Earthworm Assemblages Research Articles

Spatial organization of earthworm assemblages in pastures of northwestern France

Studying spatial patterns of soil engineers has become an important issue that may contribute to a better understanding of soil functioning. We investigated the spatial patterns of earthworm species assemblages in a recently settled and an old temperate pasture. Earthworms were sampled following a spatially explicit sampling design. Data were analysed using Spatial Analysis by Distance IndicEs methods to describe the main characteristics of earthworm spatial patterns: aggregation index, patch and/or gap number and size, and the frequencies of species association or dissociation. Ten lumbricid species composed the earthworm assemblages in both pastures, some of them displaying a spatial distribution characterized by clusters with areas of patches and gaps. By comparing aggregation indices between the pastures, an increase of the spatial organization level in the community was observed in the old pasture. We also observed differences between the pastures in the number of aggregated species, cluster characteristics, ratio between spatial association/dissociation and spatial overlap. We also found some significant relationships between species pairs that were already described in the literature, enabling us to discuss the possible nature of interactions. Our results suggest that earthworm spatial distribution and community assembly are likely driven by interspecific interactions at the local scale.

Evenness and plant species identity affect earthworm diversity and community structure in grassland soils

Diversity of plant species and the species composition (identity) are known to influence below-ground diversity. In this paper we examine the effects of plant species diversity (richness and evenness), rates of nitrogen application and planting density, on earthworm community structure in grassland. The study was carried out at three sites in Ireland using a Simplex experimental design to define the compositions of the experimental plant communities used.A negative relationship was detected between diversity (evenness) of plant species and diversity of earthworms in the soils. However, plant species identity also affected the structure of the earthworm assemblage. In particular, the legume, Trifolium repens had a strong effect but this was conditional on the rate of nitrogen application. No earthworm species favoured communities dominated by slow growing grasses (Phleum pratense and Dactylis glomerata) (P = 0.02).Higher N inputs reduced earthworm abundance and biomass under T. repens. Earthworm richness, was negatively influenced by elevated amounts of N inputs. No effect of planting density was detected but this factor also did not affect plant biomass production.

Earthworms (Lumbricidae) from a surface layer and wireworms (Elateridae) of forest stands in the anthropogenically-disturbed area of the Děčínská vrchovina Upland (Czech Republic)

In the area negatively affected by air pollution in the past, the earthworm assemblages and the occurrence of wireworms (Elateridae) in forest ecosystems were evaluated in relation to site conditions. From soil samples taken in 38 stands (Fagus, Betula, Alnus, Quercus, Pinus, Larix, Abies) earthworms and wireworms were extracted by means of Tullgren funnels. Eudominant species (Dendrobaena vejdovskyi, D. octaedra, D. illyrica) are typical representatives of forest ecosystems of the Ore Mountains. Relationships were proved to a tree species creating a forest stand and the pH of Ah horizon. The area is characterized by the generally low diversity of earthworms particularly in young stands of beech and Norway spruce. Faunistically rich sites occurred only in a mixed stand (birch, mountain ash, larch) and in a blue spruce monoculture. Reduced abundance of earthworms in the organic matter of mounds was surprising. The type/form of soil preparation, forest weed cover and the age of trees did not affect significantly the earthworm assemblages. The abundance of wireworms was increased in pine and larch stands and reduced in alder and blue spruce stands. The increasing pH value negatively affected the abundance of wireworms.

Effect of land-use on the earthworm assemblages in semi-deciduous forests of Central-West Ivory Coast

In this study, the impact of forest disturbance on earthworm assemblages was assessed using monoliths dug out at 5 m intervals along a gradient of land-use intensification. The land-use types comprised primary forest (as a baseline), secondary forest, tree plantation, fallow, perennial and annual crop. Forest disturbance resulted in a significant decrease in soil organic carbon and pH, while earthworm abundance and biomass increased along the gradient of disturbance. Surprisingly, anthropogenic disturbances in semi-deciduous forest areas have not led to the disappearance of native species to the benefit of exotic species as revealed in former studies. As a result, in this study land-use change had no impact on species richness at the landscape level, even if at local scales, recurrent Chromolaena odorata fallows, multispecies tree plantations and 4 year-old teak plantations hosted the highest average species richness. Multiple regression analyses performed between earthworm communities and environmental variables showed that soil organic carbon and pH are potential indicators of earthworm abundance change.

A simulation model to evaluate the impacts of invasive earthworms on soil carbon dynamics

Recent studies have reported that earthworm invasions alter native communities and impact nutrient cycling in terrestrial ecosystems. We developed a simulation model to evaluate the potential impacts of earthworm invasions on carbon dynamics, taking into consideration earthworm feeding strategies and priming effects on the microorganisms through their casting activities. Responses of carbon stocks (forest litter, soil organic matter, microbial biomass and earthworm populations) and carbon fluxes (litter decomposition, earthworm consumption, and microbial respiration) were used to evaluate an earthworm invasion of a forest ecosystem. Data from a northern temperate forest (Arnot Forest, New York) were adapted for model calibration and evaluation. Simulation results suggest that the impact and outcome of earthworm invasions are affected by pre-invasion resource availability (litter and soil organic matter), invasive earthworm assemblages (particularly feeding strategy), and invasion history (associated with earthworm population dynamics). The abovementioned factors may also determine invasion progress of earthworm species. The accuracy of the model could be improved by the addition of environmental modules (e.g., soil water regimes), precise parameters accounting for individual species attributes under different environmental conditions (e.g. utilization ability of different types of food resources), as well as earthworm population dynamics (size and structure) and interactions with predators and other invasive/indigenous species during the invasion progress. Such an earthworm invasion model could provide valuable evaluation of the complicated responses of carbon dynamics to earthworm invasions in a range of forest ecosystems, particularly under global change scenarios.

Earthworm fauna of Kazakh upland

The species composition of earthworms of different ecosystems in Kazakh upland (Kazakhstan) representing different soil types was assessed for the first time. This eco-region encompasses a large dry steppe area. It is considerably higher than the surrounding Western Siberian plains and Turgay plains. It features elevated plains, melkosopochniki (the local name for highly eroded plateaus), and low mountains. Habitat types characteristic to this area include petrophitic steppes with shrubs and brushwoods, granite rock pinewoods in the low mountains, and micro-phyllous woods associated with lakes and wetlands. Well represented intrazonal communities include wetlands and associated forests. Pine, birch, and aspen woods are found. Earthworms from Kazakh upland belong to seven genera, nine species, and three subspecies. These earthworms are widespread, a majority of which have an antropochoric dispersion however there are several native Asian species and subspecies as well. Development of a hydrological network promotes preservation of some forest species from the past, e.g., Dendrobaena octaedra and Eisenia norden-skioldi pallida. Moreover the boreal species of soil fauna specify the connection of area of research with the West-Siberian plain, Altai and southern Urals Mountains in the past. The epigeic D. octaedra and Dendrodrilus rubidus tenuis play a key role in the structure and function of the earthworm assemblages in the biotopes studied. The earthworm fauna is more diverse in forests of the northern and the southern parts of Kazakh upland than elsewhere in this arid zone of the country.

Earthworm assemblages in an ecotone between forest and arable field and their relations with soil properties

The objective of this work was to assess the effects of a forest-field ecotone on earthworm assemblages. Five sites (blocks) differing in the type of crop rotation used in the field were studied in Central Bohemia, Czech Republic. In each block, sampling was carried out in seven parallel rows perpendicular to a transect from a forest (oak or oak-pine) to the centre of a field, both in spring and autumn 2001-2003. Individual rows were located in the forest (5 m from the edge), in the forest edge, and in the field (at 5, 10, 25, 50 and 100 m distances from the forest edge). The density and biomass of earthworms were lowest in the forest, increased markedly in the forest edge, decreased again at 5 or 10 m distance from the forest edge and then continuously increased along the distance to the field boundary. The highest number of species was found in the forest edge and in the field boundary. Individual species differed in their distribution along the transect. Both density and biomass of earthworms were correlated with distance from forest edge, soil organic matter content, soil porosity, and water infiltration rate.

A null-model analysis of the spatio-temporal distribution of earthworm species assemblages in Colombian grasslands

Abstract:Earthworm assemblages are usually spatio-temporally structured in mosaics of patches with different species composition. We re-analysed results of past research carried out in Eastern Colombia to explore how interspecific competition accounts for this pattern. In three sown pastures and three native savannas, density data matrices were obtained from spatially explicit samplings at several successive dates, and spatio-temporal patterns of species assemblages were described through partial triadic analyses and geostatistics. This first analysis detected assemblage patchiness in the six plots at spatial scales ranging from 6 to 33 m. Species richness ranged from 5 to 6 species per plot. Null models were further used to analyse niche overlap and morphometric distribution patterns at two different scales, i.e. at the ‘plot level’ and the ‘patch level’. Seasonal and vertical niche overlaps were higher than expected by chance at both scales, indicating high environmental constraints on assemblage membership. Within-patch overlaps were lower than plot-scale overlaps. Biometric niche overlap was random at the plot level and was weakly lower than that expected by chance in patches. Body weight was significantly overdispersed and constant whatever the scale, while body length and diameter showed a similar trend within patches. These results suggest that earthworms form distinct assemblages within patches, mainly driven by deterministic responses to competition: ecologically similar species avoid competition through spatial segregation, whereas a minimal level of ecological segregation is required to allow co-existence in a given patch.

The effects of earthworm functional group diversity on earthworm community structure

A comprehensive understanding of how species/functional group interactions determine population dynamics, community composition and their effect on ecosystem functioning is necessary if we are to understand the consequences of species loss. This paper presents data from a mesocosm experiment, based on the simplex design, to examine the effect of interactions between earthworm functional groups, food supply and initial overall biomass on community structure. All communities containing anecic species moved towards domination by anecics. The survival of anecics remained constant irrespective of initial conditions, with no effect of initial community structure, food supply or initial biomass. The proportional biomass of epigeics increased when they were placed in communities dominated by anecics. Initial overall biomass had a significant effect on the survival of endogeics, with increased survival at low biomass. Juvenile production was significantly increased in communities that contained a higher initial abundance of epigeics. The anecics had significantly increased production of juveniles at lower levels of initial biomass. Overall, earthworm functional group diversity had an idiosyncratic effect on earthworm assemblage structure but the presence of synergistic interactions suggests that the persistence and optimal contribution of the earthworm assemblage to ecosystem service is dependent on the presence of a number of functional groups.

Stability of the spatio-temporal distribution and niche overlap in neotropical earthworm assemblages

The spatial distribution of soil invertebrates is aggregated with high-density patches alternating with low-density zones. A high degree of spatio-temporal organization generally exists with identified patches of specific species assemblages, in which species coexist according to assembly rules related to competitive mechanisms for spatial and trophic resources occur. However, these issues have seldom been addressed. The spatio-temporal structure of a native earthworm community in a natural savanna and a grass–legume pasture in the Colombian “Llanos” was studied during a 2-year-period. A spatially explicit sampling design (regular grid) was used to discern the distribution pattern of species assemblages in both systems. Earthworms were collected from small soil pits at three different sampling dates. Data collected from 1 m 2 soil monoliths were also used in the present study. Data were analyzed with the partial triadic analysis (PTA) and correlograms, while niche overlap was computed with the Pianka index. The PTA and correlogram analysis revealed that earthworm communities displayed a similar stable spatial structure in both systems during the 2-year study period. An alternation of population patches where different species' assemblages dominated was common to all sampling dates. The medium-sized Andiodrilus sp. and Glossodrilus sp. exhibited a clear spatial opposition in natural savanna and the grass–legume pasture for the duration of the study. The Pianka index showed a high degree of niche overlapping in several dimensions (vertical distribution, seasonality of population density) between both species. The inclusion of space-time data analysis tools as the PTA and the use of classical ecological indices (Pianka) in soil ecology studies may improve our knowledge of earthworm assemblages' dynamics.

The spatiotemporal pattern of a tropical earthworm species assemblage and its relationship with soil structure: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

The spatiotemporal pattern of a tropical earthworm assemblage (Lamto, Côte d'Ivoire) was assessed using a Partial Triadic Analysis (PTA). The abundance of earthworm species was estimated on five occasions covering two years within a single plot sampled with 100 sampling locations. The results showed that the earthworm community was highly structured in space and that the spatial pattern was stable through time. The Partial Triadic Analysis allowed extracting the earthworm community pattern that was common to all the dates. It was possible to identify which dates differed from the common model and which species were responsible for these discrepancies. The main pattern revealed by PTA was also submitted to spatial statistics to assess its significance. The results showed that the earthworm community is structured as a juxtaposition of patches dominated by different species. This pattern appeared to be constant during our 2-year study. When species were grouped following their impact upon soil structure dynamics the surveyed area appeared to be made of adjacent patches dominated either by compacting or decompacting earthworm species. The functional implications of this pattern are discussed and the spatial structure of the earthworm community was compared to soil bulk density distribution. The Mantel tests revealed a very strong relationship between soil bulk density and earthworm community structure.

The megadrile fauna (Annelida: Oligochaeta) of Maghreb: a biogeographical and ecological characterization: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

In the last two decades, the earthworm fauna of western North Africa, poorly known previously, has received many original contributions. These and additional new data (including five new regional records) from the authors' collecting make it possible to outline a satisfying picture of its ecological and biogeographical traits. In Maghreb, extensive land areas have not yet experienced the methods and effects of modern agriculture, and cultivated fields can host dense and diverse earthworm assemblages. Some species maintain narrow habitat preferences: Allolobophoridella eiseni is frequently corticicolous; Eisenia xylophila lives in decaying logs of Quercus suber, protected by the cork sleeve; Octodrilus complanatus does not occur in forests but dwells in pastures and grassland with sparse trees, whereas O. maghrebinus is only to be found in oak forests. The litter-dwelling species are few: A. eiseni, Dendrobaena lusitana, D. byblica and Dendrodrilus rubidus the last two being rare and scanty and probably of recent introduction. None of the autochthonus species recorded is adapted to arid soils, except for Hormogaster redii which, owing to its long aestivation period, can tolerate inhabiting areas where the rainy season is restricted to a few weeks per year. In contrast, the diversity of the aquatic forms is remarkable: Criodrilus lacuum, Eiseniella neapolitana, E. tetraedra, Allolobophora molleri complex, Helodrilus cfr. oculatus, H. rifensis, and Nicodrilus sp. The list of taxa so far recorded (38) is shorter than that of other Palaearctic territories of similar size and environmental variety. However, it comprises some narrow-range and broad-range endemics which strongly characterise it. The most evident affinities are with the Iberian (and Macharonesian) fauna: they concern A. molleri complex, D. lusitana, Allolobophora borellii and Lumbricus friendi. A comparable relationship is indicated by the Franco-Iberian genus Prosellodrilus, represented in Maghreb by P. doumandjii and P. festai. Instead, the two endemic species of Octodrilus (O. maghrebinus and O. kabylianus) and E. xylophila suggest unexpected relationships with the Balkan fauna.

The spatiotemporal pattern of a tropical earthworm species assemblage and its relationship with soil structureThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Summary The spatiotemporal pattern of a tropical earthworm assemblage (Lamto, Cote d'Ivoire) was assessed using a Partial Triadic Analysis (PTA). The abundance of earthworm species was estimated on five occasions covering two years within a single plot sampled with 100 sampling locations. The results showed that the earthworm community was highly structured in space and that the spatial pattern was stable through time. The Partial Triadic Analysis allowed extracting the earthworm community pattern that was common to all the dates. It was possible to identify which dates differed from the common model and which species were responsible for these discrepancies. The main pattern revealed by PTA was also submitted to spatial statistics to assess its significance. The results showed that the earthworm community is structured as a juxtaposition of patches dominated by different species. This pattern appeared to be constant during our 2-year study. When species were grouped following their impact upon soil structure dynamics the surveyed area appeared to be made of adjacent patches dominated either by compacting or decompacting earthworm species. The functional implications of this pattern are discussed and the spatial structure of the earthworm community was compared to soil bulk density distribution. The Mantel tests revealed a very strong relationship between soil bulk density and earthworm community structure.

The megadrile fauna (Annelida: Oligochaeta) of Maghreb: a biogeographical and ecological characterizationThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Summary In the last two decades, the earthworm fauna of western North Africa, poorly known previously, has received many original contributions. These and additional new data (including five new regional records) from the authors' collecting make it possible to outline a satisfying picture of its ecological and biogeographical traits. In Maghreb, extensive land areas have not yet experienced the methods and effects of modern agriculture, and cultivated fields can host dense and diverse earthworm assemblages. Some species maintain narrow habitat preferences: Allolobophoridella eiseni is frequently corticicolous; Eisenia xylophila lives in decaying logs of Quercus suber , protected by the cork sleeve; Octodrilus complanatus does not occur in forests but dwells in pastures and grassland with sparse trees, whereas O. maghrebinus is only to be found in oak forests. The litter-dwelling species are few: A. eiseni, Dendrobaena lusitana, D. byblica and Dendrodrilus rubidus the last two being rare and scanty and probably of recent introduction. None of the autochthonus species recorded is adapted to arid soils, except for Hormogaster redii which, owing to its long aestivation period, can tolerate inhabiting areas where the rainy season is restricted to a few weeks per year. In contrast, the diversity of the aquatic forms is remarkable: Criodrilus lacuum, Eiseniella neapolitana, E. tetraedra, Allolobophora molleri complex, Helodrilus cfr. oculatus, H. rifensis , and Nicodrilus sp. The list of taxa so far recorded (38) is shorter than that of other Palaearctic territories of similar size and environmental variety. However, it comprises some narrow-range and broad-range endemics which strongly characterise it. The most evident affinities are with the Iberian (and Macharonesian) fauna: they concern A. molleri complex, D. lusitana, Allolobophora borellii and Lumbricus friendi . A comparable relationship is indicated by the Franco-Iberian genus Prosellodrilus , represented in Maghreb by P. doumandjii and P. festai . Instead, the two endemic species of Octodrilus (O. maghrebinus and O. kabylianus) and E. xylophila suggest unexpected relationships with the Balkan fauna.

Single‐Tree Influence on Earthworms in Forest Soils in Eastern Kentucky

AbstractVegetation may affect earthworm populations directly through inputs of litter and leachates, and indirectly through alteration of soil properties. This study examined the characteristics of earthworm populations on an area where small‐scale spatial patterns in soil properties were previously shown to be due to the influence of individual trees and understory species. Earthworm densities in the O horizon and in the upper 20 cm of mineral soil ranged from 0 to 20 and from 0 to 80 individuals/m2, respectively. Density was significantly lower in mineral soils under both yellow poplar (Liriodendron tulipifera L.) and eastern hemlock (Tsuga canadensis [L.] Carr.) when rhododendron (Rhododendron maximum L.) was present in the understory, compared with under the same two tree species when rhododendron was absent. Bimastos parvus Eisen, a species characteristic of inhospitable sites, was dominant on rhododendron plots, but was replaced by Komarekiona eatoni Gates and Eisenoides carolinensis Michaelsen in the absence of rhododendron, especially on plots under yellow poplar. In mixed‐species forests, abundance and species composition of earthworm assemblages are spatially variable in correspondence with patterns of soil properties and of the occurrence of tree and understory plant species.

Characteristics and ecological relationships of earthworm assemblages in undisturbed forest soils in the southern Appalachians of Kentucky, USA

Characteristics and ecological relationships of earthworm assemblages in undisturbed forest soils in the southern Appalachians of Kentucky, USA