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

International audience; De nombreux travaux ont mis en évidence que les caractéristiques du paysage environnant les parcelles agricoles influencent les abondances d’ennemis naturels et le niveau de régulation biologiquedans les cultures. Les effets du paysage sur l’abondance de bio-agresseurs sont par contre encore peu étudiés. Les effets du paysage sur la régulation biologique sont parfois contradictoires, souventspécifiques aux sites et de ce fait encore peu généralisables. Des travaux récents suggèrent que ces variations de réponse peuvent résulter d’interactions entre gestion parcellaire et contexte paysager,avec des effets conditionnels du paysage selon le type de gestion parcellaire e…

Introduction du séminaire. SEBIOPAG-PHYTO déterminants agricoles parcellaires et paysagers des variations de niveaux de régulation biologique

Prod 2017-344b SPE équipe EA GESTAD INRA; National audience; Le niveau de compréhension des processus écologiques et de leurs interactions avec les activités agricoles est insuffisant pour que les agriculteurs mobilisent ou intègrent la biodiversité et ses services dans leurs décisions de gestion. En effet, la plupart des études portent sur la biodiversité taxonomique et peu sur la régulation biologique. Elles considèrent les activités agricoles à un grain grossier et à l’échelle annuelle, d’où une impossibilité d’identifier des modalités de conduite technique des exploitations agricoles utiles pour renforcer les régulations biologiques. En parallèle, l’intégration de résultats scientifique…

The DISCO-WEED project : disentangling the role of anthropic DISturbances and eCOlogical processes on WEED community assembly

EAGESTADINRA; The DISCO-WEED project : disentangling the role of anthropic DISturbances and eCOlogical processes on WEED community assembly. Sfécologie-2016, International Conference of Ecological Sciences

Comment favoriser les services écosystémiques assurés par la biodiversité des paysages agricoles ? Intérêts d’un réseau de sites d’observation à long terme

Atteindre l’objectif affiché de réduction du niveau d’usage de produits phytosanitaires tout en maintenant les niveaux de production des cultures implique la mise en place de stratégies de protection des cultures alternatives à la lutte chimique. L’adoption de pratiques plus favorables à la biodiversité dans les agroécosystèmes pourrait contribuer à augmenter les services de régulation biologique des ravageurs de culture. Il est établi que la biodiversité des milieux cultivés est modulée par des facteurs naturels et anthropiques agissant à différentes échelles spatiales, allant de la parcelle agricole au paysage, mais la compréhension des mécanismes écologiques qui produisent ces effets res…

Disentangling the effects of local and regional factors on weed community dynamics in agroecosystems

International audience; Ecological theories of community assembly have been used to understand and predict community structural changes in response to agricultural practices. This is a fundamental issue to design sustainable cropping system. Weed infestations are potentially an important threat to crop production. Factors affecting weed community composition and diversity have traditionally been studied at the within-field level, since it is generally assumed that the main drivers of weed dynamics are farming practices at this spatial scale. However, spatial dispersion and landscape characteristics may strongly impact weed diversity both at local and regional scales. Moreover, weeds can per…

Weed metacommunity dynamics in intensive farmland landscapes reveal complex interactions between local disturbance patterns and spatial dispersal

EAGESTAD INRA; Metacommunity theory represents an exciting framework to identify the ecological mechanisms shaping the spatio-temporal organization of species assembly. Among them, dispersal and niche-based processes have been proposed as major drivers of metacommunity dynamics, whose relative role has led to the emergence of distinct paradigms. Mass-effect emphasizes a greater influence of dispersal whereas patch quality is of primary importance in the species-sorting perspective. Weeds represent the basic trophic component in agricultural food webs, but may induce crop yield loss. Many weed species occur in both crop and non-crop areas such as field edges. Recent studies have revealed the…

Diversifying crop rotations with perennial forage crops: potential benefits for weed management & farmland biodiversity

Crop rotation may be used to prevent the continuous selection of weed species adapted to one crop type. However, today’s crop rotations are often very short and simple. We studied the impacts of introducing perennial forage crops into cereal-based crop rotations on weed vegetation. Large-scale weed surveys in 632 fields in western France suggested that the weed species composition varied most strongly between perennial alfalfa forage crops and six annual crops[1]. Comparisons of wheat fields before, during, and after perennial alfalfa suggested that weed communities vary in a cyclic way during such crop rotations. This may be beneficial for weed management (suppression of weed species probl…

The stability of crop production: trade-offs in pollination-dependent agriculture

EAGESTAD INRA; Historically, demand for increased crop production has been satisfied by agricultural practices that include land conversion into agricultural land and improvements in crop yield. The benefits of persisting in this approach are challenged by the existence of apparent yield plateaus for many major crops and of crop yield saturating responses to increasing levels of pesticides. Notably, despite the importance of yield stability and the empirical evidence that magnitude and stability of ecosystem functions do not necessarily co-vary positively, few studies on the stability of crop yield have been attempted. Here, we develop a model for crop yield dynamics in a spatially heteroge…

Spatial and temporal presence of grasslands maintain local weed diversity thanks to spatio-temporal dispersal process

EAGESTADINRA; In frequently disturbed environments, plant community assembly mainly results from spatial dispersal and temporal dispersal through seed bank. Here, we propose to quantify the relative contributions of temporal and spatial dispersal on weed species assembly in farmlands. Weeds are mostly annual plants that rely exclusively on seeds for perpetuation, the latter presenting various level of longevity and dispersal capacity according to the species. In farmland, arable fields surrounded by landscape with high proportion of grasslands harbor high level of weed diversity revealing important dispersal flux. Similarly, the presence of grasslands in the past history (i.e crop successio…

Skylarks trade size and energy content in weed seeds to maximize total ingested lipid biomass

International audience; tThe trade-off between forage quality and quantity has been particularly studied in herbivore organisms,but much less for seed eating animals, in particular seed-eating birds which constitute the bulk of win-tering passerines in European farmlands. The skylark is one of the commonest farmland birds in winter,mainly feeding on seeds. We focus on weed seeds for conservation and management purposes. Weedseeds form the bulk of the diet of skylarks during winter period, and although this is still a matter fordiscussion, weed seed predation by granivorous has been suggested as an alternative to herbicides usedto regulate weed populations in arable crops. Our objectives wer…

Ecological mechanisms shaping weed assembly in intensive farmland landscapes

EAGESTAD INRA; The ecological mechanisms shaping plants assemblages are multiple and scale-dependent. While the differentiation of resource patches may govern assembly rules at intermediate scales, the role dispersal processes is expected to decrease and the one of species interaction to increase from large to fine spatial scale. In this study, we investigate the contribution of these three processes to weed assembly based on a hierarchical sampling design conducted in 454 arable fields of the LTSER Zone Atelier ‘Plaine & Val de Sèvre’ from 2014 to 2016 . Using multiplicative diversity partitioning, the total field weed diversity was decomposed into four metrics, corresponding to difference…

LTSER platforms as a place-based transdisciplinary research infrastructure: learning landscape approach through evaluation

Context: Place-based transdisciplinary research involves multiple academic disciplines and non-academic actors. Long-Term Socio-Ecological Research (LTSER) platform is one concept with ~ 80 initiatives globally. Objectives: As an exercise in learning through evaluation we audited (1) the siting, construction and maintenance of individual LTSER platforms, and (2) them as a distributed infrastructure for place-based transdisciplinary research with focus on the European continent. Methods: First, we defined a normative model for ideal performance at both platform and network levels. Second, four surveys were sent out to the 67 self-reported LTSER platforms officially listed at the end of 2016.…

Can we economically afford significant reduction in herbicide and nitrogen use ? Experimental evidence in real fields says, yes we can !

EAGESTAD INRA; In Europe, several policies to limit the environmental externalities of agrochemicals have been implemented in the past decade. Yet, herbicides and fertilizers consumed over this period either have remained fairly constant or have increased. One main reason is that the fear of potential indirect negative effects on food production, hence profits. However, recent empirical studies have failed to detect a positive correlation between agrochemical use intensity and both productivity and profitability. With the present study we investigated in real farming conditions the relationships between economic benefits and weed control and nitrogen input. Through an innovative factorial e…

Species-specific song convergence in a moving hybrid zone between two passerines

Moving hybrid zones are receiving increasing attention. However, so far little is known about the proximate mechanisms underlying these movements. Signalling behaviour, by individuals engaged in interspecific sexual and aggressive interactions, may play a crucial role. In this study, we investigated song variation within a moving hybrid zone between two warblers, Hippolais polyglotta and H. icterina. In these species, song is involved in interspecific territoriality and, probably, in mixed pairings. We showed that allopatric populations of the two species are clearly acoustically differentiated. However, interspecific differences faded out in sympatry as a result of an overall pattern of co…

Gestion durable des ressources naturelles en plaine céréalière : le rôle central des milieux pérennes dans les agro-écosystèmes céréaliers

Untangling the effects of local and landscape structure on pest predation by natural enemies in an intensive crop agroecosystem

EAGESTAD INRA; In agricultural crops, the use of biological control to reduce pest damages thanks to predation by natural enemies is an important ecosystem service. Unfortunately, the numerous mechanisms driving the efficiency of the predation function in agroecosystems are and often confounding. In this study, we investigated how local covariates and farming landscape structure affect predation rates of crop pest species in an intensive agricultural landscape in mid-west France. In 2016, predation rates of aphid and weed seeds of one species were quantified in a total of 120 fields, comprising four different types of crops as well as grasslands, selected along two landscape gradients: prop…

Assortative pairing for boldness and consequences for reproductive success in Montagu’s harrier

Abstract Behavioural combination within pairs depending on personality and plasticity might influence reproductive success. However, studies testing this hypothesis are rare, especially in the case of monogamous species with bi-parental care in which the sexes exhibit different behavioural roles. In this study, we investigated the pairing patterns for both boldness and boldness plasticity in Montagu’s harriers (Circus pygargus), a species with sex-specific care, and the consequences for their reproductive success. We measured individual boldness and plasticity for both sexes, and we assessed the pairing pattern in the Montagu’s harrier population for these two traits. We calculated four ind…

Les espèces adventices, indispensables à la production agricole dans les systèmes à bas intrants

National audience; Le défi principal de l’agriculture aujourd’hui est la conception de systèmes de culture (SdC) permettant de limiter le recours aux intrants chimiques, tout en régulant les bio-agresseurs des cultures et en maintenant le potentiel de production et le revenu des exploitants agricoles. La flore adventice est un exemple emblématique de ce défi et un obstacle majeur aux objectifs du plan Ecophyto ; les herbicides représentent une part importante des produits phytosanitaires utilisés. L’agroécologie repose sur le postulat que la biodiversité, de par ses fonctions et les services écosystémiques (ex. biocontrôle, pollinisation) qu’elle sous-tend, pourrait compenser l’usage d’intr…

Impact des techniques agricoles sur l’assemblage des communautés adventices

National audience; Les pratiques agricoles jouent un rôle majeur dans le devenir des espèces adventices comme le montre les changements importants de composition et la perte de diversité des flores adventices depuis 1950. Malgré ce constat, les processus de filtrage des espèces par les différentes pratiques agricoles restent encore mal connu. Dans cette étude, nous avons cherché à mettre en évidence les liens entre les traits des adventices et leur réponse à des pratiques culturales. Dans un premier temps, une analyse RLQ a été conduite sur 218 parcelles de blé d’hiver issues du réseau Biovigilance Flore couvrant toute la France pour déterminer quels traits des adventices répondent aux diff…

L’intégration d’une luzerne de 3 ans dans la rotation: un atout agronomique, économique et environnemental !

National audience; En 2010, l’INRA et le CNRS ont étudié les pratiques de gestion des adventices en lien avec les systèmes de culture (SdC) dans une zone de grandes cultures des Deux-Sèvres. A partir d’entretiens avec 28agriculteurs, cette étude a permis d’identifier les stratégies agronomiques permettant aux agriculteurs de réduire leur utilisation d’herbicides, voire de s’en passer totalement (AB). La comparaison de la performance de durabilité de ces 28 SdC contrastés en termes de niveau d’usage d’herbicides a également été réalisée. L’intégration d’une prairie temporaire de 3 ans, type luzerne, ressort comme un levier agronomique fort pour réduire l’usage d’herbicides dans la rotation. …

Bees increase oilseed rape yield under real field conditions

prod 2018-210 EA GESTAD INRA; International audience; Oilseed rape (OSR, Brassica napus L.) is a common crop found in many European agricultural landscapes. It ispollinated by a wide variety of insects, but the reported contribution of pollinators to yield varies widely betweenstudies (from 0 to 50%). Moreover, such a contribution has seldom been estimated at the field scale in realfarming conditions. We analysed OSR yields in response to insect pollination; over four years, at two differentscales: farm fields and individual plants. We used both empirical and experimental approaches along a gradientof pollinator diversity and abundance. The empirical approach was based on farm surveys (151 …

Is the effect of grassland on weed diversity similar when present in the landscape or in the crop succession?

EAGESTADINRA; Spatio-temporal seed dispersal is a major process in structuring annual plant communites. However, few emipirical studies have quantified the relative contribution of seed dormancy and seed dispersal on annual plant diversity. In agroecosystems, weeds which are mostly annual species producing dormant seeds can be found both in annual row crops and in semi-natural habitats such as grasslands (fig. 1). Spatial mass effect from grasslands to annual crops have been reported to support weed diversity in annual crops. Similarly, the presence of grasslands in crop successions increases weed diversity in the following annual crops. Both temporal and spatial dispersal from grasslands m…

Should we manage weeds for bees ?

National audience

Reconciling pesticide reduction with economic and environmental sustainability in arable

National audience

Species-specific song convergence in a moving hybrid zone between two passerines

International audience; Moving hybrid zones are receiving increasing attention. However, so far little is known about the proximate mechanisms underlying these movements. Signalling behaviour, by individuals engaged in interspecific sexual and aggressive interactions, may play a crucial role. In this study, we investigated song variation within a moving hybrid zone between two warblers, Hippolais polyglotta and H. icterina . In these species, song is involved in interspecific territoriality and, probably, in mixed pairings. We showed that allopatric populations of the two species are clearly acoustically differentiated. However, interspecific differences faded out in sympatry as a result of…

Towards sustainable and multifunctional agriculture in farmland landscapes: Lessons from the integrative approach of a French LTSER platform

International audience; Agriculture is currently facing unprecedented challenges: ensuring food, fiber and energy production in the face of global change, maintaining the economic performance of farmers and preserving natural resources such as biodiversity and associated key ecosystem services for sustainable agriculture. Addressing these challenges requires innovative landscape scale farming systems that account for changing economic and environmental targets. These novel agricultural systems need to be recognized, accepted and promoted by all stakeholders, including local residents, and supported by public policies. Agroecosystems should be considered as socio-ecological systems and alter…