Occurrence Of Earthworms Research Articles

Mapping of suitable habitats for earthworms in China

Earthworms are important soil organisms that play critical roles in ecosystem material cycling and energy flows. Discovering and predicting the distribution of earthworm habitats is critical for managing biodiversity conservation projects and improving ecosystem health. However, earthworm data are challenging to obtain, and studies on the distribution of earthworms and factors affecting this have mainly been conducted in fields at a small scale; the spatial distribution of earthworms throughout China remains unclear. Species distribution models have been effectively used in macro-scale species suitability distribution studies; however, they have certain limitations. Thus, here, we optimized the maximum entropy model (MaxEnt) to achieve low complexity and high transferability, and the model was capable of predicting the potential distribution of earthworms in China. Modeling was based on the use of a developed database containing 286 earthworm occurrence records and 31 environmental variables (19 climatic, 9 soil, and 3 topographic variables). Results show that earthworm distribution is mainly controlled by the following environmental variables (with corresponding contribution rates): minimum temperature of the coldest month (18.47%), digital elevation model (17.65%), coarse fragments (16.72%), soil organic carbon (9.65%), soil type (7.53%), mean diurnal range (5.35%), and soil thickness (5.05%). The variables with the strongest influence on distribution are climate followed by landforms and soils. The relationship between the effect of environmental variables and earthworm distribution is not simple and linear, and each element has a certain threshold range. Only 50.67% of the total land area of China provides a suitable habitat for earthworms, and there are remarkable spatial differences. Of the various ecosystems, woodland ecosystems provide most of the suitable habitats, followed by cropland and grassland ecosystems, which together account for 45.74% of the land area. This study can be used as a reference for understanding and assessing ecosystem health, sustainability, and for enabling biodiversity conservation.

Agricultural farming intensification significantly reduced earthworm abundance and diversity in Usangu agro-ecosystems, Tanzania

Earthworms an ecologically important group of invertebrates that are crucial to delivery of many ecosystem services, but also considered ecosystem engineers playing an important role in soil fertility and land productivity. Earthworms facilitate breakdown and decomposition of plant and animal materials releasing plant nutrients. Earthworm burrows allow air and water movement in the soil but also improve soil fertility and drainages. Earthworm population in agricultural soils is influenced by different factors i.e., tillage, farming activities, soil chemistry as well as chemical contaminants. Agricultural (paddy farming) intensification with increased and excessive use of agrochemicals (fertilizers, pesticides, and herbicides) may affect earthworm population in agricultural soils. Recently, there scant studies conducted to characterize earthworm abundance and diversity in Tanzania's agro-ecosystem. Therefore, the present study characterized earthworm population in agricultural soils of contrasting intensification in Usangu agro-ecosystem (UA) to understand influence of current land use on earthworm abundance and their diversity as they have a vital role in agro-ecosystem productivity and sustainability. This study found that current paddy farming and associated activities in UA negatively affect earthworm occurrence, distribution, and diversity. Where only four dominant earthworm species were determined (Apporectodea caliginosa (endogeic), Lumbricus terrestris (Anecic), Pontoscolex corentrurus (endogeic), Fimoscolex sporadochactus (Anecic)) compared to other tropical areas. But also, highly intensified paddy farming areas (i.e., Chimala, Igalako, Ihahi, Kapunga, Mahongole, and Uturo) were observed to have earthworm abundance <25 individuals/m2 an FAO recommended earthworm count/m2 in healthy soils compared to less intensified schemes (25-40 earthworm/m2). The earthworm abundance and biomass determined in UA was below global average of 78 individuals per m2 and 150 g/m2, indicating that UA is in deteriorating quality. Thus, current farming practices creates unfavourable environmental conditions which likely leads to migration of earthworm to other land use or death due to harsh environment created. High earthworm abundance and biomass improve land productivity via nutrient recycling, thus low earthworm counts and diversity in UA likely to threaten agro-ecosystem sustainability. The present study provides baseline information on earthworm abundance and their diversity in UA and Tanzania.

Diversity and Abundance of Delineated Earthworm (Annelida: Clitellata) in Pakistan: A Review.

Earthworm, a ubiquitous (but neglected) macro-invertebrate, is found in terrestrial vicinity of Pakistan. Moreover, the occurrence of earthworms is often diverse with fluctuating quantity depending upon abiotic factors and land usage patterns. The aim of this study was to summarize all the reported information related to earthworm diversity in different areas of Pakistan. Almost all the data published from year 2001 to 2021 were collected. Following data organization, total 42 earthworm's species including five families (Acanthodrilidae, Lumbricidae, Moniligastridae, Octochaetidae and Megascolecidae) were reported from various researchers. Among five families, family Acanthodrilidae was found to have only one specie (Ramiella bishambari), Lumbricidae consist of 10 species (Apporactodea rosea, Allolobophora trapezoids, Allolobophora chloroticaa, Aporrectodea longa, A. caliginosa, Bimastus parvus, Eisenia fetida, Helodrilus foetidus, Lumbricus terrestris and L. rubillus), Moniligastridae has two species (Drawida nepalensis and D. pellucida) while Octochaetidae possess only one specie (Eutyphoeus incommodus). The most abundant and diverse family Megascolecidae consist of 28 earthworm species in all habitats of different regions of Pakistan. Among geographical areas, Faisalabad was found as the richest territory with most reported earthworm species (i.e. 28). The current study suggests further in depth research to explore the unidentified and/ missing species of earthworms in Pakistan.

Global earthworm distribution and activity windows based on soil hydromechanical constraints

Earthworm activity modifies soil structure and promotes important hydrological ecosystem functions for agricultural systems. Earthworms use their flexible hydroskeleton to burrow and expand biopores. Hence, their activity is constrained by soil hydromechanical conditions that permit deformation at earthworm’s maximal hydroskeletal pressure (≈200kPa). A mechanistic biophysical model is developed here to link the biomechanical limits of earthworm burrowing with soil moisture and texture to predict soil conditions that permit bioturbation across biomes. We include additional constraints that exclude earthworm activity such as freezing temperatures, low soil pH, and high sand content to develop the first predictive global map of earthworm habitats in good agreement with observed earthworm occurrence patterns. Earthworm activity is strongly constrained by seasonal dynamics that vary across latitudes largely due to soil hydromechanical status. The mechanistic model delineates the potential for earthworm migration via connectivity of hospitable sites and highlights regions sensitive to climate.

Predictive mapping to identify refuges for plant communities threatened by earthworm invasion

Abstract Biological invasions by cryptic ecosystem engineers can alter the ecological and socio‐economic values of ecosystems in ways that may take decades to detect. The invasion of North American glacial refuges by non‐native earthworms offers a prominent but understudied example of a cryptic invasion. Non‐native earthworms are known to alter carbon sequestration, disrupt mycorrhizal networks and homogenize plant communities, but natural resource managers still lack robust protocols to identify and safeguard high conservation value communities (HCVCs) from such invasions. In the absence of such protocols, or reliable methods to eradicate non‐native earthworm populations once established, there is an urgent need for methods to identify HCVCs at risk of or potentially shielded from earthworm invasion by the existence of abiotic barriers to their dispersal or persistence in such sites. We developed species distribution models (SDMs) using in situ field surveys and remotely sensed data to (1) identify factors limiting the occurrence of non‐native Lumbricus earthworms in imperilled coastal Douglas‐fir (Pseudotsuga menziesii) forest and Garry oak (Quercus garryana) and maritime meadow ecosystems endemic to glacial refugia of the Pacific Northwest of North America and to (2) evaluate their influence on plant species diversity and identify abiotic factors capable of preventing their dispersal or persistence at a site. As predicted, shallow, drier soils and steeper terrain limited earthworm occurrence and abundance in our highly heterogeneous study area, and earthworm presence appeared to reduce plant species richness. Our results indicated that HCVCs endemic to shallow‐soil (&lt; 12 ± 3 cm) sites that experience regular summer drought appear to act as refuges from invasion by non‐native earthworms. Our results also elevate concerns for the conservation of deep‐soil habitats not isolated from earthworm invasions by shallow soil, saltwater or other barriers to earthworm dispersal. The SDMs developed here offer guidance to the identification of potential refuges for the conservation of imperilled native species and communities from the detrimental effects non‐native earthworms in glacial refugia of western North America and should thereby facilitate proactive planning by conservation practitioners.

Effects of rare arable plants on plant diversity, productivity and soil fertility in agricultural fields

Agricultural intensification has caused a strong agro-biodiversity decline in Europe, with high losses in rare arable plants. A better understanding of the relationship between these species, agricultural productivity, and other ecosystem functions can improve conservation management. The study was performed on an experimental field near Munich. To examine the results under field conditions, study plots were additionally established on ten arable fields distributed in the Munich Plain, an area with nutrient poor soils in southern Germany. We sowed a mixture of ten rare arable plant species at varying crop densities and compared them to plots without rare arable plants. To assess the effects on plant diversity and productivity, the cover and species richness of rare and common arable plants and the crop and arable plant biomass were assessed. The organic matter, nitrogen concentration, as well as the biomass and abundance of earthworm (biannually sampled for two years) were analyzed to determine the impact on soil fertility.Our results showed that sowing rare arable plants did not negatively affect crop biomass. Arable plant biomass and cover of rare arable plants were highest when no crops were sown. There was no difference between reduced and regular crop sowing densities on rare arable plant cover. In our field experiment, earthworm occurrence and soil organic matter were probably influenced by pre-crops (two years of clover grass before the experiment) and summer droughts during the study period. However, no significant effects of sowing rare arable plants on soil fertility were detected. These results were partly verified from results of the field study.At least on nutrient-poor soils, rare arable plant sowing may be a suitable tool to promote plant diversity conservation without negatively affecting crop production. That the sowing of rare arable plants did not significantly affect the indicators for soil fertility suggests that biomass production of rare arable plants was too low to have an impact on the crops and a benefit for soil fertility. Insignificant effects on crop biomass also suggest that sowing rare arable plants does not automatically lead to crop losses. As organic matter, nitrogen concentration and earthworm occurrence slowly respond to environmental changes, they should be investigated in further long-term experiments. This study shows that conservation of rare arable plants and food production on nutrient poor fields can be combined. Therefore, land sharing may be a suitable tool for nature conservation and ecosystem functionality on arable land.

Chemical properties of soil and occurrence of earthworms in response to soil compaction and different soil tillage in cereals

Chemical properties of soil and occurrence of earthworms in response to soil compaction and different soil tillage in cereals

Using an Environment-Friendly Fertiliser from Sewage Sludge Ash with the Addition of Bacillus megaterium

Sewage sludge ash (SSA) is considered to be a valuable secondary raw material for the production of phosphorous fertilisers. This method of recycling may also be a solution to the problem posed by the growing amount of this waste. An innovative suspension fertiliser (SSAB) was produced from SSA and the phosphorus-solubilising bacteria Bacillus megaterium and was tested in a field experiment in the presence of spring wheat as the test plant in comparison to conventional fertilisers (superphosphate, phosphorite). Two variants of plant protection were also adopted: full chemical plant protection (+PP) and no plant protection (−PP). Besides affecting yield, it was expected that SSAB would not worsen the state of the soil environment. This paper presents SSAB effect on soil moisture and temperature, soil pH, content of toxic elements (As, Cd, Cr, Ni and Pb) in the soil, abundance of heterotrophic bacteria and fungi and the occurrence of earthworms. SSAB did not affect the tested soil characteristics when applied in reasonable doses. Plant protection had an individual effect on soil properties but did not modify the fertiliser action. SSAB may be a potential substitute for P fertilisers produced from non-renewable raw materials in times of shortage. Further long-term research is recommended to confirm these findings.

Distribution and abundance of exotic earthworms within a boreal forest system in southcentral Alaska

Little is known about exotic earthworms (Oligochaeta: Lumbricidae) in Alaska outside its southeastern panhandle. This study documents the distribution of exotic earthworms in the relatively undisturbed Kenai National Wildlife Refuge (KNWR), a large, primarily wilderness refuge in southcentral Alaska. We sampled 69 sites near boat launches, along road corridors, and in low human impact areas > 5 km from the road, finding three species of earthworms ( Dendrobaena octaedra, Dendrodrilus rubidus, and Lumbricus terrestris). Most road sites (90%) and boat launches (80%) contained earthworms; half (50%) of low human impact sites contained earthworms. Distance to roads was the only significant factor in predicting earth worm occurrence; soil pH, soil moisture, leaf litter depth, and vegetation cover were not. The disparate distributions of these three species suggest that within the KNWR road construction and vehicle traffic played a role in dispersal of the widespread, abundant Dendrobaena octaedra and uncommon Dendrodrilus rubidus; bait abandonment appeared to be the primary method of introduction of Lumbricus terrestris. While the distribution of harmful anecic earthworms in KNWR is currently limited, the prohibition of Lumbricus spp. as bait within conservation units in Alaska may be warranted.

경남 거창 농경지 멧돼지(Sus scrofa)의 식이물 분석

최근 멧돼지의 개체수 및 농작물 피해 증가로 인하여 사회적 문제를 야기 시키고 있다. 국내 멧돼지에 대한 연구는 미미하여 향후 효과적인 멧돼지 관리를 위해서는 종에 대한 생태적 연구가 필요하다. 본 연구는 2012년 5월부터 12월까지 경남 거창군 일대에서 유해야생동물 포획을 통해 수집된 멧돼지 위 내용물(n=79) 분석을 통하여 식이습성 구명 및 선호 농작물을 파학하기 위해 수행되었다. 연구 결과 멧돼지는 주로 식물성 먹이를 섭식하며, 계절별로 유의한 차이를 나타냈다. 식물성 먹이는 잎-줄기가 83.5%로 가장 높은 출현율 보였으며, 농작물을 포함한 식물성 먹이는 건중량의 93.5%을 차지하였다. 무척추동물의 발견 빈도는 높았으나 빠르게 소화되는 특성으로 인하여 건중량은 낮게 나타났다. 식이농작물로는 밤, 벼, 사과 등이 선호하는 농작물로 나타났다. 수확기 농작물은 멧돼지가 야생 먹이보다 선호하여 의도적으로 섭식하는 것으로 판단된다. 지렁이는 총 수집된 위에서 50%의 출현율을 보였으며, 섭식 마릿수는 여름에 가장 높고, 겨울에 낮은 것으로 나타났다. 멧돼지는 전형적인 잡식성의 성향을 보이며, 시기에 따라 섭식하는 식이물이 다른 것으로 나타났다. 향후 멧돼지에 의한 농작물 피해를 줄이기 위해서는 밤나무림에 인접한 논과 사과 과수원의 우선적인 피해방지가 필요할 것으로 판단된다. Wild boar have increased in recent years in Korea where damage to agricultural crops is considered as a social issue. The ecological studies on wild boar are essential for the effective management in the future. During May and December 2012, We collected 79 wild boar stomach samples from culling program implementation to reduce agricultural damage in Geochang County and analyzed stomach contents to figure out wild boar diet habit and which crop was preferred. There was seasonal variation in the diet. Plant foods represented up to 93.5% of the diet and were consumed more frequently than animal foods. Invertebrates occurred with high frequency but were underestimated in dry weight because they are rapidly digested. Agricultural crops consumed comprised mainly chestnuts(33%), rice(33%), and apples(24%). Agricultural crops are also a potentially important food resources for wild boar. The frequency of occurrence of earthworms was 50% of diet. Earthworm consumption generally increased in summer, and then decreased in winter. Our results show that wild boar can be considered an omnivore whose diet consists of plant and animal foods. To reduce wild boar agricultural damages, We have to focus on the prevention effort to rice paddy adjacent to chestnut forest and to apple orchard.

Reconstructing mole tunnels using frequency-domain ground penetrating radar

The European mole (Talpa europaea L.) inhabits an underground tunnel system whereby the density, extent and condition of the subsurface tunnels are indicative of its activity. Currently, no survey method was able to reveal the spatial extent and condition of the mole's tunnel network. Frequency-domain ground penetrating radar (GPR) was evaluated on its potential to image these shallow tunnel systems. This technique allows for a non-invasive, high-resolution mapping of the subsurface. We examined the effectiveness of this GPR system for delineating the mole's tunnel network. The integration of different depth slices allowed a detailed overview of the tunnel system. Automatic feature recognition on these GPR images was proven valuable for the detection and representation of the mole tunnels. The GPR survey proved successful in mapping the mole's tunnel network, which facilitates the interpretation and characterization of the mole's living environment. This can be linked to the occurrence of earthworms, as the principle food source of the moles, which regulate important ecosystem processes within the soil. This offers new perspectives for the understanding of the mole's habitat.

Predicting exotic earthworm distribution in the northern Great Lakes region

Identifying influences of earthworm invasion and distribution in the northern Great Lakes is an important step in predicting the potential extent and impact of earthworms across the region. The occurrence of earthworm signs, indicating presence in general, and middens, indicating presence of Lumbricus terrestris exclusively, in the Huron Mountains located in the Upper Peninsula of Michigan were modeled using generalized linear models and stepwise regression to identify important environmental variables. Models were then applied to earthworm occurrence data from Seney National Wildlife Refuge, also located in the Upper Peninsula of Michigan to validate results. Occurrence of earthworm signs was associated with high soil pH, high basal area of earthworm preferred overstory species, and north facing aspects. Middens of L. terrestris were associated with high soil pH, high basal area of preferred species, and close proximity to roads. The resulting model for L. terrestris was incorporated into a geographic information system (GIS) to map the expected distribution, both current and potential, across the study area. Results indicate that L. terrestris has not yet fully saturated its potential habitat, as it is currently found close to roads and has yet to establish in most interior forests sampled. Comparing field measured data to GIS layers revealed limitations in the precision of publicly available spatial data layers that should be addressed in future attempts to predict the extent of earthworm invasion across the larger Great Lakes region. However, within the Huron Mountains, it is predicted that the distribution of L. terrestris will cover, at minimum, 41 % of the area.

Road age and its importance in earthworm invasion of northern boreal forests

SummaryRoads are an important conduit for the spread of invasive species. Road age is a key factor that could influence the susceptibility of roads to invasion as older roads are typically subject to higher cumulative levels of human disturbance and propagule pressure than younger roads. We investigated the effects of road age on the spread of non‐native earthworms, which act as ecosystem engineers.We sampled earthworms and habitat variables at 98 roads in the boreal forest of Alberta, Canada, to determine the influence of road age on non‐native earthworm occurrence at the landscape level. The extent and rate of local spread were also assessed at seven sites adjacent to old and young roads. Generalized estimating equations and zero‐inflated negative binomial regression were used to analyze landscape‐ and local‐level results, respectively. We used our models to create maps that predict the current and potential future extent of earthworms in north‐eastern Alberta.Probability of earthworm occurrence and extent of spread increased as road age increased. Areas closer to agriculture and towards the south and west of our study area were also significantly more likely to be invaded by earthworms.Our spread model indicated that approximately 9% of the boreal forest of north‐eastern Alberta is likely invaded by earthworms currently. This is projected to increase to 49% of suitable forest habitat over the next 50 years as human development intensifies in this region.Synthesis and applications. Although the effects of roads and linear features are commonly investigated in relation to native species, our results emphasize the importance of considering the impacts of linear feature creation on the spread of invasive species. We demonstrate that road age in particular can be an important factor affecting the spread of invasive species. In the boreal forest, reducing the number of roads being constructed, restricting traffic, and reclaiming temporary roads will be critical to reduce the future extent of earthworm invasions.

Earthworm communities a bioindicator of arable land management practices: A case study in semiarid region of India

Abstract The abundances and activities of earthworms in arable lands depend strongly on management practices and; therefore earthworm can act as a potential bioindicator of land use practices. In this study earthworm diversity and abundances was measured in three differently managed agro-ecosystems i.e. conventional, integrated and organic, in some sites of northern semiarid region of India. The maximal numbers of earthworm occurrence were in integrated farming system (100%, all studied sites showed the presence) followed by organically managed (70%) and conventional (18.9%) agro-ecosystems. A total of six species belonging to four different families were identified during this survey and all recorded earthworm species were present in organically managed agro-ecosystems, while integrated and conventional arable lands exhibited only three earthworm species. The abundance of earthworms in arable system was also directly related to the management practices. The values of ecological indices e.g. Shannon diversity (H′), species dominance (C), the species richness (S) and evenness (E) indicated the anthropogenic pressure on earthworm communities in arable lands of northern India.

Human-facilitated invasion of exotic earthworms into northern boreal forests

Recreational and industrial development is rapidly expanding in the boreal forest of western Canada. Concerns exist that such activity is facilitating the introduction and spread of non-native species such as exotic earthworms. The mechanisms by which earthworms are introduced and spread in forested systems are not well understood. Given the poor intrinsic dispersal abilities of earthworms, we propose 4 major introduction mechanisms: 1) abandonment of worms brought as fishing bait; 2) dispersal via vehicles; 3) dispersal via vertebrate predators; or 4) dispersal via waterways. To test these hypotheses, we sampled earthworms in forest stands near boat launches, roads, seismic lines, forest interiors, and remote shorelines of lakes in the boreal forest of northern Alberta, Canada. Boat launches and roads had a significantly higher probability of earthworm occurrence (54% of plots occupied) compared with the other locations (13% of plots occupied). Species commonly used as fishing bait occurred more often near boat launches (18% of plots occupied) than near roads alone (1% of plots occupied). These results suggest that vehicle transport and bait abandonment may both be mechanisms of earthworm introduction. The consequences of these introductions remain unclear but suggest that reduced road construction and regulations prohibiting the discarding of bait need to be considered to slow earthworm invasions.

Influence of copper fungicide residues on occurrence of earthworms in avocado orchard soils

The compost worm Eisenia fetida was used to demonstrate the avoidance by worms of Cu contaminated soil. Soils were collected from two avocado orchards in north eastern New South Wales, Australia. In avoidance trials, worms preferred non-contaminated control soils, sourced from adjacent to the orchard or an OECD control soil, when Cu residues in the orchard soils reached 4–34 mg Cu kg −1. At levels of 553 mg Cu kg −1, 90% avoidance of orchard soil was observed. The worms showed preference for the soils in the order; uncontaminated field derived soil >OECD standard soil >Cu contaminated orchard soil. It was demonstrated that OECD standard soil was less favoured by worms than control soil derived from the test sites. While Cu was found to be the primary influence on worm avoidance in orchard soil, other factors, such as elevated soil Zn concentrations, could not be discounted. In a corresponding field study, it was shown that earthworms occurred at lower density in orchard soils with a history of Cu fungicide use. In one such orchard, soil Cu concentrations of up to 270 mg kg −1 were determined and no earthworms were found, while nearby control sites and less contaminated sites within the orchard had up to 40.7 g m −2 earthworm biomass. Considering the potential for Cu to accumulate in these soils and the subsequent impacts on soil biota, our results highlight the importance of limiting future application of Cu based fungicides.

Food habits of European badgers (Meles meles) along an altitudinal gradient of Mediterranean environments: a field test of the earthworm specialization hypothesis

Food specialization by European badgers (Meles meles) is a largely debated controversy. Data from Mediterranean areas indicate small importance of earthworms (Lumbricus spp.) in badger diet and support the idea that badgers are generalist predators. Nevertheless, only dry areas have been sampled so far. We studied badger diet in six areas along an elevation gradient with different rainfall and habitat conditions, which influenced earthworm availability. We evaluated the influence of earthworm availability on badger diet along this environmental gradient. Badgers used a wide range of prey items in the different habitats and seasons sampled. In contrast with other Mediterranean studies, earthworms made an important contribution to badger diet (27% of estimated volume). Earthworm occurrence in the diet was high in elevated and wet habitats and in spring and autumn–winter. Earthworm consumption was nonlinearly related to availability, indicating high intake compared with availability in wet areas. Moreover, in summer, availability was virtually zero in all habitats, whereas consumption averaged 15% volume of the diet. We tentatively suggest that badgers compensate for variations in earthworm availability by changing their foraging tactics. This suggests that badgers could be viewed as specialist foragers for earthworms in some Mediterranean environments.

Soil structure and characteristics of organic matter in two orchards differing in earthworm activity

By consuming plant remains and soil, earthworms incorporate organic matter (OM) into the soil and form biogenic soil structures, which can affect OM dynamics. We carried out a (micro)morphological study of soil structure development and OM distribution in two orchards (45 year) in a Dutch calcareous marine loam: RI − without, and KR + with high earthworm activity, the result of different levels of heavy metal contamination from fungicides. In both soils, sedimentary–stratification was absent to 60 cm depth and equal amounts of biogenic calcite spheroids were counted, suggesting similar earthworm activity in the past. In RI − the current vol.% of worm-worked groundmass in thin sections was 6% in the Ah and 7% in the Bw horizon compared with 51% in the Ah and 16% in the Bw horizon of KR +. Disappearance of earthworms with time in RI − gave rise to a compacted physicogenic soil structure with angular and prismatic aggregates and the absence of earthworm biopores. Due to restricted fragmentation and incorporation of OM fragments in casts, a litter layer formed at the soil surface. OM coatings were present in fissures and root pores of the Ah horizon, indicating the absence of mixing of organic and mineral soil materials. OM fragments were relatively coarse (>50 μm) and heterogeneously distributed through the Ah groundmass. Stronger decalcification in RI − than in KR + could be ascribed to higher production of organic acids in the litter layer of RI − and the absence of soil homogenisation by earthworms. In KR + earthworm activity was high, which has resulted in a biogenic structure with granular and subangular blocky aggregates and many worm casts and biopores. Particulate OM was relatively fine (<50 μm) and encapsulated with clayey material in casts and micro-aggregates. The organic C content was not significantly ( P<0.05) higher in the Ah horizon of KR +, than in the Ah horizon of RI − (15.7 and 13.7 g kg −1, respectively). The lower C mineralization rates in KR + below 6 cm depth, however, might be an indication of higher microbial substrate-use efficiency or physical protection of OM against decomposition. The latter explanation would accord with the observed encapsulation of OM in micro-aggregates, and with studies on other management systems that favour biogenic aggregate formation. The quality of the soil macro- and microstructures, degree of soil compaction and decalcification and soil OM dynamics were strongly determined by the occurrence of earthworms in soils.

Soil meso- and macrofauna in two agricultural systems: factors affecting population dynamics and evaluation of their role in carbon and nitrogen dynamics

Data on soil meso- and macrofauna from winter wheat fields in the Netherlands under conventional and integrated management were analysed to explain their population dynamics and to evaluate their contribution to carbon and nitrogen dynamics. To compare the functioning of the soil fauna in both systems, respiration and mineralisation were calculated on a daily basis, and canonical correspondence analysis was used to analyse the response of soil fauna to abiotic factors and to biotic factors of the previous sample date.Mainly because of the occurrence of earthworms, which were absent in the conventional system, soil fauna was clearly more important in the integrated system: integrated/conventional ratios of biomass and respiration were 58.43 and 6.49, respectively for soil meso- and macrofauna. An indication of a shift of bacterivorous to fungivorous fauna was found in the integrated system under the assumption that earthworms were 80% microbivorous and 20% saprophagous, but bot when it was assumed that they were 100% saprophagous.It was calculated that meso- and macrofauna mineralised 3.3 kg N ha−1 year−1 in the conventional and 39.8 kg N ha−1 year−1 in the integrated system, or 4.3% and 39.4% of the total in situ mineralisation, respectively. Total faunal mineralisation was 49.1% and 86.6% of the total in situ mineralisation in conventional and integrated systems, respectively.It was found that in both systems, seasonal factors played an important role in explaining biomass dynamics and that in the course of time, the upper layer in the integrated system increased in importance. It appeared from the analyses that food relations may differ in the two systems, with probably more complicated and diverse relations occurring in the integrated system.Analysis of the results of this study in comparison with the results of a food web approach showed general agreement; the largest deviations occurred on lower trophic levels, which may be associated with the greater sensitivity of the food web approach to the accuracy of parameter estimates.

Vorkommen von Regenwürmern in landwirtschaftlich rekultivierten Flächen in der Niederrheinischen Bucht

Abstract Earthworm occurrence in agricultural reclamation areas of the Lower Rhine Basin Until late 1990 the lignite mining industry utilized agricultural land covering 16,051 hectares in the Lower Rhine Basin, 6,926 hectares of which was meanwhile reclaimed for its former use. The yield potential of these reclaimed soils depends to a very large extent on their water holding capacity and rootability.Since the soil structure is completely destroyed during material removal and compacted as a result of the construction process, particular importance is attached to the activities of earthworms in these young soils because these animals can reduce the effects of such damage. In the fall of 1989 and the spring of 1990 different sites (36) were selected to examine the influence of the reclamation year, method and quality, and of cultivation on the abundance of earthworms. The animals were expelled by means of diluted formalin solution. Species and genus of these animals were determined.The population of earthworms increases with area age. It is smaller on young and middle‐aged flushed areas than on those of the same age, but constructed according to the dry dumping method. The plots cultivated without ploughing for three years had a considerably greater earthworm population compared to other areas. It was not possible to demonstrate any influence of the reclamation quality on the abundance of earthworms; the addition of organic substances, however, had a positive effect.Stable manure (turkey hen manure) was more efficient than green manure and straw chaff. Thus, cultivation promoting earthworm development can also produce a relatively high earthworm population density in reclaimed soils which in turn is of major importance for biogenic loosening‐up (stabilization of the soil structure).