From plant neighbourhood to landscape scales: how grazing modifies native and exotic plant species richness in grassland

The interactive effect of grazing and soil resources on plant species richness and coexistence has been predicted to vary across spatial scales. When resources are not limiting, grazing should reduce competitive effects and increase colonisation and richness at fine scales. However, at broad scales richness is predicted to decline due to loss of grazing intolerant species. We examined these hypotheses in grasslands of southern Australia that varied in resources and ungulate grazing intensity since farming commenced 170 years ago. Fine-scale species richness was slightly greater in more intensively grazed upper slope sites with high nutrients but low water supply compared to those that were moderately grazed, largely due to a greater abundance of exotic species. At broader scales, exotic species richness declined with increasing grazing intensity whether nutrients or water supply were low or high. Native species richness declined at all scales in response to increasing grazing intensity and greater resource supply. Grazing also reduced fine-scale heterogeneity in native species richness and although exotics were also characterised by greater heterogeneity at fine scales, grazing effects varied across scales. In these grasslands patterns of plant species richness did not match predictions at all scales and this is likely to be due to differing responses of native and exotic species and their relative abundance in the regional species pool. Over the past 170 years intolerant native species have been eliminated from areas that are continually and heavily grazed, whereas transient, light grazing increases richness of both exotics and natives. The results support the observation that the processes and scales at which they operate differ between coevolved ungulate—grassland systems and those in transition due to recent invasion of herbivores and associated plant species.     

NEKTAR,SPICE and Vortonics: using federated grids for large scale scientific applications

In response to a joint call from US’s NSF and UK’s EPSRC for applications that aim to utilize the combined computational resources of the US and UK, three computational science groups from UCL, Tufts and Brown Universities teamed up with a middleware team from NIU/Argonne to meet the challenge. Although the groups had three distinct codes and aims, the projects had the underlying common feature that they were comprised of large-scale distributed applications which required high-end networking and advanced middleware in order to be effectively deployed. For example, cross-site runs were found to be a very effective strategy to overcome the limitations of a single resource. The seamless federation of a grid-of-grids remains difficult. Even if interoperability at the middleware and software stack levels were to exist, it would not guarantee that the federated grids can be utilized for large scale distributed applications. There are important additional requirements for example, compatible and consistent usage policy, automated advanced reservations and most important of all co-scheduling. This paper outlines the scientific motivation and describes why distributed resources are critical for all three projects. It documents the challenges encountered in using a grid-of-grids and some of the solutions devised in response.     

Evaluation of Blast Furnace Slag as a Means of Reducing Metal Availability in a Contaminated Sediment for Beneficial Use Purposes

An attractive option for the management of dredged sediment involves the use of dredged sediment for beneficial use purposes, such as for fill material. Treatment (chemical amendment) of contaminated sediment may be necessary to limit the environmental and human availability (bioaccessibility, leachability, plant uptake) of heavy metals associated with the contaminated sediment before it is placed. A laboratory study was conducted to investigate the effect of admixing a specific chemical amendment (blast furnace slag) with slightly contaminated fresh-water sediment for reducing metal availability. Initial characterization tests of the un-amended sediment showed that the some of the metals analyzed were present in relatively available (non-residual) forms. Although sulfide was present in the un-amended sediment, the amount was not sufficient to bind all of the available metals. A series of metal availability testing methods indicated that the amendment of the sediment with blast furnace slag (4% on a dry weight ratio basis) had the potential to slightly reduce the availability of some, but not all of the available metals associated with the sediment. Results of the column and batch leaching tests showed that leachability of certain metals, such as barium, nickel and zinc, was reduced by the amendment, but the leachability of copper increased. The effect of the amendment for decreasing bioaccessibility for lead and arsenic was not demonstrated. The amended soil had a detrimental effect on most of the plant species that were evaluated. The metal availability results for the plant uptake tests were also mixed, with slightly lower uptake of certain metals by corn grown within the amended sediment.     

Proteomic analyses of a robust versus a poor chicken gastrointestinal colonizing isolate of Campylobacter jejuni

Campylobacter spp. are a significant contributor to the bacterial etiology of acute gastroenteritis in humans. Epidemiological evidence implicates poultry as a major source of the organism for human illness. However, the factors involved in colonization of poultry with Campylobacter spp. remain unclear. Determining colonization-associated factors at the proteome level should facilitate our understanding of Campylobacter spp. contamination of poultry. Therefore, proteomic analyses were utilized to identify expression differences between two Campylobacter jejuni isolates, a robust colonizer A74/C and a poor colonizing strain of the chicken gastrointestinal system designated NCTC 11168-PMSRU. Proteomic analyses by two-dimensional gel electrophoresis revealed the specific expression of an outer membrane-fibronectin binding protein, serine protease, and a putative aminopeptidase in the soluble portion of the robust colonizer A74C. Several proteins including a cysteine synthase and aconitate hydratase were detected specifically in the poor colonizer C. jejuni NCTC 11168-PMSRU isolate. Variation in the amino acid sequences resulting in different isoelectric points and relative mobility of the flagellin and C. jejuni major outer membrane (MOMP) protein were also detected between the two isolates. Western blotting of the bacterial proteins revealed the presence of two flagellin proteins in the poor colonizer versus one in the robust colonizing isolate, but no differences in MOMP. The results demonstrated that proteomics is useful for characterizing phenotypic variation among Campylobacter spp. isolates. Interestingly, different gene products potentially involved in robust colonization of chickens by Campylobacter spp. appear to conform to recently identified expression patterns in Biofilm or agar-adapted isolates.     

Patterns and predictors of condition indices in a critically endangered fish

Hydrobiologia - Condition indices are key predictors of health and fitness in wild fish populations. Variation in body condition, therefore, can be used to identify stressful conditions that may...