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The role of meticillin-susceptible Staphylococcus aureus (MSSA) colonization of healthcare workers (HCWs), patients and the hospital environment in MSSA transmission events (TEs) is poorly understood.The role of meticillin-resistant Staphylococcus aureus (MRSA) was investigated recently under non-outbreak conditions in a large hospital with a history of endemic MRSA over 2 years using whole-genome sequencing (WGS). Numerous potential MRSA TEs were identified. The present study investigated MSSA TEs from the same sources during the same 2-year hospital study.HCW (N=326) and patient (N=388) volunteers on nine wards were tested for nasal and oral MSSA colonization over 2 years. Near-patient environment (N=1164), high-frequency touch sites (N=810) and air (N=445) samples were screened for MSSA. Representative MSSA and clinical isolates were sequenced and analysed by core genome multi-locus sequence typing. Closely related isolates (≤24 allelic differences) were segregated into related isolate groups (RIGs). Potential TEs involving MSSA in RIGs from HCWs, patients and patient infections were identified in combination with epidemiological data.In total, 635 MSSA were recovered: clinical isolates (N=82), HCWs (N=170), patients (N=120), and environmental isolates (N=263). Twenty-four clonal complexes (CCs) were identified among 406/635 MSSA sequenced, of which 183/406 segregated into 59 RIGs. Numerous potential HCW-to-patient, HCW-to-HCW and patient-to-patient TEs were identified, predominantly among CC5-MSSA, CC30-MSSA and CC45-MSSA. HCW, patient, clinical and environmental isolates were identified in 33, 24, six and 32 RIGs, respectively, with 19/32 of these containing MSSA related to HCW and/or patient isolates.WGS detected numerous potential hospital MSSA TEs involving HCWs, patients and environmental contamination under non-outbreak conditions.

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Soil biota refers to a highly diverse assemblage of organisms that spend at least part of their life cycle in or on the soil. As their numerical diversity suggests, soil biota undertake a wide range of functions, including the detrimental activities of pathogens, parasites, and other agricultural pests. Fertilizer, tillage, and pesticide inputs account for as much as 33, 17, and 10 percent, respectively, of total energy use in US agriculture. Soil organisms may inhabit surface layers of soil and litter or deeper soil horizons, or move throughout the soil profile. The total biomass of the soil biota constitutes a relatively small fraction of total soil organic matter. The functioning of detritus food webs is driven by inputs of organic matter. Cultivation of undisturbed soil brings about a number of changes in community structure and activity of indigenous soil biota. Some physical and chemical manipulations alter habitat conditions directly and may be useful for stimulating or suppressing biotic activity.

Background Parents play a pivotal role in adolescent sexual health and Human Papillomavirus (HPV) vaccination. Nurses are on the frontlines of healthcare and play a critical role in promoting HPV vaccination and parent-child sexual health communication. We enhanced the Families Talking Together (FTT) parent-based sexual health curriculum to include adolescent vaccinations herein, FTT + HPV, and trained student nurses to provide a strong HPV vaccination and parent-child sexual health communication endorsement. Methods Using a randomized attention-controlled trial design, we examined the efficacy of FTT + HPV among 519 parents and their 11–14 year old youth recruited from medically underserved communities between 2015 and 2018. Participants were recruited from 22 after-school programs (e.g., Boys and Girls Clubs) and 19 charter schools. For parents, we examined protective factors including parent-child sexual health communication and parental involvement. For youth, we examined sexual health knowledge, parent-child sexual health communication, and parent-child connectedness. To assess HPV vaccination initiation and completion, we searched IMMTRAC immunization registry records for 85% of youth and used parental report for youth without registry records. Group differences were calculated using the estimated mean difference at one- and six months post-intervention with significance set at the p Results Baseline rates of HPV vaccination were low at 55.7%. No significant difference between the groups was seen in vaccination initiation or completion rates by one-month post-intervention. However, by six-months post intervention, there was a significant difference between the groups with 70.3% of the intervention group initiating the HPV vaccination series vs. 60.6% for the control group (p = 0.02). No difference between the groups was found for HPV series completion at six-months. There were significant differences in condom knowledge (p = 0.04), parent-child connectedness (p = 0.04), and communication frequency (p = 0.001) with greater improvement in the intervention vs. the control group. Rates of sexual activity remained low in both groups throughout the six-month follow-up period. Conclusion A brief parent-based adolescent sexual health and HPV vaccination intervention delivered by student nurses can improve sexual health outcomes including protective parental factors, adolescent sexual health knowledge, and HPV vaccination initiation rates. Trial registration ClinicalTrials.gov Identifier: NCT02600884. Prospectively registered September 1, 2015.

Gas exchange and carbon allocation patterns were studied in two populations of Panicum coloratum, an Africa C-4 grass. The plants were grown in split-root pots, containing partially sterilized soil, with one side either inoculated (I) or not inoculated (NI) with a vesicular arbuscular (VA) mycorrhizal Fungus, Gigaspora margarita. Net carbon exchange rates (CER) and stomatal conductances were measured with conventional gas exchange apparatus, and carbon assimilation, translocation, and allocation were measured using photosynthetically-fixed

Soils are one of the great unknown realms on earth, despite decades of extensive research. We still see soils “through a ped darkly”. This opacity in milieu and understanding rewards innovative study, however, as soils are indeed “complex adaptive systems”, and show very sophisticated levels of self-organization. Viewed historically, soil ecological studies have progressed from what major groups of biota are present, what is their biomass, and what major processes occur. More recent studies have delineated multi-trophic interactions, extending both above- and below-ground, as well as specifically-targeted studies of substrates and organisms that are involved in the development and function of suppressive soils. One of the great unknowns in soil ecology is a fuller understanding of the complete array of predatory biota. Soils are teeming with organisms in all three Domains, but are also rife with many viruses infecting Archaea, Bacteria and Eukarya, meaning that they need more study in soil processes. Pursuing a more holistic approach including viral biology and ecology may enable us to more capably manage our soils that have supported the biosphere so much over the millennia. Looking into the future, the opportunity to exploit soil biodiversity in the context of ecosystem development should pay considerable dividends. Using chronosequence analysis, the relationships between soil biodiversity and ecosystem function are beginning to be understood. The interplays of aboveground and belowground herbivores on plant function and feedbacks on the attraction of the herbivores’ natural enemies. Finally, management of the plant-soil–microbial-faunal system via varied organic amendments shows possibilities in the study and management of suppressive soils.

Summary Soils have often been viewed as a black box. Soil biology is difficult to study with the precision we would wish, due to the presence of considerable soil heterogeneity, a huge diversity of organisms, and a plethora of interacting processes taking place in a complex physical-chemical environment. We have isolated a tiny fraction of the known organisms, and the possible interactions of soil parent materials, landscape, land use, depth and time with the biota mean that we are to some extent still fumbling in the dark. There have been great advances, but we argue that the pace of advance could be faster. To progress, science needs new theory and concepts but also acceptable methodologies. Coherent and generally accepted theoretical knowledge exists in many areas, but there is a shortage of valid and exact methods to test new and sometimes even old hypotheses. New methods add knowledge, but they also can add to the confusion if they are not tied to the existing knowledge base. We speculate on how to improve soil biology through improving the way we perform and interpret research. Can we deal with soil variability? Can we measure the critical variables with adequate precision to test our hypotheses? Can we avoid reinventing the wheel? Can we find a balance between the freedom to test new and maybe even controversial ideas and the control and direction of research required by society?

Historically, a large percentage of land area in the Piedmont of the southeastern USA was under intensive agricultural management for the production of cotton. This intensive farming resulted in massive erosion, and general degradation of soil resources until insect pests and poor economic conditions forced large-scale abandonment of farmland around the 1930s. In subsequent decades, there have been four predominant land-uses in the region, and we sampled soil macroinvertebrates from three replicate sites of cultivated fields, grass-dominated fields, loblolly pine stands, and remnant hardwood stands for a period of 2 years, with the objective of examining soil invertebrate community composition in relation to these long-term land-uses. At each site we dug three or four soil pits that were 30 × 30 cm to a depth of 15 cm, and sorted the soil volume by hand for a time not more than 1 person h, collecting all invertebrates ~5 mm in length or larger. We recorded abundance data for all invertebrate taxa collected, and we calculated community indices including diversity, evenness, rank abundance and percent similarity in order to identify patterns of community assemblage within each land-use type. Results suggest that soils in hardwood stands support the most taxonomically diverse macroinvertebrate communities followed by pine stands, pastures, and cultivated fields in order of decreasing diversity. For earthworms, Diplocardia spp. (North American megascolecids) were most abundant in the hardwood stands, but sometimes made up a substantial fraction of the community in other land-uses; whereas lumbricid earthworms (primarily introduced Apporectodea spp.) were most abundant in the cultivated and pasture soils, or showed no consistent habitat preference (native Bimastos spp.). Scarab beetles (larvae and adults) were common in all four systems, but reached the highest densities in cultivated and grass sites. Carabid beetle larvae were collected most often from cultivated soils. Several taxa were collected either exclusively or predominantly from forested sites, including diplopods, chilopods, gastropods, and several taxa of Diptera. These results indicate that long-term soil disturbance and the attendant differences in vegetation structure have profoundly influenced the community composition of invertebrates in Southern Piedmont soils, and that more intense disturbance results in a less diverse invertebrate community composed of a few, frequently non-native, disturbance-tolerant taxa.

Understanding many soil processes, including the accumulation of organic matter and the formation and loss of soil aggregates, requires research that is conducted over decadal time periods. The dynamics of soil organic matter and soil fauna at the Horseshoe Bend (HSB) agroecosystem site in Georgia have been studied in replicated experimental plots since 1978. The experimental treatments (no-tillage (NT) and conventional-tillage (CT) regimes) are continuing to diverge in amounts and distribution of SOM in the soil profiles of HSB. Our current research focuses on two major areas: 1) long-term measurements of the gradually-increasing base of soil organic matter from C3-pathway plants, in crop rotations that have been in effect since 1997; 2) following the production, accumulation, fate and ecological effects of the Bt (Bacillus thuringiensis) proteins from the summer planting of Bt (and non-Bt) cotton in subplots within our main plots. The variation in the size of soil aggregates may influence the sequestration of Bt toxins, and their breakdown products, within soils. NT management systems at HSB generate an increasing proportion of soil macroaggregates in comparison to the markedly reduced macroaggregates in our CT plots. We suggest that NT systems may sequester more Bt-related products than will CT plots.

Enchytraeids are abundant in many different agricultural systems. However, their role in decomposition processes and nitrogen mineralization is not well understood. This study was conducted to evaluate the influence of a common enchytraeid (Enchytraeus minutus, Nielsen and Christensen 1961) on these processes in two soils (sandy clay loam and loamy sand) under two different litter placement treatments (buried versus surface placed) in a laboratory experiment. Forty-five enchytraeids were added to half of the constructed jars. Every 4 weeks (up to 112 days) three jars of each soil-litter-enchytraeid treatment were destructively sampled for determination of enchytraeid abundance, microbial biomass, dissolved organic carbon (DOC), and floatable particulate organic matter (FLPOM)-C and -N. Soil respiration and N2O fluxes were measured at biweekly intervals. At the end of the experiment less DOC was present in the sandy clay loam treatments with enchytraeids. The influence of enchytraeids on denitrification rates, depended on soil texture and litter placement. In the Buried Litter treatment enchytraeids caused an increase in the N2O-flux in the loamy sand soil and a decrease in the sandy clay loam soil. Variation in the flux was large, therefore the differences in enchytraeid and non-enchytraeid treatments were not significant. Essentially no denitrification occurred in the Surface Litter treatments. Enchytraeids affected decomposition by decreasing the amount of floatable POM in the soils. They increased the mobilization of nitrogen, resulting in larger amounts of inorganic-N in the soil solution after 112 days. Through immobilization of nitrogen in their tissue and the subsequent release upon mortality, enchytraeids provided a large pulse of inorganic nitrogen in the sandy clay loam soil. In the loamy sand treatments where mortality was less, an increase in inorganic nitrogen due the activities of enchytraeids was also found at the end of the experiment. In this laboratory study enchytraeids significantly affected decomposition and nitrogen mineralization. High abundances of enchytraeids often correspond with the beginning of the growing season in Georgia; therefore, through enchytraeid activities, more nitrogen may be available for plant uptake. (C) 2003 Elsevier B.V. All rights reserved.

Seasonal measurements of soil microbial biomass, nematode trophic groups, net N-mineralization, net nitrification, net ammonification, litter decomposition, and soil respiration rates were examined to assess the effects of rhododendron ( Rhododendron maximum L.) removal and hurricane windthrow upon these factors. Comparisons of pre- and post-disturbance quantities of soil microbial biomass carbon ranged from 503 to 1080 μg C g soil −1 and microbial biomass nitrogen ranged from 67 to 169 μg total persulfate nitrogen g soil −1 , showing no significant differences or trends in response to these disturbance events. Total nematode abundance ranged from 13.05 to 54.31 nematodes g soil −1 and showed no significant differences in response to these disturbance events, although overall nematode abundance was declining in the disturbed plots at the end of the study. Nematode trophic structure was fairly consistent across both sites and all sampling dates and exhibited no discernible trends in response to these disturbance events. Rates of net N-mineralization, nitrification, and ammonification exhibited greater variability, post-disturbance. Litter decomposition rates and soil respiration rates decreased following the disturbance events, with respiration rates in the Cut plot being significantly higher across years. Overall, the effects of these disturbance events upon soil properties were highly variable and were unrelated to the major increases in N loss that were detected from deeper soil horizons following the hurricane windthrow event.

The boundaries between terrestrial and aquatic ecosystems, known as critical transition zones (CTZ), are dynamic interfaces for fluxes of water, sediment, solutes, and gases. Moreover, they often support unique or diverse biotas. Soils, especially those of riparian zones, have not been recognized as CTZ even though they play a critical role in regulating the hydrologic pathways of infiltration and leaching, or runoff and erosion, which can cumulatively affect biogeochemical processes and human livelihoods at landscape scales. In this review, we show how the processes that regulate hydrologic fluxes across and through soil CTZ are influenced by the activities of soil biota. Our message is fourfold. First, there are a variety of ways in which soil biodiversity, in terms of richness and dominance, can influence hydrological pathways in soil and thus the transfer of materials from terrestrial to aquatic ecosystems. Second, the influence of soil organisms on these hydrological pathways is very much interlinked with other environmental, soil biophysical, and vegetation factors that operate at different spatial and temporal scales. Third, we propose that the influence of soil biodiversity on hydrological pathways is most apparent (or identifiable), relative to other factors, in situations that lead to the dominance of certain organisms, such as larger fauna. Fourth, soils are buffered against environmental change by biophysical properties that have developed over long periods of time. Therefore, the effects of changes in soil biodiversity on hydrological processes at the ecosystem scale might be delayed and become most apparent in the long term.

Placement of plant residues in conventional tillage (CT) and no-tillage (NT) soils affects organic matter accumulation and the organization of the associated soil food webs. Root-derived C inputs can be considerable and may also influence soil organic matter dynamics and soil food web organization. In order to differentiate and quantify C contributions from either roots or litter in CT and NT soils, a 14 C tracer method was used. To follow root-derived C, maize plants growing in the field were 14 C pulse-labeled, while the plant litter in those plots remained unlabeled. The 14 C was measured in NT and CT soils for the different C pools (shoots, roots, soil, soil respiration, microbial biomass). Litter-derived C was followed by applying 14 C labeled maize litter to plots which had previously grown unlabeled maize plants. The 14 C pools measured for the litter-derived CT and NT plots included organic matter, microbial biomass, soil respiration, and soil organic C. Of the applied label in the root-derived C plots, 35‐55, 6‐8, 3, 1.6, and 0.4‐2.4% was recovered in the shoots, roots, soil, cumulative soil respiration, and microbial biomass, respectively. The 14 C recovered in these pools did not differ between CT and NT treatments, supporting the hypothesis that the rhizosphere microbial biomass in NT and CT may be similar in utilization of root-derived C. Root exudates were estimated to be 8‐13% of the applied label. In litter-derived C plots, the percentage of applied label recovered in the particulate organic matter (3.2‐82%), microbial biomass (4‐6%), or cumulative soil respiration (12.5‐14.7%) was the same for CT and NT soils. But the percentage of 14 C recovered in CT soil organic C (18‐69%) was higher than that in NT (12‐43%), suggesting that particulate organic matter (POM) leaching and decomposition occurred at a higher rate in CT than in NT. Results indicate faster turnover of litter-derived C in the CT plots. q 2001 Elsevier Science Ltd. All rights reserved.

The lower montane zone of northwestern Ecuador, like many parts of the tropics, is undergoing rapid conversion from native forest vegetation to crop and pastureland. The current landscape is a mosaic of agricultural land, forest fragments and second-growth vegetation in various stages of development. While there is abundant research documenting the effects of land-use change in the lowland tropics, such information is scarce for montane regions on young volcanic soils. We compared foxtail pasture (Setaria sphacelata, [(Schumach.) Stapf and C.E. Hubb.]) and traditional, mixed-species pasture with undisturbed old-growth forest, 15–20 y-old secondary forest and 5–10 y-old shrubby regrowth. At two replicates of each vegetation class, we measured soil nitrogen and carbon pools, in situ net nitrogen mineralization and nitrification, soil respiration and soil physical properties. Setaria pasture decreased soil NO−3-N pools and net mineralization and nitrification rates compared to mature forest, secondary vegetation, and mixed-species pasture. Soil NO−3-N in Setaria pastures, during wet and dry seasons, was 40 and 25% of amounts measured in other vegetation types. Net nitrification rates were also lower beneath Setaria during both seasons, the greatest difference occurring during the wet season. Net nitrification rates increased considerably (two-fold and greater) under wet season conditions beneath all vegetation types except Setaria pasture. Soils beneath both pasture types were wetter and had higher bulk density than mature and second-growth forests. Conversion to pasture produces widely varying effects on soil N dynamics depending on characteristics of the pasture species, such as Setaria’s extremely dense root system. Reduced soil N availability beneath Setaria pasture will affect both long-term pasture productivity and subsequent forest regeneration in abandoned pastures.

We conducted field studies of the effects of earthworms on microbial biomass-N in sandy clay loam vs. sandy soils under no-tillage management on Ultisols of the southern Appalachian Piedmont in Georgia, USA. 15 N -labeled crop residue was applied to the surface of plots with or without the addition of earthworms (principally Lumbricus rubellus and Aporrectodea caliginosa). Microbial biomass N and 15 N levels were measured at intervals over five years. Microbial N concentrations increased in both soils but more so at the surface of the sandy soil and in deeper soil layers in the clay soil. Microbial N concentrations were consistently lower in earthworm treatments than in controls in the clay soil and to a lesser extent in the sandy soil. In deeper layers of the clay soil, earthworm additions increased 15 N enrichment of the microbial pool, suggesting that earthworms increased transport of crop residue N into the subsoil. In the sandy soil the microbial pool was half as large as in the clay soil, but showed a 100–300% increase in 15 N enrichment during the first year, indicating substantially higher microbial turnover. Although earthworm activity reduced standing stocks of microbial biomass, particularly in the fine-textured soil, it appeared to increase the turnover of the microbial-N pool as indicated by 15 N measurements. Observed changes in microbial biomass reflected rapid cycling of labile organic matter pools in response to biological activity, soil texture and soil management.

Carbon storage in agricultural and forest soils has attracted attention recently due to its potential as a substantial carbon sink. Labile soil C pools are especially important because they are more vulnerable to climatic change and disturbance and play vital roles in nutrient cycling. Southern Appalachian forest soils and those from conventional tillage (CT), no-tillage (NT) and fescue sods at three sites in the Georgia piedmont were analyzed for total C, total N, carbohydrates, and microbial biomass C. The sizes of soil labile C pools (carbohydrates and microbial biomass) and their contributions to the total soil C pool differed significantly among ecosystems. The highest carbohydrate contents and microbial biomass C were found in forest soils, but agricultural soils had a significantly higher proportion of the soil organic matter present as carbohydrates and as microbial biomass. This difference probably reflects the quality of soil organic matter. Soil microbial biomass C was more sensitive to changes in management regimes than soil carbohydrates. Management practices signfiicantly affected organic C, carbohydrate contents, microbial biomass C and organic C turnover rates in agricultural soils, whereas differences in the quality of organic input due to different vegetation types substantially influenced soil labile C pools in forest soils. High mannose-to-xylose ratios in highly sandy agricultural soils indicate that plant-derived materials are rapidly metabolized by microorganisms and that organic C protection in sandy soils is largely dependent on reducing microbial access through effective residue management such as surface placement.

Organic matter and abiotic conditions seem to influence distribution patterns of Enchytraeidae. In this study effects of changes in management practices on population dynamics of enchytraeids were determined. At two sites (in Athens and Griffin, GA) parts of a fescue (FE) field were converted into conventional tillage (CT) and no-tillage (NT) plots and changes in densities and depth distribution of enchytraeids were followed for 3 years. A site at Watkinsville, containing various soil textures and characterised by very low organic carbon content, which was converted into no-tillage 4 years earlier, was also sampled. Significant reductions in enchytraeid densities, after conversion of fescue into CT, were only found at Griffin. The management practices affected the vertical distribution of enchytraeids. In fescue and NT more enchytraeids were found in the 0–5cm than in the 5–15cm layer. In conventional tillage fields enchytraeids were more evenly distributed over the profile or more abundant in the 5–15cm layer. Management also affected the timing of population dynamics in the different plots. At two sample dates high abundances were found in CT plots only, not in any of the other plots. Enchytraeids were larger at Athens than at Griffin and Watkinsville and contained more soil particles in their gut. At Athens enchytraeids will presumably contribute more to the development of soil structure than at the other sites. We conclude that management affects vertical enchytraeid distributions in soil and changes the timing of population dynamics.

In this article a brief overview of the World Wide Web (WWW) is given, with some examples of the kind of information and services pertaining to analytical chemistry that can be found there. An existing WWW site that has been set up for analytical chemists is used as a case in point. The article concludes with a brief look at some of the issues raised by publishing on the Internet.

Plant roots, fungi and soil fauna are important soil ecological constituents, which have substantial influences on soil C dynamics and nutrient cycling. Four biotic treatments (root exclusion, earthworm addition, fungicide and insecticide applications) were designed to investigate the influences of plant roots, fungi, microarthropods and earthworms on soil C dynamics and nutrient cycling in the field. Soils under these four treatments and their untreated controls in a 40 year old mixed meadow in the Georgia piedmont were analyzed for total organic C, soil N, microbial biomass C and N, and carbohydrates for 2 years. Root exclusion significantly reduced the concentrations of soil carbohydrates (P < 0.05) as determined by gas chromatography, with only slight differences in total C between the treatments and the controls. Microbial biomass C and N were significantly lower under root exclusion and fungicide treatment than under the control. Root exclusion and inhibition of soil fungi significantly reduced soil N content, suggesting that both roots and fungi contribute to the retention of soil organic N or contribute as a source of N in cultivated soils. Microbial biomass determined in this study was strongly related to total carbohydrates (P ⪡ 0.01). Mannose, a sugar mainly of microbial origin, significantly decreased in the surface 5 cm soils under fungicide treatment, while little effects of the arthropod repellant naphthalene were found in any of the measurements. Significant reductions in xylose and glucose but not in mannose after earthworm additions suggested that earthworms accelerated the turnover of plant materials in soils. The results confirmed that the short-term effects of soil biota on SOM dynamics are more profound on soil carbohydrates and microbial biomass than on total C. High mannose-to-xylose ratio indicates that the microbial-derived carbohydrates are relatively dominant in the total carbohydrate pool. When combined with information on microbial biomass, soil carbohydrate ratios may be a useful indicator of changes in SOM status as a function of biotic and management regimes in cultivated soils.

Differences in soil organic carbon, nitrogen and carbohydrates as a result of different tillage practices under continuous cropping were studied in a 12 year old sorghum/rye rotation experiment in the Georgia piedmont. Soil organic C and N concentrations in an aggrading agroecosystem (no-tillage, NT) were significantly higher than in a degrading agroecosystem (conventional tillage, CT) at all dates. Soil carbohydrates followed a pattern similar to total organic C. Carbohydrate concentrations in macroaggregates (>250 μm) from NT surface soils were significantly higher than in microaggregates ( 2000 μm aggregates contained the lowest total organic C concentration. A significantly higher mannose to xylose ratio in microaggregates than in macroaggregates suggested that organic matter (OM) in microaggregates was strongly metabolized by soil microorganisms, but OM in macroaggregates was much less processed. The inhibition of fungi by the fungicide captan significantly reduced the concentrations of soil C and acid-hydrolyzable carbohydrates in NT soils but not in CT soils, indicating that fungi play a more significant role in organic C retention in the NT system than in the CT system.

Tunneling and burrowing activities of soil organisms affect structure and porosity of soils, but the role of enchytraeids as a soil burrowing organism is unclear. This study was initiated to evaluate the effect of enchytraeids on soil porosity in two soils with different texture and similar, low organic matter contents. In small microcosms, the burrowing activities of Enchytraeus minutus were followed during a 51 day period. The microcosms consisted of two glass plates with a bottom of plaster of Paris and sides of Plexiglas. Sieved (

Perspectives from different but complementary schools of thought in ecology are being applied to sustainable agriculture-population and community ecology on one hand and ecosystem ecology on the other. These perspectives intersect in the study of mechanisms and controls of processes in ecosystems. Increased understanding of these processes in agroecosystems will contribute to development of sustainable agriculture. Current models of nutrient cycling in soil suggest that active or readily mineralizable fractions of soil organic matter (SOM) are coupled to plant-available nutrient pools through the processes of mineralization and immobilization. Factors that control these processes (soil temperature, water, and texture; and resource quality of organic inputs) are influenced by management practices and represent potential controlling points for managing nutrient cycles in agroecosystems. Organic inputs present different problems for nutrient management than & synthetic fertilizers, because most nutrients mus...

The optimum temperatures for population development were determined for six species of bacterial-feeding nematodes from among eight temperatures, ranging from 5 to 40 C. Four of the species are cohabiting species. The range of temperatures over which population development occurs (temperature niche breadth) is different for the cohabiting species. This difference may be a means of reducing competition between species, thus increasing temperatures over which habitats can be exploited.

Since species loss is predicted to be nonrandom, it is important to understand the manner in which those species that we anticipate losing interact with other species to affect ecosystem function. We tested whether litter species diversity, measured as richness and composition, affects breakdown dynamics in a detritus-based stream. Using full-factorial analyses of single- and mixed-species leaf packs (15 possible combinations of four dominant litter species; red maple (Acer rubrum), tulip poplar (Liriodendron tulipifera), chestnut oak (Quercus prinus), and rhododendron (Rhododendron maximum)), we tested for single-species presence/absence (additive) or species interaction (nonadditive) effects on leaf pack breakdown rates, changes in litter chemistry, and microbial and macroinvertebrate biomass. Overall, we found significant nonadditive effects of litter species diversity on leaf pack breakdown rates, which were explained both by richness and composition. Leaf packs containing higher litter species richness had faster breakdown rates, and antagonistic effects of litter species composition were observed when any two or three of the four litter species were mixed. Less-consistent results were obtained with respect to changes in litter chemistry and microbial and macroinvertebrate biomass. Our results suggest that loss of litter species diversity will decrease species interactions involved in regulating ecosystem function. To that end, loss of species such as eastern hemlock (Tsuga canadensis) accompanied by predicted changes in riparian tree species composition in the southeastern United States could have nonadditive effects on litter breakdown at the landscape scale.

A method of generating nucleic acid probes by polymerase chain reaction (PCR) for the detection of Epstein-Barr virus (EBV)-DNA by in situ hybridization in oral hairy leukoplakia (OHL) lesions is described. This method has the advantage over older methods of being cheaper, quicker and retaining sensitivity and specificity. Purified PCR products of Epstein-Barr virus DNA of 110 bp and 328 bp were labelled with biotin by nick translation or random primer labelling and were compared in in situ hybridization experiments with probes prepared by incorporation of biotin-labelled nucleotides in the PCR reaction mixture, with EBV viral DNA as a template. These probes were applied to 18 OHL tongue biopsies known to be positive for EBV-DNA, using a commercially available biotin-labelled BamHI "V" fragment EBV-DNA probe. To determine the specificity of the probes, we applied them to 20 normal tongue tissue samples and to 12 biopsies taken from keratotic tongue lesions from patients without risk factors for HIV infection and known to be negative for EBV-DNA. Clear positive signals for EBV-DNA were detected in all 18 cases of OHL biopsies using the amplimer of 328 bp labelled by PCR and random primer labelling. However, nick translation labelling was less efficient and sensitive. All control specimens were negative for EBV-DNA.

The identification of the novel candidal species, C. dubliniensis, from oral swab studies of HIV-seropositive and -seronegative individuals has led to speculation that such a species may also reside in the oral cavity of other patient groups. In this study involvement of the newly described species, C. dubliniensis, was investigated in oral carriage and disease in 414 insulin-using diabetes mellitus patients. Seventy-seven percent of the diabetic patients carried candidal species in the oral cavity. C. albicans was the most commonly identified candidal species. This was followed by C. dubliniensis, which was isolated on 64 occasions. Colonisation with multiple candidal species was common, and C. dubliniensis was present in both carriage and disease states. Seven patients without signs of oral disease had C. dubliniensis isolated as the sole candidal species, while the same species was associated with various forms of oral candidosis in six patients.

The significance of biodiversity to biogeochemical cycling is viewed most directly through the specific biogeochemical transformations that organisms perform. Although functional diversity in soils can be great, it is exceeded to a high degree by the richness of soil species. It is generally inferred from this richness that soil systems have a high level of functional redundancy. As such, indices of species richness probably contribute little to understanding the functioning of soil ecosystems. Another approach stresses the value of identifying “keystone” organisms, that is those that play an exceptionally important role in determining the structure and function of ecosystems. Both views tend to ignore the importance of biodiversity in maintaining the numerous and complex interactions among organisms in soils and their contributions to biogeochemical cycling. We describe some of those interactions and their importance to ecosystem function.

Population dynamics of enchytraeids are described for 2 montane forested watersheds in southwestern North Carolina (Coweeta) and an agricultural site under conventional (CT) and no-tillage (NT) management in the northeastern Georgia piedmont (Horseshoe Bend, HSB). Given that much of the taxonomy, ecology and community structure of enchytraeids is poorly known, our objective was to identify key “indicators” of enchytraeid community structure which could be used, in this case, to better understand their role in soil structure formation. Although population densities of enchytraeids were higher in the forested (Coweeta) than in the arable soils (HSB), the average ash free dry weight per enchytraeid at HSB was nearly double that found at Coweeta. Based on these measurements and an estimate of their gut transit time, we calculated that the enchytraeids at HSB transported 2180 g of soil per m2 per year compared to 443 and 393 g m-2 yr-1 for watershed 18 and 27, respectively at Coweeta. We therefore hypothesize that enchytraeids have a larger influence on soil structure in agricultural fields than in forested areas, in spite of lower population densities. The ash free dry weight and ash wt. per enchytraeid may qualify as key “indicator” parameters of enchytraeid community structure which helps to understand their functional role in ecosystems, though more studies are called for.