2,150 research outputs found
Impacts of Land Abandonment on Vegetation: Successional Pathways in European Habitats
Changes in traditional agricultural systems in Europe in recent decades have led to widespread abandonment and colonization of various habitats by shrubs and trees. We combined several vegetation databases to test whether patterns of changes in plant diversity after land abandonment in different habitats followed similar pathways. The impacts of land abandonment and subsequent woody colonization on vegetation composition and plant traits were studied in five semi-natural open habitats and two arable habitats in six regions of Europe. For each habitat, vegetation surveys were carried out in different stages of succession using either permanent or non-permanent plots. Consecutive stages of succession were defined on a physiognomic basis from initial open stages to late woody stages. Changes in vegetation composition, species richness, numbers of species on Red Lists, plant strategy types, Ellenberg indicator values of the vegetation, Grime CSR strategy types and seven ecological traits were assessed for each stage of the successional pathway. Abandonment of agro-pastoral land-use and subsequent woody colonization were associated with changes in floristic composition. Plant richness varied according to the different habitats and stages of succession, but semi-natural habitats differed from arable fields in several ecological traits and vegetation responses. Nevertheless, succession occurred along broadly predictable pathways. Vegetation in abandoned arable fields was characterized by a decreasing importance of R-strategists, annuals, seed plants with overwintering green leaves, insect-pollinated plants with hemi-rosette morphology and plants thriving in nutrient-rich conditions, but an increase in species considered as endangered according to the Red Lists. Conversely, changes in plant traits with succession within the initially-open semi-natural habitats showed an increase in plants thriving in nutrient-rich conditions, stress-tolerant plants and plants with sexual and vegetative reproduction, but a sharp decrease in protected species. In conclusion, our study showed a set of similarities in responses of the vegetation in plant traits after land abandonment, but we also highlighted differences between arable fields and semi-natural habitats, emphasizing the importance of land-use legacy
Frustration - how it can be measured
A misfit parameter is used to characterize the degree of frustration of
ordered and disordered systems. It measures the increase of the ground-state
energy due to frustration in comparison with that of a relevant reference
state. The misfit parameter is calculated for various spin-glass models. It
allows one to compare these models with each other. The extension of this
concept to other combinatorial optimization problems with frustration, e.g.
p-state Potts glasses, graph-partitioning problems and coloring problems is
given.Comment: 10 pages, 1 table, no figures, uses revtex.st
Theodicy and End-of-Life Care
Acknowledgments The section on Islamic perspective is contributed by information provided by Imranali Panjwani, Tutor in Theology & Religious Studies, King's College London.Peer reviewedPublisher PD
On the formation of black holes in non-symmetric gravity
It has been recently suggested that the Non-symmetric Gravitational Theory
(NGT) is free of black holes. Here, we study the linear version of NGT. We find
that even with spherical symmetry the skew part of the metric is generally
non-static. In addition, if the skew field is initially regular, it will remain
regular everywhere and, in particular, at the horizon. Therefore, in the
fully-nonlinear theory, if the initial skew-field is sufficiently small, the
formation of a black hole is to be anticipated.Comment: 9 pages, ordinary LaTex
Electrophysiological activation by masked primes: Independence of prime-related and target-related activities
Visual stimuli that are made invisible by metacontrast masking (primes) have a
marked influence on behavioral and psychophysiological measures such as reaction
time (RT) and the lateralized readiness potential (LRP). 4 experiments are
reported that shed light on the effects that masked primes have on the LRP.
Participants had a go-nogo task in which the prime was associated with 1 of 2
responses even if the target required participants to refrain from responding.
To analyze the electrophysiological responses, we computed the LRP and applied
an averaging method separating the activation due to the prime and the target.
The results demonstrated that (a) masked primes activate responses even in a
nogo situation, (b) this prime-related activation is independent of masking, (c)
and is also independent of whether prime and target require the same responses
(congruent condition) or different responses (incongruent condition)
- …