Search

The application of biochar to land has been promoted as a strategy for sequestering carbon in soils, for improving soil fertility and remediating soil pollution. However, the implications of biochar amendments on mycorrhizal associations and pesticide decomposition in agricultural soils are poorly understood. In this study, we compared the effects of four treatments; control (no biochar and no arbuscular mycorrhizal fungi (AMF), biochar (biochar without AMF), AMF (AMF without biochar) and biochar + AMF (AMF and biochar) on the fate of simazine. We specifically focused on the sorption, leaching and biodegradation behaviour of simazine. Our results showed that when symbiosis existed between plants and AMF, biochar inhibited simazine decomposition and AMF inoculation alleviated this inhibition. In contrast, this alleviation was not observed when the plant was removed. In addition, AMF inoculated into the biochar amended soil significantly decreased simazine concentration in the leachate; however, in the AMF‐only treatment, no effect on simazine leaching was observed. These phenomena were attributed to variation in the soil's sorption capacity due to biochar application or AMF inoculation. Overall, biochar application combined with AMF inoculation has the potential to mitigate simazine accumulation in the topsoil and reduce its availability. [ABSTRACT FROM AUTHOR]

Prolonged droughts can cause environmental stress, even in ecosystems that are already adapted to dry conditions. In these areas life greatly depends on rare, sporadic rainfall events that can produce flash floods. Today, urban expansion, population growth and development are occurring worldwide, including along hyperarid coastlines, an ecological zone on the extreme of habitability. In such places, the absence of the already limited precipitation can lead to long‐lasting damage, and recognizing drought conditions in the past is useful for planning. Recognizing droughts, however, is challenging because they are not known as depositional events, and therefore may be under‐recognized in the sedimentological record. Floods in these hyperarid deserts carry eroded sediments and deposit them in either terrestrial or marine terminal basins. In the hyperarid (ca 30 mm rain per year) desert surrounding the northern Gulf of Aqaba‐Eilat some flash floods reach the sea and deposit alluvial sediments (mostly silt and clay) on the shelf. Following a recent 17 year drought period (1995 to 2012) a coarser surface layer was recognized offshore the outlet of an ephemeral river, despite the lack of incoming flood material. This coarsened layer resulted from a prolonged period wherein mixing and winnowing of fine particles at the surface was not interrupted by recurrent flash floods. In the bottom of two sediment cores collected from the same shelf, a similarly coarsened layer was observed. The terminal level of this deep coarse layer was dated to ca 660 yr bp, corresponding with the end of the Medieval Warm Period (ca 1350 ad). These findings suggest that the medieval anomaly resulted in a prolonged drought period in this already arid region. These results present a new interpretation of grain‐size distribution records that provides a means to reconstruct drought histories in hyperarid regions globally. [ABSTRACT FROM AUTHOR]

The impact of global warming on the metabolic state of a species may be examined by either measuring physiological rates across a latitudinal gradient or by assessing short‐term responses under experimentally controlled temperature regimes. The combination of the two approaches is seldom used but it provides valuable information on an organism's responses to temperature at broader temporal and spatial scales while allowing the isolation of temperature effects from other environmental variables.Here we used both approaches to assess the warming effects on the total acquisition of dissolved inorganic nitrogen (DIN; nitrate, ammonium) and organic N (DON; amino acids, peptides) by the globally widespread seagrass Zostera marina. DIN and DON uptake rates were measured in plants from three sites covering the species latitudinal distribution in Europe (Iceland, UK and Portugal). The responses of DIN and DON uptake rates of plants from the middle latitude (UK) to a latitudinal range of temperatures (8, 12 and 17°C) were also measured. We further examined the microbial uptake of DON along the latitudinal distribution and whether temperature is the main driver of that uptake.Our results showed that warming greatly increased the total N uptake by Z. marina and also the relative contribution of DON to total N acquisition. The microbial uptake of DON increased towards warmer latitudes, and temperature was the main driver of these observations.Ocean warming will increase the nitrogen demand of Z. marina and this demand may be met by an increasing uptake of organic nitrogen forms. This indicates that Z. marina, and probably other seagrass species, can be winners under global change as nitrogen uptake capacity will not limit growth driven by increased photosynthetic assimilation of CO2. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Healthcare exchange often contains peril for consumers because of numerous barriers to financial well‐being (FWB). Rather than ruing specific agendas of healthcare policy, we embrace a neutral and immediately actionable approach. The authors promote gains in healthcare's current composition by empowering consumers to be proactive, where possible, in reducing power inequities and improving their own FWB. As such, the authors identify primary barriers to the FWB of healthcare consumers and propose individual opportunities within the existing healthcare structure that are likely to improve fiscal outcomes. Moreover, the current research demonstrates collaborative paths wherein power‐holders (i.e., practitioner, researcher, consumer, government) can collaborate toward and/or contribute to the same financial health. A proposed theoretical framework, with foundations of power‐responsibility equilibrium and transformative service research, gives rise to future research directions. This research is intended to provide a foundation for healthcare and FWB thought/action, and to guide coming scholarly offerings. [ABSTRACT FROM AUTHOR]

In contrast to the situation in plants inhabiting most of the world's ecosystems, mycorrhizal fungi are usually absent from roots of the only two native vascular plant species of maritime Antarctica, Deschampsia antarctica and Colobanthus quitensis. Instead, a range of ascomycete fungi, termed dark septate endophytes (DSEs), frequently colonise the roots of these plant species. We demonstrate that colonisation of Antarctic vascular plants by DSEs facilitates not only the acquisition of organic nitrogen as early protein breakdown products, but also as non‐proteinaceous d‐amino acids and their short peptides, accumulated in slowly‐decomposing organic matter, such as moss peat. Our findings suggest that, in a warming maritime Antarctic, this symbiosis has a key role in accelerating the replacement of formerly dominant moss communities by vascular plants, and in increasing the rate at which ancient carbon stores laid down as moss peat over centuries or millennia are returned to the atmosphere as CO2. [ABSTRACT FROM AUTHOR]

This study examines the links between estuarine dynamics and longitudinal distributions of remotely sensed reflectance in estuaries. Reflectance at 655 nm from Landsat‐8 correlates with in situ measurements of surface turbidity. Images collected from 2013 to 2018 are used to investigate the spatial and temporal characteristics of reflectance distribution in six selected estuaries with different dynamics. The results show that the maximum magnitude (C max) and location (X max) of the reflectance are functions of two major forcing variables, the freshwater discharge and tidal stage. Salt wedge estuaries (i.e., the Fraser River, Connecticut River, and Columbia River estuary) are affected strongly by river discharge and are relatively less affected by tidal forcing. In salt wedge estuaries, the C max values along the river channel are correlated with river discharge, while the X max values generally are not. In partially mixed to strain‐induced periodic stratification (SIPS) estuaries (i.e., Delaware River) and SIPS‐to‐well‐mixed estuaries (i.e., Gironde estuary), the X max values are correlated with river discharge, but the C max values are not. SIPS‐to‐well‐mixed estuaries (i.e., Gironde estuary) and highly time‐dependent salt wedge to well‐mixed estuaries (i.e., Merrimack River estuary) are affected by tidal forcing. In these estuaries, the C max values are correlated with tidal stage. The C max values tend to be lower around high tide than low tide. Overall, the results demonstrate that remote sensing observations of ocean color can be utilized to infer subsurface estuarine processes. Satellite ocean color is a potential tool to monitor river discharge and to classify estuaries. Plain Language Summary: Estuaries are dynamic environments where river freshwater mixes with seawater. The relative strength of river flow relative to flow caused by ocean tides determines how and where freshwater and seawater mix in estuaries, which in turn affects various processes important to humans, like biological productivity and diversity, harbor siltation, and transport of pollutants. It is a challenge to classify estuaries on a global scale due to limited in situ observations. However, satellite remote sensing observations are able to provide repeated, snapshot views of surface water color over large spatial scale. In this study, we examine the links between estuarine dynamics and remote sensing observations in six different estuaries using satellite imagery. The observations demonstrate that satellite‐derived maximum magnitude and position in surface reflectance, which is related to particle concentration, are correlated with river flow and tidal forcing, which can be used to infer different types of estuaries. Remotely sensed observations can also be useful for inferring the subsurface water mixing and sediment resuspension in estuaries. In addition, the responses of maximum in surface particle concentration and its location to river discharge can be used for satellite‐based estimation of river discharge. Key Points: The spatial and temporal variability of Rrs distribution indicate different types of estuariesRemotely sensed observations are useful for inferring the subsurface estuarine processesReflectance‐based discharge retrieval offers a new potential approach for riverine and estuarine monitoring [ABSTRACT FROM AUTHOR]

Background: Age‐related variance in episodic memory can be accounted for in part by the retrieval of less precise mnemonic representations, independently of age differences in recollection success. Whether these selective deficits in memory precision are exacerbated in older adults with mild cognitive impairment (MCI) is unknown. Method: Healthy older adults and adults with MCI recalled item‐location associations in a circular space. Distance errors between the remembered and true location of each item were fit with a probabilistic mixture model to determine the probability that a given response belonged to a Gaussian distribution with a mean distance error of zero (indicating memory success), or to a uniform distribution comprising the full range of possible responses (indicating memory failure). We defined memory precision as the variability in distance errors during successful retrieval trials (i.e., belonging to the Gaussian component). Result: Item recognition and source memory accuracy were reduced in the MCI cohort relative to healthy older adults. By contrast, the precision of successfully retrieved item‐location associations did not differ between the two groups. Conclusion: Retrieval success and mnemonic precision represent dissociable sources of variance in memory performance in older age and mild cognitive impairment. [ABSTRACT FROM AUTHOR]

Summary: Despite considerable attention over the last 25 yr, the importance of early protein breakdown products to plant nitrogen (N) nutrition remains uncertain.We used rhizosphere injection of 15N‐, 13C‐ and 14C‐labelled inorganic N and amino acid (l‐alanine), with chase periods from 1 min to 24 h, to investigate the duration of competition for amino acid between roots (Triticum aestivum) and soil microorganisms. We further investigated how microbial modification of l‐alanine influenced plant carbon (C) and N recovery.From recovery of C isotopes, intact alanine uptake was 0.2–1.3% of added. Soil microbes appeared to remove alanine from soil solution within 1 min and release enough NH4+ to account for all plant 15N recovery (over 24 h) within 5 min. Microbially generated inorganic or keto acid C accounted for < 25% of the lowest estimate of intact alanine uptake.Co‐location of C and N labels appears a reasonable measure of intact uptake. Potential interference from microbially modified C is probably modest, but may increase with chase period. Similarly, competition for l‐alanine is complete within a few minutes in soil, whereas NO3− added at the same rate is available for > 24 h, indicating that long chase periods bias outcomes and fail to accurately simulate soil processes. [ABSTRACT FROM AUTHOR]

Optical properties are used to understand the spatial and temporal variability of particle properties and distribution within the Columbia River Estuary, especially in the salinity transition zone and in the estuarine turbidity maximum region. Observations of optical properties in the Columbia River Estuary are consistent with the established model that the river water brings more organic, smaller particles into the estuary, where they flocculate and settle into the salt wedge seaward of the density front. Large tidal currents resuspend mineral‐rich, larger aggregates from the seabed, which accumulate at the density front. Optical proxies for particle size (beam attenuation exponent γ and backscattering exponent γbb) are compared to conventional measurements. The γ and γbb are different to the expected trend with Sauter mean diameter Ds of suspended particles from low‐ to medium‐salinity waters (LMW). Ds increases in the LMW as does the γ derived from a WET Labs ac‐9, which indicates that the particle population dominating the ac‐9 is decreasing in size. The most likely explanation is that flocculation acting at LMW transfers mass preferentially from medium‐sized particles to large‐sized particles that are out of the size range to which the ac‐9 is most sensitive; γbb shows no trend in the LMW. Since γbb is a proxy of proportion of fine particles versus large flocs, the variation of γbb may be insensitive to changes in the medium‐sized particles. The overall results demonstrate that γbb is a reliable proxy for changes in particle size in a stratified environment. Plain Language Summary: Suspended particles delivered by rivers affect water quality in estuaries, so effective and economical monitoring of the variability of particles is particularly important in environmental management. Direct measurements of suspended particle size, concentration, and composition from water samples require substantial time and labor, which has driven efforts to develop indirect, yet accurate, alternative measurements of particle properties. In this study, we used optical instruments to measure particle variability within the Columbia River Estuary. The observations demonstrate that the river water delivered smaller, organic particles to the estuary, where they aggregated with one another and deposited to the seafloor. Large tidal currents resuspended mineral‐rich, larger aggregates from the seafloor, and these aggregates accumulated in the region where river waters encountered coastal ocean waters that flowed into the estuary. We observed that optical measurements related to particle size were different from the expected trend in the transition zone between fresh, river water and salty, coastal water. This unexpected trend requires more study, but we propose that it was caused by preferential aggregation of medium‐sized organic‐rich particles into large particles. This process would affect the processing of carbon, nutrients, and contaminants in estuaries. Key Points: Optical properties provide a good representation of particle dynamics in the Columbia River EstuaryVariations of alternative optical proxies for particle size are different to the expected trend at salinity transition zoneObservations are consistent with a model of preferential flocculation of medium‐sized particles [ABSTRACT FROM AUTHOR]

Incorporating crop residues and biochar has received increasing attention as tools to mitigate atmospheric carbon dioxide ( CO2) emissions and promote soil carbon (C) sequestration. However, direct comparisons between biochar, torrefied biomass, and straw on both labile and recalcitrant soil organic matter ( SOM) remain poorly understood. In this study, we explored the impact of biochars produced at different temperatures and torrefied biomass on the simple C substrates (glucose, amino acids), plant residues ( Lolium perenne L.), and native SOM breakdown in soil using a 14C labeling approach. Torrefied biomass and biochars produced from wheat straw at four contrasting pyrolysis temperatures (250, 350, 450, and 550 °C) were incorporated into a sandy loam soil and their impact on C turnover compared to an unamended soil or one amended with unprocessed straw. Biochar, torrefied biomass, and straw application induced a shift in the soil microbial community size, activity, and structure with the greatest effects in the straw-amended soil. In addition, they also resulted in changes in microbial carbon use efficiency ( CUE) leading to more substrate C being partitioned into catabolic processes. While overall the biochar, torrefied biomass, and straw addition increased soil respiration, it reduced the turnover rate of the simple C substrates, plant residues, and native SOM and had no appreciable effect on the turnover rate of the microbial biomass. The negative SOM priming was positively correlated with biochar production temperature. We therefore ascribe the increase in soil CO2 efflux to biochar-derived C rather than that originating from SOM. In conclusion, the SOM priming magnitude is strongly influenced by both the soil organic C quality and the biochar properties. In comparison with straw, biochar has the greatest potential to promote soil C storage. However, straw and torrefied biomass may have other cobenefits which may make them more suitable as a CO2 abatement strategy. [ABSTRACT FROM AUTHOR]

Background Multiple cardiac and non-cardiac processes may cause an elevated highly sensitive troponin ( hsTn). We postulated that the consumption of a seriously hot vindaloo could cause an increase in hsTn levels in seemingly healthy volunteers. Objective To determine whether eating a very hot curry can cause elevated hsTn. Methods This was a prospective observational cohort study. Participants had blood drawn for hsTn pre-ingestion and at 2 and 4 h post-ingestion of, first, a rather mild butter chicken and, 2 weeks later, a seriously hot lamb vindaloo. We assessed pre-curry tolerance and perception of curry hotness for both curries using the VHOT scale. Results Although no participant had a troponin above the reference range at any point in time, we found dramatic relative increases in troponin in many of our participants. In the vindaloo phase, 8/22 (36%) had a relative change >20%, whereas 5/22 (23%) had a relative change >50% at 4 h. However, these changes were not significantly different to those in the butter chicken phase. Based on biological variability alone, 15/22 (68%) had a relative change of >20%, and 11/22 (50%) had a relative change of >50% between the two sessions (pre-ingestion). Conclusions Eating a seriously hot vindaloo does not appear to be a risk factor for troponitis, and people may consume vindaloo safely with the knowledge that this is unlikely to result in significant damage to their myocardium. However, clinicians should be aware of the biological variability of hsTn and exercise caution when interpreting apparent changes within the normal range. [ABSTRACT FROM AUTHOR]

Dissolved organic nitrogen (DON) forms a significant pool of bioavailable N in the water column (62%) and in sediments of Ria Formosa lagoon (53%). We assessed the uptake rates of inorganic and organic nitrogen and its interactions in the seagrass Zostera marina, and further explored the possibility of seagrasses to use complex organic substrates (peptides). Uptake rates by leaves and roots were quantified in choice-uptake experiments where plants were exposed to mixed N solutions containing both 15N inorganic (ammonium + nitrate) and 13C15N organic (alanine + trialanine) nitrogen at field-relevant concentrations, and compared with uptake rates of single inorganic or organic N forms. Ammonia was the preferred N source, but plants preferred DON to nitrate. DON uptake was significantly higher through roots than leaves, coinciding with the one-order of magnitude higher concentration of DON in the sediment than in the water. Not only amino acids, as reported elsewhere for other seagrasses, but also peptides constitute relevant N sources for Z. marina (10% and 4% of the total N uptake). Seagrasses may thus compete with microbes for organic substrates at an earlier stage of protein degradation in the N cycle than previously thought. Because no interactions occurred between inorganic and organic N sources, the total N uptake by Z. marina was higher when both sources were present, showing that organic nitrogen is a complementary rather than alternative source of nitrogen. The uptake of organic nitrogen should be included in future studies assessing the total N budgets of seagrass meadows. [ABSTRACT FROM AUTHOR]

Increasing atmospheric carbon dioxide ( CO2) concentration is both a strong driver of primary productivity and widely believed to be the principal cause of recent increases in global temperature. Soils are the largest store of the world's terrestrial C. Consequently, many investigations have attempted to mechanistically understand how microbial mineralisation of soil organic carbon ( SOC) to CO2 will be affected by projected increases in temperature. Most have attempted this in the absence of plants as the flux of CO2 from root and rhizomicrobial respiration in intact plant-soil systems confounds interpretation of measurements. We compared the effect of a small increase in temperature on respiration from soils without recent plant C with the effect on intact grass swards. We found that for 48 weeks, before acclimation occurred, an experimental 3 °C increase in sward temperature gave rise to a 50% increase in below ground respiration (ca. 0.4 kg C m−2; Q10 = 3.5), whereas mineralisation of older SOC without plants increased with a Q10 of only 1.7 when subject to increases in ambient soil temperature. Subsequent 14C dating of respired CO2 indicated that the presence of plants in swards more than doubled the effect of warming on the rate of mineralisation of SOC with an estimated mean C age of ca. 8 years or older relative to incubated soils without recent plant inputs. These results not only illustrate the formidable complexity of mechanisms controlling C fluxes in soils but also suggest that the dual biological and physical effects of CO2 on primary productivity and global temperature have the potential to synergistically increase the mineralisation of existing soil C. [ABSTRACT FROM AUTHOR]

1. The amount of carbon (C) stored in soil is an important regulator for the global climate and soil fertility and is the balance between formation and decomposition of soil organic matter (SOM). Decomposition of SOM can be powerfully affected by labile carbon (C) supplements in, for example, the rhizosphere. A stimulation of SOM mineralisation induced by labile C additions is termed ‘priming’, and the mechanisms for this phenomenon remain elusive. 2. The most widely held explanation assigns priming to successional dynamics in r- and K-selected groups within the microbial community; groups which have also been connected with fungal (K-selected) and bacterial (r-selected) decomposers. New evidence has also suggested that recently formed SOM is particularly sensitive to priming. We investigated (i) the labile C concentration dependence of SOM mineralisation, (ii) the susceptibility of differently aged SOM to priming and (iii) if priming is due to bacterial or fungal growth dynamics. 3. To create an age gradient of traceable SOM, we spiked a pasture soil using 14C glucose, and subsampled plots 1 day, 2 months, 5 months and 13 months after application (i.e. SOM aged 1 day – 13 months). Glucose (0–4000 μgCg-1 ) was added in subsequent laboratory experiments, and respiration, SOM mineralisation (14CO2 evolution), bacterial growth rates (leucine incorporation) and fungal biomass (ergosterol) were tracked during ca. 1 week. 4. Mineralisation of SOM aged 2–13 months showed similar labile C concentration dependencies, and priming increased mineralisation of SOM systematically by up to 350%. The glucose treatments induced variable microbial growth responses for differently aged SOM, which were unrelated to the priming effect. 5. That successional dynamics in microbial r- and K-selected groups, or bacterial and fungal decomposers, respectively, underpinned priming was incompatible with the results obtained. An alternative explanation could be that SOM transformation by extracellular enzymes, for subsequent respiration, could be triggered by labile C. In conclusion, labile C primed the mineralisation of 2–13 months aged SOM, and the mechanism for this priming was unrelated to microbial growth dynamics. [ABSTRACT FROM AUTHOR]

In monoculture, certain plant species are able to preferentially utilize different nitrogen (N) forms, both inorganic and organic, including amino acids and peptides, thus forming fundamental niches based on the chemical form of N. Results from field studies, however, are inconsistent: Some showing that coexisting plant species predominantly utilize inorganic N, while others reveal distinct interspecies preferences for different N forms. As a result, the extent to which hypothetical niches are realized in nature remains unclear. Here, we used in situ stable isotope tracer techniques to test the idea, in temperate grassland, that niche partitioning of N based on chemical form is related to plant productivity and the relative availability of organic and inorganic N. We also tested in situ whether grassland plants vary in their ability to compete for, and utilize peptides, which have recently been shown to act as an N source for plants in strongly N-limited ecosystems. We hypothesized that plants would preferentially use NO3−-N and NH4+-N over dissolved organic N in high-productivity grassland where inorganic N availability is high. On the other hand, in low-productivity grasslands, where the availability of dissolved inorganic N is low, and soil availability of dissolved organic N is greater, we predicted that plants would preferentially use N from amino acids and peptides, prior to microbial mineralization. Turves from two well-characterized grasslands of contrasting productivity and soil N availability were injected, in situ, with mixtures of 15N-labeled inorganic N ( NO3− and NH4+) and 13C15N labeled amino acid ( l-alanine) and peptide ( l-tri-alanine). In order to measure rapid assimilation of these N forms by soil microbes and plants, the uptake of these substrates was traced within 2.5 hours into the shoots of the most abundant plant species, as well as roots and the soil microbial biomass. We found that, contrary to our hypothesis, the majority of plant species across both grasslands took up most N in the form of NH4+, suggesting that inorganic N is their predominant N source. However, we did find that organic N was a source of N which could be utilized by plant species at both sites, and in the low-productivity grassland, plants were able to capture some tri-alanine-N directly. Although our findings did not support the hypothesis that differences in the availability of inorganic and organic N facilitate resource partitioning in grassland, they do support the emerging view that peptides represent a significant, but until now neglected, component of the terrestrial N cycle. [ABSTRACT FROM AUTHOR]

The high degree to which plant roots compete with soil microbes for organic forms of nitrogen ( N) is becoming increasingly apparent. This has culminated in the finding that plants may consume soil microbes as a source of N, but the functional significance of this process remains unknown., We used 15 N- and 14 C-labelled cultures of soil bacteria to measure rates of acquisition of microbes by sterile wheat roots and plants growing in soil. We compared these rates with acquisition of 15 N delivered as nitrate, amino acid monomer ( l-alanine) and short peptide ( l-tetraalanine), and the rate of decomposition of [14 C] microbes by indigenous soil microbiota., Acquisition of microbe 15 N by both sterile roots and roots growing in soil was one to two orders of magnitude slower than acquisition of all other forms of 15 N. Decomposition of microbes was fast enough to account for all 15 N recovered, but approximately equal recovery of microbe 14 C suggests that microbes entered roots intact., Uptake of soil microbes by wheat ( Triticum aestivum) roots appears to take place in soil. If wheat is typical, the importance of this process to terrestrial N cycling is probably minor in comparison with fluxes of other forms of soil inorganic and organic N. [ABSTRACT FROM AUTHOR]

Arctic tundra ecosystems contain 14% of the global soil carbon ( C) store which is becoming vulnerable to decomposition. Arctic soil organic matter ( SOM) contains large amounts of old, recalcitrant, high molecular weight ( MW) C compounds which are protected from decomposition whilst soils remain frozen. Climatic change alters soil temperature and water regimes in the Arctic, however, the impact of these changes on C decomposition and storage is poorly understood., We investigated vegetation emergence, microbial dynamics and nutrient fluxes in response to snow melt on the high Arctic Svalbard archipelago using field and laboratory studies. Using bacterial and archaeal genetic material (16 S rRNA) and ammonia-oxidising genes, microbial communities were quantified in transects across the active snow melt front. The effects of soil temperature and water content on SOM decomposition rates were measured using 14 C-labelled low and high MW compounds., Vegetation and below-ground microbial communities, in the field, responded rapidly with peaks in nutrient availability and soil respiration observed within 72 h of snowmelt. Temperature strongly drives early growing season C dynamics in the Arctic. We suggest the nutrient peaks following snowmelt, coupled with higher levels of DNA in the subniveal zone are due to the decomposition of bacteria and archaea from previous years., We show, in the laboratory, when soils thaw, mineralisation of recalcitrant C (high MW) compounds was sensitive to soil water but not to increasing temperatures. In contrast, low MW compounds exhibited sensitivity to both temperature and soil water. We suggest that if future soil water content increases under climate change, high MW compounds could become more susceptible to decomposition, releasing more C to the atmosphere. [ABSTRACT FROM AUTHOR]

[i] Proteinaceous and peptidic nitrogen is a potential direct nutrient source for both plants and microbes in the soil, without prior degradation to amino acids and mineralization. We used a series of five sites along an elevation gradient from 15 m a.s.l. to 710 m a.s.I. along which prunaty productivity decreases to investigate peptide utilization rates by soil microbes. Using 14C-labeled L-alanine, L-dialanine, and L-trialanine in a series of incubation experiments, we show that peptides are directly and rapidly assimilated by soil microbes, and that they are utilized for both biomass production and respiration. Alanine, dialanine, and trialanine were mineralized rapidly by soil microbes from the five sites along the gradient. Across all five sites, dialanine and trialanine were mineralized faster than alanine. In competition experiments, a 100-fold excess of alanine had no effect on the rate of trialanine mineralization in four of the five sites, and the same excess of trialanine had no effect on alanine mineralization. This is indicative of uptake of the intact peptide by the soil microbial community. Our findings have implications for understanding terrestrial nitrogen cycling because they point to a short-circuit whereby large peptides and proteins need only be extracellularly cleaved to short chain length peptides before direct assimilation by microbes. [ABSTRACT FROM AUTHOR]

Background and Purpose: Hydrogen sulphide (H(2)S) is a labile, endogenous metabolite of cysteine, with multiple biological roles. The development of sulphide-based therapies for human diseases will benefit from a reliable method of quantifying H(2)S in blood and tissues.Experimental Approach: Concentrations of reactive sulphide in saline and freshly drawn whole blood were quantified by reaction with the thio-specific derivatization agent monobromobimane, followed by reversed-phase fluorescence HPLC and/or mass spectrometry. In pharmacokinetic studies, male rats were exposed either to intravenous infusions of sodium sulphide or to H(2)S gas inhalation, and levels of available blood sulphide were measured. Levels of dissolved H(2)S/HS(-) were concomitantly measured using an amperometric sensor.Key Results: Monobromobimane was found to rapidly and quantitatively derivatize sulphide in saline or whole blood to yield the stable small molecule sulphide dibimane. Extraction and quantification of this bis-bimane derivative were validated via reversed-phase HPLC separation coupled to fluorescence detection, and also by mass spectrometry. Baseline levels of sulphide in blood were in the range of 0.4-0.9 microM. Intravenous administration of sodium sulphide solution (2-20 mg x kg(-1) x h(-1)) or inhalation of H(2)S gas (50-400 ppm) elevated reactive sulphide in blood in a dose-dependent manner. Each 1 mg x kg(-1) x h(-1) of sodium sulphide infusion into rats was found to be pharmacokinetically equivalent to approximately 30 ppm of H(2)S gas inhalation.Conclusions and Implications: The monobromobimane derivatization method is a sensitive and reliable means to measure reactive sulphide species in whole blood. Using this method, we have established a bioequivalence between infused sodium sulphide and inhaled H(2)S gas. [ABSTRACT FROM AUTHOR]

Background and Purpose: Sodium sulphide (Na(2)S) disassociates to sodium (Na(+)) hydrosulphide, anion (HS(-)) and hydrogen sulphide (H(2)S) in aqueous solutions. Here we have established and characterized a method to detect H(2)S gas in the exhaled breath of rats.Experimental Approach: Male rats were anaesthetized with ketamine and xylazine, instrumented with intravenous (i.v.) jugular vein catheters, and a tube inserted into the trachea was connected to a pneumotach connected to a H(2)S gas detector. Sodium sulphide, cysteine or the natural polysulphide compound diallyl disulphide were infused intravenously while the airway was monitored for exhaled H(2)S real time.Key Results: Exhaled sulphide concentration was calculated to be in the range of 0.4-11 ppm in response to i.v. infusion rates ranging between 0.3 and 1.1 mg x kg(-1) x min(-1). When nitric oxide synthesis was inhibited with N(omega)-nitro-L-arginine methyl ester the amount of H(2)S exhaled during i.v. infusions of sodium sulphide was significantly increased compared with that obtained with the vehicle control. An increase in circulating nitric oxide using DETA NONOate [3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene] did not alter the levels of exhaled H(2)S during an i.v. infusion of sodium sulphide. An i.v. bolus of L-cysteine, 1 g.kg(-1), and an i.v. infusion of the garlic derived natural compound diallyl disulphide, 1.8 mg x kg(-1) x min(-1), also caused exhalation of H(2)S gas.Conclusions and Implications: This method has shown that significant amounts of H(2)S are exhaled in rats during sodium sulphide infusions, and the amount exhaled can be modulated by various pharmacological interventions. [ABSTRACT FROM AUTHOR]

1. Exchange of carbon dioxide (CO2) from soils can contribute significantly to the global warming potential (GWP) of agro-ecosystems. Due to variations in soil type, climatic conditions and land management practices, exchange of CO2 can differ markedly in different geographical locations. The food industry is developing carbon footprints for their products necessitating integration of CO2 exchange from soils with other CO2 emissions along the food chain. It may be advantageous to grow certain crops in different geographical locations to minimize CO2 emissions from the soil, and this may provide potential to offset other emissions in the food chain, such as transport. 2. Values are derived for the C balance of soils growing horticultural crops in the UK, Spain and Uganda. Net ecosystem production ( NEP) is firstly calculated from the difference in net primary production ( NPP) and heterotrophic soil respiration ( Rh). Both NPP and Rh were estimated from intensive direct field measurements. Secondly, net biome production ( NBP) is calculated by subtracting the crop biomass from NEP to give an indication of C balance. The importance of soil exchange is discussed in the light of recent discussions on carbon footprints and within the context of food life-cycle assessment (LCA). 3. The amount of crop relative to the biomass and the Rh prevailing in the different countries were the dominant factors influencing the magnitude of NEP and NBP. The majority of the biomass for lettuce Lactuca sativa and vining peas Pisum sativum, was removed from the field as crop; therefore, NEP and NBP were mainly negative. This was amplified for lettuces grown in Uganda (−16·5 and −17 t C ha−1 year−1 compared to UK and Spain −4·8 to 7·4 and −5·1 to 6·3 t C ha−1 year−1 for NEP and NBP, respectively) where the climate elevated Rh. 4. Synthesis and applications. This study demonstrates the importance of soil emissions in the overall life cycle of vegetables. Variability in such emissions suggests that assigning a single value to food carbon footprints may not be adequate, even within a country. Locations with high heterotrophic soil respiration, such as Spain and Uganda (21·9 and 21·6 t C ha−1 year−1, respectively), could mitigate the negative effects of climate on the C costs of crop production by growth of crops with greater returns of residue to the soil. This would minimize net CO2 emissions from these agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Abstract Thickness variations across-levee and downchannel in acoustically defined depositional sequences from six submarine channel-levee systems show consistent and quantifiable patterns. The thickness of depositional sequences perpendicular to the channel trend, i.e. across the levee, decreases exponentially, as characterized by a spatial decay constant, k . Similarly, the thickness of sediment at the levee crest decreases exponentially down the upper reaches of submarine channels and can be characterized by a second spatial decay constant, λ. The inverse of these decay constants has units of length and defines depositional length scales such that k -1 is a measure of levee width and λ-1 is a measure of levee length. Quantification of levee architecture in this way allowed investigation of relationships between levee architecture and channel dimensions. It was found that these measures of levee e-folding width and levee e-folding length are directly related to channel width and relief. The dimensions of channels and levees are thus intimately related, thereby limiting the range of potential channel-levee morphologies, regardless of allocyclic forcing. A simple sediment budget model relates the product of the levee e-folding width and e-folding length to through-channel volume discharge. A classification system based on the quantitative downchannel behaviour of levee architecture allows identification of a ‘mid-channel’ reach, where sediment is passively transferred from the through-channel flow to the levees as an overspilling flow. Downstream from this reach, the channel gradually looses its control on guiding turbidity currents, and the resulting flow can be considered as an unconfined or spreading flow. [ABSTRACT FROM AUTHOR]

Educationist Willis Hawley's paper identifies some of the chief sources of tension and confusion in American educational policy. The article presents comments of the author on Hawley's paper. The first is that the concern for innovation pervades the whole educational system, and that correctives which stop at the school level are unlikely to succeed. The second is that there are some identifiable prerequisites to an adaptive education, which research can help bring about.

A letter to the editor about babesiosis in dogs in Great Britain is presented.