Species richness and zoogeographic affinities of earthworms in Cyprus

A new survey taken in the East Mediterranean island of Cyprus showed an increase in the number of earthworm species (from the six recorded earlier to 16). These species belong to two earthworm families: Lumbricidae (15 species) and Acanthodrilidae (one species). The majority of these species are autochthonous (57–64%) and five to seven species (36–44%) were introduced. The autochthonous species are (i) endemic of the Levant (Dendrobaena semitica), (ii) distributed in Anatolia and the Caucasus (D. pentheri), (iii) distributed from Europe up to Anatolia (Allolobophora nematogena, D. pantaleonis, Proctodrilus tuberculatus) (iv) distributed from Europe up to the Levant (Murchieona minuscula), (v) distributed in the Transcaucasian region and in the East Mediterranean (Helodrilus patriarchalis), or (vi) widely distributed along the Mediterranean basin (D. byblica, Eiseniella neapolitana, and Octodrilus complanatus). The data obtained indicate that the Cypriote earthworm fauna is significantly richer in species than previously thought and that it has more zoogeographic affinities with the Anatolian fauna than with those of Levant.     

Abundance of biogenic structures of earthworms and termites in a mango orchard

A comparative study of the spatial distributions and the quantity of biogenic structures produced by earthworms and termites (Odontotermes nilensis and Ancistrotermes guineensis) has been conducted in a mango orchard at Thiès (Senegal).This study showed that surface biogenic structures may represent a large amount of modified soil (up to 536.5 g m⁻²) which vary depending upon the seasons and the species. Whilst the quantity of casts was independent on the season (178.6 g m⁻²), O. nilensis sheetings fluctuated with the seasons. In addition, we show that the spatial organisation of surface biogenic structures fluctuates with seasons. It displays patches ranging from 5 to 15 m. There is a link between the distribution of earthworm casts and the vegetation. In addition, spatial distribution was also linked to the biology of constructing species. We observed that the A. guineensis’ filling structures were mainly located under the mango trees during the dry season where the stems and the brushwoods were abundant. It appears that the spatio-temporal distribution of the biogenic structures under study depended upon two main factors: season and vegetation. However, depending upon the biology of the engineer, these two factors influenced the spatial distribution of structures in different ways.     

The efficiency of soil hand-sorting in assessing the abundance and biomass of earthworm communities. Its usefulness in population dynamics and cohort analysis studies

Pit digging and manually revising soil blocks is a frequently used method used for field studies of earthworm communities. The aim of this study was to compare the efficiency of hand-sorting (HS) to extract small earthworms, ca. 0.2 g, and the usefulness in studies of population dynamics and cohort analysis. Many earthworms are not recovered when revising manually the soil. Factors include soil characteristics, i.e. moisture, texture, etc. and also a human factor, which is more relevant if the study is conducted in the long-term. We used data collected in a field study of earthworm communities during 2 years in the savannas of Colombia. Small soil blocks (20 × 20 × 20 cm) were dug out in order to collect the smallest earthworms by washing-sieving (WS) and compare the results with the standard HS of large monoliths (100 × 100 × 50 cm). In fact, this methodology has rarely been addressed in earthworm population field studies. Our results showed that HS efficiency varied owing to the species and ranged from 31.4% up to 100% in the savanna and from 44% to 80% in the pasture, for two small species, i.e Aymara n. sp. (epigeic) and Ocnerodrilidae sp. (endogeic). In the case of the Glossodrilus n. sp. (endogeic) these values were similar, i.e. 51.7% and 58.1%, in the savanna and pasture, respectively. We also used frequency tables to calculate the average efficiency of HS 1 m² soil cores for each weight class in each species in order to obtain a population density correction factor. This allowed us to make corrections in earthworm density in the histograms for population dynamics analysis. We conclude that this method should be the modus operandi in long-term earthworm demography studies.     

Effects of disturbance on the biodiversity and abundance of isopods in temperate grasslands

Connell's ‘intermediate disturbance hypothesis’ was tested using a relatively simple, species poor isopod community in grass heaths and in a coastal sand dune grassland. Variation in diversity resulted from disturbance both to the soil profile and sward structure due to grazing. Predictions from a spatial survey were tested using a 20 years time series. These changes were related to changes in rabbit activity, anthropogenic soil disturbance and on one site, deposition of blown sand. Changes in the soil profile resulted in diversity initially increasing due to decreases in the density of the commonest species, leading to an increase in equitability. Prolonged disturbance to the soil profile both due to sand blowing onto one site and rotavating on another, lead to a reduction in diversity due to one of the species being eliminated. The isopod community was most diverse when least disturbed by grazing, of intermediate diversity under intermediate grazing intensity and least diverse when most heavily grazed. In these simple communities, differences in diversity were mostly determined by differences in equitability rather than in species richness. We conclude that maximising heterogeneity of sward structure could have advantages for the conservation of both invertebrate biodiversity and vertebrates that feed on them.     

Long-term effects of leguminous cover crops on biochemical and biological properties in the organic and mineral layers of soils of a coconut plantation

The primary aim of the study was to determine the long-term (12 years) effects of leguminous cover crops like Atylosia scarabaeoides, Centrosema pubescens, Calopogonium mucunoides and Pueraria phaseoloides on important soil biochemical and biological properties and their interrelationships in the organic (fresh litter layer, F and fermented + humus layer, F + H) and mineral (0–10 and 10–20 cm) layers of soils of a 19-year-old coconut plantation.The total biomass production (above-ground) for the 12-year period varied significantly between the cover crops and ranged from 34.86 (calopo) to 90.43 (pueraria) Mg ha^–1. Total N and C additions at the cover cropped (CC) site for the 12-year period were 0.97–3.07 Mg ha^–1 and 16.90–43.34 Mg ha^–1, respectively. Irrespective of layers, the levels of organic C, total N, organic substrates viz., dissolved organic C and N, labile organic N, water soluble carbohydrates, and light fraction organic matter-C and were markedly higher in the CC site compared to the control. Consequently, the levels of microbial biomass-C (C_MIC), -N (N_MIC) and -P (P_MIC), net N mineralization rates, CO₂ evolution, metabolic quotient (qCO₂) and the activities of l-asparaginase, l-glutaminase and β-glucosaminidase were significantly higher in the CC site compared to the corresponding levels in the control site. Between layers, the levels of various chemical, biochemical and microbial parameters were consistently higher in the organic layers compared to the mineral layers at all the sites including control. Among the ratios of various microbial indices, the ratios of C_MIC: organic C and C_MIC: P_MIC did not differ significantly between the layers and sites. However, the ratio of C_MIC: N_MIC was relatively higher in the mineral layers and control site. The variation in individual soil properties between layers and sites reflected the concomitant changes occurring in soil organic matter content. Apparently, microbial activity was limited by the supply of biologically available substrates in the mineral layers and the control site. Contrarily, the more direct supply of nutrients from decomposing plant litter and the indirect supply of nutrients from the mineralization of organic matter led to significantly higher levels of microbial biomass in the organic layers.     

The influence of livestock dung on the abundance of exotic and native earthworms in a grassland in south-eastern Australia

It is well known that organic matter in the form of dung is utilised as a food source by some earthworms, but little has been reported on the preferences of earthworms for different types of dung in agricultural settings. An experiment was carried out in spring in south-eastern Australia to evaluate the effect that dung from different livestock has on the abundance of earthworms in a grassland environment. We were particularly interested to compare the responses of native Australian earthworms (Megascolecidae) with those of exotic earthworms (Lumbricidae and Acanthodrilidae). The attractiveness of dung from sheep, cattle and horses was measured by determining the abundance and biomass of the resident earthworm species under each dung type at varying times after adding the dung to the soil surface (0, 10, 20 and 30 days). The earthworm population consisted of three exotic species, Apporrectodea trapezoides, Microscolex dubius and M. phosphoreus, and two native species, Spenceriella macleayi and S. bywongensis. Both the number of days that the dung was available to earthworms and the type of dung influenced the numbers and biomass of the earthworms found beneath the dung pats. Significant interactions existed between time and dung type when all adult earthworms were considered as one group and also when adults were split into individual species. The various species responded differently to the dung, but horse dung was generally the more preferred dung type. The significance of these results is discussed in terms of the management of dung in an Australian pastoral context.     

Biodiversity and abundance of terrestrial isopods along a gradient of disturbance in Sabah,East Malaysia

Connell's intermediate disturbance hypothesis predicts that the highest diversity is maintained at intermediate levels of disturbance. We have examined this hypothesis by observing differences in biodiversity of terrestrial isopods along a gradient of disturbance from two undisturbed primary tropical rainforest sites, to a logged site, a mixed native fruit orchard and a commercial oil palm plantation, in Sabah, East Malaysia. We describe a standardised protocol for the rapid assessment of isopod biodiversity on tropical forest floor sites and for measuring environmental variables to which we have related differences in species richness and relative abundance of the isopods. The results do not support Connell's hypothesis because there were no significant differences in diversity, species richness or equitability between disturbed sites and the nearest primary forests. The relative abundance of individual species was highest in the most disturbed environment. We suggest that this may be because particular species are well adapted to exploiting resources under the more ‘r’ selection conditions created by disturbance. Possible reasons for why the observations do not conform with predictions from the intermediate disturbance hypothesis are discussed. We conclude that Huston's dynamic equilibrium model is more appropriate than the intermediate disturbance hypothesis in predicting the effects of disturbance of tropical rainforests on these arthropod macro-decomposers.     

Accumulation of heavy metals by enchytraeids and earthworms in a floodplain

The river floodplain ‘Afferdense and Deestsche Waarden’ (ADW) in The Netherlands is diffusely contaminated with several heavy metals. It is, however, unclear whether this mixed contamination exerts any adverse ecotoxicological effects. In November 2000 and May 2001 a field survey was conducted in two areas in the ADW to collect a wide range of data concerning contamination levels, bioavailability, enchytraeids and earthworms and abiotic factors such as lutum and organic matter content, cation exchange capacity (CEC) and soil nutrient concentrations. Earthworms and enchytraeids were also analyzed for heavy metal content. At both sites arsenic and zinc were present in soil at relatively high concentrations (above the Dutch intervention value). In the two areas, both enchytraeids and earthworms accumulated metals. Fridericia ulrikae accumulated more cadmium than Enchytraeus buchholzi and Henlea perpusilla. The earthworm Lumbricus rubellus accumulated larger concentrations of Cr, Cu and Pb than Aporrectodea caliginosa and Allolobophora chlorotica. Dietary, physiological and behavioral characteristics may have contributed to these differences.     

Influence of agricultural intensification on the earthworm community in arable farmland in the North China Plain

Two field experiments had been conducted in Huantai County, Shandong Province, east of China, with an effort to understand the impact of agricultural intensification on earthworm diversity and population density. Seven species of earthworms were identified in the two experiments. Average earthworm populations in the higher fertility soil (experiment B, 1.83% organic matter) were relatively abundant, with a population density of 105 indiv./m² and biomass of 57 g/m². Aporrectae trapezoids was the most dominant species. In the lower fertility soils (experiment A, 1.43% organic matter) the population density was only 51 indiv./m² and the average biomass was 30 g/m². Drawida gisti was the most dominant species. For both the experiments A and B, organic fertilizer (OF) and crop straw return increased earthworm abundance. The impact of chemical fertilizer (CF) on the earthworm population was found to depend on the amount of organic input. In experiment B, the earthworm biomass decreased when only winter wheat (Triticum aestivum) straw was input at three CF application levels. However, while both winter wheat straw (WS) and corn (Zea mays) stalk returned, there was no negative correlation between CF and earthworm density and biomass.     

Indirect gradient analysis at different spatial scales of prorated and non-prorated earthworm abundance and biomass data in temperate agro-ecosystems

We investigated how earthworm communities of agricultural systems vary in abundance, biomass and species composition at different spatial scales. In four farms representative of the main agro-ecological regions of Belgium 14 parcels were sampled using a combined method (hand sorting after formalin extraction). Parcels in both grassland and arable land were studied. In each parcel two or three sample plots (1 m²) were randomly selected; these were further split up in two, resulting in four or six 0.5 m² subplots per parcel. Principal component analysis was applied to earthworm numbers and biomass. Innovative was that we compared the results from data matrices with raw data with prorated matrices, where unidentified juveniles were added to species following certain rules. To test the degree of variability between the different spatial levels, average distances between subplots, plots and parcels based on ordination scores were compared. A general linear model with a nested structure for subplots, plots, and parcels was built to find absolute differences between farms. Earthworm numbers ranged from 10 to 463 individuals m^–2, biomass varied between 3 and 186 g m^–2 and species numbers ranged from one to seven per parcel. Ordinations separated earthworm communities along a geographical—mainly soil—gradient on the first axis and distinguished between land uses along the second axis. Both in numbers of individuals and in biomass differences in earthworm populations increased from subplot to parcel level. As expected, differences within a pair of subplots were small. Plots within the same parcel tended to be highly similar, but in some cases large dissimilarities were encountered, reflecting a clustered population structure of earthworm communities at the field scale, and, possibly, abiotic gradients. The largest differences were observed at the parcel level. The latter may be attributed to differences in land use. Prorating had a narrowing effect on the data through which differences became less pronounced.     

Effects of carbendazim and lambda-cyhalothrin on soil invertebrates and leaf litter decomposition in semi-field and field tests under tropical conditions (Amazônia,Brazil)

Effects of the fungicide carbendazim and of the insecticide lambda-cyhalothrin on soil invertebrates and litter decomposition under tropical conditions were assessed in ecotoxicological semi-field studies using intact soil-core terrestrial model ecosystems (TMEs) and in a field test applying the litter-bag method. In the TME study, performed indoors under controlled conditions, earthworms, isopods and diplopods were added to intact soil cores and mortality of soil invertebrates and mass loss of leaf litter were assessed. The field study was performed on an abandoned rubber plantation near Manaus (Amazonia, Brazil). The measurement endpoints were abundance of the soil fauna and mass loss of leaf litter. In the TMEs carbendazim caused a decrease in the abundance of the introduced earthworm Pontoscolex corethrurus and, partly, of the milliped Trigoniulus corallinus. In the field carbendazim decreased the abundance of the native earthworm Andiorrhinus amazonius. Lambda-cyhalothrin was toxic to isopods and millipedes in the TMEs, whereas no effect on arthropods was detected in the field. Organic matter breakdown measured as mass loss of leaf litter in TMEs over time revealed that the two tested agrochemicals can have an impact on decomposition at field relevant concentrations. In the field the results were less obvious, due to spatial heterogeneity through which possible effects of the tested agrochemicals could have been masked.     

Long-term consequences of biochemical and biogeochemical changes in the Horseshoe Bend agroecosystem,Athens, GA

Understanding many soil processes, including the accumulation of organic matter and the formation and loss of soil aggregates, requires research that is conducted over decadal time periods. The dynamics of soil organic matter and soil fauna at the Horseshoe Bend (HSB) agroecosystem site in Georgia have been studied in replicated experimental plots since 1978. The experimental treatments (no-tillage (NT) and conventional-tillage (CT) regimes) are continuing to diverge in amounts and distribution of SOM in the soil profiles of HSB. Our current research focuses on two major areas: 1) long-term measurements of the gradually-increasing base of soil organic matter from C3-pathway plants, in crop rotations that have been in effect since 1997; 2) following the production, accumulation, fate and ecological effects of the Bt (Bacillus thuringiensis) proteins from the summer planting of Bt (and non-Bt) cotton in subplots within our main plots. The variation in the size of soil aggregates may influence the sequestration of Bt toxins, and their breakdown products, within soils. NT management systems at HSB generate an increasing proportion of soil macroaggregates in comparison to the markedly reduced macroaggregates in our CT plots. We suggest that NT systems may sequester more Bt-related products than will CT plots.     

Community structure of oribatid mites in relation to elevation and geology on the slope of Mount Kinabalu,Sabah, Malaysia

The patterns of oribatid communities were investigated in relation to elevations (700, 1700, 2700 and 3100 m a.s.l.) and geological substrates (i.e. non-ultrabasic and ultrabasic rocks) on the slopes of Mt. Kinabalu, Sabah, Malaysia. The density and morphospecies richness of oribatid mites were greater in the non-ultrabasic plot than in the ultrabasic plot at each of the same elevations. The density and richness of Oribatid mites decreased with elevation on both substrates, but the effects of elevation on the density on non-ultrabasic were less significant than on the ultrabasic substrate. Oribatid mite density correlated positively with the concentration of soil organic phosphorus and negatively with that of exchangeable Ca in soil. The richness of morphospecies of oribatid mites positively correlated with phosphorus concentration in litter, above-ground biomass, tree diversity and litterfall amount, and negatively correlated with elevation and Ca in soil. Morphospecies from families Galumnidae, Otocepheidae, Haplozetidae and Scheloribatidae were dominant in each plot. Canonical correspondence analysis (CCA) showed the importance of elevation for the community structure of oribatid mite. In conclusion, total density or morphospecies richness of oribatid communities was influenced by both geology and elevation, and morphospecies composition was strongly influenced by elevation.     

Decomposition and nitrogen dynamics of litter in peat soils from two climatic regions under different temperature regimes

Soil temperature is a major factor affecting organic matter decomposition and thus, global warming may accelerate decomposition processes. However, it remains unclear whether the effects will be similar in climatically different regions. The effects of soil temperatures of 5, 10 and 15 °C on the decomposition of Scots pine (Pinus sylvestris L.) needles were assessed in a 1-year (360 days) growth chamber experiment. Intact peat cores from two climatically different peatland sites (southern and northern Finland) were used as the incubation environments. Needles were incubated in litter bags beneath the living moss layer, and mass loss and nitrogen (N) concentration were determined at 60-day intervals. The rate of mass loss from the needles over time was clearly lower in the 5 °C treatment than at the higher temperatures. Mass loss was strongly related to the accumulated soil temperature sum. In temperatures higher than 5 °C, mass losses were higher in the northern peat. Also, the limit value of decomposition (asymptotic maximum mass loss) was slightly higher in the northern peat (92%), than in the southern peat (87%). The N concentration increased up to a mass loss of 50–60%, whereupon it decreased, while the amount of N (as a percentage of the original amount) remained unchanged until a mass loss of 50–60%, whereupon it decreased linearly. It seems that increasing soil temperatures may result in slightly higher rates of needle litter mass loss and consequent N release in northern peat than in southern peat. The faster decomposition in higher temperatures in the northern peat, together with the slightly higher maximum mass loss value, imply that with climatic warming, susceptibility of boreal peatlands for becoming sources of carbon to the atmosphere may increase towards north.     

Soil macrofauna affect crop nitrogen and water use efficiencies in semi-arid West Africa

It is increasingly recognised that soil fauna have a significant role in soil processes affecting nutrient availability and crop performance. A field experiment was conducted in southern Burkina Faso (West Africa) to investigate the contribution of soil fauna to nutrient availability and crop performance after application of different organic materials with contrasting qualities. A split plot design with four replications was laid out. The main treatment was the use of insecticides, to establish plots without fauna next to plots with fauna. The sub-treatments consisted in the application of Andropogon straw, cattle dung, maize straw, compost or sheep dung and a control. Soil fauna significantly increased crop water use efficiency. Crop nutrient use efficiency was high with the use of easily decomposable organic material in the presence of soil fauna. Supplementing low quality organic resources with mineral nitrogen is required to optimise the effects of their interaction with soil fauna towards enhanced crop nutrient and water use efficiencies.     

Effect of green manure Sesbania sesban and nitrification inhibitor encapsulated calcium carbide (ECC) on soil mineral-N,enzyme activity and nitrifying organisms in a rice–wheat cropping system

Green manure Sesbania sesban (S. sesban) and the nitrification inhibitor encapsulated calcium carbide (ECC) have been used to improve N supply and management in rice–wheat production systems in India. However, the ecological impact of combined use of these materials is largely unknown. We conducted a net-house pot culture experiment for 2 years, to investigate the effects of S. sesban and ECC on mineral N availability (NH₄⁺ and NO₃^–), soil enzyme activities (dehydrogenase and nitrate reductase) and populations (MPN) of nitrifying organisms under a rice–wheat cropping system. Green manure S. sesban and ECC (+ECC or –ECC) were applied along with urea in various combinations to hybrid rice under flooded conditions. For wheat, it was urea alone or urea + ECC. Soil samples were studied at 10 days after top dressing, i.e. 40 days after rice transplanting and 35 days after wheat sowing, for above characteristics. The mineral-N in soil revealed the significant effect of combined use of S. sesban and ECC to enhance NH₄⁺ and total mineral-N (NH₄⁺ + NO₃^–) contents. Dehydrogenase and nitrate reductase activities and population (MPN) of ammonia oxidizing bacteria (AOB) revealed a significant reduction in soils, whereas nitrite oxidizing bacteria (NOB) remained almost unaffected (P > 0.05) in response to application of ECC with S. sesban and urea. Our results suggest that slow release of acetylene (C₂H₂) from ECC has reduced ammonia mono-oxygenase with reducing population of AOB, and has the potential to retard the enzyme activities in favor of C and N conservations in a semi-arid agro-ecosystem.     

The effect of two ant species Lasius niger and Lasius flavus on soil properties in two contrasting habitats

Ants significantly change the soil environment within the nest. The aim of this study is to contribute to ecology and thus the importance of two ant species Lasius niger and Lasius flavus in a post-mining landscape near the town of Sokolov in northwest Bohemia where both species are common. Chemical (total C, N, and available P) and microbiological parameters (respiration, cellulose decomposition and direct counts of bacteria) were investigated in both ant species in two different habitats: a tertiary clay heap after brown coal mining with a weakly developed organic layer and semi natural meadows with well developed organic horizons. Total C and N in the L. flavus mound was lower than in the surrounding soil in both stands, the same was true for total N in L. niger on the heaps. L. niger nests in both sites were significantly enriched by available P. A litter bag test with cellulose indicated lower decomposition in the ant nest in comparison with the surrounding soil. Respiration seems to be limited by lower soil moisture in the nest. However, microbial respiration, even in suitable moisture conditions, did not differ between the nest and soil (on heaps) or nest respiration was significantly lower (in L. flavus nests in the meadow). In meadow soil both species had a lower bacteria count than the surrounding soil, but the L. niger nest on the heap had higher bacterial numbers. Both species significantly alter soil conditions, although the effect on selected parameters is variable. Moreover, the result with lower nest moisture and lower decomposition rate in ant mounds indicates that soil moisture should be the next important factor limiting soil processes inside ant mounds.     

Coarse woody debris,soil properties and snails (Mollusca: Gastropoda) in European primeval forests of different environmental conditions

We studied the snail fauna of four primeval forests of Central Slovakia and focused on the influence of forest type and coarse woody debris (CWD) on species assemblages. We found a total of 3281 individuals from 39 species. Species assemblages differed between the forests. In SW-facing oak forests, CWD enhanced the proportion of forest species such as the wood-grazing Cochlodina laminata and decreased the proportion of euryecious species like the litter-dwelling Punctum pygmaeum. In NE-facing beech forests, hygrophilous species such as Carychium tridentatum dominated the assemblages. This litter-dwelling snail was especially abundant close to CWD. The NE-facing beech forests harbored more species and individuals than the SW-facing oak forests did. CWD enhanced snail abundance, species richness and biodiversity, irrespective of forest type. We found positive correlations for abundance and species richness to the amount of leaf litter, C_org, N_tot, Ca²⁺, and K⁺; snail abundance was also positively correlated to soil pH. All these soil chemical factors were higher close to CWD than distant from CWD.