342 research outputs found
Empirical methods of identifying and quantifying trophic interactions for constructing soil food-web models
No full textIntroduction Food-web models, which depict the trophic relationships between organisms within a community, form a powerful and versatile approach to study the relationships between community structure and ecosystem functioning. Although food-web models have recently been applied to a wide range of ecological studies (Memmott, 2009; Sanders et al., 2014), such approaches can be greatly improved by introducing high-resolution trophic information from empirical studies and experiments that realistically describe topological structure and energy flows (de Ruiter et al., 2005). Over the last decades major technological advances have been made in empirically characterizing trophic networks by describing, in detail, the connectedness and flows in food webs. Existing empirical techniques, such as stable isotope probing (SIP) (Layman et al., 2012), have been refined and new approaches have been created by combining methods, e.g., combining Raman spectroscopy or fatty acid analysis with SIP (Ruess et al., 2005a; Li et al., 2013). These empirical methods can provide insight into different aspects of food webs and together form an extensive toolbox to investigate trophic interactions. It is crucial to recognize the potential and limitations of a range of empirical approaches in order to choose the right method in the design of empirically based food-web studies. Empirically based food webs are generally classified according to the type of input information that is required. In the following lines we will provide an overview of four types of food-web model: connectedness webs, semi-quantitative webs, energy-flow webs, and functional webs. Paine (1980) introduced three of those webs, which are widely accepted and applied in food-web studies across ecosystems. We propose to add a fourth type of empirically based food web, the semi-quantitative web. All of these food webs have the same basic structure, but the conceptual webs differ in the type of trophic information they describe and represent (Figure 16.1). Connectedness webs (Figure 16.1a) define the basic structure of a food web by describing the food-web connections per se
Linking Ecology and Epidemiology: The Case of Infected Resource
No full textInterspecific interactions in ecological communities are the main mechanisms that determine structure, functioning, and stability of ecosystems (May, 1972, 1973; Neutel et al., 2002; Alessina and Tang, 2012; Mougi and Kondoh, 2012, 2014). These interactions can be qualitatively positive, negative, or neutral, and pairs of these interactions between two species may be of opposite sign (e.g., trophic, parasitic) or of equivalent sign (e.g., mutualistic, competitive). Most of the research on ecological interactions has focused on feeding relations (Odum, 1971; Pimm, 1982; Levin et al., 2009; McCann, 2011; Moore and de Ruiter, 2012), but in recent studies of ecological communities this was extended to parasitic (Huxham et al., 1995; Thompson et al., 2004; Lafferty et al., 2006; Kuris et al., 2008) and non-parasitic non-trophic relations (Thebault and Fountaine, 2010; Fontaine et al., 2011; Kéfi et al., 2012; Mougi and Kondoh, 2012; Sauve et al., 2014). In this chapter, we focus on parasitic relations and notably on the question of how trophic interactions and infectious agents mutually influence each other. Here we will refer to the combined classes of infectious species as parasites (see next section for details). The impact of parasites in an ecological community can be quantified through their direct influence on the food-web structure, as well as more indirectly through the way they influence physiological traits of host species and trophic relations of the host and non-host species (Kéfi et al., 2012; Selakovic et al., 2014). In this chapter we first briefly discuss the diversity of parasitic interactions, their relationships with host and non-host species, as well as their effects on a simple consumer–resource relationship consisting of one host and one non-host species. The largest part of the chapter is devoted to exploring a basic model, to show how intricately ecological and epidemiological effects are interwoven, even in the simplest possible ecosystem consisting of two species. Even though this model is basic in the sense that it is low dimensional and not meant to realistically represent any particular system, the analysis does hint at broader ecological insight, for example into possible differences between terrestrial and aquatic ecosystems based on parasitic interaction. The simple analysis highlights the need to study the link between ecology and infectious disease epidemiology in more realistic models
The role of Scene Type and Priming in the processing and selection of a spatial frame of reference
No full textJohannsen K, de Ruiter J. The role of Scene Type and Priming in the processing and selection of a spatial frame of reference. Frontiers in Psychology. 2013;4:182.The selection and processing of a spatial frame of reference (FOR) in interpreting verbal scene descriptions is of great interest to psycholinguistics. In this study, we focus on the choice between the relative and the intrinsic FOR, addressing two questions: (a) does the presence or absence of a background in the scene influence the selection of a FOR, and (b) what is the effect of a previously selected FOR on the subsequent processing of a different FOR. Our results show that if a scene includes a realistic background, this will make the selection of the relative FOR more likely. We attribute this effect to the facilitation of mental simulation, which enhances the relation between the viewer and the objects. With respect to the response accuracy, we found both a higher (with the same FOR) and a lower accuracy (with a different FOR), while for the response latencies, we only found a delay effect with a different FOR
Increased n affects uptake of eight grassland species: the role of root surface phosphatase activity
No full textIncreased N deposition may change species composition in grassland communities by shifting them to P limitation. Interspecifi
c diff erences in P uptake traits might be a crucial yet poorly understood factor in determining the N eff ects. To test
the eff ects of increased N supply (relative to P), we conducted two greenhouse fertilization experiments with eight species
from two functional groups (grasses, herbs), including those common in P and N limited grasslands. We investigated plant
growth and P uptake from two P sources, orthophosphate and not-readily available P (bound-P), under diff erent N supply
levels. Furthermore, to test if the N eff ects on P uptake was due to N availability alone or altered N:P ratio, we examined
several uptake traits (root-surface phosphatase activity, specifi c root length (SRL), root mass ratio (RMR)) under varying
N:P supply ratios. Only a few species ( M. caerulea , A. capillaris , S. pratensis ) could take up a similar amount of P from
bound-P to that from orthophosphate. Th ese species had neither higher SRL, RMR, phosphatase activity per unit root
(Pase root ), nor higher total phosphatase activity (Pase tot : Pase root times root mass), but higher relative phosphatase activity
(Pase rel : Pase tot divided by biomass) than other species. Th e species common from P-limited grasslands had high Pase rel .
P uptake from bound-P was positively correlated with Pase tot for grasses. High N supply stimulated phosphatase activity
but decreased RMR and SRL, resulting in no increase in P uptake from bound-P. Pase root was infl uenced by N:P supply
ratio, rather than by only N or P level, whereas SRL and RMR was not dominantly infl uenced by N:P ratio. We conclude
that increased N stimulates phosphatase activity via N:P stoichiometry eff ects, which potentially increases plant P uptake
in a species-specifi c way. N deposition, therefore, may alter plant community structure not only by enhancing productivity,
but also by favouring species with traits that enable them to persist better under P limited conditions
Eyetracking for two-person tasks with manipulation of a virtual world
No full textCarletta J, Nicol C, Tailor T, Hill R, de Ruiter J, Bard EG. Eyetracking for two-person tasks with manipulation of a virtual world. Behavior Research Methods. 2010;42(1):254-265
Neural correlates of intentional communication
No full textNoordzij ML, Newman-Norlund SE, de Ruiter J, Hagoort P, Levinson SC, Toni I. Neural correlates of intentional communication. Frontiers in Neuroscience. 2010;4:1-7
Parliamentary scrutiny of methods of open coordination. The involvement of the Dutch and British parliament in the EU governance of the knowledge-based society
No full textAlthough the Open Method of Coordination (OMC) – a policy tool aimed at fostering mutual policy learning between EU member states – adds an EU dimension to national policies, no competences are shifted to the EU level. In addition, the OMC promises to involve a broad range of actors, among which members of parliament. Scholars have studied the OMC employment and OMC social inclusion and showed that the OMC
breaks this promise by affecting the national policy making process outside of the control of national parliaments. This paper investigates the involvement of two national
parliaments across three under-researched OMCs, related with the knowledge-based society theme
Earth’s buried wealth: uncovering global soil biodiversity.
No full textSoils harbor more than half the biodiversity of our planet, yet they are underappreciated and often unprotected. Among the initiatives promoting the sustainable use and conservation of soil biodiversity is the International Network on Soil Biodiversity (NETSOB - https://www.fao.org/global-soil-partnership/netsob/en/), a Technical Network of the Global Soil Partnership (GSP) within the Food and Agriculture Organization of the United Nations (FAO) that promotes the sustainable use and conservation of soil biodiversity. NETSOB, together with its chairs and members, initiated this special issue named “Highlights from the International Network on Soil Biodiversity” that covers advancements in soil biodiversity research, and provides insights into its ecological, economic, and policy dimensions. The articles included in this special issue cover topics such as the current knowledge of soil biodiversity worldwide, bibliometric analyses on ecosystem services provided by soil biodiversity, as well as on the state of global micro-, meso- macro- and megafauna biodiversity, the potential threats to soil biodiversity, and information on the establishment of the Global Soil Biodiversity Observatory (GLOSOB), an initiative established to assess and monitor soil biodiversity, and forecast changes in soil biodiversity worldwide. The articles in this special issue highlight the knowledge gaps in soil biodiversity, including the connections between specific components of soil biodiversity and parameters such as threats, ecosystem services and soil degradation, and value and limitations of using soil respiration and soil organic carbon as a proxy to infer soil biodiversity. We suggest that recognizing and preserving soil biodiversity is a matter of safeguarding our own future and the health of our planet
Hypsometric and geometric controls on hydrodynamics, tidal asymmetry, and sediment connectivity in shallow estuarine systems
No full textEstuaries and tidal basins are highly dynamic coastal systems that serve as a transition zone between the river and the ocean. The morphological evolution of these diverse environments is modulated by non-linear feedbacks between tides, meteorological forcing, and sediment transport processes. This thesis focuses on the fundamental links between these physical processes, and the geomorphologic characteristics of shallow estuarine systems, specifically: (i) how shallow basin geometries and hypsometries affect hydrodynamics and tidal asymmetry, (ii) how wind-induced currents modify velocity asymmetry in shallow basins, and (iii) defining the relationships between geometry, hypsometry, and sediment connectivity inside shallow estuarine systems.
Linking geomorphological characteristics and tidal processes in shallow tidal basins
The links between tidal basin geometry and hypsometry, bed shear stress patterns, tidal velocity- and slack water asymmetry, and hypsometric profile shapes were explored for six shallow microtidal basins of Tauranga Harbour, New Zealand. Model results, obtained from a depth-averaged numerical model developed in Delft3D for the full estuarine system, indicated that tidal distortion increases with distance from basin entrance. A simple ratio between tidal basin width and entrance width was defined to describe the planform shape of the basin. This metric, termed the ‘basin dilation factor’ indicates whether a basin can be designated as a divergent or convergent geometry. Shallow basins with a constricted geometry and relatively deep entrance channels were found to be associated with small bed shear stress values and high rates of flood-directed tidal velocity asymmetry in the sheltered basin centres. These results suggest substantial potential for sediment deposition of larger particles. Moreover, slack water asymmetry within these basins was weakly ebb-directed, indicating a small potential for export of fine sediments. These divergent, depositional basins were found to be characterized by convex hypsometric profiles with elevated intertidal regions. Conversely, unconstricted, convergent basins were associated with larger bed shear stress values and more ebb-directed tidal velocity asymmetry within basin centres. Consequently, there was limited potential for overall sediment deposition inside these basins. The slack water asymmetry was weakly flood-dominant, suggesting limited potential for fine sediment input. The comparatively high-energy conditions within these exposed tidal basins were associated with a less convex hypsometric intertidal profile. This study highlights the impacts of specific geomorphologic basin characteristics on tidal processes in shallow estuarine systems. The ability to predict the links between tidal asymmetry and morphological changes in tide-dominated systems is beneficial for coastal management, as the morphological evolution of estuarine systems affects coastal ecosystem functioning, port and estuary navigability, and potential for coastal protection.
Understanding the effects of wind-driven currents on velocity asymmetry in shallow tidal basins
Numerical modelling experiments were conducted for a series of idealized basins in which planform shape and bathymetry were varied. The model results were used to examine how wind-generated currents modulate horizontal velocity asymmetry patterns in shallow tidal basins. This study revealed that wind-driven currents primarily influence mean and peak flow velocities inside the basins, with a limited effect on tidal harmonics. Faster wind speeds led to more extreme horizontal velocity asymmetry (larger velocity asymmetry values), without substantially modifying overall spatial patterns of velocity asymmetry. The velocity asymmetry was found to be strongly depth-dependent, with changes to asymmetry patterns being most evident for wind speeds of 6 m/s and greater, and for wind directions parallel to the main axes of the tidal channels in the basins. Shallow intertidal regions inside the basins were characterized by a downwind-directed increase in velocity asymmetry, whereas deeper subtidal channels experienced asymmetry changes in the opposite direction. Wind event duration and timing were also found to influence the velocity asymmetry patterns. The differences between the relative size of the peak flood- and ebb directed currents were most evident for wind events with a duration of 6 hours or less that coincide with flooding tides. The results of this study highlight that hydrodynamics, sediment transport, and morphological evolution in shallow estuaries are modulated by tidal processes as well as meteorological forcing. Since anthropogenically induced climate change is expected to increase the intensity of extreme meteorological events, the ability to predict future pathways of morphological change in shallow estuarine systems, based on specific meteorological conditions as well as well-defined local tidal regimes, is vital for the management of these dynamic systems.
An examination of sediment connectivity in a shallow estuarine system
The sediment connectivity framework was used to examine links between hydrodynamics, sediment transport pathways, and local hypsometry inside a shallow estuarine system (Tauranga Harbour, New Zealand). The estuary was divided into twenty geomorphic cells, representing tidal channels, intertidal flats, and shallow sub-basins. Depth-averaged numerical modelling simulations were carried out to quantify tide-driven sediment connectivity between the cells for five sediment grainsize classes. Connectivity matrices were developed for the different grainsize classes, based on modelled sediment mass loads. Sediment connectivity inside the estuary was found to be modulated by tidal energy, estuarine morphology (depth), sub-basin hypsometry and geometry (planform shape), and sediment characteristics. The connectivity matrices, combined with metrics such as link density and cell strength, illustrated that sediment mass loads, and hence connectivity, were largest in the high-energy environments of the deep tidal channels located in the main estuary. In the more sheltered upper estuary, and inside the shallow sub-basins, connectivity was reduced. For fine sediments ( 275 μm) was found to be ~20%, with transport pathways primarily confined to the deeper regions of the estuary. An in-depth analysis of sediment transport pathways between the shallow sub-basins emphasized that flood-dominant, divergent basins with a convex-shaped hypsometric profile mainly function as sediment sinks, whereas ebb-dominant convergent basins act as sediment sources.
This thesis highlights the substantial dependence of tidal asymmetry, morphology, sediment transport and connectivity on hypsometry, geometry, and grainsize characteristics inside shallow estuaries. Additionally, the effects of wind-driven currents on the non-linear physical processes inside these highly dynamic environments are described. Overall, this work provides a novel elucidation of some of the relationships between geometric parameters and forcing mechanisms applicable to many shallow coastal systems
Beyond borders : broadening the artistic palette of (composing) improvisers in jazz
No full text
In this on-line dissertation, jazz saxophonist Dick de
Graaf investigates a variety of compositional and improvisational models and
techniques in contemporary jazz and Western art music, and discusses possible
applications of these materials in current jazz practices. The study includes
examinations of educational publications by five selected jazz artists (Dave
Liebman, Jerry Bergonzi, George Garzone, Walt Weiskopf, and John
O’Gallagher), and the analysis of compositional techniques by two composers
of the 20th century: Peter Schat's Tone Clock and Olivier Messiaen's modes of
limited transposition. In addition, these theories and techniques are
illustrated by selected examples (transcriptions and audio excerpts) and by
examples of applications by various musicians, including the author. All
examples are thoroughly analyzed and evaluated in order to determine their
potential use in contemporary jazz practices.
The research results provide comprehensive insights into compositional and
improvisational processes in jazz, and offer materials that can be useful for
the personal artistic development of jazz practitioners, including musicians,
composers, and educators.
Research in and through artistic practic
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