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1.
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.  相似文献   

2.
Earthworms, which play a key role in biogeochemical processes in soil ecosystems, could be negatively affected by the cultivation of transgenic Bt crops. Studies to date have found few effects of Bt maize on earthworm species. If adverse effects occur, they are likely to be chronic or sub-lethal and expressed over large spatial and temporal scales. Our objective in the present study was to investigate potential effects on earthworm populations in soil cultivated with Bt maize in a large multiple-year field study. We surveyed the earthworm populations in 0.16-ha experimental field plots of two varieties of Cry1Ab Bt maize, one variety of Cry3Bb1 Bt maize, and three non-transgenic control varieties cultivated for four years. Four earthworm species were found in our sample: Aporrectodea caliginosa, Aporrectodea trapezoides, Aporrectodea tuberculata (collectively, the A. caliginosa species complex), and Lumbricus terrestris. We found no significant differences in the biomass of juveniles and adults for all four species between Bt and non-Bt maize varieties. From this and previous studies, we conclude that the effects of Cry1Ab and Cry3Bb1 Bt maize on the A. caliginosa species complex and L. terrestris are small. Nonetheless, general conclusions about the effects of Bt maize on earthworm populations are not warranted due to the small number of species tested. In future laboratory studies, earthworm species should be selected according to their association with a Bt crop and the impact of that species to valued soil ecosystem processes.  相似文献   

3.
Earthworms and arbuscular mycorrhizal fungi (AMF) might interactively impact plant productivity; however, previous studies reported inconsistent results. We set up a three-factorial greenhouse experiment to study the effects of earthworms (Aporrectodea caliginosa Savigny and Lumbricus terrestris L.) and AMF (Glomus intraradices N.C. Schenck & G.S. Sm.) on the performance (productivity and shoot nutrient content) of plant species (Lolium perenne L., Trifolium pratense L. and Plantago lanceolata L.) belonging to the three functional groups grasses, legumes and herbs, respectively. Further, we investigated earthworm performance and plant root mycorrhization as affected by the treatments. Our results accentuate the importance of root derived resources for earthworm performance since earthworm weight (A. caliginosa and L. terrestris) and survival (L. terrestris) were significantly lower in microcosms containing P. lanceolata than in those containing T. pratense. However, earthworm performance was not affected by AMF, and plant root mycorrhization was not modified by earthworms. Although AMF effectively competed with T. pratense for soil N (as indicated by δ15N analysis), AMF enhanced the productivity of T. pratense considerably by improving P availability. Remarkably, we found no evidence for interactive effects of earthworms and AMF on the performance of the plant species studied. This suggests that interactions between earthworms and AMF likely are of minor importance.  相似文献   

4.
Sanborn Field, an agricultural demonstration field at the University of Missouri-Columbia, has over 100 years of cropping histories and management practices implemented at this site. We examined the effect of these cropping systems and management practices on earthworm populations and microbial activity. A field experiment was conducted to characterize and quantify earthworms and to determine the microbial activity in the same selected plots. We sampled 14 plots at the site, six of which were the original plots established in 1888 with the same cropping histories and management, and eight of which had been modified over the years to accommodate changing farmer needs and scientific questions. Earthworms and soil samples were collected in the spring and fall of 1999. Aporrectodea trapezoides, Aporrectodea caliginosa, and Lumbricus terrestris were the dominant species found in this field. Lumbricus terrestris was commonly associated with the no-tillage plot at Sanborn Field. Due partly to soil moisture conditions, most of the species were found and identified during the spring. Microbial activity, as expected, was greatest during the spring. Manure, no-tillage and crop rotations that include legumes had the greatest earthworm abundance and microbial activity. In general, where no fertility treatments were added to soil or where food sources were lacking, earthworm abundance decreased significantly. The abundance of earthworms found in this field reflected the cropping history and management practices used recently and within the last 100 years. In most cases, microbial activity showed similar trends as earthworm density. However, some dynamic microbial transformations, like nitrification, do not always follow the same trend as potential soil quality biotic indicators. Earthworms, along with microbial activity, may serve as useful soil quality indicators in sustained and short-term field trials.  相似文献   

5.
Earthworms have been shown to influence plant growth, survival and fecundity. They can therefore affect plant demography in plant communities changing their composition. A long term mesocosm experiment was set-up to test the effects of an endogeic (Aporrectodea caliginosa) and an anecic (Lumbricus terrestris) earthworm species on assemblages of four species of annuals: one grass (Poa annua), two forbs (Veronica persica and Cerastium glomeratum) and one legume (Trifolium dubium). The number of individuals and the biomass of each species were investigated. A. caliginosa and L. terrestris affected the density of T. dubium at each of the three monitored census dates. The other plant species responded to A. caliginosa and L. terrestris at the second and third generations. The presences of A. caliginosa and L. terrestris reduced the total number of plant individuals from the second to the third generation. At harvest (3rd generation), T. dubium and V. persica had more and larger individuals in the presence of A. caliginosa. When both earthworm species were present, T. dubium had few but larger individuals. Our study confirms that earthworms affect plant demography and plant community structure. Our results also show that accurate prediction of long-term effects of earthworms on plant communities cannot be achieved using results on their short-term effects on plant growth. This is due to the poor understanding of the effects of earthworms on plant resource allocation and demography, and also the possibility that earthworms may exert the opposite effect on the short and long-term availability of nutrients.  相似文献   

6.
Many ecological studies have pointed out maternal effects in plants and shown that plant maternal environment influences germination of their seed and subsequent seedling growth. However, few have tested for maternal effects induced by soil macroorganisms. We tested whether two earthworm species (Aporrectodea caliginosa and Lumbricus terrestris) trigger such maternal effects on seed germination and seedling growth of three plant species (Veronica persica, Poa annua and Cerastium glomeratum). Our results show that, through maternal effects, A. caliginosa enhanced seed germination (V. persica and P. annua) and seedling growth (C. glomeratum and P. annua) while L. terrestris reduced seed germination only in V. persica. In some cases, the increase in germination rates of seeds produced in the presence of earthworms was associated with a reduction of nitrogen content in seeds. These results show that earthworms induce maternal effects in plants and that the size and direction of these effects depend on the combination of plant and earthworm species.  相似文献   

7.
Energy crops are increasingly cultivated in agricultural management systems world-wide. A substitution of food crops (e.g. cereals) by energy crops may generally alter the biological activity and litter decomposition in soil due to their varying structural and chemical composition and subsequently modify soil functioning. A soil microcosm experiment was performed to assess the decomposition and microbial mineralization of different energy crop residues in soil compared to a food crop, with or without earthworms. Residues of the energy crops winter rape (Brassica napus), maize (Zea mays), miscanthus (Miscanthus giganteus) and the food crop oat (Avena sativa) were each provided as food source for a mixed earthworm population, each consisting of one individual of Lumbricus terrestris, Aporrectodea caliginosa, and Octolasion tyrtaeum. After 6 weeks, the rate of litter loss from the soil surface, earthworm biomass, microbial biomass-C and -N, microbial activity, and enzyme activities were determined. The results emphasized, that litter loss and microbial parameters were predominantly promoted by earthworms and were additionally influenced by the varying structural and chemical composition of the different litter. Litter decay by earthworms was highest in N-rich maize litter treatment (C-N ratio 34.8) and lowest in the case of miscanthus litter (C-N ratio 134.4). As a consequence, the microbial biomass and basal respiration in soils with maize litter were higher, relative to other litter types. MBC-MBN ratio in soil increased when earthworms were present, indicating N competition between earthworms and microorganisms. Furthermore, enzyme activities responded in different ways on the varying types of litter and earthworm activity. Enzymes involved in the N-cycle decreased and those involved in the C-cycle tended to increase in the presence of earthworms, when litter with high C-N ratio was provided as a food source. Especially in the miscanthus treatments, less N might remain for enzymatic degradation, indicating that N competition between earthworms and microorganisms may vary between different litter types. Especially, an expansion of miscanthus in agricultural management systems might result in a reduced microbial activity and a higher N deficit for microorganisms in soil.  相似文献   

8.
The vertical distribution and activity of earthworm life stages were studied in an arable field during 0.5 m deep frost. The anecic Lumbricus terrestris L. were below the frost at the bottom of their home burrows (max. depth 1.0 m) and remained there apparently active. Their burrows were open, free of ice and water. The endogeic Aporrectodea caliginosa Sav., mainly small juveniles, were aestivating in the frost layer, which confirms freeze-tolerance in this species. Large A. caliginosa individuals were actively burrowing below the frost down to 1 m depth at soil temperatures close to +1 °C, frost evidently triggering much deeper burrowing than summer droughts. Demonstrating cold-hardiness, viable cocoons of both A. caliginosa and L. terrestris were obtained within a 0-0.25 m layer, frozen for ca. one month prior to sampling. These two common earthworms of boreal soils seem to over-winter in all life stages and remain active below the frost, potentially contributing to the maintenance of subsoil processes during the winter months.  相似文献   

9.
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.  相似文献   

10.
The objective of this study was to determine the impact of earthworm bioturbation on the distribution and availability of zinc in the soil profile.Experiments were carried out with Allolobophora chlorotica and Aporrectodea caliginosa in 24 perspex columns (∅ 10 cm), filled with 20-23 cm non-polluted soil (OM 2%, clay 2.9%, pH 0.01 M CaCl2 6.4), that was covered by a 3-5 cm layer of aged zinc spiked soil (500 mg Zn/kg dry soil) and another 2 cm non-polluted soil on top. After 80 and 175 days, columns were sacrificed and each cm from the top down to a depth of 15 cm was sampled. Earthworm casts, placed on top of the soil, were collected. Each sample was analyzed for total and CaCl2-exchangeable zinc concentrations.Effects of earthworm bioturbation were most pronounced after 175 days. For A. chlorotica, total and CaCl2-exchangeable zinc concentrations in the polluted layers were lower with than without earthworms. Total zinc concentrations in the non-polluted layers were higher in columns with earthworms. Casts of A. chlorotica collected on the soil surface showed slightly higher total zinc concentrations than non-polluted soil. Casts were found throughout the whole column. For A. caliginosa there were no differences in total zinc concentration between columns with and without earthworms. CaCl2-exchangeable zinc concentrations in the polluted layers were lower for columns with earthworms. Casts were mainly placed on top of the soil and contained total zinc concentrations intermediate between those in non-polluted and polluted soil layers.This study shows that different endogeic earthworm species have different effects on zinc distribution and availability in soils. A. chlorotica transfers soil throughout the whole column, effectively mixing it, while A. caliginosa decreases metal availability and transfers polluted soil to the soil surface.  相似文献   

11.
A field experiment was conducted to elucidate ecosystem services provided by earthworms on the repression of phytopathogenic and toxinogenic fungi. The study focussed on decomposing Fusarium culmorum-infected and deoxynivalenol (DON)-contaminated wheat straw remaining on the soil surface as part in conservation tillage. Mesocosms were established in the topsoil of a winter wheat field located in Northern Germany, where conservation tillage has been practised for 20 years. Besides a non-earthworm treatment, two earthworm species were inoculated in the mesocosms either separately or combined: Lumbricus terrestris (anecic, detritivorous) and Aporrectodea caliginosa (endogeic, geophagous). The earthworms were exposed either to artificially Fusarium-infected wheat straw highly contaminated with DON or to non-infected straw serving as a control. The experiment was conducted during an eight week period after harvest from mid August to mid October. For both species, the artificially Fusarium-infected and DON-contaminated wheat straw was a more attractive food source than the non-infected control. In contrast to A. caliginosa, L. terrestris incorporated infected straw faster into the soil compared to control straw. Furthermore, the reduction of Fusarium biomass and DON concentration in wheat straw was significantly higher in the presence of L. terrestris than in treatments with A. caliginosa and without earthworms. Here, no significant differences could be measured between the Fusarium biomass and DON concentration in wheat straw. A. caliginosa seems not to be relevant for the reduction of Fusarium biomass and DON concentration. We concluded that amongst earthworms, anecic detritivorous species are the drivers to compensate possible negative consequences (like crop infection) of conservation tillage. They take an important role in the control of phytopathogenic and toxinogenic fungi surviving on plant residues and in the degradation of their mycotoxins.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
 A soil microcosm experiment was performed to assess the uptake of Hg from various Hg-spiked food sources (soil, leaf litter and root litter of Trifolium alexandrinum) by two earthworm species, Lumbricus terrestris (anecic) and Octolaseon cyaneum (endogeic). Treatments were applied in which one of the three food sources was Hg spiked and the other two were not. Additional treatments in which all or none of the food sources were Hg spiked were used as controls. Uptake of Hg from soil into tissues of both earthworm species was significantly higher than uptake of Hg from leaf litter or root litter, indicating that soil may be the most important pool for the uptake of Hg into earthworms. In addition, the anecic L. terrestris significantly accumulated Hg from all Hg-spiked food sources (leaf litter, root litter and soil), whereas the endogeic O. cyaneum took up Hg mainly from soil particles. Interestingly, there was no further increase in Hg in L. terrestris when all food sources were Hg spiked compared to the single Hg-spiked sources. This may be attributed to the relatively high Hg content in the soil, which may have influenced the feeding behavior of the earthworms, although their biomass did not significantly decline. We suggest that, in addition to the physiological differences, feeding behavior may also play a role in the contrasting uptake of Hg by the two earthworm species.  相似文献   

15.
Negative interactions between earthworms may arise from high earthworm population densities. Under high populations in the field, niche separation or migration away from competitive pressure may help to regulate a multi-species population to a given level. This may not be possible in laboratory experiments, leading to an increase in competitive interactions which may alter earthworm growth rates and affect decomposition and nutrient mineralization processes. The objective of this experiment was to determine how growth rates of the endogeic earthworm Aporrectodea caliginosa Sav. and the anecic earthworm Lumbricus terrestris L. are affected by increasing population density and container size in both single- and multi-species cultures. Earthworm growth responses were compared in 1-L cylindrical pots containing disturbed soil and in 2.3-L PVC cores containing undisturbed soil. The relationship describing intra- and inter-specific competition was not affected by container type for both species. Nonetheless, decreasing the container size restricted the growth of L. terrestris in both single- and multi-species cultures, but only restricted the growth of A. caliginosa in multi-species cultures. For both species, a population density greater than one individual per litre reduced earthworm growth rates significantly, while weight loss in monocultures occurred when there were more than 10 A. caliginosa, and more than three L. terrestris per litre. Growth rates of both species were restricted in all population density treatments including the lowest of 0.9 individuals per litre. Further work is needed to find the population density at which growth rates are not affected and which may be used as an appropriate population in laboratory pot experiments to measure the effects of earthworms on soil processes and plant growth.  相似文献   

16.
A microcosm experiment was carried out for 56 days at 12 °C to evaluate the feeding effects of the endogeic geophagous earthworm species Aporrectodea caliginosa on the microbial use of 15N-labelled maize leaves (Zea mays) added as 5 mm particles equivalent to 1 mg C and 57 μg N g−1 soil. The dry weight of A. caliginosa biomass decreased in the no-maize treatment by 10% during the incubation and increased in the maize leaf treatments by 18%. Roughly 5% and 10% of the added maize leaf-C and leaf-N, respectively, were incorporated into the biomass of A. caliginosa. About 29% and 33% of the added maize leaf-C were mineralised to CO2 in the no-earthworm and earthworm treatments, respectively. The presence of A. caliginosa significantly increased soil-derived CO2 production by 90 μg g−1 soil in the no-maize and maize leaf treatments, but increased the maize-derived CO2 production only by 40 μg g−1 soil. About 10.5% of maize leaf-C and leaf-N was incorporated into the soil microbial biomass in the absence of earthworms, but only 6% of the maize leaf-C and 3% of the maize leaf-N in the presence of earthworms. A. caliginosa preferentially fed on N rich, maize leaf-colonizing microorganisms to meet its N demand. This led to a significantly increased C/N ratio of the unconsumed microbial biomass in soil. The ergosterol-to-microbial biomass C ratio was not significantly decreased by the presence of earthworms. A. caliginosa did not directly contribute to comminution of plant residues, as indicated by the absence of any effects on the contents of the different particulate organic matter fractions, but mainly to grazing of residue-colonizing microorganisms, increasing their turnover considerably.  相似文献   

17.
Previous laboratory studies using epigeic and anecic earthworms have shown that earthworm activity can considerably increase nitrous oxide (N2O) emissions from crop residues in soils. However, the universality of this effect across earthworm functional groups and its underlying mechanisms remain unclear. The aims of this study were (i) to determine whether earthworms with an endogeic strategy also affect N2O emissions; (ii) to quantify possible interactions with epigeic earthworms; and (iii) to link these effects to earthworm-induced differences in selected soil properties. We initiated a 90-day 15N-tracer mesocosm study with the endogeic earthworm species Aporrectodea caliginosa (Savigny) and the epigeic species Lumbricus rubellus (Hoffmeister). 15N-labeled radish (Raphanus sativus cv. Adagio L.) residue was placed on top or incorporated into the loamy (Fluvaquent) soil. When residue was incorporated, only A. caliginosa significantly (p < 0.01) increased cumulative N2O emissions from 1350 to 2223 μg N2O-N kg−1 soil, with a corresponding increase in the turnover rate of macroaggregates. When residue was applied on top, L. rubellus significantly (p < 0.001) increased emissions from 524 to 929 μg N2O-N kg−1, and a significant (p < 0.05) interaction between the two earthworm species increased emissions to 1397 μg N2O-N kg−1. These effects coincided with an 84% increase in incorporation of residue 15N into the microaggregate fraction by A. caliginosa (p = 0.003) and an 85% increase in incorporation into the macroaggregate fraction by L. rubellus (p = 0.018). Cumulative CO2 fluxes were only significantly increased by earthworm activity (from 473.9 to 593.6 mg CO2-C kg−1 soil; p = 0.037) in the presence of L. rubellus when residue was applied on top. We conclude that earthworm-induced N2O emissions reflect earthworm feeding strategies: epigeic earthworms can increase N2O emissions when residue is applied on top; endogeic earthworms when residue is incorporated into the soil by humans (tillage) or by other earthworm species. The effects of residue placement and earthworm addition are accompanied by changes in aggregate and SOM turnover, possibly controlling carbon, nitrogen and oxygen availability and therefore denitrification. Our results contribute to understanding the important but intricate relations between (functional) soil biodiversity and the soil greenhouse gas balance. Further research should focus on elucidating the links between the observed changes in soil aggregation and controls on denitrification, including the microbial community.  相似文献   

18.
The response of earthworms to soil application of boardmill waste sludge was quantified in field and laboratory experiments. The influence of one application of 6×104 tonnes ha−1 of unamended sludge was tested against no application on silty-clay arable soil. After 2 years, results in stubble-cultivated soil showed a 1.7 times lower density of earthworms where sludge was added, whereas there was no difference in average earthworm fresh weight. In direct-drilled soil, there was an indication of lower average numbers of Lumbricus terrestris middens when sludge was applied. Negative impacts in the field may have been due to indirect negative effects of the sludge application. In the laboratory, habitat choice tests were undertaken with two common species from the field site using sludge-based mulch and fertiliser products. Aporrectodea caliginosa showed no discernible preference between soil and soil mixed with unamended sludge (mulch), but favoured soil over soil mixed with sludge and chicken manure (fertiliser). Tests with L. terrestris showed a similar pattern. The preference of L. terrestris for the two products was compared with that for chopped barley straw by direct observation of foraging behaviour. Differences in foraging time of L. terrestris for different feeds were not significant, but mass of straw collected was significantly greater compared with either type of sludge treatment.  相似文献   

19.
Few earthworms are present in production agricultural fields in the semi-arid plains of Colorado, where earthworm populations may be constrained by limited water and/or organic matter resources. We conducted a 12-week laboratory incubation study to determine the potential of a non-native endogeic earthworm (Aporrectodea caliginosa) to survive in a low-organic matter Colorado soil (1.4% organic C content), supplemented with or without biosolids, and to determine the effects of A. caliginosa on soil microbial biomass and soil nutrient availability. A factorial design with three main effects of A. caliginosa, biosolids addition, and time was used. Data was collected through destructively sampling at one, two, four, eight, and twelve weeks. During the 12-week study, 97.5% of the worms in the soil survived, and the survival of the earthworms was not significantly affected by the addition of biosolids. The addition of biosolids, however, did significantly reduce the gain in mass of the earthworms (8% mass gain compared to 18% in soil without biosolids). The presence of A. caliginosa significantly increased soil NH4-N, and NO3-N concentrations by 31% and 4%, respectively, which was less than the six fold increases in both soil NH4-N, and NO3-N concentrations supplied from biosolids. Microbial biomass carbon was not affected by A. caliginosa, but microbial biomass N was affected by an earthworm × biosolids interaction at week 1 and 12. We concluded that A. caliginosa can survive in a low-organic matter Colorado soil under optimal moisture content and that once established, A. caliginosa can provide modest increases in inorganic N availability to crops Colorado agroecosystems.  相似文献   

20.
The diet of earthworms includes soil organic matter, soil microbes and other microfauna, but the relative contribution of these dietary components to earthworm nutrition is not well known. Analysis of fatty acid (FA) profiles can reveal trophic relationships in soil food webs, leading to a better understanding of the energy and nutrient flows from microbiota to earthworms. The objective of this study was to determine the origin of FAs assimilated by the earthworm Lumbricus terrestris L. We analysed the pattern of FAs in: (i) the bulk soil, (ii) soil in the earthworm gut, (iii) the absorptive tissue of the earthworm gut wall, and (iv) the muscular layers of the earthworm body wall. Multivariate analyses performed on the FA profiles suggest that the microbial community in the earthworm gut differs from that in bulk soil. Diverse bacterial and fungal derived FAs, which earthworms cannot synthesize, were found in the earthworm gut wall and body wall, and in the neutral lipids (storage lipids) of the gut wall. The major compounds isolated were 20:4ω6, 20:5ω3 and 18:2ω6, followed by the monoenoic 18:1ω7 and 18:1ω9c, and the saturated 18:0. The microbial FA assemblage in the gut wall resembled the gut soil more than the bulk soil, and the body wall of L. terrestris showed the same microbial derived FA pattern as the gut wall, although at reduced concentrations. We propose the existence of a specific microbial community in the earthworm gut that provides FAs to the earthworm. It appears that L. terrestris may derive more of its energy and nutrients from gut specific microbiota than from microbiota already present in the ingested soil, based on the trophic relationships revealed through FA analysis.  相似文献   

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