Soil Microarthropod Communities Research Articles

Microarthropod density and diversity respond little to spatial isolation

Summary The effect of spatial isolation on the soil microarthropod community of a deciduous forest was investigated for 16 months. Soil animals were confined in plastic tubes (diameter: 7 cm; length: 15 cm). We expected the density and diversity of most microarthropods to decrease with time in isolated habitats and this decline to be more pronounced in species of high trophic level. We also expected that species that are top-down controlled, such as collembolans, would benefit from reduced predator densities whereas species suffering little from enemies, such as oribatid mites, would be little affected. In contrast to these hypotheses, the density and diversity of almost all microarthropod taxa (Gamasina, most groups of Oribatida and Collembola) were not significantly reduced by isolation. Also in contrast to our expectation, the density of predators (Gamasina) increased in isolated habitats. This increase may have resulted from the release of predator pressure, due to the exclusion of macrofauna predators. We conclude that soil microarthropods in the studied forest are insensitive to spatial isolation. Food generalism and parthenogenetic reproduction may enable them to persist in isolated communities.

Microarthropod communities in anthropogenic urban soils. 1. Structure of microarthropod complexes in soils of roadside lawns

The structure and abundance of microarthropod communities in soils of roadsides in the city of Vilnius were studied. Soil samples were taken from lawns on roadside slopes and in roundabout junctions, at the curb and at a distance of 10 m from it. The abundance of microarthropods closely correlated with the degree of vegetation development: in lawns landscaped 10, 20, and 40 years ago, this parameter averaged 2300, 6500, and 49 000 ind./m2, respectively. The abundance of soil microarthropods near the curb was three times lower (for some groups five times lower) than at a distance of 10 m. Oribatid species adapted to alkaline soils in such areas were identified.

Microarthropod communities in anthropogenic urban soils. 2. Seasonal dynamics of microarthropod abundance in soils at roundabout junctions

The seasonal dynamics of microarthropods in anthropogenic soils was studied in the central lawns of roundabout junctions in the city of Vilnius. The microarthropod communities were found to suffer from the impact of automobile exhausts: their abundance was minimum at the curb and increased significantly at a distance of 10 m from it (at the center of a lawn), but it did not reach the values typical of the soil of the control plot. The dynamics of the microarthropod abundance in anthropogenically disturbed and control soils were similar, with the abundance of microarthropods increasing in the autumn-winter period (October–December). The microarthropod communities formed in the anthropogenic soils were unstable, with a high level of dominance of a few species. Oribatids Scutovertex minutus and Tectocepheus velatus, the gamasid mite Rhodacarus coronatus, and the springtail Brachystomella parvula proved to be well adapted to alkaline soils.

Using multi-objective classification to model communities of soil microarthropods

In agricultural soil, a suite of anthropogenic events shape the ecosystem processes and populations. However, the impact from anthropogenic sources on the soil environment is almost exclusively assessed for chemicals, although other factors like crop and tillage practices have an important impact as well. Thus, the farming system as a whole should be evaluated and ranked according to its environmental benefits and impacts. Our starting point is a data set describing agricultural events and soil biological parameters. Using machine learning methods for inducing regression and model trees, we produce empirical models able to predict the soil quality from agricultural measures in terms of quantities describing the soil microarthropod community. We are also interested in discovering additional higher level knowledge. In particular, we have identified the most important factors influencing the population densities of springtails and mites and their biodiversity. We also identify to which agricultural actions different microarthropods react distinctly. To obtain this higher level knowledge, we employ multi-objective regression trees.

Relating microarthropod community structure and diversity to soil fertility manipulations in temperate grassland

We aimed to identify patterns of diversity in a below-ground community of microarthropods (mites and Collembola) after 15 months of a nutrient (calcium and nitrogen) manipulation experiment, located at the Natural Environment Research Council (NERC) Soil Biodiversity Site in Scotland, UK. We found that microarthropod densities increased with elevated soil fertility, but we detected no concurrent change in the diversity of soil microarthropods (mites and Collembola combined). That microarthropod density increased concurrently with improvements in soil fertility and plant productivity suggests that soil microarthropod communities are predominately regulated by bottom-up forces, driven by increased energy transfer via plant inputs to soil, providing increased food resources for fauna. However, that we found no concurrent change in the diversity of soil microarthropods provides little support for the idea that the diversity of soil fauna is positively related to their population density, primary productivity or improvements in soil conditions resulting from nutrient manipulations. However, we did find that microarthropod communities of more fertile sites contained a greater proportion of predators suggesting that more energy was transferred to higher trophic levels under elevated soil fertility. Our findings suggest that unlike plant communities, soil faunal diversity may not be strongly regulated by competition in productive situations, since competitive exclusion might not occur due to increased predation. Whilst we conclude that soil microarthropod diversity at our study site has not been affected by the nutrient additions to date, in the longer term we predict that changes in community composition and diversity could arise, most likely through top-down regulation of the soil food web.

Temporal predictability of soil microarthropod communities in temperate forests

Summary The temporal predictability of soil microarthropod communities in stable forest ecosystems was analysed using data gathered from the literature and original data. Four studies were found with time series of at least five consecutive years; they all reported data on Collembola from temperate forests (as do the original data included). We applied the time lag analysis (regressions of Euclidian distance between communities on time lag) for detecting directional change of community composition, the partial rate autocorrelation function for detecting density dependence, and we regressed standard deviations of the logarithms of abundance on observation period for detecting the colour of the time series. Collembolan communities did not show directional change over time, and the composition of the community appeared to be predictable at a gross qualitative level: dominant species tend to stay dominant over time. A high degree of density dependence could be detected, which might be responsible for the observed temporal stability of community composition. Intra- and interspecific competition and/or predation may cause deterministic community structure and the results of this study support the increasing body of evidence that Collembola communities are structured by intensive biotic interactions. Collembolan populations did not show any fluctuations characterised by scaling laws. Either there actually exist point attractors and stable equilibria in Collembola (brought about by non-overcompensating density-dependent interactions), or Collembolan community trajectories are restarted every year by external forces. Due to the large time-scale of environmental variation in forests, low-frequency noise in Collembola may be recognisable only in time series spanning at least some decades.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on soil microarthropod communities.

The effects of the fungicide carbendazim (applied in the formulation Derosal) on soil microarthropod communities was determined in three Terrestrial Model Ecosystem (TME) tests and a field-validation study for a period of 16 weeks after application. TMEs consisted of intact soil columns (diameter 17.5 cm: length 40 cm) taken from a grassland field. The TMEs for the two tests (pre-test and ring-test) in Amsterdam, The Netherlands, were taken from the same site where the field-validation study was performed, the third TME test (pre-test) was performed in Bangor, Wales. Collembola communities showed large variations in numbers and no effects of carbendazim on species diversity were seen. Mites were not determined to species but only to four main taxonomic groups (Astigmata, Cryptostigmata, Mesostigmata, Prostigmata). Mite numbers in both TME and field soils also showed rather large variations and it was difficult to find consistent effects of carbendazim treatment. Principal response curve (PRC) analysis was performed to further evaluate effects of carbendazim on Collembola and mites in the TME and field tests. This multivariate technique demonstrated significant effects of carbendazim on Collembola communities in one TME test and the field-validation study but not in the other two TME tests, while mite communities showed significant effects in two TME tests but not in the third TME test and the field-validation study. NOECs for the effect of carbendazim on Collembola and mite communities derived from these PRC analyses ranged from 0.36 to 87.5 kg a.i./ha.

Recovery of decomposition and soil microarthropod communities in an Appalachian watershed two decades after a clearcut

We examined decomposition rates of three substrates ( Quercus prinus L., Acer rubrum L., and Cornus florida L.) in a watershed 21 years after it had been clearcut, and compared them to an adjacent control watershed. Previous investigations at these sites had shown that microarthropod populations, important components of the decomposer community, were considerably less dense in the clearcut watershed and that decomposition rates were reduced. Twenty-one years after clearcut decomposition rates in the clearcut watershed had reconverged with the control, and in the case of one substrate ( C. florida) now exceeded the control. Microarthropods maintained denser populations in the clearcut watershed, and oribatid assemblages, the most abundant taxonomic group, were more diverse in that watershed. A contrast of the decomposition of the substrates 8 and 21 years after cable-logging revealed that decomposition was slower in the control watershed in the more recent observations, though this may reflect lower precipitation that year. These results seem to confirm that microarthropod recovery may be indicative of a restored decomposer community functioning, and that this may be reflective of reconverged abiotic conditions at the site.

Microscale distribution patterns in high Arctic soil microarthropod communities: the influence of plant species within the vegetation mosaic

We tested the hypothesis that within a relatively homogeneous vegetation type the spatial configuration of different plant species may be a determining factor in the composition of the soil animal communities. Six vascular plant species (Luzula confusa, Dryas octopetala, Cassiope tetragona, Salix polaris, Silene acaulis and Saxifraga opposigifolia), growing within high Arctic Saxifraga‐lichen heath vegetation, showed different distributional patterns. Luzula confusa and S. polaris were ubiquitous throughout while D. octopetala and C. tetragona had the most scattered distributions. Soil microarthropod density varied significantly among plant species from 18 000 (S. polaris) to 42 000 m−2 (S. acaulis). Few significant numerical interrelationships were found between the population densities of the different Collembola or cryptostigmatic mite species or between microarthropod densities and variation in the physical properties of the soil associated with each plant species. However, despite the high similarity of species present, Discriminant Analysis idengified distinct microarthropod assemblages associated with each plant species. Over 70% of microarthropod samples taken from soil beneath S. polaris or L. confusa were correctly classified. Rank order of animal species abundance, however, varied among plant species. The collembolan Folsomia quadrioculata ranked first in five of the six plant species but the mite Camisia anomia was numerically dominant under S. polaris. The second most abundant species was much more variable. Despite these variations, the shape of the species rank abundance curve for microarthropods was remarkably similar for all plant species, with rank one and two species comprising ca 55 and 27% of the fauna respectively. These conclusions were reinforced by χ2 analysis which idengified significantly distinct faunal communities between each plant species. Those microarthropod species contributing most to these between‐plant differences, as measured by higher or lower than expected populations, were idengified and were shown to be not always the most abundant species. Thus, on a local scale plants of different species were shown to act as useful proxy indicators of soil conditions that affect the soil microarthropod community. This should be taken into account when designing sampling programmes for soil invertebrates.

Effects of long-term nutrient fertilisation and irrigation on the microarthropod community in a boreal Norway spruce stand

Intensive nutrient fertilisation of forests has been suggested as a method to increase production of biofuels as a replacement for fossil fuels. We used a field experiment in a Norway spruce, Picea abies (L.) Karst., stand in northern Sweden to examine possible long-term effects of forest fertilisation on soil fauna (Oribatida, Mesostigmata, Collembola, predatory macroarthropods). Fertilisers had been applied annually for a period of 13 years, both in solid and liquid form, and N was added as ammonium nitrate (75–100 kg N ha −1 per year). For comparison, control plots and plots receiving only irrigation were included. An autumn sampling showed soil fauna decreases in plots receiving fertiliser in solid form, but increases in plots receiving liquid fertiliser. Clear shifts in community composition following both fertilisation methods were seen in Oribatida and Collembola, but species number and diversity were not significantly affected. This was probably due to increases in tolerant species that balanced decreases in other species. Liquid fertilisation had less negative effects on many species than fertilisation in solid form. Irrigation alone did not affect faunal abundances and had no effect on community composition of Oribatida and Collembola. The study indicates that intensive forest fertilisation will cause large shifts in soil microarthropod communities, but that species richness may remain unaffected. The risk of species loss will probably depend upon the size of the areas used for this purpose.

Oribatid mite and collembolan diversity, density and community structure in a moder beech forest ( Fagus sylvatica): effects of mechanical perturbations

The effects of mechanical perturbations on two soil microarthropod communities (oribatid mites and collembolans) were investigated in a moder beech forest on sandstone. We disturbed the soil matrix by sieving and mixing the litter and soil of the moder profile. The top litter layer (L material) and the deep mineral soil (Bv) remained intact. Three amounts of disturbance were established: a single perturbation, perturbations once every 2 months (60 d) and once every 2 weeks (14 d). Densities of most groups of oribatid mites and all groups of collembolans declined in the disturbance treatments. In most cases, densities were lowest in the strong perturbation treatment (14 d). Desmonomata were the only group of oribatid mites that benefited from intermediate amounts of disturbance but not from the strongest disturbance. Also, disturbances reduced diversity of oribatid mites and collembolans. According to their sensitivity to disturbances oribatid mites ranked Poronota=Enarthronota=Suctobelbidae (the most sensitive)>Oppiidae> Tectocepheus>Desmonomata. The ranking of collembolans was Folsomia (the most sensitive)>Hypogastruridae/Neanuridae>Onychiuridae=Isotomidae>Entomobryidae. Generally, tolerance of disturbance was wider for oribatid mites than for collembolans. The results indicate that disturbances such as mixing of litter and soil and comminution of litter material strongly affect the density and diversity of soil microarthropods. However, they also indicate that the soil microarthropod community is resistant to weaker disturbances. In the field, mechanical disturbances are often caused by burrowing of earthworms. Our results suggest that the high density of microarthropods in moder soils may be due to the low intensities of mechanical disturbances by earthworms.

RESPONSE OF ANTARCTIC TERRESTRIAL MICROARTHROPODS TO LONG-TERM CLIMATE MANIPULATIONS

The terrestrial biota of the Antarctic Peninsula region are experiencing marked changes in climate, especially rising temperatures, precipitation, and UV-B radiation—a combination unique worldwide. These changes, combined with the inherent simplicity of terrestrial communities, have led to their use as “model systems” to predict the future climate change responses of biota at lower latitudes. However, studies integrating responses at different levels of the community trophic structure are lacking. We report here the consequences on the soil microarthropod community of a four-year, multivariate, climate-manipulation experiment carried out over vegetation near Palmer Station, Anvers Island, western Antarctic Peninsula. The experiment used a multifactorial randomized-block design, deploying filters to raise temperatures and reduce ultraviolet (UV)-B (280–320 nm) or both UV-B and UV-A (320–400 nm) radiation of existing vegetation, with further water and fertilizer amendment treatments. Seven microarthropod species recovered in sufficient numbers for statistical analyses showed considerable spatial aggregation independent of treatment, a feature typical of many soil invertebrates. Analyses using negative binomial generalized linear modeling identified further significant and consistent treatment impacts on both individual species and species groups. Relative to controls, manipulations increasing temperature decreased numbers of microarthropods (particularly Collembola), as did exposure to near-ambient levels of UV radiation (separate significant effects for both UV-A and UV-B), while water amendment increased numbers. The impacts of temperature and water are consistent with our understanding of the importance of these two environmental variables and their interaction in Antarctic terrestrial ecosystems. The negative impact of UV (-A or -B) on arthropod heterotroph and detritivore populations in the Antarctic terrestrial food web is likely to be a secondary consequence of UV impact on vegetation characteristics. This is, again, consistent with general predictions of the impact of changing UV climate on ecosystem function.

Impacts of different agricultural practices on the biodiversity of microarthropod communities in arable crop systems

Two crop production systems, which differ on tillage and pesticides, were compared for biodiversity of soil microarthropod communities. A biodiversity index, which integrates different structure and density parameters (abundance, taxonomic richness, taxonomic diversity, coenotic diversity) was used. Results showed a greater biodiversity in minimum tillage systems compared to deep tillage systems. Pesticides seemed to be only a second order factor of variance on microarthropod biodiversity.

Community composition of soil microarthropods of acid forest soils as affected by wood ash application

The responses of soil microarthropod communities of acid forest soils to wood ash-application was studied both in a sixty years old pine forest stand (wood ash dose: 3000kg ha —1 ) and in laboratory microcosms (wood ash dose: 5000kg ha —1 ). We also tested whether microarthropod communities stressed with wood ash were more sensitive to an additional disturbance, drought, than the microarthropod communities in the ash-free soil. Microarthropods were sampled five times during the field experiment and four times during the laboratory experiment. At each sampling the abundance and community structure of microarthropods were analysed. In the field the number of collembolans, and in the laboratory the number of mesostigmatid mites decreased after ash-treatment. Although in both experiments the number of oribatid mite species was lower in the ash-treated than in the control soil, principal component analysis revealed no changes in the community structure of microarthropods after the ash application. Drought had no influence on soil microarthropods. It is concluded that soil microarthropods, at least at the community level, are rather resistant to substantial changes in soil pH even though changes at the species level can take place, and that microarthropods stressed with wood ash are not more susceptible to other disturbance (drought) than microarthropod communities in the ash-free soils.

Soil microarthropod community structure and dynamics in organic and conventionally managed apple orchards in Western Colorado, USA

We studied the influences of organic and conventional management practices on microarthropod diversity, densities, and dynamics in apple orchards on the Western Slope of Colorado. The ‘organic’ orchards differed from the ‘conventional’ orchards in that they used natural fertilizers (versus synthetic) and did not use insecticides and/or herbicides. Based on findings from annual agroecosystems, we hypothesized that the conventionally managed (CM) apple orchards would support a lower diversity and density of soil microarthropods than the organically managed (OM) apple orchards. We located nine sites, three OM orchards, three CM orchards, and three native sites. From each site, microarthropods were extracted from soil samples taken from June to September of 1997 and April to September of 1998. The richness and diversity of functional groups and families did not differ among the OM orchards, CM orchards and/or native sites. We did find significantly greater ( P≤0.05) densities of soil microarthropods early in growing season, June 1997 and April 1998, in the OM orchards in comparison to the CM orchards and native sites. Furthermore, the densities of predatory mites were significantly greater in the OM orchards in comparison to both the CM orchards and native sites on selective dates throughout the period of study. Organic management practices have increased the densities of microarthropods above those found in CM orchards and native sites. These results may be due to the interaction between a greater accumulation of plant litter and organic matter in the OM orchards and the heavy pesticide use in the CM orchards.

A novel method for estimation of wild fire intensity based on ash pH and soil microarthropod community

Summary Wild fires are a complex and unpredictable phenomenon. Post hoc estimation of wild fire intensity is important in understanding the ecological impact of fire on ecosystems and their post fire regeneration. The aim of the present study was to evaluate a novel method for fire intensity estimation, based on measurements of post-fire ash pH and soil microarthropod community. Estimation of fire intensity by the novel method was compared to estimation by the mean minimum diameter of burned branch technique (MMDB), described by Moreno & Oechel (1989). The study was carried out in a Pinus halepensis Mill. forest on Mt. Carmel that burned in a wildfire in October 1998. The intensity of the fire was estimated by measuring thickness and pH of the ash layer under the canopy projection of burned trees, as well as by the MMDB technique. Variations in arthropod community were monitored in soil samples collected under the burned trees. Ash accumulation and increase of the ash layer pH were directly related to fire intensity. A positive correlation was found between the ash layer pH and minimum diameter of burned branches, with increasing fire intensities. A negative correlation was found between the size of microarthropod community and fire intensity, which also affected the composition of the arthropod community. Thus, estimation of fire intensity by integration of two factors, pH of the ash layer and composition of the microarthropod community, can give a wider understanding of fire impact on ecosystems. This integrated method is reliable, quick and inexpensive. Estimation of fire intensity can also be important for prediction of recovery time of the whole ecosystem.

Effects of temperature and moisture fluctuations on an experimental soil microarthropod community

Summary We established an experiment in microcosms with coniferous forest humus and birch leaf litter for testing the effects of constant vs. diurnally fluctuating temperature and uniform vs. varying moisture, on the population densities and species richness of Collembola and Mestostigmata. These parameters and the vertical distribution of populations were analysed by layers (top, centre, bottom) at two samplings (weeks 10 and 27). The hypotheses were that populations of at least some species benefit from fluctuating microclimate, and that varying conditions permit more species to coexist than uniform conditions. At fluctuating temperature regime, four species and total Collembola were more abundant, and species richness of Collembola was higher. One mite species and total Mesostigmata were more numerous at constant temperature. One collembolan species was more abundant at varying moisture, and one mite species at constant moisture. We conclude that the data support our hypotheses, though the observed differences between treatments were not very marked. Some species appeared to share their environment vertically.

Effects of Soil pH Gradient Caused by Stemflow Acidification on Soil Microarthropod Community Structure in a Japanese Red Cedar Plantation: An Evaluation of Ecological Risk on Decomposition

Effect of acidic stemflow input on soil biological properties around cedar tree trunk were examined in a 34 year old Japanese red cedar plantation forest. Average soil pH of soil around cedar trunk (stemflow soil) was 3.88 and that of soil between trees (throughfall soil) was 4.97, and this suggested soil acidification due to proton load via stemflow. Soil microarthropod density in soil was higher as close to tree trunk, whereas microbial biomass of surface soil was reduced ca. 30 % around trunk. Abundance of Collembola and Gamasid mites showed positive correlation to amount of soil organic matter, while Oribatida had strong negative correlation to soil pH.Tectocepheus velatus (Oribatida) was dominant in soils pH under 4.0. Annual decomposition rate of cedar foliage was reduced ca. 16% in stemflow soil compared to throughfall soil. More litter accumulation was observed in stemflow soil, but it was not significant, though low microbial activity and retarded litter decomposition may be responsible to the accumulation of organic matter in stemflow soil. Soil biological community and soil process have been changed due to stemflow, the affected area corresponded to ca. 9.4 % of the forest. Thus, ecological risk of acidification in the sense of decrease in decomposition rate is 1.4%.

Experimental manipulation of the winter surface ice layer: the effects on a High Arctic soil microarthropod community

The effect of patch size on the tolerance of the soil microarthropod population to an experimentally induced environmental catastrophe, a thick surface ice layer, was studied at a High Arctic site (78°55 ‘N, 11°53’ E). Such an ice layer currently occurs infrequently; however, climate change models suggest that the occurrence of such an ice layer is likely to increase in frequency. The experimental approach was a factorial design with two patch sizes, an icing treatment and controls. A thin layer of natural ice was present even in the controls and this was treated as a covariate in the analysis. The soil microarthropod fauna at the experimental site consisted of five species of Collembola and seven species of oribatid mite. The experimental surface ice layer reduced the total number of the soil microarthropods studied by 50%; however, mortality differed between mites and Collembola and species within the two taxo‐nomic groups. Mites were very resistant and showed no significant change, Collembola more sensitive (the populations ofHypogastrura tullbergideclined by 56% andFolsomia quadrioculataby 54′% in the iced treatment plots). The thin annual surface ice layer seemed to have an additional effect onH. tullbergiand the miteLauroppia translamcllata.That such a thin ice layer could reduce survival was unexpected and could play an important role in determining the extreme patchy distribution of arctic soil animals.

Experimental manipulation of the winter surface ice layer: the effects on a High Arctic soil microarthropod community

Experimental manipulation of the winter surface ice layer: the effects on a High Arctic soil microarthropod community