Species variables or environmental variables as indicators of forest biodiversity: a case study using saproxylic beetles in Maritime pine plantations

To assess the sustainability of plantation forest management we compare two types of biodiversity indicators. We used the species richness of saproxylic beetles as a case study to test the “species” and “environmental” indicator approaches. We compared single species abundance or occurrence and deadwood volume or diversity as predictor variables. • Beetles were sampled with flight interception traps in 40 Maritime pine plantation stands. The volume and diversity of deadwood was estimated with line intersect and plot sampling in the same stands. Predictive models of species richness were built with simple linear or Partial Least Square regressions. • Deadwood variables appeared to be good predictors of saproxylic beetle richness at the stand-scale with at least 75% of variance explained. Deadwood diversity variables consistently provided better predictive models than volume variables. The best environmental indicator was the diversity of deadwood elements larger than 15 cm in diameter. • By contrast, the use of “species variables” appeared to be less relevant. To reach the quality of prediction obtained with “environmental variables”, the abundance or occurrence of 6 to 7 species – some of which are difficult to identify – had to be used to build the indicator

Concepts et méthodes de l’écologie des paysages pour aider à mieux gérer les services écosystémiques

Concepts et méthodes de l’écologie des paysages pour aider à mieux gérer les services écosystémique

Contribution à la connaissance des Coléoptères saproxyliques des forêts pyrénéennes : 3ème note : la forêt de Hèches, Hautes-Pyrénées

L’amélioration de la connaissance des cortèges de Coléoptères saproxyliques présents dans les forêts gérées des Pyrénées est un préalable indispensable à leur conservation. Dans le cadre d’une étude menée sur la propriété du Groupement Forestier de Hèches, un inventaire des Coléoptères saproxyliques a été conduit en 2003 et 2004, au moyen de pièges et de chasse à vue. Une liste de 374 taxons (espèces non-saproxyliques incluses) a ainsi été établie. Quelques espèces rares, voire inattendues font l’objet de commentaires faunistiques. Cet inventaire offre par ailleurs l’opportunité de situer le massif forestier étudié dans une échelle de valeur biologique des forêts pyrénéennes en 5 classes

Is there a synergy between hedges and intercrops for pest biocontrol ?

A major challenge for agroecology is to identify alternative cropping systems that can both ensure sufficient levels of food production and reduction in pesticide inputs while maintaining ecosystem integrity and simultaneously delivering multiple ecosystem services. Among ecological services, biocontrol of pests by natural enemies could be improved by effective management of semi-natural elements in landscape such as hedgerows (Landis et al., 2000). Another way to reduce pest populations in fields consists in increasing diversity of crop species both in time and space. A practice such as intercropping that creates structures of mixed plant populations with "barrier" or "dilution of resources" effects (Médiène et al., 2011) can reduce the pressure of pathogens, weeds and pests compared with that exerted on sole crops (Letourneau et al., 2011). While the combination of these two kinds of practices designed to strengthen auxiliary communities often appears efficient and could result in a synergy, many cases of study show opposite results (e.g. Straub and Snyder, 2006). Our study aimed at quantifying and comparing the efficiency of both hedgerow and intercropped pea and wheat on pest biocontrol in a field. We examined i) the potential role of different types of field edges (with and without an hedgerow) on biological control of weed seeds, aphids, pea weavils and eggs of Sitona lineatus, ii) the effect of intercropping on the biological control of these pests compared with sole crops and iii) the interaction between the two factors. We conducted both field surveys of pest abundance and pest biocontrol effectiveness by estimating predation rates by using seeds and prey sticked on cards. We found that aphid density was slightly lower in pea-wheat intercrops than in sole crops, and was influenced by the distance from the field edge (whatever the kind of edges). However, neither the hedgerow nor the intercrop situation favored aphid predation. The density of weeds did not vary according to the cropping system and distance from the field edge. We showed that the predation rate of weed seeds or of Sitona lineatus eggs and the parasitism of Bruchus pisorum decreased according to the distance to the hedge in sole crops but increased in the intercrop. This study points out the absence of a global synergy between intercrops and hedges in supporting pest and weed regulation: the regulation efficiency varied according to pest species. This study calls for a deepened multi-species approach in order to find trade-offs between agricultural practices and field edge management to optimize regulating ecosystem services such as pest biocontrol

Do species interactions prevent Limoniscus violaceus from living in suitable basal hollow trees?

The violet click beetle (Limoniscus violaceus) is an endangered beetle that is protected in Europe. Its conservation required better knowledge on its biology. Recently, a study revealed that the probability of occurrence of L. violaceus in hollows increases with increasing tree circumference at 30 cm above ground and with increasing hollow decay stage (Gouix et al., submitted). However, the model showed that it was easier to identify unoccupied hollows than to identify the occupied ones. As tree hollows harbour a ränge of associated and facultative species living within a relatively small habitat, we may suspect some species interactions (competition and/or predation) that prevent Limoniscus violaceus from occupying suitable basal hollow trees. We studied beetle and Spider assemblages emerging from 73 basal hollow trees located within a Single forest site of 3500 ha (in France). All trees were considered to be suitable for Limoniscus violaceus (i.e. trees with a circumference at 30 cm above ground greater than 235 cm and cavity at an advanced stage of decay). We used the probabilistic approach to test for statistically significant pair-wise patterns of species co-occurrence. In total, 4805 species pairs were analyzed and 9.6 % had non-random patterns. We detected very few negative co-occurrence patterns (19) compared with positive ones (444). Regarding Limoniscus violaceus, we highly linked to the presence of tree hollows in mature trees. Moreover, the interaction between saproxylic insects and hollows shows specialised interacting patterns that model the structure and stability of these saproxylic assemblages. The objective of this work is to evaluate how interacting patterns of saproxylic insect networks vary according to woodland sites. We selected three representative Mediterranean woodlands in the Park: one sclerophyllous oak woodland of Quercus rotundifolia; one mixed deciduous oak woodland of Quercus pyrenaica and Quercus faginea; and one ash riparian woodland of Fraxinus angustifolia. We considered 30, 30 and 27 tree hollows, respectively, which were covered with emergence traps. Our study lasted one year, during which traps were emptied monthly and pots were replaced. We selected Coleoptera and Syrphidae (Diptera) as study groups. They were sorted according to trophic guilds: xylophagous, saproxylophagous, saprophagous, xylomycetophagous and predators. We used Aninhado and Modular programmes to evaluate the network architecture, and bipartite for R programme to study interacting attributes in the hollow-saproxylic insect interaction in each woodland site. Saproxylic insect-hollow networks presented a significant nested pattern, which means that most of the interactions are established with the most generalist nodes/species at both trophic levels (in this case, the lower trophic level is composed of hollows and the higher trophic level is composed of insects). Not all studied forests showed the same level of connectance (proportion of possible links between trees and species), the deciduous oak woodland being the forest with the most densely interconnected network

Dispersion et persistance de la biodversité dans la trame forestière (DISTRAFOR)

L’établissement d’un trame forestière fonctionnelle, c’est -à-dire qui permette aux espèces de se déplacer et de migrer au sein des paysages, suppose de connaître les espèces qui se dispersent mal et les configurations paysagères délétères. Pour y répondre, le projet Distrafor a étudié la réponse à la connectivité spatiale et temporelle forestière de la flore vasculaire, des coléoptères saproxyliques et carabiques, et de la faune du sol, en contrôlant la qualité de l’habitat. Les analyses ont porté sur des données préexistantes et acquises pour ce projet, en étudiant à partir de cartes anciennes et de données de biodiversité contemporaines les assemblages faunistiques et floristiques dans des boisements anciens et récents. Les résultats montrent que près de la moitié des plantes réagit à l’ancienneté de l’usage forestier mais cette réponse peut s’expliquer en partie par des différences des caractéristiques chimiques des sols entre forêts anciennes et forêts récentes. Des analyses complémentaires restent à réaliser pour estimer la proportion de plantes véritablement limitées par de faibles capacités de dispersion. Ces espèces bénéficient de l’accroissement de la connectivité forestière, en particulier dans les zones de grandes cultures et les zones urbaines. La colonisation est nettement favorisée lorsque l’accroissement forestier se fait au contact direct de bois anciens. Les plantes naturalisées ne semblent pas particulièrement favorisées par la connectivité. En contexte agricole, la composition des assemblages de coléoptères carabiques et sa proxyliques varie entre boisements récents et anciens, alors qu’elle ne semble réagir ni à la qualité, ni à la connectivité de l’habitat forestier ; les cortèges sont moins riches dans les paysages les plus boisés. Certaines espèces de coléoptères semblent pouvoir compenser une plus forte fragmentation forestière par de meilleures capacités de dispersion. Sur les mêmes sites, la macrofaune du sol répond à ces paramètres mais de façon différenciée selon les taxons et la région. Ces résultats montrent qu’il faut cibler les opérations de restauration sur les zones les moins boisées, et qu’il faut encourager en parallèle le maintien et la restauration de la qualité des habitats forestiers les plus fragiles

A socio-ecological framework for the analysis of edges dynamics and their consequences on ecosystems services in temperate landscapes

The 2015 World Congress was a joint meeting between the International Association of Landscape Ecology World Congress (WC) and the U.S. chapter of IALE (US-IALE), held at the Hilton Portland & Executive Tower in Portland, Oregon, July 5 - 10, 2015. The theme was: Crossing Scales, Crossing Borders: Global Approaches to Complex Challenges. The meeting brought together nearly 1,000 leaders in landscape ecology from around the globe, including educators and practitioners in the fields of geology, ecology, biology, geography, and landscape preservation and design, dedicated to preserving and protecting our natural resources

Bat responses to changes in forest composition and prey abundance depend on landscape matrix and stand structure

Despite the key importance of the landscape matrix for bats, we still not fully understand how the effect of forest composition interacts at combined stand and landscape scales to shape bat communities. In addition, we lack detailed knowledge on the effects of local habitat structure on bat-prey relationships in forested landscapes. We tested the assumptions that (i) forest composition has interacting effects on bats between stand and landscape scales; and (ii) stand structure mediates prey abundance effects on bat activity. Our results indicated that in conifer-dominated landscapes (> 80% of coniferous forests) bat activity was higher in stands with a higher proportion of deciduous trees while bats were less active in stands with a higher proportion of deciduous trees in mixed forest landscapes (~ 50% of deciduous forests). Moth abundance was selected in the best models for six among nine bat species. The positive effect of moth abundance on Barbastella barbastellus was mediated by vegetation clutter, with dense understory cover likely reducing prey accessibility. Altogether, our findings deepen our understanding of the ecological processes affecting bats in forest landscapes and strengthen the need to consider both landscape context and trophic linkage when assessing the effects of stand-scale compositional and structural attributes on bats

Insights about saproxylic biodiversity living in old-growth forests of French Pyrénées

The symposium will span over four days, including a one day field trip. Keynote addresses will introduce morning sessions followed by parallel conference sessions. Scientific poster sessions, held in the late afternoon, will be combined with a cocktail buffet. A banquet will take place on Wednesday night. All events will be held at the Rouyn-Noranda Congress Center