Pink landscapes: 1/f spectra of spatial environmental variability and bird community composition

Temporal and spatial environmental variability are predicted to have reddened spectra that reveal increases in variance with the period or length sampled. However, spectral analyses have seldom been performed on ecological data to determine whether these predictions hold true in the case of spatial environmental variability. For a 50 km long continuous transect of 128 point samples across a heterogeneous cultural landscape in the Czech Republic, both habitat composition and bird species composition decomposed by standard ordination techniques did indeed exhibit reddened spectra. The values of main ordination axes have relationships between log spectral density and log frequency with slopes close to -1, indicating 1/f, or 'pink' noise type of variability that is characterized by scale invariance. However, when habitat composition was controlled for and only residuals for bird species composition were analysed, the spectra revealed a peak at intermediate frequencies, indicating that population processes that structure bird communities but are not directly related to the structure of the environment might have some typical correlation length. Spatial variability of abundances of individual species was mostly reddened as well, but the degree was positively correlated to their total abundance and niche position (strength of species-habitat association). If 'pink' noise type of variability is as generally typical for spatial environmental variability as for temporal variability, the consequences may be profound for patterns of species diversity on different spatial scales, the form of species-area relationships and the distribution of abundances within species ranges

The Seiberg-Witten prepotential and the Euler class of the reduced moduli space of instantons

The n-instanton contribution to the Seiberg-Witten prepotential of N=2 supersymmetric d=4 Yang Mills theory is represented as the integral of the exponential of an equivariantly exact form. Integrating out an overall scale and a U(1) angle the integral is rewritten as (4n-3) fold product of a closed two form. This two form is, formally, a representative of the Euler class of the Instanton moduli space viewed as a principal U(1) bundle, because its pullback under bundel projection is the exterior derivative of an angular one-form.Comment: LaTex, 15 page

Structure of the species-energy relationship

The relationship between energy availability and species richness (the species-energy relationship) is one of the best documented macroecological phenomena. However, the structure of species distribution along the gradient, the proximate driver of the relationship, is poorly known. Here, using data on the distribution of birds in southern Africa, for which species richness increases linearly with energy availability, we provide an explicit determination of this structure. We show that most species exhibit increasing occupancy towards more productive regions (occurring in more grid cells within a productivity class). However, average reporting rates per species within occupied grid cells, a correlate of local density, do not show a similar increase. The mean range of used energy levels and the mean geographical range size of species in southern Africa decreases along the energy gradient, as most species are present at high productivity levels but only some can extend their ranges towards lower levels. Species turnover among grid cells consequently decreases towards high energy levels. In summary, these patterns support the hypothesis that higher productivity leads to more species by increasing the probability of occurrence of resources that enable the persistence of viable populations, without necessarily affecting local population densities

The telltale heart: a non-invasive method to determine the energy expenditure of incubating Great Cormorants Phalacrocorax carbo carbo

We studied the energetics of incubating Great Cormorants Phalacrocorax carbo carbo via heart rate and respirometric measurements performed in captive and free-living animals. We applied a modified heart beat frequency (HR) monitor built for use in human athletics as well as respirometry for measurements in four captive-bred cormorants at Neumuenster Zoo, Germany. The obtained data were used to model the relationship between HR and metabolic rate (MR). The resulting correlations were MR (W kg-0.723) = 4.76 + 0.01HR (bpm) during daytime and MR (W kg-0.723) = 2.33 + 0.03HR (bpm) at night. Furthermore, the heart beat frequencies of 5 free-living, incubating cormorants at the Chausey Islands, France, were measured acoustically using artificial eggs while the activities at the nest were observed via video. HR-MR models established in the captive animals were used to determine the activity-dependent energy expenditure in these free-living cormorants. The Median MR was 5.08 W kg-0.723 at night, 6.06 W kg-0.723 while resting and sleeping during daytime, 6.20 W kg-0.723 during preening, gular flutter and unrest and 6.47 W kg-0.723 during nest building. In resting birds we found a nocturnal reduction in the energy expenditure of 16 %. Our method for measurement of heart beat frequency appears promising as a technique for determination of HR with minimal restraint to the anima

The energetics response to a warmer climate: relative contributions from the transient and stationary eddies

We use the Lorenz Energy Cycle (LEC) to evaluate changes in global energetic activity due to CO<sub>2</sub>-doubling in the coupled atmosphere-ocean ECHAM5/MPI-OM model. Globally, the energetic activity – measured as the total conversion rate of available potential energy into kinetic energy – decreases by about 4 %. This weakening results from a dual response that consists of a strengthening of the LEC in the upper-troposphere and a weakening in the lower and middle troposphere. This is fully consistent with results from a coarser resolution version of the same coupled model. We further use our experiments to investigate the individual contributions of the transient and stationary eddy components to the main energetics response. <br><br> The transient eddy terms have a larger contribution to the total energetic activity than the stationary ones. We find that this is also true in terms of their 2 × CO<sub>2</sub>-response. Changes in the transient eddy components determine the main energetics response, whereas the stationary eddy components have very small contributions. Hence, the dual response – strengthening in the upper troposphere and weakening below – concerns mainly the transient eddy terms. We can relate qualitatively this response to the two main features of the 2 × CO<sub>2</sub> warming pattern: (a) the tropical upper-tropospheric warming increases the pole-to-equator temperature gradient – strengthening the energetic activity above – and enhances static stability – weakening the energetic activity below; and (b) the high-latitude surface warming decreases the pole-to-equator temperature gradient in the lower troposphere – weakening the energetic activity below. Despite the small contribution from the stationary eddies to the main energetics response, changes in stationary eddy available potential energy (<i>P</i><sub>se</sub>) reflect some features of the warming pattern: stronger land-sea contrasts at the subtropics and weaker land-sea contrasts at the high northern latitudes affect <i>P</i><sub>se</sub> regionally, but do not affect the global energetics response

Exploring high-end climate change scenarios for flood protection of the Netherlands

This international scientific assessment has been carried out at the request of the Dutch Delta Committee. The "Deltacommissie" requested that the assessment explore the high-end climate change scenarios for flood protection of the Netherlands. It is a state-of–the art scientific assessment of the upper bound values and longer term projections (for sea level rise up to 2200) of climate induced sea level rise, changing storm surge conditions and peak discharge of river Rhine. It comprises a review of recent studies, model projections and expert opinions of more than 20 leading climate scientists from different countries around the North Sea, Australia and the US

Species abundance distribution results from a spatial analogy of central limit theorem

Copyright © 2009, The National Academy of SciencesThe frequency distribution of species abundances [the species abundance distribution (SAD)] is considered to be a fundamental characteristic of community structure. It is almost invariably strongly right-skewed, with most species being rare. There has been much debate as to its exact properties and the processes from which it results. Here, we contend that an SAD for a study plot must be viewed as spliced from the SADs of many smaller nonoverlapping subplots covering that plot. We show that this splicing, if applied repeatedly to produce subplots of progressively larger size, leads to the observed shape of the SAD for the whole plot regardless of that of the SADs of those subplots. The widely reported shape of an SAD is thus likely to be driven by a spatial parallel of the central limit theorem, a statistically convergent process through which the SAD arises from small to large scales. Exact properties of the SAD are driven by species spatial turnover and the spatial autocorrelation of abundances, and can be predicted using this information. The theory therefore provides a direct link between SADs and the spatial correlation structure of species distributions, and thus between several fundamental descriptors of community structure. Moreover, the statistical process described may lie behind similar frequency distributions observed in many other scientific fields