Management intensity affects traits of soil microarthropod community in montane spruce forest

This study examined the influence of forest management intensity (3 unmanaged, 3 mild managed, 5 intensively managed stands) on soil microarthropods in montane spruce forest. We particularly focused on Oribatida and Collembola which play important roles in organic matter decomposition and nutrient cycling. Our results showed a significant shift from fungivory and carnivory to detritivory in the Oribatida community accompanying management intensification. Similarly, parthenogenetic oribatid mite species contributed more to the community in intensively managed forests and the presence of Collembola species with developed furca increased with management intensification. Although there was no remarkable influence of management intensity on total densities or diversity indices, important and significant shifts in species composition and functional groups showed that soil functions and processes were affected by forest management. Trait assessment indicates a shift in roles Oribatida play in decomposition; fragmentation and comminuting of undecomposed litter seems to gain importance in the intensively managed forest, whereas fungivorous species affect primary decomposers through feeding on fungi in the unmanaged forest.     

Diversity of soil mites (Acari: Oribatida,Mesostigmata) along a gradient of land use types in New York

This study explored the relationship between landscape-level factors (land use type) and the diversity of soil mites (Acari: Oribatida, Mesostigmata) at a within-site scale, using diversity measures including point diversity (local species diversity within a single sampling point), patterns of species turnover among the sampling points, and alpha diversity (total species richness in a habitat). The land use types included corn fields, intensive short-rotation forestry plantations, two types of abandoned agricultural fields, and hardwood forests.Land use type was identified as a significant factor influencing both small-scale (within individual soil cores) and site-scale diversity of Oribatida, which increased in the order “corn → willow → abandoned fields → forests”. There was no statistical relationship between land use type and abundance or diversity of Mesostigmata.Using a bootstrapping method to generate “random” communities, we found that all land use types had significantly more diverse patterns of species abundance than was expected by chance. On the other hand, the patterns of presence/absence of species were less diverse than expected by chance. Local site factors were significant in driving the patterns of diversity of soil mites at the site scale; land use type was less important. The overall structure of Oribatida and Mesostigmata assemblages was significantly related to land use type. We conclude that soil communities respond to land management on both local scales and habitat-wide scales.     

Top-down control of soil microarthropods - Evidence from a laboratory experiment

Predator-prey interactions are of eminent importance as structuring forces for animal communities. The present study investigates if and how strongly the density of soil microarthropods is controlled by top-down forces, i.e. predation by mesostigmate mites (Mesostigmata, Acari). We set up a laboratory experiment running for ten weeks with undisturbed soil cores taken from the field using two densities of predatory mesostigmate mites: (1) ambient density (control) and (2) increased density (addition of seven Pergamasus septentrionalis and eight Lysigamasus sp. individuals). Increased predator density resulted in a decrease in the density of Oribatida, Collembola and Protura whereas the density of other taxa including Astigmata, Prostigmata and Uropodina was not significantly affected. Additionally, the species number of Oribatida was also not significantly affected. Taxa of Oribatida and Collembola were differently affected by increased predator density. Among Collembola, densities of Poduridae and Sminthuridae were reduced, whereas Entomobryidae were not affected. Among Oribatida, densities of Oppiidae and Suctobelbidae were reduced whereas Desmonomata, Poronota and Tectocepheus were not affected. Grouping of Oribatida into different size classes and into classes differing in sclerotization suggests that smaller mites (200-300 μm) and mites with less sclerotization were more heavily affected than larger mites and mites with strong sclerotization. The results indicate that predatory mesostigmate mites have the potential to control the density of certain taxa of soil microarthropods. In particular, small and little sclerotized prey is susceptible to predator control indicating that predator defense is an important component of the life history tactics of soil microarthropods, especially of Oribatida.     

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.     

Soil springtails (Hexapoda: Collembola), symphylans and pauropods (Arthropoda: Myriapoda) under different management systems in agroecosystems of the subhumid Pampa (Argentina)

The Pampa region is the most important agricultural area in Argentina. Although intensive agricultural activity is leading to important levels of soil degradation, studies on the impact on soil fauna are scarce. Despite the environmental importance of collembolans, symphylans and pauropods in soil, information on the influence of land management on their population densities is poor, particularly in Neotropical agroecosystems. The aim of this study was to investigate the effects of different management systems on the density of collembolans, symphylans and pauropods. Population abundance of these arthropods was examined in a natural site and a cattle raising, a mixed and an agricultural management system on a Typic Hapludoll soil in La Colacha, Córdoba, Argentina. All the sites studied had the same land use history until approximately 50 years before sampling and have the same soil type. Total abundance of the studied groups varied in the different management systems. Our results suggest that conventional agricultural management tends to reduce the density of collembolans and pauropods. Our data do not support our hypothesis that the cattle raising management system constitutes an intermediate situation between the natural site and the high-input management systems. We conclude that the reduction of collembolan and pauropod densities in high-input management systems is largely explained by the mechanical and chemical perturbations produced by conventional agricultural management practices and by particular abiotic soil conditions present in the intensively managed sites that are unfavourable for these organisms. Surprisingly, symphylans were more abundant in the mixed management site. The implications of our findings on soil ecosystem functioning are discussed.     

Effects of habitat age and plant species on predatory mites (Acari, Mesostigmata) in grassy arable fallows in Eastern Austria

Density, diversity and assemblage structure of Mesostigmata (cohorts Gamasina and Uropodina) were investigated in nine grassy arable fallows according to a factorial design with age class (2-3, 6-8, 12-15 years) and plant species (legume: Medicago sativa, herb: Taraxacum officinale, grass: Bromus sterilis) as factors. The response of Mesostigmata to habitat age and plant species was explored because this group belongs to the dominant acarine predators playing a crucial role in soil food webs and being important as biological control agents. To our knowledge, this combination of factors has never been studied before for Mesostigmata. A further rarely applied aspect of the present study is the micro-scale approach investigating the Mesostigmata assemblage of the soil associated with single plants. Four plots were randomly chosen at each fallow in May 2008. At each plot plant roots and the adjacent soil of five randomly selected plant individuals per plant species were dug out with steel cylinders for heat extraction of soil fauna and measurement of environmental parameters. In total, 83 mite taxa were identified, with 50 taxa being new to Austria. GLM analysis revealed a significant effect of plant species on mite density, with significantly more mites in B.?sterilis than in T.?officinale samples, and M.?sativa samples being intermediate. This was in contrast to the assumption that the mite density is highest in M. sativa samples due to the propagation of plant quality effects to higher trophic levels. These results were probably caused by a higher amount of fine roots in grass samples leading to high densities of Collembola, which are preferred prey of predatory mites. Mite density did not significantly differ between the three age classes. A canonical analysis of principal coordinates (CAP) showed that the mite assemblage exhibited a weak yet significant separation between plant species, and a highly significant separation between age classes. Accordingly, different mite assemblages were found for the three age classes, while only few mite species were clearly associated with a single plant species. Finally, canonical correspondence analysis (CCA) revealed that the mite assemblage was best explained by soil organic carbon, total density of Collembola and water content.     

Vertical distribution of soil mites (Acari) in conventional and no-tillage agricultural systems

Summary Soil mite abundance was measured at four depths (0–5, 6.5–11.5, 13–18, and 19.5–24.5 cm) in agricultural plots under no-tillage or conventional tillage in Clarke County, Georgia, USA. The vertical distribution of mites was not significantly different between the two tillage systems: Most mites were found in the top 0–5 cm zone. This was the zone where greater moisture content occurred, and (in other studies) was the zone of maximum root biomass and microbial activity. Among mite suborders, only the Prostigmata were found in any abundance below 5 cm. Mite populations declined dramatically on occasions when the soil moisture exceeded field capacity, but did not appear to migrate vertically.Dedicated to the late Prof. Dr. W. Kühnelt     

Assessing the relationship between patch type and soil mites: A molecular approach

An urgent need exists for indicators of soil health and patch functionality in extensive rangelands that can be measured efficiently and at low cost. Soil mites are candidate indicators, but their identification and handling is so specialised and time-consuming that their inclusion in routine monitoring is unlikely. The aim of this study was to measure the relationship between patch type and mite assemblages using a conventional approach. An additional aim was to determine if a molecular approach traditionally used for soil microbes could be adapted for soil mites to overcome some of the bottlenecks associated with soil fauna diversity assessment. Soil mite species abundance and diversity were measured using conventional ecological methods in soil from patches with perennial grass and litter cover (PGL), and compared to soil from bare patches with annual grasses and/or litter cover (BAL). Soil mite assemblages were also assessed using a molecular method called terminal-restriction fragment length polymorphism (T-RFLP) analysis. The conventional data showed a relationship between patch type and mite assemblage. The Prostigmata and Oribatida were well represented in the PGL sites, particularly the Aphelacaridae (Oribatida). For T-RFLP analysis, the mite community was represented by a series of DNA fragment lengths that reflected mite sequence diversity. The T-RFLP data showed a distinct difference in the mite assemblage between the patch types. Where possible, T-RFLP peaks were matched to mite families using a reference 18S rDNA database, and the Aphelacaridae prevalent in the conventional samples at PGL sites were identified, as were prostigmatids and oribatids. We identified limits to the T-RFLP approach and this included an inability to distinguish some species whose DNA sequences were similar. Despite these limitations, the data still showed a clear difference between sites, and the molecular taxonomic inferences also compared well with the conventional ecological data. The results from this study indicated that the T-RFLP approach was effective in measuring mite assemblages in this system. The power of this technique lies in the fact that species diversity and abundance data can be obtained quickly because of the time taken to process hundreds of samples, from soil DNA extraction to data output on the gene analyser, can be as little as 4 days.     

Use of geochemical fingerprints to trace sediment sources in an agricultural catchment of Argentina

Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. Specific land uses and management practices, such as intensive grazing and crop cultivation, are considered to be significantly driving and accelerating these processes. This research focuses on the identification of suitable soil tracers from hot spots of land degradation and sediment fate in an agricultural catchment of central Argentina with erodible loess soils. Using Energy Dispersive X-Ray Fluorescence (EDXRF), elemental concentrations were determined and later used as soil tracers for geochemical characterization. The best set of tracers were identified using two artificial mixtures composed of known proportions of soil sources collected from different lands having contrasting soil uses. Barium, calcium, iron, phosphorus, and titanium were identified for obtaining the best suitable reconstruction of source proportions in the laboratory-prepared artificial mixtures. Then, these elements, as well as the total organic carbon, were applied for pinpointing critical hot spots of erosion within the studied catchment. Feedlots were identified to be the main source of sediments, river banks and dirt roads together are the second most important source. This investigation provides key information for optimizing soil conservation strategies and selecting land management practices and land uses which do not generate great contribution of sediment, preventing pollution of the waterways of the region.     

Temperature tolerance in soil microarthropods: Simulation of forest-fire heating in the laboratory

Forest fires markedly reduce the abundance of surface-dwelling soil animals; animal densities also decline in soil layers underlying the char layer. The aim of the present study was to determine lethal temperatures for different species within the more abundant microarthropod groups in boreal forests, namely Collembola, Protura, Mesostigmata and Oribatida. In the laboratory, forest soil humus containing naturally occurring microarthropods was heated in plastic bags to avoid desiccation. Each sample was heated to one of 11 different temperatures between 20 and 60 °C for 1, 4, or 12 h. At the 1-h exposure, 36 °C was the highest temperature tolerated before significant decreases in numbers were detected. The corresponding temperatures after 4- and 12-h exposures were 34 °C for Oribatida and 30–32 °C for Collembola, Protura and Mesostigmata, respectively. Individual species responded differently, and the most heat-tolerant species within Oribatida was Tectocepheus velatus (40 °C at 4-h exposure) while Friesea mirabilis and Mesaphorura sp. (36 °C at 4-h exposure) were the most tolerant within Collembola. During a forest fire, temperatures higher than those tolerated by the investigated groups and species may well be reached.     

梵净山常绿落叶阔叶混交林土壤螨类群落结构研究

为了查明梵净山沿海拔梯度常绿落叶阔叶混交林土壤螨类群落特征及海拔差异,2015年6月对梵净山常绿落叶阔叶混交林带土壤螨类进行调查,获土壤螨类2 100只,隶属4亚目55科101属。采用属数和个体数量,群落多样性、优势度、均匀度、甲螨群落MGP和捕食性螨类MI等指数对螨类群落结构的分析显示,Vilhenabates和Setoxylobates是该林带的主要类群,螨类分布呈现明显的表聚性。随海拔上升,螨类类群数和个体数量基本呈减少的趋势。土壤螨类群落优势度表现为1 300 m1 900 m1 500 m1 700 m,多样性和均匀性指数表现为1 700 m1 900 m1 500 m1 300 m,方差分析表明海拔差异对螨类优势度具有显著影响,对多样性和均匀性影响很小。甲螨群落结构以O型为主;中气门螨类群落以K-选择类群为主。     

Development of key soil health indicators for the Australian banana industry

To improve the sustainability and environmental accountability of the banana industry there is a need to develop a set of soil health indicators that integrate physical, chemical and biological soil properties. These indicators would allow banana growers, extension and research workers to improve soil health management practices. To determine changes in soil properties due to the cultivation of bananas, a paired site survey was conducted comparing soil properties under conventional banana systems to less intensively managed vegetation systems, such as pastures and forest. Measurements were made on physical, chemical and biological soil properties at seven locations in tropical and sub-tropical banana producing areas. Soil nematode community composition was used as a bioindicator of the biological properties of the soil. Soils under conventional banana production tended to have a greater soil bulk density, with less soil organic carbon (C) (both total C and labile C), greater exchangeable cations, higher extractable P, greater numbers of plant-parasitic nematodes and less nematode diversity, relative to less intensively managed plant systems. The organic banana production systems at two locations had greater labile C, relative to conventional banana systems, but there was no significant change in nematode community composition. There were significant interactions between physical, chemical and nematode community measurements in the soil, particularly with soil C measurements, confirming the need for a holistic set of indicators to aid soil management. There was no single indicator of soil health for the Australian banana industry, but a set of soil health indicators, which would allow the measurement of soil improvements should include: bulk density, soil C, pH, EC, total N, extractable P, ECEC and soil nematode community structure.     

Assessment of fungal communities in soil and tomato roots subjected to diverse land and crop management systems

Effects of diverse agricultural land management practices on soil and on root colonizing fungal communities were determined through a PCR-based molecular method and a culture-dependent method, respectively, in a field location with uniform soil type. Initiated in July 2000, the management systems were: conventional tomato production, frequent tillage (disk fallow), undisturbed weed fallow, bahiagrass pasture (Paspalum notatum var. notatum ‘Argentine’), and an organically managed system including cover crops and annual applications of poultry manure and urban plant debris. Culture-dependent colony counting was used to identify and enumerate communities of root colonizing fungi and length heterogeneity polymerase chain reaction (LH-PCR) analysis of internal transcribed spacer-1 (ITS-1) profiles to characterize phylotypes in soil fungal communities. Three years after initiation of land management treatments and midway through tomato cultivation, both methods detected a high degree of similarity in fungal community composition between weed fallow and bahiagrass plots. Soil fungal communities in organically managed plots were similar to each other and distinct from communities in other land management systems while the composition of root colonizing fungal communities in organic plots was divergent. The results demonstrate that the soil fungal communities and root colonizing fungal communities were affected differently depending on land and crop management practices. Fusarium oxysporum was a dominant species in all soil and root colonizing fungal communities except those subjected to organic management practices.     

Discriminating the effects of agricultural land management practices on soil fungal communities

The structure of fungal communities was examined in soil subjected to 5 years of different agricultural land management and tomato production practices. Length heterogeneity polymerase chain reaction (LH-PCR) of fungal rDNA internal transcribed spacer-1 (ITS-1) regions was used to create genomic fingerprints of the soil fungal communities. Three years after initiation of land management practices, univariate analysis of genetic diversity failed to detect differences among soil fungal communities in plots managed organically, conventionally or maintained free of vegetation by continuous tillage (disk fallow). Genetic diversity was significantly higher in plots maintained as a perennial pasture grass (Paspalum notatum var Argentine bahiagrass) or as an undisturbed weed fallow. The composition of soil fungal communities within organic, pasture grass or disk fallow plots were separated into unique clusters by non-parametric multivariate analysis of their Bray-Curtis similarity matrices, computed from the relative abundance of ITS-1 amplicons, while the composition of communities within disk fallow and conventional plots could not be distinguished from each other. Diversity of soil fungal communities was significantly reduced following the cultivation of tomato in year four when compared to the diversity in plots where tomato was not cultivated. Divergence in the composition of soil fungal communities was observed following the cultivation of tomato under all land management regimes except organic, where communities continued to remained clustered based upon similarities among their ITS-1 amplicons. Divergence in the composition of fungal communities became more pronounced following two major hurricanes (Francis and Jeanne, September 2004) except for communities in the organic and pasture grass plots. Following the completion of a second tomato crop in year 5, genetic diversity and richness was similar under all land management regimes except the pasture grass, where it remained significantly higher. By contrast, following two consecutive years of tomato production, unique but mutually similar compositions of fungal communities were detected only in plots subjected to the organic land management regime. This was supported by observations that fungal communities were dominated by a 341 bp rDNA amplicon fragment in all land management regimes except the organic. Cloning and sequencing indicated that the 341 bp fragment generated by LH-PCR had a sequencing size of 343 bp, which was most closely related to Fusarium oxysporum. Thus, land management practices that disturb or disrupt soil fungal communities will significantly reduce their diversity. However, the composition of soil fungal communities is more strongly influenced by land management practices and communities within an organically management system were more resistant to anthropogenic and meteorological disturbances.     

Land‐Use Effects on Soil Nutrient Cycling and Microbial Community Dynamics in the Everglades Agricultural Area,Florida

Soil subsidence has become a critical problem since the onset of drainage of the organic soils in the Everglades Agricultural Area (EAA), which may impair current land uses in the future. The objectives of this study were to characterize soil microbial community‐level physiology profiles, extracellular enzymatic activities, microbial biomass, and nutrient pools for four land uses: sugarcane, turfgrass, pasture, and forest. Long‐term cultivation and management significantly altered the distribution and cycling of nutrients and microbial community composition and activity in the EAA, especially for sugarcane and turf fields. The least‐managed fields under pasture had the lowest microbial biomass and phosphorus (P) levels. Turf and forest had more microbial metabolic diversity than pasture or the most intensively managed sugarcane fields. Land‐use changes from sugarcane cropping to turf increased microbial activity and organic‐matter decomposition rates, indicating that changes from agricultural to urban land uses may further contribute to soil subsidence.     

不同栽培模式对中小型土壤动物多样性的影响

土壤动物是土壤中重要的生物群落,在分解凋落物、土壤有机质以及维护生态系统平衡等方面中扮演重要角色。为了研究不同栽培模式下中小型土壤动物多样性特征,探究有利于中小型土壤动物的种植方式,本文研究了有机与常规栽培、大棚与露天、茄果与叶菜等不同栽培模式对中小型土壤动物种群数量、组成和多样性等特征的影响。结果表明：1）利用Tullgren法在18个样地共获得中小型土壤动物3 869只,隶属于2门14目30科（亚目）。辐螨亚目、甲螨亚目以及等节跳科构成了研究区土壤动物的主要部分。2）露天条件下,有机栽培使5~10 cm和10~15 cm土层中小型土壤动物数量显著高于常规栽培;但大棚条件下,有机栽培使0~5 cm和5~10 cm土层中小型土壤动物数量显著低于常规栽培。3）有机栽培下,大棚内0~5 cm和10~15 cm土层中小型土壤动物数量显著低于露天,且棚内10~15 cm层中小型土壤动物丰富度显著高于常规栽培;而常规栽培下,大棚内5~10 cm土层中小型土壤动物数量著高于露天。无论有机和常规栽培,棚内0~5 cm层中小型土壤动物Shannon-Weiner多样性高于露天。4）有机栽培使叶菜作物10~15 cm土层中小型土壤动物数量显著低于常规栽培,且0~5 cm土层中小型土壤动物均匀度指数显著高于常规栽培;常规栽培使叶菜作物0~5 cm和5~10 cm土层中小型土壤动物数量显著高于茄果作物。因此,在设施条件下采用有机栽培和管理,且利用作物轮作可能更有利于土壤动物群落数量和多样性的增加。     

Acari (mite) assemblages under plantations of bluegum, Eucalyptus globulus, in southwestern Australia

Farm forestry, in particular the planting of exotic bluegums Eucalyptus globulus, is a strategy increasingly used in southwestern Australia to mitigate the damaging effects of land clearing and to improve agricultural productivity. At the same time, such agroforestry systems have the potential to at least partially impede the biodiversity decline associated with habitat destruction and agriculture. The soil/litter habitat, an important repository of biodiversity in terrestrial systems, is one of the habitats most affected by clearing and conventional agricultural practices. Within this habitat, free-living mites are one of the most diverse and abundant animal groups contributing significantly to key ecosystem functions. This study compares the soil and litter mite assemblages of 7-year-old E. globulus plantations with those of adjacent native forest and pasture sites. The assemblages associated with E. globulus were substantially more diverse than those of the pasture soils but well below that of the native forest. Particularly low densities of oribatid mites were observed in the plantation sites. We suggest that the young plantation age, the exotic nature of the plantation species, and the homogeneous, mono-specific litter all contributed to limit the potential for these plantations to enhance mite biodiversity.     

Effects of agricultural management on nematode–mite assemblages: Soil food web indices as predictors of mite community composition

Biological indicators based on abundances of soil organisms are powerful tools for inferring functional and diversity changes in soils affected by agricultural perturbations. Field plots, combining organic and conventional practices with no tillage, conservation tillage and standard tillage maintained different nematode assemblages and soil food webs. Soil food web indices based on nematode assemblages were reliable predictors of the trophic composition of functional characteristics of soil mite assemblages. Bacterial-feeding and predatory nematodes, together with predatory mites, were abundant in the organic-no till treatments and were associated with high values of the Enrichment and the Structure Index based on nematode assemblages. Conventional-Standard tillage treatments had high abundances of fungal- and plant-feeding nematodes and algivorous mites, associated with high values of the Basal and Channel Index. This study validates the hypothesis that nematode-based soil food web indices are useful indicators of other soil organisms such as mites, with similar functional roles and environmental sensitivities.     

Effect of seasonality and agricultural practices on occurrence of entomopathogenic nematodes and soil characteristics in La Rioja (Northern Spain)

The effects of seasonality and land management on entomopathogenic nematodes (EPNs) distribution and on soil characteristics were studied in natural areas and agricultural fields under organic and conventional management in La Rioja (Northern Spain). The population density of the native EPNs as well as air temperature, rainfall, soil fertility, soil moisture, and soil content of heavy metals were seasonally recorded over 2 consecutive years. The highest occurrence of EPNs was observed in autumn, followed by spring and summer. Agricultural management influenced the amount of soil organic matter, nutrients and heavy metals, as well as soil volumetric moisture and temperature, leading to statistical differences mainly between natural and agricultural sites, but also in some cases between different types of agricultural management. The usefulness of soil organic matter, C, N, P and K content, as well as the C/N, C/P and N/P ratios as indicators for differentiating conventional and organic crop management as well as the role of agricultural practices such as tillage and fertilizing is discussed.