Abundance Of Earthworm Species Research Articles

Two aspects of earthworm bioturbation: Crop residue burial by foraging and surface casting in no-till management

In no-till agroecosystems, presence of the earthworm Lumbricus terrestris L. can be a key driver in the replenishment of soil organic matter stocks post-harvest, through surface residue foraging and incorporation. The impact on such systems under different climatic conditions is, however, still unquantified. A field experiment was designed to determine incorporation of cereal harvest residues at three no-till agricultural sites in boreal conditions (SW Finland) focusing on L. terrestris impacts over the period from autumn harvest to spring sowing. Either spring barley, wheat or oats were cultivated at the sites. Following the harvests, representative masses of residues were applied on small experimental plots (0.25 m2) with cleaned soil surfaces in areas of inherently high (LT+: 10.6 ± 2.1 ind. 0.25 m-2) and low (LT-: 1.8 ± 0.7 ind. 0.25 m-2) L. terrestris density within the fields. Residues were covered with metal mesh caging and left until spring sowing, when changes in residue mass were recorded and plots sampled for earthworms. The reduction of straw residue mass varied between sites, from no difference between the LT+ and LT- treatments to 19 % and 59 % higher mass reduction in LT+. Amount of earthworm castings on the residues was also quantified and findings indicated a positive correlation with earthworm (also endogeic) density. For L.terrestris, earthworm species abundance relationships indicated competitive interaction with epigeics and positive interaction with endogeics. Results showed that L. terrestris foraging can enhance the incorporation of cereal surface residues outside of the boreal growing season and that earthworm surface casting also has a role in residue burial. However, the increase of incorporation by L. terrestris activity, interrupted by winter conditions, was moderate and did not lead to marked exposition of the soil surface by experimental end, even at those plots with the highest L. terrestris foraging. The incorporation rate estimates may have been unrepresentative due to the exceptionally late harvest during the study period. Investigations covering the whole year from multiple growing seasons are needed for a comprehensive assessment of earthworm impacts on crop surface residue dynamics.

Historical patterns of exotic earthworm distributions inform contemporary associations with soil physical and chemical factors across a northern temperate forest

Understanding environmental factors related to exotic earthworm distributions across invasion stages (i.e., introduction, colonization, regional spread) is critical for assessing long-term impacts on previously earthworm-free forests. Studies following earthworm community establishment in North America, however, remain limited. We address this by characterizing historical and current exotic earthworm distributions in a regionally representative aspen-dominated forest, where their presence was first documented in the early 1900s. We map historic earthworm distribution records in a 360-km2 area surrounding our current study site, and re-analyze data collected nearly 60 years ago to inform contemporary associations between species densities and environmental factors. Field surveys were conducted over two years (2008–2010) using 10 permanent plots, with concurrent measurements of environmental ‘effect factors’ determined by large-scale ecosystem processes (leaf litter inputs, soil physical properties, soil C and N content), and environmental ‘response factors’ likely impacted by earthworm activity over short time scales (annual litter mass loss and soil isotopic values). Present-day communities included five exotic species with varying densities: Lumbricus rubellus ≥ Lumbricus terrestris >> Dendrobaena octaedra ≥ Aporrectodea spp. (Aporrectodea trapezoides + Aporrectodea caliginosa). These species were also present in the landscape in the early to mid-1900s though shifts in species composition, particularly the movement of L. terrestris into upland forest soils, were evident. Over two years, earthworm community composition did not show strong temporal or spatial trends characteristic of incipient invasions. However, species-specific associations with environmental factors were observed: L. terrestris and L. rubellus densities were positively associated with soil C and N content, Acer rubrum (red maple) inputs, and soil moisture; and were negatively associated with Pinus strobus (white pine) inputs. D. octaedra, and Aporrectodea spp. densities were positively associated with % sand; and negatively associated with plot-to-road distance. Soil moisture and texture were significant drivers of earthworm species abundance in historical surveys, though associations with soil C were only evident for Aporrectodea spp. Contemporary associations between earthworm species and soil C and N content suggest greater nutrient limitation in upland forest soils, while the importance of plot-to-road distance suggests the persistence of dispersal limitation and repeated introductions as a mechanism maintaining population densities. Species-specific associations with environmental response variables were also observed, where: surface soil δ13C depletion was associated with Aporrectodea spp. and D. octaedra biomass; δ15N enrichment was associated with total earthworm biomass, but negatively associated with L. rubellus biomass; and increased leaf litter mass loss was associated with L. terrestris and juvenile biomass. As soil C and N pools were not higher in plots with higher earthworm biomass, these results suggest earthworm activity may influence soil nutrient cycling by decreasing turnover times of nutrient pools over the long-term. Our results characterize exotic earthworm distributions at scales relevant to forest ecosystem processes, and allow for future extrapolation of laboratory and controlled field studies assessing impacts on soil nutrient cycling across northern temperate forests.

Diversity and abundance of earthworms in land use systems in central-western Colombia

The neotropical landscapes of Colombia's Andean region are characterized by a mosaic of agroecosystems presenting a range of vegetational cover for which soil fauna adaptation is still unknown. To analyze the diversity and abundance of earthworm species in relation to changes in selected soil physical and chemical parameters (bulk density, C stock, N stock, %C, %N, 13C, 15N, C:N ratio), these systems were classified into five categories according to land use intensity: non-intensive (NI), low intensity (LI), medium intensity (MI), high intensity (HI), and maximum intensity (IN). The influence of livestock production was confirmed in the significant differences observed in bulk density and 15N between NI, HI, and IN (P < 0.05). The C and N contents of IN systems (pastures) differed significantly (P < 0.05) in comparison with the other categories. Average δ 13C at the three soil depths evaluated (0–10, 10–20, and 20–30 cm) ranged between −24.9 for LI and −22.87 for IN, indicating that soil organic carbon was related to C3-type vegetation for all land uses and vegetation covers. Overall, 26 earthworm species were recorded, of which 16 showed a high capacity to adapt to natural, NI, LI, and MI systems. Depending on land use intensity, significant differences were also observed (P < 0.05) in the origin and ecological category of earthworms, mainly in terms of the following variables: diversity of native species, diversity of endogeic species, abundance of native species, biomass of native species, and abundance of exotic species. Based on the results obtained, the most favorable mosaic systems for agrobiodiversity conservation were identified as well as those subsystems that require special management to solve problems of habitat degradation.

Abundance of earthworm species in Estonian arable soils

Specific composition of earthworm community has indicative value for evaluating the impact of agricultural practice on soil. The occurrence of species only like Aporrectodea caliginosa, Aporrectodea rosea, Lumbricus rubellus tolerant to disturbance is the result of intensive tillage and agricultural practice or the influence of strong limiting ecological factor. A community including more sensitive species Lumbricus terrestris and Aporrectodea longa, or the most sensitive species Allolobophora chlorotica and Lumbricus castaneus, indicates more favourable conditions of habitat.

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 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.