Selection of hardwood saplings by European roe deer: Effects of variation in the availability of palatable species and of understory vegetation

L'alimentation du chevreuil (Capreolus capreolus) dans les forêts européennes de production a des conséquences financières importantes. Le chêne (Quercus robur, Q. pedunculatus) et le charme (Carpinus betulus) font partie des espèces communément consommées et souffrent de niveaux de dégâts élevés. Dans cet article, nous testons l'hypothèse que les préférences alimentaires du chevreuil dépendent de la fréquence de présence des espèces. Dans la première expérience, le charme et le cornouiller (Cornus sanguinea) sont offerts en proportions variables de 2/8 à 8/2 : le charme est préféré et le degré de préférence n'est pas affecté par son abondance relative. Dans la deuxième expérience, le chêne, le hêtre (Fagus sylvatica) et l'érable (Acer pseudoplatanus) sont offerts dans des conditions plus naturelles (plantation) avec une végétation d'accompagnement abondante ou rare. La consommation de chêne diminue quand la végétation d'accompagnement est abondante; mais son abondance relative par rapport aux autres plants n'a pas d'effet sur le degré de préférence. La sélection alimentaire chez le chevreuil n'apparaît pas être dépendante de la fréquence des espèces : certaines conclusions sont tirées pour la gestion des plantations forestières

Spatial variation in springtime food resources influences the winter body mass of roe deer fawns. Oecologia 137

Abstract It is well established that the dynamics of mammalian populations vary in time, in relation to density and weather, and often in interaction with phenotypic differences (sex, age and social status). Habitat quality has recently been identified as another significant source of individual variability in vital rates of deer, including roe deer where spatial variations in fawn body mass were found to be only about a tenth of temporal variations. The approach used was to classify the habitat into blocks a priori, and to analyse variation in animal performance among the predefined areas. In a fine-grained approach, here we use data collected over 24 years on 1,235 roe deer fawns captured at known locations and the plant species composition sampled in 2001 at 578 sites in the ChizØ forest to determine the spatial structure at a fine scale of both vegetation and winter body mass of fawns, and then to determine links between the two. Space and time played a nearly equal role in determining fawn body masses of both sexes, each accounting for about 20% of variance and without any interaction between them. The spatial distribution of fawn body mass was perennial over the 24 years considered and predicted values showed a 2 kg range according to location in the reserve, which is much greater than suggested in previous work and is enough to have strong effects on fawn survival. The spatial distribution and the range of predicted body masses were closely similar in males and females. The result of this study is therefore consistent with the view that the life history traits of roe deer are only weakly influenced by sexual selection. The occurrence of three plant species that are known to be important food items in spring/summer roe deer diets, hornbeam (Carpinus betulus), bluebell (Hyacinthoides sp.) and Star of Bethlehem (Ornithogalum sp.) was positively related to winter fawn body mass. The occurrence of species known to be avoided in spring/summer roe deer diets [e.g. butcher's broom (Ruscus aculeatus) and beech (Fagus sylvatica)], was negatively related to fawn body mass. We conclude that the spatial variation in the body mass of fawns in winter in this forest is as important as the temporal variation, and that the distribution of plant species that are actively selected during spring and summer is an important determinant of spatial variation in winter fawn body mass. The availability of these plants is therefore likely to be a key factor in the dynamics of roe deer populations

Selection of hardwood saplings by European Roe Deer : effects of variation in the availability of palatable species and of understory vegetation

Feeding by Roe Deer (Capreolus capreolus) in European commercial forests has important financial costs. Oak (Quercus robur, Q. pedunculatus) and hornbeam (Carpinus betulus) are commonly among the preferred species, and suffer high levels of damage. In this paper we test the hypothesis that selection is frequency-dependent. In one experiment, hornbeam was offered together with dogwood (Cornus sanguined) in proportions varying from 2/8 to 8/2 : hornbeam was preferred and the degree of preference was not affected by its relative abundance. In a second experiment the Deer were offered oak, beech (Fagus sylvatica) and sycamore (Acer pseudoplatanus) in more natural conditions with sparse or dense understory vegetation. The consumption of oak decreased when the understory vegetation was dense ; but its availability relative to the other saplings had no effect on the degree of preference. Food selection in Roe Deer appears not to be frequency-dependent. Some conclusions for the management of hardwood plantations are drawn.L’alimentation du chevreuil (Capreolus capreolus) dans les forêts européennes de production a des conséquences financières importantes. Le chêne (Quercus robur, Q. pedunculatus) et le charme (Carpinus betulus) font partie des espèces communément consommées et souffrent de niveaux de dégâts élevés. Dans cet article, nous testons l’hypothèse que les préférences alimentaires du chevreuil dépendent de la fréquence de présence des espèces. Dans la première expérience, le charme et le cornouiller (Cornus sanguinea) sont offerts en proportions variables de 2/8 à 8/2 : le charme est préféré et le degré de préférence n’est pas affecté par son abondance relative. Dans la deuxième expérience, le chêne, le hêtre (Fagus sylvatica) et l’érable (Acer pseudoplatanus) sont offerts dans des conditions plus naturelles (plantation) avec une végétation d’accompagnement abondante ou rare. La consommation de chêne diminue quand la végétation d’accompagnement est abondante ; mais son abondance relative par rapport aux autres plants n’a pas d’effet sur le degré de préférence. La sélection alimentaire chez le chevreuil n’apparaît pas être dépendante de la fréquence des espèces : certaines conclusions sont tirées pour la gestion des plantations forestières.Tixier Hélène, Duncan Patrick, Ballon Philippe, Guillon Noël, Guillon Nadine. Selection of hardwood saplings by European Roe Deer : effects of variation in the availability of palatable species and of understory vegetation. In: Revue d'Écologie (La Terre et La Vie), tome 53, n°3, 1998. pp. 245-253

Assessment of forage availability in ecological studies

International audienceIn this study we describe and calibrate a quantitative index method to estimate leaf biomass and forage availability for browsers at different feeding heights. The method is based on an index relating leaf biomass to a number of leaf contacts with a vertical, three-dimensional (25×25×165 cm) metallic quadrat with a central rod and takes into account the characteristics of leaves (shape, size, and thickness) to define plant categories and then produce general allometric equations per category. We then discuss the use of this biomass index to evaluate the quality of habitats for browsers in terms of food resources

Cellulose Conversion with Tungstated-Alumina-Based Catalysts: Influence of the Presence of Platinum and Mechanistic Studies

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Cellulose reactivity and glycosidic bond cleavage in aqueous phase by catalytic and non catalytic transformations

International audienceA key challenge for the next decades is to develop effective, safe, environmental friendly and economic technologies to convert lignocellulosic biomass into target molecules. The catalytic transformation of cellulose in aqueous phase is a promising way to obtain valuable products.This short review highlights different aspects related to this process from cellulose nature to its reactivity in various operating conditions. Focus will be made on recent advances dealing with use of heterogeneous catalysis for cellulose transformation

Cellulose hydrothermal conversion promoted by heterogeneous Brønsted and Lewis acids: Remarkable efficiency of solid Lewis acids to produce lactic acid

International audienceCrystalline cellulose treated in hydrothermal conditions (190 °C, 24 h) is partially solubilised, 30%, into water soluble oligosaccharides/polymers with the formation of small amounts of glucose and 5-HMF. In the presence of solid Brønsted catalysts such as Cs2HPW12O40 and HY zeolite, the extent of the cellulose depolymerisation was not changed when no leaching occurred. However, a quite different products distribution was obtained, in favour of further transformations of glucose and HMF in levulinic and formic acids. On the opposite, solid Lewis acids such as tungstated zirconia (ZrW) and tungstated alumina (AlW) exhibited a remarkable promoting effect on the cellulose depolymerisation which was raised up to 45% while an unexpected decrease of the proportion of water soluble oligosaccharides/polymers was observed. Yields of 27 mol% and 18.5 mol% in lactic acid were achieved on AlW and ZrW, respectively. Moreover, these tungsten based Lewis acids exhibited a good stability and recyclability. The efficiency of the solid Lewis acids ZrW and AlW to produce lactic acid directly from crystalline cellulose was explained by a positive synergy between water autoprotolysis responsible of the cellulose depolymerisation into soluble intermediates which are further converted on the solid Lewis catalyst surface

Conversion of cellulose to 2,5-hexanedione using tungstated zirconia in hydrogen atmosphere

SSCI-VIDE+CDFA+CPI:NES:FRA:FCMInternational audience2,5 hexadione is produced from cellulose using ZrW in the presence of hydrogen while lactic acid is the main product in helium atmosphere. FTIR and kinetics studies strengthened the proposed mechanism which involves as important elementary steps hydroxyls abstractions and hydride transfers promoted by the Lewis acid sites of ZrW. Moreover the important increase of cellulose conversion in the presence of ZrW in hydrogen atmosphere was explained by the likely formation of additional Bronsted acid sites formed by hydrogen interacting with ZrW which catalyze the protolysis of the glycosidic bonds in cooperation with the pool of hydroxonium ions provided by the self protolysis of water at 190°C