Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: South Africa's system of socio-economic development planning is complex and ine ective. There are many regulatory authorities involved, often with unclear responsibilities and inadequate procedures of implementing objectives. Planning for development in South Africa needs to take various factors into account. Economic growth is pursued, while social imbalances are addressed and the environment is protected against unreasonable damage. The term Sustainable Development is an important concept in the vision of many of the regulating authorities, however, the implementation of sustainability is di cult. This study considers an approach which aligns activities in a specifi ed region to the vision and objectives of the applicable regulatory authorities, as an alternative to achieving objectives strictly through enforcing regulations. This thesis developed an integrated evaluation model which can be used to evaluate the alignment of a small-scale farm to the visions and objectives of certain regulatory authorities. Four small-scale farms in the Letaba catchment of the Limpopo Province were used as a case study to be evaluated against national and regional development visions. On a national level the National Development Plan (NDP), the National Framework for Sustainable Development (NFSD), the Integrated Sustainable Rural Development Strategy (ISRDS) and the principles of Water Allocation Reform (WAR) were regarded. For regional categorisation, the relevant municipal Integrated Development Plan (IDP), Spatial Development Framework (SDF), Local Economic Development (LED) plan and the applicable Catchment Management Strategy (CMS) were considered. The Letaba catchment area has speci c development constraints regarding water. For this reason, the impact the four farms have on the water of the region was evaluated in addition to their alignment with regional development visions. The hydrological evaluations were performed through the use of the Soil and Water Assessment Tool. Hereby it was determined whether objectives of development planning were realistic in terms of water availability. It was established that the location of a farm is a determining factor of the impact it has on the catchment area's water supply. The developed Integrated Evaluation Model combined all the visions and objectives of the mentioned strategic documents to speci cally assess the contribution a small-scale farm makes. The evaluation results provide insight into the alignment of activities to the ideals of a region and can be useful when formulating actions to reach a common vision. Small-scale farms are well-aligned to the objectives of WAR, the CMS and ISRDS. The farms have a limited contribution to the ideals of the NDP and NFSD and results against the IDP, the SDF and the LED di er considerably for each farm. Furthermore, the results of the farms' alignment with regional objectives do not correspond to the hydrologically ideal locations. Therefore, the development of small-scale farming should take hydrological information into consideration. The Integrated Evaluation Model proves to be valuable, understandable and applicable to evaluate the alignment of small-scale farms to the visions of regulatory authorities. / AFRIKAANSE OPSOMMING: Suid-Afrika se sisteem van beplanning vir sosio-ekonomiese ontwikkeling is ingewikkeld en one ektief. Daar is verskillende regulatoriese owerhede betrokke wat maklik aanleiding gee tot onsekerheid ten opsigte van verantwoordelikhede asook tot onvoldoende benaderings tot implementering. Om ontwikkeling in Suid-Afrika suksesvol te laat geskied, moet verskeie faktore inaggeneem word. Behalwe vir die strewe na ekonomiese groei, moet sosiale agterstande gelyktydig aangespreek word en moet hierdie ontwikkeling van so 'n aard wees dat die omgewing nie onnodige skade lei nie. Volhoubaarheid is 'n gemeenskaplike ideaal van die meeste partye betrokke by die beplanning van Suid-Afrika se ontwikkeling. Die implementering van hierdie oogmerk is egter onduidelik. Hierdie studie oorweeg 'n benadering wat alle handelinge in 'n bepaalde gebied in ooreenstemming bring met die visie en doelwitte van die toepaslike regulatoriese owerhede. Hierdie benadering word as 'n alternatief gestel teenoor 'n benadering om doelwitte slegs deur regulasies te bereik. Hierdie tesis het 'n Geïntegreerde Evalueringsmodel ontwikkel wat die mate waartoe 'n klein plaas 'n bydrae maak tot die visie en doelwitte van regulatoriese owerhede meet. Vier kleinskaalse boerderye in die Letaba Opvangsgebied in Limpopo was ondersoek as 'n gevallestudie. Hierdie plase is geëvalueer teen nasionale- en streeksontwikkelingsvisies. Op 'n nasionale vlak is die Nasionale Ontwikkelings Plan (NOP), die Nasionale Raamwerk vir Volhoubare Ontwikkeling (NRVO), die Geïntegreerde Volhoubare Landelike Ontwikkelings Strategie (GVLOS) en die waardes van die Water Toekenning Hervorming (WTH) beskou. Ten opsigte van streeksontwikkeling, is die betrokke munisipale Geïntegreerde Ontwikkelings Plan (GOP), die Ruimtelike Ontwikkelings Raamwerk (ROR), Plaaslike Ekonomiese Ontwikkeling (PEO) plan en die gepaste Opvangsgebied Bestuurs Plan (OBP) inaggeneem. Water is 'n beperkende faktor tot ontwikkeling in die Letaba opvangsgebied. Omrede, word die vier plase se impak op die watertoestand van die gebied bepaal, sowel as die bydrae tot die visie van die regulatoriese owerhede. 'n Opstelling van die studie-area is gemaak met die Soil and Water Assessment Tool ten einde hidrologiese a eidings te maak. Hierdeur is bepaal of die visies en doelwitte soos gestel deur die beplanningsdokumente vir ontwikkeling, realisties is ten opsigte van die waterbeskikbaarheid. Die studie het bevestig dat die ligging van 'n plaas 'n bepalende faktor is tot die plaas se uitwerking op die gebied se water. Die ontwikkelde Geïntegreerde Evalueringsmodel kombineer die visies en doelwitte van die bogenoemde strategiese dokumente om die bydrae van 'n klein plaas te meet. Die evalueringsresultate verskaf insigte rondom die ooreenstemming van plase teenoor die visie van 'n streek en kan nuttig gepas kom wanneer spesi eke aksies beplan word om 'n gemeenskaplike doelwit te bereik. Kleinskaalse boerdery is in lyn met die doelwitte soos bepaal deur die OBP, GVLOS en WTH. Die bydrae wat die plase ten opsigte van die NOP en NRVO se ideale maak is egter beperk. Verder verskil die resultate grootliks vir elke plaas ten opsigte van die bydrae gelewer tot die visies van die GOP, ROR en PEO. Gewensde resultate ten opsigte van bydrae tot ontwikkelingsvisies het nie ooreengestem met die liggings wat aanbeveel is deur die hidrologiese studie nie. Dus moet hidrologiese inligting inaggeneem word tydens besluitneming vir die ontwikkeling van kleinskaalse boerdery. Die Geïntegreerde Evalueringsmodel bied waarde, is toeganklik en is toepaslik om kleinskaalse boerdery te meet tenoor die visies van regulatoriese owerhede.

The focus of this study is to explore and expand farmer learning processes in sustainable agriculture workplace contexts. It examines change oriented learning processes in the context of three sustainable agriculture practices. The study begins by discussing the history and emergence of environmental discourses and approaches; sustainable agriculture; and the histories of three kinds of sustainable agriculture practices: Permaculture, Organic Farming and Machobane Farming System. It also traces the evolution of agricultural extension approaches within the wider context of education for sustainable development. The main focus of the study is an exploration of how farmer learning can be mediated through an expansive learning process. The study methodology surfaces some of the contradictions in sustainable agriculture and learning activity systems that farmers encounter in learning and practising sustainable agriculture. It uses these contradictions as sources of expansive learning in and between the respective activity systems of farmers, sustainable agriculture facilitators, agricultural extension workers (conventional) and organic entrepreneurs. As shown in the study, the expansive learning processes result in the modelling, implementation and reviewing of solutions to contradictions being faced in the learning and practice of sustainable agriculture. The study also proposes a number of tools that can be adapted and used by development farmers and agricultural trainers to examine and expand learning as well as build farmer agency. The study was conducted in three case study sites in Lesotho, South Africa and Zimbabwe. In Zimbabwe the study is located in Hwedza district in the St Margaret Primary School and community that learn, practise and facilitate the learning of Permaculture within the Schools and Colleges Permaculture Programme (SCOPE). The second study site is in South Africa: Durban urban and peri-urban areas where a community of organic farmers, facilitators and entrepreneurs coordinate the marketing of their produce through Isidore Farm and Earth Mother Organic and support each other to learn and practise organic farming. The third study site is based in the Mafeteng and Mohale‟s Hoek districts of Lesotho where the focus was on farmers who learn and practise the Machobane Farming System (MFS) and are supported in this by the Rural Self Development Association (RSDA) and the Machobane Agricultural Development Foundation (MADF). Drawing on three sensitising concepts of dialectics, reflexivity and agency, the study worked with Cultural Historical Activity Theory (CHAT) underpinned by critical realism to reveal how farmer learning is mediated and expanded. The theory of practice/habitus also provided a useful theoretical lens with which to examine data generated. Using a two-phased, multiple embedded case study approach, the study worked within the broad framework of social learning. It used semi-structured individual and group interviews, observations and document analysis to explore learning processes and generate „mirror‟ data. This data was then used in Change Laboratory Workshops, within the Developmental Work Research methodology, where double stimulation and focus group discussions contributed to expanding learning processes. Drawing on critical realism the study used inductive, abductive and retroductive modes of inference to analyse data in each case study as well as across case studies. The findings of the study reveal that farmer learning is influenced by both intrinsic motives, such as identity, and extrinsic motives which are primarily associated with economic, ecological and health benefits. Farmers learn through scaffolding and mediating tools that link everyday and scientific knowledge. They also learn from fellow farmers through observation, practising and experimentation. Some of the issues that were raised in connection with farmer learning processes are: language; time to learn, practice and appropriate concepts; time to improve the natural resource base while at the same time improving income generation; and responses to climate change. The study also found that farmer learning and practice of sustainable agriculture in the case studies investigated, is influenced by past and current agricultural and educational policies; societal values and attitudes; social and cultural backgrounds; work affordances and gender relations; quality of training offered; poverty; and, HIV and AIDS. In the second phase of the study, which built on the problematic situations being encountered by research participants (sustainable agriculture farmers, sustainable agriculture facilitators, extension workers, and organic marketers) to surface contradictions, the main finding was that the expansive learning process has potential to enhance farmer learning and practice of sustainable agriculture. It does this by mobilising distributed cognition among participants as well as their preparedness to act. Through the expansive learning processes in each case study, research participants were able to question their practices, surface contradictions, model solutions and implement them, and thus build individual, collective and relational agency reflexively. Observation of this required micro-analysis of agentive talk and reflective talk. The study contributes in-depth insight into participatory research and learning processes, especially within the context of people-centred learning and innovation in the agricultural development arena. It provides empirical and explanatory insight into how change oriented social learning can emerge and be expanded in Education for Sustainable Development, explaining learning and change relationships in three sustainable agricultural practices. It also provides learning and extension tools to work with contradictions that arise from intentionality, experience, context and history in farming and training activity systems. Its key contribution lies in providing in-depth insight into mobilisation of human agency and reflexivity in change oriented sustainable agriculture learning and development, processes that are critical for responding to contemporary socio-ecological issues and risks.

The Government of the Eastern Cape Province introduced the Massive Food Production programme, which is a cornerstone within the agrarian reform initiative of the Provincial Growth and Development Plan (PGDP). The programme has been going on for more than seven years, however little has been documented on its impact. The main objective of the study was to investigate the impact of the Massive Food Production Programme on the livelihoods in Nkonkobe Municipality. This study did not only investigate its impact on the participants but also assessed its impact on the recipient communities. Accordingly, the specific objectives of the study were to investigate the impact of the Massive Food Programme on the asset base of participants, the general livelihood activities, and the livelihood outcomes. Among other livelihood activities, the study made an in-depth investigation on the impact of the Massive Food Production Programme on maize crop production. This is because the Massive Food Production was aimed at maize crop production. Previous studies investigated on the indicators of success that can be used to measure the impact of this programme. After the wide-ranging evaluation of views, arguments and research findings, a model to measure impact of the programme was designed. The asset base improvement was used as the proxy of impact. Nine factors were selected from the principal component analysis of the many factors that were taken to affect participation. Three other dummy variables to proximate location, participation and group turnover were added to the regression model that was developed to measure impact. The DFID Sustainable Livelihood Framework was used to investigate the impact of the Massive Food Production Programme. This approach was used in both conceptualizing the study and the selection of variables. The DFID Sustainable Livelihood Approach was selected because unlike the CARE or UNDP Sustainable Livelihood models, it was designed for such purposes. Data collection was accomplished through observation, interviewing, and focus group discussions. The researcher also made use of project annual reports on change of livelihoods, baseline survey reports, project log frame, internal reports, work plans, budgets and mid-term evaluation reports as sources of secondary data. v The research findings were analysed using several analytical procedures, including the conventional descriptive statistics, principal components analysis, and linear regression analysis. The use of the different types of analysis was driven by the research questions under investigation and the theories on which they are based, and by the available data. The study revealed that to some extent the Massive Food Production Programme has managed to improve the asset base of the farmers. However, its impact on ensuring food security is still debatable. Findings of the study revealed that most of the participants and the non-participants communities experienced food shortages in the last season 2007/8 for at most three months. The study revealed that the highest agricultural income is from livestock sales. The varying locations showed the potential of livestock production. It is recommended that development agencies consider livestock production as an agricultural strategy with immense potential for enhancing sustaining rural livelihoods

Given the livelihoods challenges which face many rural communities, understanding a community’s livelihoods dynamics and opportunities is one major step to developing workable options to address the challenges. This study has focused on one rural community and used the five determinants of the Sustainable Livelihoods Approach to describe the livelihoods situation in Embui sub-location in Machakos County, Kenya. Residents of Embui have had to deal with the fact that traditional production systems are not sufficient to provide for their livelihoods needs. The community and continues to be challenged by limited capital for diversifying income sources, low skills and limited social and economic services. This study recommends support to marketing of locally produced artifacts, improved access to capital and provision of water for irrigation along with extension services as the key areas of support to improve the living standards of the residents of Embui / Development Studies / M.A. (Development Studies)

No description available.

Este trabalho traz como tema central a realidade da agricultura e dos agricultores familiares no Brasil. A análise dessa temática parte da identificação e caracterização do modelo de modernização tecnológica adotado no contexto brasileiro. Busca-se compreender a concepção de tecnologia e de desenvolvimento tecnológico que fundamentou determinadas opções políticas e econômicas e identificar a racionalidade que permeou tal processo, visto que todo agir social traz consigo uma racionalidade que lhe é própria. Nesse itinerário de investigação são especialmente abordados alguns conceitos como "Razão Instrumental", "Apropriação" e "Inapropriação" tecnológica e mesmo tecnologia. Posteriormente é apresentada a prática alternativa de agricultura orgânica como "apropriada tecnologicamente" ao contexto da agricultura familiar e orientada segundo os princípios de uma racionalidade comunicativa. Conceito este analisado conforme a construção filosófica de Jürgen Habermas. Em seguida se busca aproximar os conceitos até então abordados com a proposição de que as práticas associativistas e cooperativistas por agricultores familiares são essenciais para a construção de espaços onde a racionalidade comunicativa se efetiva e onde tal categoria de agricultores conquista sua cidadania. A construção desse arcabouço teórico é por fim confrontada com a realização de uma pesquisa do tipo "Estudo de Caso" de uma associação de agricultores orgânicos do município de Tijucas do Sul, por nome ARUATÃ. O objetivo é analisar e perceber as dificuldades de construção de uma prática associativista e as possíveis razões que explicariam porque muitas iniciativas associativistas não prosperam, como por exemplo, a própria ARUATÃ. / This work assumes as its central issue the reality of agriculture, and specially the familiar agriculture, in Brazil. The analysis of this thematic begins with the identification and characterization of the technological modernization model adopted in the Brazilian context. Therefore, it seeks to understand the conception of technology and technological development that based the political and economic options and to identify the rationality embedded in the process, since every social action brings a rationality of its own. In this itinerary of investigation are especially used the concepts of " instrumental reason" technological "appropriation" and "unappropriation" and even technology. The alternative practices of organic agriculture is presented as "technologically appropriated" in the context of familiar agriculture and oriented according to the principles of a communicative reason, as defined by Jürgen Habermas. Next the text tries to bring together the theoretical concepts and the proposition that associative and cooperative practices by familiar farmers are essentials for the construction of spaces where the communicative rationality really works and where the farmers can conquest their citizenship. The theoretical frame is finally confronted with a "case study" research about an association of organic farmers from Tijucas do Sul, named ARUATÃ. The objective is to analyze and realize the existent difficulties in the construction of an associative practice and the possible reasons that could explain why many associative initiatives, like Aruatã, don't prosper.

Este trabalho traz como tema central a realidade da agricultura e dos agricultores familiares no Brasil. A análise dessa temática parte da identificação e caracterização do modelo de modernização tecnológica adotado no contexto brasileiro. Busca-se compreender a concepção de tecnologia e de desenvolvimento tecnológico que fundamentou determinadas opções políticas e econômicas e identificar a racionalidade que permeou tal processo, visto que todo agir social traz consigo uma racionalidade que lhe é própria. Nesse itinerário de investigação são especialmente abordados alguns conceitos como "Razão Instrumental", "Apropriação" e "Inapropriação" tecnológica e mesmo tecnologia. Posteriormente é apresentada a prática alternativa de agricultura orgânica como "apropriada tecnologicamente" ao contexto da agricultura familiar e orientada segundo os princípios de uma racionalidade comunicativa. Conceito este analisado conforme a construção filosófica de Jürgen Habermas. Em seguida se busca aproximar os conceitos até então abordados com a proposição de que as práticas associativistas e cooperativistas por agricultores familiares são essenciais para a construção de espaços onde a racionalidade comunicativa se efetiva e onde tal categoria de agricultores conquista sua cidadania. A construção desse arcabouço teórico é por fim confrontada com a realização de uma pesquisa do tipo "Estudo de Caso" de uma associação de agricultores orgânicos do município de Tijucas do Sul, por nome ARUATÃ. O objetivo é analisar e perceber as dificuldades de construção de uma prática associativista e as possíveis razões que explicariam porque muitas iniciativas associativistas não prosperam, como por exemplo, a própria ARUATÃ. / This work assumes as its central issue the reality of agriculture, and specially the familiar agriculture, in Brazil. The analysis of this thematic begins with the identification and characterization of the technological modernization model adopted in the Brazilian context. Therefore, it seeks to understand the conception of technology and technological development that based the political and economic options and to identify the rationality embedded in the process, since every social action brings a rationality of its own. In this itinerary of investigation are especially used the concepts of " instrumental reason" technological "appropriation" and "unappropriation" and even technology. The alternative practices of organic agriculture is presented as "technologically appropriated" in the context of familiar agriculture and oriented according to the principles of a communicative reason, as defined by Jürgen Habermas. Next the text tries to bring together the theoretical concepts and the proposition that associative and cooperative practices by familiar farmers are essentials for the construction of spaces where the communicative rationality really works and where the farmers can conquest their citizenship. The theoretical frame is finally confronted with a "case study" research about an association of organic farmers from Tijucas do Sul, named ARUATÃ. The objective is to analyze and realize the existent difficulties in the construction of an associative practice and the possible reasons that could explain why many associative initiatives, like Aruatã, don't prosper.

O consumo e o mercado de cafés especiais, como orgânicos, gourmets e socialmente justos, cresce no mundo todo oferecendo preços atraentes para o produtor, enquanto o mercado de cafés commodity encontra grande oferta e preços muito baixos. A produção orgânica revela-se como alternativa ambiental, social e econômica, pois não contamina o meio ambiente e nem as pessoas direta e indiretamente envolvidas, além de agregar mais valor ao produto final. Apesar de o Brasil ser o maior produtor mundial de café, com aproximadamente 45 milhões de sacas em 2002, a produção de café orgânico foi aproximadamente de 70 mil sacas, de acordo com a ACOB (Associação de Cafeicultura Orgânica do Brasil). O México é o maior produtor mundial de café orgânico, com aproximadamente 500 mil sacas em 2002, sendo a maioria proveniente de sistemas sombreados de café. A cafeicultura nacional caracteriza-se por extensas áreas de monocultivo a pleno sol, desconsiderando o fato do café ser uma espécie originária de florestas caducifólias da Etiópia. A produção de café orgânico brasileira também é, em sua maioria, a pleno sol, com pouca biodiversidade e grande input ao sistema. Países produtores de café orgânico em sistemas sombreados e consumidores criticam a ausência de biodiversidade do sistema brasileiro. Portanto, a pesquisa nacional deve avaliar cientificamente diferentes manejos de café orgânico, obtendo informações quantitativas e qualitativas, visando a sustentabilidade sócio-ambiental e ganho de competitividade internacional do produto brasileiro neste nicho de mercado. Na busca de parâmetros que permitam a caracterização do sistema sombreado e do sistema a pleno sol de café orgânico, a composição química elementar avaliada em elevado nível metrológico é uma ferramenta potencial. Esta alta confiabilidade metrológica pode ser obtida através da análise por ativação neutrônica instrumental (INAA). Para a caracterização destes sistemas de produção de café orgânico, vários elementos químicos foram quantificados por INAA em grãos e folhas de café Coffea arabica, variedade Mundo Novo, e nos solos de ambos os sistemas - café sombreado por árvore leguminosa Platycyamus regnellii e café a pleno sol, na fazenda Jacarandá, Machado, Minas Gerais. Foram também avaliados os parâmetros de produtividade, fertilidade do solo, nutrição vegetal e qualidade do café. Os resultados indicam uma perspectiva positiva para a discriminação dos dois sistemas de produção utilizando-se da composição química elementar determinada por INAA. As avaliações demonstram uma tendência à superioridade do sistema sombreado, principalmen te quanto às maiores concentrações de potássio encontrados em grãos, folhas e solo, que podem ter propiciado uma melhor qualidade do café deste sistema. / The consumption of special coffee, mainly organic coffee, is increasing worldwide following the tendency of consuming products socially fair and ecologically sustainable, providing new market opportunities for coffee farmers in developing countries. The organic coffee is considered to have a better quality, once no agrochemicals are used and therefore, only the essential elements of the coffee will be present in the final product. Brazil is the largest world coffee producer, with 2,700,000 tons of green coffee in the 2002 harvest. However, only 4,200 tons are certified organic coffee, according to the Organic Coffee Brazilian Association (ACOB). The cultivation of organic coffee and shaded coffee are common in Central America, while in Brazil both conventional and organic coffee are mainly cultivated in the full sun system. Mexico, the largest world organic coffee producer, harvested 24,000 tons of certified organic coffee in the 2001-2002 season, most of it from shaded organic coffee system. In Brazil, such system is not well trusted and is also known as less productive. The full sun organic system is very criticized because of the lack of biodiversity and the high demand for external organic fertilizers. The shaded coffee system recycles more nutrients and has biodiversity, consequently, less dependent on external organic fertilizers, insecticides and fungicides. To characterize these two distinct organic coffee production systems, several inorganic chemical elements were quantified by instrumental neutron activation analysis (INAA) in coffee beans and leaves from Coffea arabica, variety Mundo Novo, leguminous shade tree (Platycyamus regnellii) leaves and soil from both systems at the Jacarandá farm, Machado, Minas Gerais State, Brazil. Other parameters such as productivity, soil fertility, plant nutrition and coffee quality were also evaluated. Results show a positive perspective for discrimination of the two production systems, through the chemical composition by INAA. The evaluations show a tendency of superiority for the shaded treatment, mainly according to the higher mass fractions of K in grains, leaves and soil, which may have caused better coffee quality.

No description available.

Le contrôle des ravageurs est l'un des principaux services éco-systémiques rendus par la biodiversité à l'agriculture. Les communautés d'insectes auxiliaires, hébergées par les espaces agricoles présentent des niveaux de diversité, spécifique et fonctionnelle, élevés et leurs biologie et traits de vie sont bien décrits et étudiés. Ces communautés constituent donc un excellent modèle pour aborder des questions d'intérêt à la fois fondamental et appliqué sur les mécanismes à l'origine de la biodiversité et sur l'impact de la biodiversité sur l'approvisionnement en services éco-systémiques. Dans cette thèse, nous développons une combinaison originale d'approches classiques et d'approches moléculaires de pointe pour élucider les relations trophiques au sein de la communauté de coléoptères carabiques en milieu agricole. Les coléoptères carabiques peuvent contribuer de façon significative au service de contrôle biologique mais les mécanismes généraux conditionnant cette contribution restent encore difficiles à évaluer par manque d'approche systémique pour l'analyse de leurs réseaux d'interactions.L'étude sans a priori du régime alimentaire de la communauté de carabes dans un paysage agricole typique révèle un partitionnement de la ressource entre groupes d'espèces. L'étude expérimentale des interactions entre espèces avec un régime alimentaire similaire montre une différentiation des activités spatio-temporelles à fine échelle. D'un point de vue fondamental, ces résultats semblent démontrer la prépondérance des processus déterministes (partage de niche) par rapport aux processus neutres (stochasticité environnementale) pour expliquer la coexistence des espèces. D'un point de vue appliqué, l'importance de la ressource dans la structuration des communautés de carabes fournit un levier d'action potentiel pour l'élaboration de stratégies de gestion afin d’optimiser leur fonction de régulateurs naturels. / Biological control is one of the main ecosystem services provided by biodiversity in agroecosystems. Communities of beneficial insects, hosted by agricultural areas exhibit high levels of species and functional diversity, and their biology and life history traits are well described today. These communities are therefore an excellent model for addressing issues of fundamental and applied interest about mechanisms at the origin of biodiversity and its impacts on the supply of ecosystem services. In this thesis, we develop an original combination of advanced molecular approaches and more traditional methods in order to elucidate trophic interaction network within the community of carabid beetles in agricultural areas. The carabid beetles can significantly contribute to the service of biological control, but their contribution and beneficial conditions are difficult to assess because of their opportunistic and plastic feeding behavior. A without a priori investigation of carabid diet at community level in a typical agricultural landscape reveals a resource partitioning between groups of species. Additional experimental studies in laboratory conditions indicate that interspecific competition could be the mechanism generating this partitioning. From a fundamental point of view, these results suggest a preponderance of deterministic processes (niche partitioning) compared to neutral processes (environmental stochasticity) to explain the coexistence of species. From an applied point of view, the importance of the resource in structuring carabid communities provides a potential lever of action for the development of efficient management strategies optimizing carabid function as crop auxiliaries.