Soil Microarthropod Community Structure Research Articles

The Effect of Bean Seed Treatment with Entomopathogenic Fungus Metarhizium robertsii on Soil Microarthropods (Acari, Collembola).

Simple SummaryPlant pest control is essential for agriculture. The treatment of agricultural crops with entomopathogenic fungi protects plants against pests and can also increase plant growth, but at the same time may disturb the community structure of non-target beneficial invertebrates, in particular soil microarthropods. This can have a negative impact on soil fertility and ultimately on crop yields. The effect of the treatment of broad bean (Vicia faba L.) seeds, with the entomopathogenic fungus Metarhizium robertsii, on the abundance and structure of soil microarthropod communities in the rhizosphere was assessed. Compared with the control, no adverse effect was revealed on both the abundance of soil microarthropods, including mites (Mesostigmata, Oribatida, Astigmata, Prostigmata) and springtails (Collembola), and the structure of microarthropod communities. Therefore, dressing seeds with a conidial suspension for plant inoculation, with entomopathogenic fungi (at least M. robertsii), can be assumed as a potentially safe method of plant protection for soil microarthropods.The treatment of agricultural crops with entomopathogenic fungi may disturb the structure of soil microarthropod communities, which can have an adverse impact on soil fertility and, ultimately, on the yield. The effect of the treatment of broad bean (Vicia faba L.) seeds, with the entomopathogenic fungus Metarhizium robertsii, on the abundance and community structure of soil microarthropods in the rhizosphere was assessed in different phases of plant vegetation in a two-year experiment. Under the conditions of the gradually decreased abundance of M. robertsii both in the soil cenoses and in the plants during summer, no adverse effect was revealed of the bean seed treatment, with the entomopathogenic fungus, on the abundance of soil microarthropods (Acari: Mesostigmata, Prostigmata, Oribatida and Astigmata; Collembola) and the structure of their communities. Similar results were obtained in the analysis, taking into account the positive colonization of plants. Some changes in the microarthropod community structure were explained primarily by the spatial heterogeneity of the field, the hydrothermal regime, and the features of the microarthropod life cycles. The results indicate the possibility of using dressing seeds with conidial suspension for plant inoculation with entomopathogenic fungus (at least M. robertsii) as a potentially safe plant protection method for non-target soil microarthropods.

Effects of cultivating Coptis chinensis and Paris polyphylla on soil microarthropod communities.

In recent years, the area of herbal medicine planting is rapidly increasing. The effects of planting herbal medicines on soil invertebrate communities are still unclear. To reveal the effects of planting different herbal medicines on the soil microarthropod communities, soil microarthropods in two fields of planting Coptis chinensis and Paris polyphylla for 3-year and 5-year, respectively, were investigated in Pengzhou, Chengdu in July 2020. A total of 526 individuals of soil microarthropods were recorded and classified into 4 classes, 17 orders, 69 families, and 98 genera or taxonomic groups. The communities were dominated by Isotoma, Piatynothrus, Folsomia, and Paranura. The community structure of soil microarthropods differed obviously among the two herbal medicine fields, with the main influencing taxonomic groups of Proisotoma, Ocesobates and Epicridae. The total taxonomic group richness of soil microarthropods were richer in C. chinensis field than P. polyphylla field. There was no significant difference in the abundance and diversity index between the two fields. With the increases of cultivating years, the abundance of soil microarthropods in C. chinensis field declined significantly, and Shannon index increased significantly in P. polyphylla field. The redundancy analysis showed that the community structure of soil microarthropods was mainly affected by soil available N, pH, total K, and available K. It suggested that the effects of cultivating herbal medicines on soil microarthropod communities differed between herbal medicine species. Therefore, we recommended to intercrop C. chinensis and P. polyphylla for maintaining the stability of soil microarthropod diversity and promoting ecosystem function.

Communities of Soil Microarthropods (Acari, Collembola) at Ash Dumps of a Combined Heat and Power Plant at Different Degrees of Conservation

The features of the composition and structure of soil microarthropod communities that are formed at ash dumps of a combined heat and power plant (CHPP) at the initial stages of their self-restoration at different degrees of conservation are studied. The research was carried out in 2017 in Novosibirsk (55°00′ N, 83°04′ E) at the ash dump of CHPP no. 5 consisting of two sections: the nonreclaimed section (S1) and the section reclaimed by covering ash and slag with potentially fertile soil (S2). A plot in a birch forest adjacent to the ash dump was used as a control. The material was collected in ash-dump zones differing in degrees of moisture (three plots in both S1 and S2) and in the control (in total, seven plots). Microarthropod communities included mites (Mesostigmata, Oribatida, and Prostigmata) and springtails (Collembola). The microarthropod abundance was significantly lower at both sections of the ash dump than in the control, while no significant differences were found between the ash-dump sections. The effect of reclamation was revealed only for mites. Among them, representatives of Oribatida proved to be most sensitive. There were no significant differences in the proportion of different groups of the community at S1. In turn, Oribatida were dominant at S2 and in the control. Based on the example of Oribatida and Mesostigmata model groups, it is shown that mite communities formed at the ash dump were species-poor and consisted of widespread species with a high degree of dominance of some of them. Oribatida can serve as a good bioindicator for assessing the soil state during restoration successions at ash dumps of CHP plants.

长期施加N、P肥对高寒草甸小型土壤节肢动物群落的影响

为查明长期施肥对高寒草甸小型土壤节肢动物群落影响，2012年5月下旬在西南民族大学青藏高原畜牧业高科技研究基地内用随机区组方式设置施N、P和NP混施三种处理实验样地，每种施肥处理分别设置10 g/m²、20 g/m²和30 g/m²三个施肥梯度，以不施肥的高寒草甸为对照样地。2017年8月对各样地内的小型土壤节肢动物、植物群落和土壤理化性质进行调查。结果表明：（1）施肥可以明显改变高寒草甸小型土壤节肢动物的群落组成结构，其中NP混施比单施N、P肥更能有效增加螨类和昆虫的类群数；（2）N、P、NP三种施肥种类的小型土壤节肢动物群落个体密度、类群数和Shannon多样性指数均显著增加（P<0.05），且当施肥量为20 g/m²时，小型土壤节肢动物群落的个体密度、类群数和Shannon多样性指数均达到最大；（3）小型土壤节肢动物群落的个体密度、类群数和Shannon多样性指数均与全磷含量呈显著正相关（P<0.05）。研究表明，在高寒草甸长期施加氮、磷肥，尤其是氮磷混施，不仅能够明显改变小型土壤节肢动物群落组成结构，还能显著提高群落密度和多样性，建议按照20 g/m²的总量对高寒草甸进行氮磷等量混施，以提高小型土壤节肢动物群落多样性及其生态功能。;The objective of this study was to examine the effects of long-term N and P addition on soil microarthropod communities in alpine meadows. Three addition treatments of N fertilizer (N), P fertilizer (P) and a NP mixed fertilizer (NP) were set up in Hongyuan County, northwest Sichuan, in late May 2012. Each treatment included three fertilization gradients of 10 g/m² (N₁₀, P₁₀ and NP₁₀), 20 g/m² (N₂₀, P₂₀ and NP₂₀), and 30 g/m²(N₃₀, P₃₀ and NP₃₀) with six replication plots in size of 3 m×3 m. Another six plots of alpine meadow without N and P addition were used as control treatments (CK). Investigations were conducted on the soil microarthropods and environmental factors in each plot in August 2017. Soil microarthropods were extracted from the soil samples for 48 h at 38℃ using the Tullgren method in the laboratory. The results showed that (1) the taxonomic composition structure of soil microarthropod communities was markedly influenced by N, P and NP additions, and the taxonomic richness of mites and insects were increased more significantly by NP mixed additions than N or P addition. (2) The individual density, taxonomic richness and Shannon diversity index of soil microarthropod communities increased significantly in the treatments of N, P and NP additions (P<0.05), and reached to maximum values at the fertilization gradient of 20 g/m². (3) The individual density, taxonomic richness and Shannon diversity index significantly and positively correlated with soil total P (P<0.05). The results demonstrated that additions of N, P, especially NP, changed the taxonomic composition structure, and increased the individual density and diversity of soil microarthropod communities in alpine meadows on Qinghai-Tibet Plateau. We recommended to add the N and P equal mixed fertilizer to alpine meadows at total amount of 20 g/m², to promote the soil microarthropod diversity and ecological functions.

Microarthropod abundance and community structure along a chronosequence within the Tanana River floodplain, Alaska

ABSTRACT We investigated abundance and community structure of soil microarthropods in three stages of a primary successional chronosequence along the Tanana River in interior Alaska: early-successional alder stands, mid-successional balsam poplar stands and late successional white spruce stands. Microarthropod abundances in alder stands were uniformly low and tended to increase in balsam popular stands where abundances were highly variable among sites. White spruce stands had the highest abundances, almost 8 times those of alder sites. Arthropod taxon and Oribatida family richness also increased (alder: 29 taxa, 6 families; balsam poplar: 34 taxa, 10 families; white spruce: 40 taxa, 14 families). Non-metric multidimensional ordination of arthropod taxa indicated microarthropod communities became more similar within stand types later in succession and environmental fit of the site characteristics found organic matter thickness, soil degree days, organic layer phosphorus (P), mineral layer concentrations of carbon (C), nitrogen (N), and manganese (Mn), and white spruce basal area were significant (p < 0.05). Regression analysis indicated prey abundance and predator abundance were positively correlated (R2 = 0.43; p< 0.001). Our findings point to the importance of vegetation, soil development and temperature, site stability, microarthropod colonization time, and possibly predator abundance in shaping these microarthropod communities.

Effects of Livestock Pressure and Vegetation Cover on the Spatial and Temporal Structure of Soil Microarthropod Communities in Iberian Rangelands

Forests, including their soils, play an important role since they represent a large reservoir of biodiversity. Current studies show that the diversity of soil fauna provides multiple ecosystem functions and services across biomes. However, anthropogenic practices often pose a threat to soil fauna because of changes in land use and soil mismanagement. In these terms, rangelands in the southwest of Spain present several problems of soil degradation related to livestock activity and soil erosion, the intensity of which compromises the soil fauna’s functions in the ecosystem. Therefore, the aim of this study is to evaluate the response of community metrics and the spatial distribution of soil microarthropods to livestock activity and vegetation in such ecosystems. A photo interpretation analysis of an experimental catchment used as a study area was developed to identify and classify the intensity of livestock pressure. A total of 150 soil samples were collected throughout 2018. Soil biological (CO2 efflux) and physical-chemical parameters (pH, bulk density, organic matter, and water contents), and such meteorological variables as precipitation, temperature, and evapotranspiration were considered as variables affecting the composition of microarthropod communities in terms of taxa diversity, abundances, and their adaptation to soil environment (evaluated by QBS-ar index). Results showed higher abundance of microarthropods and higher adaptation to soil environment outside the influence of trees rather than beneath tree canopies. Moreover, the classification of livestock pressure revealed by the photo interpretation analysis showed low correlations with community structure, as well as with the occurrence of well-adapted microarthropod groups that were found less frequently in areas with evidence of intense livestock activity. Furthermore, abundances and adaptations followed different spatial patterns. Due to future climate changes and increasing anthropogenic pressure, it is necessary to continue the study of soil fauna communities to determine their degree of sensitivity to such changes.

Pengaruh Perbedaan Aplikasi Pestisida pada Struktur Komunitas Mikroarthropoda Tanah dalam Skala Lapangan dan Laboratorium

The choice of using pesticides with natural ingredients or synthetic chemicals is a differentiator between organic farming systems and inorganic farming systems. Pesticides are additives in agriculture to control pests or weeds. Abamectin is one of the active ingredients that can be found in pesticides. Ground microarthropods are members of the soil mesofauna, which are soil animals that have a body size ranging from 0.2-2 mm. The purpose of this study was to determine the effect of differences in the application of pesticides on a field or laboratory scale on the structure of soil microarthropod communities. Soil samples were taken from three agricultural lands, namely Bandungan inorganic agricultural land, Kopeng inorganic agricultural land and Kopeng organic agricultural land. The study was conducted in August to December 2018 in the Ecology and Biosystematic Laboratory of the Department of Biology, FSM Undip. Found a total of 60 species species richness originating from 13 orders. The application of pesticides which include the concentration and frequency of pesticide spraying has a negative influence on the structure of soil microarthopod communities. Application of abamectin pesticides on a laboratory scale proves that the administration of abamectin pesticides that exceeds the recommended concentration will adversely affect the structure of the soil microathropod community. Based on statistical tests of soil microarthropod species diversity from the results of the application of pesticides on a field and laboratory scale is significantly different.

Roots, mycorrhizal fungi and altitude as determinants of litter decomposition and soil animal communities in tropical montane rainforests

This study assesses the importance of root- and mycorrhiza-derived resources for decomposition processes and as food resources for microarthropod communities along an altitudinal gradient of tropical montane rainforests in southern Ecuador. At 1000, 2000 and 3000 m microcosms with openings of different mesh sizes (4 mm, 45 μm) or closed were exposed in the field, manipulating accessibility by roots and mycorrhizal fungi. The microcosms contained undisturbed soil with a mixture of leaf litter from three abundant plant species from the site at which the microcosms were exposed. After 12 months water content, microbial biomass, remaining litter mass, C-to-N ratio and the soil microarthropod community structure were analysed. Water content and C-to-N ratio were lower and microbial biomass was highest at the lowest altitude, while litter decomposition and microarthropod abundance were at a maximum at the intermediate altitude. Exclusion of roots and mycorrhizal fungi did not affect litter decomposition, but decreased the abundance and diversity of Oribatida, while the abundance of Collembola increased in closed microcosms. The effect of root and mycorrhizal exclusion on all investigated parameters did not differ between the three altitudes. The results indicate that in nutrient limited tropical montane rainforests mycorrhizal fungi suppress the activity of other microorganisms, potentially competing for litter-derived resources, at each of the investigated altitudes. Collembola benefitted from this reduced competition while Oribatida strongly depended on root-derived resources.

Altitude and decomposition stage rather than litter origin structure soil microarthropod communities in tropical montane rainforests

Microarthropods impact organic matter turnover and nutrient cycling via processing of organic matter entering the soil as litter and root exudates. Variations in the structure of soil microarthropod communities are due to both biotic and abiotic factors such as local climatic conditions and litter quality. However, in particular in tropical ecosystems the relative importance of these factors for structuring soil microarthropod communities are little understood. We investigated variations in the structure of soil microarthropod communities in leaf and root litter from three altitudes exposed in three tropical montane rainforests at different altitude in southern Ecuador for three years. Leaf litter from three abundant tree species and roots of different diameter were collected from three sites at different altitude (ca. 1000, 2000, 3000 m). Litter and roots were placed in litterbags at the three altitudes, and after 6, 12, 24 and 36 months soil microarthropods in the litterbags were analysed. Density of Acari and Collembola, and diversity of Oribatida decreased with increasing altitude and varied with the degree the litter was decomposed rather than with litter origin and therefore quality of the litter material. Densities fluctuated during litter decomposition generally being lowest after 24 months but higher after 36 months. Species composition of Oribatida varied strongly with altitude; only few species overlapped between altitudes. The percentage of parthenogenetic Oribatida species decreased with increasing altitude. The results suggest that the origin and therefore quality of litter material is of little importance as driving factor for the composition of microarthropod communities of tropical montane rainforests. Factors changing between rainforest sites at different altitude, as well as decomposition stage of litter and associated changes in the microbial community are much more important.

Struktur Komunitas Mikroartropoda Tanah di Lahan Pertanian Organik dan Anorganik di Desa Batur Kecamatan Getasan Salatiga

Soil microarthropods is a arthropods that have an important role in decomposing organic materials and soil nutrients. On the farmland there is organic materials content and soil nutrients that abundants enough, because the addition of manure as a source of energy in the ground. The research was conducted in August-October 2015 took place in the field of organic and inorganic farmland in the Batur Village, Getasan Sub-district, Salatiga. This study aimed to examine the soil microarthropods community structure in organic and inorganic farmland as well as the effect of chemical and physical environmental factors to community structure of soil microarthropods. The study was conducted with samples of soil sampling method (PCT) and extracted using Barlese Funnel Extractor. Statistically show that diversity of soil microarthropods between organic and inorganic farmland are not significantly different. There is found 28 taxa of soil microarthropods in organic farmland and 23 taxa in inorganic. The highest total individual density of the taxa are exist in the organic farmland (2260 individual/ m²). The highest abundance of soil microarthropods taxa in inorganic farmland are Carabidae (26,55%) dan Prostigmata (13,27%), while in inorganic farmland are Carabidae (17,24%) dan larva Coleoptera (13,79%). The evenness of soil microarthropods taxa in organic farmland are much low compared with inorganicfarmland, because there is a dominant taxa (Carabidae). There is an influence relation between the chemical and physical environmental factors including water content, porosity, nutrient, and organic materials with community structure of soil microarthropods. Key words:Community structure, Soil microarthropods, Organic and inorganic farmland

Struktur Komunitas Mikroartropoda Tanah di Lahan Pertanian Organik dan Anorganik di Desa Batur Kecamatan Getasan Salatiga

Soil microarthropods is a arthropods that have an important role in decomposing organic materials and soil nutrients. On the farmland there is organic materials content and soil nutrients that abundants enough, because the addition of manure as a source of energy in the ground. The research was conducted in August-October 2015 took place in the field of organic and inorganic farmland in the Batur Village, Getasan Sub-district, Salatiga. This study aimed to examine the soil microarthropods community structure in organic and inorganic farmland as well as the effect of chemical and physical environmental factors to community structure of soil microarthropods. The study was conducted with samples of soil sampling method (PCT) and extracted using Barlese Funnel Extractor. Statistically show that diversity of soil microarthropods between organic and inorganic farmland are not significantly different. There is found 28 taxa of soil microarthropods in organic farmland and 23 taxa in inorganic. The highest total individual density of the taxa are exist in the organic farmland (2260 individual/ m²). The highest abundance of soil microarthropods taxa in inorganic farmland are Carabidae (26,55%) dan Prostigmata (13,27%), while in inorganic farmland are Carabidae (17,24%) dan larva Coleoptera (13,79%). The evenness of soil microarthropods taxa in organic farmland are much low compared with inorganicfarmland, because there is a dominant taxa (Carabidae). There is an influence relation between the chemical and physical environmental factors including water content, porosity, nutrient, and organic materials with community structure of soil microarthropods. Key words:Community structure, Soil microarthropods, Organic and inorganic farmland

Effects of Cushion Plants on High-Altitude Soil Microarthropod Communities: Cushions Increase Abundance and Diversity of Mites (Acari), but not Springtails (Collembola)

ABSTRACTCushion plants in alpine ecosystems act as nurse species, which modify and alleviate environmental conditions and positively influence the diversity and abundance of other organisms. Soil fauna in alpine environments should benefit from nurse plant facilitation, but this has not been investigated. We compared diversity, abundance, and community structure of soil microarthropods (Collembola, Oribatida, Mesostigmata, Prostigmata, Endeostigmata, and Astigmata) under cushion plants and in adjacent open microsites in high altitude patterned ground landscapes in New Zealand. We investigated how cushion plants influence environmental factors, and how environmental factors and species traits contribute to microarthropod community structure. The results show that cushion plants are a key in maintaining the biodiversity of soil microarthropods in the high alpine. Cushion plants maintain higher moisture and organic matter content in the soil, provide productive and structurally complex habitat, and mitigate disturbance. Abundance and species richness of Oribatida, Mesostigmata, and Prostigmata were higher under cushion plants. In contrast, abundance of Collembola was higher in open microsites, while their species richness similar in and out of cushions. Oribatida assemblages were dominated by small asexual species, indicating a disturbed environment. Oribatida community structure was significantly related to the microhabitat in two out of three mountain ranges. Collembola assemblages were similar in and out of cushions. Higher soil moisture and organic matter content under cushion plants were significant in explaining patterns in microarthropod assemblages, although high percentage of variability was not explained by environmental variables. There was no effect of cushions on soil temperatures. Species identity of the cushion plant did not influence abundance, species richness, or community assemblages of mites and springtails; however, some species were associated with either Dracophyllum or Raoulia cushions.

Relative importance of local- and large-scale drivers of alpine soil microarthropod communities.

Nitrogen (N) deposition and climate are acknowledged drivers of change in biodiversity and ecosystem function at large scales. However, at a local scale, their impact on functions and community structure of organisms is filtered by drivers like habitat quality and food quality/availability. This study assesses the relative impact of large-scale factors, N deposition and climate (rainfall and temperature), versus local-scale factors of habitat quality and food quality/availability on soil fauna communities at 15 alpine moss-sedge heaths along an N deposition gradient in the UK. Habitat quality and food quality/availability were the primary drivers of microarthropod communities. No direct impacts of N deposition on the microarthropod community were observed, but induced changes in habitat quality (decline in moss cover and depth) and food quality (decreased vegetation C:N) associated with increased N deposition strongly suggest an indirect impact of N. Habitat quality and climate explained variation in the composition of the Oribatida, Mesostigmata, and Collembola communities, while only habitat quality significantly impacted the Prostigmata. Food quality and prey availability were important in explaining the composition of the oribatid and mesostigmatid mite communities, respectively. This study shows that, in alpine habitats, soil microarthropod community structure responds most strongly to local-scale variation in habitat quality and food availability rather than large-scale variation in climate and pollution. However, given the strong links between N deposition and the key habitat quality parameters, we conclude that N deposition indirectly drives changes in the soil microarthropod community, suggesting a mechanism by which large-scale drivers indirectly impacts these functionally important groups.

Struktur Komunitas Mikroartropoda Tanah di Lahan Penambangan Galian C Rowosari, Kecamatan Tembalang, Semarang

Rowosari miningsite isthe ‘C’ type of excavation area in Semarang. Mining activities may affect environmental disturbance, including on soil fauna. This research aims to determine the community structure of soil microarthropods in Rowosari mining area. The research was conducted in August-September 2015. Soil samples were taken on diagonal plot of 5x5 m2 with a five-point sampling on two stations, namely Post Mining Area (PoMA) and Pre Mining Area (PeMA). The analysis used in the research are relative abundance index, Shannon-Weiner diversity index, evenness index, and Sorensen similarity index. The results shows that there are 360-660 individuals/m2 from 10 ordo and 24 taxa found in Rowosari Excavation Site. The highest relative abundance index is Carabidae (22,22) in PoMA station and Prostigmata (21,21) in PeMA station. The diversity both station belongs to medium category (2,43-2,45). The highest evenness index is 0,95. The similarity taxa of soil microarthropods in two stations are categorized as medium. Community structure of soil microathropods in Post Mining Area and Pre Mining Areawere no significant differences. Keywords: Community structure, Soil microarthropods, Miningexcavation C.

Year-round behaviour of soil microarthropod communities under plant protection product application

The use of plant protection products (PPPs) in agro-environments can lead to undesired exposure of non-target organisms in non-target compartments. A year-round field survey was conducted in a vineyard in Northern Italy, for monitoring the changes in the structure of soil microarthropod communities under the application of PPPs, focusing on springtails and mites, both inside and 4 and 10 m outside the vineyard. Exposure to PPPs was estimated as time-weighted average soil concentrations. The fluctuations in the abundances of the different organisms after the application of PPPs, especially insecticides, were recorded. A recovery in abundances was observed at the end of the productive season outside the field and at the beginning of the next spring within the vineyard. Using multivariate statistical tools, the behaviour of each taxon in relation to the stressors was assessed. Some organisms were affected by the stressors, while others were favoured because of low vulnerability to PPPs and the indirect effect of the absence of other taxa. The principal response curves (PRC) method was the most sensitive tool for assessing PPP effects on soil arthropod communities. Strong differences were evident in the structure of the communities inside and outside the vineyard, with the communities sampled 4 and 10 m outside the vineyard being fairly similar, the latter considered as control. The role of physical stressors on community composition is recognised. However, chemical stressors, and in particular PPP exposure seemed to have larger effects on structural and functional characteristics of soil arthropod communities than physical stressors.

Climate change effects on soil microarthropod abundance and community structure

Long-term ecosystem responses to climate change strongly depend on how the soil subsystem and its inhabitants respond to these perturbations. Using open-top chambers, we studied the response of soil microarthropods to single and combined effects of ambient and elevated atmospheric [CO2], ambient and elevated temperatures and changes in precipitation in constructed old-fields in Tennessee, USA. Microarthropods were assessed five years after treatments were initiated and samples were collected in both November and June. Across treatments, mites and collembola were the most dominant microarthropod groups collected.We did not detect any treatment effects on microarthropod abundance. In November, but not in June, microarthropod richness, however, was affected by the climate change treatments. In November, total microarthropod richness was lower in dry than in wet treatments, and in ambient temperature treatments, richness was higher under elevated [CO2] than under ambient [CO2]. Differential responses of individual taxa to the climate change treatments resulted in shifts in community composition. In general, the precipitation and warming treatments explained most of the variation in community composition. Across treatments, we found that collembola abundance and richness were positively related to soil moisture content, and that negative relationships between collembola abundance and richness and soil temperature could be explained by temperature-related shifts in soil moisture content.Our data demonstrate how simultaneously acting climate change factors can affect the structure of soil microarthropod communities in old-field ecosystems. Overall, changes in soil moisture content, either as direct effect of changes in precipitation or as indirect effect of warming or elevated [CO2], had a larger impact on microarthropod communities than did the direct effects of the warming and elevated [CO2] treatments. Moisture-induced shifts in soil microarthropod abundance and community composition may have important impacts on ecosystem functions, such as decomposition, under future climatic change.

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.

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%.

Soil microarthropod community structure and litter decomposition dynamics: A study of tropical and temperate sites

The influence of climate, substrate quality and microarthropods on decomposition was studied by comparing the mass loss of litter at three forested sites: two tropical and one temperate. At each site, litterbags containing a dominant local litter were placed in the field in replicated plots. Half the bags were treated with naphthalene to reduce microarthropod abundance. The pattern of mass loss was markedly seasonal at the temperate site. The amount of mass remaining after 250 days was strongly related to the initial %N of the three litter types ( r 2=0.997). The faunated litterbags lost more mass at all sites and for all litters studied than the litterbags with reduced microarthropod populations. The effect was minimal at the temperate site where the fauna tended to increase the decomposition rate only towards the end of the year. In contrast, the effect of the fauna at the tropical sites was marked within months of the start of the experiment. Species richness of microarthropods in samples of 300 cm 2 of leaf litter was similar at the three sites. However, diversity (measured using Fisher's α index) was greatest at the tropical sites.