Mode-locking in systems of globally coupled phase oscillators

We investigate the dynamics of a Kuramoto-type system of globally coupled phase oscillators with equidistant natural frequencies and a coupling strength below the synchronization threshold. It turns out that in such cases one can observe a stable regime of sharp pulses in the mean field amplitude with a pulsation frequency given by spacing of the natural frequencies. This resembles a process known as mode-locking in laser and relies on the emergence of a phase relation induced by the nonlinear coupling. We discuss the role of the first and second harmonic in the phase-interaction function for the stability of the pulsations and present various bifurcating dynamical regimes such as periodically and chaotically modulated mode-locking, transitions to phase turbulence and intermittency. Moreover, we study the role of the system size and show that in certain cases one can observe type-II supertransients, where the system reaches the globally stable mode-locking solution only after an exponentially long transient of phase turbulence

BioBio - Indikatoren für Biodiversität in biologischen und extensiven Landwirtschaftssystemen

Das EU-Forschungsprojekt BioBio schließt eine Lücke in der Verfügbarkeit wissenschaftlich fundierter, praktisch relevanter und international anwendbarer Biodiversitätsindikatoren für den Ökolandbau und andere extensive Landnutzungssysteme. Ziel des Projektes war es, ein breit anwendbares Indikatorensystem und standardisierte Methoden für die Beurteilung des Nutzens von ökologischer und extensiver Landwirtschaft für die Biodiversität auf landwirtschaftlich genutzten Flächen zur Verfügung zu stellen. Dazu wurden Indikatoren zusammengestellt, bewertet und standardisierte Analysemethoden definiert. 2010 wurden aus einer Vorauswahl 48 vielversprechendsten Indikatoren europaweit in 12 Fallstudien getestet. Von diesem Gesamtset der Indikatoren werden abschließend drei Indikatoren zur genetischen, vier Indikatoren zur Arten- und zehn Indikatoren zur Lebensraumdiversität sowie 14 indirekte Managementindikatoren für die Anwendung empfohlen

Leap-frog patterns in systems of two coupled FitzHugh--Nagumo units

We study a system of two identical FitzHugh-Nagumo units with a mutual linear coupling in the fast variables. While an attractive coupling always leads to synchronous behavior, a repulsive coupling can give rise to dynamical regimes with alternating spiking order, called leap-frogging. We analyze various types of periodic and chaotic leap-frogging regimes, using numerical pathfollowing methods to investigate their emergence and stability, as well as to obtain the complex bifurcation scenario which organizes their appearance in parameter space. In particular, we show that the stability region of the simplest periodic leap-frog pattern has the shape of a locking cone pointing to the canard transition of the uncoupled system. We also discuss the role of the timescale separation in the coupled FitzHugh-Nagumo system and the relation of the leap-frog solutions to the theory of mixed-mode oscillations in multiple timescale systems

Leap-frog patterns in systems of two coupled FitzHugh-Nagumo units

We study a system of two identical FitzHugh-Nagumo units with a mutual linear coupling in the fast variables. While an attractive coupling always leads to synchronous behavior, a repulsive coupling can give rise to dynamical regimes with alternating spiking order, called leap-frogging. We analyze various types of periodic and chaotic leap-frogging regimes, using numerical pathfollowing methods to investigate their emergence and stability, as well as to obtain the complex bifurcation scenario which organizes their appearance in parameter space. In particular, we show that the stability region of the simplest periodic leap-frog pattern has the shape of a locking cone pointing to the canard transition of the uncoupled system. We also discuss the role of the timescale separation in the coupled FitzHugh-Nagumo system and the relation of the leap-frog solutions to the theory of mixed-mode oscillations in multiple timescale systems

LANDSCAPE AESTHETICS AS AN INDICATOR FOR SOCIAL SUSTAINABILITY OF CROP ROTATIONS

The goal of this study was to evaluate different crop rotations in terms of landscape aesthetics. Klostergut Scheyern has been used as an example, since its current crop rotation must be changed. Therefore, people living in the neighbourhood of Klostergut Scheyern have been shown photos of each crop at different periods of the year. Additionally, a questionnaire containing quantitative, as well as qualitative questions has been developed. Each crop has got a grade; the best one being 1 up to the worst one being 4. People have been allowed to justify their ranking. Also, the use of agricultural machines has been presented on photos. For each crop, participants could decide whether they liked or disliked the working steps. In summary, all crops have been evaluated rather positively. The grades reach from 1.4 to 2.6. The use of machines has hardly ever influenced people’s opinions. Taking qualitative comments into consideration, the survey revealed the difficulty to separate purely visual aspects from moral attitudes towards a certain crop

Examining farm-to-table during the COVID-19 pandemic: Sustainability and the chef-farmer relationship in times of stress

Food is foundational to culture. While farm-to-table culinary tourism has expanded greatly over the past several decades, the abrupt onslaught of the COVID-19 pandemic seemingly reversed course overnight. In the U.S., many restaurants were shuttered for several months and subsequently had to alter their business model to reopen. Meanwhile, farmers that worked closely with chefs were vulnerable to dramatic changes in purchasing habits. Therefore, this study sought to explore the relationship between chefs and farmers and how the stress of the pandemic impacted these relationships. It also looked at the role of shared sustainability values on the farmer-chef relationship during times of stress. The study took place between October 2020 and March 2021 and involved in-depth virtual interviews with farmers and chefs. Preliminary results suggest that while working relationships are not always contingent on shared values, shared sustainability values can be critical in maintaining these connections during difficult times

Untersuchungen zum Einfluss ausgebrachter Hummelvölker auf Samenerträge von Rotklee

It is known that a lot of agricultural crops are dependent on pollination by insects. While managing of pollinators for some crops is common, the effect of artificially breed bumblebees on yields of Red Clover (Trifolium pratense) is less studied. Here we present results of a field experiments where boxes with bumblebees (Bombus terrestris) where used to raise the pollination and thus the seed yields. By comparing test plots in different fields the effects were investigated. In the experiment no significant differences were found between the plots with or without artificially breed bumblebees. Possible reasons are discussed

Trichomonas gallinae infections in the naïve host Montifringilla nivalis subsp. nivalis

Infectious diseases bear a great risk for populations of naïve host species. In the present article we inform about the first microscopic and molecular detection of the bird pathogen Trichomonas gallinae in the White-winged Snowfinch (Montifringilla nivalis subsp. nivalis). The emergence of trichomonosis in this highly specialised alpine bird species may pose a serious threat to its already declining population. Interspecies transmission of T. gallinae most likely occurred at a bird feeder in a Swiss mountain village. Monitoring of the disease and immediate measures to prevent its spread are urgently needed

Species–area relationships in continuous vegetation : evidence from Palaearctic grasslands

Aim: Species-area relationships (SARs) are fundamental scaling laws in ecology although their shape is still disputed. At larger areas power laws best represent SARs. Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in continuous vegetation. We asked which function describes SARs best at small grains and explored how sampling methodology or the environment influence SAR shape. Location: Palaearctic grasslands and other non-forested habitats. Taxa: Vascular plants, bryophytes and lichens. Methods: We used the GrassPlot database, containing standardised vegetation-plot data from vascular plants, bryophytes, and lichens spanning a wide range of grassland types throughout the Palaearctic and including 2057 nested-plot series with at least seven grain sizes ranging from 1 cm2 to 1024 m². Using non-linear regression, we assessed the appropriateness of different SAR functions (power, power quadratic, power breakpoint, logarithmic, Michaelis-Menten). Based on AICc, we tested whether the ranking of functions differed among taxa, methodological settings, biomes or vegetation types. Results: The power function was the most suitable function across the studied taxonomic groups. The superiority of this function increased from lichens to bryophytes to vascular plants to all three taxonomic groups together. The sampling method was highly influential as rooted-presence sampling decreased the performance of the power function. By contrast, biome and vegetation type had practically no influence on the superiority of the power law. Main conclusions: We conclude that SARs of sessile organisms at smaller spatial grains are best approximated by a power function. This coincides with several other comprehensive studies of SARs at different grain sizes and for different taxa, thus supporting the general appropriateness of the power function for modelling species diversity over a wide range of grain sizes. The poor performance of the Michaelis-Menten function demonstrates that richness within plant communities generally does not approach any saturation, thus calling into question the concept of minimal area