The National Early Warning Score and its subcomponents recorded within ±24 hours of emergency medical admission are poor predictors of hospital-acquired acute kidney injury

YesBackground: Hospital-acquired Acute Kidney Injury (H-AKI) is a common cause of avoidable morbidity and mortality. Aim: To determine if the patients’ vital signs data as defined by a National Early Warning Score (NEWS), can predict H-AKI following emergency admission to hospital. Methods: Analyses of emergency admissions to York hospital over 24-months with NEWS data. We report the area under the curve (AUC) for logistic regression models that used the index NEWS (model A0), plus age and sex (A1), plus subcomponents of NEWS (A2) and two-way interactions (A3). Likewise for maximum NEWS (models B0,B1,B2,B3). Results: 4.05% (1361/33608) of emergency admissions had H-AKI. Models using the index NEWS had the lower AUCs (0.59 to 0.68) than models using the maximum NEWS AUCs (0.75 to 0.77). The maximum NEWS model (B3) was more sensitivity than the index NEWS model (A0) (67.60% vs 19.84%) but identified twice as many cases as being at risk of H-AKI (9581 vs 4099) at a NEWS of 5. Conclusions: The index NEWS is a poor predictor of H-AKI. The maximum NEWS is a better predictor but seems unfeasible because it is only knowable in retrospect and is associated with a substantial increase in workload albeit with improved sensitivity.The Health Foundatio

Effects of fungal seed pathogens under conspecific and heterospecific trees in a temperate forest

This is the accepted manuscript of an article published by the NRC Research Press.This study investigated the impacts of soil fungi on seeds of two eastern North American temperate-zone trees: Acer saccharum (sugar maple) and Tsuga canadensis (eastern hemlock). Seeds of each species were buried at locations dominated by either conspecifics or heterospecifics. Half were protected with fungicide, and net consequences for survival and germination were assessed. Net effects of fungicide usually were positive, indicating pathogens affected seeds more strongly than any potential mutualists. Losses of A. saccharum to fungi were modest, and almost identical in areas dominated by itself vs. areas dominated by T. canadensis. In contrast, fungal impacts on T. canadensis were strongly habitat-dependent: losses to fungi were high in T. canadensis-dominated sites, but not in A. saccharum-dominated sites. This result is consistent with an accumulation of host-specific pathogens, either by a direct feedback between T. canadensis and its fungal enemies, or indirectly through modification of the soil environment. Even though these two trees share similar habitats, responses to fungicide indicate that their seeds are affected very differently by the soil environment.This is a publication of the Koffler Scientific Reserve at Jokers Hill. This research was supported by NSERC Research and Equipment Grants. The National Tree Seed Centre kindly donated the seeds used in this experiment

Effects of gap area and shape on recolonization by grassland plants with differing reproductive strategies

This is the accepted manuscript of an article published by the NRC Research Press. The manuscript does not include figures. To view figures, please consult the publisher's version of this article.Species with poor dispersal ability initially should be slower to colonize larger or rounder gaps than smaller or less circular gaps. Conversely, dispersive and seed-banking species should be less sensitive than poor dispersers to gap size and shape, and less confined near a gap’s edges. I tested these ideas with a 3-year experiment in which I monitored the revegetation of gaps in grassland vegetation. Initially, species reproducing largely by clonal growth (bulbs and perennial graminoids) were the most sensitive to gap size and (to a lesser extent) shape, reaching their greatest abundances in small and/or rectangular openings. Species relying on seed dispersal (annual grasses) also tended to do best in smaller plots, but were less concentrated near plots’ edges. Species relying on seed dormancy (dicots and Juncus bufonius) were least sensitive to plot size, shape, and distance from an edge. In subsequent years, these patterns often were obscured or reversed, reflecting continuing seed immigration and environmental and competitive conditions within gaps. These results indicate that species respond to gap size and shape in ways consistent with their reproductive biologies, and suggest that the importance of gaps’ dimensions may vary among plant communities.Funding was provided by the Nature Conservancy of California, the University of California Natural Reserve System, an NSF Doctoral Dissertation Improvement Grant (DEB-9122821), an NSERC (Canada) PGS Fellowship, the Hardman Foundation, and the Department of Integrative Biology at U.C. Berkeley

A comparison of the growth responses of three sedges to foraging by lesser snow geese.

Masters Thesis completed in 1987 by P. M. Kotanen at the University of Toronto. Supervised by Dr. R.L. Jefferies.SUMMARY:1.The responses to herbivory of above-ground organs of the sedges Carex subspathaces and Carex X flavicans were investigated at La Pérouse Bay, Manitoba. Demographic techniques were used to compare the production and turnover of leaves and shoots and the elongation of leaves between plants of swards on which lesser snow Geese fed and plants of swards from which geese were excluded. The effects of herbivory on the shoot demography of carex aquatilis were also studied.2.Patterns of foraging by the geese varied seasonally. Following their arrival at La Pérouse Bay, the geese fed by pulling shoots of carices and by grubbing the roots and rhizomes of graminoids. After the hatch of the goslings, the geese fed by clipping the leaves of grasses and sedges.3.Within one summer, gazing increased the cumulative production of leaves of Carex subspathaceaand of Carex X flavcas. Though the geese removed few leaves, leaves of shoots of both species in grazed plots had shorter lifespans than leaves of shoots in ungrazed plots. Grazing also increased the total number of leaves per shoot which died during the growing season.4.The rates of elongation of leaves of shoots of Carex subspathacea and Carex X flavicans in grazed plots did not consistently differ from the rates of elongation of leaves of shoots in ungrazed plots.5.Herbivory by geese did not consistently alter the production of shoots of Carex aquatilis, Carex subspathacea, or Carex X flavicans.6.The increased production of leaves is the primary response of above-ground organs of these carices to herbivory by geese. The unresponsiveness of shoot production suggests that these carices are more vulnerable to damage from the loss of shoots than from the clipping of leaves

Responses of vegetation to a changing regime of disturbance: effects of feral pigs in a Californian coastal prairie

This is the accepted manuscript of an article published by Wiley. The manuscript does not include figures. To view figures, please consult the publisher's version of this article.Disturbance can eliminate sensitive native species and facilitate invasions by exotics, but disturbance is also important in the maintenance of many native-dominated ecosystems. Because of this dual role, disturbance can have complex implications for biodiversity. I have investigated the effects of an introduced agent of disturbance, the feral pig (Sus scrofa L.), in meadows in northern California. Pigs were the principal agent of soil disturbance at this site, annually overturning an average of 7.4% of the total surface area. Grubbed areas revegetated rapidly, but grubbing had significant effects on the composition of the affected vegetation. Species richness was reduced in grubbed plots in the first year following disturbance, but rose thereafter, often exceeding the richness of undisturbed controls. Disturbance did not exclusively benefit either native or exotic species. Changes in richness primarily reflected the early colonization of disturbed plots by natives, particularly annuals, although alien annual grasses also increased in disturbed sites. Consequently, though non-natives did respond positively to disturbance, at least in the short-term they did not simply replace natives. Pigs' effects may typify the complicated events to be expected when an ecosystem's regime of disturbance is significantly altered, either by direct human intervention or as a consequence of a biological invasion.Funding was provided by an NSF Doctoral Dissertation Improvement Grant (DEB-9122821), an NSERC Postgraduate Fellowship, the Nature Conservancy of California (CARO 042491-K), a Mildred E. Mathias Grant of the University of California Natural Reserve System, the Hardman Foundation, and the Department of Integrative Biology at U.C. Berkeley

Fates of added nitrogen in freshwater arctic wetlands grazed by Snow Geese: the role of mosses

This is the publisher's version of an article published by the University of Colorado at Boulder, Institute of Arctic and Alpine Research.Previous studies have shown that the growth of freshwater grasses and sedges eaten by breeding colonies of Snow Geese responds weakly to nitrogen additions, and also is poorly able to compensate within the same season for tissues lost to geese. These results contrast with the rapid responses to grazing and fertilization that have been observed in salt-marsh species. A possible explanation is that the mosses prominent in freshwater wetlands rapidly sequester added nitrogen, preventing access by forage species to the fecal inputs provided by foraging geese. To investigate this hypothesis, I added ecologically realistic amounts of ammonium and nitrate labelled with 15N to the surface and rooting zone of experimental plots in freshwater wetland vegetation at two Snow Goose colonies. Results indicate that the presence of mosses did not prevent forage species from rapidly taking up ammonium and nitrate added either at or below the moss surface. Nonetheless, most of the added 15N was absorbed by the moss layer; consequently, mosses tend to divert nitrogen away from forage species and into long-lasting peat. In the long term, this may reduce the ability of freshwater forage plants to recover from damage by increasing populations of Snow Geese.This is a collaborative publication of the Universite Laval Bylot Island Field Station and the Hudson Bay Project. NSERC, the Polar Continental Shelf Project, the University of Toronto, the Connaught Fund, the Hudson Bay Project, the FFCAR of the Quebec Government, and the Canadian Wildlife Service contributed financial support

Robert Jefferies with a baby Arctic Fox

Robert L. Jefferies with an Arctic fox cub, which was released unharmed

Researchers on the top of the McConnell esker

Researchers Robert Jefferies, Peter Kotanen, Dick Kerbes, Peter and Paul Mekiuniak, at the top of the esker of the McConnell River, which drains into the Hudson Bay at Kivalliq region in Nunavut territory

Effects of experimental soil disturbance on revegetation by natives and exotics in coastal Californian meadows

This is the accepted manuscript of an article published by Wiley.Disturbance is widely believed to facilitate invasions by exotic plants, but also is important for the persistence of many native species. Here, I report the results of a series of field experiments designed to investigate the effects of soil disturbance on natives and aliens in Californian grassland vegetation. I also compare the effects of different types of soil disturbance to establish whether some favour aliens to a greater degree than others. In two experiments, conducted at two different locations, three types of soil disturbance (excavation, burial, and simulated gopher mounds) were created, and their revegetation was compared with changes in undisturbed control plots over the next three years. A third experiment was used to provide data on the effects of soil disturbance on soil temperature, moisture, and KCl-extractable nitrogen. Disturbance affected both soil temperature and chemistry. Buried plots contained the most KCl-extractable nitrogen, and also were the warmest. Effects on soil moisture were relatively small. Initially, most disturbances greatly reduced the numerical abundance of both groups dominated by natives (perennial graminoids and bulbs) and those dominated by aliens (annual graminoids). Disturbance also reduced maximal (summer) species richness, but in some cases increased the fraction of richness contributed by natives. In subsequent years, richness rebounded as natives and exotics re-invaded. Native bulbs and perennial graminoids were slow to recover; instead, most disturbances increasingly became numerically dominated by exotic annual grasses, accentuating the effects of a multi-year drought. The differing effects of experimental disturbances on aliens and natives can best be explained by considering relationships between sources of propagules, life histories, and geographic origins. Some types of disturbance were less damaging to native-dominated groups than others, but most ultimately favoured exotics. Consequently, it may be difficult to develop management strategies that preserve the diversity of disturbance-dependent natives while still excluding weedy aliens.Funding was provided by the Nature Conservancy of California (CARO 042491-K), the University of California Natural Reserve System, an NSF Doctoral Dissertation Improvement Grant (DEB-9122821), a Postgraduate Fellowship of the Natural Sciences and Engineering Research Council of Canada, the Hardman Foundation, and the Department of Integrative Biology at U.C. Berkeley

Revegetation following soil disturbance in a California meadow: the role of propagule supply

This is the accepted manuscript of an article published by Springer Verlag. The manuscript does not include figures. To view figures, please consult the publisher's version of this article.Revegetation following a disturbance event initially should be constrained by the abundance and types of propagules available at the disturbed site. I tested this idea by conducting two experiments in which I created artificial soil disturbances by excavating or burying pre-existing grassland vegetation. In the first experiment, I varied disturbance intensity (depth), to investigate the consequences for revegetation when numbers of surviving propagules (dormant seeds and bulbs) were altered. In the second experiment, I varied the timing of disturbance, to investigate the consequences when disturbed sites experienced differing exposures to seasonal patterns of clonal growth and seed dispersal. I sampled these experiments from 1991 to 1993, and have interpreted their results using measurements of the seed bank, the bulb bank, and the seed rain. In the first (depth) experiment, bulbs declined in abundance with burial depth and were scarcer in deeper excavations. In contrast, numbers of annual graminoids initially showed no trends with respect to disturbance depth. These results reflect the depth distributions of the seed and bulb banks. Since bulbs occur deeply in the soil, progressively deeper disturbances left fewer survivors. Similarly, perennial graminoids could grow through only the shallowest burials. In contrast, since the annual graminoid dominated seed bank is concentrated near the soil surface, disturbance depth mattered less to these species: any disturbance removing the surface layer was equally destructive. In the second (timing) experiment, more annual graminoids initially occurred in older plots. This result reflects seasonal patterns of seed production: plots exposed to more of the annual graminoid dominated seed rain supported higher densities of annual graminoids as a result. In subsequent years, the vegetation of most plots in both experiments was increasingly dominated by annual graminoids, again as a consequence of their great abundance in the seed rain. These results indicate that interactions between soil disturbances and sources of propagules play an important role in controlling early stages of succession in newly-created gaps. They also suggest that disturbance may play different roles in communities characterized by species with different reproductive strategies. Understanding sources of colonists will improve our ability to predict the effects of disturbance.Funding was provided by the Nature Conservancy of California, the University of California Natural Reserve System, an NSF Doctoral Dissertation Improvement Grant (DEB-9122821), an NSERC (Canada) PGS Fellowship, the Hardman Foundation, and the Department of Integrative Biology at U.C. Berkeley