Do earthworms (D. veneta) influence plant-available water in technogenic soil-like substrate from bricks and compost?
Ulrich, Susanne ; Willaredt, Moreen ; Nehls, Thomas ; Schaik, Loes van - \ 2020
Journal of Soils and Sediments (2020). - ISSN 1439-0108
Brick-compost mixture - Earthworms - Microcosms - Soil-like substrate - Technosol - Water retention
Purpose: Topsoil and peat are often taken from intact rural ecosystems to supply the urban demand for fertile soils and soil-like substrates. One way of reducing this exploitation is to recycle suitable urban wastes to produce Technosols and technogenic soil-like substrates. In this study, we investigate the role earthworms can play in impacting the hydraulic properties of such a soil-like substrate. Materials and methods: In a 4-month microcosm experiment, the influence of the earthworm species D. veneta on the hydraulic properties of brick-compost mixture was examined. Of the ten boxes filled with ca. 11 dm3 of ground bricks (0.7 cm3 cm−3) and green waste compost (0.3 cm3 cm−3), five contained earthworms (W-boxes) and the remaining five were used as controls (C-boxes). The substrate was periodically irrigated and the weight of the boxes and of the drained water was monitored. At the same time, images were taken from the front of the boxes to quantify the activity of the earthworms by image analysis and soil aggregation was studied with micrographs. Before and after the experiment, water retention curves were determined from disturbed samples of the substrate using the simplified evaporation method. Results and discussion: After 6 weeks, differences between the C- and the W-boxes were evident. Micrographs showed brick-compost aggregates only for the substrates processed by earthworms. The earthworm activity leads to reduced evaporation and an increased water content in the respective microcosms. The effect persists even after disturbing the substrate. The proportion of plant-available soil water is about 0.02 cm3 cm−3 higher for the substrate processed by earthworms (0.250 ± 0.009 cm3 cm−3) compared with the control (0.230 ± 0.008 cm3 cm−3). Conclusions: This study shows that earthworms are capable of ingesting and processing crushed bricks together with compost. The earthworms produced aggregates which persisted after disturbance and had a positive influence on the water retention capacity of such a soil-like substrate constructed from waste.
Large variations in readily-available phosphorus in casts of eight earthworm species are linked to cast properties
Vos, Hannah M.J. ; Koopmans, Gerwin F. ; Beezemer, Lieke ; Goede, Ron G.M. de; Hiemstra, Tjisse ; Groenigen, Jan Willem van - \ 2019
Soil Biology and Biochemistry 138 (2019). - ISSN 0038-0717
Community composition - Earthworms - Phosphorus - Physico-chemical cast properties
Phosphorus (P) is an important nutrient for plant growth. However, P is often poorly available for uptake by roots because it strongly adsorbs to the soil mineral phase. Recent research shows that earthworms can temporally and locally increase P availability to plants. However, the pathways through which they do so are not fully understood, and it remains unclear to what extent this capacity varies among earthworm species. Here we study the variation among earthworm species with respect to readily-available P in casts as well as other physico-chemical cast properties, in a greenhouse pot experiment using a soil with a low P status. The earthworms belong to eight commonly occurring earthworm species in the Netherlands: two epigeic species (a mixture of the compost earthworms Dendrobaena veneta/Eisenia fetida; Lumbricus rubellus); four endogeic species (Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea rosea, Octolasion lacteum); and two anecic species (Aporrectodea longa; Lumbricus terrestris). For all species, the pH in water extracts of earthworm cast (pH = 7.4–8.2) was significantly higher (p < 0.001) than for the control bulk soil (pH = 6.6) and differed significantly (p = 0.003) among earthworm species. Similarly, the dissolved organic carbon (DOC) concentration in the same water extracts was an order of magnitude higher in earthworm cast compared to the control bulk soil and varied among species (p < 0.001). The size of the total pool of reversibly adsorbed P in earthworm cast was greater than in the control bulk soil, but no significant differences were found among earthworm species. Differences among species were present for the readily-available P pools extracted from casts, including P-Olsen and water-extractable ortho-P. Water-extractable ortho-P concentrations were much higher in the casts of all species as compared to the control bulk soil (0.9–6.8 vs 0.06 mg l−1 or to 9.0–68 vs 0.6 mg kg−1). Highest ortho-P levels were measured in L. rubellus casts and the lowest in casts of A. chlorotica. A positive correlation between the concentrations of DOC and ortho-P was observed (R2 = 0.72, p < 0.001). The observed variation in all measured physico-chemical cast properties could not be explained by conventional ecological earthworm classifications. Our results show that the nature and magnitude of earthworm-induced increased P availability differs dramatically among earthworm species. This strongly suggests that, apart from its size, species composition of the earthworm community is key to optimizing P availability to plants.
Improved Pastures Support Early Indicators of Soil Restoration in Low-input Agroecosystems of Nicaragua
Webster, Emily ; Gaudin, Amélie C.M. ; Pulleman, Mirjam ; Siles, Pablo ; Fonte, Steven J. - \ 2019
Environmental Management 64 (2019)2. - ISSN 0364-152X - p. 201 - 212.
Brachiaria brizantha - Earthworms - Pasture degradation - Permanganate oxidizable carbon - Silvopastoral systems - Soil health
Pasture degradation hinders livestock production and ecosystem services that support rural smallholder communities throughout Latin America. Silvopastoral systems, with improved pasture cultivars (especially Brachiaria spp.) and multipurpose trees, offer a promising strategy to restore soils and improve livelihoods in the region. However, studies evaluating the impact of such systems on pasture productivity and soil health under realistic smallholder constraints are lacking. We evaluated the impact of improved pasture grass and tree establishment on a suite of soil health indicators in actively grazed, low-input, farmer-managed silvopastoral systems. In August 2013, paired pasture treatments (improved grass with trees vs. traditional pastures) were established on nine farms with similar land-use histories near Matagalpa, Nicaragua. On each farm, one treatment was left as traditional pasture with naturalized grass (Hyparrhenia rufa), while the adjacent treatment was sown with the improved grass (Brachiaria brizantha cv. Marandu) and planted with tree saplings without fertilizer. In August 2015, we measured standing biomass and a suite of chemical, biological, and physical soil health variables. Improved silvopastoral systems with B. brizantha produced more standing grass biomass and supported higher levels of earthworm populations and permanganate oxidizable carbon (POXC) compared to the traditional control. Correlations suggest that earthworms and POXC were associated with incipient improvements to soil aggregate stability and water holding capacity. We report measurable improvements to soil health just two years following the establishment of improved pasture systems under common smallholder management practices and suggest that these systems, even with minimal fertility inputs, have the potential to enhance regional sustainability.
Bioturbation of Ag2S-NPs in soil columns by earthworms
Baccaro, Marta ; Harrison, Samuel ; Berg, Hans van den; Sloot, Laura ; Hermans, Davy ; Cornelis, Geert ; Gestel, Cornelis A.M. van; Brink, Nico W. van den - \ 2019
Environmental Pollution 252 (2019). - ISSN 0269-7491 - p. 155 - 162.
Bioturbation - Earthworms - Nanoparticles - Soil - Transport
Sewage sludge contains Ag2S-NPs causing NP exposure of soil fauna when sludge is applied as soil amendment. Earthworm bioturbation is an important process affecting many soil functions. Bioturbation may be affected by the presence of Ag2S-NPs, but the earthworm activity itself may also influence the displacement of these NPs that otherwise show little transport in the soil. The aim of this study was to determine effects of Ag2S-NPs on earthworm bioturbation and effect of this bioturbation on the vertical distribution of Ag2S-NPs. Columns (12 cm) of a sandy loamy soil with and without Lumbricus rubellus were prepared with and without 10 mg Ag kg−1, applied as Ag2S-NPs in the top 2 cm of the soil, while artificial rainwater was applied at ∼1.2 mm day−1. The soil columns were sampled at three depths weekly for 28 days and leachate collected from the bottom. Total Ag measurements showed more displacement of Ag to deeper soil layers in the columns with earthworms. The application of rain only did not significantly affect Ag transport in the soil. No Ag was detected in column leachates. X-ray tomography showed that changes in macro porosity and pore size distribution as a result of bioturbation were not different between columns with and without Ag2S-NPs. Earthworm activity was therefore not affected by Ag2S-NPs at the used exposure concentration. Ag concentrations along the columns and the earthworm density allowed the calculation of the bioturbation rate. The effect on the Ag transport in the soil shows that earthworm burrowing activity is a relevant process that must be taken into account when studying the fate of nanoparticles in soils. Earthworm bioturbation plays a more important role than rainfall in the vertical transport of Ag2S-NPs in soil.
The impact of cattle dung pats on earthworm distribution in grazed pastures
Bacher, M.G. ; Fenton, O. ; Bondi, G. ; Creamer, R.E. ; Karmarkar, M. ; Schmidt, O. - \ 2018
BMC Ecology 18 (2018)1. - ISSN 1472-6785
Earthworms - Grassland - Lumbricidae - Population aggregation - Populations - Sampling - Soil biodiversity - Soil fauna - Spatial distribution
Background: Grazed grassland management regimes can have various effects on soil fauna. For example, effects on earthworms can be negative through compaction induced by grazing animals, or positive mediated by increases in sward productivity and cattle dung pats providing a food source. Knowledge gaps exist in relation to the behaviour of different earthworm species i.e. their movement towards and aggregation under dung pats, the legacy effects of pats and the spatial area of recruitment. The present study addressed these knowledge gaps in field experiments, over 2 years, using natural and simulated dung pats on two permanent, intensively grazed pastures in Ireland. Results: Dung pats strongly affected spatial earthworm distribution, with up to four times more earthworms aggregating beneath pats, than in the control locations away from pats. In these earthworm communities comprising 11 species, temporally different aggregation and dispersal patterns were observed, including absence of individual species from control locations, but no clear successional responses. Epigeic species in general, but also certain species of the anecic and endogeic groups were aggregating under dung. Sampling after complete dung pat disappearance (27 weeks after application) suggested an absence of a dung pat legacy effect on earthworm communities. Based on species distributions, the maximum size of the recruitment area from which earthworms moved to pats was estimated to be 3.8 m2 per dung pat. Since actual grazing over 6 weeks would result in the deposition of about 300 dung pats per ha, it is estimated that a surface area of 1140 m2 or about 11% of the total grazing area can be influenced by dung pats in a given grazing period. Conclusions: This study showed that the presence of dung pats in pastures creates temporary hot spots in spatial earthworm species distribution, which changes over time. The findings highlight the importance of considering dung pats, temporally and spatially, when sampling earthworms in grazed pastures. Published comparisons of grazed and cut grasslands probably reached incorrect conclusions by ignoring or deliberately avoiding dung pats. Furthermore, the observed intense aggregation of earthworms beneath dung pats suggests that earthworm functions need to be assessed separately at these hot spots.
Applying soil health indicators to encourage sustainable soil use : The transition from scientific study to practical application
Griffiths, Bryan S. ; Faber, Jack ; Bloem, Jaap - \ 2018
Sustainability 10 (2018)9. - ISSN 2071-1050
Earthworms - Ecosystem services - Monitoring - Soil food web - Water infiltration
The sustainable management of land for agricultural production has at its core a healthy soil, because this reduces the quantity of external inputs, reduces losses of nutrients to the environment, maximises the number of days when the soil can be worked, and has a pore structure that maximises both the retention of water in dry weather and drainage of water in wet weather. Soil health encompasses the physical, chemical, and biological features, but the use of biological indicators is the least well advanced. Sustainability also implies the balanced provision of ecosystem services, which can be more difficult to measure than single indicators. We describe how the key components of the soil food web contribute to a healthy soil and give an overview of the increasing number of scientific studies that have examined the use of biological indicators. A case study is made of the ecosystem service of water infiltration, which is quite an undertaking to measure directly, but which can be inferred from earthworm abundance and biodiversity which is relatively easy to measure. This highlights the difficulty of putting any monitoring scheme into practice and we finish by providing the considerations in starting a new soil health monitoring service in the UK and in maintaining biological monitoring in The Netherlands.
Responses of soil biota to non-inversion tillage and organic amendments : An analysis on European multiyear field experiments
Hose, Tommy D'; Molendijk, Leendert ; Vooren, Laura Van; Berg, Wim van den; Hoek, Hans ; Runia, Willemien ; Evert, Frits van; Berge, Hein ten; Spiegel, Heide ; Sandèn, Taru ; Grignani, Carlo ; Ruysschaert, Greet - \ 2018
Pedobiologia 66 (2018). - ISSN 0031-4056 - p. 18 - 28.
Earthworms - Microbial biomass - Multiyear field experiments - Nematodes - Non-inversion tillage - Organic amendments
Over the last two decades, there has been growing interest on the effects of agricultural practices on soil biology in Europe. As soil biota are known to fluctuate throughout the season and as agro-environmental conditions may influence the effect of agricultural practices on soil organisms, conclusions cannot be drawn from a single study. Therefore, integrating the results of many studies in order to identify general trends is required. The main objective of this study was to investigate how soil biota are affected by repeated applications of organic amendments (i.e. compost, farmyard manure and slurry) or reduced tillage (i.e. non-inversion tillage and no till) under European conditions, as measured in multiyear field experiments. Moreover, we investigated to what extent the effects on soil biota are controlled by soil texture, sampling depth, climate and duration of agricultural practice. Experimental data on earthworm and nematode abundance, microbial biomass carbon and bacterial and fungal communities from more than 60 European multiyear field experiments, comprising different climatic zones and soil texture classes, were extracted from literature. From our survey, we can conclude that adopting no tillage or non-inversion tillage practices and increasing organic matter inputs by organic fertilization were accompanied by larger earthworm numbers (an increase between 56 and 125% and between 63 and 151% for tillage and organic amendments, respectively) and biomass (an increase between 108 and 416% and between 66 and 196% for tillage and organic amendments, respectively), a higher microbial biomass carbon content (an increase between 10 and 30% and between 25 and 31% for tillage and organic amendments, respectively), a marked increase in bacterivorous nematodes (an increase between 19 and 282% for organic amendment) and bacterial phospholipid-derived fatty acids (PLFA; an increase between 31 and 38% for organic amendment). Results were rarely influenced by soil texture, climate and duration of practice.
Exploring the pathways of earthworm-induced phosphorus availability
Ros, Mart B.H. ; Hiemstra, Tjisse ; Groenigen, Jan Willem van; Chareesri, Anupol ; Koopmans, Gerwin F. - \ 2017
Geoderma 303 (2017). - ISSN 0016-7061 - p. 99 - 109.
Earthworms - pH - Phosphorus - Plant growth - Surface complexation modelling
As many soils are unable to supply sufficient amounts of phosphorus (P) to plants, P availability is often a growth-limiting factor. Literature shows that levels of readily available P can be considerably higher in earthworm casts than in the surrounding bulk soil, possibly resulting in increased plant P uptake. However, the underlying mechanisms through which this increase of readily available P occurs are unclear. In a greenhouse pot experiment with annual ryegrass (Lolium multiflorum) on a soil with low P availability, we tested whether the presence of the anecic earthworm Lumbricus terrestris resulted in increased grass growth and P uptake and explored the possible mechanisms behind such an effect. During the pot experiment, earthworm casts were collected and analysed for water-extractable P as well as for most other relevant ions. The earthworm's presence significantly increased grass yield from 9.80 to 10.80 g dry matter per pot (p = 0.044) and P uptake from 6.32 to 8.04 mg per pot (p = 0.002). Due to increased microbial activity, the solution chemistry in the water extracts of the casts was dramatically changed compared to the bulk soil samples. The concentrations of dissolved inorganic P in cast were enhanced by a factor ~ 30–1000 compared to the levels found in bulk soil. The pH in earthworm casts increased from 5.9 to values between 7.4 and 9.0 and the Ca concentrations decreased by about a factor ~ 2-3 compared to bulk soil samples. In addition, there was an increase in dissolved organic carbon (35 mg L− 1 in casts versus 3 mg L− 1 in soil). Surface complexation modelling, using the Charge Distribution model, suggests that, besides an increase in pH, particularly an enhanced interaction of dissolved organic matter with reactive surface of metal (hydr)oxides is likely to be a major driving force for the augmented release of orthophosphate (PO4) via competitive adsorption and desorption. This competition for adsorption sites is an alternative pathway, next to mineralisation of organic matter, through which earthworms can increase soil fertility.
Potential effects of tillage and field borders on within-field spatial distribution patterns of earthworms
Schaik, Loes Van; Palm, Juliane ; Klaus, Julian ; Zehe, Erwin ; Schröder, Boris - \ 2016
Agriculture, Ecosystems and Environment 228 (2016). - ISSN 0167-8809 - p. 82 - 90.
Agricultural fields - Autocorrelation - Earthworms - Soil tillage - Spatial distribution
Earthworms play a key role in regulating soil ecosystem functions and services. The small scale variability in earthworm abundance is often found to be very high, which is a problem for representative sampling of earthworm abundance at larger scales. In agricultural fields, soil tillage may influence both the average earthworm abundance as well as the spatial distribution of earthworms. Therefore we studied the abundance and spatial pattern of the different ecological earthworm types, i.e. endogeic, epigeic and anecic earthworms, in four agricultural fields differing in soil tillage (two fields with regular tillage and two fields with conservation tillage) and surrounding land use (other cropped fields or apple orchard and forest). To this aim we sampled earthworms on a total number of 430 plots (50 × 50 cm2) using a combination of extraction with mustard solution and hand sorting. The results exhibit large differences in average earthworm abundance between the four fields. Only one of the two fields with conservation tillage had a comparatively very high overall abundance of earthworms. Furthermore, we found a high spatial variability of earthworms within the field scale often exhibiting a patchy distribution. We detected a trend of decreasing earthworm abundances from the field border into the field for different earthworm groups on each of the fields. In three fields with low total earthworm abundance (and only very few epigeic earthworms) there was a short scale autocorrelation with ranges varying strongly for the endogeic earthworms (37.9 m, 62.6 m, and 85.2 m) compared to anecic earthworms (19.8 m, 22.8 m, and 27.4 m). In the field with high abundance, after trend removal, the variogram models for anecic and endogeic earthworms were rejected based on their negative explained variances. On this field, we found only a short scale autocorrelation for the epigeic earthworms with a range of 143 m.Based on these results it seems that ploughing alone cannot explain the differences in abundance and range of autocorrelation found on the four fields. The trend of strongly decreasing earthworm abundance from the field border into the field in the one field with high abundance does indicate that the field border or surrounding land use may also influence the recolonization of fields, but more research is required to provide further evidence for this hypothesis. Due to the very different patterns of earthworm distributions in the fields it remains difficult to recommend an optimal number and distance of samples to obtain a representative earthworm abundance for the field scale.
Vermicomposting as a technology for reducing nitrogen losses and greenhouse gas emissions from small-scale composting
Nigussie, Abebe ; Kuijper, Thomas ; Bruun, Sander ; Neergaard, Andreas de - \ 2016
Journal of Cleaner Production 139 (2016). - ISSN 0959-6526 - p. 429 - 439.
Earthworms - Substrate quality - Thermophilic composting - Vermicomposting
Thermophilic composting produces a significant amount of greenhouse gases. The objectives of this study were (i) to evaluate the effectiveness of vermicomposting to reduce nitrogen losses and greenhouse gases emissions compared to thermophilic composting, and (ii) to determine the effect of different variables (i.e. carbon:nitrogen ratio, earthworm density, moisture content and carbon quality) on greenhouse gases emissions and earthworm growth during vermicomposting. The results showed that vermicomposting significantly reduced nitrogen loss by 10–20% compared to thermophilic composting. Vermicomposting decreased nitrous oxide emissions by 25–36% and methane emissions by 22–26%. A higher earthworm density increased carbon dioxide emissions by 3–14%, but decreased methane emissions by 10–35%. Earthworm density had a marginal effect on nitrous oxide emissions. Vermicomposting decreased nitrous oxide emissions by 40% with higher moisture and by 23% with lower moisture. Vermicomposting also decreased methane emissions by 32% and 16% with higher and lower moistures respectively. This study showed that the addition of labile carbon sources increased carbon dioxide and methane emissions and earthworm growth, but did not affect nitrous oxide emissions. In conclusion, vermicomposting is effective at reducing nitrogen losses and greenhouse gas emissions from composting. Therefore, vermicomposting could represent an option for reducing greenhouse gas emissions from composting, particularly in developing countries where the existing technical solutions are expensive and difficult to implement.
Integrating soil physical and biological properties in contrasting tillage systems in organic and conventional farming
Crittenden, S.J. ; Goede, R.G.M. de - \ 2016
European Journal of Soil Biology 77 (2016). - ISSN 1164-5563 - p. 26 - 33.
Earthworms - Non-inversion tillage - Organic agriculture - Soil physical quality - Structural equation modelling
Though soil physical and soil biological properties are intrinsically linked in the soil environment they are often studied separately. This work adds value to analyses of soil biophysical quality of tillage systems under organic and conventional farming systems by correlating physical and biological data otherwise left unexplored. Multivariate redundancy analysis was used to relate data on soil water, soil structure, soil carbon, crop yield, and earthworm species abundances (Aporrectodea caliginosa, Aporrectodea rosea, Eiseniella tetraedra, Lumbricus rubellus). Structural equation modelling was then used to infer causal relations amongst the variables. Effects of tillage system (i.e., mouldboard ploughing (MP) and non-inversion tillage (NIT)) on soil physical parameters and on the earthworm species Lumbricus rubellus were similar in organic and conventional farming. Despite sampling times in different seasons and different crops present at the time of sampling NIT correlated positively with L. rubellus, soil organic matter content, plant-available water content, soil aggregate stability, soil water content, and penetration resistance. Field-saturated hydraulic conductivity was negatively correlated with NIT and was negatively, or not correlated at all, with earthworm species abundances, possibly due to the absence of Lumbricus terrestris in these fields. In the comparison of organic fields, earthworms were positively correlated with the soil's ability to hold water but loosening by ploughing appears to have benefited the conduction of water through soil more than earthworms. Tillage systems and farming systems were found to have both direct and indirect influences on soil parameters. Organic farming increased soil organic matter content, soil water content, and both endogeic and epigeic earthworm species abundances. Non-inversion tillage increased crop yield, soil organic matter content, and soil penetration resistance. This study demonstrates that multivariate techniques can integrate and add value to data otherwise analysed separately.
Modelling distribution patterns of anecic, epigeic and endogeic earthworms at catchment-scale in agro-ecosystems
Palm, Juliane ; Schaik, N.L.M.B. van; Schröder, Boris - \ 2013
Pedobiologia 56 (2013)1. - ISSN 0031-4056 - p. 23 - 31.
Biotic interactions - Boosted regression trees (BRT) - Distribution patterns - Earthworms - Soil hydrology - Species distribution models
Species distribution models are useful for identifying driving environmental factors that determine earthworm distributions as well as for predicting earthworm distribution patterns and abundances at different scales. However, due to large efforts in data acquisition, studies on larger scales are rare and often focus on single species or earthworms in general. In this study, we use boosted regression tree models (BRTs) for predicting the distribution of the three functional earthworm types, i.e. anecics, endogeics and epigeics, in an agricultural area in Baden-Württemberg (Southwest Germany).First, we predicted presence and absence and later earthworm abundances, considering predictors depicting land management, topography, and soil conditions as well as biotic interaction by using the abundance of the other functional earthworm types. The final presence-absence models performed reasonably well, with explained deviances between 24 and 51% after crossvalidation. Models for abundances of anecics and endogeics were less successful, since the high small-scale variability and patchiness in earthworm abundance influenced the representativeness of the field measurements. This resulted in a significant model uncertainty, which is practically very difficult to overcome with earthworm sampling campaigns at the catchment scale.Results showed that management practices (i.e. disturbances), topography, soil conditions, and biotic interactions with other earthworm groups are the most relevant predictors for spatial distribution (incidence) patterns of all three functional groups. The response curves and contributions of predictors differ for the three functional earthworm types. Epigeics are also controlled by topographic features, endogeics by soil parameters.
The effects of earthworms, botanical diversity and fertiliser type on the vertical distribution of soil nutrients and plant nutrient acquisition : A mesocosm study
Massey, P.A. ; Creamer, R.E. ; Schulte, R.P.O. ; Whelan, M.J. ; Ritz, K. - \ 2013
Biology and Fertility of Soils 49 (2013)8. - ISSN 0178-2762 - p. 1189 - 1201.
Botanical diversity - Earthworms - Mesocosm - Nutrient distribution - Phosphorus distribution
The application of phosphorus (P)-based fertiliser to agricultural soils can result in a skewed vertical distribution of P down the soil profile, since the element tends to accumulate at the soil surface. Such accumulation can have detrimental effects on the environment, as the erosion of surface soil can facilitate the transfer of large quantities of P out of the field into water bodies. Earthworm and plant communities are intricately linked to vertical nutrient distributions in soil, with both communities either facilitating or negating the incorporation of nutrients into the soil matrix. This study aimed to investigate the effect of earthworm presence, plant community structure and fertiliser type to affect the distribution of nutrients in experimental mesocosms; with particular emphasis on the vertical distribution of P. Mesocosms were designed to simulate a soil which has a high P concentration at the surface compared to further down the soil profile. It was hypothesised that the presence of earthworms would facilitate the incorporation of P into the soil matrix and the presence of a more botanically diversity community would assimilate a greater quantity of soil nutrients. After 1 year, mesocosms were deconstructed into five depth ranges, and the distribution of nutrients were modelled and analysed. Results indicated that the presence of earthworms did redistribute soil nutrients from the surface into the matrix beneath. This redistribution was apparent from a reduction in nutrient concentrations in the 0-1 cm depth range. The presence of a more botanically diverse community not only assimilated greater soil nutrient concentrations, but also promoted a less even vertical distribution of soil nutrients, demonstrating the importance of soil biota and plant diversity in the redistribution of soil nutrients.
A critical review of current methods in earthworm ecology : From individuals to populations
Bartlett, Mark D. ; Briones, Maria J.I. ; Neilson, Roy ; Schmidt, Olaf ; Spurgeon, David ; Creamer, Rachel E. - \ 2010
European Journal of Soil Biology 46 (2010)2. - ISSN 1164-5563 - p. 67 - 73.
Biogeochemical cycling - Earthworms - Ecotoxicology - Lumbricidae - Molecular techniques - Sampling - Stable isotopes
Earthworms play an important role in the functioning of many terrestrial ecosystems, and while their importance is frequently acknowledged significant challenges still remain in determining their operant roles within the soil. This lack of knowledge becomes increasingly important as the spatial scale of analysis increases from individuals to populations within the landscape. To effectively develop understanding, research techniques must be able to determine the effects that earthworms have on the soil system, as well as to establish how many and which species are present. A range of techniques are required to facilitate meaningful analysis from the micro-scale within a soil profile (e.g. drilosphere effects) to a field scale or landscape scale. Furthermore, an additional framework of understanding is required to investigate the role of earthworms in the biogeochemical cycles. By critically evaluating recent advances in methods and data analysis techniques in three areas of earthworm research we highlight that combinations of common approaches often offer the most significant insights into the functional roles of earthworms within a soil system. Through particular reference to earthworm sampling and identification, biochemical functions and persistent pollutant ecotoxicology of temperate ecosystems we emphasise how a range of investigation methods can be a hindrance to developing a whole-system level understanding. The complex and diverse nature of soil systems means that a traditional compartmentalised approach studying single species using a single research technique is no longer sufficient to gain further insights into the earthworm contribution to ecosystem goods and services delivered at the whole landscape scale. The integration of technologically advanced methods in combination with systems based modelling will be critical to develop landscape scale understanding of the functions of earthworms as individuals and as populations within in their ecosystems.