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The concept of the gender wage gap has received considerable attention in the literature, particularly in the U.S. context. Many analyses put forth various factors that explain the variation in wages across genders. However, we extend this knowledge to link the gender wage gap with the theoretical framework of intersectionality. Specifically, the current analysis focuses on the intersection between gender, race, and region to explain the variation in gender wage gap across the United States. Through difference in means tests as well as linear regression, we show that region has an independent effect on explaining the gap in pay between men and women. We employ data from the National Women's Law Center that quantifies the wage gap for each state for various racial groups. By employing this type of data, it allows us to move beyond the existence of the wage gap and analyze the effect of region as well as offer a test of the intersectionality argument. Findings show that region does play a role in the wage gap, even when accounting for economic and demographic characteristics of the state. [ABSTRACT FROM AUTHOR]

This work investigated the responses of antibiotic resistance genes (ARGs) and the soil microbial community in a paddy–upland rotation system to mineral fertilizer (NPK) and different application dosages of manure combined with NPK. The occurrence of five tetracycline ARGs ( tetA , tetB , tetC , tetG and tetW ), two sulfonamide ARGs ( sul1 and sul2 ) and one genetic element ( IntI 1) was quantified. NPK application showed only slight or no impact on soil ARGs abundances compared with the control without fertilizer. Soil ARGs abundances could be increased by manure-NPK application but was related to manure dosage (2250–9000 kg ha −1 ). Principal component analysis (PCA) showed that the soil ARG profile of the treatment with 9000 kg ha −1 manure separated clearly from the other treatments; the ARGs that contributed most to the discrimination of this treatment were tetA , tetG , tetW , sul1 , sul2 and IntI 1. Community level physiological profile (CLPP) analysis showed that increasing manure dosage from 4500 kg ha −1 to 9000 kg ha −1 induced a sharp increase in almost all of the detected ARGs but would not change the microbial community at large. However, 9000 kg ha −1 manure application produced a decline in soil microbial activity. Determination of antibiotics and heavy metals in soils suggested that the observed bloom of soil ARGs might associate closely with the accumulation of copper and zinc in soil. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The best method to teach anatomy is widely debated. A shift away from cadaveric dissection in UK medical schools towards newer approaches has taken place without adequate evaluation of their suitability. The impact of this on future anatomical and surgical competencies is unclear. We assessed student perceptions to different methods of anatomy teaching. Methods: All 2nd year students at Leeds School of Medicine were invited to complete a matrix-grid questionnaire. Participants were asked to score six methods of anatomy teaching (dissection; prosection; lectures; models; PC software packages; living & radiological anatomy) using a 5-point Likert-type scale on the ability to achieve nine learning objectives. Kruskal–Wallis and Mann–Whitney analyses suitable for non-parametric data were used to evaluate differences in scores between teaching methods. Results: 170 students (71%) responded to the survey. Overall, dissection was the single highest scored method, followed by prosection. Newer approaches such as models, computer software packages and living & radiological anatomy scored comparatively worse. The most suitable method for achieving individual learning objectives was variable with dissection perceived as most suitable for four out of nine objectives. Conclusions: Cadaveric dissection is a favourable approach for achieving important learning objectives in the field of anatomy. Further evaluation of teaching methods is required prior to changes being made in the curricula of UK medical schools. [Copyright &y& Elsevier]

The universally conserved His-66 of elongation factor Tu (EFTu) stacks on the side chain of the esterified Phe of PhetRNAPhe. The affinities of eight aminoacyl-tRNAs were differentially destabilized by the introduction of the H66A mutation into Escherichia coli EF-Tu, whereas Ala-tRNAAla and GlytRNAGly were unaffected. The H66F and H66W proteins each show a different pattern of binding of 10 different aminoacyltRNAs, clearly showing that this position is critical in establishing the specificity of EF-Tu for different esterified amino acids. However, the H66A mutation does not greatly affect the ability of the ternary complex to bind ribosomes, hydrolyze GTP, or form dipeptide, suggesting that this residue does not directly participate in ribosomal decoding. Selective mutation of His-66 may improve the ability of certain unnatural amino acids to be incorporated by the ribosome. [ABSTRACT FROM AUTHOR]

Abstract: Vegetational changes during the restoration of cutover peatlands leave a legacy in terms of the organic matter quality of the newly formed peat. Current efforts to restore peatlands at a large scale therefore require low cost and high throughput techniques to monitor the evolution of organic matter. In this study, we assessed the merits of using Fourier transform infrared (FTIR) spectra to predict the organic matter composition in peat samples at various stages of peatland regeneration from five European countries. Using predictive partial least squares (PLS) analyses, we were able to reconstruct peat C:N ratio and carbohydrate signatures with reasonable accuracy, but not the micromorphological composition of vegetation remains. Despite utilising different size fractions, both carbohydrate (<200μm fraction) and FTIR (bulk soil) analyses report on the composition of plant cell wall constituents in the peat and therefore essentially reveal the composition of the parent vegetational material. The accuracy of the FTIR-based PLS models for C:N ratios and carbohydrate signatures was adequate to allow for their use as initial screening tools in the evaluation of the present and future organic matter composition of peat during monitoring of restoration efforts. [Copyright &y& Elsevier]

Abstract: L-ficolin is a pattern-recognition molecule which binds lipoteichoic acid and Gram-positive bacteria and activates the lectin pathway of complement. Five common functional polymorphisms have recently been identified in the FCN2 gene which encodes L-ficolin: three promoter polymorphisms (at positions −986, −602 and −4) which affect serum L-ficolin concentration, and two non-synonymous polymorphisms (Thr236Met and Ala258Ser) which influence carbohydrate binding. We studied the frequencies of these polymorphisms in individuals with invasive pneumococcal disease (IPD) and a control group. Although the five FCN2 polymorphisms were each present in the UK Caucasian population studied, no significant associations were observed between the FCN2 polymorphisms and susceptibility to IPD. This is in contrast to mannose-binding lectin deficiency, which we have previously shown to be associated with increased susceptibility to IPD. Although we are unable to exclude small effects of FCN2 genetic variation on susceptibility to IPD, the result suggests that L-ficolin may not be critical for host defence against pneumococcal infection. [Copyright &y& Elsevier]

Abstract: Acid rain sulphate (SO4 2−) deposition is a known suppressant of methane (CH4) emission from wetlands. However, the hypothesised mechanism responsible for this important biogeochemical interaction, competitive exclusion of methanogens by dissimilatory SO4 2− reducing bacteria (SRB), lacks supporting evidence. Here, we present data from an acid rain simulation experiment in the Moidach More peat bog of NE Scotland that strengthens this hypothesis. We report a tenfold increase in estimated SO4 2− reduction during periods when measured CH4 emission rates were suppressed relative to controls receiving only one-tenth the SO4 2− of treated plots, but no treatment effect on potential methane oxidation. This tenfold increase in estimated SO4 2− reduction indicates the presence of a more active population of SRB in plots where CH4 emissions were reduced by over 30%. [Copyright &y& Elsevier]

Abstract: A multiple substrate induced respiration (SIR) assay, using 14C-labelled carbon sources, was used to evaluate community level physiological profiles (CLPP) of the microbial community in peat horizons of differing degrees of humification. The separation and grouping of the peat horizons by CLPP was similar to the pattern produced by analysis of the organic carbon chemistry of the peat horizons by Fourier Transform Infrared (FTIR) spectroscopy and therefore reflected the level of decomposition. Partial redundancy analysis showed that a large proportion (68.7%) of the variability in the CLPP data could be attributed to the ratio of polysaccharide to ‘carboxylate’ FTIR bands alone. The multiple substrate SIR technique may, therefore, be a powerful technique to further elucidate the influence of the microbial constituent of peat on the potential activity and patterns of cycling of labile carbon in peatlands. [Copyright &y& Elsevier]

Abstract: A miniaturized method based on 96-well microtitre plates was developed and used to study respiration in pristine and contaminated soils following addition of volatile substrates. Small soil samples were exposed to fuel components, which were volatilized from spatially separate reservoirs of 2,2,4,4,6,8,8-heptamethylnonane (HMN) as an organic carrier. Respiration was determined as CO2 production by means of a pH-indicator and bicarbonate-containing agar, or as 14CO2 evolution from 14C-labelled substrates. Substrate concentrations inducing maximum microbial activity or inhibition were determined and CO2 production profiles examined by multivariate analysis. When high concentrations of fuel components were applied, distinction of hydrocarbon exposed soils from unexposed soil was achieved within 6h of incubation. With low concentrations, adequate distinction was achieved after 24h, probably as a result of community adaptation. Nutrient limitation was identified with the 14C method for toluene, and the optimal N and P amendment determined. Further potential applications of this rapid and inexpensive method are outlined. [Copyright &y& Elsevier]

A highly differentiated porcine skin organ culture model has been developed for future investigations of membrane-coating granules (MCG) and their role in epidermal differentiation. In contrast to many previous systems, cultures do not undergo necrosis of the upper epidermis or display dermoepidermal separation, but survive for at least 3 weeks, at which time mitotic cells are still evident. Although rete projections are gradually smoothed out and the viable epidermis thins at a rate of approximately 0.35 cells per day, the stratum corneum gains approximately 1.5 corneocytes per day. Furthermore, at 3 weeks all the major differentiation markers are expressed, including keratohyalin granules, MCG, and an orthokeratotic stratum corneum. The system is inexpensive, simple to establish, and does not require elevated oxygen levels. The main requirements are 1) the use of Dulbecco's minimal essential medium supplemented with 2) hydrocortisone (100 μg/ml), 3) growth at an air/liquid interface, and 4) attached connective tissue. The further addition of vitamin C (300 μg/ml) and/or bovine serum albumin (2 mg/ml) offered no obvious advantage. Degeneration of organ cultures in standard cell culture media was discovered to be caused by fetal bovine serum (FBS). FBS-induced degeneration was not prevented by adding any of the supplements rested, or the inclusion of 3T3 fibroblasts, even when culturing at an air/liquid interface. Complete submersion rapidly killed specimens, presumably through oxygen starvation. The ability to maintain a fully keratinizing system for several weeks, in a totally chemically defined medium, will prove valuable for research not only into the role(s) of MCG in epidermal biology but also studies of desquamation and epidermal differentiation. [ABSTRACT FROM AUTHOR]

Lysosomes are by definition organelles that maintain an internal acidic pH and contain hydrolytic enzymes. Membrane-coating granules contain a battery of hydrolytic enzymes, in addition to their lamellar discs, and are therefore commonly assumed to he lamellate lysosomes. Although there are data confirming the existence of enzymes in membrane-coating granules, there is no direct evidence to suggest that their internal pH is acidic. As part of a wider program on their role in desquamation, our aim was to determine whether membrane-coating granules are indeed acidic and possess proton pumps. Chloroquine and monensin were selected as the pH markers because both induce swelling of acidic organelles. In four repeat experiments dermatome slices of pig ear skin (2 mm2 × 0.5 mm) were incubated as organ cultures either alone (control) or with 1 mM chloroquine or 25 μM monensin. Ultrastructural observations revealed no swelling in control specimens. In contrast, the inclusion of chloroquine or monensin caused swelling of specific organelles including membrane-coating granules, lysosomes, and trans elements of Golgi stacks, but not mitochondria, rough endoplasmic reticulum, or nuclear envelopes. Swelling of membrane- coating granules and the other organelles was prevented by pretreatment with N,N'-dicyciohexylcarbodiimide, a known inhibitor of lysosomal H+ ATPase activity. These findings suggest that membrane-coating granules actively maintain an acidic interior with the aid of proton pumps. Furthermore, membrane-coating granules are heterogeneous because swelling of the whole population did not commence simultaneously. However, it remains to be determined whether this heterogeneity reflects variations in membrane-coating granule pH, leakiness of their membranes to cations, or the number or activity of their proton pumps. [ABSTRACT FROM AUTHOR]

The conversion of natural forests to tea plantations largely affects soil nitrous oxide (N 2 O) emissions and soil microbial communities. However, the impacts of this conversion on the contribution of fungi to N 2 O emission and on fungal community structure remain unclear. In this study, we determined the soil N 2 O emission rate, N 2 O production by fungi, associated fungal community diversity, and related ecological factors in chronological changes of tea crop systems (3, 36 and 105 years old tea orchards named T3, T36 and T105, respectively), and in an adjacent soil from a natural forest. The results indicate that the tea plantations significantly enhanced soil N 2 O production compared with the forest soil. Tea plantations significantly decreased soil pH and C/N ratio, but increased soil inorganic nitrogen (N). Furthermore, they increased the fungal contribution to the production of soil N 2 O, but decreased the bacterial counterpart. We also observed that fungal community and functional composition differed distinctly between tea plantations and forest. Additionally, most of the fungal groups in high N 2 O emission soils (T36 and T105) were identified as the genus Fusarium , which were positively correlated with soil N 2 O emissions. The variation in N 2 O emission response could be well explained by NO 3 −-N, soil organic carbon (SOC), C/N, and Fusarium , which contributed to up to 97% of the observed variance. Altogether, these findings provide significant direct evidence that the increase of soil N 2 O emissions and fungal communities be attributed to the conversion of natural forest to tea plantations. Image 1 • Forest-to-tea plantation conversion altered sources of N 2 O production. • Tea plantations have increased N 2 O production source from fungi. • Fungal communities differed following the conversion from forest to tea plantation. • Soil properties and Fusarium groups contributed to N 2 O emissions. [ABSTRACT FROM AUTHOR]

Organic fertilizers increase soil fertility, microbial diversity and heterogeneity of microbial activity hotspots. Black soldier fly (Hermetia illucens L.) frass (BSFF) derived from organic waste composts has been extensively marketed as organic fertilizer, but its effects on rhizosphere microbiota remain unknown. We compared the effects of BSFF from three organic wastes (straw, manure, and kitchen waste) on maize growth in acidic soils. Sufficient P, an optimal soil pH, and a satisfactory soil C/N ratio, as provided by the straw-derived frass, increased the maize growth more than the other frass types. Maize growth increased due to nutrient mobilization by active rhizosphere microbiota, which was localized using in situ soil zymography and identified through DNA amplicon sequencing and quantitative PCR. Specifically, the area of hotspots of acid phosphatase activity along the maize roots increased for 2.8 times after straw-derived frass application compared to unamended soils. Microbial diversity raised within these enzyme activity hotspots and was accompanied by the increased abundances of plant growth-promoting microbial taxa like Luteibacter , Chrysosporium , and Cladorrhinum. Microorganisms formed efficient and mutualistic networks within the rhizosphere hotspots induced by straw-derived frass to accelerate organic P mineralization, as inferred by random forest analysis and the quantitative of phoC and phoD genes. Concluding, the straw-derived frass benefits maize growth on acidic soils through abiotic (soil physico-chemical properties) and biotic (active rhizosphere microbiota) stimuli. • Rhizosphere microbiota was sampled from enzyme activity hotspots localized by zymography. • Indicator species in rhizosphere hotspots were depended on added frass from organic wastes. • Straw-derived frass intensified hotspots of phosphatase and leucine aminopeptidase activities. • Abundance of active microbes harboring phoC gene increased in enzyme hotspots. • Microbial network in soil with straw-derived frass has greater complexity compared to other fertilizers. [ABSTRACT FROM AUTHOR]

Nitrification, as a crucial step in nitrogen cycling and plant nutrition, is a biologically mediated process responsible for enormous losses of nitrogen fertilizer and a contributor to environmental pollution. The recent progress in our understanding of nitrification and nitrifiers, specifically in acidic soils, is discussed and reviewed. At one time it was assumed that rates of nitrification are relatively low in acidic soils. However, more recent studies have demonstrated nitrification down to pH 3.0 and that the rate of nitrification can equal, or even exceed, that found in neutral soils. Studies on acidic forest soils in Europe noted that they have a high potential for nitrate production. Furthermore, using the 15 N isotope-dilution technique it was shown that net nitrification measurements can markedly underestimate gross nitrification in these natural and highly organic systems. Using selective inhibitors it has been demonstrated that heterotrophic nitrifiers can contribute to nitrification. While heterotrophic nitrification can be performed by a wide range of bacteria and fungi, inhibitor studies point to fungi to be mainly responsible. Autotrophic ammonia-oxidizing bacteria (AOB), such as Nitrosomonas and Nitrosospira , have been known for some considerable time but have generally found to be inactive in acidic conditions. The discovery of ammonia monooxygenase in uncultured archaea that were functionally active at low pH pointed to an autotrophic microbial group (ammonia oxidizing archaea, AOA) that might be adapted to low substrate (ammonia) concentrations and responsible for nitrification in the wider range of acidic grassland and cultivated soils. Obligately acidophilic AOA have more recently been cultivated while stable isotope probing has been used to confirm the dominance of AOA over AOB in acidic soils. Detailed molecular studies using both 16S rRNA and amo A (ammonia monooxygenase sub-unit A) gene sequencing are continuing to expand our appreciation of the diversity of both AOB and AOA and how this varies over different pH ranges and in different ecosystems. Similar work is being directed towards nitrite oxidizing bacteria (NOB) but to date we do not fully know the role of pH in controlling NOB activity. Such understanding of nitrification and nitrifiers will help develop new effective nitrification inhibitors and aid the management of nitrogen cycling in acidic soils. [ABSTRACT FROM AUTHOR]

Abstract: Because of their rapidly changing vegetation dynamics and harsh environmental conditions, roadside prairies in semi-arid regions represent an exceptional study system in which to investigate the effects of plant-soil interactions on ecosystem functioning. We conducted a two-year field experiment on two roadside embankments in semi-arid central Spain differing in construction age to answer the following questions: (i) do commonly used restoration treatments (hydroseeding, fertilization and irrigation) affect soil microbial functional diversity and processes related to soil functioning (basal respiration, total N and P and in situ N availability rate)? (ii) what portion of plant effects on processes related to soil functioning is mediated indirectly by microbial functional diversity? Except for a small and negative irrigation effect on the microbial functional diversity in the three-year old site, the restoration treatments employed did not affect this variable. Fertilization increased plant diversity, an effect likely mediated by the enhanced soil nutrient availability with this treatment at early stages of secondary succession. In contrast, hydroseeding did not affect processes related to soil functioning. The total effect of the plant community on these processes was higher than that of the microbial functional diversity alone, suggesting that the studied slopes are to the greater extent regulated by plants. However, soil microbes are a key proximate influence in the system, as the indirect effects of plant community on soil functioning processes mediated by soil microbes represented 37–41% of the total plant effects observed. Our results indicate that the restoration of recently built slopes can potentially be improved with treatments that promote plant compositional shifts, such as fertilization, or alter soil function, such as the enhancement of soil microbial functional diversity. They also highlight that plant-soil interactions are an important process that can be manipulated for restoration purposes in early-successional stages, especially in nutrient-poor semi-arid ecosystems. [Copyright &y& Elsevier]

Intensively fertilized acidic soils are global hotspots of nitrous oxide (N 2 O) emissions, contributing to net agronomic greenhouse gas outcomes. Identifying the key drivers of soil N 2 O emissions is hampered by the synergistic or antagonistic effects of multiple factors. Within a framework based on the predominant role of microbial communities producing N 2 O, the N 2 O emissions are affected either by proximal regulators: temporary soil property fluctuations affect N 2 O production transcriptionally, or by distal regulators: persistent genetic rearrangements in local microbial communities. The proximal regulators, individually or together, may spontaneously impact distal regulators. Here, we use acidic soils from tea (Camellia sinensis L.) plantations on a broader geographic scale as a model system. Based on amplicon sequencing and properties of 195 acidic (average pH = 5.0) soils, we determined the importance of proximal and distal regulation to N 2 O emissions. Microbial phylogenetic diversity as a distal regulator overwhelms mineral N content as a proximal regulator in explaining high N 2 O emissions. Low-abundance, diverse prokaryotic communities (e.g., Acidothermu) and specialized denitrifying fungal communities (e.g., Fusarium) were associated with high N 2 O emissions. Revisiting the impact of proximal regulators on distal regulators revealed that soil pH is the sole proximal regulator influencing the prokaryotic rare taxa that correlated with high N 2 O emissions. When considering proximal regulators together (here soil properties compiled as soil fertility index), the microbial diversity were independent of soil fertility. The microbial assembly was dominated by stochastic processes. Consequently, proximal regulators have a limited impact on distal regulators of N 2 O emissions from acidic soils. In conclusion, the framework underscored the importance of in situ microbial communities as distal regulators in explaining high N 2 O emissions from acidic soils. • Tea plantation soils as a model system for studying N 2 O emissions from acidic soils. • Microbial assembly processes are independent of soil fertility. • Microbial phylogenetic diversity explains more elevated N 2 O emissions. • Diverse prokaryotes and specialized fungi contributed to high N 2 O emissions. [ABSTRACT FROM AUTHOR]

The distribution and morphology of tonofilament (TF) clumps were examined by light and electron microscopy in skin samples from a total of 17 patients with the Dowling-Meara (DM) form of epidermolysis bullosa simplex (EBS). TF clumps extending from the basal to the upper-spinous epidermal layer were seen in all lesional skin samples and in the majority of peri-lesional and non-lesional skin samples. TF clumps were also noted in adnexal epithelia, including outer hair root sheaths, sweat ducts, and sebaceous glands. Cultured keratinocytes from two patients also demonstrated characteristics TF clumps. All these epithelial cells have in common their expression of the keratin pair K5 and K14. Post-embedding immunogold electron microscopy using antibodies to K5, K14, and K10 showed similar expressed keratins in DM-EBS skin from four patients compared with normal skin, with K5 and K14 predominantly in the basal cell layer and K10 in the suprabasal layers. The clumped TF in DM-EBS samples were labeled strongly with anti-K5 and K14 antibodies in the basal and suprabasal layers. In contrast, the suprabasal clumps were only slightly reactive with anti-K10 antibodies and labeling was usually restricted to the periphery of the clumps. We conclude that DM-EBS is associated with an intrinsic abnormality of the keratin-filament network involving the K5 and K14 pair that is likely to result in impaired resistance of basal epidermal cells to external shearing forces, leading to the characteristics interaepidermal blisters. DM-EBS may become the first genetic skin disease to be recognized as having a specific keratin abnormality. [ABSTRACT FROM AUTHOR]

• Oxytetracycline can be degraded effectively by black soldier fly larvae. • Intestinal microorganisms facilitate the bioremediation of antibiotic contamination. • This is the first report of ARGs and MGEs in the gut of black soldier fly larvae. As a saprophytic insect, the black soldier fly can digest organic waste efficiently in an environmentally friendly way. However, the ability and efficiency of this insect, and the microbial mechanisms involved, in the degradation of antibiotics are largely uncharacterized. To obtain further details during the degradation of OTC (oxytetracycline) by black soldier fly larvae (larvae), the changes in intestinal bacterial communities were examined. Both ARGs (antibiotic resistance genes) and MGEs (mobile genetic elements) were found within the larval guts. At the end of the degradation period, 82.7%, 77.6% and 69.3% of OTC was degraded by larvae when the initial concentrations were 100, 1000 and 2000 mg kg−1 (dry weight), respectively, which was much higher than the degradation efficiencies (19.3–22.2%) without larvae. There was no obvious effect of OTC on the development of the larvae. Although the larval gut microorganisms were affected by OTC, they adapted to the altered environment. Enterococcus , Ignatzschineria , Providencia , Morganella , Paenalcaligenes and Actinomyces in the gut responded strongly to antibiotic exposure. Interestingly, numerous ARGs (specifically, 180 ARGs and 10 MGEs) were discovered, and significantly correlated with those of both integron-integrase gene and transposases in the larval gut. Of all the detected ARGs, tetracycline resistance genes expressed at relatively high levels and accounted for up to 67% of the total ARGs. In particular, Enterococcus, Ignatzschineria, Bordetella, Providencia and Proteus were all hosts of enzymatic modification genes of tetracycline in the guts that enabled effective degradation of OTC. These findings demonstrate that OTC can be degraded effectively and prove that the bioremediation of antibiotic contamination is enhanced by larvae. In addition, the abundance of ARGs and MGEs formed should receive attention and be considered in environmental health risk assessment systems. [ABSTRACT FROM AUTHOR]

Phospholipid fatty acid (PLFA) analysis has been widely used to study soil microbial community structure. Soil PLFAs are taken to be indicative of living organisms since phospholipids are assumed to rapidly degrade after cell death. However, the turnover rate of phospholipids has never been accurately quantified. For this purpose, a short incubation experiment was conducted by amending paddy soil with extracted phospholipids, using the 13C labeling technique and PLFA analysis to quantify phospholipid degradation. Both bacterial (Methylocystis sp. and Escherichia coli) and fungal (Simplicillium subtropicum) phospholipids had high turnover rates. The half-life (t ½) for different phospholipids ranged from 14 to 27 h and the average t ½ for total phospholipids was about 20 h at 25 °C but nearly double that at 15 °C. However, phospholipids had a similar turnover rate in a soil with lower microbial biomass (84 mg C kg−1) compared to a soil with higher microbial biomass (305 mg C kg−1). Assimilation of 13C into other phospholipids was very low but followed the same timescale. Overall, this provides for the first time direct evidence for high turnover rates in soil through the analysis of specific 13C-labelled PLFAs and confirms the classic hypothesis that intact phospholipids represent living cells, necessary for the validity of the established PLFA methodology. Image 1 • Soil phospholipid degradation was accurately quantified using pure 13C labelled substrates. • High turnover rates of soil phospholipids were found and the average half-life was about 20 h. • The results confirm the classic hypothesis that intact phospholipids represent living cells in soil. [ABSTRACT FROM AUTHOR]

Abstract: Trees have a key role in determining the composition of soil biota via both above and belowground resource-based mechanisms, and by altering abiotic conditions. We conducted an outdoor mesocosm experiment to investigate the relative impact of above and belowground tree inputs on soil nematode trophic composition, and examine whether tree-driven impacts differed between contrasting species (birch and pine). For both species, we created a factorial design of litter addition and root presence treatments. The litter addition treatment was equivalent to natural levels of litterfall; tree saplings were planted in mesocosms for the root presence treatment and an unplanted control treatment was established that had no litter or root inputs. Litter addition had a limited impact on soil nematode community composition: it primarily decreased omnivore and predatory nematode abundance in birch but had few other effects on the nematode community. By contrast, root presence markedly altered nematode community composition through changes in a range of trophic groups. For both birch and pine, there were significant increases in total, fungivore and predatory nematode abundance in root presence treatments, and furthermore, total and fungivore abundances were positively related to root biomass. Root presence of these contrasting tree species also had a distinctive impact on some specific nematode trophic groups; pine roots promoted bacterivore abundance while birch roots promoted root-hair feeding nematode abundance. These findings suggest strong bottom-up effects of belowground tree inputs, and indicate that particular components of the nematode community may be affected differently by resource quantity and quality. Consequently, we suggest that, in the short-term, belowground rather than aboveground tree inputs have a strong impact on soil food web structure and complexity. [Copyright &y& Elsevier]

Abstract: To determine whether successional changes in plant communities may influence belowground community structure, we quantified nematode abundance, trophic structure and diversity along two separate chronosequences from heather moorland to birch woodland in the Scottish uplands. Tree invasion markedly altered plant community composition, and hence litter inputs, both directly, and indirectly through changes in understorey species. In turn, these changes in detrital inputs were reflected in consistent changes in nematode community structure. Nematode abundance increased from moorland to birch woodland, with moorland soils being dominated by a few taxa, notably root-hair and fungal feeders, compared to the more diverse composition of the birch woodland soils. Trophic structure was altered through an increase in the abundance of bacterial feeding relative to fungal-feeding nematodes, and an increase in the abundance of predatory nematodes. The increase in predators during the succession from moorland to woodland was associated with an increase in soil pH, highlighting that not only changes in the plant community, but also changes in soil properties associated with tree invasion may influence soil nematodes. Nematode diversity increased from moorland to birch woodland, with nematode richness being positively related to both plant species richness and soil pH. These results suggest that trees may control soil community structure through the manipulation of resources and the soil physico-chemical environment, promoting greater nematode diversity and trophic complexity. [Copyright &y& Elsevier]