Soil Mite Communities Research Articles

Relative roles of spatial factors, environmental filtering and biotic interactions in fine-scale structuring of a soil mite community

Community theories suggest that community structuring depends on dispersal limitation, environmental filtering and biotic interactions. However, the relative roles of these factors at fine scale are less well understood. In this study, we attempt to determine the relative roles of spatial factors, environmental filtering and biotic interactions in the fine-scale (5 m) structuring of a soil mite community from a temperate deciduous forest in the Maoershan Ecosystem Research Station in northeastern China. In August 2012, we established three plots and collected 100 samples from each plot in a 5 × 5 m2 area using a spatially delimited sampling design. To quantify the relative contributions of the spatial and environmental processes, Moran's eigenvector maps (MEMs), variation partitioning analysis and partial Mantel test were used. Null and neutral models were used to disentangle the effects of biotic interactions. Null mode analyses were conducted for non-random patterns of species co-existence and significant species-pairs in the assemblage of soil mites, and to determine whether the observed pattern was the result of biotic interactions. The neutral model was used to identify whether the community structure shows divergence, convergence or neutrality. The results indicated that the relatively large and significant variance was due to spatial factors in all plots. The contribution of environmental filtering was relatively low and non-significant in all plots based on variation partitioning, while it was significant in Plot II based on a partial Mantel test. Soil organic matter content, soil pH, and soil and litter water content explained a significant part of the variance observed in the distribution of the mite community. Furthermore, the null model revealed a non-random co-occurrence pattern in the soil mite community, and the environmental niche overlap indicated a weak contribution of biotic interactions. The observed mean dissimilarity implied significant divergence in communities based on neutral model analysis. Collectively, these results emphasize that both spatial and environmental processes were important drivers in the fine-scale structuring of soil mite communities in a temperate deciduous forest and that biotic interactions were less influential in the observed pattern.

The specific responses of Acari community to Bt cotton cultivation in agricultural soils in northern China

Transgenic cotton expressing the Bacillus thuringiensis (Bt) insecticidal crystal (Cry1A) protein effectively controls the cotton bollworm and thus has been planted extensively in China. However, the large-scale release of Bt cotton may have undesirable effects on soil fauna due to Bt protein accumulation and the pleiotropic effects of genetic manipulation. A survey of soil mites was carried out monthly for two consecutive years (2009–2010) in Bt and non-Bt cotton fields. The soil mites were extracted using modified Tullgren funnels and were identified to the genus level, when possible. The results suggested that the effects of Bt cotton on soil mite community size were time dependent and taxonomic group specific. The cumulated abundance over a year was always higher in non-Bt fields for Oribatida; this effect was statistically significant in 2010 for Prostigmata and Astigmata. The changes in the community variables tested were similar between Bt and non-Bt cotton fields in 2009, whereas the taxonomic group richness, Shannon–Weaver index and evenness index were significantly different between Bt and non-Bt cotton fields in 2010. Additionally, sharp inter-annual fluctuations in the community composition of the soil mites were found, accompanied with the replacement of some taxonomic groups. Finally, the dominances of some taxonomic groups were significantly different between Bt and non-Bt cotton fields. Bt cotton cultivation fostered Laelapidae populations while inhibited Tectocepheus abundance in 2009. However, Bt cotton cultivation negatively impacted the abundances of Scheloribates and Nothrus in 2010. In conclusion, Bt cotton cultivation exerted specific impacts on soil mites.

Diversity of soil mite communities (Acari) within habitats seasonally flooded by the Vistula River (Ostromecko, Poland)

Abstract The research was carried out in three types of habitats located in the seasonally flooded area of the Vistula River within Wielka Kępa Ostromecka Reserve: Salicetum albo-fragilis, Fraxino-Alnetum and Populetum albae. In the soil of Salicetum albo-fragilis Veigaia nemorensis and Trichouropoda ovalis were abundant, while Fraxino-Alnetum was dominated by Rhodacarellus silesiacus, and Populetum albae was overwhelmed by Rhodacarellus silesiacus and Dinychus inermis. Only between the Mesostigmata communities populating Fraxino-Alnetum and Populetum albae there were no statistically significant differences recorded in the distribution of abundance. The most similar, from the qualitative, quantitative and qualitative-quantitative point of view were Mesostigmata communities inhabiting Fraxino- Alnetum and Populetum albae. The numerous occurrence of Rhodacarellus silesiacus population in the soil of Fraxino-Alnetum and Populetum albae is most probably the result of succession changes within those habitats, and the species itself can be seen as an indicator of those habitats undergoing the process of a riparian forest transforming into an oak-hornbeam forest vegetation type.

Community structures of Mesostigmata, Prostigmata and Oribatida in broad-leaved regeneration forests and conifer plantations of various ages

The community structures of Mesostigmata, Prostigmata, and Oribatida in the soil of broad-leaved regeneration forests and conifer plantations of various ages were assessed alongside soil and plant environmental variables using three response metrics (density, species richness, and species-abundance distribution). The density and species richness of mites recovered swiftly after clear-cutting or replanting. Oribatid mites dominated the soil mite communities in terms of densities and species richness for both forest types. Soil mite communities in broad-leaved forests was related to forest age, the crown tree communities index, and forest-floor litter weight. In contrast, soil mite communities in the conifer plantation sites were related to various indices of understory plants. The development of the understory plants was synchronized with the silvicultural schedules, including a closed canopy and thinning. Such a conifer plantation management may affect indirectly the community of mites.

Changes in the abundance and structure of a soil mite (Acari) community under long-term organic and chemical fertilizer treatments

A study was conducted in an 11-year field experiment in a winter wheat–summer maize rotation agroecosystem in the North China Plain. We aimed to evaluate the changes in soil physico-chemical parameters and the abundance, diversity and community structure of soil mites, under organic fertilizer (OF) and chemical fertilizer (CF) treatments, compared to unfertilized soil as the control (U). Soil organic matter content, available potassium (K), total nitrogen (N) and hydrolyzable N were significantly higher in the plots under the OF treatment than under the other treatments. Available phosphorus (P) content was similar in OF and CF plots and higher than in the control. After continuous 11-year application, both the organic and chemical fertilizer treatments reduced the abundance and diversity of soil mites. Both types of fertilizer significantly reduced the abundance of Oribatida such as Epilohmannia sp., Xylobates sp., Scheloribates sp., and Cultroribula sp. This result was positively related to the high level of phosphorus in the two treatments, which probably suppressed fungi, thus reducing the food resources for mycophagous mites. However, the organic fertilizer remarkably increased the abundance of r-strategic, predatory Mesostigmata, such as Ascidae, possibly due to abundant prey under the nutrient-rich conditions. However, the number of predatory mites did not increase in the chemical fertilizer treatment. While organic fertilizer application did not increase the overall abundance and diversity of soil mites, especially Oribatida, parallel studies (unpublished) show that the increase in predatory Mesostigmata reflected enhanced biological activity and functioning of the bacterial decomposition pathway especially in the food web of this treatment.

DOES PLANT SPECIES CO-OCCURRENCE INFLUENCE SOIL MITE DIVERSITY?

Few studies have considered whether plant taxa can be used as predictors of belowground faunal diversity in natural ecosystems. We examined soil mite (Acari) diversity beneath six grass species at the Konza Prairie Biological Station, Kansas, USA. We tested the hypotheses that soil mite species richness, abundance, and taxonomic diversity are greater (1) beneath grasses in dicultures (different species) compared to monocultures (same species), (2) beneath grasses of higher resource quality (lower C:N) compared to lower resource quality, and (3) beneath heterogeneous mixes of grasses (C3 and C4 grasses growing together) compared to homogeneous mixes (C3 or C4 grasses) using natural occurrences of plant species as treatments. This study is the first to examine the interaction between above- and belowground diversity in a natural setting with species-level resolution of a hyper-diverse taxon. Our results indicate that grasses in diculture supported a more species and phylogenetically rich soil mite fauna than was observed for monocultures and that this relationship was significant at depth but not in the upper soil horizon. We noted that mite species richness was not linearly related to grass species richness, which suggests that simple extrapolations of soil faunal diversity based on plant species inventories may underestimate the richness of associated soil mite communities. The distribution of mite size classes in dicultures was considerably different than those for monocultures. There was no difference in soil mite richness between grass combinations of differing resource quality, or resource heterogeneity.

The community characteristics of soil mites under different land uses in Changchun metropolitan area, China

Soil mites were investigated under different land uses in Changchun metropolitan area (Jilin Province, China). The soil mites were extracted using modified Tullgren funnels and were identified to the genus level. A total of 8 703 soil mites belonging to 92 genera were found. The community characteristics of soil mites were analyzed using individual density, number of taxon, diversity, abundance, and evenness as well as MGP analysis and the MI index. Litter removal considerably decreased the numbers of soil mite taxon, abundance and diversity, and tillage changed the vertical distribution of soil mite individual density in the soil profile and accelerated their move to lower soil layers. The results suggest that the land-use types significantly affect the community structures of soil mites, and litter removal and conventional cultivation are the main factors in play. The studies also suggest that the type of vegetation above ground appears to have little influence on the ecological structures of the soil mite community.

Diversity of soil mite communities when managing plant communities on set-aside arable land

When restoring former agricultural land to more low-nutrient input ecosystems, the establishment of a plant community can be enhanced by sowing desirable species. In this study our aim was to determine whether management of the plant community influences the microarthropod community. We carried out a field experiment in three European countries on set-aside arable land and determined soil mites from the sites in Sweden, The Netherlands and Spain. Experimental plots on set-aside arable land were sown with high (15 species) or low (4 species) plant species seed mixtures; other plots were colonized naturally. A field with continued agricultural practices and a later successional site (target site) were used for comparison with the experimental plots. Soil from the later successional site was inoculated into half of the plots. Abandoning agricultural practices increased the density of mites at one site while the number of mite species was not affected. Sowing plant seeds had no effect on mite densities at any of the sites. The community composition of mites changed in response to management of the plant community, as shown by canonical correspondence analysis. Among the functional groups of mites, saprophytes generally dominated on all plots at all sites. Mites parasitic on insects were not present on fields with continued agricultural practice in Sweden and The Netherlands, and might thus be regarded as an indicator of an increase in trophic complexity in the sown and naturally colonized treatments. Predatory and plant parasitic mites showed no consistent pattern in relation to the treatments of the three sites. Soil inoculation treatment had only a minor impact on the soil mite communities.

Communities of soil mites (Acarina) in planted birch stands compared with natural forests in central Finland

The aim of the study was to compare the soil mite communities in anthropogenous birch stands of different origin with each other and with natural forests at the same latitude. Nine sites were investigated: three birch stands (Betula pendula Roth) planted ca. 30 years prior to the study after clear-cutting of spruce stands ("birch after spruce"), three birch stands planted ca. 30 years earlier on arable soil that had been under cultivation until reforestation ("birch after field"), and three natural deciduous forests. These were sampled twice, and microarthropods were extracted, counted, and identified. There were clear differences between birch stands established after spruce forest and after cultivation and between these and natural deciduous forests. The communities of birch after spruce were rather similar to those of natural spruce forests, but the population densities were lower. The populations in birch after field were generally very low. There were also conspicuous differences among replicates of the same kind of forests. All the dominant species in the study sites are common members of the forest soil fauna. The communities of birch after field could be characterized as impoverished forest communities. Soil pH and the removal of the litter layer by earthworms were regarded as the most important factors explaining the observed differences.

Structure of soil mite (Acari) communities in urban green of Warsaw.

Structure of soil mite (Acari) communities in urban green of Warsaw.