Augmentation de la biodiversité cultivée et interactions avec la production agricole, la régulation biologique des bioagresseurs et la biodiversité associée

Intensive agriculture is more and more criticized due to its negative impacts on the environment, like biodiversity loss. That’s why agroecological practices based on the increase of the planned diversity are developed. Here, we hypothesised that this increase of the planned diversity could increase the supply of ecosystem services and partly reduce effects of inputs use. The aim of the study is to observed relationships between production of good and ecosystem services of weed regulation and maintaining of associated diversity. Then we identified and described the rotations that have the best synergies between services, on 33 successions from 4 experiments. First, we created indicator to describe the successions then I performed correlations analysis on the variables and performances profiles and Pareto fronts. Finally, the most interesting successions were described with the indicators. So, we observed a negative correlation between production and weeds species richness, which is characterized by an opposition between planned diversity and the use of inputs. However, we highlighted successions which increased weed species richness without decreasing production or weeds regulation. These successions are characterised by a small decrease of inputs use and a small increase of planned diversity. It seems that we must consider in the same time planned biodiversity and input use to create new cropping systems.L’agriculture intensive est de plus en plus remise en cause pour son impact négatif sur l’environnement, avec notamment une érosion de la biodiversité. C’est pourquoi des pratiques agroécologiques se basant notamment sur l’augmentation de la diversité cultivée sont développées. On fait l’hypothèse que l’augmentation de la diversité cultivée pourrait permettre d’augmenter les services écosystémiques et substituer en partie l’effet des intrants. L’objectif est d’observer les relations entre production de biens et de services de régulation des adventices et de maintien de la diversité associée, puis d’identifier et de caractériser les successions ayant les meilleures synergies entre services, sur 33 successions provenant de 4 essais. Après la création d’indicateurs décrivant les successions, des analyses de corrélations entre variables ainsi que des profils de performances et des fronts de Pareto ont été réalisées, puis les successions les plus intéressantes ont été caractérisées par les indicateurs. Ainsi, on a pu observer une corrélation négative entre la production et la richesse en adventices, caractérisée par une opposition entre la diversité cultivée et l’utilisation d’intrants. Cependant, on a mis en évidence des successions permettant d’augmenter la richesse en adventices sans réduire la production ni la régulation des adventices. Celles-ci sont caractérisées par une faible réduction de l’utilisation d’intrants et une légère augmentation de la diversité cultivée. Il faut donc raisonner de manière cohérente la diversité cultivée et l’utilisation d’intrants

A landscape-scale approach for linking farming strategies to weed communities and their contribution to ecosystem services

National audienceWeeds present in agricultural fields provide habitats and trophic resources and as such contribute to the provision of ecosystem services such as pollination (quantity and quality of pollen and nectar in flowers) and biological control (seeds for pest natural enemies). The nature and amount of services provided depends on the floral composition of weed communities and this composition is driven by the combination of farming practices. Linking farming strategies to services is thus an important step to provide management guidelines for enhancing ecosystem services. We report here on such an analysis, based on agronomical and weed data collected annually in 70 field cores and field edges between 2008 and 2013 on the Fenay landscape platform, a 1000 ha area of arable farming located near Dijon (Eastern France). Our results indicate that across this study area, farmers adopt contrasted farming strategies and that the observed differences in field management practices lead to differences in the composition of weed communities. Our data also show that weed richness and weed community composition strongly differ between habitats, i.e. field edges and the core of the fields. Thus a phenological survey of the most frequent weeds was set up to estimate their success in providing flower and seed resources during the crop growing season and the quantity of flowers and seeds produced. We expect this success to differ between field cores and field edges and between contrasted field management strategies. Indices of services provision for observed weed communities will derive from the recorded abundance of species and their success and level of trophic resources provision under different habitats and management strategies

Analyse multi-échelles de compromis entre services écosystémiques fournis par la flore adventice

National audienceLes adventices, étant à la base des réseaux trophiques, jouent un rôle important dans les processus biologiques mis en avant en agroécologie. Cependant, elles sont également en compétition avec les cultures, il est donc important de s’intéresser aux compromis entre les services et diservices qu’elles fournissent. Pour cela, nous allons nous intéresser au suivi d’une plateforme paysagère, regroupant près de 150 parcelles contiguës de grandes cultures. Un suivi des pratiques agricoles ainsi que des relevés de flore à l’interface et à l’intérieur de la parcelle y sont réalisés depuis 2008. Les services/diservices fournis par les commuanutés observées peuvent ensuite être déterminés par des indicateurs. Ceux-ci peuvent traduire un niveau de compétition avec la culture, une valeur pollinique, une valeur de provisions de ressources pour des auxiliaires de culture ou un niveau de biodiversité. Le but de la thèse sera donc d’étudier les synergies ou antagonismes entre ces services aux échelles spatiales et temporelles. On peut ainsi étudier les compromis entre parcelles au sein du paysage ou entre l’interface et le plein-champ. On pourra également s’intéresser à la répartition des services, dans le paysage et les parcelles, au cours du temps. L’objectif final sera ainsi d’analyser le rôle que jouent les interfaces dans la fourniture et la stabilité des services écosystémiques et de mettre en évidence des stratégies de gestion optimisant les compromis

Enhancing weed multifunctionality at a landscape scale: A simulation study

International audienceThere is a pressing need for research guiding the design and management of multifunctional landscapes that combine the delivery of production services and that of other ecosystem services. Arable weeds are an interesting model as they can impact negatively crop production but also contribute to maintain pollination and pest control services. Here, we assessed weed multifunctionality using weed data recorded within a small landscape, in the field edge and field core of 97 fields over six consecutive years. We detected a general positive correlation between harmfulness and services provision, at the field-scale and at the landscape scale. At the field scale, the flora of field edges strongly contributed to the delivery of (dis)services; some fields delivered interesting trade-offs, and this was only weakly explained by the crop management strategy. At the landscape scale, we explored through scenarii the impact of changes in the composition (proportional cover of the different crop management strategies) and structure (field size, i.e. length of field edges) of the land-use mosaics on weed multifunctionality. Land–use mosaics offering interesting trade-offs were for the most part characterised by an even representation of the different crop management strategies. Small-grained landscapes did not offer better trade–offs than the current landscape structure, but slightly improved the inter-annual stability of services. Our results support the idea that promoting the co-existence of various cropping strategies within landscape is a good option to reconcile the positive and negative impacts of weeds

Multi-scale analysis of the trade-off between ecosystem services provided by weeds community

National audienc

The structure and composition of land-use mosaics affect the trade-offs between services provided by arable weeds

International audienc

Which structure and composition of agricultural land use mosaics to enhance multiple services provided by arable weeds?

International audienc

Quantifying the contribution of weeds to ecosystem (dis)services: from weed survey to proxy values

International audienc

Phénologie des adventices en grande culture : effet de la culture et de la localisation dans la parcelle (plein champ/bord de champ) sur la probabilité des adventices de fleurir et grainier

National audienc

A framework to estimate the contribution of weeds to the delivery of ecosystem (dis)services in agricultural landscapes

International audienceThere is a pressing need for indicators and methods to quantify the provision of ecosystem services as a prerequisite to identify management options that optimize trade-offs between services. Arable weeds provide multiple services and are thus a good model to evaluate such trade–offs. This flora provides trophic resources (flowers or seeds) that support pollinators and pest natural enemies (pollination and pest control services) but can also be harmful for crop production (disservice). To date, few indicators are available to quantify the contribution of weeds to ecosystem services or their harmfulness, and no indicators account for intraspecific variability in weed traits that result from contrasting growing conditions, notably the location of weeds within fields (field edge vs field core) and crop type. Here, we developed nine proxies for potential weed harmfulness (competition, harvest difficulties and future weed infestations) and weed contributions to resources provision to pollinators (bees, bumblebees and hoverflies) and pest natural enemies (carabid beetles, birds and parasitoid wasps). These nine proxies accounted for individual weed plant response to growing conditions (combination of within-field location by crop type) for 155 weed species, resulting in 967 unique situations (combinations of species by within-field locations by crop types). Apart from harvest difficulties, all proxies were positively correlated, i.e. harmfulness increased when services increased. Weed plants located on field edges had greater contributions to all proxies than those located in field cores, especially in cereal crops. We identified that small weed species with short life cycles and low competitiveness, presented the optimum proxy combination, i.e. high services and low harmfulness. The development of these proxies and the proposed framework provide new avenues for assessing trade-offs between multiple ecosystem services at different temporal (crop sequence) and spatial scales (landscape)