Tropical forest degradation in the context of climate change: increasing role and research challenges. [K-2215-01]

While developed countries in temperate regions faced their forest transition about 100 years ago or more, “tropical forest rich” nations still largely depend on forest resources or land clearing for their development. Hence, tropical forests are retreating at an alarming rate from advancing cash crops, such as oil palm, soybean, or cattle ranching. Beside tropical deforestation, tropical forest degradation resulting mostly from human-induced causes (e.g. predatory or illegal logging, non-timber forest product extraction, fuel wood extraction) significantly contributes to greenhouse gas emissions and loss of biodiversity. If deforestation is an obvious ecosystem change, forest degradation is more difficult to discern and quantify. Degraded forests have become a major component of today's tropical landscapes, representing up to 50 % of all tropical forests. For example, almost half of standing primary tropical forests, up to 400 million ha, are designated by national forest services for timber production. The portion of tropical forests managed for timber extraction, hereafter referred to as “managed forests”, will therefore play key roles in the trade-off between provision of goods and maintenance of carbon stocks, biodiversity, and other services. However, so far, most of our understanding of tropical forest arise from studies carried out in old-growth undisturbed forests, or secondary forests (i.e. regrowth forests) while the ecology of degraded forests at the regional and continental scale remains poorly studied and their role to mitigate climate change still very poorly known. However, understanding the functions played by degraded forests in providing goods and environmental services in the context of climate change is crucial. We will first discuss the complex concept of forest degradation in the tropics and then define degraded forests. We will show their importance in providing timber while maintaining high levels of biodiversity and carbon stocks. We will further demonstrate that implementation of sustainable forest management can promote long term provision of ecosystem services. Finally, the potential of tropical degraded forests in mitigating climate change will be discussed along with future research challenges on this issue. (Texte intégral

Five-dimensional Superfield Supergravity

We present a projective superspace formulation for matter-coupled simple supergravity in five dimensions. Our starting point is the superspace realization for the minimal supergravity multiplet proposed by Howe in 1981. We introduce various off-shell supermultiplets (i.e. hypermultiplets, tensor and vector multiplets) that describe matter fields coupled to supergravity. A projective-invariant action principle is given, and specific dynamical systems are constructed including supersymmetric nonlinear sigma-models. We believe that this approach can be extended to other supergravity theories with eight supercharges in $D\leq 6$ space-time dimensions, including the important case of 4D N=2 supergravity.Comment: 18 pages, LaTeX; v2: comments added; v3: minor changes, references added; v4: comments, reference added, version to appear in PL

Tranquillisation, sédation et anesthésie des bovidés sauvages en parcs zoologiques

Aujourd’hui toutes les espèces de grands singes sont menacées d’extinction. Les parcs zoologiques participent à leur conservation et à l’éducation du public. Afin de remplir au mieux ces missions, le zoo AFRICAN SAFARI envisage la création d’enclos de type île pour accueillir des pongidés (chimpanzé commun Pan troglodytes, gorille des plaines de l’Ouest Gorilla gorilla gorilla et orang-outan de Bornéo Pongo pygmaeus) dans des conditions optimales de bien-être et de manière esthétique. Après avoir présenté ces espèces, l’auteur précise les recommandations concernant l’hébergement de ces singes sur des îles ainsi que les principes de bien-être et d’enrichissement. Le projet d’AFRICAN SAFARI est aussi exposé. Les résultats d’une enquête sur les îles pour grands primates, menées auprès de zoos européens, sont ensuite rapportés. Ces enclos présentent un réel intérêt pour héberger gorilles et orangs-outans mais ne semblent pas être indiqués pour accueillir de manière sûre des chimpanzés

GUYAFOR: a network of research permanent plots of tropical forests in French Guiana

GUYAFOR, a network of forest research permanent plots, is dedicated to long term studies in forest dynamics and biodiversity. Forest plots have been established in French Guyana from the late 60's to recent years by Cirad, ONF and CNRS. From 2000, they are progressively integrated in the GUYAFOR network with standardized protocols for both tree inventories and environmental characterization. The network includes 45 plots distributed on 10 sites mainly in the coastal area.157 800 trees above 10 cm dbh are monitored within 235 ha at regular intervals (2 to 4 years). Undisturbed forests are monitored on all sites. Forests subjected to different logging treatments are also monitored on four sites (Paracou, Organabo, Risquetout and Montagne Tortue), providing a unique feature to this network. Recent works carried out on the Guyafor network include studies to understand patterns of tree biological diversity at specific, functional and evolutionary levels and studies on the effects of logging practices on the carbon cycle. (Résumé d'auteur

Estimates of genetic differentiation measured by FST do not necessarily require large sample sizes when using many SNP markers

Population genetic studies provide insights into the evolutionary processes that influence the distribution of sequence variants within and among wild populations. FST is among the most widely used measures for genetic differentiation and plays a central role in ecological and evolutionary genetic studies. It is commonly thought that large sample sizes are required in order to precisely infer FST and that small sample sizes lead to overestimation of genetic differentiation. Until recently, studies in ecological model organisms incorporated a limited number of genetic markers, but since the emergence of next generation sequencing, the panel size of genetic markers available even in non-reference organisms has rapidly increased. In this study we examine whether a large number of genetic markers can substitute for small sample sizes when estimating FST. We tested the behavior of three different estimators that infer FST and that are commonly used in population genetic studies. By simulating populations, we assessed the effects of sample size and the number of markers on the various estimates of genetic differentiation. Furthermore, we tested the effect of ascertainment bias on these estimates. We show that the population sample size can be significantly reduced (as small as n = 4–6) when using an appropriate estimator and a large number of bi-allelic genetic markers (k.1,000). Therefore, conservation genetic studies can now obtain almost the same statistical power as studies performed on model organisms using markers developed with next-generation sequencing

On the statistics of magnetotelluric rotational invariants

Author Posting. © Author, 2013. This article is posted here by permission of Oxford University Press on behalf of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 196 (2014): 111-130, doi:10.1093/gji/ggt366.The statistical properties of the Swift skew, the phase-sensitive skew and the WAL invariants I1−I7 and Q are examined through analytic derivation of their probability density functions and/or simulation based on a Gaussian model for the magnetotelluric response tensor. The WAL invariants I1−I2 are shown to be distributed as a folded Gaussian, and are statistically well behaved in the sense that all of their moments are defined. The probability density functions for Swift skew, phase-sensitive skew and the WAL invariants I3−I4, I7 and Q are derived analytically or by simulation, and are shown to have no moments of order 2 or more. Since their support is semi-infinite or infinite, they cannot be represented trigonometrically, and hence are inconsistent with a Mohr circle interpretation. By contrast, the WAL invariants I5−I6 are supported on [ − 1, 1], and are inferred to have a beta distribution based on analysis and simulation. Estimation of rotational invariants from data is described using two approaches: as the ratio of magnetotelluric responses that are themselves averages, and as averages of section-by-section estimates of the invariant. Confidence intervals on the former utilize either Fieller's theorem, which is preferred because it is capable of yielding semi-infinite or infinite confidence intervals, or the less accurate delta method. Because section-by-section averages of most of the rotational invariants are drawn from distributions with infinite variance, the classical central limit theorem does not pertain. Instead, their averaging is accomplished using the median in place of the mean for location and an order statistic model to bound the confidence interval of the median. An example using real data demonstrates that the ratio of averages approach has serious systematic bias issues that render the result physically inconsistent, while the average of ratios result is a smooth, physically interpretable function of period, and is the preferred approach.Supported by NSF grant EAR101518

A seed-diffusion model for tropical tree diversity patterns

Diversity patterns of tree species in a tropical forest community are approached by a simple lattice model and investigated by Monte Carlo simulations using a backtracking method. Our spatially explicit neutral model is based on a simple statistical physics process, namely the diffusion of seeds. The model has three parameters: the speciation rate, the size of the meta-community in which the studied tree-community is embedded, and the average surviving time of the seeds. By extensive computer simulations we aim the reproduction of relevant statistical measures derived from the experimental data of the Barro Colorado Island tree census in year 1995. The first two parameters of the model are fixed to known values, characteristic of the studied community, thus obtaining a model with only one freely adjustable parameter. As a result of this, the average number of species in the considered territory, the relative species abundance distribution, the species-area relationship and the spatial auto-correlation function of the individuals in abundant species are simultaneously fitted with only one parameter which is the average surviving time of the seeds.Comment: 12 pages, 5 figure

Factors Associated With Readmission Of Patients With Congenital Heart Disease In A Swiss University Hospital

ABSTRACT Background: Congenital heart defects (CHD) are a common congenital anomaly that leads to extensive use of healthcare resources, yet there is little information available on the rates of readmission or the factors that predispose to readmission within 30 days of discharge. We sought to evaluate!the rate of readmission among patients with CHD and to analyse the factors associated with! readmission. Methods: Retrospective study using data concerning all patients with an ICD=10 code from Q20 to Q25 hospitalised between 2002 and 2014 at the University Hospital of Lausanne. Readmission and association with socio-clinical factors were evaluated for all non-humanitarian patients under the age of 18. Results: 996 patients younger than 18 were hospitalised for CHD, 332 undergoing surgery. 96 patients (9.6%) were readmitted within 30 days of discharge, 83 (86.5%) cardiac causes. Median time to readmission was 10 days (interquartile range: 6 - 20) and median length of readmission was 12 days (interquartile range: 6 - 20). Foreign nationality, greater distance to hospital, and length of index hospitalisation < 14 days predisposed to readmission. Patients who underwent surgery were less likely to be readmitted (8.7%). Conclusion: Readmissions were frequent, almost 1 in 10 patients, and associated with several socio- clinical factors. Providing patients who live far from hospital with specialized care closer to home may help reduce the rate of readmission