In this investigation we analyzed the spatiotemporal variation of ecosystem service values (ESVs) and its correlation with numerous environmental factors (EFs) for the karst region of Northwest Guangxi, China, from 1985 to 2005 using remote sensing, geographic information systems (GIS) and statistical techniques. The results indicate that historically ESVs for this karst region decreased from 1985 (109.652 billion Yuan) to 1990 (88.789 billion Yuan) and then increased at the turn of the twenty-first century. However, the ESVs in both 2000 (103.384 billion Yuan) and 2005 (106.257 billion Yuan) never achieved the level recorded in 1985. The total of nutrient cycling, organic production and gas regulation combined were 72.69, 64.57, 70.18 and 72.10% of ESVs in 1985, 1990, 2000 and 2005, respectively. In contrast, the ESVs of water conservation, soil reservation, recreation and culture were determined to be relatively low contributing only 17.44, 23.82, 19.26 and 24.76% of total ESVs, respectively, during these four years. With regards to the spatial distribution of ESVs, larger values were recorded in the west and smaller ones recorded in the east. The most significant factors that were deemed to influence ESVs are annual rainfall, per capita cropland, slope and vegetation coverage. Annual rainfall and slope exert a negative force, whereas per capita cropland and vegetation coverage exert a positive force on ESVs. The results of the study would suggest that ecosystem conditions of this important karst region have been improved as the result of the implementation of rocky desertification control policies.

The recognition of nature in the resolution of societal challenges has been growing in relevance. This recognition has been associated with the development of new concepts from science and policy such as natural capital, ecosystem services, green infrastructure, and more recently Nature-Based Solutions (NBS). NBS intends to address societal challenges in an effective and adaptive form providing economic, social, and environmental benefits. The overall aim of this PhD thesis is to develop an environmental and economic assessment of NBS for highly urbanised territories based on rationales and models underpinning ecosystem services, urban/landscape ecology, and life cycle thinking approaches. This combined evaluation approach would help to better understand if NBS are cost-effective or not. The aim is developed according to four specific objectives. The first objective corresponds to the characterisation of NBS in relation to urban contexts and the problematics that they can help to address or mitigate. To achieve this objective a critical review on the study of the relationship between NBS, ecosystem services (ES) and urban challenges (UC) was developed. As a main output, a graph of plausible cause-effect relationships between NBS, ES and UC is obtained. The graph represents a first step to support sustainable urban planning, moving from problems (i.e. urban challenges) to actions (i.e. NBS) to resolutions (i.e. ES). The second objective corresponds to the definition of an adequate set of biophysical and monetary assessment methods and indicators to evaluate the value of NBS in urbanised contexts. To achieve this objective, a review of existing methods on ecosystem services valuation, life cycle cost analysis and life-cycle assessment are developed. The review takes into account specific constraints such as easiness to use and availability of data. At the end, potential methods and indicators were selected, which will be later integrated in the combined assessment framework. The third objective corresponds to the design of a combined assessment framework integrating methods from life cycle assessment, landscape/urban ecology and ecosystem services that quantifies the environmental and economic value of NBS informing about the cost-effectiveness of its entire life cycle. To achieve this objective, a conceptual framework is developed. From it, a system dynamics model of ecosystem (dis)services is developed and coupled with a life cycle assessment method. The combined evaluation is tested with a relevant NBS type (i.e. urban forest) in a case study in the metropolitan area of Madrid. The fourth objective is the development of a decision support (DSS) tool that integrates the assessment framework as part of iterative design processes in urban planning and landscape design. The DSS intends to enhance the interrelation between science, policy and planning/design. To achieve this objective a user-friendly web-based prototype DSS on NBS, called NBenefit$®, is developed. The prototype DSS provides the user a simple form of quantifying the provision of multiple ES and costs over the entire life cycle (implementation, operational life, and end-of-life) of NBS. This thesis contributed to the characterisation of NBS and its environmental and economic assessment to inform urban planning and landscape design processes, allowing decisions that are more informed. / Il riconoscimento della natura nella risoluzione delle sfide sociali è diventato sempre più importante. Questo riconoscimento è stato associato allo sviluppo di nuovi concetti provenienti dalla scienza e dalla politica, come il capitale naturale, i servizi ecosistemici, le infrastrutture verdi e, più recentemente, le soluzioni basate sulla natura (NBS). NBS intende affrontare le sfide della società in una forma efficace e adattabile fornendo benefici economici, sociali e ambientali. Lo scopo di ricerca di questa tesi di dottorato è quello di sviluppare una valutazione ambientale ed economica delle NBS per territori altamente urbanizzati basata su logiche e modelli che hanno alla base i servizi ecosistemici, l'ecologia urbana e paesaggistica e degli approcci di approcio life cycle. Questo quadro di valutazione combinato aiuterebbe a capire meglio se le NBS sono costo effetive e se contribuiscono a uno sviluppo resiliente e sostenibile. Questo scopo di ricerca è sviluppato secondo quattro obiettivi specifici. Il primo obiettivo corrisponde alla caratterizzazione delle NBS in relazione ai contesti urbani e alle problematiche che possono aiutare ad affrontare o mitigare. Per raggiungere questo obiettivo è stata sviluppata una revisione critica dell letteratura sullo studio della relazione tra NBS, servizi ecosistemici (ES) e sfide urbane (UC). Come risultato principale, si ottiene un grafico delle relazioni causa-effetto plausibili tra NBS, ES ed UC. Il grafico rappresenta un primo passo per supportare la pianificazione urbana sostenibile, passando dai problemi (es. UC) alle azioni (es. NBS) alle risoluzioni (es. ES). Il secondo obiettivo corrisponde alla definizione di un set di metodi e indicatori di valutazione biofisica e monetaria adeguate per valutare il valore della NBS in contesti urbanizzati. Per raggiungere questo obiettivo, viene sviluppata una revisione dei metodi esistenti sulla valutazione dei servizi ecosistemici, l'analisi dei costi del ciclo di vita e la valutazione del ciclo di vita. La revisione tiene conto di vincoli specifici come la facilità d'uso e la disponibilità dei dati. Alla fine, sono stati selezionati potenziali metodi e indicatori, che saranno successivamente integrati nel quadro di valutazione combinato. Il terzo obiettivo corrisponde alla progettazione del quadro di valutazione combinato, integrando metodi di valutazione del ciclo di vita, ecologia paesaggistica / urbana e servizi ecosistemici che quantifica il valore ambientale ed economico della NBS informando sull'efficacia in termini di costi del suo intero ciclo di vita. Per raggiungere questo obiettivo, prima viene sviluppato un quadro concettuale. Da esso, viene sviluppato un modello di dinamica di sistemi per calcolare i servizi (e disservici) ecosistemici, il quale è interrelazionato con un metodo di valutazione life cycle. Questa valutazione combinata viene testata con un tipo di NBS pertinente (foresta urbana) in un caso di studio nell'area metropolitana di Madrid. Il quarto obiettivo è lo sviluppo di uno strumento di supporto decisionale (DSS) che integri il quadro di valutazione come parte dei processi di progettazione iterativa nella pianificazione urbana e nella progettazione del paesaggio. Il DSS intende migliorare l'interrelazione tra scienza, politica e pianificazione / progettazione. Per raggiungere questo obiettivo è stato sviluppato Nbenefit$® un prototipo di DSS online per la valutazzione NBS di facile uso. Il prototipo DSS fornisce all'utente una forma semplice per quantificare multipli ES e costi (internalizatti o no) durante l'intero ciclo di vita (implementazione, vita operativa e fine vita) del NBS. In conclusione, questa tesi ha contribuito alla caratterizzazione di NBS e alla sua valutazione ambientale ed economica per informare i processi di pianificazione urbana e progettazione del paesaggio, consentendo decisioni più informate.

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This thesis addresses three interlinked aspects that are relevant for mainstreaming Nature-based Solutions in urban planning. The first aspect concerns the integration and use of ecosystem service knowledge in spatial planning. A literature review aimed at analysing practical applications of ecosystem services in real-life planning processes and instruments reveals both the outcomes generated and the procedures adopted to integrate them, as well as the main advantages, constraints, enabling factors, and open issues associated with ecosystem service knowledge integration in spatial planning processes and instruments. The second aspect is related to the use of spatial assessments of ecosystem service demand to support an effective planning of Nature-based Solutions at the city scale. An approach is developed to allocate and prioritize Nature-based Solutions in cities in order to deliver ecosystem services for addressing the existing urban challenges while maximising the benefits for residents. The approach is tested in the case study area of Valletta (Malta), identifying the potential sites for the implementation of eleven types of Nature-based Solutions, assessing the demand for five priority ecosystem services, and identifying what type(s) of Nature-based Solutions, among the eleven proposed, should be implemented in each potential site, as well as the sites that should be prioritized first. The third aspect involves the promotion of the implementation of Nature-based Solutions in urban plans through the use of suitable policy instruments. A matrix that links the suitable instruments identified to different typologies of Nature-based Solutions reveals the range of instruments that can be deployed to promote the implementation of each type of Nature-based Solution. The matrix is then applied to analyse which instruments are currently deployed and which are not in the two urban plans covering the case study area of Valletta, hence the missing opportunities that could be further exploited.

Urban green spaces are put under high pressure due to increasing population density in cities. This problem will potentially accelerate where the densification in the cities continues. Consequently, this sets high requirements on the management, if the green spaces are to generate the benefits and values that are associated with greens spaces as urban parks. One way to increase these benefits and values could be to incorporate ecosystem services and indicators for ecosystem services in a multi-stakeholder management system. Is it possible that ecosystem service indicators could facilitate collaboration between stakeholders and thus improve the value of urban green space? This master thesis aimed to identify ecosystem service indicators for a green space and incorporate them in a multi-stakeholder management system. The study was made to clarify if indicators can facilitate collaboration between stakeholders and thus improve the management of an urban green space. In order to achieve that, the first step was to let the stakeholders express what they desired the green space to generate in terms of benefits and values. These expressed benefits and values were formulated into target variables which were linked with the ecosystem services that the green space was assessed to generate if the target variables are achieved. A literature study was conducted to identify applicable indicators for the chosen ecosystem services. These indicators were quantified and incorporated into an already existing management system. This management system performed as a framework and a fundament which was further developed to incorporate more functions as indicators and ecosystem services. The thesis resulted in two identified indicators for ten ecosystem services and the development of a multi-stakeholder management system. Identified indicators were birds and compliant seating. Birds were identified as an indicator because they indicated many of the same ecosystem services as the ones that are generated in the green space. These ecosystem services are linked with the benefits and values that are associated with the target variables. In addition, the birds were chosen because they were possible to quantify. Compliant seating was the second indicator, and it has the potential to function as a control indicator as it can be seen as a manifestation of the cultural ecosystem services generated at the green space. A multi-stakeholder management system was developed with the incorporation of indicators for ecosystem services. The developed management system aimed to facilitate the collaboration between stakeholders with the use of ecosystem service indicators. Taken together, the findings suggest a role for ecosystem service indicators in multi-stakeholder management plans to improve the value of green spaces. / Grönytor i städer är satt under hög press på grund av ökande befolkningstäthet vilket leder till att fler människor behöver dela på samma mängd urban grönyta. Detta fenomen ökar kraven på förvaltningen av grönytor då de behöver generera fler nyttigheter och mera värde. Ett sätt att öka dessa värden skulle kunna vara att använda sig av indikatorer för ekosystemtjänster inom ett förvaltningssystem där flera förvaltare verkar. Är det möjligt att indikatorer för ekosystemtjänster kan underlätta samarbetet mellan olika förvaltare och därigenom öka värdet av en grönyta?   Den här masteruppsatsen hade målet att identifiera indikatorer för ekosystemtjänster genererade av en grönyta och sedan inkorporera dem i en förvaltningsmetod som ökar samverkan mellan förvaltare. Studien syftade till att tydliggöra om användandet av ekosystemtjänstindikatorer kan underlätta samarbetet av mellan olika förvaltare för att förbättra förvaltningen av en grönyta. Det första steget för att åstadkomma detta var att låta förvaltarna uttrycka vilka värden och nyttigheter de vill att grönytan skulle skapa. Dessa värden och nyttigheter formulerades som målvariabler vilka länkades till de ekosystemtjänster som grönytan bedömdes generera. Genom en litteraturstudie identifierades indikatorer som kunde indikera de ekosystemtjänster som genererades vid grönytan. Indikatorerna kvantifierades och inkorporerades in i ett redan existerande förvaltningssystem.   Studien resulterade i två identifierade indikatorer och i utvecklandet av ett förvaltningssystem som underlättar samverkan genom användandet av indikatorer. Fåglar identifierade som en indikator på grund av att fåglar indikerade samma ekosystemtjänster som genereras på grönytan. Fåglar valdes också för att det var möjligt att kvantifiera fåglarna vid grönytan. Villkorlig sittplats var den andra indikatorn och den har möjligheten att fungera som en kontrollindikator eftersom den kan beskrivas som en manifestation av de ekosystemtjänster som genereras på grönytan. Sedan så utvecklas även ett förvaltningssystem där indikatorerna inkorporerades. Förvaltningssystemet hade målet att underlätta samverkan mellan de olika förvaltarna med hjälp av indikatorerna. Sammanfattningsvis så bedöms det att indikatorer för ekosystemtjänster har potentialen att användas i ett förvaltningssystem och därigenom kunna bidra till att öka värdet av grönytan.

Denna studie undersöker processkedjan för att implementera stadsgrönska och ekosystemtjänster i urbana miljöer. Hur kedjan ser ut från det att ett uppdrag ges av regeringen, till arbetet vidare hos den aktuella myndigheten för att sedan komma till hur arbetet tas vid ute hos kommuner och andra berörda aktörer. Ekosystemtjänster är de fördelar som vi människor får indirekt och direkt av naturen. Vi är beroende av att ekosystemen fortsätter producera tjänster som är livsviktiga för människans hälsa, välbefinnande samt för hela vår existens. Ett gemensamt arbete och hänsynsfullt nyttjande av våra resurser behövs för att säkerställa ekosystemtjänsterna. Att bevara, utveckla och nyskapa tätortsnära natur och grönområden kan resultera i stora samhällsvinster och att integrera ekosystemtjänster i den fysiska planeringen är ett steg i rätt riktning. Två etappmål togs fram 2018, där det ena målet innebär att kommunerna ska ha tillgång till en utvecklad metod gällande integrering av stadsgrönska och ekosystemtjänster i urbana miljöer senast år 2020. Det andra målet innebär att en majoritet av kommunerna senast 2025 ska ta tillvara och integrera ekosystemtjänster och stadsgrönska i planering, byggande och förvaltning. Studiens resultat bygger på hur långt kommunerna har kommit i arbetet med de två etappmålen, samt Boverkets insats i arbetet bakom den utvecklade metoden och med att nå ut med informationen till kommuner och andra aktörer. Resultatet innefattar även arbetet tillsammans med Naturvårdverkets då uppdraget skulle ske i samverkan med dem. Detta har genomförts med både kvalitativa och kvantitativa metoder, genom intervjuer och enkätutskick. / This study investigates the process chain for implementing urban greenery and ecosystem services in urban environments. This is done from the time the assignment is given by the government to the relevant authority, the continued work there, on to the work out at the municipalities and other relevant actors. Ecosystem services are the benefits that we humans receive indirectly and directly by nature. We are dependent on the ecosystems continuing to produce services that are vital to human health, well-being and for our entire existence. Commonly work and careful use of our resources are needed to ensure ecosystem services. Preserving, developing and innovating urban and green areas can result in great social benefits and integrating ecosystem services into physical planning is a step in the right direction. Two stagegoals were developed in 2018, where one goal means that the municipalities should have access to a developed method regarding the integration of urban greenery and ecosystem services in urban environments by 2020. The second goal means that a majority of the municipalities must use and integrate urban greenery and ecosystem services by 2025 at the latest, in planning, construction and management. The study result is based on how far the municipalities have come to work on the two stagegoals, as well as Boverkets work behind the developed method and with reaching out with the information to the municipalities and other concerned. The result also includes the work in conjunction with Naturvårdsverket when the assignment would take place in collaboration with them. This has been done with both qualitative and quantitative methods, through interviews and questionnaires.

År 2018 ska betydelsen av biologisk mångfald och värdet av ekosystemtjänster vara allmänt kända och integreras i ekonomiska ställningstaganden, politiska avväganden och andra beslut i samhället där så är relevant och skäligt. Så lyder ett av etappmålet som beslutades av regeringen år 2012. Idag vet vi att endast delar av målet kommer kunna nås. Denna studie omfattar en kartläggning av begreppet ekosystemtjänst i Sveriges samtliga översiktsplaner och fördjupade översiktsplaner. Vidare har en granskning av tre bostadsbyggnadsprojekt i Stockholms län genomförts, där ekosystemtjänster i planeringen från översiktsplan till genomförande varit fokuspunkt. Av studiens första del, kartläggning av begreppet, framgick det att 116 av 290 kommuner har använt begreppet ekosystemtjänst i sin översiktsplan. De senaste tre åren är det totalt fler antagna översiktsplaner där begreppet behandlas än utan. I studiens andra del granskades översiktsplaner, planhandlingar och genomförandeavtal från projekt i Täby, Nacka och Haninge kommun. Granskningen är baserad på textanalys och platsbesök, resultatet visade att kommunerna har en hög ambition gällande arbetet med ekosystemtjänster. Det finns samband mellan visioner i översiktsplan och bestämmelser i detaljplan. I avtalen för genomförandet av detaljplanerna binds exploatörerna till att arbeta efter gestaltningsprogram och hållbarhetsprogram vilka reglerar hänsynstagandet av ekosystemtjänster. Begreppet ekosystemtjänst används för att visa den nytta människan får från naturens arbete. Vi är beroende av att ekosystemen fortsätter producera tjänster, de är livsviktiga för vår folkhälsa och vårt välbefinnande. Ett gemensamt arbete och hänsynsfullt nyttjande behövs för att säkerställa ekosystemtjänsterna. Det kan resultera i stora samhällsvinster att bevara, utveckla och nyskapa tätortsnära natur och grönområden. Att integrera ekosystemtjänster i den fysiska planeringen är ett steg på vägen. Översiktsplaneringen visar inriktningen för kommunens samhällsplanering och konturerna av den framtida fysiska strukturen, den vägleder kommande detaljplaner och bygglov. Översiktsplanen spelar en nyckelroll för ekosystemtjänsternas framtid eftersom det där finns stora möjligheter att belysa deras mycket betydelsefulla värde. För att uppnå visionerna i översiktsplaneringen krävs möjlighet att förverkliga dessa i detaljplanen. För att säkra ekosystemtjänsternas producerande förmåga krävs en tydlig och ändamålsenlig lagstiftning. Kunskapen och medvetenheten om dess livsviktiga förmåga måste öka. Alla måste se sin del i det gemensamma ansvaret och arbeta för ett hållbart samhälle. / In 2018 the meaning of biodiversity and the value of ecosystem services should be general knowledge and integrated into economical standpoints, political considerations and other decisions where relevant and reasonable. This is one of the milestone targets that the Swedish government decided in 2012. We know today that only parts of this target will be reached. This study includes a survey regarding the concept of ecosystem service in Sweden, all the local authority comprehensive planning, and an examination of three housing projects in Stockholm’s county where ecosystem services were the focal point during the comprehensive planning. In the first part of the study, which concentrates on surveying the concept of ecosystem services, it can be shown that 116 of 290 municipalities have been using the concept in their local authority comprehensive planning. Furthermore, the concept is used more often than not during the last three years in local authority comprehensive planning. In the second part of the study the outline planning was examined, plan handlings and implementation contracts from projects in Täby, Nacka and Haninge municipality. The research was based on text analysis and on-site inspection. The results from the research showed that the municipalities have a high ambition regarding working with ecosystem services, and that there exist a correlation between the visions in the local authority comprehensive planning and regulations in the detailed developed plan. In the agreement the developers are bound to work according to implementation contracts and sustainability program which regulate the considerations of ecosystem services. The concept of ecosystem services is used to show which benefits we humans receive from nature’s work. We are dependent on continual ecosystem services, which are also essential to the public health and wellbeing. Joint effort and a considerate use of ecosystem services is needed to keep them intact. It can result in large profit for society to preserve, develop and recreate nature and green areas in population centers. To integrate ecosystem services in the physical planning is a step in the right direction. The local authority comprehensive planning show the direction for the municipality’s community planning, and the outline of the future physical structure, it also serves to guide upcoming detailed development plans and building acts. The local authority comprehensive planning plays a key part in the ecosystem services future, since its importance can be illustrated within. To reach the visions of the local authority comprehensive planning and the opportunity to actualize it in the detailed development plan is required. To secure the continued functionality of the ecosystem services, a clear and purposive legislation is required. An increase in knowledge and awareness of ecosystem services is essential, and everyone must see their part in the in our common responsibility and work toward a sustainable society.

Crop rotation may be used to prevent the continuous selection of particular weed species adapted to one crop type. This might be useful for weed management, economy in herbicide applications and promoting biodiversity. Common simple crop sequences might be diversified by introducing perennial forage crops. Impacts of such perennial crops on weeds were studied with four approaches : 1) Large-scale weed surveys in 632 fields in western France showed that weed species composition differed most strongly between perennial alfalfa crops and annual crops. Comparisons of fields before, during and after perennial alfalfa suggested that community composition varies in a cyclic way during such crop rotations. Several weed species problematic in annual crops were suppressed during and after perennial crops, but the appearance of other species led to equal or even higher plant diversities. 2) A 3-year field experiment with contrasting crop management options allowed an investigation of the underlying mechanisms for this: The absence of soil tillage reduced weed emergence but increased the survival of established plants. The permanent vegetation cover and frequent hay cuttings reduced weed growth, plant survival and seed production. 3) Greenhouse experiments testing the regrowth ability of individual plants after cutting showed strong differences between species and functional groups. An two-factorial experiment suggested that the negative impacts of cutting and competition on weed growth were mainly additive. 4) Special measurements of weed seed predation in the field experiment showed positive correlations with vegetation cover, indicating that this ecosystem service may be particularly fostered by perennial crops. Consistent preferences of seed predators for certain weed species indicates that seed predation may be another cause of the observed weed community shifts.

Le modèle input-output régional environnementalisé développé dans la thèse de M. Cordier suggère qu’il serait possible de restaurer 25% des surfaces naturelles de nourriceries de poissons détruites dans l’estuaire de la Seine entre 1834 et 2004. Le modèle suggère que la mesure de restauration pourrait augmenter de 15% à 23% la biomasse de soles produite dans l’estuaire par rapport à une situation sans mesure. Quant à l’effet des coûts de restauration sur les agrégats macroéconomiques (PIB, emploi, etc.), il génère une diminution qui ne dépasse pas 0,5% par rapport à une situation sans mesure. Le modèle montre cependant que trois secteurs sont particulièrement touchés par la mesure, leur bénéfice étant considérablement réduit. Cela indique le compromis à réaliser entre les objectifs écologiques à long terme et les objectifs économiques sectoriels à court terme. La quantification des compromis par le modèle constitue un atout utile aux processus de décision participatifs multicritère / The regional green input-output model developed in Mateo Cordier's PhD shows that it seems possible to restore 25% of the natural areas of fish nurseries destroyed in the Seine estuary between 1834 and 2004. The model suggests that the restoration measure could increase between 15% and 23% the biomass of sole generated by the estuary compared to a situation without measure. Regarding the impact of restoration costs on macro-economic indicators (GDP, employment, etc.), it generates a decrease that does not exceed 0,5% compared to a situation without measure. However, the model shows that three sectors are particularly impacted by the measure. Their benefits are considerably reduced. This shows the trade-off that occurs between ecological targets on the long run and economic targets on the short run. The quantification of such trade-offs in the model is particularly useful to public participation in decision-making. / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

La rotation de cultures peut être utilisée pour empêcher la sélection continue d’espèces adventices adaptées à un type de culture. Elle pourrait favoriser la gestion des adventices, l’économie d’herbicides et la biodiversité. Les successions de cultures simples d’aujourd’hui pourraient être diversifiées par des cultures fourragères pérennes. Les impacts des ces cultures sur les adventices ont été étudié utilisant quatre approches : 1) Des relevés d’adventices sur 632 champs dans l’ouest de la France ont montré que la composition spécifique varie le plus entre des cultures fourragères pérennes et des cultures annuelles. Une comparaison des champs avant, pendant, et après des cultures fourragères pérennes a suggéré que la composition des communautés varie d’une manière cyclique pendant ces rotations. Plusieurs espèces problématiques dans des cultures annuelles ont été supprimées pendant et après les cultures pérennes, mais l’apparition d’autres espèces a produit une diversité de plantes comparable, voire supérieure. 2) Une expérimentation au champ de trois ans avec des modes de gestion contrastés a permis d’étudier les mécanismes sous-jacents: L’absence de travail du sol a réduit la levée des adventices, mais a augmenté la survie des plantes adultes. Le couvert végétal permanent et les fauches fréquentes ont réduit la croissance, la survie des plantes et la production de graines. 3) Des expérimentations sous serre analysant la croissance poste fauche de plantes individuelles ont montré des différences importantes entre espèces et groupes fonctionnels. Une expérimentation à deux facteurs a suggéré que les impacts négatifs de la fauche et de la compétition sur la croissance des adventices ont été additifs. 4) Des mesures spéciales de prédation de graines d’adventices sur l’expérimentation au champ ont montré des corrélations positives avec le couvert végétal et la prédation, indiquant une importance particulière de ce service écosystémique dans des cultures pérennes. La préférence des graines de certaines espèces montre que la prédation de graines peut être une autre cause des changements de communautés d’adventices. / Crop rotation may be used to prevent the continuous selection of particular weed species adapted to one crop type. This might be useful for weed management, economy in herbicide applications and promoting biodiversity. Common simple crop sequences might be diversified by introducing perennial forage crops. Impacts of such perennial crops on weeds were studied with four approaches : 1) Large-scale weed surveys in 632 fields in western France showed that weed species composition differed most strongly between perennial alfalfa crops and annual crops. Comparisons of fields before, during and after perennial alfalfa suggested that community composition varies in a cyclic way during such crop rotations. Several weed species problematic in annual crops were suppressed during and after perennial crops, but the appearance of other species led to equal or even higher plant diversities. 2) A 3-year field experiment with contrasting crop management options allowed an investigation of the underlying mechanisms for this: The absence of soil tillage reduced weed emergence but increased the survival of established plants. The permanent vegetation cover and frequent hay cuttings reduced weed growth, plant survival and seed production. 3) Greenhouse experiments testing the regrowth ability of individual plants after cutting showed strong differences between species and functional groups. An two-factorial experiment suggested that the negative impacts of cutting and competition on weed growth were mainly additive. 4) Special measurements of weed seed predation in the field experiment showed positive correlations with vegetation cover, indicating that this ecosystem service may be particularly fostered by perennial crops. Consistent preferences of seed predators for certain weed species indicates that seed predation may be another cause of the observed weed community shifts. / Fruchtfolgen können dazu dienen, die kontinuierliche Selektion von Unkrautarten zu verhindern, die an eine bestimmte Kultur angepasst sind. Dies könnte dem Unkrautmanagement, der Einsparung von Herbiziden, und der Biodiversität dienen. Heutige, sehr einfache Furchtfolgen könnten durch mehrjährige Futterkulturen diversifiziert werden. Die Einflüsse solcher mehrjähriger Kulturen auf Unkräuter wurden in vier Ansätzen untersucht : 1) Vegetationsaufnahmen auf 632 Feldern in Westfrankreich zeigten, dass die Unkrautzusammensetzung zwischen mehrjährigen Futterkulturen und einjährigen Kulturen stark variiert. Der Vergleich von Feldern vor, während und nach mehrjährigen Futterkulturen legte nahe, dass die Pflanzengemeinschaft während solcher Fruchtfolgen zyklisch variiert. Mehrere problematische Unkrautarten wurden während und nach den mehrjährigen Kulturen zurückgedrängt. Das Auftauchen anderer Arten führte jedoch zu einer gleichbleibenden oder leicht erhöhten Pflanzenvielfalt. 2) Ein dreijähriger Feldversuch mit verschiedenen Bearbeitungsoptionen ermöglichte es, die zugrunde liegenden Mechanismen zu untersuchen: Die fehlende Bodenbearbeitung hat das Auflaufen der Unkräuter reduziert und das Überleben der adulten Pflanzen erhöht. Die permanente Vegetationsbedeckung und die häufigen Heuschnitte haben das Wachstum, das Überleben und die Samenproduktion vermindert. 3) Gewächshausexperimente zum Nachwachsen von Unkrautpflanzen nach Heuschnitten zeigten große Unterschiede zwischen verschiedenen Arten und funktionellen Gruppen. Ein Experiment mit zwei Faktoren lässt vermuten, dass die negativen Effekte der Schnitte und der Konkurrenz auf das Unkrautwachstum sich addieren. 4) Spezielle Messungen der Prädation von Unkrautsamen auf den untersuchten Feldern zeigten positive Korrelationen mit der Vegetationsbedeckung, was auf eine besondere Wichtigkeit dieser Ökosystemdienstleistung in ausdauernden Kulturen hindeutet. Die Präferenz von bestimmten Samenarten deutet darauf hin, dass Samenprädation ein weiterer Grund für die beobachteten Änderungen der Unkrautgemeinschaften sein kann.