Seasonal variations in plant species effects on soil N and P dynamics

It is well established that plant species influence ecosystem processes, but we have little ability to predict which vegetation changes will alter ecosystems, or how the effects of a given species might vary seasonally. We established monocultures of eight plant species in a California grassland in order to determine the plant traits that account for species impacts on nitrogen and phosphorus cycling. Plant species differed in their effects on net N mineralization and nitrification rates, and the patterns of species differences varied seasonally. Soil PO4- and microbial P were more strongly affected by slope position than by species. Although most studies focus on litter chemistry as the main determinant of plant species effects on nutrient cycling, this study showed that plant species affected biogeochemical cycling through many traits, including direct traits (litter chemistry and biomass, live-tissue chemistry and biomass) and indirect traits (plant modification of soil bioavailable C and soil microclimate). In fact, species significantly altered N and P cycling even without litter inputs. It became particularly critical to consider the effects of these multiple traits in order to account for seasonal changes in plant species effects on ecosystems. For example, species effects on potential rates of net N mineralization were most strongly influenced by soil bioavailable C in the fall and by litter chemistry in the winter and spring. Under field conditions, species effects on soil microclimate influenced rates of mineralization and nitrification, with species effects on soil temperature being critical in the fall and species effects on soil moisture being important in the dry spring. Overall, this study clearly demonstrated that in order to gain a mechanistic, predictive understanding of plant species effects on ecosystems, it is critical to look beyond plant litter chemistry and to incorporate the effects of multiple plant traits on ecosystems.     

Building resilience and adaptation to manage Arctic change

Unprecedented global changes caused by human actions challenge society's ability to sustain the desirable features of our planet. This requires proactive management of change to foster both resilience (sustaining those attributes that are important to society in the face of change) and adaptation (developing new socioecological configurations that function effectively under new conditions). The Arctic may be one of the last remaining opportunities to plan for change in a spatially extensive region where many of the ancestral ecological and social processes and feedbacks are still intact. If the feasibility of this strategy can be demonstrated in the Arctic, our improved understanding of the dynamics of change can be applied to regions with greater human modification. Conditions may now be ideal to implement policies to manage Arctic change because recent studies provide the essential scientific understanding, appropriate international institutions are in place, and Arctic nations have the wealth to institute necessary changes, if they choose to do so.     

Ozone artifacts and carbonyl measurements using Tenax GR, Tenax TA, Carbopack B, and Carbopack X adsorbents

Four popular thermally desorbable adsorbents used for air sampling (Tenax TA, Tenax GR, Carbopack B, and Carbopack X) are examined for the potential to form artifacts with ozone (O3) at environmental concentrations. The performance of these adsorbents for the ketone and aldehyde species identified as O3-adsorbent artifacts was also characterized, including recovery, linearity, and method detection limits (MDLs). Using gas chromatography/mass spectrometry, 13 different artifacts were identified and confirmed for both Tenax TA and Tenax GR, 9 for Carbopack B, but none for Carbopack X. Several O3 artifacts not reported previously were identified, including: pentanal, 3-hexanone, 2-hexanone, hexanal, 3-heptanone, and heptanal with Tenax TA; pentanal, 3-hexanone, 2-hexanone, hexanal, and 3-heptanone on Tenax GR; and 1-octene and 1-nonene with Carbopack B. Levels of straight-chain aldehyde artifacts rapidly diminished after a few cycles of adsorbent conditioning/O3 exposure, and concentrations could be predicted using a first-order model. Phenyl-substituted carbonyl artifacts (benzaldehyde and acetophenone) persisted on Tenax TA and GR even after 10 O3 exposure-conditioning cycles. O3 breakthrough through the adsorbent bed was most rapid in adsorbents that yielded the highest levels of artifacts. Overall, artifact composition and concentration are shown to depend on O3 concentration and dose, conditioning method, and adsorbent type and age. Calibrations showed good linearity, and most compounds had reasonable recoveries, for example, 90 +/- 15% for Tenax TA, 97 +/- 23% for Tenax GR, 101 +/- 24% for Carbopack B, and 79 +/- 25% (91 +/- 9% for n-aldehydes) for Carbopack X. Benzeneacetaldehyde recovery was notably poorer (22-63% across the four adsorbents). MDLs for several compounds were relatively high, up to 5 ng. By accounting for both artifact formation and method performance, this work helps to identify which carbonyl compounds can be measured using thermally desorbable adsorbents and which may be prone to bias because of the formation of O3-adsorbent artifacts.     

Partial amniotic carbon dioxide insufflation for fetal surgery

Partial amniotic carbon dioxide insufflation (PACI) involves insufflating the amniotic sac with carbon dioxide (CO₂) and, in some cases, draining some of the amniotic fluid. The creation of a gaseous intra-amniotic compartment improves visualization, even in the presence of limited bleeding, and creates the work space required for complex fetoscopic procedures. Clinically, PACI is mostly used to perform fetoscopic myelomeningocele (MMC) repair, enabling a minimally invasive alternative to open fetal surgery. However, evidence of the fetal safety of PACI is limited. Previous animal experiments in sheep demonstrate that PACI induces fetal hypercapnia and acidosis with largely unknown short and longer term implications. In this review, we examine the literature for the physiological effects of intrauterine insufflation pressure, duration, humidity, and the role of maternal hyperventilation on fetal physiology and well-being.     

User behaviour, best practice and the risks of non-target exposure associated with anticoagulant rodenticide use

Usage of anticoagulant rodenticides (ARs) is an integral component of modern agriculture and is essential for the control of commensal rodent populations. However, the extensive deployment of ARs has led to widespread exposure of a range of non-target predatory birds and mammals to some compounds, in particular the second-generation anticoagulant rodenticides (SGARs). As a result, there has been considerable effort placed into devising voluntary best practice guidelines that increase the efficacy of rodent control and reduce the risk of non-target exposure. Currently, there is limited published information on actual practice amongst users or implementation of best practice. We assessed the behaviour of a typical group of users using an on-farm questionnaire survey. Most baited for rodents every year using SGARs. Most respondents were apparently aware of the risks of non-target exposure and adhered to some of the best practice recommendations but total compliance was rare. Our questionnaire revealed that users of first generation anticoagulant rodenticides rarely protected or checked bait stations, and so took little effort to prevent primary exposure of non-targets. Users almost never searched for and removed poisoned carcasses and many baited for prolonged periods or permanently. These factors are all likely to enhance the likelihood of primary and secondary exposure of non-target species.     

Risk-based modelling of diffuse land use impacts from rural landscapes upon salmonid fry abundance

Research has demonstrated that landscape or watershed scale processes can influence instream aquatic ecosystems, in terms of the impacts of delivery of fine sediment, solutes and organic matter. Testing such impacts upon populations of organisms (i.e. at the catchment scale) has not proven straightforward and differences have emerged in the conclusions reached. This is: (1) partly because different studies have focused upon different scales of enquiry; but also (2) because the emphasis upon upstream land cover has rarely addressed the extent to which such land covers are hydrologically connected, and hence able to deliver diffuse pollution, to the drainage network. However, there is a third issue. In order to develop suitable hydrological models, we need to conceptualise the process cascade. To do this, we need to know what matters to the organism being impacted by the hydrological system, such that we can identify which processes need to be modelled. Acquiring such knowledge is not easy, especially for organisms like fish that might occupy very different locations in the river over relatively short periods of time. However, and inevitably, hydrological modellers have started by building up piecemeal the aspects of the problem that we think matter to fish. Herein, we report two developments: (a) for the case of sediment associated diffuse pollution from agriculture, a risk-based modelling framework, SCIMAP, has been developed, which is distinct because it has an explicit focus upon hydrological connectivity; and (b) we use spatially distributed ecological data to infer the processes and the associated process parameters that matter to salmonid fry. We apply the model to spatially distributed salmon and fry data from the River Eden, Cumbria, England. The analysis shows, quite surprisingly, that arable land covers are relatively unimportant as drivers of fry abundance. What matters most is intensive pasture, a land cover that could be associated with a number of stressors on salmonid fry (e.g. pesticides, fine sediment) and which allows us to identify a series of risky field locations, where this land cover is readily connected to the river system by overland flow.     

Total mercury loadings in sediment from gold mining and conservation areas in Guyana

The Low Carbon Development Strategy proposed in June 2009 by the government of Guyana in response to the Reducing Emissions from Deforestation and Forest Degradation in Developing Countries program has triggered evaluation of forest-related activities, thereby acting as a catalyst for improvements in Guyana's small- to medium-scale gold mining industry. This has also shed light on areas committed to conservation, something that has also been handled by Non Governmental Organizations. This paper compares water quality and mercury concentrations in sediment from four main areas in Guyana, two that are heavily mined for gold using mercury amalgamation methods (Arakaka and Mahdia) and two that are considered conservation areas (Iwokrama and Konashen). Fifty-three sediment and soil mercury loadings ranged from 29 to 1,200 ng/g and averaged 215 ± 187 ng/g for all sites with similar averages in conservation and mining areas. Sediment loadings are within the range seen in French Guiana and Suriname, but conservation area samples had higher loadings than the corresponding uncontaminated baselines. Type of ore and location in the mining process seemed to influence mercury loadings. Mercury sediment loadings were slightly positively correlated with pH (correlation coefficient = 0.2; p value < 0.001) whereas no significant correlations were found with dissolved oxygen or turbidity.     

Complex karyotypic mosaicism as a result of non-disjunction and subsequent centromere fission

Karyotypic discrepancy among four different cell types is described in tissues derived from a pregnancy terminated because of chromosomal anomalies. Chorionic villus cells demonstrated 46,XX (direct preparation) and 46, XX/47,XX,+marl (cultured cells) karyotypes, while fetal skin fibroblasts had a karyotype of 47,XX,+ 18 and the placenta showed a triple mosaicism of 47,XX, + 18/47,XX,+mar1/48,XX,+ 18,+mar2. The origin of this complex chromosomal distribution and its significance are discussed in comparison with findings in similar cases.     

Thermal radiation from vented dust explosions

The fireball from a vented dust explosion presents a danger to personnel who may be within the vicinity of the event. The risk of serious injury to people caught within the fireball is great, and anyone just outside the fireball may be at risk from thermal radiation. This report describes a project in which the effects of thermal radiation from vented dust explosions was studied. The aim was to establish the areas around a fireball in which people would be at risk from thermal radiation. Six dusts were tested in a large vented vessel and external fireballs were generated under a range of conditions. The fireball geometry and the heat flux from the fireball were studied. A range of material samples were exposed to the fireball. The safe areas around the fireballs were established for each of the six dusts. Generally, the larger vent areas resulted in the larger fireballs and high heat pulse values. However, the fireball was usually too brief to ignite fabric samples unless they were very close to the fireball. The work has shown that in most cases the safe area was relatively close to the surface of the largest fireball.