Tree identity surpasses tree diversity in affecting the community structure of oribatid mites (Oribatida) of deciduous temperate forests

The role of tree diversity and identity as determinants of soil animal community structure is little understood. In a mature deciduous forest dominated by beech we identified clusters of one, two and three tree species of beech, ash and lime allowing to investigate the role of tree species diversity and identity on the density and community structure of oribatid mites. To relate oribatid mite community structure to environmental factors we measured leaf litter input, fine root biomass, mass of organic layers, topsoil pH and C and N content. We expected oribatid mite density to increase with increasing tree diversity, but we expected the effects of tree species identity to override effects of tree diversity. Further, we hypothesized the density of oribatid mites to be reduced by the presence of beech but increased by the presence of lime and ash. As expected tree diversity little affected oribatid mite communities, whereas tree species identity strongly altered density and community structure of oribatid mites. However, in contrast to our expectations the density of oribatid mites was highest in presence of beech indicating that many oribatid mite species benefit from the presence of recalcitrant litter forming thick organic layers. Especially Oppioidea benefited from the presence of beech presumably due to an increased availability of food resources such as fungi and nematodes. Lower density of oribatid mites in monospecific clusters of lime and ash suggests that oribatid mites did not benefit from high quality litter of these species. Notably, large and strongly sclerotized oribatid mite species, such as Steganacarus magnus and Chamobates voigtsi, benefited from the presence of ash and lime. Presumably, these large species better resist harsh microclimatic conditions in shallow organic layers.     

Canopy Oribatida: Tree specific or microhabitat specific?

A diverse assemblage of oribatid mites inhabits the canopy of coniferous trees in western North America. We tested the hypothesis that oribatid mites are microhabitat specific in old-growth Douglas fir, Western hemlock and western redcedar at the Wind River Crane Canopy Research Facility, Washington, USA. The upper 3 m of canopy of the three tree species were accessed using the canopy crane. Oribatida were extracted from 4 to 12 g dwt samples of alecterioid and foliose lichens using the twig-washing technique. Overall species richness was low, 16 species representing 11 families, with no species unique to this site. Species were absent from samples taken contemporaneously from the forest floor. All oribatid species were found in foliose lichens, whereas only nine species, in seven families, were recovered from alecterioid lichens. Oribatid species richness was lichen specific depending on the tree species. On Western hemlock both lichens supported similarly rich communities, but on Douglas fir and western redcedar foliose lichens supported the richer community.     

Little effect of forest age on oribatid mites on the bark of trees

This study investigates the effect of forest age (20-, 50-, 160-year-old, and primeval forest) on oribatid mite communities on the bark of oak trees in the National Park Pusza Białowieża in eastern Poland. We hypothesized that oribatid mite diversity on bark peaks at forests of intermediate age and that the number of parthenogenetic species of oribatid mites is highest in young stands. In contrast to these hypotheses, the diversity, density, number of juveniles, community structure and the mode of reproduction of oribatid mite species were not significantly affected by forest age. None of the oribatid mite species occurred exclusively on trees of a specific age. The results suggest that oribatid mite communities on the bark of trees are minimally affected by tree harvesting regimes. In contrast to oribatid mites in soil, communities on bark appear to be less sensitive to disturbances.     

Trophic structure of oribatid mite communities from six different oak forests (Quercus robur)

The degree of trophic plasticity in soil animals is intensely debated. We used stable isotope ratios (¹⁵N/¹⁴N, ¹³C/¹²C) of oribatid mite species from six oak (Quercus robur) forests to investigate (1) if trophic niches vary between forests and (2) the range of trophic levels spanned by oribatid mites. Using litter as baseline stable isotope signatures of most oribatid mite species differed between forests. Therefore, the stable isotope signatures were re-calibrated using stable isotope values of Platynothrus peltifer as primary decomposer species occurring in each of the six forests. Re-calibrated values of nine species (Cerachipteria jugata, Damaeus clavipes, Neotrichoppia variabilis, Oppia denticulata, Hermaniella dolosa, Steganacarus magnus, Ceratozetes peritus, Nanhermannia nana, Xenillus tegeocranus, Eremaeus cordiformis) differed significantly between forests indicating trophic plasticity in most of the studied oribatid mite species. Overall, calibrated stable isotope ratios spanned over 8.7 δ units for ¹⁵N and 5.9 δ units for ¹³C indicating that in forest ecosystems oribatid mite species span about three trophic levels.     

A comparison of microarthropod assemblages with emphasis on oribatid mites in canopy suspended soils and forest floors associated with ancient western redcedar trees

Microarthropod abundance, oribatid mite species richness and community composition were assessed in the high canopy (ca. 35 m) of an ancient temperate rainforest and compared with microarthropod communities of the forest floor. Microarthropods were extracted from 72 core samples of suspended soils and 72 core samples from forest floors associated with six western redcedar trees in the Walbran Valley on the southwest coast of Vancouver Island, Canada. Total microarthropod abundances, mesostigmatid and astigmatid mites, Collembola and other microarthropod abundances were significantly greater in forest floors compared to canopy habitats. Oribatid and prostigmatid mite abundance were not significantly different between habitats. The relative abundances of all microarthropod groups considered in this study differed significantly between habitats. Eighty-eight species of oribatid mites were identified from the study area. Eighteen of the 53 species observed in suspended soils were unique to the canopy. Cluster analysis indicates that the arboreal oribatid mite community is distinct and not a taxonomic subset of the forest floor assemblage, however, canopy oribatid mite communities are more heterogeneous in species composition than in the forest floor.     

Reactions to soil acidification in microarthropods: Is competition a key factor?

Summary Acidification of raw humus soil in coniferous forest areas leads to characteristic changes in the microarthropod community. Certain species are calciophilic and decrease in abundance, while others are acidophilic and increase in abundance. The simplest explanation for these changes is that population levels are directly related to soil pH. This hypothesis was tested by growing small populations of selected species in monoculture at different pH levels. Three acidophilic species were tested, the collembolan Mesaphorura yosii, the oribatid mite Nothrus silvestris, and the astigmatid mite Schwiebea cf. lebruni. A slightly calciophilic collembolan, Isotomiella minor, was also included. For all species, population growth was lowest in acidified raw humus. Even acidophilic species seem to have an optimum at a high pH. It is assumed that their success in low-pH soils is due to their ability to compete under these conditions. Competition may be a key factor in microarthropod reactions to soil acidification.Dedicated to the late Prof. Dr. W. Kühnelt     

Stable isotopes revisited: Their use and limits for oribatid mite trophic ecology

In this review we summarize our knowledge of using stable isotopes (¹⁵N/¹⁴N, ¹³C/¹²C) to better understand the trophic ecology of oribatid mites. Our aims are (a) to recapitulate the history of stable isotope research in soil animals with a focus on oribatid mites, (b) to present new stable isotope data for oribatid mites and overview the current state of knowledge of oribatid mite trophic niche differentiation, (c) to compile problems and limitations of stable isotope based analyses of trophic relationships and (d) to suggest future challenges, questions and problems that may be solved using stable isotope analyses and other novel techniques for improving our understanding on the trophic ecology of soil invertebrates. We conclude that (1) in addition to ¹⁵N/¹⁴N ratios, ¹³C/¹²C ratios contribute to our understanding of the trophic ecology of oribatid mites, allowing, e.g. separation of lichen- and moss-feeding species, (2) there likely are many lichen but few moss feeding oribatid mite species, (3) oribatid mite species that are endophagous as juveniles are separated by their stable isotope signatures from all other oribatid mite species, (4) fungivorous oribatid mite species cannot be separated further, e.g. the fungal taxa they feed on cannot be delineated. A particular problem in using stable isotope data is the difficulty in determining signatures for basal food resources, since decomposing material, fungi and lichens comprise various components differing in stable isotope signatures; ¹³C/¹²C ratios and potentially other isotopes may help in identifying the role of these resources for decomposer animal nutrition.     

Spruce forest conversion to a mixed beech-coniferous stand modifies oribatid community structure

We investigated oribatid mite community diversity and structure in the managed conversion of coniferous stands into semi-natural montane forests that are composed of a small-scale mosaic formed by different age classes of silver fir, Norway spruce and European beech in the southern Black Forest area, South-Western Germany, using the space-for-time substitution method. The core hypothesis was that changing tree composition and management practice will affect functional structure and diversity of oribatid mite community through changing substrate quality and litter diversity. Three forest districts were selected within the research region. Four stand types representing the major stages of forest conversion were selected within each forest district: (i) even-aged spruce monocultures, (ii) species enrichment stage, (iii) forest stand structuring stage, at which fur and beech and other deciduous trees penetrate the upper storey of the forest and (iv) a diverse continuous cover forest respectively. Oribatid mite abundance, species richness and composition, biomass, ecomorphs and feeding groups relative abundance were determined. An overall increase in species richness moving from the spruce monoculture to a continuous cover forest was detected. However, the herbivorous and litter-dwelling mites were most sensitive to forest conversion demonstrating significant differences in abundance between conversion stages. Almost all changes in the oribatid community were associated with the properties of the changing litter layer. Abundance of soil-dwelling mites remained very stable what is in contradiction with the response of the other soil fauna groups found at the same sites. Overall oribatid community seemed to be more dependent on total microbial biomass than fungi. However, observed effects were overshadowed by considerable district-induced differences.     

Changes in the community composition and trophic structure of microarthropods in sporocarps of the wood decaying fungus Fomitopsis pinicola along an altitudinal gradient

Soil microarthropods colonize a wide range of habitats including microhabitats such as earthworm burrows, ant nests, tree trunks, moss mats and wood decaying fungi. While many of these microhabitats have been investigated intensively, the role of wood decaying fungi as a habitat and food resource for microarthropods found little attention. We investigated the density, community structure, reproductive mode and trophic structure of microarthropods, in particular oribatid mites, in the wood decaying fungus Fomitopsis pinicola (Schwarts: Fr) Karst. along an altitudinal gradient in Germany spanning from 350 m to 1160 m. Microarthropods were extracted from sporocarps, and stable isotope ratios (¹⁵N/¹⁴N; ¹³C/¹²C) of the fungus and the microarthropods were measured. Densities of most microarthropod taxa were highest at lower altitudes and decreased with increasing altitude. Oribatid mites were the dominant animal taxon. Their community structure gradually changed with altitude. Stable isotope ratios indicated that oribatid mite and other arthropod species occupy distinct trophic niches but most do not feed on F. pinicola. Notably, species of the same genus, e.g. Carabodes, occupied different trophic niches. Most oribatid mite species in F. pinicola reproduced sexually which is similar to the bark of trees but in contrast to the soil where most species reproduce via parthenogenesis. The findings indicate that (1) at high altitudes microarthropod density in fungal fruiting bodies is limited by low temperatures reducing animal metabolism and reproduction, and this also affects oribatid mite community structure, (2) despite the uniform habitat trophic niches of oribatid mite species differ and this also applies to morphologically similar species of the same genus, and (3) feeding on F. pinicola or associated resources facilitates the dominance of sexual reproducing species.     

Do oribatid mites (Acari: Oribatida) show a higher preference for ubiquitous vs. specialized saprotrophic fungi from pine litter?

Previous studies of oribatid mite feeding preferences for different saprotrophic fungi were limited to ubiquitous fungal species, whereas saprophytes specialized to decompose particular substrates have been neglected. We examined the preference of seven oribatid mite species (Adoristes ovatus, Eniochthonius minutissimus, Eueremaeus silvestris, Nothrus silvestris, Oppiella subpectinata, Porobelba spinosa and Spatiodamaeus verticillipes) for nine autochthonous saprotrophic fungi from Scots pine litter (Pinus sylvestris). Among the fungal species offered were specific coniferous litter colonizers (Allantophomopsis lycopodina, Ceuthospora pinastri, Hormonema dematioides, Scleroconidioma sphagnicola, Verticicladium trifidum, Marasmius androsaceus and Sympodiella acicola) and two ubiquitous species (Cladosporium herbarum and Oidiodendron griseum). The fungi were inoculated on fragments of pine needles and offered simultaneously and separately to the mites. Our main hypothesis, that oribatid mites (usually occurring in more than one type of ecosystems) would prefer the ubiquitous fungal species rather than those specific to pine litter, was supported only partly. The ubiquitous C. herbarum was highly preferred by all studied mites, but most of them preferred one or more of the specialized fungi with similar intensity. The basidiomycete M. androsaceus along with sterile needles were consistently avoided by all mites in all experiments. Our results do not support the hypothesis, that the “true” fungivorous oribatid mites in traditional sense are more selective fungal feeders than are the “unspecialized” panphytophagous ones. We observed no gradation in preference of fungi for oribatid mites as a group, but rather a discontinuous and dynamic mosaic with particular mites preferring particular fungal species. This heterogeneous mosaic shapes the feeding niches occupied by particular oribatid mite species and probably reduces competition for food source among numerous species coexisting in a given habitat and time.     

Oribatid mite community structure and tree species diversity: A link?

Differences in tree species may lead to contrasting soil environments via differences in litter chemical quality and physical environmental factors, such as soil type and soil moisture. However, separating the effects of litter quality and physical environment is difficult under field conditions. Both litter quality and soil environment affect the species composition of the soil animal community. A diversity gradient of canopy tree species (11–25 species) located on homogeneous soil substrate at Tomakomai Experimental Forest of Hokkaido University was used to analyse the relationship between tree species diversity and oribatid mite community structure. Soil samples were collected from three levels of tree species richness (high, intermediate and low) with three replicates each, in July 2000. Leaf area index (LAI) was positively correlated with tree species diversity suggesting higher litter input into the soils with increasing tree diversity. However, the tree species diversity gradient affected neither accumulation of litter on the forest floor nor abundance and species richness of oribatid mites. Canopy and understory plant species richness, LAI, total soil carbon and biomass of epigeic and endogeic earthworms did not significantly affect mite community structure as indicated by redundancy analysis (RDA). The results suggest that oribatid mite community structure is minimally affected by tree species diversity and associated changes in litter diversity.     

Speciation in the parthenogenetic oribatid mite genus Tectocepheus (Acari, Oribatida) as indicated by molecular phylogeny

Despite the lack of universal concepts for species and speciation, both sexual and asexual organisms are expected to diversify into discrete genotypic and morphological clusters. Species-rich clusters of parthenogenetic oribatid mites likely evolved in the absence of sexual reproduction. We used nucleotide sequences of the large and small rDNA genes (18S and 28S) and the coding genes for heat shock protein 82 (hsp82) and elongation factor-1 alpha (ef-1α) for phylogenetic analyses of three morphotypes of the parthenogenetic oribatid mite genus Tectocepheus. DNA sequence divergences of the different morphotypes were similar to those of sexual species in other organisms. Maximum likelihood analyses of single genes and combined data sets were largely congruent in reconstructing the phylogeny of the Tectocepheus species. The results suggest that the different morphotypes of Tectocepheus indeed evolved in the absence of sexual reproduction, and that Tectocepheus minor, Tectocepheus velatus and Tectocepheus sarekensis are best considered distinct species. Further, the results suggest that 18S rDNA, hsp82 and ef-1α are powerful markers for resolving phylogenetic relationships of oribatid mites. Saturation plots indicated that the D3-region of 28S is much more saturated than all other examined genes. This indicates that the D3-region is unsuitable for resolving ancient splits in oribatid mites.     

Oribatid mite communities and foliar litter decomposition in canopy suspended soils and forest floor habitats of western redcedar forests, Vancouver Island, Canada

Litter decomposition and changes in oribatid mite community composition were studied for 2 years in litterbags collected from arboreal organic matter accumulations (canopy suspended soils) and forest floors associated with western redcedar trees on Vancouver Island, British Columbia. We tested the hypotheses that lower rates of mass loss, higher nutrient levels, and different patterns of oribatid mite richness and abundance in decomposing western redcedar litter would be observed in litterbags associated with canopy suspended soils compared to forest floors. Decomposition, measured by mass loss of cedar litter in litterbags, was not significantly different in canopy and forest floor habitats, although reduced in the canopy. Abundance and richness of oribatid mites inhabiting litterbags were significantly greater on the forest floor compared to the canopy suspended soils. Canopy suspended soils had higher levels of total nitrogen, available phosphorus and potassium than the forest floor, but moisture content was significantly lower in the suspended soils. Higher nutrient levels in the canopy system are attributed to differences in coarse woody debris input (but not foliar litter), combined with reduced nutrient uptake by roots and lower mobilisation rates of nutrients by detritivorous and fungivorous microarthropods. Moisture limitation in the canopy system possibly contributed to lower mass loss in litterbags, and lower abundance and richness of oribatid mites in litterbags placed on canopy suspended soils. Patterns of oribatid mite community composition were related to mite communities associated with the underlying substrate (forest floor or canopy suspended soil) which act as source pools for individuals colonising litterbags. Successional and seasonal trends in oribatid mite communities were confounded by moisture limitation at 24 months, particularly within the canopy habitat.     

Do oribatid mites live in enemy-free space? Evidence from feeding experiments with the predatory mite Pergamasus septentrionalis

To examine whether their strongly hardened cuticle permits adult oribatid mites (Acari) to live in enemy-free space, we investigated (1) if Pergamasus septentrionalis, a widespread and abundant predatory mesostigmate mite species, is able to feed on oribatid mites, (2) if this predator preferentially feeds on certain oribatid mite species and (3) to what extent oribatid mites are consumed compared to collembolans and juvenile Mesostigmata. Single adult individuals of six different oribatid mite species (Steganacarus magnus; Nothrus silvestris; Damaeus riparius; Liacarus coracinus; Eupelops plicatus; Achipteria coleoptrata), one collembolan species (Folsomia quadrioculata) and juvenile Pergamasus spp. were offered separately to adult P. septentrionalis in a no-choice feeding experiment. The predators quickly and preferentially fed on collembolans and juvenile Pergamasus; three oribatid mite species were occasionally eaten (L. coracinus, N. silvestris, A. coleoptrata); the other oribatid mite species were rejected as food (E. plicatus, S. magnus, H. riparius). When preying on oribatid mites, P. septentrionalis typically first cut off the legs of the mite, then opened the body through the region of the genital plates or the mouthparts. The results suggest that predator pressure on adult oribatid mites in the field is low, since few relevant predators at the study site are more abundant and powerful than P. septentrionalis. Adult oribatid mites therefore likely indeed live in enemy-free space, i.e. are little affected by predators, but that may not apply to soft-bodied immatures. Collembolans were quickly consumed indicating that they comprise a major part of the diet of P. septentrionalis. Strong feeding on juveniles of Pergamasus suggests that P. septentrionalis also functions as an intra-guild predator.     

Climatic and litter fall effects on collembolan and oribatid mite species and communities in a beech wood based on a 7 years investigation

During a period of 7 years, between 1989 and 1995, Collembola and Oribatida were investigated in a beech forest on an acid Dystric Cambisol soil in northern Germany. Precipitation and temperature at a nearby climate station were recorded, and litter fall in the forest was measured. For 23 collembolan and 27 oribatid mite species, an analysis was performed concerning the influence of the climate parameters or litter fall on yearly assemblages or single species. Climate influence on the community structure was weak. Composition of the assemblages was relatively constant throughout the period of 7 years. A significant effect was determined for mean annual temperature and July precipitation only. More distinct effects were found in single species. In total, nine collembolan and six oribatid mite species were significantly influenced by litter fall, mean annual temperature, mean January temperature, mean July temperature, total precipitation or July precipitation. Reaction time ranged between 1 and 12 months. Four collembolan species reacted with a retarded yearly occurrence on deep spring temperature. Species diversity of Collembola was negatively correlated with total litter fall, while in oribatid mites the diversity showed a positive correlation.     

Differential effects of lichens and mosses on soil enzyme activity and litter decomposition

In the New Jersey Pinelands, canopy gaps in the pine-dominated forest support patches of lichens, mosses, and caespitose grasses. We tested the hypotheses that non-vascular plants and lichens can affect nutrient cycling processes and that mosses and lichens would differ from each other. We predicted that (1) lichen tissues would decompose more slowly than pine or moss tissues, (2) all plant materials would decompose more slowly beneath lichens than beneath mosses, and (3) soil enzyme activities would be higher under lichens than under mosses or grasses, reflecting greater nutrient limitation. We compared rates of decomposition of the litter of Pinus rigida and moss and lichen tissues, and measured soil enzyme activities responsible for nutrient mineralization from litter (acid and alkaline phosphatases, chitinase, β-glucosidase, aminopeptidase, and phenol oxidase) under three types of groundcover (lichens, mosses, and grasses) and unvegetated soil at two sites. While groundcover affected enzyme activities, the patterns of enzyme activities differed markedly between the two sites. In general, the enzyme activities were uniformly low. Decomposition rates were more strongly affected by the groundcover than by litter materials. While all litters tended to decompose more slowly under lichens than under mosses, supporting one of our initial hypotheses, the rates of decomposition were markedly different between the two sites. These results suggest that while mosses and lichens create patches of different soil function in both sites, the differences between the sites in unknown factors cause the enzyme activities and decomposition rates to differ.     

Species diversity and metal accumulation in oribatid mites (Acari, Oribatida) of forests affected by a metallurgical plant

A study was made of oribatid mite communities and their responses to metal contamination derived from the Kosogorsky metallurgical plant located in the Tula District, Russia. Mite communities were sampled in three different seasons in four sites at different distances from the smelter. Concentrations of zinc, copper, cadmium, lead and iron were measured in ten mite species. The data show that the mite community as a whole is quite tolerant to the metal contamination caused by the Kosogorsky plant. At the polluted sites some species typical for nutrient-rich soils appeared, but community structure and species diversity were not seriously affected by metal contamination. In general, oribatid mites accumulated metals to very high internal concentrations. Average Cu, Cd, Pb and Fe concentrations did not differ significantly between species, but Zn did, and its level was associated with the mode of feeding of the species. Microphytophagous species, feeding exclusively on fungi, accumulated zinc in higher concentrations than other mites. This study illustrates the potential for bioindication by the little studied but species-rich group of soil oribatids.     

Responses of co-occurring populations of Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) to soil pH, moisture and resource addition

Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) are the two most dominating soil invertebrates in terms of biomass in boreal coniferous forest soils. A microcosm experiment was set up in order to study the influence of pH, moisture and resource addition on D. octaedra and C. sphagnetorum when both species are simultaneously present. Two kinds of coniferous forest humus were used as substrate, pine stand humus (pH 4.2), and spruce stand humus (pH 4.6); in the third treatment the pine stand humus was adjusted with slaked lime (CaOH₂) to the same initial pH as the spruce stand humus. Each substrate was adjusted to water contents of 25%, 42.5% and 60% of WHC (referred to as ‘dry’, ‘moist’ and ‘wet’). In the second part of the experiment, spruce needle litter and birch leaf litter were separately added into the pine stand humus (‘moist’, unlimed) and compared with a control without litter. The microcosms were plastic jars with 75 g (d.m.) of humus, into which 4 specimens of D. octaedra and 70 specimens of C. sphagnetorum were added. D. octaedra showed the highest biomass and C. sphagnetorum the lowest biomass in the spruce stand humus with higher pH. Moisture did not affect earthworms, while C. sphagnetorum thrived best at the highest moisture. Addition of both kinds of litter increased the numbers and biomass of D. octaedra, while on C. sphagnetorum resource addition had little effect. The results help to explain the abundance of these two species in coniferous forests differing in soil acidity, moisture and fertility.     

Responses of oribatid mite communities to summer drought: The influence of litter type and quality

A litterbag experiment was used to study the impact of extended periods of summer drought on the structure of oribatid mite communities (Acari, Oribatida) developing in two litter types (beech, spruce) of two qualities (fresh, pre-incubated). Within each litter type, litter quality determined species composition and densities and, in turn, this determined the impact of drought upon the oribatid mite communities. In both litter types, drought had a greater impact on community development in the pre-incubated compared to the fresh litter. In the short-term perspective of the present study, oribatid mite communities in beech litter were less sensitive to summer drought than those in spruce litter. This was partly due to the presence of site-specific, drought-tolerant species but seemed also strongly related to differences in the decomposition patterns between the litter types. Marked changes in densities and composition of oribatid communities after only one period of summer-drought suggest that there is a potential for a significant alteration of oribatid community structure in both litter types if climatic changes persist.     

Molecular detection of nematode predation and scavenging in oribatid mites: Laboratory and field experiments

Recent stable isotope analyses indicate that a number of putative detritivorous soil microarthropods is not typical detritivores but rather live as predators or scavengers. Using molecular gut content analyses the present study investigates if nematodes indeed form part of the diet of oribatid mites. First, in a no-choice laboratory feeding experiment two nematode species (Phasmarhabditis hermaphrodita and Steinernema feltiae) were offered to eight species of oribatid mites and one gamasid mite. Second, after feeding for 4 and 48 h on each nematode species the detection time of prey DNA in the oribatid mite species Steganacarus magnus was investigated. Third, in a field experiment nematode prey (P. hermaphrodita and S. feltiae) in the diet of microarthropods was investigated distinguishing between scavenging and predation. In the no-choice laboratory experiment not only the gamasid mite but also several of the studied oribatid mite species consumed nematodes. After feeding on nematodes for 4 h prey DNA was detectable in S. magnus for only 4 h, but after feeding for 48 h prey DNA was detectable for 128 h, indicating that the duration of feeding on prey is an important determinant for prey DNA detection. The field experiment confirmed that oribatid mite species including Liacarus subterraneus, Platynothrus peltifer and S. magnus intensively prey on nematodes. Interestingly, DNA of dead P. hermaphrodita was detectable to a similar degree as that of living individuals indicating that scavenging is of significant importance in decomposer food webs. Results of our study indicate that predation and scavenging on nematodes by “detritivorous” microarthropods in soil food webs need to be reconsidered.