Organism-substrate relationships in lowland streams

A field and laboratory study on the microdistribution of bottom dwelling macroinvertebrates to investigate the role of the stream substrate In the development and preservation of the macroinvertebrate communities in natural, undisturbed lowland streams is described. Field data on bottom substrates and fauna wore collected between 1975 and 1978 from two Dutch lowland streams. Substrates were characterized by the nature and the amount of organic detritus and the mineral particle sizes: in a field classification on the basis of the visually dominant particle sizes; in a grain-size classification on the basis of exact particle-size analysis in the laboratory. Substrate preference for 84 macroinvertebrate species was demonstrated using the Index of Representation.Substrate-selection experiments were conducted in a laboratory stream for three Trichoptera species (Micropterna sequax, Chaetopteryx Villosa and Sericostoma personatum) and one Ephemeroptera species (Ephemera danica). An experiment on the colonization of artificial substrates in the field was also conducted.Prom the field data, several faunal groups could be distinguished, each group made up of species with similar substrate preferences. Detailed data on the microdistribution in relation to substrate particle size are given for 26 species, which represent the various taxonomical units that compose the faunal groups: Trichoptera (5 species), Ephemeroptera (1 species), Plecoptera (1 species), Coleoptera (3 species), Amphipoda (1 species), Diptera (15 species, among which 13 species of Chironomidae). The microdistribution is discussed in relation to case-building behaviour, life cycle and food preferences. For several species substrate preferences may be different for different development stages or in different seasons.It is concluded that most species show distinct preferences for a specific substrate. The small scale spatial variation in substrate composition of the stream bed is essential for the existence of many lowland stream macroinvertebrate species

Understanding acts of creativity:an Examination of the Creative Process through three different conceptual lenses

To stay competitive, organizations must utilize employees’ creative output. A minimum requirement is that employees actually engage in a creative process involving specific creative activities. Although this creative process is critical for producing creative output, scientific understanding of it is still limited. In this dissertation, we examined when people engage in (what type of) creative processes, in what order, and what the consequences are for creative output.Firstly, we examined the relation between work effort and creative process engagement. We found that creative process engagement takes energy, and that a lack of energy makes engaging in the creative process less attractive for employees. Secondly, we examined whether specific creative-process activities (defining problems, searching information, and generating ideas) need different motivators, and have different effects on creative output. We found that job autonomy especially motivated employees to define problems and search for information. In contrast, employees who felt their leaders expected them to be creative were especially motivated to generate ideas. Furthermore, we found that generating ideas is important for both radical and incremental creative output, but that radical creativity additionally requires employees to define problems. Thirdly, we wanted to understand whether being creative requires the various activities to follow each-other in an ordered way, or in a more dynamic and iterative way. Therefore, we examined the creative process over the course of a creative task. We found that a more dynamic creative process was associated with creative products that were more novel

Toward a new theory of feed intake regulation in ruminants

Part I of this thesis contains a critical appraisal of the commonly accepted theory with regard to feed intake regulation in ruminants and the presentation of a new theory. This new theory assumes that feed consumption creates both benefits to the animal (in a non-reproducing animal the intake of net energy for maintenance and gain) and costs (the total oxygen consumption of the animal). It is hypothesized that, for the animal, the intake level where the ratio between benefits and costs becomes maximal, is optimal. Predictions of this optimum level for a wide range of feeds are shown to agree closely with observed voluntary feed intake in non-reproducing ruminants. Physiological processes related to the concept of an optimum feed intake are discussed. Maintenance of intracellular pH and associated energy costs may appear to be key factors in view of increases of the metabolic acid load consequent upon changes in intake. It is concluded that the concepts developed here may reflect a more universal principle governing the intensity of different forms of behaviour in ruminants as well as in monogastric animals.Part II reports results of a long-term feeding experiment with small West African Dwarf goats and a larger sheep breed given pelleted roughage. Between species, intake of digestible organic matter and fasting heat production appeared to vary as a function of metabolic weight.The effect of nutrient supplements on intake of low to medium quality roughages was investigated in supplementation and infusion experiments with the same species. Nutritive substances tested were by-pass protein, rumen microbial material, grass juice, intestinally digestible carbohydrates, and volatile fatty acid mixtures. Nutrient supplements usually depressed roughage intake but increased estimated intake of metabolizable energy (ME). From the theory presented in Part I it is inferred that such changes of intake are the result of changes of the efficiency of ME utilization

De invloed van structuurdunning en noodverjonging op de effectieve depositie in bossen; een literatuurstudie

Dit rapport doet verslag van een deelonderzoek uit de Evaluatie van effectgerichte maatregelen in multifunctionele bossen 2004-2005 en is gericht op de effecten de maatregelen Aanpassen van de bosvegetatie als overbruggingsmaatregel in het kader van het Overlevingsplan Bos en Natuur (OBN). Structuurdunning (groepenkap) en noodverjonging (omvorming) hebben via beïnvloeding van de ruwheid van de kroonlaag van het bos in principe een effect op de depositie van verzurende en vermestende stoffen in het bos. De maatregelen worden kort omschreven. Doel van dit deelrapport is om de effecten van de beide maatregelen op de depositie in te schatten via literatuurstudie. Het niveau van depositie is hoger in bosranden en mede afhankelijk van de lengte en type begroeiing van het gebied vóór het bos. Door filtering in de bosrand slaat er verderop minder depositie neer. Er zijn vele literatuurbronnen die deze effecten beschrijven en kwantificeren voor specifieke situaties. Een algemeen beeld voor de netto effecten op de depositie is daarvan moeilijk af te leiden door de vele tijdgebonden en kleinschalige effecten. Voor de depositie hebben de beide maatregelen dus waarschijnlijk geen netto effect. Bovendien is het effect van structuurdunning en noodverjonging op de ruwheid van het kronendak in principe tijdelijk vanwege het opgroeien van de verjonging die het gat opvult. De beide maatregelen zullen vooral ingezet moeten worden om de stabiliteit en diversiteit van het bos te verhogen

Waarom volstaat een fosfaatbemesting met Ca bij lage pH? Het effect van Ca zonder het pH effect van bekalking; literatuuronderzoek

Dit rapport doet verslag van een deelonderzoek uit de Evaluatie van effectgerichte maatregelen in multifunctionele bossen 2004-2005 en is gericht op de effecten van de maatregelen bemesting en bekalking in bossen als overbruggingsmaatregel in het kader van het Overlevingsplan Bos en Natuur (OBN). Er zijn veel literatuurbronnen beschikbaar over de meestal positieve effecten van bekalking, na negatieve effecten van verzuring op de bodem en de plant. Echter in deze literatuur studie gaat het in het bijzonder om de vraag of Ca2+ ook afzonderlijk voldoende effect heeft op de invloeden van verzuring op de plant. Intensief is gezocht naar literatuur waarin experimenten met zuiver Ca bemesting, zonder pH effecten, duidelijk gescheiden waren van bekalking, dus mét pH effecten, eventueel in een combinatie met andere elementen. Voor bomen kon in dit onderzoek geen geschikte bronnen worden gevonden van proeven met bijvoorbeeld gips. In Braziliaanse literatuur over landbouwgewassen konden wèl voorbeelden worden gevonden van positief effect van Ca2+ in zure bodems. Bemesting met gips (zonder pH effect) bleek daarbij juist meer effectief dan bekalking, omdat dit sneller werkte en eerder doordrong ook in het diepere wortelmilieu. Geconcludeerd kan dus worden dat een fosfaatmeststof volstaat voor het opheffen van een Ca-tekort. Onder de huidige Nederlandse condities behoeft de pH niet verhoogd te worden als er met fosfaat wordt bemest

Investment and export opportunities in a sustainable pig supply chain in China

Given the increasing average income of the Chinese consumer, increasing awareness of food safety and giant performance arrears there is a large need for investments in the entire pig supply chain. The Netherlands can contribute to a more sustainable Chinese pig production system, both by exporting products and investments. See Chapter 10. The Chinese government stimulates the development of large production and processing facilities, resulting in a great demand for machinery in the entire supply chain and the required knowledge for its optimal use, such as for housing techniques, animal identification systems, feed composition, meat processing techniques, logistics chain management, traceability and benchmark systems and efficiency-oriented training for managers. See Chapter 10

Modelling the Effect of Climate Change on Environmental Pollution Losses from Dairy Systems in the UK

21 p.So far, there has been strong emphasis on studying the impacts of climate change on agriculture in terms of changes in food production; however, there is increasing evidence that agricultural ecosystems (e.g. livestock) will also be severely affected in terms of other goods and services. For example, patterns and loads of environmental pollution derived from nutrient losses are expected to change dramatically (e.g. increased run-off: Betts et al., 2007). There have been few studies that use a system-based approach to explore the complex interactions between farm inputs, response of system components and inherent site factors that give rise to changes in productivity, environmental pollution losses and agricultural services in future scenarios. This article describes the methodology and the results of a study to evaluate the effect of climate change only on losses of nitrogen (N) and carbon (C) from grassland-based livestock systems in 10 UK Regional Development Programme (RDP) areas. In order to do so, a modelling framework integrating different models at the crop and farm level was developed and implemented. Simulated projections suggest that farming systems will undergo different changes in food production and associated nutrient losses depending on different areas and time-slices. Potential trade-offs on other pillars of farm sustainability (e.g. net farm income, biodiversity and soil quality) were simulated and illustrated as an example