Mapping the spatio-temporal distribution of key vegetation cover properties in lowland river reaches,using digital photography

The presence of vegetation in stream ecosystems is highly dynamic in both space and time. A digital photography technique is developed to map aquatic vegetation cover at species level, which has a very high spatial and a flexible temporal resolution. A digital single-lens reflex (DSLR) camera mounted on a handheld telescopic pole is used. The low-altitude (5 m) orthogonal aerial images have a low spectral resolution (red-green-blue), high spatial resolution (～1.9 pixels cm^?2, ～1.3 cm length) and flexible temporal resolution (monthly). The method is successfully applied in two lowland rivers to quantify four key properties of vegetated rivers: vegetation cover, patch size distribution, biomass and hydraulic resistance. The main advantages are that the method is (i) suitable for continuous and discontinuous vegetation covers, (ii) of very high spatial and flexible temporal resolution, (iii) relatively fast compared to conventional ground survey methods, (iv) non-destructive and (v) relatively cheap and easy to use, and (vi) the software is widely available and similar open source alternatives exist. The study area should be less than 10 m wide, and the prevailing light conditions and water turbidity levels should be sufficient to look into the water. Further improvements of the image processing are expected in the automatic delineation and classification of the vegetation patches.     

Community gardening and social cohesion: different designs,different motivations

Community gardens vary in several ways: they are cultivated by different kinds of communities in various locations, entail individual or communal plots and the extent of active participation (e.g. gardening) differs. In this paper, we study seven community gardens with varying organisational designs and objectives, and investigate the extent to which these influence the enhancement of social cohesion. We also take into account to what extent differences in motivation among community gardeners matter. Despite these differences in motivation, however, we find that in all of the cases studied, people talk to and get to know others, and mutual help is widespread. We, therefore, conclude that community gardens contribute to the development of social cohesion – even if people are not particularly driven by social motivations. Moreover, while participants who are motivated by the social aspects of gardening naturally show a higher level of appreciation for them, these social aspects also bring added value for those participants who are motivated primarily by growing vegetables.     

Adaptive superparasitism and patch time allocation in solitary parasitoids : the influence of pre-patch experience

Summary Dynamic optimal diet models predict that host selection decisions and patch time allocation are influenced by the resource value of the habitat. We tested these predictions using the solitary' parasitoid Leptopilina heterotoma. Assuming that travel times between patches, the quality of previously visited patches and parasitoid density affect the parasitoids' estimation of the resource value of the habitat, different treatments were given before introducing parasitoids singly to a patch containing 5 unparasitized and 15 parasitized hosts. The decision to superparasitize is only slightly influenced by the rate of patch encounter. The quality of the previously visited patch has a strong influence. When a poor patch has been visited on the previous day, more superparasitism is observed in the partly depleted patch than when a rich patch has been searched. More superparasitism is also observed when the parasitoids are kept with conspecifics before the experiment than when they are kept alone. Increasing patch residence times are observed as the quality of the previously presented patch decreases. Host selection decisions and patch time allocation are thus clearly influenced by the pre-patch experience of the parasitoid, as predicted by dynamic optimal diet models. This can also explain why females that have never oviposited in unparasitized hosts will superparasitize readily. Correspondence to: M.E. Visser     

Dynamis CO2 quality recommendations

In the carbon capture and storage (CCS) chain, transport and storage set different requirements for the composition of the gas stream mainly containing carbon dioxide (CO₂). Currently, there is a lack of standards to define the required quality for CO₂ pipelines. This study investigates and recommends likely maximum allowable concentrations of impurities in the CO₂ for safe transportation in pipelines. The focus is on CO₂ streams from pre-combustion processes. Among the issues addressed are safety and toxicity limits, compression work, hydrate formation, corrosion and free water formation, including the cross-effect of H₂S and H₂O and of H₂O and CH₄.     

Consequences of resource competition for sex allocation and discriminative behaviors in a hyperparasitoid wasp

Population-wide mating patterns can select for equal parental investment in both sexes, but limiting resources, such as mates or developmental substrates, can increase competition leading to biased sex ratios in favor of either sex. Such competition for resources typically occurs in spatially structured populations, where dispersal is limited. In this laboratory study, we investigate if and how resource competition affects sex allocation, discriminative behaviors and competitive interactions of the wingless hyperparasitoid Gelis acororum, which exploits patchily distributed hosts. We show that G. acororum sex ratios are male-biased and that this is not a consequence of constrained reproduction by virgin females. Our results suggest that this pattern of reproductive investment, which is only rarely observed in parasitoids, is a consequence of resource limitation, in terms of hosts rather than mates. Further, G. acororum appears not to respond to intrinsic host quality or to prior oviposition in its host. When competing inter-specifically for host resources, G. acororum outcompetes its congener Gelis agilis, but does so mainly when ovipositing on the host first. Overall, our results suggest that host resource limitation could be an important environmental factor shaping sex allocation in G. acororum, with competition taking place both intra- and inter-specifically.     

Assessing the market opportunities of landfill mining

Long-term estimates make clear that the amount of solid waste to be processed at landfills in the Netherlands will sharply decline in coming years. Major reasons can be found in the availability of improved technologies for waste recycling and government regulations aiming at waste reduction. Consequently, market size for companies operating landfills shrinks. Among the companies facing the problem is the Dutch company Essent. Given the expected market conditions, it looks for alternative business opportunities. Landfill mining, i.e., the recycling of existing landfills, is considered one of them. Proceeds of landfill mining are related to, for example, recycled materials available for re-use, regained land, and possibilities for a more efficient operation of a landfill. The market for landfill mining is of a considerable size--there are about 3800 landfills located in the Netherlands. Given market size the company faces the dilemma of how to explore this market, i.e., select the most profitable landfills in a fast and efficient way. No existing methods or tools could be found to do so. Therefore, to answer to the problem posed, we propose a step-wise research method for market exploration. The basic idea behind the method is to provide an adequate, cost-saving and timely answer by relying on a series of quick scans. Relevant aspects of a mining project concern the proceeds of regained land and recyclables, the costs of the mining operation and the associated business and environmental risks. The method has been tested for its practical use in a pilot study. The pilot study addressed 147 landfills located in the Dutch Province of Noord-Brabant. The study made clear how method application resulted in the selection of a limited number of high potential landfills in a few weeks, involving minimal research costs.     

Evolutionary constraints in the mechanism of flavin catalysis

Analysis of the possible evolution of flavin catalysis in succinate dehydrogenase suggests as the ultimate stage an active site that bears one or more acid functions and uses the enediol form of the substrate rather than the carbanion as a nucleophile. In the case of flavoenzyme catalyzed oxidation of fatty acylCoA, α-amino acids and α-hydroxy acids evolution to a similar mechanism seems to be blocked.     

Biomass energy experiments in rural India: Insights from learning-based development approaches and lessons for Strategic Niche Management

This paper investigates the suitability and limitations of the Strategic Niche Management framework in the context of emerging economies of South and East Asia. We explore several learning-based approaches to development projects that are part of the academic and practitioner field of development studies. The approaches show similarities with SNM but they reflect the developing-country context within which they were framed, and are also more geared towards local community development and capacity building. We apply these approaches to four biomass energy projects in rural India to identify determinants of success and failure. We then discuss how these findings compare with the insights that an SNM analysis would have offered. We arrive at the following conclusions. First, the great strengths of SNM are its explicit conceptualisation of environmental sustainability and its endogenous treatment of the larger context. Second, the learning-based development approaches hone in on the complexities of local management and stakeholder organisation. Third, they also bring out the great importance of local institutions such as traditional status and power differences. Fourth, we conclude that SNM holds considerable promise for application in a developing Asian context, but that its usefulness and relevance in that setting could be enhanced by incorporating these additional issues.