Quel est le coût des dégâts d'écorcement dans les plantations d'épicéa?

editorial reviewedLes dégâts d’écorcement sont particulièrement préjudiciables pour les plantations d’épicéa, première essence de production wallonne. Bien que l’occurrence des dégâts d’écorcement ait été objectivée avec des inventaires, l’ampleur de la perte financière n’avait pas été quantifiée précisément jusqu’à présent. D’après cette étude, le coût des dégâts serait d’environ 46 €/ha/an si le taux d’écorcement annuel est de 4 %, un taux qui était jugé jusqu’à présent comme acceptable. L’étude souligne également l’intérêt financier de la protection individuelle des arbres d’avenir au rabot de Gerstner, surtout dans les pessières les plus productives, ou si le rabotage peut être réalisé bien avant la première éclaircie

Are wild ungulates a threat for the forest diversity?

Les ongulés sauvages interfèrent avec la dynamique forestière en modifiant les avantages concurrentiels des espèces en cours de régénération. Le monitoring d'un réseau d'enclos-exclos à l'échelle régional dans les hêtraies-chênaies d'Ardenne a permis de mettre en évidence la nature de ces impacts. Les ongulés favorisent les essences climaciques au détriment des essences liées aux stades moins avancés de la succession. Ces impacts vont à l'encontre d'objectifs de gestion visant à diversifier les forêts. Les essences défavorisées ont une régénération déficitaire depuis des décennies. Ces impacts réduisent également la résilience des forêts face à l'augmentation des températures et des épisodes de déficit hydrique.15. Life on lan

Wherever I may roam-Human activity alters movements of red deer (Cervus elaphus) and elk (Cervus canadensis) across two continents

Human activity and associated landscape modifications alter the movements of animals with consequences for populations and ecosystems worldwide. Species performing long-distance movements are thought to be particularly sensitive to human impact. Despite the increasing anthropogenic pressure, it remains challenging to understand and predict animals' responses to human activity. Here we address this knowledge gap using 1206 Global Positioning System movement trajectories of 815 individuals from 14 red deer (Cervus elaphus) and 14 elk (Cervus canadensis) populations spanning wide environmental gradients, namely the latitudinal range from the Alps to Scandinavia in Europe, and the Greater Yellowstone Ecosystem in North America. We measured individual-level movements relative to the environmental context, or movement expression, using the standardized metric Intensity of Use, reflecting both the directionality and extent of movements. We expected movement expression to be affected by resource (Normalized Difference Vegetation Index, NDVI) predictability and topography, but those factors to be superseded by human impact. Red deer and elk movement expression varied along a continuum, from highly segmented trajectories over relatively small areas (high intensity of use), to directed transitions through restricted corridors (low intensity of use). Human activity (Human Footprint Index, HFI) was the strongest driver of movement expression, with a steep increase in Intensity of Use as HFI increased, but only until a threshold was reached. After exceeding this level of impact, the Intensity of Use remained unchanged. These results indicate the overall sensitivity of Cervus movement expression to human activity and suggest a limitation of plastic responses under high human pressure, despite the species also occurring in human-dominated landscapes. Our work represents the first comparison of metric-based movement expression across widely distributed populations of a deer genus, contributing to the understanding and prediction of animals' responses to human activit

Wherever I may roam—Human activity alters movements of red deer (Cervus elaphus) and elk (Cervus canadensis) across two continents

Human activity and associated landscape modifications alter the movements of ani-mals with consequences for populations and ecosystems worldwide. Species perform-ing long-distance movements are thought to be particularly sensitive to human impact. Despite the increasing anthropogenic pressure, it remains challenging to understand and predict animals' responses to human activity. Here we address this knowledge gap using 1206 Global Positioning System movement trajectories of 815 individuals from 14 red deer (Cervus elaphus) and 14 elk (Cervus canadensis) populations spanning wide environmental gradients, namely the latitudinal range from the Alps to Scandinavia in Europe, and the Greater Yellowstone Ecosystem in North America. We measured individual-level movements relative to the environmental context, or movement ex-pression, using the standardized metric Intensity of Use, reflecting both the directional-ity and extent of movements. We expected movement expression to be affected by resource (Normalized Difference Vegetation Index, NDVI) predictability and topogra-phy, but those factors to be superseded by human impact. Red deer and elk movement expression varied along a continuum, from highly segmented trajectories over relatively small areas (high intensity of use), to directed transitions through restricted corridors (low intensity of use). Human activity (Human Footprint Index, HFI) was the strong-est driver of movement expression, with a steep increase in Intensity of Use as HFI increased, but only until a threshold was reached. After exceeding this level of impact, the Intensity of Use remained unchanged. These results indicate the overall sensitivity of Cervus movement expression to human activity and suggest a limitation of plastic responses under high human pressure, despite the species also occurring in human-dominated landscapes. Our work represents the first comparison of metric- based movement expression across widely distributed populations of a deer genus, contribut-ing to the understanding and prediction of animals' responses to human activity.publishedVersio

Mammal responses to global changes in human activity vary by trophic group and landscape

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.Peer reviewe

An exclosure experiment to assess the impact of ungulates on plant diversity in Belgium

The erosion of biodiversity is caused by many factors. Large ungulates, which occupy a large part of the Walloon forests, can also influence the distribution and dynamics of plant species. Therefore, they impact the biodiversity of our temperate forests. The aim of the present study is to identify changes in forest understory vegetation due to the pressure exerted by wild ungulates thanks to an exclosure-enclosure experiment. This study was conducted on a high plateau of the Ardenne, in the forest of St Michel Freyr (South Belgium). The forested area is dominated by beech and spruce where red deer, wild boar and roe deer are living in sympatry. 150 sampling plots were established in 2000. Each plot consisted of two closed enclosures of 4 m² each and one exclosure of 4 m² as control under pressure of ungulates. Sampling was carried out systematically by a 500m-square mesh. The cover rate and height of some easily identifiable species were measured regularly since 2000 (2001, 2002, 2003, 2004, 2007, 2011-2012). In addition, we identified each herbaceous species in 2011-2012 to analyze the species richness after more than 10 years exclosure. Ligneous species showed an increase of developpement in the fenced area. These species are more impacted when they are not much represented in the study site.Species richness and diversity are higher in areas impacted by herbivory. Monocotyledons are mainly favorised while tree seedlings are unfavorised. Browsing on the trees keeps the area free from high vegetation and allows light to reach the ground. In the same time, herbaceous species have a lower cover rate in the enclosure because of the competitive exclusion induced by shrub and tree seedlings layer. If the apparition of most species is favorised by ungulates, they induce a lag of gowth on dicotyledons which have a higher palatability than monocotyledons. Ungulates have the ability to impact the distribution of vegetal species by the modification of the competitive interaction. By their pressure on tree and shrub species, they induce a higher diversity of the ground flora. However, this change in vegetation composition is slow and requires a long-term studie, specially in areas of low biomass productivity like the St-Hubert forest

LES ENCLOS-EXCLOS : UNE TECHNIQUE ÉPROUVÉE POUR L’ÉVALUATION ET LE MONITORING DE L’ÉQUILIBRE FORÊT-GRANDE FAUNE

Afin d’objectiver l’équilibre entre la flore et la grand faune d’un territoire, l’installation d’un réseau d’enclos-exclos présente l’avantage d’être à la fois scientifiquement robuste et visuellement parlant. Il a été testé sur le cantonnement de Florenville, sur deux territoires à la pression de gibier contrastée.During the last decades, populations of large ungulate herbivores have increased and their influence on forest vegetation have been clearly highlighted. Therefore, monitoring game pressure have become unavoidable for sustainable forest management. Such monitoring require a rigorous approach in order to evaluate objectively the forest-game balance. Under these conditions, the use of exclosure experiment has appeared an interesting solution. They enable to observe the ecosystem evolution due to forest-game imbalance as well as to detect any early deterioration of a situation that was initially considered acceptable. The enclosure-exclosure devices compare, on the one hand, the real environment (exclosure) fully accessible by wildlife and, secondly, a “control” fenced habitat (enclosures) inaccessible to all populations of large ungulates (e.g. wild boar, red deer, roe deer and mouflon). In 2006, enclosure-exclosure devices (4 x 4 m) were installed within forest gaps in order to monitore the understory dynamic in Wallonia. Observations were collected until 2012 and we computed a set of indicators characterizing the ecological changes due to large herbivores pressure on forest ecosystems. Such devices played a key educational role as it provide a visual comparison of two contrasted situations. Additionally, quantitative information were collected to perform further analysis (floristic survey, as well as height, number of stems and the cover of vegetation). We identified indicators of the ecological changes that responded within two years whereas other indicators required at least 4 monitoring years in order to quantify correctly herbivore pressure. Short-term indicators allow a rapid detection, but they have the disadvantage of being very sensitive to exogenous factors (climate changes, site conditions). At the opposite, medium-term indicators, such as regeneration growth, require a longer monitoring period, but they are more robust (mitigation interannual variations of environmental factors) than the short-term indicators. We evaluated the relative efficiency of various indicators using 17 enclosures distributed in two zones with contrasted deer densities. Some of the tested indicators allowed detecting significant differences between the two zones (Student's t test). In particular, among the short-term indicators we obtained significant result with the ground vegetation richness, regeneration richness, seedling density and height of Rubus fruticosus L. and Rubus idaeus L.. Among the medium-term indicators, the most relevant indicators were the average height of beech and birch, ground vegetation richness, seedling density and total cover of vegetation

Analyse spatio-temporelle des dégâts d'écorcement dans les plantations résineuses en Région Wallonne

Les dégâts d’écorcement inquiètent de très nombreux gestionnaires forestiers. Depuis plus de 10 ans, des inventaires sont réalisés annuellement et des outils de diagnostic ont été développés afin d’en quantifier l’ampleur en Région wallonne. L’examen de ces données met en évidence le rôle prépondérant des densités de cerfs ainsi que de la structure du paysage, de la rigueur des hivers et de la capacité d’accueil du milieu

Assessment and monitoring of forest-game balance: an exclosure experiment

During the last decades, populations of large ungulates have largely increased, strengthening the pressure exerted by these species on forest vegetation. Therefore, monitoring this pressure has become unavoidable for sustainable forest management. Such monitoring requires a rigorous approach in order to evaluate objectively the balance between game population and forestry. The use of exclosure experiment offers an interesting solution to observe the effects of game populations on forest ecosystem. When objectives expected from forest management are clearly defined, exclosure experiments can effectively be used as a monitoring tool, to allow detecting unbalanced situations, for example, herbivore pressure threatening forest regeneration. The monitoring tool combines on one side an exclosure, defined as "the real environment", fully accessible to herbivores and, on the other side an enclosure, which is the "control treatment", fenced and therefore unavailable to any large ungulates. Our main aim was to compute a set of indicators characterizing the ecological changes due to large herbivores pressure on forest ecosystems. We identified 2 categories of ecological indicators: the short-term and the medium-term indicators. Short-term indicators require only two-year of monitoring to correctly quantify herbivore pressure whereas medium-term indicators require at least 4 years of monitoring. The study site is located in Southern Belgium (Wallonia), in mixed beech and oak forests. The predominant vegetation type is the "Luzulo-Fagetum", typically found in acidophileous beech forests. The ungulate species of interest are red deer, roe deer, wild boar and mouflon. In 2006, enclosures and exclosures (4 x 4 m) were installed in 17 sites scattered in two zones with contrasted deer densities to assess indicators efficiency. Between 2006 and 2012, we performed floristic surveys and we recorded the height, density and cover of the understory vegetation of every plot