Dung exploitation by the dung beetle Typhaeus typhoeus (Col., Geotrupidae).

This paper deals with the functional aspects of the exploitation of dung by the dung beetle Typhaeus typhoeus. In horizontal brood chambers of a nest in the soil these beetles make "dung sausages" chiefly from rabbit droppings, as a food source for the larvae. Their foraging behaviour was shown to be positively correlated with the occurrence of rainy periods. The beetles foraged more efficiently on clustered dung pellets than on dispersed ones. Body sizes of beetles were positively correlated with the lengths of the dung sausages from which they emerged. In laboratory experiments the lengths of the dung sausages made by a pair of beetles did not significantly differ within a wide range of frequencies of supply of various amounts of rabbit dung pellets, despite the longer time spent per dung sausage when less dung was supplied per unit of time. It is suggested that dung provisioning does not stop before the dung sausages have reached lengths (approximately 8.5-9.5 cm) anticipated by the lengths of the brood chambers. However, there appeared to be a critically low value between 1-2 and 4-5 dung pellets supplied per day, below which the finished dung sausages were significantly shorter (approximately 3.5 cm).When, at the places of settlement, dung was scarce near the nest entrances, the number of nest excavated by the beetles and, thus, the beetles' physical effect on the soil, was shown to be higher than when dung was plentiful near the nest.The ecological and evolutionary consequences of the foraging behaviour by the beetles are discussed.

One-dimensional scattering in K-hollandite: theory and experiment.

This work comprises calculations using the Frenkel-Kontorova and double-chain models, which led to new results explaining the experimental diffraction pattern of K-hollandite. The use of a deformable host chain and a Lennard-Jones-like interchain interaction gives the best results. From these calculations, it can also be concluded that the guest as well as the host are deformed and that the system is pinned. The inclusion of Debye-Waller factors as fitting parameters is also discussed, with the conclusion they should not be used in the case of the double-chain model.

A method to assess ecosystem services developed from soil attributes with stakeholders and data of four arable farms.

Ecosystem-service indicators and related accounting units are crucial for the development of decision frameworks for sustainable land management systems. With a management concept using ecosystem services, land-use expectations can be linked to quantifiable soil features in a defendable and transparent way. A method to define a set of site-specific ecosystem services and indication system for quantification was set-up and run. First, we interviewed a wide group of land users profiting from ecosystem services of the soil at four arable farms in the polder Hoeksche Waard (S-SE of Rotterdam, the Netherlands). Subsequently, site-specific ecosystem services were defined and weighted according to land use expectations at different spatial and temporal scales. Second, a practical set of indicators was taken from 'Best Professional Judgment' and used to quantify the performance of the ecosystem services for these four farms. The indicators were derived from biotic and abiotic soil parameters. The performance of ecosystem services was related to a reference situation (MEP: maximum ecological potential) with the same land use and soil type combination (i.e., arable fields on silt loam) taken from the database of our national soil survey. In many cases, the performance of ecosystem services was relatively poor if compared to MEP. However, the performances of natural attenuation and/or climate-related services were better. In addition, the different management of these farms (i.e. conventional, intensive and organic farming) was reflected in the performance of the ecosystem services of their soils. Third, land management measures to improve the targeted ecosystem services were incorporated in the outlined method, but not worked out with illustrative field data in this study. Together with concordant data, we show opportunities for a quantification of ecosystem services to improve land-users' awareness and to assess management sustainability.

Within-trophic group interactions of bacterivorous nematode species and their effects on the bacterial community and nitrogen mineralization.

Knowledge of the interactions between organisms within trophic groups is important for an understanding of the role of biodiversity in ecosystem functioning. We hypothesised that interactions between bacterivorous nematodes of different life history strategies would affect nematode population development, bacterial community composition and activity, resulting in increased N mineralization. A microcosm experiment was conducted using three nematode species (Bursilla monhystera, Acrobeloides nanus and Plectus parvus). All the nematode species interacted with each other, but the nature and effects of these interactions depended on the specific species combination. The interaction between B. monhystera and A. nanus was asymmetrically competitive (0,-), whereas that between B. monhystera and P. parvus, and also A. nanus and P. parvus was contramensal (+, -). The interaction that affected microcosm properties the most was the interaction between B. monhystera and P. parvus. This interaction affected the bacterial community composition, increased the bacterial biomass and increased soil N mineralization. B. monhystera and P. parvus have the most different life history strategies, whereas A. nanus has a life history strategy intermediate to those of B. monhystera and P. parvus. We suggest that the difference in life history strategies between species of the same trophic group is of importance for their communal effect on soil ecosystem processes. Our results support the idiosyncrasy hypothesis on the role of biodiversity in ecosystem functioning.

Field research for the authorisation of pesticides.

On request of the Dutch government a committee of the Health Council of the Netherlands has reviewed the role that results of field research in its broadest sense (i.e., including multi-species toxicity tests in the laboratory, research on model ecosystems et cetera) can play in ecotoxicological risk assessment for the authorisation of pesticides. The Committee believes that field research can provide valuable additional data about the exposure of non-target organisms and the resultant effects at population, community and ecosystem level. However, it frequently is unclear how these data might be used in reaching a decision about authorisation. To solve this problem, it is necessary to specify what is understood by "unacceptable damage". Both more clearly formulated protection goals of the government and a better understanding of the ecological significance of effects are needed to clarify this. Furthermore, the Committee points out that the statistical power of field trials must be sufficient to allow for the detection of changes that might be regarded as ecologically relevant. Finally, it recommends keeping a finger on the pulse in relation to authorised pesticides by monitoring their presence in environmental compartments and by investigating their role in suddenly occurring mortality among conspicuous animal species, such as birds, fish and honeybees. This kind of research forms a safety net for substances that have been wrongly authorised.