Organic residue decomposition: The minicontainer-system a multifunctional tool in decomposition studies

The Minicontainer-test, first described by Eisenbeis (1993), was designed to study the kinetics of organic residue decomposition at a microsite level. It is derived from the litterbag technique and consists of polyethylene minicontainers (volume about 1.5 cm³) filled with a test substrate (litter, straw, cellulose, etc.). The minicontainers (MCs) are closed at either end with plastic gauze discs of variable mesh size (e.g. 20 μm, 250 μm, 500 μm or 2 mm). A definite number of such units are inserted into PVC-bars, which can be implanted into the soil horizontally or vertically, or be exposed on the soil surface horizontally. The bars are very stable and can be exposed in different environments for months to years. If required, the bars can be removed temporarily and stored, e.g. during soil cultivation. Should fresh litter be used, two phases of decomposition can be distinguished: a fast initial phase, which can be mainly related to the effect of leaching, and a second slow phase depending mainly on the activity of soil organisms and litter quality. Several questions can be addressed to investigations using MCs, e.g. 1) parts of the soil fauna which are involved in decomposition (nematodes, microarthropods, and smaller specimens of the macrofauna, e.g. enchytraeidae, diplopods and dipteran larvae) can be extracted from the litter substrate using a miniscale high gradient extractor, 2) the organic mass loss of litter can be determined, 3) microbial biomass (C_mic, N_mic) can be assessed by fumigation extraction and 4) microbial activity (respiration) in the test substrate can also be assessed by use of standardised methods. Compared to litterbag studies, the larger number of small replicate units improves the statistical evaluation. Until today the Minicontainer-test has been applied in forestry and agriculture, e.g. studying the effects of liming, soil restoration and the application of insecticides, e.g. Diflubenzuron (Dimilin) and Btk (Bacillus thuringiensis var.kurstaki).     

Confronting Management Challenges in Highly Uncertain Natural Resource Systems: a Robustness–Vulnerability Trade-off Approach

This paper presents a framework for the study of policy implementation in highly uncertain natural resource systems in which uncertainty cannot be characterized by probability distributions. We apply the framework to parametric uncertainty in the traditional Gordon–Schaefer model of a fishery to illustrate how performance can be sacrificed (traded-off) for reduced sensitivity and hence increased robustness, with respect to model parameter uncertainty. With sufficient data, our robustness–vulnerability analysis provides tools to discuss policy options. When less data are available, it can be used to inform the early stages of a learning process. Several key insights emerge from this analysis: (1) the classic optimal control policy can be very sensitive to parametric uncertainty, (2) even mild robustness properties are difficult to achieve for the simple Gordon–Schaefer model, and (3) achieving increased robustness with respect to some parameters (e.g., biological parameters) necessarily results in increased sensitivity (decreased robustness) with respect to other parameters (e.g., economic parameters). We thus illustrate fundamental robustness–vulnerability trade-offs and the limits to robust natural resource management. Finally, we use the framework to explore the effects of infrequent sampling and delays on policy performance.     

Challenges of simulating complex environmental systems at the landscape scale: A controversial dialogue between two cups of espresso

With the advancement of computational systems and the development of model integration concepts, complexity of environmental model systems increased. In contrast to that, theory and knowledge about > environmental systems as well as the capability for environmental systems analyses remained, to a large extent, unchanged. As a consequence, model conceptualization, data gathering, and validation, have faced new challenges that hardly can be tackled by modellers alone. In this discourse-like review, we argue that modelling with reliable simulations of human-environmental interactions necessitate linking modelling and simulation research much stronger to science fields such as landscape ecology, community ecology, eco-hydrology, etc. It thus becomes more and more important to identify the adequate degree of complexity in environmental models (which is not only a technical or methodological question), to ensure data availability, and to test model performance. Even equally important, providing problem specific answers to environmental problems using simulation tools requires addressing end-user and stakeholder requirements during early stages of problem development. In doing so, we avoid modelling and simulation as an end of its own.     

Determination of 10 particle-associated multiclass polar and semi-polar pesticides from small streams using accelerated solvent extraction

A new analytical method using accelerated solvent extraction was developed for the determination of 10 particle-associated polar and semipolar pesticides. In addition, six deuterated analogues of the target compounds were evaluated as internal standards. The method yielded acceptable accuracy (73–103% recovery) and precision (<25% relative standard deviation) for eight compounds. Using size exclusion chromatography (SEC) as cleanup step resulted in higher recoveries compared to solid phase extraction (SPE) cleanup.

Deuterated standards with 10 or more deuterium atoms performed well as internal standards concerning similar recovery and correlation with the target analytes.

The method was employed to extract particle-associated pesticides from 16 streams located in an area with intense agriculture in France. Acetochlor, pirimicarb, tebuconazole, fenpropidin, -endosulfan and chlorfenvinphos were detected at concentrations up to 1 mg kg⁻¹ dry weight. A comparison with aquatic toxicity data indicated potential risk to the benthic fauna exposed to these concentrations of pirimicarb, -endosulfan and chlorfenvinphos.

We suggest that the method presented here be used for the extraction and quantitation of particle-associated polar pesticides.     

Impacts on industry of Europe's emerging chemicals policy REACh

For Europe, a new regime in chemicals regulation is about to start. After the proposal of the European Commission concerning the Registration, Evaluation and Authorization of Chemicals (REACh) passed its readings in the European Parliament and some differences with the European Council of Ministers were resolved, the regulation will come into force in June 2007. This paper is focused on the question how serious the cost burdens for industry induced by REACh will be, and whether the New European Member States (NMS) which joined the European Union in May 2004 will be able to cope with the regulation. This evaluation has been done by assessing the legislative, administrative and economic framework in New Member States and by analysing real business cases in companies. The empirical showcase business impact studies are at the same time of interest for companies of EU-15 states, other European countries who may implement the regulation, and even for exporters of raw materials and chemicals outside Europe, who will also have to comply with REACh if they market in the European Community. The results give no indications that REACh adoption will bring significant drawbacks to companies in the NMS. The emerging regulation will bring challenges for individual companies, especially for small and medium-sized ones, but for the European chemical industry as a whole, there is no question that it will be able to cope with REACh burdens without losing its global competitiveness.     

Discrimination of different social companions in spectacled parrotlets (Forpus conspicillatus): evidence for individual vocal recognition

Individual recognition is generally assumed to be a prerequisite for establishing and maintaining a complex social system. Indeed, there is good evidence that highly social species have complex systems of vocal communication with individual recognition by acoustic cues. In this study, we provide experimental evidence that vocal class and individual recognition is present in a non-passerine bird, the spectacled parrotlet (Forpus conspicillatus). Spectacled parrotlets live in a complex system of social relationships. Soon after fledging, the young establish close sibling relationships which are important for successful socialization, pairing and reproduction. In a series of playback experiments we tested if spectacled parrotlets use contact calls for vocal recognition. The results showed that spectacled parrotlets discriminate between the contact calls of different social categories. Adult birds preferred to respond to the contact calls of their mates. Subadult individuals recognized the contact calls of their siblings. During the period of pair bond formation, the affiliative contacts to the siblings decrease, but the parrotlets continue to respond to the calls of their siblings. This is the first evidence that vocal sibling recognition might outlast the period of strong sibling interaction and extends into the period of pair bond formation. In cases of mate loss or divorce, the acoustic contact to their siblings might facilitate the re-establishment of close sibling relationships. Received: 29 October 1997 / Accepted after revision: 5 April 1998     

Effect of vegetation type on throughfall deposition and seepage flux

This paper compares different vegetation types (coniferous and deciduous forest, grassed and pure heathland) in terms of input (throughfall deposition) and output (seepage flux) in a region with intermediate nitrogen load (+/-20kg Nha(-1)y(-1) via bulk precipitation) in comparable conditions in north Belgium. Coniferous forest (two plots Pinus sylvestris and two plots Pinus nigra) received significantly higher nitrogen and sulphur throughfall deposition than deciduous forest and heathland. Grassed and pure heathland had significantly highest throughfall quantities of Ca(2+) and Mg(2+), respectively. The observed differences in throughfall deposition between the different vegetation types were not univocally reflected in the ion seepage flux. Considerable seepage fluxes of NO(3)(-), SO(4)(2-), Ca(2+) and Al(III) were only found under the P. nigra plots. We discuss our hypothesis that the P. nigra forests already evolved to a situation of N saturation, while the other vegetation types did not.     

Effects of soil properties, mulch and NPK fertilizer on maize yields and nutrient budgets on ferralitic soils in southern Benin

Four on-farm experiments examined whether modest applications of fertilizers in combination with prunings from native agroforestry trees would be an alternative to maintain the fertility of ferralitic soils in Benin. An application of about 1.9 t ha⁻¹ dry matter of mulch of Senna siamea combined with 30 kg N ha⁻¹, 22 kg P ha⁻¹ and 25 kg K ha⁻¹ as compound fertilizer was compared with (1) 60 kg N ha⁻¹, 43 kg P ha⁻¹ and 50 kg K ha⁻¹ as compound fertilizer alone, (2) mulch of S. siamea alone (about 3.2 t ha⁻¹ dry matter), and (3) a control treatment. Criteria were soil properties, yields, nutrient uptakes, and nutrient budgets. Application of sole mulch had no significant effects (P>0.05) on maize yields, while combined application of prunings and NPK fertilizers or sole NPK increased yields significantly (P<0.05). The most limiting nutrient was P. The local maize cultivar was efficient in P uptake, but not in internal nutrient utilization efficiency; mulch increased significantly the internal P utilization efficiency (P<0.05). Soil properties were interpreted with the QUEFTS (quantitative evaluation of the fertility of tropical soils) computer program. The predicted and measured yields were almost the same for maize without NPK. The measured responses to NPK were much lower than the responses calculated by QUEFTS. The calculated nutrient budgets were split into balances for available nutrients and for those not immediately available (NIA). Nutrient budgets were negative for the control and sole mulch treatments, and positive for the NPK treatments. Mulch improved the balances of NIA nutrients. The present experiment could not prove that combining NPK with mulch is the best option for sustainable agriculture. It may be more economical to apply lower rates of fertilizer to local maize than those applied in the two NPK treatments in the present study.     

Termite assemblages in a West-African semi-deciduous forest and teak plantations

Responses of termite assemblages to the conversion of semi-deciduous forest into teak plantations were studied in the Lama Forest Reserve in Benin, West Africa. Four belt transect surveys were run in each of the two forest types, adopting a modified termite diversity assessment protocol. Termite assemblages were remarkably species-poor in both forest types, with only 19 species encountered altogether. The low species richness was due to the rarity of soil-feeders of the soil/humus interface and the absence of true soil-feeders in the compact vertisol soil. Species richness was significantly higher in semi-deciduous forest than in teak plantations, but termite encounters were significantly lower. Termite assemblage and feeding group structure differed significantly among forest types. Wood-feeders were recorded only in semi-deciduous forest. In contrast, fungus-growers were more species-rich and about four times more abundant in teak plantations, mainly due to one Ancistrotermes species. The humification score, which depicts the position of termite assemblages along a gradient of increasing humification of their food substrate, was significantly higher in teak plantations, due to the absence of wood-feeders and the preponderance of fungus-growers. Combined principal components and multiple regression analysis identified two significant predictors of termite assemblages, soil water content and leaf litter biomass. The abundance of fungus-growers in teak plantations seemed to be mainly related to the high leaf litter biomass. Indirect evidence also suggests that lower predation pressure by ants on termites in teak plantations may have contributed to the abundance of termites.