Combining a weed traits database with a population dynamics model predicts shifts in weed communities

A functional approach to predicting shifts in weed floras in response to management or environmental change requires the combination of data on weed traits with analytical frameworks that capture the filtering effect of selection pressures on traits. A weed traits database (WTDB) was designed, populated and analysed, initially using data for 19 common European weeds, to begin to consolidate trait data in a single repository. The initial choice of traits was driven by the requirements of empirical models of weed population dynamics to identify correlations between traits and model parameters. These relationships were used to build a generic model, operating at the level of functional traits, to simulate the impact of increasing herbicide and fertiliser use on virtual weeds along gradients of seed weight and maximum height. The model generated ‘fitness contours’ (defined as population growth rates) within this trait space in different scenarios, onto which two sets of weed species, defined as common or declining in the UK, were mapped. The effect of increasing inputs on the weed flora was successfully simulated; 77% of common species were predicted to have stable or increasing populations under high fertiliser and herbicide use, in contrast with only 29% of the species that have declined. Future development of the WTDB will aim to increase the number of species covered, incorporate a wider range of traits and analyse intraspecific variability under contrasting management and environments

Ukrudt i et kulturlandskab

Ukrudt for landmænd er vilde planter for biologer. Landbruget har i dag gode muligheder for at kontrollere ukrudtet og nye undersøgelser viser, at mængden af ukrudt visse steder har nået et historisk lavpunkt, men det omgivende samfund ønsker mere plads til den spontane natur i landskabet. Der bør være plads til lidt ukrudt i et kulturlandskab – også for landmandens egen skyld. I dette kapitel argumenterer biologerne for at det er nødvendig med lidt ukrudt og naturhensyn, hvis landmanden vil glædes over hare, agerhøne og gulspurv. Det er muligt at leve sammen – både effektivt landbrug og vilde planter

Reconsidering the Neighborhood Effect: Does Exposure to Residential Unemployment Influence Voters' Perceptions of the National Economy?

This entry contains details on data access, coding, and output from the analyses

DK-RIM: Assisting integrated management of Lolium multiflorum, Italian ryegrass

Lolium multiflorum (annual Italian ryegrass) and other grass weeds are an increasing problem in cereal cropping systems in Denmark. Grass weeds are highly competitive and an increasing number of species develop resistance against the most commonly used herbicide modes of action. A diverse management strategy provides a better overall control of grass weeds and decreases the reliance on herbicides. The bio-economic decision support system, DK-RIM (Denmark-Ryegrass Integrated Management), was developed to assist integrated management of L. multiflorum in Danish cropping systems, based on the Australian RIM model. DK-RIM provides long-term estimations (10-year period) and visual outputs of L. multiflorum population development, depending on management strategies. The dynamics of L. multiflorum plants within the season and of the soil seed bank across seasons are simulated. The user can combine cultural weed control practices with chemical control options. Cultural practices include crop rotation changes, seeding density, sowing time, soil tillage system, and cover crops. Scenarios with increasing crop rotation diversity or different tillage strategies were evaluated. DK-RIM aims at being an actual support system, aiding the farmer’s decisions and encouraging discussions among stakeholders on alternative management strategies

Fire performance of sandwich panels in a modified ISO room test

Four sandwich panel rooms were constructed as prescribed in the ISO 13784-1 test. However, the construction followed normal industry practice, and the panels were then subjected to damage typically found in commercial premises. The fire load was increased to simulate fires actually occurring in commercial premises, by stepping-up the propane burner from 300 kW to 600 kW, and placing substantial wooden cribs in two of the rooms. The results showed significant differences in fire growth rate and burning behaviour between those panels filled with polyisocyanurate (PIR) and those filled with stone wool in both the experiments without and with the wood crib. Most significantly, the PIR pyrolysis products caused ignition (by radiation from above) of the wood crib 1 minute after the burner was stepped up to 300 kW (11 minutes into the test) rather than 2 minutes after the burner had been stepped up to 600 kW (22 minutes into the test) for the stone wool panels. This interaction between building and contents is frequently ignored in assessments of fire safety. After a few minutes, the PIR pyrolysis products that escaped outside the room, from between the panels, ignited. The extra thermal attack from PIR fuelled flames distorted the panels, exposing more PIR and resulting in large flames on both the inside and outside of the enclosure. From a fire safety perspective this is most important as it shows that with larger fire loads typical of those found in commercial premises, steel-faced PIR filled panels are not capable of acting as fire barriers, and support flame spread through compartment walls and ceilings. In addition, the PIR panelled rooms produced very large quantities of dense smoke and toxic effluents, where the stone wool panelled rooms produced small amounts of light smoke of lower toxicity