Influence du paysage et des pratiques agricoles sur le contrôle biologique des graines d'adventices par les carabiques

Farmland biodiversity and its associated ecosystem services are affected by agricultural activities at multiple spatial scales. Among these services, the regulation of weeds by invertebrate seed predators has received much attention recently but little is known about the relative effect of local management and landscape context of fields on this process. We monitored seed predation on four common weed species and carabid communities in 28 winter-cereals fields during five consecutive weeks in spring 2010. These fields were situated in contrasted landscape contexts and varied in terms of intensity of pesticide treatments and soil tillage regimes. Weed seed predation was strongly and positively related to the Shannon diversity of (strictly) granivorous carabids and to the activity–density of omnivorous carabids but negatively to the richness of omnivorous carabids. Weed seed predation and granivore diversity were positively related to landscape diversity and the proportion cover of temporary grassland within a 1000 m radius around focal fields and were negatively affected by the intensity of local pesticide treatments. No-till systems sheltered higher diversity of granivorous carabids but did not show higher seed predation rates. We showed that landscape composition factors had a higher relative influence than local practices factors on weed seed predation service. Consequently, weed management strategies should not only consider the management of single fields but also the surrounding landscape to preserve carabid biodiversity and enhance weed seed predation service

Le projet SEBIOPAG-PHYTO : déterminants agricoles parcellaires et paysagers des variations de niveaux de régulation biologique

Ce séminaire est une restitution des principales avancées obtenues dans le cadre des projets ANR PEERLESS «viabilité d’une gestion écologique renforcée de la santé des plantes dans les paysages agricoles » (2013-2017) et FRB SEBIOPAG-PHYTO «déterminants agricoles parcellaires et paysagers des variations de niveaux de régulation biologique » (2014-2017). Le séminaire a rassemblé 60 scientifiques, pour moitié extérieure aux unités INRA partenaires de ces projets. Il s'est déroulé à Paris Paris les 27-28 novembre 2017

Les effets conjugués de la gestion parcellaire et du contexte paysager et de sa dynamique sur les bioagresseurs et les niveaux de régulation biologique

Ce séminaire est une restitution des principales avancées obtenues dans le cadre des projets ANR PEERLESS «viabilité d’une gestion écologique renforcée de la santé des plantes dans les paysages agricoles » (2013-2017) et FRB SEBIOPAG-PHYTO «déterminants agricoles parcellaires et paysagers des variations de niveaux de régulation biologique » (2014-2017). Le séminaire a rassemblé 60 scientifiques, pour moitié extérieure aux unités INRA partenaires de ces projets. Il s'est déroulé à Paris Paris les 27-28 novembre 2017

Gestion des populations de vulpins résistants : quelles possibilités offrent les pratiques culturales ?

National audienc

Bandes enherbées, biodiversité mais sans danger

National audienc

Identifying the relevant spatial and temporal scales in plant species occurrence models : the case of arable weeds in landscape mosaic of crops

SPE EcolDurInternational audienceSpecies distribution models (SDMs) represent potential valuable tools to explore factors underlying species occurrence over a large range of spatial scales. However, a recurrent problem with this approach is identifying the appropriate spatial and temporal scales for modeling. This problem is reinforced in plant populations for which it is often difficult to evaluate the limits of habitat patches. In this study, we aimed at developing SDMs for 13 arable weeds in highly dynamic small agricultural region. Although weed dynamic is widely thought to result from local processes, we explored the spatial and temporal scales that would best explain species occurrence over the area. Models were developed using weed occurrence data in 58 fields over four consecutive years (2008–2011) and spatial organization of management practices over the landscape for eight consecutive years (2004–2011). We used a model selection approach based on the minimum AIC criteria to select the best SDMs. Results showed that SDMs can successfully be applied to model weed occurrence over a small region. The appropriate temporal scale to consider in weed SDMs should encompass several years to reflect the effect of management history while the relevant spatial scale should extend beyond the crop field itself and include the field border and neighboring fields. This study illustrates that adopting a multiple scale approach is successful to model plant occurrence over a highly dynamic landscape

The relative effects of local management and landscape context on weed seed predation and carabid functional groups

International audienceFarmland biodiversity and its associated ecosystem services are affected by agricultural activities at multiple spatial scales. Among these services, the regulation of weeds by invertebrate seed predators has received much attention recently but little is known about the relative effect of local management and landscape context of fields on this process. We monitored seed predation on four common weed species and carabid communities in 28 winter-cereals fields during five consecutive weeks in spring 2010. These fields were situated in contrasted landscape contexts and varied in terms of intensity of pesticide treatments and soil tillage regimes. Weed seed predation was strongly and positively related to the Shannon diversity of (strictly) granivorous carabids and to the activity-density of omnivorous carabids but negatively to the richness of omnivorous carabids. Weed seed predation and granivore diversity were positively related to landscape diversity and the proportion cover of temporary grassland within a 1000m radius around focal fields and were negatively affected by the intensity of local pesticide treatments. No-till systems sheltered higher diversity of granivorous carabids but did not show higher seed predation rates. We showed that landscape composition factors had a higher relative influence than local practices factors on weed seed predation service. Consequently, weed management strategies should not only consider the management of single fields but also the surrounding landscape to preserve carabid biodiversity and enhance weed seed predation service

La prise en compte de la stratégie agricole améliore la compréhension de l’effet des pratiques sur les communautés adventices

National audienceLes agriculteurs présents dans une même situation de production peuvent différer dans leurs objectifs et donc leurs pratiques. Afin de tester l’effet d’une pratique particulière (ex. désherbage chimique) sur la communauté adventice, il est donc nécessaire de tenir compte de l’ensemble des autres pratiques, formant une stratégie agricole. Nous avons ainsi développé 14 indicateurs décrivant les pratiques agricoles enquêtées sur la zone de Fénay de 2004 à 2016 auprès des 23 agriculteurs de la zone. L’originalité des indicateurs est qu’ils situent chaque parcelle par rapport aux autres parcelles ayant mis en oeuvre la même culture la même année sur la zone. Ceci nous a permis d’identifier 8 stratégies agricoles sur la zone de 950 ha, qui ont été confrontées et validées avec 11 des 23 agriculteurs concernés lors d’entretiens dédiés. Nous avons ensuite cherché à savoir si la connaissance de la stratégie améliorait la prédiction de l’effet d’une pratique agricole (ex. IFT herbicide) sur la flore adventice. Les résultats montrent que les modèles statistiques étaient presque toujours plus explicatifs lorsqu’ils intégraient l’effet de la stratégie que l’effet de la pratique seule. Ceci confirme l’intérêt d’indicateur tenant compte d’effet annuel et culture, de l’intérêt d’identifier des stratégies agricoles et de les confronter aux regards des agriculteurs pour en comprendre les déterminants, afin d’améliorer notre compréhension de l’effet des pratiques sur la flore. Taking into account of the farming strategy improves the understanding of the effect of farming practices on weed communities. Farmers located in a homogeneous cropping situation can differ in their objectives and farming practices. In a way to test the effect of a particular practice (ex. chemical weeding) on the weed community structure, it is necessary to take into account all the other practices apply on the field, we’ll call hereafter farming strategy. We developed 14 indicators describing farming practices surveyed on the Fénay area from 2004 to 2016. The originality of these indicators rely on the fact that they assess the intensity of each practices implemented in a field accounting for year and crop effect. We identified 8 farming strategies on the 950-ha area, which were confronted and validated by 11 of the 23 farmers during individual interviews. Then, these strategies were integrated into models linking a unique farming practice (e.g. herbicide use) to the weed community indicators. Our results indicate that models were almost always more explicative when they included the strategy and the farming practice than the farming practice alone. It confirms that descriptors of farming practices need to account for crop and year effect, the need to identify farming strategies and confront them to the farmers, to improve the analysis of the effect of practices on weeds

A framework to type crop management strategies within a production situation to improve the comprehension of weed communities

National audienceFarmers facing the same production situation may have different farming objectives and thus farming practices. However, the latter are rarely precisely described since studies often use a unique indicator of soil use intensity, showing a weak explanatory value of biotic pressures. Our aim was to develop a framework to identify crop management strategies based on (i) 14 indicators of farming practices collected in 203 fields from 2004 to 2016 through interviews with the 23 farmers managing the fields, and (ii) a discussion with the farmers to assess to what extent they are valid. Then, we assessed how much these strategies helped improving our understanding of 412 weed communities surveyed in their fields. Indicators of farming intensity (e.g. treatment frequency index) was converted into ratios by dividing with the mean value of all the fields cultivated with the same crop in the same year. We identified eight crop management strategies with cluster analysis within a 950-ha area exposed to the same production situation. They differed, in decreasing order of importance, by the diversity of crops, tillage intensity, pesticide and fertiliser uses. The interviews of the farmers validated their assignment to each strategy. The interviews revealed the reasons why farmers implement a single or various strategies in their fields (seven farmers practiced two or three strategies because of differences in soil types or history of fields). The outputs of the classification gave them additional information on how their farming system differed from those of their neighbours. Using crop management strategies improved the quality of the statistical models predicting weed richness, cumulated weed richness over the 2008–2013 period, weed abundance and the frequency of weeding failure. This framework is useful to identify crop management strategies and to share information with farmers in order to be used to redesign cropping systems toward a more environmentally friendly agriculture