The project of Zone Atelier Pyrenees-Garonne (ZA PYGAR)

South-Western France, going from the Pyrenees mountains to the plains of the Garonne river basin. PYGAR tries to answer three main scientific questions: 1/ What are the respective contributions of climate change and local anthropogenic disturbances to ecosystem changes (biodiversity, bio-physical characteristics)? 2/ How human practices drive ecosystem services? 3/ What are the relationships between resources availability and their accessibility, and the historic and prehistoric human population structure? The main transversal question of PYGAR is the adaption and response time of the different SES to global changes. The SES are studied at different time scales from the last glacial maximum to the present-day. PYGAR clusters 17 Labs (40 full-time permanent staffs: 23 researchers/professors & 17 engineers/technicians) from Toulouse and Bordeaux, supported by the University of Toulouse and several French research organisms (CNRS, INRA, IRSTEA, IRD, CNES, BRGM, Météo France). Socioeconomic partners (companies, farmer’s associations…) and public services (Occitania Region, Water Agency…) are strongly interested in the project. PYGAR includes 4 territories (sites ateliers): the central Pyrenees mountain range, the Garonne River, the agricultural hills and valleys of the Gascogne region and the Viaur-Aveyron river basin. The theory of SES provides a valuable tool to set up an interdisciplinary approach to deal with the co-evolution and resilience of the social and ecological templates of the studied systems facing global changes (climate change and land cover)

Spatial uncertainty effects on a species-landscape relationship model in ecology

In this study, we explore the effects of geometrical uncertainty in an existing species-landscape relationship model in the hoverfly communities. We also investigate how geometrical uncertainties affect a more complex model including both current forest patch features and past forest features. Because of a possible time-lag in biological responses to forest changes such as fragmentation, the historical dimension is added to the first model. The proposed approach relies on three spatial sources enabling to get forest fragments at different times: historical map (~1850), aerial black and white photographs (1954) and orthorectified photographs (2010). Firstly, we analyze the effect of the spatial data production method (manual versus automatic) on models using current forest patches only. Then, we build a more complex model including past changes in forest size. As previously, the effect of production-based uncertainty was assessed by comparing the models based on forests extracted manually and automatically. We address finally the impact of positional accuracy on the historical map by using a Monte Carlo simulation approach. Global results show that responses of the statistical models are strongly affected by spatial uncertainty in inputs

Spectro-temporal heterogeneity measures from dense high spatial resolution satellite image time series: application to grassland species diversity estimation

Grasslands represent a significant source of biodiversity that is important to monitor over large extents. The Spectral Variation Hypothesis (SVH) assumes that the Spectral Heterogeneity(SH) measured from remote sensing data can be used as a proxy for species diversity. Here, we argue the hypothesis that the grassland’s species differ in their phenology and, hence, that the temporal variations can be used in addition to the spectral variations. The purpose of this study is to attempt verifying the SVH in grasslands using the temporal information provided by dense Satellite Image Time Series (SITS) with a high spatial resolution. Our method to assess the spectro-temporal heterogeneity is based on a clustering of grasslands using a robust technique for high dimensional data. We propose new SH measures derived from this clustering and computed at the grassland level. We compare them to the Mean Distance to Centroid (MDC). The method is experimented on 192 grasslands from southwest France using an intra-annual multispectral SPOT5 SITS comprising 18 images and using single images from this SITS. The combination of two of the proposed SH measures—the within-class variability and the entropy—in a multivariate linear model explained the variance of the grasslands’ Shannon index more than the MDC. However, there were no significant differences between the predicted values issued from the best models using multitemporal and monotemporal imagery. We conclude that multitemporal data at a spatial resolution of 10 m do not contribute to estimating the species diversity. The temporal variations may be more related to the effect of management practices

Discriminating small wooded elements in rural landscape from aerial photography: a hybrid pixel/object-based analysis approach

While small, fragmented wooded elements do not represent a large surface area in agricultural landscape, their role in the sustainability of ecological processes is recognized widely. Unfortunately, landscape ecology studies suffer from the lack of methods for automatic detection of these elements. We propose a hybrid approach using both aerial photographs and ancillary data of coarser resolution to automatically discriminate small wooded elements. First, a spectral and textural analysis is performed to identify all the planted-tree areas in the digital photograph. Secondly, an object-orientated spatial analysis using the two data sources and including a multi-resolution segmentation is applied to distinguish between large and small woods, copses, hedgerows and scattered trees. The results show the usefulness of the hybrid approach and the prospects for future ecological applications

Biodiversité et services rendus à l’agriculture. Principaux enseignements de différents dispositifs de recherche récents et actuels en Midi-Pyrénées

Dans le canton d’Aurignac, des chercheurs de l’Institut national de la recherche agronomique et de l’Institut national polytechnique de Toulouse travaillent depuis une trentaine d’années sur l’agriculture, les paysages et la biodiversité. Les paysages agricoles étudiés sont caractérisés par une agriculture de polyculture élevage et la présence de petits bois. Ces paysages agri-forestiers constituent un site d’étude à long terme qui est reconnu au niveau national et européen

From farm, landscape and territory analysis to scenario exercise: an educational programme on participatory integrated analysis

Tools and methodologies have been developed to enable integrated analysis (IA) of complex issues like agro‐ecosystems and natural resources management. They are based on interdisciplinary and often on participatory approaches combining, interpreting and communicating knowledge from diverse scientific disciplines and from stakeholders. In this paper we present the original educational programme built to enable students in agronomy to implement participatory IA methods in order to deal with sustainability issues in rural territory. In this educational programme students take a professional project management situation on a given case study. One of the originality of the course programme lies in its twofold objectives: building student capacities for carrying out integrated multi‐scale analysis of complex systems and providing researchers with an operational research device which facilitates the integrated analysis of new study territories. The educational programme articulates trips in the case study region and formation modules on project management, farming systems sustainability assessment, landscape multifunctionality analysis, stakeholder analysis and interviews, territorial diagnosis and narrative scenario construction. The main objectives and methods used in these modules are presented and discussed in the light of the outcomes of the implementation of this educational programme. Discussion is focused on the main educational and research issues of this programme

Éléments semi-naturels des paysages agricoles et boisés et connectivités pour les pollinisateurs sauvages

Les espaces agricoles couvrent plus de la moitié du territoire français. Ils ont donc un rôle essentiel dans la préservation de la biodiversité et des continuités écologiques. Ce rôle dépend fortement des pratiques agricoles. Parmi celles-ci, l’agro-écologie est une façon de concevoir des systèmes de production qui visent à diminuer les pressions sur l’environnement et sur les ressources naturelles et à préserver, voire amplifier, la fonctionnalité écologique des exploitations. Favoriser les infrastructures agro-écologiques est susceptible de contribuer à la circulation de nombreuses espèces et à favoriser la connexion écologique des espaces naturels ou semi-naturels.Cette biodiversité est par ailleurs utile à l’agriculture en raison des nombreux services qu’elle apporte (pollinisation, auxiliaires des cultures…).A une échelle plus vaste, la transition agro-écologique des territoires, peut conduire à la mise en place de projets favorables à la biodiversité tout en structurant des filières répondant aux besoins des consommateurs locaux.L’Agence française pour la biodiversité organise une journée d’échanges techniques dans le cadre du Centre de ressources Trame verte et bleue et en partenariat avec le ministère de la Transition écologique et solidaire et le ministère de l’Agriculture et de l’Alimentation.Cet événement cherchera à répondre aux questions suivantes : Quelles synergies peut-on développer entre agro-écologie et Trame verte et bleue ? Quels services réciproques peuvent se rendre les pratiques agro-écologiques et une biodiversité fonctionnelle ? Comment accompagner les acteurs de terrain dans cette approche ? L’objectif de cette journée est de favoriser le développement de l’agro-écologie dans les projets de Trame verte et bleue en réunissant les acteurs de la biodiversité et du monde agricole. Elle visera à présenter des retours d’expériences réussies illustrant les bénéfices mutuels entre production agricole et biodiversité

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

Edge contrast does not modulate edge effect on plants and pollinators

Edge contrast, is one of the main determinants of edge effects. This study examines the response of plant and pollinator diversity (bees and butterflies) to forest edge contrast, i.e. the difference between forests and adjacent open habitats with different disturbance regimes. We also investigated a potential cascading effect from plants to pollinators and whether edge structure and landscape composition mediate the relationship between edge contrast and beta diversity of pollinators. We sampled 51 lowcontrast edges where forests were adjacent to habitats showing low levels of disturbance (i.e. grey dunes, mowed fire-breaks, orchards, grasslands) and 29 high-contrast edges where forests were adjacent to more intensively disturbed habitats (i.e. tilled firebreaks, oilseed rape) in three regions of France. We showed that plant diversities were higher in edges than in adjacent open habitat, whatever the edge contrast. However, plant beta diversity did not differ significantly between low and highcontrast edges. While we observed higher pollinator diversities in adjacent habitats than in low-contrast edges, there were no significant differences in pollinator beta diversity depending on edge contrast. We did not observe a cascading effect from plants to pollinators. Plant and bee beta diversities were mainly explained by local factors (edge structure and flower cover) while butterfly beta diversity was explained by surrounding landscape characteristics (proportion of land cover in grassland)

Odonata communities in an agricultural lowland in the South of France

Odonata communities were studied in an agricultural landscape where semi-natural habitat patches (pastures and woods, with a dense network of deep ditches) are embedded in a crop mosaic (cereals, irrigated maize). We compared species richness and diversity of aquatic plants and odonata in ditches surrounded by pastures or by crops. Ours results showed that this surrounding (pastures vs crops) has no effect on aquatic plant and odonata species richness and diversity. However, in cultivated areas water supply through irrigation and deep ditches with plant-covered borders could promote odonata species. High level of vegetation cover (particularly with Typha sp.) limited odonata richness and diversity. A rare species in Europe, protected and sensible to pollution, Coenagrion mercuriale, occurred in many ditches including those surrounded by crops, particularly those with an intermediate semi-aquatic vegetation cover. The regular maintenance of ditches, by limiting shrubs and trees height, keep them open and facilitate the dispersal of this little mobile species. Although irrigated crops seem to support a high level of odonata diversity, a new intensification of agricultural practices in this area by increasing the pollutant input and/or by converting pastures to crops could be detrimental to odonata communities and particularly to some species like Coenagrion mercurialeLes peuplements d'odonates ont été étudiés dans une plaine où se pratique une agriculture intensive (maïs irrigué notamment) mais où subsistent encore quelques éléments semi-naturels (prairies, bois et fossés). Nous avons comparé des fossés bordés de cultures avec ceux bordés de prairies en termes de diversité et de richesse spécifiques en plantes semi-aquatiques et en odonates. Il apparaît que l'environnement immédiat des fossés (prairies versus cultures) n'a pas d'influence sur la diversité et la richesse spécifique en plantes semi-aquatiques et en odonates. Toutefois en zone de cultures, l'apport d'eau par l'irrigation et des fossés profonds bordés de végétation, pourrait favoriser ces espèces d'odonates. Les odonates préfèrent nettement les fossés plutôt peu recouverts par de la végétation aquatique (notamment par Typha sp.). Une espèce considérée comme rare, protégée et sensible à la pollution, Coenagrion mercuriale, est présente y compris en zone de cultures. Elle affectionne surtout les fossés moyennement recouverts par la végétation semi-aquatique. L'entretien régulier par élagage des fossés, se traduisant par une faible hauteur des ligneux, limite la constitution de barrières à la dispersion de cette espèce peu mobile. Bien que les cultures irriguées semblent promouvoir la diversité en odonates, une nouvelle intensification des pratiques agricoles, notamment en accentuant les problèmes de pollution et /ou en supprimant des zones prairiales, pourrait affecter les conditions de vie des libellules comme Coenagrion mercuriale