Modeling Across-Trial Variability in the Wald Drift Rate Parameter

The shifted-Wald model is a popular analysis tool for one-choice reaction-time tasks. In its simplest version, the shifted-Wald model assumes a constant trial-independent drift rate parameter. However, the presence of endogenous processes—fluctuation in attention and motivation, fatigue and boredom—suggest that drift rate might vary across experimental trials. Here we show how across-trial variability in drift rate can be accounted for by assuming a trial-specific drift rate parameter that is governed by a positive-valued distribution. We consider two candidate distributions: the truncated normal distribution and the gamma distribution. For the resulting distributions of first-arrival times, we derive analytical and sampling-based solutions, and implement the models in a Bayesian framework. Recovery studies and an application to a data set comprised of 1469 participants suggest that (1) both mixture distributions yield similar results; (2) all model parameters can be recovered accurately except for the drift variance parameter; (3) despite poor recovery, the presence of the drift variance parameter facilitates accurate recovery of the remaining parameters; (4) shift, threshold, and drift mean parameters are correlated

Adapting complex multi-level landscape systems to climate change

Adaptation to climate change is becoming a prominent issue in both landscape research and landuse planning. Current research focuses mainly on the description of potential impacts for different societal sectors and in general fails to provide useful information to help define climate adaptation strategies and specific policy measures or development plans. This editorial briefly explores the reasons why this may be the case and proposes a conceptual framework for more effective climate adaptation research. Furthermore, it introduces three papers that address adaptation of landscape systems to climate change as an integrated multi-level challenge. The included papers focus on the relationship between climate-induced changes in the natural system and the economics-oriented societal system and specifically address the interdependencies across scales

Klimaatadaptatie droge rurale zandgronden - Gelderland

Het doel van dit project is een beeld te krijgen van de gevolgen van klimaatveranderingen voor de droge zandgronden van de provincie Gelderland, om de gevolgen van klimaatverandering in gebiedsontwikkelingsprocessen in te bouwen in de gebieden ‘Baakse Beek’ en ‘Blauwe Bron’. Het doel van dit project is een beeld te krijgen van de gevolgen van klimaatveranderingen voor de droge zandgronden van de provincie Gelderland, om de gevolgen van klimaatverandering in gebiedsontwikkelingsprocessen in te bouwen in de gebieden ‘Baakse Beek’ en ‘Blauwe Bron’. In workshops werd door wetenschappers en betrokkenen bij de gebiedsprocessen kennis over effecten van klimaatverandering en adaptatiemogelijkheden gedeeld en werden kennisleemten geïdentificeerd, om de gebiedsprocessen klimaatbestendig te maken

Klimaatverandering in de Grote Polder en Polder Groenendijk : Workshopverslag

Het klimaat verandert en dat merken we langzaam maar zeker. Maar wat zijn hiervan de gevolgen op lokaal niveau? Om hier een beeld van te vormen is informatie over klimaatverandering en (land)gebruik samengebracht voor de Grote Polder en Polder Groenendijk. Kunnen we een eerste beeld vormen van wat klimaatverandering betekent voor het bedrijfsleven op het bedrijvenpark, voor de Heineken-brouwerij, voor de gemeente Zoeterwoude, voor het Hoogheemraadschap van Rijnland, voor de boeren, voor de natuur, en voor de mensen die er wonen en recreëren? Tijdens een bijeenkomst op 28 september 2017, georganiseerd door het Hoogheemraadschap van Rijnland in het kader van de Groene Thema Cirkel Water, is met diverse partijen uit het gebied het beeld besproken en zijn een aantal verhaallijnen afgeleid. Deze verhaallijnen worden verder verwerkt in de ‘story maps’ van de klimaateffectatlas Zuid Holland

Iso-osmotic regulation of nitrate accumulation in lettuce (Lactuca sativa L.)

Concerns about possible health hazards arising from human consumption of lettuce and other edible vegetable crops with high concentrations of nitrate have generated demands for a greater understanding of processes involved in its uptake and accumulation in order to devise more sustainable strategies for its control. This paper evaluates a proposed iso-osmotic mechanism for the regulation of nitrate accumulation in lettuce (Lactuca sativa L.) heads. This mechanism assumes that changes in the concentrations of nitrate and all other endogenous osmotica (including anions, cations and neutral solutes) are continually adjusted in tandem to minimise differences in osmotic potential of the shoot sap during growth, with these changes occurring independently of any variations in external water potential. The hypothesis was tested using data from six new experiments, each with a single unique treatment comprising a separate combination of light intensity, N source (nitrate with or without ammonium) and nitrate concentration carried out hydroponically in a glasshouse using a butterhead lettuce variety. Repeat measurements of plant weights and estimates of all of the main soluble constituents (nitrate, potassium, calcium, magnesium, organic anions, chloride, phosphate, sulphate and soluble carbohydrates) in the shoot sap were made at intervals from about 2 weeks after transplanting until commercial maturity, and the data used to calculate changes in average osmotic potential in the shoot. Results showed that nitrate concentrations in the sap increased when average light levels were reduced by between 30 and 49 % and (to a lesser extent) when nitrate was supplied at a supra-optimal concentration, and declined with partial replacement of nitrate by ammonium in the external nutrient supply. The associated changes in the proportions of other endogenous osmotica, in combination with the adjustment of shoot water content, maintained the total solute concentrations in shoot sap approximately constant and minimised differences in osmotic potential between treatments at each sampling date. There was, however, a gradual increase in osmotic potential (ie a decline in total solute concentration) over time largely caused by increases in shoot water content associated with the physiological and morphological development of the plants. Regression analysis using normalised data (to correct for these time trends) showed that the results were consistent with a 1:1 exchange between the concentrations of nitrate and the sum of all other endogenous osmotica throughout growth, providing evidence that an iso-osmotic mechanism (incorporating both concentration and volume regulation) was involved in controlling nitrate concentrations in the shoot

Impacts of climate change on plant diseases – opinions and trends

There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods

Land use and climate change

Klimaat en landgebruik zijn sterk aan elkaar gerelateerd. Landgebruik beïnvloedt het klimaat, bijvoorbeeld doordat vegetatie kooldioxide opneemt, landbouw stikstof vastlegt en industrie diverse broeikasgassen uitstoot. Omgekeerd betekent een veranderend klimaat dat aanpassingen nodig kunnen zijn in bijvoorbeeld: landbouw (overstap op andere gewassen), natuur (veranderingen binnen ecosystemen), de kustzone (door zeespiegelrijzing) en het rivierengebied (meer ruimte voor water). Deze en andere adaptatie- en mitigatie-maatregelen staan centraal in diverse andere projecten van het ‘Klimaat voor Ruimte’ programma. Centraal in het LANDS project staan de effecten van klimaatverandering op de inrichting en het gebruik van de ruimte

Assessment of the exposure and loads of acidifying and eutrophying pollutants and ozone, as well as their harmful influence on the vitality of the trees and the Speulder forest ecosystem as a whole

Within the framework of the Dutch Priority Program on Acidification, 10 yr of research was conducted in a Douglas fir stand at Speulder forest. Research was conducted to establish the loads and levels of acidifying and eutrophying pollutants and ozone, to determine forest vitality characteristics and follow growth parameters and nutrient status in time and to determine the effects of reduction of loads and levels by manipulation experiments. Results indicate that during the last 20 yr critical levels for air pollutants have hardly been exceeded except for ozone, which slightly affected assimilation. Elevated nitrogen deposition has caused several adverse effects including (i) inhibited mycorrhizal development, leading to a decreased base cation and phosphorus uptake; (ii) elevated foliage/root (fine and coarse) ratios, making the forest more sensitive to drought and windthrow; (iii) elevated nitrogen and arginine concentrations in the foliage, associated with relative base cation and phosphorus deficiency, and (iv) elevated nitrate leaching polluting the groundwater. High inputs of acidity have caused elevated ratios of Al to base cations, affecting fine root (uptake) and depletion of the readily available Al pool, thus affecting the long-term sustainability. Despite these effects, forest vitality, in terms of defoliation/discoloration, is reasonable and forest growth even increased in response to nitrogen. The exceedances of critical loads for nitrogen and acidity, however, implies a (large) risk for the long-term sustainability of the Speulder forest