Among the seven species identified at both meadows, four (Allolobophora longa, Eisenia foetida, Allolobophora rosea, Allolobophora chlorotica) were exclusively present in SIRWW, whereas a single species (Amynthas sp.) was characterized in SITWW. Three ecological earthworm groups (epigeic, endogeic, and anectic) were represented in SIRWW, with the dominance of endogeics. Further studies are needed to quantify pollution in this soils and the accumulation of pollutant load in earthworms. It is also important to highlight the relationship between the abundance and diversity of earthworms in these two ecosystems with soil biological activity.

Urban land-use impacts on composition and spatiotemporal variations in abundance and biomass of earthworm community

Soil fauna can sensitively respond to alterations in soil environment induced by land-use changes. However, little is known about the impact of urban land-use changes on earthworm communities. In this study, three land-use types (i.e., forest, nursery and abandoned lands) were chosen to identify differences in diversity, abundance and biomass of earthworm community in Kunming City. Urban land-use had a pronounced difference in species composition, evenness and diversity of earthworm communities. Forest land had the highest density, biomass and diversity of the earthworm communities. Total abundance was dominated by endogeic species in nursery land (70%) and abandoned land (80%), whereas in the forest land, the earthworm community comprised epigeic, endogeic and anecic species. Temporal changes in earthworm density and biomass were also significantly affected by land-use change. Total density and biomass of earthworms in the forest and nursery lands were highest in September, but highest in the abandoned land in October. The influence of soil physicochemical properties on the earthworm density and biomass also varied with land-use types. Soil temperature significantly affected earthworm density and biomass in the three land-use types. Soil pH was positively correlated with earthworm biomass in the forest land, but negatively associated with earthworm density in the abandoned land. Soil organic matter was positively correlated only with density and biomass of earthworms in the nursery and abandoned lands. Our results suggest that the species composition, abundance and biomass of earthworm communities can be determined by the modification of soil properties associated with urban land-use type.

Exotic earthworms dispersion through protected forest areas and their potential impacts on nitrous oxide production

It is generally accepted that human activities are responsible for the dispersal of exotic earthworms in northeastern North America. We know little, however, about the relative effects of concurrent human activities on the structure of these earthworm communities in protected forest areas, nor on their impacts on soil biological activities. Our first objective was to infer the relative importance of recreational fishing and road traffic on the structure of Lumbricidae communities in Mont-Tremblant National Park, the oldest conservation area in the province of Quebec, Canada. Our second objective was to test the relationship between earthworm species abundances and soil properties related to microbial and nitrogen dynamics. We sampled earthworm communities around 61 lakes, which included 23 heavily-fished lakes and 20 non-fished lakes located near roads, as well as 18 non-fished lakes located in remote areas of the park. Our results revealed that fishing and proximity to roads both have a positive effect on the abundance of earthworms, as does the soil pH. Fishing activities had a greater effect than road proximity on the abundance and diversity of earthworm communities, notably on the abundance of the anecic species Lumbricus terrestris. To assess at a finer scale the effects of earthworm community structure on soil microbial and nitrogen dynamics, we collected and analyzed soils from 47 sampling points around two lakes with high earthworm densities. Exploratory redundancy analysis found a negative correlation between epigeic and anecic earthworm species, with the former correlating positively to microbial biomass and the latter correlating positively to nitrification and denitrification. Confirmatory path analysis established a positive indirect effect of Lumbricus terrestris, the preferred fishing bait, on potential soil nitrous oxide emissions. We conclude that the human-mediated dispersion of earthworms in the most pristine ecosystems of Quebec affects ecosystem functioning and thus requires a review of current policies regarding the use of live-bait by fishermen.

DNA barcoding reveals diversity patterns of earthworm communities in remote tropical forests of French Guiana

Despite representing a key component of terrestrial biota, soil invertebrates in tropical rainforests have been poorly studied from both a taxonomic and an ecological perspective when compared to other groups of terrestrial animals. We sampled earthworm communities in a range of sampling locations in two different study sites of the Nouragues Natural Reserve in French Guiana, focusing on lowland to plateau and hilltop forests as well as on savannah-like vegetation of the Nouragues granitic inselberg. We used the barcode region of the COI gene to delimit Molecular Taxonomic Units (MOTUs), further validated using species-level diagnostic morphological characters. A total of 651 sequences was obtained, most of them corresponding to juveniles that cannot be identified to the species level from morphology alone. We found a total of 48 MOTUs, and both rarefaction curves and diversity estimators (Chao1 and ACE) suggested that 60 species could occur in the study area, representing the highest earthworm richness ever recorded worldwide. Beta-diversity analyses highlighted a strong species turnover between sampling locations. Except in a few specific cases, species richness was usually limited to 12 species at the scale of a given location, which likely indicates the influence of competitive interactions during community assembly process. Community structure was dominated by species living in the upper soil layers and in surface microhabitats, with some of them able to colonize epiphytic soils up to more than 40 m above ground level. These results suggest the importance of long-term diversification processes and current ecological factors for the structuring and the diversity of earthworm communities in tropical rainforests of French Guiana.

Broad and local-scale patterns of exotic earthworm functional groups in forests of National Wildlife Refuges of the Upper Midwest, USA

The National Wildlife Refuge System is the world’s largest network of lands set aside specifically for wildlife conservation. For refuge planners and managers tasked with maintaining ecological integrity and wildlife habitat, many uncertainties exist. In forests in the Upper Midwest, for instance, exotic earthworms are impacting ecosystem structure and function, but their community composition and effects on refuges is unknown. We examined the association of earthworm functional group abundance and community composition within upland forests of refuges with broad scale patterns of anthropogenic land use and local scale differences in forest characteristics. Patterns of anthropogenic land cover, including proportion of the land, mean patch area, and largest patch index, were strongly correlated with the biomass of epi-endogeic earthworms. Earthworm community diversity, however, was inversely related to patterns of dominating anthropogenic land cover, and increased under high ratios of natural to anthropogenic lands in the surrounding ecoregion. Within forests, earthworm community composition could be partially explained by variables representing both dispersal opportunities and habitat suitability. In general, heavily-invaded forests had low conifer dominance, high silt content, high basal area, greater amounts of anthropogenic cover within 500 m, and were closer to roads and farther from agriculture. However, the relationship between local forest characteristics and biomass differed greatly among earthworm functional groups and between refuges dominated by natural lands and those dominated by anthropogenic lands. For refuges with high earthworm loads and well developed earthworm communities, managers may be confounded in restoring historic conditions and may need to look at multiple tools, including artificial regeneration, to mitigate for current earthworm effects. In refuges seemingly in earlier stages of earthworm invasion, future planning and management should be tempered by potential effects observed in those refuges in more anthropogenic landscapes.

New earthworm records for Macaronesia with observations on the species, ecological characteristics and colonization history

Abstract Field surveys have provided new earthworm records for Madeira and Porto Santo, subtropical islands part of central-eastern, oceanic Macaronesia, belonging to three families: Acanthodrilidae, Lumbricidae and Megascolecidae; although we found no evidence of endemic or native species. The first records from Macaronesia of Dendrobaena pseudohortensis , Dendrodrilus rubidus tenuis and Octolasion cyaneum are included, increasing their known distribution. Eight peregrine species are cited for Porto Santo (no previous records) and eight for Madeira, mostly of Palaearctic origin; their introduction is presumed not to have occurred before humans arrived on the islands. The number of introduction events emerges as the most consistent predictor of the establishment of invasive species. The new data presented contribute to a better understanding of the earthworm colonization and the primary factors that determine the present distribution patterns of species are discussed. Human activity appears to be a strong influence on the distribution of the newly recorded species throughout the study area. We also make some ecological observations: soil pH and organic matter as variables influence the spatial ordination of some earthworm species. Affinities are evident with the Canary Island fauna and to a lesser extent with that of continental areas west of the Strait of Gibraltar and within the Mediterranean basin. The diversity of earthworm communities is linked with the arrival of European colonists and agro-commercial activities, which began almost six centuries ago. It is anticipated that the number of earthworm species will continue to increase, since introductions from other parts of the world are highly probable.

Effects of bioenergy crop cultivation on earthworm communities—A comparative study of perennial ( Miscanthus) and annual crops with consideration of graded land-use intensity

Energy crops are of growing importance in agriculture worldwide. This field study aimed to investigate earthworm communities of different intensively cultivated soils during a 2-year period, with special emphasis on annual and perennial energy crops like rapeseed, maize, and Miscanthus. These were compared with cereals, grassland, and fallow sites. Distribution patterns of earthworm abundance, species, and ecological categories were analysed by constrained ordination procedures (redundancy analysis; CANOCO) using a set of environmental variables as predictors, such as CN value of harvest residues, SOC and N t content, soil pH, soil texture, and land-use intensity. The latter was determined by principal component analysis using average soil coverage and intensity of tillage, weed control, and fertilisation as input variables. It was clearly found that land-use intensity was the dominant regressor for earthworm abundance and total number of species. The diversity of earthworm communities was especially enhanced and showed a more balanced species composition in extensively managed soils under grassland, fallow, and Miscanthus. For the total number of species, Miscanthus (5.1 ± 0.9) took a medium position and neither differed significantly from intensively managed rapeseed (4.0 ± 0.9), cereals (3.7 ± 1.1), and maize sites (3.0 ± 1.4), nor from grassland (6.8 ± 1.5) and fallow (6.4 ± 1.0) sites. Total earthworm abundance ranged between 355 (±132) and 62 (±49) individuals m −2 in fallow and maize sites, respectively. Interestingly, Miscanthus had quite positive effects on earthworm communities although the CN value of harvest residues was very high. It is recommended that Miscanthus may facilitate a diverse earthworm community even in intensive agricultural landscapes.

Hierarchical Responses of Soil Invertebrates (Earthworms) to Toxic Metal Stress

The concept of a hierarchical cascade of biological responses to stress occurring across different levels of biological organization is an underlying principle of both theoretical and regulatory ecology/ecotoxicology. This study investigates the reality of this cascade for earthworms exposed to toxic metal stress. Gene expression was the most sensitive endpoint (EC50 = 616 microg Zn g(-1)) followed by the integrity of coelomocyte lysosomal membrane (EC50 = 645 microg Zn g(-1)). This confirms that, in accordance with the cascade concept, suborganism level endpoints respond at lower metal concentrations than higher organization endpoints. The relative sensitivity of the higher organization parameters was not as predicted by the cascade. Organic material removal was more sensitive (EC50 = 997 microg Zn g(-1)) than L. rubellus reproduction (EC50 = 3236 microg Zn g(-1)), L. rubellus population size (EC50 = 5000-11500 microg Zn g(-1)), and earthworm community diversity (EC50 = 1737 microg Zn g(-1)). This can be attributed to (1) the relative insensitivity of L. rubellus to metals and (2) general toxic effects of metals on the earthworm energy budget (and thus feeding). On the basis of these results, it can be concluded that predictive assessments of the consequences of environmental stressors needs to include approaches that respect the relative sensitivities of different taxa, while retrospective appraisals should exploit the sensitivity of low organization level responses.

Influence of agricultural land use on the size and composition of earthworm communities in northern KwaZulu-Natal, South Africa

The effects of land management including undisturbed native forest, native grassland, sugarcane ( Saccharum spp.) (preharvest burnt or green cane harvested), exotic forest (gum, Eucalyptus grandis; pine, Pinus elliottii; wattle, Acacia mearnsii), orchard crops (orange, Citrus sinensis; banana, Musa accumunata; avocado, Persea americana) and grazed kikuyu grass ( Pennisetum clandestinum) on the size and composition of earthworm communities and on related soil properties (organic C, soluble C, microbial biomass C) were investigated. The study locality was in the tropical, northern part of KwaZulu-Natal. Earthworm numbers followed the order: kikuyu pasture > native forest > banana> orange> wattle= pine= gum= green cane harvested sugarcane ≥ native grassland = avocado≥ burnt sugarcane . Earthworm numbers and biomass were closely positively correlated with soluble C, microbial biomass C and also pH. A total of 11 species of earthworms were collected. Over 80% of individuals collected were accidentally introduced exotic species which originated from India, South America and West Africa. Most land use types supported five to seven species but sugarcane and wattle supported only two or three species. Juveniles dominated the community under all land uses except kikuyu pasture and avocado. Epigeic species dominated under native forest and native grassland, avocado and gum. For the other types of land use, endogeics predominated. The most numerous species present was Pontoscolex corethrurus which was present under all land uses. The most common epigeic species was Amynthus rodericensis which made up a substantial portion of the community under native and gum forests and banana. The third most numerous species was A. minimus which is a polyhumic, endogeic species and was particularly numerous under kikuyu pasture. Dichogaster saliens was an important component of the community under some land uses. It was concluded that land use has major effects on the size, composition and diversity of earthworm communities in the region.

Effect of agricultural land use on soil organic matter status and the composition of earthworm communities in KwaZulu-Natal, South Africa

Little is known regarding the effects of land use on soil organic matter status and earthworm communities in South African soils. For that reason the effects of the main agricultural land uses in the midlands region of KwaZulu-Natal (maize ( Zea mays), sugarcane ( Saccharum spp.), annual ryegrass ( Lolium multiflorum), permanent kikuyu pasture ( Pennisetum clandestinum), gum ( Eucalyptus grandis) and pine forest ( Pinus patula)) on soil organic matter content, microbial biomass C and the size and composition of the earthworm community was investigated on two sites where the long-term history of land management was known. In comparison with, undisturbed, native grassland, permanent kikuyu pasture resulted in an increase in organic C, K 2SO 4-extractable C, microbial biomass C and the microbial quotient. Maize and sugar production under conventional tillage (CT) resulted in a decrease in organic matter and microbial biomass. Under gum and pine forests the organic C content was similar to that of under native grassland but the microbial biomass and microbial quotient tended to be higher. Exotic earthworms dominated under agricultural management making up to 98 and 100% of the communities at sites 1 and 2, respectively. They belonged to the families Lumbricidae, Acanthrodilidae and Megascolicidae. They were accidentally introduced from Europe, India and West Africa, respectively, and now coexist in the sub-humid warm climate of the region. Earthworm numbers (230–310 m −2) and biomass, the number of species present, and the number present as adults were all greatest under kikuyu pastures and numbers were low (<60 m −2) under maize (CT) and sugarcane. Numbers were 3.5-fold higher for maize under zero than CT. In relation to the comparatively large organic C and microbial biomass C values under exotic forests, earthworm numbers were notably low (25–60 m −2). This was attributed to the low palatability of pine and gum litter. It was concluded that land use has substantial effects on soil organic matter content and on the size, composition and diversity of earthworm communities in South African soils.