Landscape scenario modelling of vegetation condition

Summary   Landscape scenario modelling is a useful aid to planning for biodiversity conservation. Vegetation condition modelling is increasingly being integrated into such analysis. Model complexity and model uncertainty are critical factors that must be addressed when tailoring vegetation condition modelling to individual applications. We describe three approaches that we have used to compare the effects of different landscape scenarios on vegetation condition. The first is a simple land-use–condition approach where vegetation condition is determined solely by land use. The second is a land-use–regeneration approach that introduces transition functions to model vegetation condition dynamics associated with land use change. The third is a threat–regeneration approach, which models vegetation condition dynamics based on the interaction between regeneration and a range of mapped threats. The three approaches represent a progression towards increased refinement and realism, but also increased complexity and data requirements. We examine the relative usefulness of the three approaches and conclude that there is no single 'silver bullet' solution but recommend judicious matching of approaches to applications within a collaborative and adaptive setting.     

The optimal tomotherapy treatment planning parameters for extremity soft tissue sarcomas

Background and purposeTo determine the optimum combination of treatment parameters between pitch, field width (FW) and modulation factor (MF) for extremity sarcomas in tomotherapy.Materials and methodsSix patients previously treated for extremity sarcomas (3 arms and 3 legs) with tomotherapy were included in this study. 288 treatment plans were recalculated, corresponding to all combinations between 2 FW (2.5 and 5 cm), 4 MF (1.5, 2, 2.5 and 3) and 6 pitches (0.215, 0.287, 0.43 and 3 off-axis pitches). The treatment parameters (MF, FW or pitch) are modified between each plan, and the calculation is relaunched for 400 iterations, without modifying the optimisation constraints of the plan under which the patient has been treated.ResultsWe suggest eliminating the 0.43 pitch and never combining a 0.215 pitch with an MF ≤ 2. We also do not recommend using an MF = 1.5 unless treatment time is an absolute priority over plan quality. We did not see any advantage in using Chen off-axis pitches, except for targets far from the axis (>15 cm) treated with a high pitch. A combination of MF = 2/FW = 5 cm/pitch = 0.287 gives plans of acceptable quality, combined with reduced treatment times. These conclusions are true only for extremity sarcomas treated in 2 Gy/fraction.ConclusionsWe have shown that the choice of pitch/MF/FW combination is crucial for the treatment of extremity sarcomas in tomotherapy: some produce good dosimetric quality with a reduced irradiation time, while others may increase the time without improving the quality.     

Doomed to die? Predicting extinction risk in the true hawks Accipitridae

One of the most important tasks in conservation biology is identifying species at risk from extinction and establishing the most likely factors influencing this risk. Here, we consider an ecologically well-defined, monophyletic group of organisms, the true hawks of the family Accipitridae, which are not only among the most studied, but also contain some of the rarest bird species in the world. We investigate which intrinsic and extrinsic factors, covering morphology, life history and ecology, covary with International Union for the Conservation of Nature and Natural Resources threat status, as well as global population size and geographic range size. By decomposing threat status into population size and range size, we test whether any factors are generally important: we found that species with less habitat specialization, a larger clutch size and more plumage polymorphism were associated with lower extinction risk and larger population and range sizes. Species with special habitat requirements might be less capable of dealing with habitat transformation and fragmentation, while species with small clutch sizes might not be able to reverse population declines. Plumage polymorphism might indicate the size of the species' gene pool and could be a good marker of extinction risk. The analyses also emphasized that no single factor is likely to be sufficient when predicting the threat of extinction.     

Some Approximations of the Borel-Tanner or the Generalized Poisson Distribution

This paper considers some approximations for the Borel-Tanner (Generalized Poisson) sums by using (i) Gram-Charlier Poisson expansion, (ii) Mixture of two Poisson distributions, (iii) Variance stabilizing technique, and (iv) negative binomial distribution. It has been found that the approximation obtained by using the negative binomial distribution seems to be more efficient than the other approximation.     

Biomimetic nitration of the linoleic acid metabolite 13-hydroxyoctadecadienoic acid: isolation and spectral characterization of novel chain-rearranged epoxy nitro derivatives

Nitration of unsaturated fatty acids is a (patho)physiologically important pathway of lipid modification induced by nitric oxide-derived species. We report herein on the unexpected chain rearrangement undergone by (13S,9Z,11E)-13-hydroxyoctadeca-9,11-dienoic acid (1), a linoleic acid metabolite, when exposed to nitrating agents of biological relevance. At pH 7.4 and at room temperature, reaction of 1 with peroxynitrite (ONOO-) as well as Fe2+-EDTA/H2O2/NO2- and horseradish peroxidase/H2O2/NO2- led to the formation of two nitration products, which could be isolated as the methyl esters and were identified as diastereoisomeric methyl (12S)-10,11-epoxy-12-hydroxy-9-nitromethylheptadecanoates by extensive 1H, 13C, 15N NMR and MS analysis.     

Breeding abundance of threatened raptors as estimated from occurrence data

A model derived from the negative binomial distribution (NBD) has been proposed to solve the problem of predicting abundance of species from occurrence maps. The viability of NBD was explored for predicting the breeding abundance of five threatened species of raptor: Bonelli's Eagle Hieraaetus fasciatus, Golden Eagle Aquila chrysaetos, Peregrine Falco peregrinus, Lanner Falco biarmicus and Lesser Kestrel Falco naumanni. First, the accuracy of the NBD was tested in a reference area where the species abundance and occurrence were known through intensive field surveys. Next, an estimation of regional abundance derived from NBD was made for each species. These estimates were then compared to the existing regional data for the five raptors. The spatial distributions of the species were strongly aggregated, with F. peregrinus correctly showing the most widespread area of occupancy. The NBD gave a good approximation of the breeding abundance of the raptors, but tended to overestimate real data, particularly the regional data for falcons. Difficulties in species detection, insufficient sampling effort (F. biarmicus) or data collected over long time spans when population size increased (F. naumanni) may have reduced the NBD's resolution power. The ability of the method to predict local abundances over large areas from readily available presence‐absence data, with relatively low fieldwork effort, could have considerable applications in conservation biology.