24 research outputs found
Active Brownian Particles. From Individual to Collective Stochastic Dynamics
We review theoretical models of individual motility as well as collective
dynamics and pattern formation of active particles. We focus on simple models
of active dynamics with a particular emphasis on nonlinear and stochastic
dynamics of such self-propelled entities in the framework of statistical
mechanics. Examples of such active units in complex physico-chemical and
biological systems are chemically powered nano-rods, localized patterns in
reaction-diffusion system, motile cells or macroscopic animals. Based on the
description of individual motion of point-like active particles by stochastic
differential equations, we discuss different velocity-dependent friction
functions, the impact of various types of fluctuations and calculate
characteristic observables such as stationary velocity distributions or
diffusion coefficients. Finally, we consider not only the free and confined
individual active dynamics but also different types of interaction between
active particles. The resulting collective dynamical behavior of large
assemblies and aggregates of active units is discussed and an overview over
some recent results on spatiotemporal pattern formation in such systems is
given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte
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Urban hedges: a review of plant species and cultivars for ecosystem service delivery in north-west Europe
Urban hedges provide a number of important ecosystem services (ESs) including microclimate alteration, flood and pollution mitigation, and biodiversity provision, along with some disservices (DSs, e.g. invasiveness, allergenicity). However, hedge plant species differ in their capacity to promote different services, so it is important that the decision to plant hedges is evidence-based. The objectives of this study were thus to (i) to review the role of urban hedges within NW Europe; (ii) review the available literature detailing the ESs and DSs provided by different plant species and cultivars when used as hedge plants; (iii) identify where there is a lack of evidence for certain species or ESs/DSs; and (iv) develop a starting point for a discussion about appropriate species/cultivar selection to deliver multiple ESs, and avoid DSs.
Many studies consider biodiversity and air quality ESs. There are significant gaps in the literature relating to rainfall mitigation/flood protection, but also CO2 sequestration, allergenicity and human psychological well-being impact of different species. Additionally, for noise and pollution mitigation studies, a range of methodologies and units are used, making comparisons between hedge species difficult/impossible.
A number of common hedge species demonstrated high levels of ESs delivery, including Fagus sylvatica, Crataegus monogyna, Ilex aquifolium and Rosa rugosa. No species surveyed had an entirely negative association with ESs, and most provide at least some benefits in supporting ESs provision (e.g. Viburnum tinus, Laurus nobilis). We created a matrix, in a table form, linking plant species, key plant traits and ESs/DSs, which should make it easier for professionals to choose species best suited to provide multiple benefits, whilst minimising the drawbacks. Our review suggests that the relative contribution of urban hedges to ESs delivery may be under-valued currently, and calls for more research
TRY plant trait database â enhanced coverage and open access
Plant traitsâthe morphological, anatomical, physiological, biochemical and phenological characteristics of plantsâdetermine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of traitâbased plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traitsâalmost complete coverage for âplant growth formâ. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and traitâenvironmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives