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Dynafor au congrès international de la SFE²

Avec plus de 1000 sur place et d'autres en ligne, la conférence a été un moment fort pour les communautés d'écologie française et allemande. Les présentations devraient être disponibles prochainement en rediffusion vidéo sur le site de la conférence.

Il y a eu 5 communications orales faites par des dynaforien.nes dans plusieurs sessions de ce colloque, dont une session dédiée à l'écologie des paysages, et 4 communications dont des Dynaforien.nes étaient co-auteurs. En voici les résumés de présentation:

1°) The new assets of landscape ecology in the face of global challenges

Marc DECONCHAT 1 , Cécile ALBERT 2 , Audrey ALIGNIER 3 , Stéphanie AVIRON 3 , Laurent BERGES 4 , Sébastien BONTHOUX 5 , Solène CROCI 6 , Aude ERNOULT 6 , Cendrine MONY 6 , Clélia SIRAMI 1

1 Inrae - Castanet Tolosan (France), 2Cnrs - Marseille (France), 3 Inrae - Rennes (France), 4 Inrae - Grenoble (France), 5 Insa-Cvl - Blois (France), 6Univ Rennes1 - Rennes (France)

Abstract : In an ever-changing world threatened by multiple, wide-ranging and sometimes sudden crises, the ecological sciences need to assess how they can contribute to effectively addressing these emerging issues. Landscape ecology has evolved significantly in recent decades. Its concepts, methods, tools and results open new perspectives and are particularly relevant to address problems for which intermediate scales, such as landscapes, seem to be the most appropriate for action. Moreover, landscape ecology can be mobilized to address a wide range of interrelated issues such as global health, climate change, biodiversity conservation and food security. Spatio-temporal heterogeneity, at the heart of landscape ecology concepts, is now seen as a way of adapting to global changes. Remote sensing data and methods could also provide useful information for analyzing evolution trajectories and steering the socio-ecosystems. Developments in spatial modelling are contributing to society debates with increasingly refined scenarios of expected or desirable changes to guide realistic and fair transitions. However, the production of new, finer and more precise data and knowledge is not always enough to trigger the necessary changes and to anticipate future crises. Interactions between scientists and territorial stakeholders are often crucial to move from knowledge development to action. Because landscapes are socio-ecological systems, the social dimension of landscape analysis, such as developed through european landscape ecology is an important axis in which a development of tools and concepts is urgently needed. This presentation urges scientists to take up these issues, to develop transdisciplinary research questions and methods and to disseminate their results widely to accelerate the necessary transitions.

2°) Searching for optimal sampling design for landscape-scale biodiversity surveys

F. Laroche 1

1 Umr 1201 Dynafor University Of Toulouse Inrae Inpt Ei Purpan Castanet-Tolosan - Toulouse (France)

Abstract : Evaluating the spatial autocorrelation in species distribution is a necessary step for many applied ecological questions at landscape scale, like building a reserve network or implementing an efficient monitoring program. Autocorrelation range can be inferred from spatial sampling. However, there exists a trade-off between estimating of the autocorrelation range of a species distribution and estimating trends in the mean species abundance or occupancy among sites, which is also a question of interest in many studies. For instance, the random sampling design is a good heuristic to estimate autocorrelation range, as pairwise distances among samples cover a wide array of possible autocorrelation ranges. By contrast, the grid design is a better choice for estimating trends of the mean among sites as it eliminates small pairwise distances prone to pseudo-replication. Hybrid strategies mixing random and grid are thought to yield a polyvalent design able to cope with both conflicting objectives. Yet, fractal sampling designs could also show such intermediary performance, for it preserves some regularities associated to grid, but also contains various spatial scales browsing a wide array of possible autocorrelation ranges. Here, we studied for which questions fractal or hybrid design could be advantageous sampling strategies. We used optimal design theory to compare the accuracy of random, grid, hybrid and fractal designs at estimating mean and autocorrelation range of a field of values. We retrieved that the hybrid strategy is a Pareto-optimal intermediary strategy between grid and random designs. Fractal designs showed distinct properties : they performed better than both random and grid designs for estimating small autocorrelation ranges, but worse than other designs for estimating intermediate aurocorrelation ranges and mean value of a traget field. Overall, hybrid designs seemed appropriate when looking for a polyvalent design. Fractal designs could constitute a valuable alternative when specifically aiming at estimating of small autocorrelation ranges while tolerating a cost on other objectives. Thus, the interest of fractal designs appeared quite circumscribed in our study. More generally, harbouring explicit spatial scales may be a clear advantage of fractal designs for the analysis of biodiversity patterns when distinct biological processes occur at distinct spatial scales.

3°) How landscape heterogeneities could contribute to wild bees diversity and pollination in agricultural landscapes

Symposium: Diversification of agricultural landscapes to promote pollinator biodiversity and pollination service delivery

Ouin, A.1,x, Carrié, R., Desaegher, J., Rivers-Moore, J. 1,x, Sheeren, D. 1,x, Sirami, C. 1,x, Vialatte, A. 1,x, Andrieu, E. 1,x

1, UMR DYNAFOR, INRAE / Toulouse INP, Auzeville Tolosane, France

2, Center for environnemental and climate science, Lund University, Sweden

3, INRAE, UR 406 Abeilles et Environnement, Avignon, France

x, LTSER ZA PYGAR, Université de Toulouse, Auzeville Tolosane, France

Landscape heterogeneity support multiple ecosystem services, including the pollination of crops and wild flowers. In the Long Term Socio-Ecological Research (LTSER) site of Vallées et Coteaux de Gascogne (VCG), which is part of the LTSER platform ZA PYGAR located in south-west France, local features of the VCG and social systems have interacted with global drivers (like CAP) and lead to the maintenance of a high level of landscape heterogeneity. We show how the different components of landscape heterogeneity : composition (with a focus on wooded semi-natural habitats), configuration but also heterogeneity of practices contribute to wild bees diversity and potential of pollination. The modelling of pollinators and pollination allow us to propose some guidelines about the location of flower resource patches to ensure crop pollination.

4°) Crop diversity in the landscape favors bats and biological control of some pests

A. Tortosa 1 , B. Giffard 2 , L. Barbaro 1, 3, J. Froidevaux 3, 4, S. Ladet 1 , J. Delhommel 1 , A. Vialatte 1

1 Université De Toulouse, Inrae, Dynafor - Auzeville-Tolosane (France), 2Bordeaux Sciences Agro, Inrae, Isvv, Save - Villenave D'ornon (France), 3CESCO, Muséum national d'Histoire naturelle, CNRS, Sorbonne University - Paris/concarneau (France), 4University of Stirling, Biological and Environmental Sciences, Faculty of Natural Sciences - Stirling (United Kingdom)

Abstract : Agricultural landscapes mixing crop types can support higher biological pest control, while contributing to maintain farmland biodiversity. In addition to their status of protected species, bats have been recently shown to be efficient predators of many agricultural and forest pests. In our study, we investigated how diverse agricultural landscapes could promote bat richness, activity and biological pest control. We hypothesised that resource continuity may be ensured in diverse landscapes combining maize, vineyards and pine plantations, which are major crops of South-western France. Indeed, flight peaks of three associated moth pests follow one another in time and are known to be prey of several insectivorous bats. We therefore evaluated whether diverse landscapes with all 3 crops (maize, vineyard and pine, with the proportion of semi-natural habitats controlled) affect bat communities and their biological control activity, by comparing them with simplified landscapes dominated by only one of the three crops. Our study involved 37 landscapes (vineyards-, maize-, pine plantations-dominated landscapes and diverse landscapes) where abundance of the three lepidopteran pests were measured with specific pheromone baited-traps according to their first generation flight peak. Alternative preys were estimated with food traps. Bat activity was recorded two consecutive nights with passive detectors. Finally, specific damages were observed. We found that diverse landscapes have positive effects on bat species richness and activity. We also showed that grapevines and pine plantations benefit from a diverse landscape from the point of view of controlling their main pests by bats. Maize-dominated landscapes showed contrasting results, pest abundances and damage were positively related to bat richness and activity; assessing the actual efficiency of their biological control would require longer-term investigations. In addition, more diverse landscapes benefit to a large range of bat species and especially for species of conservation concern activity. This work highlights potential win-win strategies between different crops managed by different producers at the landscape scale. Overall, our study advocates for promoting the diversity of coexisting crop types within agricultural landscapes to enhance bat species richness, which in turn would sustain higher pest biological control and ultimately bolster biodiversity conservation strategies in farmland.

5°) How repeatable are communities in Fomes polypores?

A. Ardanuy 1 , O. Rose 2 , C. Bouget 3 , A. Brin 4 , F. Laroche 1

1 INRAE UMR DYNAFOR - Castanet Tolosan (France), 2Office National des Forêts - Fontainebleau (France), 3 INRAE UMR EFNO - Nogent-Sur-Vernisson (France), 4E.I. PURPAN UMR DYNAFOR - Toulouse (France)

Abstract : Coexistence of species within communities is thought to result from the joint effect of stochasticity, equalizing mechanisms and stabilizing mechanisms. Stabilizing mechanisms, such as niche differences, may generate predictable functional structures of communities. Here we tested this assumption on feeding guilds of coleopteran communities within Fomes polypores. We examined whether those communities presented a repeatable functional community at distinct sampling scales in five sites using constrained null models. The scales considered were polypore, plot and site. For each scale, we tested whether the functional structure in terms of feeding guilds was more repeatable among units than expected by chance, and assessed whether such repeatability was stronger than the one observed at species level. In parallel we examined the species structure within guilds, and tested whether species turnover differed among guilds with different trophic position (fungivorous and predatory). Our preliminary analysis shows that coleopteran communities within polypores varied significantly among plots at species level, with larger β-diversity than those of null communities, while feeding guilds did not. This suggests that these coleopteran communities present functional redundancy. At the next organisation level, plot scale, the coleopteran community β-diversity matched that of null communities from both species and feeding guild perspective. At the global scale both coleopteran communities and feeding guilds showed structure at site scale, with larger β-diversity than randomised null communities. When exploring species co-existence within feeding guilds, our analysis showed greater β-diversity for fungivorous species than for the null model communities at plot scale, while predatory species showed the opposite trend. This indicates that these feeding guilds diverge in their response to plot structure. At global scale our analysis showed similar diversity patterns for fungivorous than at plot scale, and no divergence from the null communities for predators. Our results support the idea of a repeatable structure of coleopteran communities at polypore scale with exchangeable species composition given a local species pool. We speculate that differences in feeding guilds β-diversity patterns are due to the predatory guild comprising more habitat generalist species - which may be favoured in fragmented systems - than the potentially more habitat obligate fungivorous guild.

Dynafor a aussi participé à d’autres présentations :

6°) Avian insectivory is not mediated by bird acoustic and functional diversity along a wide latitudinal gradient

L. Schillé 1 , E. Valdés-Correcher 1 , F. Archaux 2 , F. Bălăcenoiu 3 , M. Bjoern 4 , M. Bogdziewicz 5 , T. Boivin 6 , C. Bouget 2 , M. Branco 7 , T. Damestoy 8 , M. De Groot 9 , J. Dobrosavljević 10, L. Barbaro 11, B. Castagneyrol 1

1Biogeco, Inrae, University Bordeaux, Cestas, France - Cestas (France), 2Efno, Inrae, Nogent-Sur-Vernisson, France - Nogent-sur-Vernisson (France), 3National Institute For Research And Development In Forestry “marin Drăcea” Bucharest. Bulevardul Eroilor 128, 077190 Voluntari, Romania - Voluntari (Romania), 4Department Of Geosciences And Natural Resource Management, Section Forest, Nature And Biomas, University Of Copenhagen - Copenhagen (Denmark), 5Faculty Of Biology, Adam Mickiewicz University In Poznan, Poland - Poznan (Poland), 6 Inrae Ur629 Ecologie Des Forêts Méditerranéennes, Avignon, France - Avignon (France), 7Centro De Estudos Florestais, Instituto Superior De Agronomia, Universidade De Lisboa Forest Technical University - Lisboa (Portugal), 8Unilasalle, Aghyle, Up.2018.c101 - Beauvais (France), 9Slovenian Forestry Institute, Večna Pot 2, 1000 Ljubljana, Slovenia - Ljubljana (Slovenia), 10Univeristy Of Belgrade Faculty Of Forestry - Belgrad (Serbia), 11Dynafor, University Of Toulouse, Inrae - AuzevilleTolosane (France)

Abstract Biodiversity increases towards the tropics. It has long been assumed that this pattern resulted from an increase in the intensity of biotic interactions towards lower latitudes. Yet, this view is being challenged. Pluralistic research is needed to elucidate the mechanisms underlying latitudinal variation in biodiversity and biotic interactions, which implies a sound examination of an ecological force overlooked so far: predation. In this study, we asked whether more diverse communities of insectivorous birds impose a stronger predation pressure on prey and whether this diversity-function relationship varies with latitude. We deployed artificial caterpillars in 138 oak trees along a 19° latitudinal gradient in Europe to quantify bird predation rates. We used passive acoustic monitoring devices to characterise the acoustic diversity around oaks as well as the species and functional diversity of insectivorous birds. Avian predation rates increased with latitude and percentage of forest cover. The functional diversity of insectivorous birds increased with increasing temperature, but had no effect on avian predation rates. The acoustic diversity was influenced by percentage of forest cover, but was independent of insectivorous bird diversity. Acoustic diversity had no influence on avian predation rates. Contrary to our predictions, latitudinal clines in predation rates were not associated with changes in bird diversity or acoustic diversity.

7°) Positive response of flower-visiting insect abundances to landscape context relies on nectar productivity

A. Alignier 1, 2, N. Lenestour 1 , E. Jeavons 1 , J. Van Baaren 3 , S. Aviron 1 , L. Uroy 1, 4, C. Ricono 3 , C. Le Lann 3

1 Inrae Umr 0980 Bagap - Rennes (France), 2LTSER Zone Atelier Armorique - Rennes (France), 3Université De Rennes 1, Umr-Cnrs 6553 Ecobio - Rennes (France), 4Université de Toulouse, École d’Ingénieurs de Purpan, INPT, Umr 1201 Dynafor - Toulouse (France)

Abstract : In agricultural landscapes, flower‐visiting insects such as domestic bees, wild bees and hoverflies ensure pollination of many crops and wild plants. Landscape studies aiming to explain flower‐visiting insect abundance mainly focus on land cover maps. This structural landscape view has been challenged by many authors who pointed out the need for a functional approach that considers the fundamental ecological requirements of species (“species-centered”) to better understand biodiversity patterns and functions. Here, we proposed a functional landscape view based upon the attractiveness, accessibility and profitability of floral resources, from both crop and non-crop habitats and across several spatial scales to explain abundance of flower-vising insects. We translated land-cover maps of 40 landscapes of 250 m, 500 m and 1000 m radius into floral resource maps, using pre-existing vegetation surveys and floral traits databases. In the centres of the landscapes, abundances of flower-visiting insect groups (i.e. domestic and wild bees, bumblebees and hoverflies) were recorded in organic winter cereal fields. We showed that floral resource maps significantly explained the abundances of flower-visiting insect groups. Insect abundances were consistently higher in landscapes with high floral resource profitability. Domestic and wild bees < 1 cm responded positively to nectar productivity at the largest spatial scale, i.e. 1000 m landscape radius. Using functional maps based upon floral resources, we succeed in explaining flower-visiting insects’ abundances, identifying which category of floral resources organisms require, and in which habitat types theses resources prevail. Our results open new research area aiming to manage the environment by optimizing floral resources for species conservation or maintaining ecosystem services.

8°) Evaluation and comparison of pollination service indicators at agricultural landscape level

T. Gandara 1 , A. Michelot-Antalik 2 , A. Gardarin 3 , S. Petit-Michaut 4 , J. Desaegher 5 , E. Pocher 1

1 Centre D'ecologie Et Des Sciences De La Conservation (cesco), Muséum National D'histoire Naturelle, Centre National De La Recherche Scientifique, Sorbonne Université - Paris (France), 2Université De Lorraine, Inrae, Lae - Nancy (France), 3Agroparistech, Umr 211 Agronomie, Thiverval-Grignon - Grignon (France), 4 Inrae, Umr1347 Agroécologie - Dijon (France), 5Université De Toulouse, Inrae, Umr Dynafor, - Castanet-Tolosan (France)

Abstract The current pollinator decline is a major issue, notably because one-third of the world agricultural production depends on pollination. However, quantifying whether the loss of some pollinators translates into less efficient pollination remains challenging, particularly at the scale of farmland territories, which is a relevant scale for action. On the one hand, clear links have been established between the abundance and diversity of pollinators and pollination efficiency only over relatively small areas, because time-consuming experimental methods prohibit studies over broader areas. On the other hand, nationwide or continentwide indices exist but they either measure potential pollination only or have not been validated against other metrics characterizing pollinators or pollination. The aim of our study was to assess the relevance of two pollination indicators developed at national or broader scale, to characterize pollination over a 950-ha farmland territory of field crops (Fénay platform near Dijon, France). We specifically evaluated the realized pollination service indicator, based on crop yields and their dependence on pollinators, and the potential pollination indicator simulated by the InVEST model, based on land use and landcover as proxies for potential floral and nesting resources. We examined the spatiotemporal variation of these indicators over the Fénay area between 2005 and 2019, their environmental correlates (farming practices, landscape, and weather) and how they were related to each other. Our results suggest that the two indicators designed for large spatial extent can prove useful within farmland territories: both indicators exhibit significant variation across the study area, some of which could be related with environmental variables known to influence pollinators. For example, the spatial variation in the realized pollination service index correlates with farming practices, e.g. less efficient pollination in plots with more herbicide use. No correlation with the distance to the nearest semi-natural element was found, which contradicts results from previous studies at the field scale. The temporal variation in the pollination service index correlates negatively with the duration and intensity of summer heat waves. The potential pollination indicator will be compared with the realized pollination indicator, and in the future with field measurements of pollination efficiency for cross validation.

9°) Ambient and substrate energy influence decomposer community diversity differentially across trophic levels: An experimental approach using saproxylic beetles

P. Kriegel 1, S. Thorn 2 , Brin, A., Larrieu, L, al.

1 University Wuerzburg (Germany), 2Hessian Agency For Nature Conservation (Germany)

Abstract: The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy, (i.e., solar radiation, temperature) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are largely lacking. To show differential effects of energy types between trophic levels on decomposer communities, we compiled data on 332 557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species along a latitudinal gradient in Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles were determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Besides the influence from energy-related measures, diversity was positively affected by co-variables like deadwood amount, while effects of deadwood decay stage varied between trophic levels. We therefore show that influence of substrate energy on decomposer communities is dependent on trophic levels, which need to be considered when trying to predict biodiversity.


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