Modeling recent bark stripping by red deer (Cervus elaphus) in South Belgium coniferous stands

? Context

Over the past few decades, the impact of large herbivorous ungulates on forest vegetation has been clearly highlighted. Among those impacts, bark stripping of coniferous trees is one of the most damaging. Bark stripping leads to rot development, inducing serious loss of timber value.

? Aims

The present study aimed firstly at evidencing the factors explaining the variations observed in fresh bark peeling rate for spruce and Douglas-fir in southern Belgium and secondly at identifying the key factors to consider when setting up a deer management plan.

? Method

Fresh bark peeling rate was recorded with a systematic sampling survey from 2004 to 2007. The covered territory was then divided into 63 distinct hunting zones of area ranging from 1,000 to 25,000 ha. About 5,000 plots were monitored annually. Each zone was characterized with a large number of explanatory variables. The explanatory variables were integrated firstly into fixed linear models using a stepwise procedure, and then into a mixed model.

? Results

The significant variables included in the model (R ²?=?44 %) are (by decreasing order of importance) red deer densities, proportion of coniferous stands and agricultural areas, snow cover, distance to urban habitats, and species diversity in the understory.

? Conclusion

The models revealed the impacts of several factors on bark peeling: deer density, deer-carrying capacity of the territory, landscape structure, and severity of winter conditions. The adjusted model allowed subtracting the impact of winter conditions in order to produce a relevant indicator for hunting management. In addition, the model was used to assess the sensitivity of a forested area to bark peeling based on its environmental characteristics.     

Effects of silage preservation on astaxanthin forms and fatty acid profiles of processed shrimp (Pandalus borealis) waste

Acid silage of shellfish processing waste has been reported to be a good and economical technique to protect these biomasses from bacterial decomposition. Shrimp (Pandalus borealis) by-products contain some value-added nutrients for the aquaculture industry such as carotenoid pigments (mainly astaxanthin) and n − 3 polyunsaturated fatty acids. The aim of this work was to determine the effect of ensiling shrimp waste during a long period of time (more than 3 months) on some unstable components such as the astaxanthin forms (free, mono- and diesterified) and polyunsaturated fatty acids. Comparisons of astaxanthin forms and the fatty acid profiles were performed on defrosted shrimp waste and on a 14-week-old shrimp waste silage. No significant difference (P ≥ 0.05) in the total lipids extracted from the two forms of shrimp waste was observed. Nevertheless, a small quantity of the red pigment, presumably an astaxanthin portion, was observed to stay firmly bound to the shrimp carapace after the solvent extraction in shrimp waste compared to the full recovery obtained in ensiled shrimp waste. This may explain the significantly (P < 0.05) higher concentration of total astaxanthin (4.57 vs 3.99 mg/g) found in the crude oil extracted from shrimp waste silage. Higher percentages (P < 0.01) of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were found in esterified astaxanthin from shrimp waste silage (43.9% and 45.5%) in comparison with their shrimp waste (24.7% and 20.3%) counterparts. This suggests that EPA and DHA are the principal fatty acids esterified with the portion of astaxanthin linked to chitin in the shrimp carapace. The utilization of shrimp waste silage as a pigmenting component of salmonid feeds is also discussed.     

Early infections by myxoma virus of young rabbits (Oryctolagus cuniculus) protected by maternal antibodies activate their immune system and enhance herd immunity in wild populations

The role of maternal antibodies is to protect newborns against acute early infection by pathogens. This can be achieved either by preventing any infection or by allowing attenuated infections associated with activation of the immune system, the two strategies being based on different cost/benefit ratios. We carried out an epidemiological survey of myxomatosis, which is a highly lethal infectious disease, in two distant wild populations of rabbits to describe the epidemiological pattern of the disease. Detection of specific IgM and IgG enabled us to describe the pattern of immunity. We show that maternal immunity attenuates early infection of juveniles and enables activation of their immune system. This mechanism associated with steady circulation of the myxoma virus in both populations, which induces frequent reinfections of immune rabbits, leads to the maintenance of high immunity levels within populations. Thus, myxomatosis has a low impact, with most infections being asymptomatic. This work shows that infection of young rabbits protected by maternal antibodies induces attenuated disease and activates their immune system. This may play a major role in reducing the impact of a highly lethal disease when ecological conditions enable permanent circulation of the pathogen.     

Size and dispersion of urticating setae in three species of processionary moths

Larvae of the processionary moths of the Palaearctic region bear urticating setae that are released against vertebrate predators, especially insectivorous birds. A few species are pests of forest and urban trees and, consequently, may threaten human and animal health during outbreaks, causing dermatitis, conjunctivitis and respiratory distress. Although some studies provide detailed information about the setae, particularly those of the pine processionary moth Thaumetopoea pityocampa, there is little knowledge on the morphological traits of the setae and their release by the larvae. In the present study we identify major traits of the setae of 3 species of processionary moth, T. pityocampa, T. pinivora and T. processionea, which are potentially helpful in the understanding of setae dynamics in the environment: (i) diameter and length of setae and (ii) analysis of dynamical properties of the setae in the airborne state. Setae are highly variable in size, with bimodal distribution in T. pityocampa and T. pinivora; in these 2 species, short and long setae are interspersed within the integument fields where they occur. The difference in the seta size has important consequences in dispersion, as smaller setae can spread 5 times further than their bigger counterparts. This information is relevant for a full understanding of the defensive importance of larval setae against natural enemies of the processionary moths, as well for elucidating the importance of the processionary setae as air pollutants, both close to the infested trees and at longer distances.     

Potential spread of the pine processionary moth in France: preliminary results from a simulation model and future challenges

Context

Some forest insect pests are currently extending their range as a consequence of climate warming. However, in most cases, the evidence is mainly based on correlations and the underlying mechanism is not clearly known.

Aims

One of the most severe pests of pine forests in Europe, the pine processionary moth, Thaumetopoea pityocampa, is currently expanding its distribution as a result of climate warming and does not occupy entirely its potential habitat. A model describing its spread was developed to simulate its potential range in France under various climate change scenarios.

Methods

The spread model was divided into several sub-models to describe the growth, survival and dispersal of the species. The model was validated on the observed change of species distribution, its sensitivity was tested, and spread scenarios were simulated for the future.

Results

The model shows that climate warming initiated the species range expansion in France since the early 1990s. The spread is now limited by dispersal capability, but human-mediated dispersal could accelerate the range expansion.

Conclusion

Species range expansion is an indicator of climate change. However, time lags can appear due to limited dispersal capabilities, and human-mediated dispersal could create satellite colonies and artificially accelerate the spread.     

Screening techniques and sources of resistance to foliar diseases caused by major necrotrophic fungi in grain legumes

Summary Necrotrophic pathogens of the cool season food legumes (pea, lentil, chickpea, faba bean and lupin) cause wide spread disease and severe crop losses throughout the world. Environmental conditions play an important role in the development and spread of these diseases. Form of inoculum, inoculum concentration and physiological plant growth stage all affect the degree of infection and the amount of crop loss. Measures to control these diseases have relied on identification of resistant germplasm and development of resistant varieties through screening in the field and in controlled environments. Procedures for screening and scoring germplasm and breeding lines for resistance have lacked uniformity among the various programs worldwide. However, this review highlights the most consistent screening and scoring procedures that are simple to use and provide reliable results. Sources of resistance to the major necrotrophic fungi are summarized for each of the cool season food legumes. Marker-assisted selection is underway for Ascochyta blight of pea, lentil and chickpea, and Phomopsis blight of lupin. Other measures such as fungicidal control and cultural control are also reviewed. The emerging genomic information on the model legume, Medicago truncatula, which has various degrees of genetic synteny with the cool season food legumes, has promise for identification of closely linked markers for resistance genes and possibly for eventual map-based cloning of resistance genes. Durable resistance to the necrotrophic pathogens is a common goal of cool season food legume breeders.     

Chemical compositions of the essential oils of the aerial parts of Chamaemelum mixtum (L.) Alloni

The chemical compositions of the aerial parts essential oils of Chamaemelum mixtum (L.) Alloni from Corsica and Sardinia were investigated employing gas chromatography and gas chromatography-mass spectrometry (GC-MS). The structure of (Z)-heptadeca-9,16-dien-7-one, a natural compound not previously described, was elucidated by GC-MS (electron impact and chemical ionization) and one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy. The variation in C. mixtum essential oil was studied, and statistical analysis showed the clustering of oil samples into three groups according to the amount of oxygenated compounds; these groups correlated to the harvest area. The strong biological activity of the oxygenated fraction (minimum inhibitory concentration of <0.1 mg/mL) of the Corsican oil against Candida albicans , Citrobacter frendii , Enterococcus faecalis , Escherichia coli , Klebsiella pneumoniae , Listeria monocytogenes , and Staphyllococcus aureus can be attributed to the presence of irregular monoterpene alcohols and (Z)-heptadeca-9,16-dien-7-one.     

Mars surface diversity as revealed by the OMEGA/Mars Express observations

The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) investigation, on board the European Space Agency Mars Express mission, is mapping the surface composition of Mars at a 0.3- to 5-kilometer resolution by means of visible-near-infrared hyperspectral reflectance imagery. The data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy, offering key insights into the evolution of Mars. OMEGA has identified and mapped mafic iron-bearing silicates of both the northern and southern crust, localized concentrations of hydrated phyllosilicates and sulfates but no carbonates, and ices and frosts with a water-ice composition of the north polar perennial cap, as for the south cap, covered by a thin carbon dioxide-ice veneer.     

Saharan wheats: before they disappear

Wheat landraces cultivated in the Saharan oases have been submitted during centuries to drought, heat and salinity and are expected to have developed tolerance to these constraints. The different forms present in the oases of Libya, Algeria and Morocco have been collected and described by several authors who highlighted the peculiarity and diversity of this germplasm, on the basis of spike and grain morphology. The origin, date and way of introduction of wheat in the Saharan oases are however largely unknown. Most landraces may have been introduced from Egypt, possibly during wet climatic episodes. Spike morphological traits of some landraces suggest an Asiatic origin (Iran, Turkestan and Afghanistan). More recent introductions have also probably occurred. This lack of information as well as the potential interest of this germplasm for wheat improvement would merit further studies. Marker-based diversity analysis of Saharan wheats and comparison with North-African and Asian wheats might permit to precise their classification and confirm their origin. Evaluation for tolerance to abiotic constraints would allow a better understanding of their adaptation to the oases environments and identification of potential progenitors to be used by wheat breeders. Such studies are urgent considering the quick genetic erosion of this germplasm due to drastic ecological and socio-economic changes affecting Saharan oases and their cropping systems.