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H Ferris - One of the best experts on this subject based on the ideXlab platform.
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Increases in Atmospheric [CO2] and the Soil Food Web
Managed Ecosystems and CO2, 2020Co-Authors: Donald A. Phillips, H Ferris, J. C. MooreAbstract:Organic inputs to Soil are comprised largely of plant debris and root exudation, which is responsible for rhizodeposition. Increases in organic matter inputs from plants growing under elevated [CO2] affect Soil microorganisms and a limited set of conclusions can be drawn. Bacterial and fungal communities in Soil ecosystems use such plant materials as resources to support multiple levels of tiny grazers and predators, which comprise Soil Food Webs. Ten years of elevated [CO2] at the ETH FACE site produced data on Soil protozoa and nematodes that are consistent with adjustments predicted for availability of Soil bacteria and fungi. Disparate changes in Soil microorganisms and complex adjustments in Food Web structure reported under higher [CO2] in a multitude of other experiments suggest that a better understanding of C resource availability is needed. Increases in living root mass under elevated [CO2] could affect Soil Food Webs through additional exudation, but limited information is available on changes in root exudation under such conditions. We summarize here a new, more complex, understanding of root exudation that includes mechanisms by which microorganisms, and possibly their predators within the Food Web, can actively enhance root exudation. Initial experiments indicate that higher [CO2] can increase root exudation of amino acids under axenic conditions by two separate mechanisms and these could result in more rhizodeposition. Little is known about how elevated [CO2] levels alter predation, another key connection between the Soil Food Web and the plant, but reductionist studies are beginning to support the concept that specific molecules affect predation and influence many organismic interactions in the root zone. Because the fossil record suggests Soil Food Webs were exposed to widely varied levels of [CO2] for long periods, a certain stability of these interactions should be expected as global atmospheric [CO2] increases.
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ecosystem services of the Soil Food Web after long term application of agricultural management practices
Soil Biology & Biochemistry, 2017Co-Authors: H Ferris, Xiaoke Zhang, Jeffrey P Mitchell, Wenju LiangAbstract:Abstract The structure of Soil nematode assemblages was assessed in field plots in the San Joaquin Valley of California which have 16-year management system histories. Attributes of the ecosystem functions of the assemblages were determined in laboratory studies. The four agricultural management systems were no tillage (minimum tillage) with cover crops in the intervals between economic crops, standard tillage with cover crops, minimum tillage without cover crops and standard tillage without cover crops. The economic crops were sorghum and garbanzo beans. A Soil column system was used in laboratory studies to evaluate the nitrogen mineralization ecosystem service associated with nematode assemblages in Soils from the four management systems compared to that in defaunated Soil. In an additional comparison, defaunated Soil was amended with mineral fertilizer solution for comparison with the mineralization service of the Soil fauna. Management systems using cover crops, which created a continuity of both photosynthetic production and roots in the Soil, strongly enhanced the nematode assemblages in the field Soil. Management systems with cover crops had greater total abundance, measured as numbers, biomass and metabolic footprints, of nematodes, and also of the functional guilds of nematodes considered important in Soil fertility and as prey for predators. Leachates from Soil columns with intact nematode assemblages had greater total mineral nitrogen and supported greater plant growth than those from defaunated columns. Soil carbon levels in field plots were strongly affected by the management systems. The biomass and diversity-weighted footprint of bacterivore and microbivore (bacterivores plus fungivores) nematodes, in turn, were correlated with levels of Soil carbon.
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abundance diversity and connectance of Soil Food Web channels along environmental gradients in an agricultural landscape
Soil Biology & Biochemistry, 2011Co-Authors: Sara Sanchezmoreno, H Ferris, Anna Youngmathews, Steven W Culman, Louise E JacksonAbstract:Abstract Soil Food Webs respond to anthropogenic and natural environmental variables and gradients. We studied abundance, connectance (a measure of the trophic interactions within each channel), and diversity in three different channels of the Soil Food Web, each comprised of a resource-consumer pair: the microbivore channel (microbes and their nematode grazers), the plant–herbivore channel (plants and plant-feeding nematodes), and the predator–prey channel (predatory nematodes and their nematode prey), and their associations with different gradients in a heterogeneous agricultural landscape that consisted of intensive row crop agriculture and grazed non-irrigated grasslands in central California. Samples were taken at three positions in relation to water channels: water’s edge, bench above waterway, and the adjacent arable or grazed field. Nematode communities, phospholipid fatty acid (PLFA) biomarkers, and Soil properties (NH 4 + -N, NO 3 − -N, total N, total C, pH, P, bulk density and Soil texture) were measured, and riparian health ratings were scored. Environmental variables were obtained from publicly-available data sources (slope, elevation, available water capacity, erodability, hydraulic conductivity, exchangeable cation capacity, organic matter, clay and sand content and pH). The abundance and richness in most Food Web components were higher in grazed grasslands than in intensive agricultural fields. Consumers contributed less than their resources to the abundance and richness of the community in all channels. The association between richness and abundance for each component was strongest for the lowest trophic links (microbes, as inferred by PLFA) and weakest for the highest (predatory nematodes). The trophic interactions for the predator–prey and plant–herbivore channels were greater in the grassland than in the cropland. Fields for crops or grazing supported more interactions than the water’s edge in the plant–herbivore and microbivore channels. Connectance increased with the total richness of each community. Higher connectance within the microbivore and predator–prey Soil Food Web channels were associated with Soil NO 3 − -N and elevation respectively, which served as surrogate indicators of high and low agricultural intensification.
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form and function metabolic footprints of nematodes in the Soil Food Web
European Journal of Soil Biology, 2010Co-Authors: H FerrisAbstract:Metabolic footprints provide metrics for the magnitudes of ecosystem functions and services provided by component organisms of the Soil Food Web. Nematodes occupy various trophic roles and perform important functions within the Web. They are convenient indicators of similar functions performed by other organisms in the Web and are well-documented indicators of ecosystem condition. The generally vermiform shapes of nematodes, and the standardized morphometric characteristics used in their description, facilitate assessment of body volume and weight. Prescribed coefficients allow calculation of their carbon metabolism. Their production of body structure and eggs can be standardized for life course duration. Consequently, standardized metabolic activity levels, attributable to the abundance of nematodes performing various functional roles, can be calculated from existing and accessible morphometric data. Metabolic footprints of nematode assemblages provide measures of ecosystem services performed by each functional guild.
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contribution of nematodes to the structure and function of the Soil Food Web
Journal of Nematology, 2010Co-Authors: H FerrisAbstract:As carbon and energy flow through the Soil Food Web they are depleted by the metabolic and production functions of organisms. To be sustained, a "long" Food Web, with a large biomass at higher trophic levels, must receive a high rate of rhizode-position or detrital subsidy, or be top-populated by organisms of slow growth and long life cycle. Disturbed Soil Food Webs tend to be bottom heavy and recalcitrant to restoration due to the slow growth of upper predator populations, physical and chemical constraints of the Soil matrix, biological imbalances, and the relatively low mobility and invasion potential of Soil organisms. The functional roles of nematodes, determined by their metabolic and behavioral activities, may be categorized as ecosystem services, disservices or effect-neutral. Among the disservices attributable to nematodes are overgrazing, which diminishes services of prey organisms, and plant-damaging herbivory, which reduces carbon fixation and availability to other organisms in the Food Web. Unfortunately, management to ameliorate potential disservices of certain nematodes results in unintended but long-lasting diminution of the services of others. Beneficial roles of nematodes may be enhanced by environmental stewardship that fosters greater biodiversity and, consequently, complementarity and continuity of their services.
Parwinder S. Grewal - One of the best experts on this subject based on the ideXlab platform.
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effects of plant and animal waste based compost amendments on the Soil Food Web Soil properties and yield and quality of fresh market and processing carrot cultivars
Nematology, 2018Co-Authors: Alemayehu W Habteweld, Parwinder S. Grewal, Daniel C Brainard, A N Kravchenko, Haddish MelakeberhanAbstract:A substantial knowledge gap exists on how compost source and rate of application affect nematode community-based Soil Food Web structure, Soil health, Soil physiochemistry, and crop yield and quality in short- and full-season crops. We tested effects of plant (PC)- and animal (AC)-based compost at 1, 1.5 and 2× the standard nitrogen (N) rate on processing carrot ‘Cupar’ and fresh market ‘Sugarsnax 54’ (short-season crop) over 2-3 growing seasons. Low abundance of nematodes and domination of herbivores and bacterivores indicate that the field is biologically stressed. While outcomes of most measured parameters varied by compost source and/or rate, an increase in Soil Food Web structure with time was most consistent. A combination of the variable outcomes and correlation patterns suggest that a multifactor analysis may best quantify compost-driven changes in Soil ecosystems as opposed to looking for changes in a single parameter.
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relationship between Soil heavy metal contamination and Soil Food Web health in vacant lots slated for urban agriculture in two post industrial cities
Urban Ecosystems, 2015Co-Authors: Kuhuk Sharma, Parwinder S. Grewal, Zhiqiang ChengAbstract:Urban agriculture offers a means of obtaining healthy Food while making use of vacant land in cities. However, Soil contamination with heavy metals is a major concern for human health, Food safety and Soil Food Web health. In a previous study we reported on the human health risks of heavy metal contamination in Soil in 43 vacant lots in two low-income neighborhoods, Hough and Weinland Park, located in two post-industrial cities, Cleveland and Columbus (Ohio, USA), respectively. In this study, we determined the relationship between heavy metal concentrations and the Soil Food Web health using nematode community as a surrogate in the same lots. A general absence of higher trophic level omnivorous and predatory nematodes and an over-abundance of plant-parasitic nematodes indicated the disturbed nature of the urban Soil Food Web. When compared to the USEPA’s Ecological Soil Screening levels (Eco SSLs) only Zn was established as a metal of concern for Soil invertebrates which was also negatively associated with nematode Channel index in the multiple regression analysis. A combination of As, Cd, Cr, Soil texture and organic matter were significant factors associated with nematode abundance and community indices in the regression analysis. Bacteria and fungus feeding nematodes in the Hough neighborhood were negatively correlated with As and positively with Cd and Cr; whereas plant parasitic nematodes were positively correlated with Cr, % silt and active carbon content, perhaps due to the influence of these heavy metals on the nematode Food sources. In Weinland Park, neighborhood, channel index was negatively correlated to Cd and Zn concentration. Soil Pb and Zn concentrations that were elevated in these vacant lots beyond natural background concentrations did not show any significant associations with the nematode community; whereas the metals present within background concentration, i.e., As, Cd and Cr were correlated with the opportunistic bacteria and fungus feeding nematodes. Principal component analysis revealed different clustering of heavy metals, Soil properties and nematode parameters in the two cities, indicating unique associations. Results showed that Soil Cd and Cr concentrations were positively associated with the abundance of lower trophic level nematodes in both neighborhoods. Additionally, strong correlations between As, Cd, Cr, organic matter and Soil texture influenced the nematode population densities and should be further explored.
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habitat structure influences below ground biocontrol services a comparison between urban gardens and vacant lots
Landscape and Urban Planning, 2012Co-Authors: Priyanka Yadav, Kathy Duckworth, Parwinder S. GrewalAbstract:Urban agriculture offers a framework for local self-reliance by provisioning Food security, employment opportunities, and other community benefits. However, urban agriculture must rely on the supporting and regulating services of the Soil Food Web. Hence, we quantified belowground biocontrol activity in urban gardens and vacant lots in two post-industrial cities using an in situ insect baiting technique. Due to the differences in habitat structure, we hypothesized that belowground biocontrol services will differ between gardens and vacant lots and the influence of habitat structure would differ with the type of biocontrol organism. Results revealed that biocontrol activity, as assessed by % mortality of baited insects, varied between 51% and 98% with higher activity often recorded in vacant lots than gardens. Major contributions to bait insect mortality were by ants, followed by microbial pathogens and entomopathogenic nematodes, respectively. Ants showed higher (p < 0.0001) % mortality in vacant lots (60% ± 33.4%) than in urban gardens (33.3% ± 22.2%) whereas microbial pathogens exhibited higher (p < 0.0001) mortality in gardens (27.8% ± 15%) than vacant lots (8.3% ± 16.7%). Ants caused higher (p < 0.0001) mortality when larger-mesh size cages were used compared with the smaller-mesh size cages, but mortality by microbial pathogens did not differ with cage type. The high biocontrol activity indicates the resilience of the Soil Food Web in urban ecosystems and the differential effects of habitat structure on biocontrol activity can help guide landscape planning and vegetation management to enhance urban environments and boost local self-reliance.
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dynamics of the Soil nematode Food Web and nutrient pools under tall fescue lawns established on Soil matrices resulting from common urban development activities
Applied Soil Ecology, 2009Co-Authors: Zhiqiang Cheng, Parwinder S. GrewalAbstract:Human activity in urbanizing areas often disturbs the Soil profile, but little is known of its effects on subsequent Soil Food Web dynamics and biogeochemical cycling. We assessed dynamics of the Soil nematode Food Web and nutrient pools in tall fescue lawns created on either disturbed topSoil or subSoil, with or without compost amendment, and managed under three nitrogen fertilizer rates for one year. Overall, total nematodes and number of nematode genera were higher in topSoil than subSoil plots throughout the study. Compost amendment temporarily reduced number of nematode genera and this effect lasted for six months. Total number of nematodes also initially declined in the compost-amended plots, but increased within two months and remained high thereafter. The nematode Food Web enrichment index was initially lower in subSoil compared with topSoil plots and steadily increased overtime, but structure remained low in subSoil throughout the study period. The Food Web structure declined even in topSoil under turfgrass over time. Compost amendment only increased Food Web enrichment temporarily, but had little effect on structure. Nitrogen fertilizer had no effect on either enrichment or structure of the Food Web. Temporal faunal profile analysis indicated that the Soil Food Webs under turfgrass in all treatments converged over time, representing a highly enriched but poorly structured Food Web, and a strong bottom-up control on the Soil Food Web. Soil macronutrients Ca, P, K, total N, total C, microbial biomass, and Soil organic matter contents were higher in topSoil than subSoil, and were increased by compost amendment in both substrates. Soil P was only 18 μg/g in subSoil and it further declined by about 20% during the year. During the first two months after seeding, topSoil plots had lower turfgrass cover than subSoil plots (63 ± 5% and 95 ± 0%, respectively), but had higher weed cover (29 ± 5% and 2 ± 0%, respectively). After one year, turfgrass quality (greenness) was higher in topSoil than subSoil plots, in plots with compost amendment than those without, and in high N than low and no N plots. We conclude that anthropogenic activities, resulting in the loss of topSoil, can have a profound effect on the structure of the Soil Food Web, which may severely limit its capacity to support optimal nutrient cycling, plant growth, and other essential functions.
Sara Sanchezmoreno - One of the best experts on this subject based on the ideXlab platform.
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abundance diversity and connectance of Soil Food Web channels along environmental gradients in an agricultural landscape
Soil Biology & Biochemistry, 2011Co-Authors: Sara Sanchezmoreno, H Ferris, Anna Youngmathews, Steven W Culman, Louise E JacksonAbstract:Abstract Soil Food Webs respond to anthropogenic and natural environmental variables and gradients. We studied abundance, connectance (a measure of the trophic interactions within each channel), and diversity in three different channels of the Soil Food Web, each comprised of a resource-consumer pair: the microbivore channel (microbes and their nematode grazers), the plant–herbivore channel (plants and plant-feeding nematodes), and the predator–prey channel (predatory nematodes and their nematode prey), and their associations with different gradients in a heterogeneous agricultural landscape that consisted of intensive row crop agriculture and grazed non-irrigated grasslands in central California. Samples were taken at three positions in relation to water channels: water’s edge, bench above waterway, and the adjacent arable or grazed field. Nematode communities, phospholipid fatty acid (PLFA) biomarkers, and Soil properties (NH 4 + -N, NO 3 − -N, total N, total C, pH, P, bulk density and Soil texture) were measured, and riparian health ratings were scored. Environmental variables were obtained from publicly-available data sources (slope, elevation, available water capacity, erodability, hydraulic conductivity, exchangeable cation capacity, organic matter, clay and sand content and pH). The abundance and richness in most Food Web components were higher in grazed grasslands than in intensive agricultural fields. Consumers contributed less than their resources to the abundance and richness of the community in all channels. The association between richness and abundance for each component was strongest for the lowest trophic links (microbes, as inferred by PLFA) and weakest for the highest (predatory nematodes). The trophic interactions for the predator–prey and plant–herbivore channels were greater in the grassland than in the cropland. Fields for crops or grazing supported more interactions than the water’s edge in the plant–herbivore and microbivore channels. Connectance increased with the total richness of each community. Higher connectance within the microbivore and predator–prey Soil Food Web channels were associated with Soil NO 3 − -N and elevation respectively, which served as surrogate indicators of high and low agricultural intensification.
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effects of agricultural management on nematode mite assemblages Soil Food Web indices as predictors of mite community composition
Applied Soil Ecology, 2009Co-Authors: Sara Sanchezmoreno, H Ferris, Nicole L Nicola, Frank G ZalomAbstract:Abstract 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.
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nematode diversity Food Web condition and chemical and physical properties in different Soil habitats of an organic farm
Biology and Fertility of Soils, 2008Co-Authors: Sara Sanchezmoreno, H Ferris, Sean M Smukler, Anthony T Ogeen, Louise E JacksonAbstract:The aim of this paper was to assess biodiversity among different habitats of an organic farm and the relationships between some Soil properties, nematode taxonomic diversity, and Soil Food Web condition. Eight habitats were studied in the farm: ponds, ditches, a riparian corridor, hedgerows, and four agricultural fields (mustard, oats, fallow, and legumes). The undisturbed riparian corridor had higher Soil \({\text{NO}}_{\text{3}}^ - - {\text{N}}\) and \({\text{NH}}_4^ + - {\text{N}}\) concentrations, and potentially mineralizable N and higher abundances of bacterivore nematodes and longer Food Webs. Canonical correlation analysis showed associations between habitats and nematode trophic groups: predatory and bacterial-feeding nematodes in the riparian corridor and hedgerows, omnivore nematodes in the ponds and ditches, and fungal-feeding nematodes in the legume field. Soil chemical and physical properties mirrored the aboveground farm patterns and were more similar among habitats that were or had been cultivated, compared to the riparian corridor. Soil Food Web indices, based on functional analysis of nematode faunal composition, reflected the aboveground landscape heterogeneity. Discriminant analysis indicated that Soil Food Web indices separated the two most disturbed habitats (ponds and tailwater ditches) from the two least disturbed habitats (the riparian corridor and hedgerows). The indices correlated with Soil functioning as inferred by Soil properties. Abundance of nematode taxa was not associated with aboveground landscape patterns. The complexity of the Soil Food Web may have been influenced by (1) environmental factors that differed between years, (2) different time periods since disturbance in the various habitats, and (3) movement of nutrients and organisms by water flow between habitats in the farmscale.
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role of tardigrades in the suppressive service of a Soil Food Web
Agriculture Ecosystems & Environment, 2008Co-Authors: Sara Sanchezmoreno, H Ferris, Noemi GuilAbstract:In a previous study, Soil suppressiveness to populations of the plant-parasitic nematode Meloidogyne incognita was correlated with abundance of omnivore and predatory nematodes. In the current study, performance of the regulatory function switched from nematodes to tardigrades when predatory nematodes disappeared due to predation pressure and/or unfavorable environmental conditions. Two tardigrade species, Macrobiotus richtersi and M. harmsworthi effectively suppressed nematode populations. While there were significant changes in the Soil Food Web over time, the regulatory function was maintained. Under experimental conditions, M. richtersi consumed 61 nematodes per day, indicating that tardigrades may significantly reduce nematode biomass. The impact of tardigrades on Soil Food Web dynamics and their relationships with nematodes are discussed.
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suppressive service of the Soil Food Web effects of environmental management
Agriculture Ecosystems & Environment, 2007Co-Authors: Sara Sanchezmoreno, H FerrisAbstract:Soil Food Webs perform the important ecosystem services necessary to maintain both agricultural productivity and ecosystem health. Higher trophic levels in Soil Food Webs can play a role suppressing plant parasites and affecting nutrient dynamics by modifying abundance of intermediate consumers. Natural and agricultural landscapes were sampled to compare Soil faunal structure. Top-down Soil suppressiveness of a parasitic nematode, Meloidogyne incognita, was determined in laboratory assay. Five treatments, including two nitrogen fertilizers, two herbicides and simulated tillage were established in experimental microcosms to evaluate the effects of simulated agricultural practices on top-down suppressiveness. Soil Food Web indices, based on the composition of the nematode fauna, were calculated to infer Soil Food Web condition. Long and complex Soil Food Webs in natural areas, with more trophic links and abundant predatory nematodes, effectively suppressed plant–parasite populations, while disturbed communities in agricultural Soils did not. Soil suppressiveness was related to the ratio of predators to prey and to the prevalence of omnivore and predator species. Agricultural management led to a reduction in the suppressive capacity of the Soil Food Web. Abundance of predatory nematodes was related to Soil NH4+, probably due to excretory products of nematodes and other organisms grazing on microbes. Soil suppressiveness, Soil Food Web dynamics and agricultural management are strongly inter-related.
David A Wardle - One of the best experts on this subject based on the ideXlab platform.
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trickle down effects of aboveground trophic cascades on the Soil Food Web
Oikos, 2005Co-Authors: David A Wardle, Wendy M Williamson, G W Yeates, Karen I BonnerAbstract:Trophic cascades are increasingly being regarded as important features of aboveground and belowground Food Webs, but the effects of aboveground cascades on Soil Food Webs, and vice versa, remains essentially unexplored. We conducted an experiment consisting of model synthesised communities containing grassland plant and invertebrate species, in which treatments included Soil only, Soil+plants, Soil+plants+aphids, and Soil+ plants+aphids+predators; predator treatments consisted of the lacewing Micromus tasmaniae and ladybird beetle Coccinella undecimpunctata added either singly or in combination. Addition of Micromus largely reversed the negative effects of aphids on plant biomass, while both of the predator species caused large changes in the relative abundances of dominant plant species. Predators of aphids also affected several components of the belowground subsystem. Micromus had positive indirect effects on the primary consumer of the Soil decomposer Food Web (microflora), probably through promoting greater input of basal resources to the decomposer subsystem. Predator treatments also influenced densities of the tertiary consumers of the Soil Food Web (top predatory nematodes), most likely through inducing changes in plant community composition and therefore the quality of resource input to the Soil. The secondary consumers of the Soil Food Web (microbe-feeding nematodes) were, however, unresponsive. The fact that some trophic levels of the Soil Food Web but not others responded to aboveground manipulations is explicable in terms of top-down and bottom-up forces differentially regulating different belowground trophic levels. Addition of aphids also influenced microbial community structure, promoted Soil bacteria at the expense of fungi, and enhanced the diversity of herbivorous nematodes; in all cases these effects were at least partially reversed by addition of Micromus. These results in tandem point to upper level consumers in aboveground Food Webs as a potential driver of the belowground subsystem, and provide evidence that predator-induced trophic cascades aboveground can have effects that trickle through Soil Food Webs.
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Trickle‐down effects of aboveground trophic cascades on the Soil Food Web
Oikos, 2005Co-Authors: David A Wardle, Wendy M Williamson, G W Yeates, Karen I BonnerAbstract:Trophic cascades are increasingly being regarded as important features of aboveground and belowground Food Webs, but the effects of aboveground cascades on Soil Food Webs, and vice versa, remains essentially unexplored. We conducted an experiment consisting of model synthesised communities containing grassland plant and invertebrate species, in which treatments included Soil only, Soil+plants, Soil+plants+aphids, and Soil+ plants+aphids+predators; predator treatments consisted of the lacewing Micromus tasmaniae and ladybird beetle Coccinella undecimpunctata added either singly or in combination. Addition of Micromus largely reversed the negative effects of aphids on plant biomass, while both of the predator species caused large changes in the relative abundances of dominant plant species. Predators of aphids also affected several components of the belowground subsystem. Micromus had positive indirect effects on the primary consumer of the Soil decomposer Food Web (microflora), probably through promoting greater input of basal resources to the decomposer subsystem. Predator treatments also influenced densities of the tertiary consumers of the Soil Food Web (top predatory nematodes), most likely through inducing changes in plant community composition and therefore the quality of resource input to the Soil. The secondary consumers of the Soil Food Web (microbe-feeding nematodes) were, however, unresponsive. The fact that some trophic levels of the Soil Food Web but not others responded to aboveground manipulations is explicable in terms of top-down and bottom-up forces differentially regulating different belowground trophic levels. Addition of aphids also influenced microbial community structure, promoted Soil bacteria at the expense of fungi, and enhanced the diversity of herbivorous nematodes; in all cases these effects were at least partially reversed by addition of Micromus. These results in tandem point to upper level consumers in aboveground Food Webs as a potential driver of the belowground subsystem, and provide evidence that predator-induced trophic cascades aboveground can have effects that trickle through Soil Food Webs.
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linking aboveground and belowground communities the indirect influence of aphid species identity and diversity on a three trophic level Soil Food Web
Oikos, 2004Co-Authors: David A Wardle, Wendy M Williamson, Karen I Bonner, G W Yeates, G M BarkerAbstract:There has been a growing recent interest in how foliar herbivory may indirectly affect the belowground sub-system, but little is known about the belowground consequences of the identity, species composition or diversity of foliar herbivores. We performed an experiment, utilising model grassland communities containing three plant species, in which treatments consisted of addition of each of eight aphid species in single and in two- four- and eight-species combinations, as well as an aphid-free treatment. While aphid species treatments did not affect total plant biomass or productivity, aphid species identity had important effects on the relative abundance of the three plant species. This in turn affected the abundances of each of three groups of secondary consumers in the Soil Food Web (bacterial- and fungal-feeding nematodes, and enchytraeids) but not primary consumers (microbes, herbivorous nematodes) or tertiary consumers (predatory nematodes). The fact that some trophic levels responded to treatments while others did not is consistent with trophic dynamic theory. Aphid species treatments also affected the community composition within each of the herbivorous, microbe-feeding and top predatory nematode groups, as well as diversity within the first two of these groups. However, aphid species diversity per se had few effects. There were specific instances in which specific aboveground and belowground response variables in two aphid species combinations differed significantly from those in both of the corresponding single aphid species treatments (apparently as a consequence of resource use complementarity between coexisting aphid species), but no instance in which increasing aphid diversity beyond two species had any effect. Our results provide evidence that the identity of aboveground consumers can have effects that propagate through multiple trophic levels in Soil Food Webs in terms of consumer abundance, and composition and diversity within trophic levels.
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effects of defoliation intensity on Soil Food Web properties in an experimental grassland community
Oikos, 2001Co-Authors: Juha Mikola, David A Wardle, G W Yeates, G M Barker, Karen I BonnerAbstract:We established a greenhouse experiment based on replicated mini-ecosystems to evaluate the effects of defoliation intensity on Soil Food-Web properties in grasslands. Plant communities, composed of white clover (Trifolium repens), perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata) with well-established root and shoot systems, were subjected to five defoliation intensity treatments: no trimming (defoliation intensity 0, or DI 0), and trimming of all plant material to 35 cm (Dl 1), 25 cm (DI 2), 15 cm (DI 3) and 10 cm (Dl 4) above Soil surface every second week for 14 weeks. Intensification of defoliation reduced shoot production and standing shoot and root mass of plant communities but increased their root to shoot ratio. Soil microbial activity and biomass decreased with intensification of defoliation. Concentrations of NO 3 -N in Soil steadily increased with intensifying defoliation, whereas NH 4 -N concentrations did not vary between treatments. Numbers of microbi-detritivorous enchytraeids, bacterial-feeding rotifers and bacterial-feeding nematodes steadily increased with intensifying defoliation, while the abundance of fungal-feeding nematodes was significantly enhanced only in Dl 3 and DI 4 relative to DI 0. The abundance of herbivorous nematodes per unit Soil mass was lower in DI 3 and DI 4 than in DI 0, Dl I and DI 2. but when calculated per unit root mass, their abundance tended to increase with defoliation intensity, The abundance of omnivorous and predatory nematodes appeared to be highest in the most intensely defoliated systems The ratio of abundance of fungal-feeding nematodes to that of bacterial-feeding nematodes was not significantly affected by defoliation intensity. The results s infer that defoliation intensity may significantly alter the structure of Soil Food Webs in grasslands, and that defoliation per se is able to induce patterns observed in grazing studies in the field. The results did not support hypotheses that defoliation per se would cause a shift between the bacterial-based and fungal-based energy channels in the decomposer Food Web, or that herbivore and detritivore densities in Soil would be highest under intermediate defoliation. Furthermore, our data for microbes and microbial feeders implies that the effects of defoliation intensity on Soil Food-Web structure may depend on the duration of defoliation and are therefore likely to be dynamic rather than constant in nature.
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Effects of defoliation intensity on Soil Food‐Web properties in an experimental grassland community
Oikos, 2001Co-Authors: Juha Mikola, David A Wardle, G W Yeates, G M Barker, Karen I BonnerAbstract:We established a greenhouse experiment based on replicated mini-ecosystems to evaluate the effects of defoliation intensity on Soil Food-Web properties in grasslands. Plant communities, composed of white clover (Trifolium repens), perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata) with well-established root and shoot systems, were subjected to five defoliation intensity treatments: no trimming (defoliation intensity 0, or DI 0), and trimming of all plant material to 35 cm (Dl 1), 25 cm (DI 2), 15 cm (DI 3) and 10 cm (Dl 4) above Soil surface every second week for 14 weeks. Intensification of defoliation reduced shoot production and standing shoot and root mass of plant communities but increased their root to shoot ratio. Soil microbial activity and biomass decreased with intensification of defoliation. Concentrations of NO 3 -N in Soil steadily increased with intensifying defoliation, whereas NH 4 -N concentrations did not vary between treatments. Numbers of microbi-detritivorous enchytraeids, bacterial-feeding rotifers and bacterial-feeding nematodes steadily increased with intensifying defoliation, while the abundance of fungal-feeding nematodes was significantly enhanced only in Dl 3 and DI 4 relative to DI 0. The abundance of herbivorous nematodes per unit Soil mass was lower in DI 3 and DI 4 than in DI 0, Dl I and DI 2. but when calculated per unit root mass, their abundance tended to increase with defoliation intensity, The abundance of omnivorous and predatory nematodes appeared to be highest in the most intensely defoliated systems The ratio of abundance of fungal-feeding nematodes to that of bacterial-feeding nematodes was not significantly affected by defoliation intensity. The results s infer that defoliation intensity may significantly alter the structure of Soil Food Webs in grasslands, and that defoliation per se is able to induce patterns observed in grazing studies in the field. The results did not support hypotheses that defoliation per se would cause a shift between the bacterial-based and fungal-based energy channels in the decomposer Food Web, or that herbivore and detritivore densities in Soil would be highest under intermediate defoliation. Furthermore, our data for microbes and microbial feeders implies that the effects of defoliation intensity on Soil Food-Web structure may depend on the duration of defoliation and are therefore likely to be dynamic rather than constant in nature.
Karen I Bonner - One of the best experts on this subject based on the ideXlab platform.
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trickle down effects of aboveground trophic cascades on the Soil Food Web
Oikos, 2005Co-Authors: David A Wardle, Wendy M Williamson, G W Yeates, Karen I BonnerAbstract:Trophic cascades are increasingly being regarded as important features of aboveground and belowground Food Webs, but the effects of aboveground cascades on Soil Food Webs, and vice versa, remains essentially unexplored. We conducted an experiment consisting of model synthesised communities containing grassland plant and invertebrate species, in which treatments included Soil only, Soil+plants, Soil+plants+aphids, and Soil+ plants+aphids+predators; predator treatments consisted of the lacewing Micromus tasmaniae and ladybird beetle Coccinella undecimpunctata added either singly or in combination. Addition of Micromus largely reversed the negative effects of aphids on plant biomass, while both of the predator species caused large changes in the relative abundances of dominant plant species. Predators of aphids also affected several components of the belowground subsystem. Micromus had positive indirect effects on the primary consumer of the Soil decomposer Food Web (microflora), probably through promoting greater input of basal resources to the decomposer subsystem. Predator treatments also influenced densities of the tertiary consumers of the Soil Food Web (top predatory nematodes), most likely through inducing changes in plant community composition and therefore the quality of resource input to the Soil. The secondary consumers of the Soil Food Web (microbe-feeding nematodes) were, however, unresponsive. The fact that some trophic levels of the Soil Food Web but not others responded to aboveground manipulations is explicable in terms of top-down and bottom-up forces differentially regulating different belowground trophic levels. Addition of aphids also influenced microbial community structure, promoted Soil bacteria at the expense of fungi, and enhanced the diversity of herbivorous nematodes; in all cases these effects were at least partially reversed by addition of Micromus. These results in tandem point to upper level consumers in aboveground Food Webs as a potential driver of the belowground subsystem, and provide evidence that predator-induced trophic cascades aboveground can have effects that trickle through Soil Food Webs.
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Trickle‐down effects of aboveground trophic cascades on the Soil Food Web
Oikos, 2005Co-Authors: David A Wardle, Wendy M Williamson, G W Yeates, Karen I BonnerAbstract:Trophic cascades are increasingly being regarded as important features of aboveground and belowground Food Webs, but the effects of aboveground cascades on Soil Food Webs, and vice versa, remains essentially unexplored. We conducted an experiment consisting of model synthesised communities containing grassland plant and invertebrate species, in which treatments included Soil only, Soil+plants, Soil+plants+aphids, and Soil+ plants+aphids+predators; predator treatments consisted of the lacewing Micromus tasmaniae and ladybird beetle Coccinella undecimpunctata added either singly or in combination. Addition of Micromus largely reversed the negative effects of aphids on plant biomass, while both of the predator species caused large changes in the relative abundances of dominant plant species. Predators of aphids also affected several components of the belowground subsystem. Micromus had positive indirect effects on the primary consumer of the Soil decomposer Food Web (microflora), probably through promoting greater input of basal resources to the decomposer subsystem. Predator treatments also influenced densities of the tertiary consumers of the Soil Food Web (top predatory nematodes), most likely through inducing changes in plant community composition and therefore the quality of resource input to the Soil. The secondary consumers of the Soil Food Web (microbe-feeding nematodes) were, however, unresponsive. The fact that some trophic levels of the Soil Food Web but not others responded to aboveground manipulations is explicable in terms of top-down and bottom-up forces differentially regulating different belowground trophic levels. Addition of aphids also influenced microbial community structure, promoted Soil bacteria at the expense of fungi, and enhanced the diversity of herbivorous nematodes; in all cases these effects were at least partially reversed by addition of Micromus. These results in tandem point to upper level consumers in aboveground Food Webs as a potential driver of the belowground subsystem, and provide evidence that predator-induced trophic cascades aboveground can have effects that trickle through Soil Food Webs.
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linking aboveground and belowground communities the indirect influence of aphid species identity and diversity on a three trophic level Soil Food Web
Oikos, 2004Co-Authors: David A Wardle, Wendy M Williamson, Karen I Bonner, G W Yeates, G M BarkerAbstract:There has been a growing recent interest in how foliar herbivory may indirectly affect the belowground sub-system, but little is known about the belowground consequences of the identity, species composition or diversity of foliar herbivores. We performed an experiment, utilising model grassland communities containing three plant species, in which treatments consisted of addition of each of eight aphid species in single and in two- four- and eight-species combinations, as well as an aphid-free treatment. While aphid species treatments did not affect total plant biomass or productivity, aphid species identity had important effects on the relative abundance of the three plant species. This in turn affected the abundances of each of three groups of secondary consumers in the Soil Food Web (bacterial- and fungal-feeding nematodes, and enchytraeids) but not primary consumers (microbes, herbivorous nematodes) or tertiary consumers (predatory nematodes). The fact that some trophic levels responded to treatments while others did not is consistent with trophic dynamic theory. Aphid species treatments also affected the community composition within each of the herbivorous, microbe-feeding and top predatory nematode groups, as well as diversity within the first two of these groups. However, aphid species diversity per se had few effects. There were specific instances in which specific aboveground and belowground response variables in two aphid species combinations differed significantly from those in both of the corresponding single aphid species treatments (apparently as a consequence of resource use complementarity between coexisting aphid species), but no instance in which increasing aphid diversity beyond two species had any effect. Our results provide evidence that the identity of aboveground consumers can have effects that propagate through multiple trophic levels in Soil Food Webs in terms of consumer abundance, and composition and diversity within trophic levels.
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effects of defoliation intensity on Soil Food Web properties in an experimental grassland community
Oikos, 2001Co-Authors: Juha Mikola, David A Wardle, G W Yeates, G M Barker, Karen I BonnerAbstract:We established a greenhouse experiment based on replicated mini-ecosystems to evaluate the effects of defoliation intensity on Soil Food-Web properties in grasslands. Plant communities, composed of white clover (Trifolium repens), perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata) with well-established root and shoot systems, were subjected to five defoliation intensity treatments: no trimming (defoliation intensity 0, or DI 0), and trimming of all plant material to 35 cm (Dl 1), 25 cm (DI 2), 15 cm (DI 3) and 10 cm (Dl 4) above Soil surface every second week for 14 weeks. Intensification of defoliation reduced shoot production and standing shoot and root mass of plant communities but increased their root to shoot ratio. Soil microbial activity and biomass decreased with intensification of defoliation. Concentrations of NO 3 -N in Soil steadily increased with intensifying defoliation, whereas NH 4 -N concentrations did not vary between treatments. Numbers of microbi-detritivorous enchytraeids, bacterial-feeding rotifers and bacterial-feeding nematodes steadily increased with intensifying defoliation, while the abundance of fungal-feeding nematodes was significantly enhanced only in Dl 3 and DI 4 relative to DI 0. The abundance of herbivorous nematodes per unit Soil mass was lower in DI 3 and DI 4 than in DI 0, Dl I and DI 2. but when calculated per unit root mass, their abundance tended to increase with defoliation intensity, The abundance of omnivorous and predatory nematodes appeared to be highest in the most intensely defoliated systems The ratio of abundance of fungal-feeding nematodes to that of bacterial-feeding nematodes was not significantly affected by defoliation intensity. The results s infer that defoliation intensity may significantly alter the structure of Soil Food Webs in grasslands, and that defoliation per se is able to induce patterns observed in grazing studies in the field. The results did not support hypotheses that defoliation per se would cause a shift between the bacterial-based and fungal-based energy channels in the decomposer Food Web, or that herbivore and detritivore densities in Soil would be highest under intermediate defoliation. Furthermore, our data for microbes and microbial feeders implies that the effects of defoliation intensity on Soil Food-Web structure may depend on the duration of defoliation and are therefore likely to be dynamic rather than constant in nature.
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Effects of defoliation intensity on Soil Food‐Web properties in an experimental grassland community
Oikos, 2001Co-Authors: Juha Mikola, David A Wardle, G W Yeates, G M Barker, Karen I BonnerAbstract:We established a greenhouse experiment based on replicated mini-ecosystems to evaluate the effects of defoliation intensity on Soil Food-Web properties in grasslands. Plant communities, composed of white clover (Trifolium repens), perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata) with well-established root and shoot systems, were subjected to five defoliation intensity treatments: no trimming (defoliation intensity 0, or DI 0), and trimming of all plant material to 35 cm (Dl 1), 25 cm (DI 2), 15 cm (DI 3) and 10 cm (Dl 4) above Soil surface every second week for 14 weeks. Intensification of defoliation reduced shoot production and standing shoot and root mass of plant communities but increased their root to shoot ratio. Soil microbial activity and biomass decreased with intensification of defoliation. Concentrations of NO 3 -N in Soil steadily increased with intensifying defoliation, whereas NH 4 -N concentrations did not vary between treatments. Numbers of microbi-detritivorous enchytraeids, bacterial-feeding rotifers and bacterial-feeding nematodes steadily increased with intensifying defoliation, while the abundance of fungal-feeding nematodes was significantly enhanced only in Dl 3 and DI 4 relative to DI 0. The abundance of herbivorous nematodes per unit Soil mass was lower in DI 3 and DI 4 than in DI 0, Dl I and DI 2. but when calculated per unit root mass, their abundance tended to increase with defoliation intensity, The abundance of omnivorous and predatory nematodes appeared to be highest in the most intensely defoliated systems The ratio of abundance of fungal-feeding nematodes to that of bacterial-feeding nematodes was not significantly affected by defoliation intensity. The results s infer that defoliation intensity may significantly alter the structure of Soil Food Webs in grasslands, and that defoliation per se is able to induce patterns observed in grazing studies in the field. The results did not support hypotheses that defoliation per se would cause a shift between the bacterial-based and fungal-based energy channels in the decomposer Food Web, or that herbivore and detritivore densities in Soil would be highest under intermediate defoliation. Furthermore, our data for microbes and microbial feeders implies that the effects of defoliation intensity on Soil Food-Web structure may depend on the duration of defoliation and are therefore likely to be dynamic rather than constant in nature.
