Earthworm communities in grasslands and horticultural soils

 In a survey of 42 farm sites, comprising grassland and two types of horticultural farms (growing vegetables or flower bulbs), earthworm communities were sampled by hand-sorting and a number of soil physico-chemical characteristics recorded. For heavy metals the availability in the soil solution was estimated based on the measured absolute content. Abundance, biomass and species richness were significantly higher in grassland soils than in horticultural soils, and within the horticultural farms significantly higher in vegetable than in flower-bulb farms. No epigeic species were found in horticultural soils. The differences between the various farm types were probably related to the intensity of management practices, such as soil tillage, harvesting and crop protection measures, that result in less soil organic matter of lower quality. The data from the grassland farms were analyzed in conjunction with the physico-chemical soil characteristics, applying canonical correspondence analysis. Community parameters such as species richness and diversity apparently were not related to soil characteristics, but an appreciable part of the variation in abundance and biomass of several individual species could be explained by factors such as lutum content (particles <16 μm), pH, bio-availability of metal ions and geographical position of the sample site. It is concluded that repeated surveys of this type may become a valuable tool for monitoring soil quality. Received: 16 March 2000     

Secondary succession of terrestrial isopod,centipede, and millipede communities in grasslands under restoration

The aim of this study was to investigate the impact of restoration management on the composition of a macro-invertebrate community in a formerly, nutrient-poor grassland. Four grassland plots were selected that were last fertilised 7, 11, 24 or 29 years before sampling in 1996. In the same plots it was observed that nutrient impoverishment as a restoration tool resulted in a decrease in primary production and a directional shift in vegetation composition after cessation of fertiliser application. Terrestrial isopods, millipedes, and centipedes were sampled with pitfall traps in the four plots. The directional shift observed in vegetation composition before this study was not accompanied by a directional change in macro-invertebrate composition. Both the field poorest in nutrients and the one richest in nutrients showed the lowest density and species richness, while the species composition was similar across intermediate succession stages. By far the most specimens and species were caught in the field that had not received fertilisers for 24 years. Succession theory could only partly explain the observed results. Canonical correspondence analysis of the data revealed that only a small part of the pattern could be explained by the nutrient status of the grasslands. The C accumulation due to secondary succession of plants was hypothesised to influence the densities and diversity of macro-invertebrate communities in these grasslands.     

Earthworm communities in alluvial forests: Influence of altitude,vegetation stages and soil parameters

In many terrestrial ecosystems, soil parameters usually regulate the distribution of earthworm communities. In alluvial ecosystems, few studies have investigated the impact of periodic floods and alluvium deposition on soil fauna. In this context, we assumed that earthworm communities may vary depending on altitude (alpine, subalpine, mountain and hill levels), forest successional stage (post-pioneer to mature forests) and some soil parameters. Our results demonstrated that the composition of earthworm communities differed depending on altitudinal gradients. No earthworm was found at the alpine level while maximum density and biomass were observed at the hill level mainly due to the contribution of anecic species. A total of 27 species and subspecies were found over the three sampling sites, and Lumbricus moliboeus was discovered for the first time in carbonated soils. Soil texture had a major effect on epigeics that were often associated with coarse sandy texture in contrast to anecics which preferred deep soils and mature forest stages, which in combination provided the highest carbon content and the finest soil texture. In our study, carbonated fluviosols (Fluvisols according to the World Reference Base) were recorded; fluviosols typiques with well-structured A layers were generally found in mature or intermediate forest stages while most of fluviosols juveniles with heterogeneous texture were observed principally in post-pioneer forests. We conclude that in alluvial ecosystems, earthworm communities were highly dependent first on soil parameters, then altitude and to a lesser extent forest successional stages. Changes in earthworm communities tend to reflect a gradient of alluvial dynamics thus reinforcing the potential role of earthworms as bioindicators in natural and/or semi natural alluvial ecosystems.     

Earthworm communities in birch stands with different origin in central Finland

The aim of the study was to compare earthworm communities in anthropogenous birch stands with different origin in Finland. A total of nine forest sites were investigated: three birch stands (Betula pendula) planted ca. 30 years prior to the study after clear-cutting of spruce stands (“Birch after Spruce”, BS), three birch stands planted ca. 30 years earlier on arable soil that had been under normal cultivation until forestation (“Birch after Field”, BF), and three “Natural Deciduous” forests (D). Earthworms were sampled in May and October 1999 using a combination of formaline extraction and modified wet funnels. There were conspicuous differences between replicates of similarly managed forests. Earthworms were totally lacking in one of the D sites, while another had an abundant and diverse community. Only Dendrobaena octaedra was present in one BS site, while the two others harboured also Aporrectodea caliginosa and three Lumbricus species. All these species were also present in the BF sites, where their total biomass (ranging from 70 to 138 g (f.w.)/m²) was 2.6 times the average in BS, and of the same magnitude as the average in natural deciduous stands. A separate experiment revealed that L. terresris and A. caliginosa, which are not found in the surrounding coniferous forest, are able to live and reproduce in the soil of the D site where they were absent. It was concluded that earthworm species survive and reproduce in birch stands established on arable soil, where they have invaded during the long cultivation. On the other hand, their possibilities to disperse from cultural landscapes determine their presence not only in birch stands established in earlier coniferous forests, but also in “natural deciduous” forests where source populations are not present in the surroundings.     

Relationship between plants and soil microbial communities in fertilized grasslands

The relationship between biodiversity and ecosystem functioning is of major scientific concern today. Few studies though have measured the interactions between soil microorganisms and plant diversity, the purpose of this study was to examine the link between plant diversity and microbial communities in fertilized versus unfertilized grasslands. Experiments were carried out on a permanent grassland in north-eastern France where agricultural practices had remained unchanged for the last 13 years. The experimental design included two plots of 300 m² (fertilized at 120 kg N ha⁻¹ or non-fertilized). Plots were replicated into three equal sub-plots (100 m²). From each sub-plot, six samples of soil and vegetation were taken at three dates during floristic development. At sampling, ground cover of each species was estimated, and total amount of C and N was determined in aboveground and root biomass. Soil samples were analyzed in order to measure the metabolic fingerprints of microorganisms using Biolog^® GN2 microplates. Floristic composition and carbon substrate utilization patterns of rhizobacterial communities were more diversified in unfertilized than fertilized plots. In unfertilized plots, the development of Convolvulus arvensis and two legumes (Trifolium pratense and Trifolium repens) may help maintain observed floristic diversity. Moreover, an inversion of C and N distribution between aboveground and root biomass during the vegetation cycle probably induced a variation of rhizodeposition. This phenomenon could explain the differences of rhizobacterial metabolic fingerprints observed between experimental plots.     

Earthworm communities in temperate beech wood forest soils affected by liming

To monitor the effects of liming on forest ecosystems, experimental plots were installed in forests in mid-western Germany. In addition to soil chemical indices, earthworm communities were investigated on these plots about 15 years after first lime applications took place. As a “natural reference”, communities were compared to earthworm records that derived from a beech forest on limestone. In the non-acidified plots that had never been limed only epigeic earthworms were detected in small numbers and low species richness. Forest liming caused higher pH and a higher base saturation in the mineral topsoils. To a large extent, epigeic earthworm species seemed to benefit from this and had increased in number and biomass at all three different locations selected for the investigations. The epigeic dominated communities were completed by anecic Lumbricus terrestris that was rarely found in some of the samples from one location and a number of endogeic species that showed a very patchy distribution in limed plots. In contrast to this, the soil of the beech forest on limestone showed a different community composition. It was dominated by endogeic species in abundance and by anecic species in biomass. On limestone the total biomass of earthworms clearly exceeded the biomass values from all other plots. In conclusion, a long-term support of forest earthworm fauna due to liming was detected. This support was mainly effective for epigeic species, but in some cases for endogeic and anecic species, too.     

Agricultural management affects communities of culturable root-endophytic fungi in temperate grasslands

Three grassland sites of similar physical characteristics but differing management histories were chosen to test the hypothesis that agricultural disturbance has a deleterious effect on the diversity of culturable root-endophytic fungi and favours potentially pathogenic species. Species abundance data were collected for fungi isolated from surface sterilised root samples. Brillouin index of diversity, Twinspan and detrended correspondence analysis were applied to the community data. Quantitative ordination separated the samples by site showing that the communities differed in fields of contrasting management and this was supported by data from a microcosm experiment. Species presence and absence appeared to be affected seasonally; site differences were manifested in relative abundance. Diversity did not appear to vary by site, but a methodological explanation for this is proposed. Sterile dark septate endophytes were shown to be among the most abundant groups at all sites.     

Nematode communities of grazed and ungrazed semi-natural steppe grasslands in Eastern Austria

Soil nematode communities were investigated at eight semi-natural steppe grasslands in the National Park Seewinkel, eastern Austria. Four sites were moderately grazed by horses, cattle and donkeys, four were ungrazed. Nematodes were sampled on four occasions from mineral soil, and their total abundance, diversity of genera, trophic structure and functional guilds were determined. Altogether 58 nematode genera inhabited the grasslands, with Acrobeloides, Anaplectus, Heterocephalobus, Prismatolaimus, Aphelenchoides, Aphelenchus, Tylenchus and Pratylenchus dominating. Mean total abundance at sites was 185–590 individuals per 100 g soil. Diversity indices did not separate communities well, but cluster analysis showed distinct site effects on nematode generic structure. Within feeding groups the relative proportion of bacterial-feeding nematodes was the highest, followed by the fungal- and plant-feeding group. Omnivores and predators occurred in low abundance. The maturity indices and plant parasite indices were characteristic for temperate grasslands, but the abundance of early colonizers (c-p 1 nematodes) was low. A high density of fungal-feeding c-p 2 families (Aphelenchoidae, Aphelenchoididae) resulted in remarkably high channel index values, suggesting that decomposition pathways are driven by fungi. Nematode community indices of all sites pointed towards a structured, non-enriched soil food web. At most sites, grazing showed little or no effect on nematode community parameters, but total abundance was higher at ungrazed areas. Significant differences in the percentage of omnivorous nematodes, the sum of the maturity index, the number of genera and Simpson's index of diversity were found at one long-term grazed pasture, and this site was also separated by multi-dimensional scaling (MDS).     

Soil properties, grassland management, and landscape diversity drive the assembly of earthworm communities in temperate grasslands

Earthworms are widespread soil organisms that contribute to a wide range of ecosystem services. As such, it is important to improve our knowledge, still scanty, of the factors that drive the assembly of earthworm communities. The aim of the present study was to conjointly evaluate the effects on the assembly of earthworm communities of i) soil properties (texture, organic matter content, and pH), ii) grassland management (grassland age, livestock unit, and type of fertilization), iii) landscape diversity (richness, diversity of surrounding habitats, and grassland plant diversity), and iv) presence of hedgerows. The study was conducted in temperate grasslands of Brittany, France. Earthworms were sampled in 24 grasslands and, in three of these grasslands, they were sampled near a hedgerow or near a ditch (control without a hedgerow). Soil properties explained the larger portion of the variation in the earthworm community parameters compared to grassland management or landscape diversity. The increase in soil organic matter content and pH were the most favorable factors for earthworm abundance and biomass, in particular for endogeic species. Regarding grassland management, the increase in the livestock unit was the most damaging factor for earthworm communities, in particular for the anecic earthworm biomass and endogeic species richness. Surprisingly, landscape diversity negatively affected the total earthworm abundance and epigeic earthworm biomass, but it was related to an increase in the epi-anecic species. At a finer scale, we also demonstrated that the presence of hedgerows surrounding grasslands enhanced earthworm species richness, especially within the epigeic and anecic ecological categories. This study highlights that the earthworm ecological categories respond specifically to environmental filters; further studies need to be conducted to elucidate the factors that drive the assembly of earthworm communities at this ecological category level. We recommend that policymakers should act on landscape management to favor earthworm diversity in order to improve the ecosystem services they drive.     

Earthworm communities in native savannas and man-made pastures of the Eastern Plains of Colombia

 The structure and seasonal changes of earthworm communities were evaluated in a natural savanna and in a improved grass-legume pasture in a Colombian oxisol over a period of 18 months. One plot of 90×90 m was isolated in each of the systems and each month five samples of 1 m²×0.5 m and ten of 20×20×20 cm were randomly selected from a stratified block design. Species richness was similar in the two evaluated plots (seven species), whereas diversity measured by the index, H (Shannon and Weaver 1949) was clearly different, i.e. H=2.89 in natural savanna and H=1.29 in pasture. This is explained by differences in earthworm community structure. The average annual density in the savanna was 49.8, ranging from 10.8 to 135.8 individuals (ind) m^–2, and biomass was 3.3 g m^–2 (hand-sorting method), ranging from 0.9 to 11.5 g m^–2. In the man-made pasture, density was 80.1 ind m^–2 on average, ranging from 24 to 215.8 ind m^–2 and biomass was more than tenfold higher, ranging from 29.2 to 110.4 g m^–2. This was especially due to the presence of a large glossoscolecid anecic species, Martiodrilus carimaguensis Jiménez and Moreno, which has been greatly favoured by conversion of savanna to pasture. Endogeic species were dominant in the natural savanna whereas the anecic species accounted for 88% of total earthworm biomass in the pasture. Total earthworm density and biomass were significantly different in the two systems studied (t-test). The results indicate a clearly positive response of earthworm communities to improved pastures, a type of land use that is being increasingly adopted in moist neotropical savannas. Received: 20 October 1997     

Plant communities and soil phytolith assemblages relationship in native grasslands from southeastern Buenos Aires province,Argentina

This study has compared the phytolith production and soil phytolith assemblages of two native grass communities typical in Argentina, namely the monospecific Paspalum quadrifarium community or “pajonal”, and the Stipa-Piptochaetium community or “flechillar”. Five sites – three of which had been unmanaged while other two had been submitted to fire and fire-grazing management activities – were selected for study. The results show that in these sites a) phytolith production of the plant communities differed due to their diverse floristic composition, b) it was possible to define the type of management or the type of community based on soil phytolith assemblages, c) there were differences between plant communities and soil phytolith assemblages. These results suggest that modern phytolith assemblages are composed not only of local and present vegetation but also of extralocal/regional and probably past vegetation. Hypotheses about the probable processes involved in phytolith incorporation to soil have emerged during the investigation.     

Dissimilar response of plant and soil biota communities to long-term nutrient addition in grasslands

The long-term effect of fertilizers on plant diversity and productivity is well known, but long-term effects on soil biota communities have received relatively little attention. Here, we used an exceptional long-lasting (>40 years) grassland fertilization experiment to investigate the long-term effect of Ca, N, PK, and NPK addition on the productivity and diversity of both vegetation and soil biota. Whereas plant diversity increased by liming and decreased by N and NPK, the diversity of nematodes, collembolans, mites, and enchytraeids increased by N, PK, or NPK. Fertilization with NPK and PK increased plant biomass and biomass of enchytraeids and collembolans. Biomass of nematodes and earthworms increased by liming. Our results suggest that soil diversity might be driven by plant productivity rather than by plant diversity. This may imply that the selection of measures for restoring or conserving plant diversity may decrease soil biota diversity. This needs to be tested in future experiments.     

Earthworm communities and soil properties in shaded coffee plantations with and without application of glyphosate

In central Veracruz, Mexico, many coffee plantations are managed using agrochemicals for weed control, with glyphosate-based herbicides (GBH) the most commonly used. To date, however, no studies in this region have characterized the soil biological and physicochemical properties in coffee plantations under such glyphosate application. In this study, earthworms were used as bioindicator organisms by measuring differences in the earthworm community in plots within shaded coffee plantations, with and without repeated applications of glyphosate. Differences in earthworm-induced soil processes, such as water infiltration rates, potential net carbon mineralization rates and soil physicochemical properties were also evaluated. Eight plots were selected in shaded coffee plantations; four had received regular applications of GBH over the preceding 22 years, while the other four had received no herbicides over the preceding 7 years. The earthworm species found in plots with no GBH treatment were Pontoscolex corethrurus (99%) and Amynthas corticis (1%), while A. corticis was absent in plots that had been treated with GBH. Significant differences (P < 0.01) in earthworm density (168 ± 16 and 353 ± 37 ind m⁻²) and biomass (22.7 ± 1.1 and 45.4 ± 6.9 g m⁻²) were observed in soils with and without GBH, respectively. No significant difference (P = 0.08) was observed in the water infiltration rate (2 × 10⁻⁴ ± 4 × 10⁻⁵ and 4 × 10⁻⁴ ± 1 × 10⁻⁴ cm s⁻¹ with and without GBH, respectively). Soil carbon flow was greater in plots with GBH (76 ± 7 μg dry soil⁻¹ d⁻¹) than in those without GBH (62 ± 1 μg dry soil⁻¹ d⁻¹, P < 0.005). Significant differences (P < 0.05) were found in pH and in the clay, silt and Ca content of the soil. Our findings indicated reduced species number, density and biomass of earthworms, and increased net carbon mineralization rate in plots with GBH. The plots managed with glyphosate presented a negative effect on the earthworm parameters measured, and we conclude that the earthworms therefore acted as indicators of perturbation. It is also possible that this effect could be due to factors unrelated to the glyphosate that were not considered in this study, such as chemical fertilization or legume litter spatial variability, among others.     

Grazing management of calcareous grasslands and its implications for the conservation of beetle communities

Calcareous grasslands are an important habitat for floral and faunal communities in the UK and Europe. Declines due to changes in management, scrub invasion and agricultural improvement have left much of the remnants of this habitat in a degraded and fragmented state. Grazing, by cattle or sheep, is one of the main management practices used to maintain and improve the floral and faunal quality of calcareous grassland. The long-term impacts of different grazing regimes, however, are poorly understood, particularly in terms of the invertebrate communities. This study contrasted the impacts of recently introduced and long-term sheep or cattle grazing on beetle communities present on one of the largest areas of calcareous grassland in Europe, the Salisbury Plain military training Area, UK. No effects of grazing management on beetle abundance, species richness or evenness were found, but plant diversity and overall percentage cover of grasses did influence beetle diversity. Proportions of the total number of individuals and overall species richness within beetle guilds (predatory, phytophagous, flower/seed feeders, root feeders and foliage feeders) were strongly influenced by both the duration and type of grazing animal. At the species level, beetle community structure showed significant differences between ungrazed, long-term cattle and long-term sheep grazing treatments. Changes in plant community structure were found to influence beetle community structure. The significance of these results is discussed in terms of the long-term impacts of grazing on beetle community structure, and the benefits of different grazing regimes for the conservation management of calcareous grasslands.     

Diversity and distribution of nematode communities in grasslands from Romania in relation to vegetation and soil characteristics

The nematode communities of 36 grassland ecosystems in Romania, belonging to different plant associations and soil types, were studied. The abundance of nematodes, the species and trophic types present, as well as their distribution in relation to plant community and soil characteristics are analyzed and discussed.The abundance of nematodes from the 36 grasslands studied ranged between 0.41 × 10⁶ and 8.57 × 10⁶ individuals/m², and a total of 121 genera and 145 species of nematodes were found. The highest diversity was found in grasslands developed on brown earth soil (65–67 genera and 74–76 species), with least diversity in those evolving on podzol and lithosol (33–36 genera with 25–28 identified species). Most of the dominant taxa were found in specific soil layers; some obligate plant parasitic genera (e.g., Paratylenchus, Rotylenchus, Criconema) showed preference for deeper soil layers. The nematode diversity index (H′), with values ranging between 2.38 and 3.47, did not differ significantly between the different types of grasslands. Plant feeding, bacterial feeding, hyphal feeding and omnivorous nematodes were the main groups in mountainous grasslands developed on different soil types. Plant feeding and bacterial feeding nematodes dominated the trophic structure and more plant feeders (62–69%) were found in communities of subalpine and alpine grasslands developed on podzol and alpine meadow soil, than in those developed on rendzina and lithosol (27–33%). The ratio of hyphal feeding to bacterial feeding nematodes (Hf/Bf) is constantly in favour of the bacterial feeding group, the values being an indicator of good soil fertility for most studied grasslands. The nematode communities of grasslands are grouped into six main clusters according to their genera affinity and distinguished by different grassland and soil types. Communities from subalpine grasslands developed on rendzina, acid brown and lithosol have the greatest similarities. An ordination of nematode communities in relation to important environmental variables is presented. Environmental variables relevant in explaining the patterns of nematode composition in grasslands, using canonical correspondence analysis (CCA), are: humus, pH, total nitrogen, exchangeable bases and soil type. No single factor could be selected.     

The invertebrate communities of peat and upland grasslands in the North of England and some conservation implications

From a study of the invertebrates of 42 sites on peat or on upland grasslands in Northern England, we have recognised seven invertebrate communities. The typical habitats of each community were: lowland oligotrophic mire, high altitude blanket bog, lower altitude blanket bog, ‘mixed’-moor, dry northern heath, ‘edge’-peat and upland grasslands. There is the possibility of further upland grassland communities being identified in a more extensive survey of such areas. Most sites conformed to the classification but a small number of exceptions were found and it would be unwise to predict the invertebrate community directly from the habitat.Seasonal variation in the abundance of surface-active invertebrates was measured for each invertebrate community and marked differences in the timing of the peaks were found. Differences were also found in the total biomass of invertebrates in each community. The role of these differences in creating faunistic diversity on uplands and alternative sources of food for vertebrate predators has been considered.     

Interactive effects of nitrogen fertilizer and altered precipitation on fungal communities in arid grasslands of northern China

Journal of Soils and Sediments - Fungi play an essential role in regulating the functioning of terrestrial ecosystems and are sensitive to climate change factors. Climate change incidents, such as...     

Precipitation modifies the effects of warming and nitrogen addition on soil microbial communities in northern Chinese grasslands

Terrestrial ecosystems experience simultaneous shifts in multiple drivers of global change, which can interactively affect various resources. The concept that different resources co-limit plant productivity has been well studied. However, co-limitation of soil microbial communities by multiple resources has not been as thoroughly investigated. Specifically, it is not clearly understood how microbial communities respond to shifts in multiple interacting resources such as water, temperature, and nitrogen (N), in the context of global change. To test the effects of these various resources on soil microorganisms, we established a field experiment with temperature and N manipulation in three grasslands of northern China, where there is a decrease in precipitation from east to west across the region. We found that microbial responses to temperature depended upon seasonal water regimes in these temperate steppes. When there was sufficient water present, warming had positive effects on soil microorganisms, suggesting an interaction between water and increases in temperature enhanced local microbial communities. When drought or alternating wet–dry stress occurred, warming had detrimental effects on soil microbial communities. Our results also provide clear evidence for serial co-limitation of microorganisms by water and N at the functional group and community levels, where water is a primary limiting factor and N addition positively affects soil microorganisms only when water is sufficient. We predict that future microbial responses to changes in temperature and N availability could be seasonal or exist only in non-drought years, and will strongly rely on future precipitation regimes.