Growth,reproduction and litter and soil consumption by Lumbricus terrestris L. in reclaimed peat

Ninety-one percent of Salix aquatica cv. gigantea litter disappeared within 6 months from experimental cages containing Lumbricus terrestris L. in reclaimed peat, compared with only 28% when L. terrestris was absent. Litter consumption rate was 6–9 mg dry wt g^?1 fresh wt day^?1 in the field and 10–15 mg g^?1 fresh wt day^?1 in the laboratory at 15°C. Maximum growth rate in the field was 4mg fresh wt g^?day^? and 4.55 mg in the laboratory. Cocoon production in the field was 1.3worm^?1 month^?1 and 2.1 in the laboratory. Mean gut contents were 48-23 mg dry wt g^?1 fresh wt over the size range 1–6 g fresh wt and gut transit time was 10h. It was estimated that a Lumbricus biomass of 100gm^?2 could consume 1.34 kg soil m^?2 yr^?1.     

The earthworm population of a winter cereal field and its effects on soil and nitrogen turnover

The earthworm population in a winter cereal field in Ireland was studied over a 3-year-period and its effects on soil and N turnover were assessed. The mean annual population density was 346–471 individuals m^-2 and the mean biomass was 56.9–61.2 g m^-2. Twelve species were recorded, the most abundant being Allolobophora chlorotica followed by Aporrectodea caliginosa, and 242 mg at 5°C to 713 mg at 10°C in the case of juvenile Lumbricus terrestris. Gut contents (dry mass of soil) comprised 6.7–15.5% of the A. caliginosa live mass, and 9.7–14.7% of the Lumbricus terrestris mass. Annual soil egestion by the field population was estimated as 18–22 kg m^-2. Tissue production ranged from 81.7 to 218.5 g m^-2, while N turnover resulting from mortality was calculated as 1.5–3.9 g m^-2 depending on the year and the method of calculation. Earthworms were estimated to contribute an additional 3.4–4.1 g mineral N to the soil through excretion, mucus production, and soil ingestion. Independent estimates of N output via mucus and excretion derived from ¹⁵N laboratory studies with Lumbricus terrestris were 2.9–3.6 g m^-2 year^-1.     

Cast production and NIR spectral signatures of Aporrectodea caliginosa fed soil with different amounts of half-decomposed Populus nigra litter

Sub-adult individuals of Aporrectodea caliginosa were incubated for 16 weeks under laboratory cultures in a soil treated with 0%, 10% or 50% of a Populus nigra half-decomposed leaves, respectively. Growth was maximum in the 50% organic matter treatment and cocoon production occurred. Average soil ingestion rates decreased from 1.56 g/g^?1 fresh weight of worm per day^?1 in control soil to 1.17 and 0.5 g, respectively, in treatments with 10% and 50% half-decomposed litter. Surface casts never comprised more than 10% of total cast production. Near-infrared spectrometry (NIRS)signatures of digested and non-ingested soil significantly differed and showed a rather constant effect of digestion, independent of the organic matter content (p?<?0.01). These results confirm the value of NIRS spectral signatures as indicators of the origin of soil aggregates and biological processes involved in soil aggregation.     

Production and carrying capacity for the earthworm Lumbricus terrestris in culture

Approximately 8 h were required at 25°C for food to pass from mouth to anus in the earthworm Lumbricus terrestris. Gut load per unit transit appeared inversely related to nitrogen content; values of about 2 and 44 mg dry castings per 100mg dry worm were obtained with activated sludge and mineral soil, respectively. Production of biomass was greater in a substrate of activated sludge and loam relative to activated sludge and cellulose, despite higher concentrations of nitrogen in the latter. Optimum population density was about 8 earthworms (31 g live wt) in 1000cm³ 2:1 sludge:soil. Growth occurred at a maximum rate between 15 and 25°C. A yield of approximately 4% biomass (dry wt) was obtained on a mixture of activated sludge and loam, based on the content of organic matter present.     

Gut load and transit time in Hormogaster elisae (Oligochaeta,Hormogastridae) in laboratory cultures

The gut load and gut transit time (GTT) of the endogeic earthworm Hormogaster elisae in laboratory cultures at 18 °C and 23 ºC were studied. The GTT, 5.25 h ± 0.40 at 18 ºC and 3.63 h ± 0.46 at 23 ºC, was determined by staining the soil with alimentary colouring (tartrazine). The gut load was calculated with two methods: earthworm mass difference, before and after voiding the gut, and dry mass of the gut content. The gut load ranged between 168 and 261 mg wet mass g live earthworm mass^–1 (mass difference method) or 137–196 mg dry mass g live earthworm mass^–1 (dry mass method). With the obtained data a potential annual soil turnover for H. elisae was calculated: 211–470 kg wet soil mass kg live earthworm mass^–1 year^–1 (mass difference method) or 176–325 kg dry soil mass kg live earthworm mass^–1 year^–1 (dry mass method).     

Partitioning of Hg Between Solid and Dissolved Organic Matter in the Humus Layer of Boreal Forests

The mobility of mercury (Hg) deposited on soils controls the concentration and toxicity of Hg within soils and in nearby streams and lakes, but has rarely been quantified under field conditions. We studied the in situ partitioning of Hg in the organic top layer (mor) of podsols at two boreal forest sites differing in Hg deposition and climatic regime (S. and N. Sweden, with pollution declining to the north). Soil solution leaching from the mor layer was repeatedly sampled using zero-tension lysimeters over 2 years, partly in parallel with tension lysimeters. Concentrations of Hg and dissolved organic carbon (DOC) were higher while pH was lower at the southern site (means ± SD: Hg?=?44?±?15 ng L^?1, DOC?=?63.0?±?31.3 mg L^?1, pH?=?4.05?±?0.53) than at the northern site (Hg?=?22?±?6 ng L^?1, DOC?=?41.8?±?12.1 mg L^?1, pH?=?4.28?±?0.43). There was a positive correlation over time between dissolved Hg and DOC at both sites, even though the DOC concentration peaked during autumn at both sites, while the Hg concentration remained more constant. This correlation is consistent with the expected strong association of Hg with organic matter and supports the use of Hg/C ratios in assessments of Hg mobility. In the solid phase of the overlying O_f layer, both Hg concentrations and Hg/C ratios were higher at the southern site (means ± SD: 0.34?±?0.06 μg g^?1 dw and 0.76?±?0.14 μg g^?1 C, respectively) than at the northern site (0.31?±?0.05 μg g^?1 dw and 0.70?±?0.12 μg g^?1 C, respectively). However, concentrations in the solid phase differed less than might be expected from the difference in current atmospheric input, suggesting that the fraction of natural Hg is still substantial. At both sites, Hg/C ratios in the upper half of the mor layer were only about two thirds of those in the lower half, suggesting that the recent decrease in anthropogenic Hg deposition onto the soil is offset by a natural downward enrichment of Hg due to soil decomposition or other processes. Most interestingly, comparison with soil leachate showed that the average Hg/C ratios in the dissolved phase of the mor layers at both sites did not differ from the average Hg/C ratios in the overlying solid organic matter. These results indicate a simple mobilisation with negligible fractionation, despite differences in Hg deposition patterns, soil chemistry and climatic regimes. Such a straight-forward linkage between Hg and organic matter greatly facilitates the parameterisation of watershed models for assessing the biogeochemical fate, toxic effect and critical level of atmospheric Hg input to forest soils.     

Effects of pentachlorophenol on asymbiotic nitrogen fixation in soil

The effect of 50, 100, 150, and 400 μg sodium pentachlorophenate (Na-PCP) per gram soil was studied in nonsterile soil incubated under aerobic and anaerobic conditions, and in sterilized soil inoculated withAzotobacter sp. isolated from the soil. N₂ fixation was determined by acetylene reduction. Pentachlorophenate at a concentration of 50 μg g^?1 had an inhibitory effect in nonsterile soil incubated aerobically while strong inhibition of dinitrogen fixation in nonsterile soil occurred in the presence of 100 μg g^?1 and above. The EC₅₀ values for the inhibition of nitrogenase activity in nonsterile soil incubated aerobically and anaerobically and in sterilized soil inoculated withAzotobacter sp. suspensions were 49.8±1.4 μg Na-PCP g^?1, 186.8±2.8 μg Na-PCP g^?1, and 660.8±29.3 μg Na-PCP g^?1, respectively.     

Precipitation as the most affecting factor on soil–plant environment conditions affects the mycorrhizal spore numbers in three different ecological zones in Turkey

Mycorrhizal symbiosis is the one of the most important relationship between microbiota and plants to sustain plant nutrition in relatively unfavourable conditions. Somehow this relation is threatened by time, therefore, definition of the factors effecting mycorrhizal symbiosis has become essential. The aim of this study was to determine the differences in specific mycorrhizal parameters such as sporulation and soil–plant environment conditions in three different regions of Turkey. During 1996?2002, 53 soil series were selected from natural and agricultural plant communities in three different agro-ecological zones of Turkey: Central Anatolia (CA), the Southeastern Anatolian (SA) project area and the Coast of Mediterranean (CM). The arbuscular mycorrhizal fungus (AMF), spore numbers and mycorrhizal root colonization were related to the annual average precipitation, soil characteristics and host plant identity.

In the CM zone (average annual precipitation of 650?mm), soils found under natural vegetation contained a maximum value of 108?spores?g^?1, with bare soils containing a minimum number of 0.1?spores?g^?1. In the CA zone (330?mm annual average precipitation), the maximum number of spores in the soil samples was 46.5?spores?g^?1 with a minimum of 6.8?spores?g^?1 and in the SA soil samples (380?mm annual average precipitation), a maximum of 48.4?spores?g^?1 and a minimum of 14.2?spores?g^?1 were recorded. The overall mean number of mycorrhizal spores g^?1 soil was 15.5?±?14.4, 22.2?±?8.6 and 27.9?±?25.4 for the CA, SA and CM zones, respectively. Mean spore numbers differed in only two of the three zones, with the third zone being intermediate. Precipitation was the most affecting factor on the sporulation of AMF. Also host plant species and certain soil parameters, such as positive correlations with CaCO₃ and N-min and a negative correlation with organic matter, have an influence on sporulation.

The key finding is that the cropping system has a large impact on spore numbers/abundance. Seventeen standing crops as well as bare soil, fallow and natural areas were compared. There are a large number of factors which can affect mycorrhizal development; in the present work, it seems that soil and crop management, and environmental factors (such as precipitation) affect sporulation and root colonization. Covering land surface with mycorrhiza-dependent cover crop, irrigation and less soil till may increase indigenous mycorrhizal spores.     

Introduced earthworm species exhibited unique patterns of seasonal activity and vertical distribution,and <Emphasis Type="Italic">Lumbricus terrestris</Emphasis> burrows remained usable for at least 7 years in hardwood and pine stands

It is difficult to obtain non-destructive information on the seasonal dynamics of earthworms in northern forest soils. To overcome this, we used a Rhizotron facility to compile 7 years of data on the activity of anecic (Lumbricus terrestris) and endogeic (Aporrectodea caliginosa complex) earthworms in two contrasting soil/plant community types. We hypothesized that L. terrestris burrows would be used for longer than a typical L. terrestris lifetime, and that the distribution and activity pattern of the two earthworm species would respond differently to changes in soil moisture and temperature. For 7 years we recorded earthworm distribution and activity state bi-weekly to a depth of 1.5 m, tracked L. terrestris burrows using images captured annually, and measured soil temperature and moisture. Activity and vertical distribution of earthworms was closely linked to earthworm species and soil temperature in the fall, winter and spring. Lumbricus terrestris typically remained active through the winter, whereas the A. caliginosa complex was more likely to enter an aestivation period. Activity of all earthworms decreased substantially in July and August when soil temperature was at its highest and soil moisture at its lowest for the year. Most L. terrestris burrows were used continuously and moved very little during the 7-year study, likely creating spatiotemporally stable hotspots of soil resources. The different patterns of response of these species to soil temperature and moisture suggests that endogeic earthworms are more likely than anecic earthworms to adjust activity states in response to climate change mediated shifts in soil moisture and temperature.     

Metal soil pollution differentially affects both the behaviour and exposure of <Emphasis Type="Italic">A. caliginosa</Emphasis> and <Emphasis Type="Italic">L. terrestris</Emphasis>: a mesocosm study

The effects on two earthworm species of a gradient of metal contamination in soil collected close to a 50-year-old lead recycling factory were investigated in mesocosms filled with soil sampled at three distances from the factory (10, 30 and 60 m). After 5 weeks of exposure, earthworm litter consumption and weight change were measured. Burrow systems were analysed using X-ray tomography, and water infiltration was measured. No significant differences in earthworm weight or activity were observed between mesocosms filled with soil from 30 and 60 m. In contrast, both earthworm species significantly lost weight and burrowed less in the soil sampled at 10 m. In the cores filled with the soil collected at 10-m distance, Aporrectodea caliginosa avoided the highly contaminated first layer (0–5 cm) and burrowed deeper whereas Lumbricus terrestris burrowed relatively more in this layer. We assume that these different reactions are associated with their ecological types. Epi-anecic earthworms forage litter at the soil surface, whereas endogeic earthworms are geophagous and thus are able to forage deeper. This was further corroborated by the bioaccumulation factors measured for each species: for L. terrestris, BAF values for Pb and Cd only decreased slightly in the 10-m soil correlating with their overall reduced activity. However, BAF values for A. caliginosa were 20-fold lower compared to those observed in soil from 30 and 60 m. These modifications in burrowing behaviour in the 10-m mesocosms resulted in a significant and marked decrease in water infiltration rates but only for L. terrestris.     

Dietary cobalt supplements and the growth and reproduction of the earthworm Eisenia foetida

The effect of adding cobalt, as ⁶⁰Co, to the food source of the earthworm Eisenia foetida was studied. Cobalt was retained with a half-life of 387 ± 43 (SD) days in the worm. After 172 days more cobalt was concentrated in the gut than the body wall. ⁶⁰Co was not transmitted from adults to cocoons. Prolonged studies involving the addition of CoCl₂ (0, 8.2, 16.5 and 82.5 μg Co g^?1) to a food source low in Co indicated that total Co concentrations of 17.6 and 25.9 μg g^?1 resulted in significantly increased maximum weights compared to the control worms which were exposed to 9.4 μg Co g^?1. The highest Co addition (82.5 μg g^?1, total 91.9 μg g^?1) caused no increase in maximum weight over controls, but resulted in a statistically significant lag in early growth compared to that of all other groups. Significantly more cocoons were produced by worms fed 17.6 or 25.9 μg Co g^?1 compared with those fed 9.4 or 91.9 μg Co^?1 Co.     

Assessment of the Hyperaccumulating Lead Capacity of Salvinia minima Using Bioadsorption and Intracellular Accumulation Factors

Salvinia minima has been reported as a cadmium and lead hyperaccumulator being the adsorption and intracellular accumulation the main uptake mechanisms. However, its physicochemical properties, the effect of metal concentration and the presence of organic and inorganic compounds on its hyperaccumulating capacity are still unknown. Furthermore, the specific adsorption and accumulation mechanisms occurring in the plant are not clear yet. Thus, based on a compartmentalization analysis, a bioadsorption (BAF) and an intracellular accumulation factor (IAF) were calculated in order to differentiate and quantify these two mechanisms. The use of kinetic models allowed predicting the specific type of uptake mechanisms involved. Healthy plants were exposed to five lead concentrations ranging from 0.80?±?0.0 to 28.40?±?0.22 mg Pb²⁺l^?1 in batch systems. A synthetic wastewater, amended with propionic acid and magnesium sulfate, and deionized water were used as media. The BAF and IAF contributed to gain an in-depth insight into the hyperaccumulating lead capacity of S. minima. It is clear that such capacity is mainly due to adsorption (BAF 780–1980) most likely due to its exceptional physico-chemical characteristics such as a very high surface area (264 m² g^?1) and a high content of carboxylic groups (0.95 mmol H⁺g^?1 dw). Chemisorption was predicted as the responsible mechanism according to the pseudo-second order adsorption model. Surprisingly, the ability of S. minima to accumulate the metal into the cells (IAF 57–1007) was not inhibited at concentrations as high as 28.40±0.22 mg Pb²⁺l^?1.     

C and N turnover of fermented residues from biogas plants in soil in the presence of three different earthworm species (Lumbricus terrestris,Aporrectodea longa,Aporrectodea caliginosa)

A soil microcosm experiment was performed to assess (1) the C- and N- turnover of residues from biogas plants in soils in the presence of three earthworm species (Lumbricus terrestris, Aporrectodea longa and Aporrectodea caliginosa) and (2) the resulting changes in soil chemical and microbiological properties when using these residues as fertilizer in comparison to conventional slurry. Earthworms were exposed in soils, fertilized with an equivalent amount of 120 kg of NH₄-N ha^?1 from: (1) conventional cattle slurry and (2) a fermented residue derived from cattle slurry, grass (silage) and maize. Additional treatments without slurry and earthworms were used as controls.There was considerable evidence that soils fertilized by fermented slurry comprised fewer amounts of readily available nutrients for microbial C and N turnover. We observed significant stimulation of microbial biomass, basal respiration and nitrification in treatments with conventional slurry, especially in the presence of earthworms. However, the stimulation of microbial activity by manure and earthworms were significantly lower in treatments with fermented slurry. Moreover, the results showed clear interactions between different earthworm species and manures. While the biomass of the anecic species (L. terrestris and A. longa) increased in both slurry treatments, the biomass of A. caliginosa (endogeic) decreased, with a significantly stronger biomass decline in treatments with fermented slurry. The metabolic quotients revealed microbial stress metabolism in fermented slurry treatments, predominantly in treatments with A. caliginosa. We conclude that particularly A. caliginosa and soil microorganisms competed for labile C sources in treatments with fermented slurry. An application of these residues as fertilizer might result in a reduction of microbial activity in agricultural soils and in a decline of endogeic earthworms.     

Effects of Bt-cotton on biological properties of Vertisols in central India

Growing areas under transgenic crops have created a concern over their possible adverse impact on the soil ecosystem. This study evaluated the effect of Bt-cotton based cropping systems on soil microbial and biochemical activities and their functional relationships with active soil carbon pools in Vertisols of central India (Nagpur, Maharastra, during 2012–2013). Culturable groups of soil microflora, enzymatic activities and active pools of soil carbon were measured under different Bt-cotton based cropping systems (e.g. cotton-soybean, cotton-redgram, cotton-wheat, cotton-vegetables and cotton-fallow). Significantly higher counts of soil heterotrophs (5.7–7.9 log cfu g^?1 soil), aerobic N-fixer (3.9–5.4 log cfu g^?1 soil) and P-solubilizer (2.5?3.0 log cfu g^?1 soil) were recorded in Bt-cotton soils. Similarly, soil enzymatic activities, viz. dehydrogenase (16.6–22.67 µg TPF g^?1 h^?1), alkaline phosphatase (240–253 µg PNP g^?1 h^?1) and fluorescein di-acetate hydrolysis (14.6–18.0 µg fluorescein g^?1 h^?1), were significantly higher under Bt-cotton-soybean system than other Bt- and non-Bt-cotton based systems in all crop growth stages. The growth stage-wise order of soil microbiological activities were: boll development > harvest > vegetative stage. Significant correlations were observed between microbiological activities and active carbon pools in the rhizosphere soil. The findings indicated no adverse effect of Bt-cotton on soil biological properties.     

Cropping history and peat amendment-induced changes in strawberry field earthworm abundance and microbial biomass

Common agricultural practices, e.g. soil tillage and organic amendment, may affect field earthworm communities considerably. However, there is little data to show how long the changes persist after a certain action. The effect of peat, commonly used in Finland to improve the horticultural soil structure, on key soil organisms is also largely unknown. Earthworm abundance and microbial biomass were studied in a strawberry field experiment (soil type silty clay) with a history of different crops (strawberry, timothy, caraway, rye, turnip rape, fiddleneck, onion and buckwheat) and peat treatments. Sampling was carried out after three years of perennial cropping of strawberry. Half of the area was peat-amended twice three years apart. The earthworm community consisted mainly of Aporrectodea caliginosa and Lumbricus terrestris. Soil peat amendment almost doubled the number of endogeic A. caliginosa, but had no effect on the anecic L. terrestris. The effect of cropping history on earthworms diminished after three years of strawberry cropping. Only the positive effect of caraway on juvenile Lumbricus spp. was detectable three years after its cropping had been finished. However, some crops had secondary effects on the earthworm distribution without significant influence on their numbers while they were grown, e.g. high numbers of A. caliginosa were recorded from soil with a history of timothy ley. The effect of strawberry cropping was contradictory: six years of continuous strawberry cropping decreased the number of the anecic L. terrestris, but during the last three years on strawberry, the proportion of L. terrestris increased from 6% to 40% in the experimental area with a concomitant great drop in the number of A. caliginosa. The role of different agricultural practices (no tillage, mulching, inter-row grass cover and pesticides) is discussed. The crop-induced changes persisted in the microbial biomass for three years (onion cropping reduced microbial biomass C), but soil amendment had no effect on microbes. The abundance of A. caliginosa was associated with soil organic C, but not with soil microbial biomass.     

Anaerobic ammonium oxidation and denitrification in a paddy soil as affected by temperature,pH, organic carbon,and substrates

Anaerobic ammonium oxidation (anammox process) widely occurs in paddy soil and may substantially contribute to permanent N removal; however, little is known about the factors controlling this process. Here, effects of temperature, pH, organic C, and substrates on potential rate of anammox and the relative contribution of anammox to total N₂ production in a paddy soil were investigated via slurry incubation combined with ¹⁵N tracer technique. Anammox occurred over a temperature range from 5 to 35 °C with an optimum rate at 25 °C (1.7 nmol N g^?1 h^?1) and a pH range from 4.8 to 10.1 with an optimum rate at pH 7.3 (1.7 nmol N g^?1 h^?1). The presence of glucose and acetate (5–100 mg C L^?1) significantly inhibited anammox activities and the ratio of anammox to total N₂ production. The response of potential rates of anammox to ammonium concentrations fitted well with Michaelis-Menten relationship showing a maximum rate (V_max) of 4.4 nmol N g^?1 h^?1 and an affinity constant (K_m) of 6.3 mg NH₄⁺-N L^?1. Whereas, nitrate addition (5–15 mg ¹⁵NO₃^?-N L^?1) significantly inhibited anammox activities and the ratio of anammox to total N₂ production. Our results provide useful information on factors controlling anammox process and its contribution to N loss in the paddy soil.     

Gross N transfer rates in field soils measured by 15N-pool dilution

Abstract

A micro-plot ¹⁵N-tracer experiment was established in three different soils of a long-term soil fertility field experiment. The nutrient-poor loam sand has been subjected to various treatments over the years and this has resulted in different organic C (0.35% – 0.86%), microbial biomass (38.3 – 100.0 µg C _mic g^?1 soil), clay and fine silt contents. Using the ¹⁵N-pool dilution technique, we assessed gross N-transfer rates in the field. Gross N mineralization rates varied strongly among the three plots and ranged between 0.4 and 4.2 µg N g^?1 soil d^?1. Gross nitrification rates were estimated to be between 0 and 2.1 µg N g^?1 soil d^?1. No correlation between gross N mineralization rates and the organic matter content of the soils was established. However, gross nitrate consumption rates increased with increasing soil C content. The ¹⁵N-pool dilution technique was successfully used to measure gross N transfer rates directly in the field.     

Fate of prions in soil: Degradation of recombinant prion in aqueous extracts from soil and casts of two earthworm species

Prions represent the active agent in transmissible spongiform encephalopathy (TSE) diseases and can remain infective to mammals even after prolonged periods in soil. The influence of mesofauna on prion dispersal and degradation in soil, however, remains unknown. In this study the effect of earthworms on the retention/dissemination of TSEs in soil was evaluated using a model recombinant prion protein (recPrP) and aqueous extracts from soil and fresh casts of two earthworm species, Lumbricus terrestris and Aporrectodea caliginosa. Our results showed that earthworm gut-derived enzymes did not enhance the degradation of recPrP in comparison to soil, even though non-prion related proteolytic activity was higher in fresh worm excrements than in soil samples. Complete degradation of recPrP occurred in the aqueous extracts from all samples within up to 6 days at +15 °C. The proteolytic enzymes responsible for degrading recPrP were inhibited by aprotinin and leupeptin and studies in pure cultures suggested these were most probably of soil microbial origin.     

Subsurface earthworm casts can be important soil microsites specifically influencing the growth of grassland plants

Earthworms (Annelida: Oligochaeta) deposit several tons per hectare of casts enriched in nutrients and/or arbuscular mycorrhizal fungi (AMF) and create a spatial and temporal soil heterogeneity that can play a role in structuring plant communities. However, while we begin to understand the role of surface casts, it is still unclear to what extent plants utilize subsurface casts. We conducted a greenhouse experiment using large mesocosms (volume 45 l) to test whether (1) soil microsites consisting of earthworm casts with or without AMF (four Glomus taxa) affect the biomass production of 11 grassland plant species comprising the three functional groups grasses, forbs, and legumes, (2) different ecological groups of earthworms (soil dwellers—Aporrectodea caliginosa vs. vertical burrowers—Lumbricus terrestris) alter potential influences of soil microsites (i.e., four earthworms × two subsurface microsites × two AMF treatments). Soil microsites were artificially inserted in a 25-cm depth, and afterwards, plant species were sown in a regular pattern; the experiment ran for 6 months. Our results show that minute amounts of subsurface casts (0.89 g kg^?1 soil) decreased the shoot and root production of forbs and legumes, but not that of grasses. The presence of earthworms reduced root biomass of grasses only. Our data also suggest that subsurface casts provide microsites from which root AMF colonization can start. Ecological groups of earthworms did not differ in their effects on plant production or AMF distribution. Taken together, these findings suggest that subsurface earthworm casts might play a role in structuring plant communities by specifically affecting the growth of certain functional groups of plants.     

Peat amendment and production of different crop plants affect earthworm populations in field soil

A field experiment was conducted to study the effects of peat amendment and crop production system on earthworms. The experiment was established on a field previously cultivated with oats and with silt as the main soil type. Perennial crops strawberry, timothy and caraway, and annual crops rye, turnip rape, buckwheat, onion and fiddleneck were cultivated with conventional methods. All the crops were grown with and without soil amendment with peat. Earthworms were sampled twice: 4 and 28 months after establishment of the experiment. In the former case part of the experimental plots were soil sampled and hand sorted for estimation of earthworms. In the latter case all experimental plots were sampled and both soil sampling and mustard extraction was carried out. Soil organic carbon and microbial biomass was measured at 14 and 28 months. Peat increased the abundance of juvenile Aporrectodea caliginosa by 74% in three growing seasons, but had no effect on adult numbers. Lumbricus terrestris numbers were not increased by peat treatment. Three season cultivation of caraway favoured both A. caliginosa and L. terrestris. An equal abundance of A. caliginosa was also found in plots cultivated with turnip rape and fiddleneck. Total earthworm and especially A. caliginosa numbers were very small in plastic-mulched strawberry beds. This was mainly attributed to repeated use of the insecticide endosulfan. With the strawberry plots omitted there was a significant correlation between soil microbial N measured at 14 months and juvenile Aporrectodea spp. and Lumbricus spp. numbers measured at 28 months. Adult earthworm numbers were not associated with either soil organic C or microbial biomass.