Temporal patterns of nutrient availability around nests of leaf-cutting ants (Atta colombica) in secondary moist tropical forest

Leaf-cutting ants consume up to 10% of canopy leaves in the foraging area of their colony and therefore represent a key perturbation in the nutrient cycle of tropical forests. We used a chronosequence of nest sites on Barro, Colorado Island, Panama, to assess the influence of leaf-cutting ants (Atta colombica) on nutrient availability in a neotropical rainforest. Twelve nest sites were sampled, including active nests, recently abandoned nests (<1 year) and long-abandoned nests (>1 year). Waste material discarded by the ants down-slope from the nests contained large concentrations of nitrogen and phosphorus in both total and soluble forms, but decomposed within one year after the nests were abandoned. Despite this, soil under the waste material contained high concentrations of nitrate and ammonium that persisted after the disappearance of the waste, although soluble phosphate returned to background concentrations within one year of nest abandonment. Fine roots were more abundant in soil under waste than control soils up to one year after nest abandonment, but were not significantly different for older sites. In contrast to the waste dumps, soil above the underground nest chambers consistently contained lower nutrient concentrations than control soils, although this was not statistically significant. We conclude that the 'islands of fertility' created by leaf-cutting ants provide a nutritional benefit to nearby plants for less than one year after nest abandonment in the moist tropical environment of Barro Colorado Island. Published by Elsevier Ltd.

An economic decision support tool for simulating paratuberculosis control strategies in a UK suckler beef herd

A dynamic, deterministic, economic simulation model was developed to estimate the costs and benefits of controlling Mycobacterium avium subsp. paratuberculosis (Johne's disease) in a suckler beef herd. The model is intended as a demonstration tool for veterinarians to use with farmers. The model design process involved user consultation and participation and the model is freely accessible on a dedicated website. The 'user-friendly' model interface allows the input of key assumptions and farm specific parameters enabling model simulations to be tailored to individual farm circumstances. The model simulates the effect of Johne's disease and various measures for its control in terms of herd prevalence and the shedding states of animals within the herd, the financial costs of the disease and of any control measures and the likely benefits of control of Johne's disease for the beef suckler herd over a 10-year period. The model thus helps to make more transparent the 'hidden costs' of Johne's in a herd and the likely benefits to be gained from controlling the disease. The control strategies considered within the model are 'no control', 'testing and culling of diagnosed animals', 'improving management measures' or a dual strategy of 'testing and culling in association with improving management measures'. An example 'run' of the model shows that the strategy 'improving management measures', which reduces infection routes during the early stages, results in a marked fall in herd prevalence and total costs. Testing and culling does little to reduce prevalence and does not reduce total costs over the 10-year period.

A tool for mapping research skills in undergraduate curricula

There has been considerable interest recently in the teaching of skills to undergraduate students. However, existing methods for collating data on how much, where and when students are taught and assessed skills have often been shown to be time-consuming and ineffective. Here, we outline an electronic research skills audit tool that has been developed to map both transferable and discipline-specific skills teaching and assessment within individual modules, the results of which can be collated and analysed across entire degree programmes. The design and use of the audit tool is described in detail and a bioscience case study is presented to illustrate the types of data that can be collected. The audit tool has been designed as a time-effective way of collecting information on skills teaching and assessment, but also actively encourages staff to reflect on their teaching and learning practices. Conclusions are drawn about the practicalities of using the audit tool and its importance in both curriculum design and as a resource to encourage dialogue with graduate employers.

Landscape typology in the Mediterranean context: a tool for habitat restoration

Despite the wide use of Landscape Character Assessment (LCA) as a tool for landscape planning in NW Europe, there are few examples of its application in the Mediterranean. This paper reports on the results from the development of a typology for LCA in a study area of northern Sardinia, Italy to provide a spatial framework for the analysis of current patterns of cork oak distribution and future restoration of this habitat. Landscape units were derived from a visual interpretation of map data stored within a GIS describing the physical and cultural characteristics of the study area. The units were subsequently grouped into Landscape Types according to the similarity of shared attributes using Two Way Indicator Species Analysis (TWINSPAN). The preliminary results showed that the methodology classified distinct Landscape Types but, based on field observations, there is a need for further refinement of the classification. The distribution and properties of two main cork oak habitats types was examined within the identified Landscape Types namely woodlands and wood pastures using Patch Analyst. The results show very clearly a correspondence between the distribution of cork oak pastures and cork oak woodland and landscape types. This forms the basis of the development of strategies for the maintenance, restoration and recreation of these habitat types within the study area, ultimately for the whole island of Sardinia. Future work is required to improve the landscape characterisation , particularly with respect to cultural factors, and to determine the validity of the landscape spatial framework for the analysis of cork oak distribution as part of a programme of habitat restoration and re-creation.

The effects of seed mix and management on the abundance of desirable and pernicious unsown species in arable buffer strip communities

Buffer strips are refuges for a variety of plants providing resources, such as pollen, nectar and seeds, for higher trophic levels, including invertebrates, mammals and birds. Margins can also harbour plant species that are potentially injurious to the adjacent arable crop (undesirable species). Sowing perennial species in non-cropped buffer strips can reduce weed incidence, but limits the abundance of annuals with the potential to support wider biodiversity (desirable species). We investigated the responses of unsown plant species present in buffer strips established with three different seed mixes managed annually with three contrasting management regimes (cutting, sward scarification and selective graminicide). Sward scarification had the strongest influence on the unsown desirable (e.g. Sonchus spp.) and unsown pernicious (e.g. Elytrigia repens) species, and was generally associated with higher cover values of these species. However, abundances of several desirable weed species, in particular Poa annua, were not promoted by scarification. The treatments of cutting and graminicide tended to have negative impacts on the unsown species, except for Cirsium vulgare, which increased with graminicide application. Differences in unsown species cover between seed mixes were minimal, although the grass-only mix was more susceptible to establishment by C. vulgare and Galium aparine than the two grass and forb mixes. Annual scarification can enable desirable annuals and sown perennials to co-exist, however, this practice can also promote pernicious species, and so is unlikely to be widely adopted as a management tool in its current form.