{"id":15461,"date":"2026-05-26T08:20:22","date_gmt":"2026-05-26T08:20:22","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/phuong-thi-nguyen\/"},"modified":"2026-05-26T08:21:04","modified_gmt":"2026-05-26T08:21:04","slug":"phuong-thi-nguyen","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/phuong-thi-nguyen\/","title":{"rendered":"Phuong Thi Nguyen"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":7,"featured_media":15462,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-15461","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"Understanding drivers of vegetable agro-biodiversity in smallholder farming","samenvatting":"Groenten spelen meerdere rollen in kleinschalige landbouwsystemen door bij te dragen aan voedsel, voeding, veevoer, inkomen, risicobeheer en veerkracht. Rijk aan mineralen, vitamines, vezels en eiwitten, zijn groenten essentieel voor dieetdiversiteit. Ondanks hun belang heeft het huidige onderzoek naar landbouw- en zaadsystemen zich grotendeels gericht op basisgewassen zoals rijst, ma\u00efs en tarwe, met beperkte aandacht voor groenten. In dit proefschrift wordt de agro-biodiversiteit van groenten gedefinieerd als de variatie in gewassen en hun vari\u00ebteiten die door boerenhuishoudens worden geteeld voor voedsel, verkoop, voer en medicinale doeleinden.\n\nDe agro-biodiversiteit van groenten wordt gevormd door de beslissingen van boeren over welke gewassen en vari\u00ebteiten ze verbouwen en welke zaadbronnen ze gebruiken. Zaadsystemen, die traditioneel worden gecategoriseerd als informele (boeren) of formele systemen, maar in toenemende mate ook intermediaire systemen omvatten, spelen een cruciale rol bij het vormgeven van de diversiteit. Er is echter nog weinig bekend over hoe boeren zaadbronnen uit verschillende systemen combineren en hoe deze keuzes de diversiteit be\u00efnvloeden in de tijd en ruimte. Dit proefschrift onderzoekt hoe groentediversiteit wordt gestructureerd, behouden of verloren gaat via managementpraktijken, zaadsystemen en collectieve processen in Noord-Vietnam.\n\nTen eerste analyseert het onderzoek de groentediversiteit op huishoudniveau. De resultaten tonen aan dat diversiteit positief geassocieerd is met een grotere verscheidenheid aan zaadbronnen. Zelfbewaard zaad en lokale markten spelen een essenti\u00eble rol, terwijl directe betrokkenheid bij formele systemen beperkt blijft. Intermediairs bleken cruciaal voor het verbinden van boeren met formele systemen. Ten tweede werd onderzocht hoe diversiteit over ruimtelijke niveaus (van huishouden tot district) is opgebouwd. De diversiteit nam scherp toe van huishoud- naar dorpsniveau. Zeldzame groenten droegen aanzienlijk bij aan de totale diversiteit en werden vooral in stand gehouden voor eigen consumptie.\n\nHet derde en vierde deel van het proefschrift richten zich op vari\u00ebteitsdiversiteit binnen \u00e9\u00e9n soort: de pompoen. Het onderzoek naar de dynamiek van pompoenzaadkeuzes concludeert dat beslissingen van boeren geen eenmalige adoptiemomenten zijn, maar adaptieve processen gevormd door marktkansen, arbeidsbeperkingen en seizoensgebonden omstandigheden. Participatieve vari\u00ebteitsselectie met groepen vrouwelijke boeren toonde aan dat het beheer van meerdere vari\u00ebteiten vaak de capaciteit van individuele huishoudens overstijgt en gebaat is bij collectieve activiteiten.\n\nConcluderend stelt dit proefschrift dat de agro-biodiversiteit van groenten het resultaat is van op elkaar inwerkende processen over verschillende ruimtelijke niveaus, zaadsystemen en tijd. De vijf belangrijkste inzichten zijn: (1) groentediversiteit is dynamisch en schaaloverstijgend; (2) informele en intermediaire systemen zijn centraal voor het behoud van diversiteit; (3) diversiteit op gewas- en vari\u00ebteitsniveau wordt gedreven door verschillende mechanismen; (4) beslissingen van boeren zijn adaptief; en (5) ondersteuning van agro-biodiversiteit vereist langdurige betrokkenheid die de experimenteerdrift van boeren erkent en de ontwikkeling van een ge\u00efntegreerde zaadsector versterkt.","summary":"Vegetables play multiple roles in smallholder farming systems by contributing to food, nutrition, feed, income, risk management, and resilience. Rich in minerals, vitamins, fibers and proteins, vegetables are essential for dietary diversity. Despite their importance, the current body of agricultural and seed systems research has largely focused on staple crops such as rice, maize, and wheat, with limited attention to vegetables. In this thesis, vegetable agro-biodiversity is defined as the variation in crops and their varieties cultivated by farming households for food, sale, feed, and medicinal purposes.\n\nVegetable agro-biodiversity is shaped by farmers\u2019 decisions regarding which crops and varieties to be grown and which seed sources to use. Seed systems, which are traditionally categorized as informal (farmer) or formal systems but increasingly recognized to include intermediate systems as well, play a crucial role in shaping vegetable diversity. Yet, understanding remains limited on how farmers combine seed sources from different seed systems, and how these choices influence diversity across space and time. Moreover, most existing studies assess diversity at a single spatial level or treat it as static, overlooking how diversity is shaped from dynamic decision-making processes of farmers and accumulates across spatial levels. This thesis addresses these gaps by exploring how vegetable diversity is structured, maintained, or lost through farmers\u2019 management practices, seed systems, and collective processes in northern Vietnam. This region offers an inspiring context due to the predominance of smallholder farming households, agro-ecological heterogeneity over short distances, input and output market transformation over the past three decades, and cultural diversity with more than 30 ethnic groups residing in northern Vietnam. By adopting a mixed-methods approach combining household surveys, interviews, focus group discussions, and participatory experiments, this research addresses four interrelated questions.\n\nFirst, it analyzes household-level vegetable diversity and its links to seed sources and seed systems. The results show that diversity is positively associated with more diverse seed sources. Among the seed sources farmers used, self-saved seed and local markets played an essential role while the direct engagement with formal seed systems and their actors remained limited. Intermediaries were crucial in linking farmers to formal seed systems, thereby creating intermediate seed systems. Second, this thesis examined how vegetable diversity was structured and shaped across spatial levels from household to district. The results show that the diversity increased sharply from household to village level and accumulated more gradually at higher levels. Rare vegetables, which were grown by only one or two households within a village, contributed substantially to observed overall diversity and were mainly maintained through self-saved seed and produced for home consumption, reflecting heterogenous household preferences. For the third and fourth question the thesis zooms in on a single species to look at variety diversity. As third, this thesis explores temporal dynamics in farmers\u2019 choices of pumpkin seed and varieties. It concludes that farmers\u2019 decisions were not discrete adoption events, rather continuous, adaptive processes shaped by market opportunities, labor constraints, seasonal conditions, and use purposes. Farmers\u2019 choice of varieties and seed resulted from cycles of experimentation, use, and\/or abandonment, which challenged linear adoption models. Fourth, participatory variety selection with women farmer groups demonstrates that managing multiple varieties at the same time often exceeded individual household capacity and benefits from collective activities. Farmers assessed varieties based on multiple criteria, including yield, culinary quality, and market opportunity. Participatory approaches can also support the re-introduction of local varieties and thus strengthen links between gene banks and on-farm conservation. The answers to the first two research questions show that crop-level diversity is mainly associated with access to land, labor, and multiple seed sources, whereas the last two demonstrate that varietal diversity is shaped by farmers\u2019 adaptive seed management, experimentation, and changing preferences over time.\n\nOverall, this thesis shows that vegetable agro-biodiversity is not merely a remnant of tradition nor a direct outcome of market integration. It is the outcome of interacting processes across spatial level, seed systems and time. Five key insights are drawn from the research: (1) vegetable diversity is dynamic and multi-scale; (2) informal and intermediate seed systems are central to sustaining diversity; (3) crop-level and variety diversity are driven by related but distinct mechanisms; (4) farmers\u2019 decisions are adaptive and shaped by use-purpose values; (5) supporting vegetable agro-biodiversity requires long-term engagement that recognizes farmers\u2019 experimentation and strengthens an integrated seed sector development.","auteur":"Phuong Thi Nguyen","auteur_slug":"phuong-thi-nguyen","publicatiedatum":"17 juni 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/phuongthinguyen?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/262e0ce7-7f9b-43b0-84da-5535beea4483\/optimized","url_epub":"","ordernummer":"18841","isbn":"978-94-6534-382-2","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":15463,"naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15461","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=15461"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15461\/revisions"}],"predecessor-version":[{"id":15464,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15461\/revisions\/15464"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/15462"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=15461"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=15461"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}