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Spatial navigation deficits are often observed among older adults on tasks that require navigating virtual reality (VR) environments on a computer screen. We investigated whether these age differences are attenuated when tested in more naturalistic and ambulatory virtual environments. In Experiment 1, young and older adults navigated a variant of the Morris Water Maze task in each of two VR conditions: a desktop VR condition which required using a mouse and keyboard to navigate, and an ambulatory VR condition which permitted unrestricted locomotion. In Experiment 2, we examined whether age- and VR-related differences in spatial performance were affected by the inclusion of additional spatial cues. In both experiments, older adults navigated to target locations less precisely than younger individuals in the desktop condition. Age differences were significantly attenuated, however, when tested in the ambulatory VR environment. These findings underscore the importance of developing naturalistic assessments of spatial memory and navigation. [ABSTRACT FROM AUTHOR]

Spatial navigation and memory are often seen as heavily intertwined at the cognitive and neural levels of analysis. We review models that hypothesize a central role for the medial temporal lobes, including the hippocampus, in both navigation and aspects of memory, particularly allocentric navigation and episodic memory. While these models have explanatory power in instances in which they overlap, they are limited in explaining functional and neuroanatomical differences. Focusing on human cognition, we explore the idea of navigation as a dynamically acquired skill and memory as an internally driven process, which may better account for the differences between the two. We also review network models of navigation and memory, which place a greater emphasis on connections rather than the functions of focal brain regions. These models, in turn, may have greater explanatory power for the differences between navigation and memory and the differing effects of brain lesions and age. Neurobiological models often assume a correspondence between memory and spatial navigation based on the idea of the cognitive map. The authors review recent literature, highlighting important distinctions between memory and navigation and discussing novel models for their independent neural underpinnings. [ABSTRACT FROM AUTHOR]

Recall that under spatial randomness, the number of events in quadrat I i i has the distribution Graph HT ht Poisson( I A i ). Then we may observe Graph HT ht If E Graph HT ht = Var Graph HT ht , then the empirical VMR should be close to 1, indicating that the events are spatially random. Consider the distribution of events in Figure 4 partitioned now into two Graph HT ht rectangular quadrats (instead of four quadrats). [Extracted from the article]

Recent research suggests that episodic memory is associated with systematic differences in the localization of neural activity observed during memory encoding and retrieval. The retrieval-related anterior shift is a phenomenon whereby the retrieval of a stimulus event (e.g., a scene image) is associated with a peak neural response which is localized more anteriorly than the response elicited when the stimulus is experienced directly. Here, we examine whether the magnitude of the anterior shift (i.e., the distance between encoding- and retrieval-related response peaks) is moderated by age, and also whether the shift is associated with memory performance. Younger and older human subjects of both sexes underwent fMRI as they completed encoding and retrieval tasks on word-face and word-scene pairs. We localized peak scene and face selectivity for each individual participant within the face-selective precuneus and in three scene-selective (parahippocampal place area [PPA], medial place area, occipital place area) ROIs. In line with recent findings, we identified an anterior shift in the PPA and occipital place area in both age groups and, in older adults only, in the medial place area and precuneus also. Of importance, the magnitude of the anterior shift was larger in older than in younger adults. The shift within the PPA exhibited an age-invariant across-participant negative correlation with source memory performance, such that a smaller displacement between encoding- and retrieval-related neural activity was associated with better performance. These findings provide novel insights into the functional significance of the anterior shift, especially in relation to memory decline in older age. [ABSTRACT FROM AUTHOR]

The physical, chemical and biological attributes of a soil combined with abiotic factors (e.g. climate and topography) drive pedogenesis and some of these attributes have been used as proxies to soil quality. Thus, we investigated: (1) whether appropriate soil quality indicators (SQIs) could be identified in soils of Great Britain, (2) whether conventional soil classification or aggregate vegetation classes (AVCs) could predict SQIs and (3) to what extent do soil types and/ or AVCs act as major regulators of SQIs. Factor analysis was used to group 20 soil attributes into six SQI which were named as; soil organic matter (SOM), dissolved organic matter (DOM), soluble N, reduced N, microbial biomass, DOM humification (DOMH). SOM was identified as the most important SQI in the discrimination of both soil types and AVCs. Soil attributes constituting highly to the SOM factor were, microbial quotient and bulk density. The SOM indicator discriminated three soil type groupings and four aggregate vegetation class groupings. Among the soil types, only the peat soils were discriminated from other groups while among the AVCs only the heath and bog classes were isolated from others. However, the peat soil and heath and bog AVC were the only groups that were distinctly discriminated from other groups. All other groups heavily overlapped with one another, making it practically impossible to define reference values for each soil type or AVC. The two-way ANOVA showed that the AVCs were a better regulator of the SQIs than the soil types. We conclude that conventionally classified soil types cannot predict the SQIs defined from large areas with differing climatic and edaphic factors. Localised areas with similar climatic and topoedaphic factors may hold promise for the definition of SQI that may predict the soil types or AVCs. [ABSTRACT FROM AUTHOR]

Plant S deficiency is common, but the role of S-containing amino acids such as cysteine in plant S uptake is unknown. We applied 14C-, 35S-, 13C-, and 15N-labelled cysteine to wheat and oilseed rape rhizospheres and traced the plants' elemental uptake. Both plants absorbed 0.37–0.81% of intact cysteine after 6 h with no further increase after 24 h. They absorbed 1.6–11.5% 35S and 12.3–7.6% 15N from cysteine after 24 h and utilised SO42− as their main S source (75.5–86.4%). Added and naturally occurring cysteine-S contributed 5.6 and 1.1% of total S uptake by wheat and oilseed rape, respectively. Cysteine and inorganic S derived from cysteine contributed 24.5 and 13.6% of uptake for wheat and oilseed rape, respectively, after 24 h. Oilseed rape absorbed ~10-fold more S from cysteine and SO42− than did wheat. The highest absorption of free cysteine should be in the organic-rich soil patches. Soil microorganisms rapidly decomposed cysteine (t1/2 = 1.37 h), and roots absorbed mineralised inorganic N and S. After 15 min, 11.7–14.3% of the 35S-cysteine was retained in the microbial biomass, while 30.2–36.7% of the SO42− was released, suggesting that rapid microbial S immobilisation occurs after cysteine addition. Plants acquire N and S from cysteine via unidirectional soil-to-root nutrient flow, and cysteine is an important S source for plants. [ABSTRACT FROM AUTHOR]

Functional magnetic resonance imaging (fMRI) is among the foremost methods for mapping human brain function but provides only an indirect measure of underlying neural activity. Recent findings suggest that the neurophysiological correlates of the fMRI blood oxygenation level-dependent (BOLD) signal might be regionally specific. We examined the neurophysiological correlates of the fMRI BOLD signal in the hippocampus and neocortex, where differences in neural architecture might result in a different relationship between the respective signals. Fifteen human neurosurgical patients (10 female, 5 male) implanted with depth electrodes performed a verbal free recall task while electrophysiological activity was recorded simultaneously from hippocampal and neocortical sites. The same patients subsequently performed a similar version of the task during a later fMRI session. Subsequent memory effects (SMEs) were computed for both imaging modalities as patterns of encoding-related brain activity predictive of later free recall. Linear mixed-effects modeling revealed that the relationship between BOLD and gamma-band SMEs was moderated by the lobar location of the recording site. BOLD and high gamma (70-150 Hz) SMEs positively covaried across much of the neocortex. This relationship was reversed in the hippocampus, where a negative correlation between BOLD and high gamma SMEs was evident. We also observed a negative relationship between BOLD and low gamma (30-70 Hz) SMEs in the medial temporal lobe more broadly. These results suggest that the neurophysiological correlates of the BOLD signal in the hippocampus differ from those observed in the neocortex. [ABSTRACT FROM AUTHOR]

• Retrieval gating allows retrieved content to be aligned with a retrieval goal. • Younger adults show retrieval gating as operationalized by cortical reinstatement. • Older adults failed to demonstrate evidence of retrieval gating. • Scene reinstatement correlated with memory performance in younger adults only. Retrieval gating refers to the ability to modulate the retrieval of features of a single memory episode according to behavioral goals. Recent findings demonstrate that younger adults engage retrieval gating by attenuating the representation of task-irrelevant features of an episode. Here, we examine whether retrieval gating varies with age. Younger and older adults incidentally encoded words superimposed over scenes or scrambled backgrounds that were displayed in one of three spatial locations. Participants subsequently underwent fMRI as they completed two memory tasks: the background task, which tested memory for the word's background, and the location task, testing memory for the word's location. Employing univariate and multivariate approaches, we demonstrated that younger, but not older adults, exhibited attenuated reinstatement of scene information when it was goal-irrelevant (during the location task). Additionally, in younger adults only, the strength of scene reinstatement in the parahippocampal place area during the background task was related to item and source memory performance. Together, these findings point to an age-related decline in the ability to engage retrieval gating. [ABSTRACT FROM AUTHOR]

Amyris is a fermentation product company that leverages synthetic biology and has been bringing novel fermentation products to the market since 2009. Driven by breakthroughs in genome editing, strain construction and testing, analytics, automation, data science, and process development, Amyris has commercialized nine separate fermentation products over the last decade. This has been accomplished by partnering with the teams at 17 different manufacturing sites around the world. This paper begins with the technology that drives Amyris, describes some key lessons learned from early scale-up experiences, and summarizes the technology transfer procedures and systems that have been built to enable moving more products to market faster. Finally, the breadth of the Amyris product portfolio continues to expand; thus the steps being taken to overcome current challenges (e.g. automated strain engineering can now outpace the rest of the product commercialization timeline) are described. [ABSTRACT FROM AUTHOR]

Aims: The capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role? Methods: Growing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases. Results: We found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity. Conclusions: Our results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture. [ABSTRACT FROM AUTHOR]

Soil soluble nitrogen (N) is crucial to the N nutrition and productivity of plants. Consequently, understanding the factors that affect its pool size and composition is of considerable importance. Here, six typical forest types in northeast China were investigated to determine the dynamics of soil soluble N across seasons and plant communities, and the potential drivers. Soil free amino acids, NH4+, NO3−, dissolved organic N (DON) and a variety of soil characteristics were measured over the growing season (from May to September). Seasonality showed a stronger effect on the availability of soil inorganic N and free amino acids than vegetation. The coefficients of variation of soil inorganic N, amino acid-N and the potential drivers (moisture and DON) appeared to be greater for season, and the concentrations of these available N sources tended to be higher at the beginning than at the height of growing season. Potential soil drivers (e.g. moisture, microbial biomass-N and DON) and plant phenology together drove the seasonal dynamics of inorganic N and amino acid-N. Arginine, histidine, serine, leucine, aspartic acid, glycine, glutamic acid and proline composed the dominant soil amino acid pool in the temperate forest soils. The basic amino acids (arginine and histidine) were consistently dominant irrespective of vegetation and season, suggesting that selective sorption by the soil solid phase could play an important role in regulating the cycling of amino acid-N in these temperate forest ecosystems. This research indicates that changes in local soil properties, and plant phenology caused by seasonality, exert a powerful influence on the characteristics of plant-soil N cycling. [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]

Abstract The frequency and intensity of extreme weather events (e.g. flood, drought) are predicted to increase for the foreseeable future and it is expected that these will negatively impact upon agroecosystem functioning. Our understanding of how grassland ecosystems respond to extreme weather events occurring at different times of the year, however, is lacking. To better understand the seasonal response of grassland to flooding, we subjected an agricultural grassland to an 8-week extreme flood event at three different temperatures (5 °C-winter, 15 °C-spring/autumn and 25°C-summer) and then followed its subsequent recovery for 9 weeks after floodwater removal. We focused on key indicators of ecosystem functioning including primary production, nutrient cycling, greenhouse gas (GHG) emissions, ammonia (NH 3) volatilization, and soil microbial communities. The experiment used intact soil mesocosms (1 kg) with indigenous vegetation collected from a grassland with no previous history of flooding. Flooding reduced biomass production by 18% at 5 °C, 50% at 15 °C and 95% at 25 °C. Flooding also significantly disrupted elemental cycling (nitrogen, phosphorus and carbon) as evidenced by an increased release of P, Fe and NH 4 + into the soil and overlying floodwater and large amounts of CH 4 and NH 3 released to the atmosphere (mainly during the flooding). These effects were more pronounced at higher temperatures (e.g. 45–700 kg CH 4 C ha−1 and 1–5 kg NH 3 N ha−1 at 15 and 25 °C, respectively). In addition, after floodwater removal this NH 4 + was rapidly nitrified leading to large losses of N 2 O (1.0–14.2 kg N 2 O N ha−1 at 5–25 °C, respectively). Especially at higher temperatures, flooding resulted in a reduction in soil microbial biomass (more than 58% of the equivalent unflooded treatment at 25 °C) and changes in microbial community structure (assessed by PLFAs). Further, some of these changes persisted after flood removal including a loss of actinomycetes, arbuscular mycorrhizal fungi and fungi. Overall, we conclude that ecosystem responses to extreme weather events are critically dependent on temperature with those occurring at higher temperatures having a greater negative impact than those at the lowest temperature (5 °C). The large potential release of CH 4 and N 2 O also suggests that flood events should be considered as a potential source of GHGs when comparing top-down and bottom-up calculations of national inventories, and that further work is needed to better refine GHG emission estimates for these events. Highlights • Flooding induced a rapid release of nutrients, especially at higher temperatures. • 700 kg CH 4 C ha−1 and 5 kg NH 3 N ha−1 were released in the flood phase at 25 °C. • During soil recovery, nitrification led to 1.0–14.2 kg N 2 O N ha−1 losses at 5–25 °C. • Flooding reduced soil microbial biomass, actinomycetes and arbuscular mycorrhiza. • Flooding reduced biomass production by 18% at 5 °C, 50% at 15 °C and 95% at 25 °C. [ABSTRACT FROM AUTHOR]

Understanding the processes that lead to seasonal changes in grain size on muddy macro-tidal flat and channel complexes will assist efforts to predict future changes caused by climate change and construction of infrastructure like tidal power generators, wind farms, and causeways. Surficial sediment samples were collected for disaggregated inorganic grain size (DIGS) analysis every month for 1 year from a tidal flat and from a tidal channel and its banks in Kingsport, NS, Canada, which is located in the Minas Basin of the Bay of Fundy. A process-based parameterization of the DIGS distribution was used to determine floc fraction, representative of the percentage of fine-grained material deposited to the seabed in flocs. Small changes in floc fraction occurred seasonally in the channel. Values were higher in late winter and lower in late summer. A more pronounced seasonal variation in floc fraction was observed on the tidal flats. Observed changes in floc fraction correlated with elevation. Results from this study are discussed in terms of the controls on floc fraction which include suspended particulate matter concentration (SPM), turbulence, and stickiness in the water column, all of which can be used to understand the formative processes responsible for shaping the bottom sediment texture. [ABSTRACT FROM AUTHOR]

Abstract Soils around the world are being exposed to weather events which are unprecedented in recent history. To maintain the delivery of soil-related ecosystem services and to promote greater soil resilience it is essential to understand how plant-soil systems respond to these extreme events. In this study we replicated a recent period of extreme rainfall and prolonged spring flooding in a temperate grassland which had no previous history of flooding. Intact soil mesocosms (Eutric Cambisol) 1 kg weight were subjected to a simulated long-term spring flood (15 °C, 2 months) and maintained in the light with above ground indigenous vegetation (Lolium perenne L.) or dark with and without indigenous vegetation to simulate different flood typologies. In comparison to a no-flood control treatment, nutrient cycling, water quality, air quality (greenhouse gas emissions), habitat provision and biological population regulation shifts were evaluated. Flooding induced a rapid release of nutrients into the soil solution and overlying floodwater, resulting in potential nutrient losses up to 15 mg Fe, 16 mg NH 4 +, 360 mg DOC and 28 mg DON, per mesocosm. The presence of plants increased the rate of nutrient release (especially P), with the effects magnified when light transmission through the floodwater was restricted (1.3 mg P vs 0.2 mg P, per mesocosm). Flooding induced a rapid decline in redox potential and subsequent production of CH 4 , especially in the darkened treatments (10 and between 11 and 16 times higher than the control, without and with light restrictions, respectively). Upon removal of the floodwater, the accumulated NH 4 + was nitrified leading to a shift in greenhouse gas emissions, from CH 4 to N 2 O emissions. N 2 O was only significantly produced in the mesocosms kept under light restrictions (13 times higher than in other two treatments). Flooding eliminated earthworms, reduced grass production after soil recovery (from 28 g for control mesocosms to 11 g and <1 g for flooded mesocosms without and with light restrictions, respectively). Soil microbial biomass was also reduced (up to a 22–27% of the total PLFAs) and flooding induced shifts in microbial community structure, particularly a loss of soil fungi. The soil fungi content quickly recovered (4 weeks) when light was not restricted during the flood period, however, no such recovery was seen in the darkened treatments. Overall, we conclude that extreme flood events cause rapid and profound changes in soil function. Both the impact of the flooding and the time to recover is exacerbated when light is restricted (e.g. in sediment laden floodwater). In addition, our results suggest that the presence of flood-resilient plants can mitigate against some of the negative impacts of flooding on soil functioning. Highlights • Flooding eliminated earthworms and altered soil microbial community structure. • Flooding reduced the size of the microbial biomass and fungal content. • Vegetation played a vital role in preserving soil quality during flooding. • Decomposition of vegetation induced P loss in light restricted floodwater. • Impact of flooding was greater under light restricted floodwater conditions. [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]

Abstract Large ice blocks containing enough sediment to be denser than sea water form in the Minas Basin of the Bay of Fundy, Canada. Ice block composition and the timing of ice block formation were monitored to improve understanding of the potential threat to tidal power generators posed by collision with ice blocks. Field studies were carried out in 2012 and 2013 in the Kennetcook River, which is a tributary of the Minas Basin of the Bay of Fundy. In 2012, the cross-sectional area of the channel at the study site decreased by 21% due to the formation of ice walls. In 2013, it decreased by 24%. Large ice blocks separated from the ice walls during spring tides following a time lag of the minimum air temperature. The time lag was 20 days in 2012 and 21 days in 2013. Eleven percent of samples from ice blocks were denser than sea water. Highlights • Ice block composition and formation were monitored in Canada's Bay of Fundy. • In 2012 ice walls caused a channel's cross-sectional area to decrease by 21%. • Ice walls collapsed into ice blocks lagging spring tide and air temperature minimum. • 11% of ice block samples were denser than sea water due to sediment content. [ABSTRACT FROM AUTHOR]

The hybrid integration of single-crystal (SC) diamond membranes with on-chip optical devices has the potential to service many applications, spanning non-linear optics to quantum photonics with embedded diamond colour centres. Limited dimensions of high optical quality diamond however restrict the size and number of devices that can be fabricated on a single chip, which impedes the use of diamond in large photonic integrated circuitry. Here we show the fabrication and integration of a 1 μm thick SC diamond membrane with a silicon photonic device. The quality of the diamond-silicon interface is measured using SEM and optical techniques. Silicon microring resonators are measured after integration with the diamond film and show a low excess loss of 0.4 dB and a group index dispersion that is dependent on the mode confinement in the diamond layer. [ABSTRACT FROM AUTHOR]

Behavioral studies using delay and social discounting as indices of self-control and altruism, respectively, have revealed functional similarities between farsighted and social decisions. However, neural evidence for this functional link is lacking. Twenty-five young adults completed a delay and social discounting task during fMRI scanning. A spatiotemporal partial least squares analysis revealed that both forms of discounting were well characterized by a pattern of brain activity in areas comprising frontoparietal control, default, and mesolimbic reward networks. Both forms of discounting appear to draw on common neurocognitive mechanisms, regardless of whether choices involve intertemporal or interpersonal outcomes. We also observed neural profiles differentiating between high and low discounters. High discounters were well characterized by increased medial temporal lobe and limbic activity. In contrast, low discount rates were associated with activity in the medial prefrontal cortex and right temporoparietal junction. This pattern may reflect biological mechanisms underlying behavioral heterogeneity in discount rates. [ABSTRACT FROM AUTHOR]

Hill, P.S. and Gelati, S., 2017. Competent vs. observed grain size on the seabed of the Gulf of Maine and Bay of Fundy. The output of a three-dimensional tidal circulation model and nearly 10,000 sediment samples are used to compare observed and competent grain sizes on the floor of the Gulf of Maine and Bay of Fundy. Competent grain size is the largest grain size a flow is capable of mobilizing. Competent and observed grain sizes have similar broad spatial distributions. Coarser observed grain sizes are found in regions of larger stress, and associated coarser competent grain sizes and finer observed sizes are found in regions with finer competent sizes. Areas in which competent sizes are finer than observed sizes likely have significant sources of seabed stress that are not included in the model, specifically from waves and subtidal flows. Areas in which competent sizes are coarser than observed sizes likely are regions where sediment input into the region overwhelms the ability of near-bed flows to transport sediment away from the region, leaving the seabed with a texture similar to that of the supply. The results indicate that sediment texture is unlikely to change greatly if large-scale tidal power development is pursued in Minas Passage, which connects the Minas Basin to the Outer Bay of Fundy. Forecast changes of sediment texture in the Gulf of Maine are small, and in the Bay of Fundy, sediment texture is unlikely to change because it is dominated by sediment supply, which should not be affected by tidal power development. [ABSTRACT FROM AUTHOR]

Optical instruments that measure the particulate beam attenuation and backscattering coefficients have been used widely to estimate suspended particulate mass (SPM) in various environments. In pycnoclines, density differences can cause significant forward light scattering (schlieren). This fluid-induced scattering increases the measured by instruments with small acceptance angles that are open to the environment (not pumped). When the 1-m bin-averaged buoyancy frequency ( N) exceeds 0.05 s−1 in the Columbia River estuary, inaccurate estimates of are observed by such instruments. The schlieren phenomena do not affect the and measured with a pumped transmissometer or a backscattering meter. It follows that to obtain a reliable proxy of SPM in a highly stratified environment, the use of either a backscattering sensor or a pumped transmissometer is required. [ABSTRACT FROM AUTHOR]

Extreme flood events are predicted to have a negative impact on soil quality. Currently, there is a lack of information about the effect of agricultural practices on soil functioning and microbial processes under these events. We hypothesized that the impact of flooding on soil quality will be exacerbated when crop residues are present in the soil as they will induce more extreme anaerobicity. A spring extreme flood event (10 °C, 9 weeks) was simulated in mesocosms containing an arable sandy-loam soil low in nutrients. The main treatments were (1) with and without flooding and (2) with and without maize residue addition (8 Mg ha). We monitored changes in soil chemical quality indicators (e.g. pH, salinity, Fe, P, C, NH , NO and organic N), greenhouse gas (GHG) emissions (CO, CH, NO) and soil microbial community composition (PLFAs) during a prolonged flood period (9 weeks) and an 8-week 'recovery' period after flooding. In comparison to the other treatments, flooding in the presence of crop residues resulted in a dramatic drop in soil redox potential. This was associated with the enhanced release of Fe and C into solution and an increase in CH emissions. In contrast, maize residues reduced potential nitrate losses and NO emissions, possibly due to complete denitrification and microbial N immobilization. Both flooding and maize residues stimulated microbial growth and promoted a shift in microbial community composition. Following floodwater removal, most of the soil quality indicators returned to the levels of the control treatment within 5 weeks. After this short recovery phase, no major impact of flooding could be observed on plant growth (maize pot-grown). Overall, we conclude that both extreme flooding and management regime negatively impact upon a range of soil quality indicators (e.g. redox, GHG emissions); however, the soil showed high resilience and recovered quickly after floodwater removal. Further work is required to investigate the impact of repeated extreme flood events on soil quality and function over longer timescales. [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]

The strong tidal currents of the Minas Passage in the Bay of Fundy, Nova Scotia, have made this area an important site for testing and development of tidal power technologies. Understanding sediment processes in this area is essential for determining the impacts that large-scale tidal power extraction would have on the system. Previous estimates of sediment input to the Basin suggest that much more sediment enters the Basin than accumulates within it; therefore, the bottom sediment texture should be in hydrodynamic equilibrium with bottom currents. A recent study, however, showed that sediment texture is generally finer that what was expected based on current speeds. This paper uses geographic information systems methods to provide updated and more highly resolved measurements of the amount of sediment entering the Minas Basin from the dominant source, which is coastal erosion. Volumetric input from coastal erosion is 1.1 × 106 m3·a−1, which is more than two times smaller than previous estimates. This updated value makes input rates comparable to accumulation rates, and agrees with the hypothesis that bottom sediment texture is not in equilibrium with current speeds. Grain-size distributions also support the hypothesis that the Minas Basin acts as a sediment trap. [ABSTRACT FROM AUTHOR]

Carcinoid syndrome is a paraneoplastic condition, which usually affects the lungs or gastrointestinal tract but uncommonly cardiac valves can be involved, causing carcinoid heart disease. We describe a case of a 60-year-old man presented with a twelve-month history of worsening shortness of breath and decreased exercise tolerance. Investigations confirmed grade 1 metastatic neuroendocrine carcinoma (carcinoid tumour) of likely gastrointestinal tract origin. Two months after diagnosis he underwent successful tricuspid valve replacement and pulmonary root replacement. Cytoreductive surgery of the right lobe of the liver and the ileal primary is planned. Cardiac surgery is the only definitive treatment for carcinoid heart disease and should be considered in all those with symptoms and evidence of severe valvular disease. [ABSTRACT FROM AUTHOR]

Shrublands cover a large proportion of the world’s land surface, yet they remain poorly studied in comparison to other ecosystems. Within shrublands, soil organic matter (SOM) is replenished from inputs of both above- and below-ground plant litter, however, their relative importance depends on their respective turnover rates. To critically address this, we measured the biodegradation rates of the soluble and insoluble components of 14 C-labelled above- and below-ground plant litter in soil. During the 150 day incubation, the amount of plant-derived soluble-C lost as 14 CO 2 was similar for the different plant parts being 64.7 ± 2.3% for roots, 72.1 ± 7.4% for stems, and 72.4 ± 1.8% for leaves. In comparison, the turnover of the insoluble fraction was much slower. However, again little difference in mineralisation was seen for the different plant parts with the total losses being 21.1 ± 0.9% for roots, 19.5 ± 1.6% for stems, and 19.6 ± 1% for leaves. A double exponential first order kinetic model fitted well to the experimental data. It also allowed the partitioning of C between microbial anabolic and catabolic processes for the soluble C component. Using this model, we deduced that the soluble fraction turns over ca. 40 times annually, whereas it takes ca. 2.5 years to turnover the insoluble fraction. For the soluble plant component, the overall microbial carbon use efficiency (CUE) was estimated to be greater for root-derived C in comparison to that derived from aboveground (no difference was observed for the insoluble component). From this, we tentatively suggest that C sourced from belowground plant components may persist longer in soil than C derived from aboveground plant components. [ABSTRACT FROM AUTHOR]

The article focuses on the impact of the December 2015 passage of the Every Student Succeeds Act (ESSA) which reauthorized the long-standing Elementary and Secondary Education Act (ESEA). It mentions that the shift in attention to student performance and results as a risk of democratic experimentalism. It also mentions that the states in partnership with the U.S. Department of Education should share lessons to accelerate progress toward more effective schooling for all students.

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]

Size-specific sediment retention by diatom biofilms was measured by eroding intertidal muds at increasing shear stresses (0.01–0.60 Pa) using a Gust microcosm. The grain sizes eroded from biofilm-covered sediment were compared to those from control cores from which the biofilms were destroyed using bleach. Biofilms were quantified using carbohydrate measurements. Cores from an intertidal mud flat in the Minas Basin of the Bay of Fundy (Canada) showed biofilms preferentially retained clays and very fine silts relative to fine and medium silts. In contrast, prior field observations on an intertidal sand flat indicated that fine and medium silts were preferentially retained by biofilms relative to clays and very fine silts. These contrasting results suggest a link between size-specific sediment retention and sediment texture, where sand biofilms retain coarser, non-cohesive sediment grains, while mud biofilms retain finer, cohesive sediment grains. This relationship implies that biofilms could contribute to a positive feedback that would preserve existing sediment texture. [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]

Total suspended matter (TSM) concentrations were derived from ocean colour imagery (MERIS satellite data) in Minas Basin. Analysis of time series of TSM in 1-km 2 pixel boxes revealed an annual cycle in TSM in most parts of the Basin. Higher TSM of up to 85 g/m 3 was observed in late-winter (February–March), and lower TSM of 5–10 g/m 3 characterized late-summer (July–August). The largest annual variation occurred in the centre of Basin, and the smallest variation occurred in shallow areas. Satellite-derived TSM, supported by in situ observations, were compared to predictions using the Delft3D model. Increasing model erosion rate in winter relative to summer improved agreement between model and satellite-derived TSM. In comparison with the satellite-derived estimates, the model underestimated TSM in shallow areas in summer and overestimated it in winter. This discrepancy is likely due to inaccurate satellite-derived TSM in shallow, high-concentration areas of the Basin. [ABSTRACT FROM AUTHOR]

In this study, we first determined the low molecular weight dissolved organic carbon (LMW DOC) concentration-dependent kinetics of soil respiration in a temperate grassland soil sampled on successive occasions. We then used the established relationship to estimate in situ LMW DOC concentrations from basal respiration measurements. 14C-labelled glucose was used as a model substrate and was added to soil over a wide range of concentrations (0.05-4000 μg C g−1 DW soil; equivalent to ca. 2.5 μM-200 mM glucose-C). The time-dependent loss of 14C-glucose to 14CO2 was similar to previous assessments. The Michaelis-Menten parameter Vmax varied between 17 (September 2010) and 42 (October 2010) μg CO2-C g−1 h−1 (corresponding to 1.4-3.5 µmol CO2 g−1 h−1), while Km varied between 893 (September 2010) and 1990 (October 2010) μg glucose-C g−1 (41-92 mM glucose), thus within the span previously reported for soils, albeit in the higher end of the range. However, the estimates were 6 orders-of-magnitude greater than those found in previous studies in natural waters. A possible methodological reason for this difference was an induced multiphasic concentration dependence, biasing Km and Vmax with high concentrations of LMW DOC. By combining the established concentration dependences with measurements of basal respiration, we estimated in situ concentrations of LMW DOC of 131 (October 2010), 112 (January 2011) and 270 (September 2010) μg LMW DOC g−1, far exceeding the total DOC concentration in the soil (17-20 μg DOC g−1 soil), thus invalidating our approach. We propose a way forward, and suggest that although current estimates of LMW DOC cycling need revision, there is evidence for a rapidly cycling pool of LMW DOC, possibly turning over >30 times per day, that warrants further attention. [ABSTRACT FROM AUTHOR]

Amino acid and oligopeptide-nitrogen (N) forms only a minor component of the total dissolved N pool in grassland soils, yet the importance of these N-pools for plant productivity will ultimately depend on the rate at which these pools turnover. Fluxes of dissolved organic matter (DOM) through the soil solution are frequently estimated from measurements of respiration, but this method fails to consider any delay between microbial substrate acquisition and mineralization. Here, we added 14C-labelled alanine and tri-alanine (10 μM) to 4 soils collected from a natural grassland productivity gradient and then measured substrate depletion from the soil solution and the subsequent production of 14CO2 resulting from mineralization at 1-60 min. There was a considerable delay between microbial 14C removal from the soil solution, which occurred extremely rapidly (up to 96% of added substrate depleted within a minute), and 14CO2 evolution resulting from the fast turnover of the alanine and tri-alanine. This indicates that amino acid and peptide longevity in the soil solution of the soils in this grassland productivity gradient has been greatly overestimated from measurements of mineralization alone. Rates of substrate uptake and mineralization by microbes declined in less productive, N-limited grassland soils with lower levels of microbial biomass, suggesting that the availability of organic N for plant uptake is likely to be controlled by soil microbial activity. We estimate that amino acid and peptide pools occurring in the most productive grassland soils may turnover at a rate of up to 20 times a minute, representing a very considerable flux of N through the soil. [ABSTRACT FROM AUTHOR]

Highlights: [•] We examined the extent to which working memory contributes to future thought. [•] Future thought was closely related to parallel measures of autobiographical memory. [•] Working memory contributed to the construction of unique future event depictions. [•] Working memory was not related to the access or elaboration of event details. [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]

Abstract: Throughout the last glacial period, massive volumes of icebergs were discharged periodically through Hudson Strait during so-called Heinrich (H) events. These icebergs transported sediments that were subsequently deposited in distinct layers across the North Atlantic as they melted. The objective of this research was to measure and describe sedimentation associated with a meltwater plume discharged during the H1 ice-rafting event at about 17ka by examining sediment texture. The H1 layer was sampled in 11 piston cores that cover about 4000km of the slope between Hudson Strait and the Gulf of Maine. Disaggregated inorganic grain size (DIGS) distributions were determined using a Coulter Counter. Additionally, the CaCO3 content and the >63μm fraction were measured and DIGS distributions were sorted using entropy analysis. Entropy analysis proved to be a useful tool for distinguishing between sediment delivery mechanisms. Textural interpretation of sediment dynamics during the H1 event was broadly consistent with facies interpretations. H1 layer sediments were mainly delivered by plume and ice-rafting, with some samples showing higher-energy sorting. In general, plume deposition was dominant within 1000km of Hudson Strait, and distal sediments were mainly delivered by ice-rafting. Entropy analysis of DIGS distributions provides a robust means of understanding fine fraction (<100μm) sediment dynamics in H events. [Copyright &y& Elsevier]

Over the past 20 years, our understanding of soil nitrogen (N) cycling has changed with evidence that amino acids are major substrates for both soil microorganisms and plants. However, the recent discovery that plants and microorganisms can directly utilize small peptides in soil needs to be evaluated for its ecological significance, because peptides are released earlier in protein decomposition and thus would provide significant competitive advantage to any organism that can use them directly. We tested whether soil microorganisms took up peptides faster than amino acids across a broad range of ecosystems. We show that l-enantiomeric-peptidic-N is taken up significantly faster than the equivalent monomer, and that this is universal across soils from different ecosystems, with distinct microbial communities. Peptides may have an unrecognized, global, importance in the terrestrial N cycle, providing N to soil microorganisms at an earlier stage of decomposition than previously acknowledged. [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]

Abstract: In natural plant–soil systems and following incorporation into plants in agricultural systems, most nitrogen enters soil as protein or other biological polymers. Before this nitrogen can be taken up by soil microorganisms or plants, it must be cleaved to a form which can be transported into the organism. It is well known that soil microorganisms and many plants can utilise l-amino acids and a growing body of evidence shows that short l-peptides can be taken up without further modification. However, there has been very little empirical investigation of rates of uptake in soil. d-amino acids and their peptides are less abundant in soil than their l-enantiomeric counterparts, but do occur in significant quantities. To date their potential rate of cycling in the soil solution remains virtually unknown. We directly measured rates of uptake of 14C-labelled l- and d-alanine and their di- and tripeptides in a temperate agricultural soil. All were taken up extremely rapidly by soil microorganisms. Half-times for l-enantiomers and the d-amino acid monomer were all less than 1 min, with l-peptides accounting for the highest potential fluxes (9 nmol N g−1 DW soil min−1), more than double that of the amino acid monomer. Uptake of d-peptides was slowest with half-times in soil solution of 10 and 36 min (di- and tripeptide, respectively). Availability of l-peptides had a much stronger effect on the rate of uptake of the amino acid monomer than the amino acid monomer had on the uptake of the peptides, suggesting a microbial preference for peptides. We suggest that very high potential N fluxes and an apparent microbial preference for l-peptides indicates that most N is cycled through the soil solution as l-peptides early in protein degradation, and that this is the site of fiercest competition for soil N. [Copyright &y& Elsevier]

Abstract: Most nitrogen (N) enters many Arctic and Antarctic soil ecosystems as protein. Soils in these polar environments frequently contain large stocks of proteinaceous organic matter, which has decomposed slowly due to low temperatures. In addition to proteins, considerable quantities of d-amino acids and their peptides enter soil from bacteria and lengthy residence times can lead to racemisation of l-amino acids in stored proteins. It has been predicted that climate warming in polar environments will lead to increased rates of soil organic N turnover (i.e. amino acids and peptides of both enantiomers). However, our understanding of organic N breakdown in these soils is very limited. To address this, we tested the influence of chain length and enantiomeric composition on the rate of breakdown of amino acids and peptides in three contrasting tundra soils formed under the grass, moss or lichen-dominated primary producer communities of Signy Island in the South Orkney Islands. Both d- and l-enantiomers of the amino acid monomer were rapidly mineralized to CO2 at rates in line with those found for l-amino acids in many other terrestrial ecosystems. In all three soils, l-peptides were decomposed faster than their amino acid monomer, suggesting a different route of microbial assimilation and catabolism. d-peptides followed the same mineralization pattern as l-peptides in the two contrasting soils under grass and lichens, but underwent relatively slow decomposition in the soil underneath moss, which was similar to the soil under the grass. We conclude that the decomposition of peptides of l-amino acids may be widely conserved amongst soil microorganisms, whereas the decomposition of peptides of d-amino acids may be altered by subtle differences between soils. We further conclude that intense competition exists in soil microbial communities for the capture of both peptides and amino acids produced from protein breakdown. [Copyright &y& Elsevier]

Nitrogen is a key regulator of primary productivity in many terrestrial ecosystems. Historically, only inorganic N (NH4 + and NO3 -) and L-amino acids have been considered to be important to the N nutrition of terrestrial plants. However, amino acids are also present in soil as small peptides and in D-enantiomeric form. We compared the uptake and assimilation of N as free amino acid and short homopeptide in both L- and D-enantiomeric forms. Sterile roots of wheat (Triticum aestivum L.) plants were exposed to solutions containing either 14C-labelled L-alanine, D-alanine, L-trialanine or D-trialanine at a concentration likely to be found in soil solution (10 μM). Over 5 h, plants took up L-alanine, D-alanine and L-trialanine at rates of 0.9±0.3, 0.3±0.06 and 0.3±0.04 mmol g-1 root DW h-1, respectively. The rate of N uptake as L-trialanine was the same as that as Lalanine. Plants lost ca.60% of amino acid C taken up in respiration, regardless of the enantiomeric form, but more (ca.80%) of the L-trialanine C than amino acid C was respired. When supplied in solutions of mixed N form, N uptake as D-alanine was ca.5-fold faster than as NO3 -, but slower than as L-alanine, L-trialanine and NH4 +. Plants showed a limited capacity to take up D-trialanine (0.04±0.03 mmol g-1 root DW h-1), but did not appear to be able to metabolise it. We conclude that wheat is able to utilise L-peptide and D-amino acid N at rates comparable to those of N forms of acknowledged importance, namely L-amino acids and inorganic N. This is true even when solutes are supplied at realistic soil concentrations and when other forms of N are available. We suggest that it may be necessary to reconsider which forms of soil N are important in the terrestrial N cycle. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the fate and turnover of the pools that comprise dissolved organic nitrogen (DON) in soil is key to determining its role in ecosystem functioning. We investigated seasonal changes of dissolved organic carbon (DOC) and nitrogen (DON) concentrations within four molecular weight (MW) size fractions across an altitudinal gradient (from lowland to montane systems), and quantified individual amino acids and amino acid constituents of oligopeptidic-N, as well as nitrate and ammonium. We tested two ideas: first, that DON is more abundant than DIN in low-productivity relative to high-productivity grassland ecosystems; and second, that the abundance of peptides and amino acids is likewise greater in low- than high-productivity grassland. The most productive site had a history of inorganic fertiliser application, and hence in this site alone DIN was more abundant than DON. Plant productivity varied 3-fold between the other sites, and DON was generally at higher concentrations in the sites of lower productivity both in absolute terms as well as relative to DIN, with a large increase observed in spring. The fraction containing the highest concentration of the DON had a MW of >100 kDa, and in summer and autumn this fraction was more abundant at the lowest productivity site. We conclude that relationships between the abundance of DON relative to DIN and ecosystem productivity is dependent on season, and hence more complex than previously suggested, and that peptides are a dynamic and potentially nutritionally significant component of DON. [Copyright &y& Elsevier]

lthough progress has been made, greater efforts are needed to promote faculty diversity at the college and university levels, especially in STEM fields. Thus, it is important to elucidate best practices both for increasing awareness of diversity issues pertaining to higher education and for implementing change. This article focuses on the outcomes of a diversity workshop for college and university faculty hosted by the West Virginia Higher Education Policy Commission, Division of Science and Research. More specifically, it elucidates how participation in the workshop translated into practice at the faculty participants' home institutions. [ABSTRACT FROM AUTHOR]

Abstract: Distinguishing between root and non-root derived CO2 efflux is important when determining rates of soil organic matter turnover, however, in practice they remain difficult to separate. Our aim was to evaluate two methods for determining the component of below-ground respiration not dependent on plant roots (i.e., basal soil respiration; R b). The first approach estimated R b indirectly from the y-intercept of linear regressions between below-ground respiration (BGR) and root biomass. The second approach involved direct measurements of soil respiration from bare plots. To compare the contrasting approaches, BGR and crop biomass measurements were collected throughout the year in a range of agricultural systems. We found that both methods were very closely correlated with each other. Values of R b determined by the intercept approach, however, were slightly higher than those determined by measurement of bare plots. Both approaches showed a seasonal trend with estimates of R b lowest in winter months at 0.02 t C ha−1 month−1 for the y-intercept approach and 0.11 t C ha−1 month−1 for the bare plots approach, even after the data had been corrected for the influence of soil temperature. Highest rates of R b occurred from the height to the end of the crop growing season (0.8–1.5 t C ha−1 month−1). The annual CO2 efflux due to R b was estimated to be 8.1 t C ha−1 y−1 from the y-intercept approach and 6.8 t C ha−1 y−1 from bare plots. Annual BGR was 12.1 t C ha−1 y−1. We conclude that both methods provide similar estimates of R b, however, logistically the bare plots approach is much easier to undertake than the y-intercept approach. [Copyright &y& Elsevier]

The article discusses research on the music literacy skills of members from various adult church choirs. The conductors rated the music literacy of their choirs based on literacy in music-reading skills, music-reading skills, above average reading skills, and advanced music-reading skills. Suggestions when establishing a music-reading skills course are offered.

Abstract: The influences of wave climate and sediment supply on the depths of sand–mud transitions (h SMT) are investigated. Depths of sand–mud transitions (SMT) are based on published granulometric data from surface samples gathered from 14 sites in different wave-dominated coastal environments with fluvial input, including high energy (Columbia, Eel, Russian, San Lorenzo, Copper, and Nepean rivers), moderate energy (Ebro, Nile, Santa Clara, Tseng-wen and Kao-ping rivers), and low energy (Po, Pescara and Tronto rivers) regimes. Geometric mean diameter (GMD) and mud percent are compiled from samples along shore-normal transects, and significant correlation is found between these two textural descriptors. Nominally, the SMT is defined as the transition from GMD >63 µm to <63 µm. The correlation between mud percent and GMD permits an alternative, complementary definition of the SMT as the transition from <25% mud to >25% mud. This dual definition is applied to the 14 systems, and h SMT is tabulated for each system. Correlation is found between h SMT and the depth at which wave-induced bottom shear stress equals the critical erosion shear stress of the largest mud particles and also between h SMT and significant wave height. Lack of correlation between h SMT and sediment load of nearby rivers indicates either that the influence of sediment supply on depth of the sand–mud transition is small or is not adequately represented in this study. Shelf width and slope do not correlate with residuals from a formalized linear relationship between h SMT and significant wave height. The relationship between h SMT and wave climate is useful for calibration of numerical models of erosion and deposition in wave-dominated coastal environments, for prediction of seabed properties in remote or inaccessible areas, and for reconstruction of paleodepth based on facies changes from sand to mud in ancient rocks. [Copyright &y& Elsevier]