Ecological network theory has developed from studies of static, binary trophic relationships to the analysis of quantitative, dynamic communities consisting of multiple link-types. Particularly, work has focused on the dynamic nature of ecological networks, which maintains stability in complex communities. However, there are few in situ network-level studies of the determinants of temporal and spatial variation in community structure. This thesis utilises data from a 10-year study of a host-parasitoid network and a collaborative study in an applied ecological setting to identify individual level factors important to network structure. The work aims towards an empirical, predictive framework linking adaptive foraging behaviour to ecological network structure. The results show that condition-dependent foraging behaviours structure host-parasitoid networks. The realised niches of the studied parasitoid species were generally biased towards larger host species and condition-dependent sex ratio allocation increased the likelihood that females would eclose from relatively larger hosts and males from relatively smaller hosts, which resulted in sex ratios deviating from Hamiltonian (50:50) predictions. Further, both of these aspects of behaviour are plastic, where parasitoid behaviour responded to environmental heterogeneity. Particularly, host preference behaviour conformed to an egg-/time-limitation framework, where the size dependency of the behaviour is greater when individuals have a greater likelihood of being egg-limited. Both the size-dependency and the plasticity of these behaviours differed significantly between secondary parasitoid species. This species identity effect interacted with landscape heterogeneity, which may explain some inter- and intra-specific variation in network structure. With respect to applied ecology, the results show that the benefits of natural vegetation for pest control are dependent upon the dispersal capabilities and the diet breadth of the pest and its natural enemies. The findings are evaluated towards a predictive framework for understanding the effects of future climate change on community structure and stability. We consider this framework in terms of applied ecology, particularly pest control ecosystem services provided by natural vegetation in an agricultural environment. The synergistic nature of the multiple determinants of network structure found in this thesis suggest that future studies should focus on the whole network, which is not necessarily the sum of its parts.

L'augmentation de la dégradation des sols et ses conséquences sur les services écosystémiques nécessite le développement de stratégies de restauration de ces sols. La constitution de Technosols, résultant de l’assemblage de sols pollués et de déchet industriels, est une approche innovatrice pouvant à la fois permettre de restaurer les sols et de recycler des sous-produits industriels. Des études récentes ont mis en évidence que les Technosols pouvaient assurer des services écosystémiques tels que la production primaire. Toutefois, notre connaissances des autres services écosystémiques rendus par les Technosols tels que les cycles biogéochimiques est limitée. En raison de la contribution significative des communautés microbiennes aux cycles biogéochimiques dans les sols, l’objectif de ce travail de thèse était l’effet du type de Technosol sur les communautés microbiennes et plus particulièrement les communautés fonctionnelles impliquées dans le cycle de l’azote. Dans ce contexte, (i) la densité et la diversité de la communauté bactérienne totale, (ii) la densité de la communauté crenarchéenne ainsi que (iii) la densité et les activités des communautés nitrifiante et dénitrifiante ont été étudiées dans deux types de Technosols différents. Les résultats obtenus montrent que la diversité et la composition de la communauté bactérienne des deux Technosols n'étaient pas significativement différentes entre elles, et similaires à celles de ‘sols naturels’, les Proteobacteria étant le phylum dominant (50-80%). La densité de la communauté bactérienne oxydant l’ammonium était non seulement plus importante que celle des crenarcheae qui oxyde l’ammonium, mais est également corrélée avec l'activité potentielle de nitrification suggérant ainsi que les bactéries sont responsables de l’oxydation de l’ammonium dans les Technosols. La densité des dénitrifiants et de la communauté oxydant l’ammonium sont du même ordre de grandeur que celles observées dans les sols agricoles. L’analyse de la distribution de l'activité et de la densité des communautés nitrifiante et dénitrifiante dans les différents horizons des Technosols montre un effet négatif de la profondeur, cet effet étant plus marqué que l’effet du type de Technosol étudié. Les propriétés physico-chimiques des Technosols et la densité de la communauté bactérienne oxydant l’ammonium sont corrélés à l'activité de nitrification alors que l'activité de dénitrification était contrôlée principalement par les propriétés physico-chimiques des Technosols, et dans une moindre mesure par la densité de la communauté dénitrifiant possédant le gène nirS. L'estimation de la stabilité fonctionnelle du processus de dénitrification vis-à-vis de périodes stress hydrique et thermique a montré que les Technosols présentaient une plus haute résistance et une meilleure résilience que des sols remédiés par traitement thermique uniquement. Ce travail souligne le potentiel des Technosols à assurer les services écosystémiques tels que le cycle de l’azote, ainsi que leur forte capacité à résister et à se remettre de stress environnementaux. Tout ceci semble donc indiquer que la construction de Technosols est une technologie prometteuse qui pourrait permettre la restauration de friches industrielles et le recyclage des déchets industriels / Increasing soil degradation and its consequences on overall ecosystem services urge for restoration strategies. Construction of Technosols through assemblage of treated soil and industrial wastes is an innovative technology for the restoration of polluted land and re-use of industrial by-products. Recent studies have evidenced that Technosols could support ecosystemic services such as primary production but the knowledge about other soil functions, such as biogeochemical cycling, is limited. Due to the significant contribution of microbial communities to soil functioning, this PhD work was carried out to study the effect of the type of Technosol on microbial communities with a focus on functional guilds involved in N cycling. For this purpose, the abundance and diversity of the total bacterial community and the abundance of crenarchaeal community together with the abundance and activities of the nitrifying and denitrifying communities were investigated in two types of Technosols. Results demonstrated that diversity and composition of the bacterial community were similar to ‘natural soils’ and were not significantly different between the two Technosols with Proteobacteria being the dominant phylum (50-80%). The bacterial ammonia oxidizers were greater in number than crenarchaeal ammonia oxidizers but also correlated to the potential nitrification activity suggesting that bacteria are the dominant ammonia oxidizers in Technosols. The abundance of both the ammonia oxidizers and the denitrifiers were in the same range than that observed in other soil systems. Analyses of the vertical distribution of the activity and abundance of N-cycling communities in the Technosols showed a significant depth-effect, which was more important than the Technosol type-effect. Technosols physicochemical properties and the abundance of the bacterial ammonia oxidizers were the main drivers of the nitrification activity whereas the denitrification activity was controlled mainly by the Technosols physicochemical properties and, to a minor extent, by the abundances of the nirS denitrifiers. The estimation of the functional stability of the denitrification process against the heat-drought stresses revealed that Technosol exhibited the high resistance and resilience in comparison to the thermally treated soil. This work highlighted the potential of constructed Technosols to ensure the N cycling ecosystem services, along with a high capacity to resist and recover from environmental stresses, suggesting that construction of Technosols is a promising technology and a solution for the restoration of industrial wastelands and waste recycling

A Madagascar et au Niger, des politiques de décentralisation de la gestion des ressources naturelles ont émergé dans les années 90. Elles se sont construites en réponse à l'échec des politiques centralisées face à la dégradation des forêts et ont été favorisés par le développement de la reconnaissance à l'international des capacités des acteurs ruraux à gérer leurs forêts. L'application de ces politiques modifie les interactions entre acteurs ruraux et écosystèmes de façon positive et négative. Cette thèse propose un cadre pour analyser les effets attendus et inattendus des réformes forestières sur les forêts et les acteurs ruraux. Ce cadre est appliqué à un cas d'étude à Madagascar et un au Niger, illustrant la décentralisation dans des contextes différents. Le couple humains-écosystèmes forestiers est modélisé comme un système socio-écologique (SES), dont les interactions entre usagers et écosystèmes sont des fonctions du SES. Les politiques forestières sont interprétées comme des stratégies visant à réduire la vulnérabilité des SES. Les résultats montrent que le processus de décentralisation a visé un SES dans lequel une seule fonction, la production de bois énergie, est représentée. Cependant, les systèmes de forêts tropicales sèches sont composés de plusieurs fonctions différentes qui interagissent entre elles. Les nouvelles politiques forestières entrainent l'augmentation de l'expression de certaines des fonctions parmi les 16 identifiées au Niger et les 15 identifiées à Madagascar. Mais elles ont aussi conduit au déclin d'autres fonctions, avec des conséquences pour les acteurs impliqués dans ces fonctions. Pour réduire la vulnérabilité dans les SES des forêts tropicales sèches, des politiques qui intègrent les interactions complexes caractéristiques de ces systèmes doivent être développées. / In the 1990's, policies for decentralization of natural resource management were developed in Madagascar and Niger. These policies were created in response to the failure of centralized policies to halt forest degradation, and favored by an increasing international recognition of rural people's capacity to manage their own forests. The new policies influenced how rural people interact with their forest ecosystems, a change process that had both positive and negative outcomes. This thesis proposes a framework for analyzing intended as well as inadvertent effects of the decentralization policies on forests and on local people. It further applies the framework to two case studies, one in Niger and one in Madagascar, representing the implementation of these policies in two different contexts. The framework conceptualizes human and forests as a social-ecological system (SES), in which interactions between users and ecosystems are regarded as functions of the system. The implemented policies are interpreted as strategies to reduce vulnerability of the SES. The results show that the decentralization process targeted a SES where only one function, the production of fuelwood, was perceived. In reality, however, dry tropical forest systems are composed by several different functions, and these functions interact. While the new forest policies led to an increased expression of some of the 16 functions identified in Niger (15 in Madagascar), they led to a decline in others, with the subsequent marginalization of the actors groups linked to those functions. To reduce vulnerability in tropical dry forest SES, we need to develop policy options that properly reflect and account for the complex interactions that characterize these systems.

Payments for ecosystem services (PES), or conservation incentives, are an increasingly popular approach to encouraging natural resources conservation on private lands. The goal of PES approaches is to motivate conservation by private landowners that would not otherwise take place by providing an economic incentive. To achieve this goal, incentive programs must be available to landowners who can provide the desired services; supportive policy structures must be in place; landowners must be willing to participate as sellers of ecosystem services; and the program itself must have an institutional structure that effectively regulates the production, sale, and maintenance of targeted ecosystem services. This dissertation uses a combination of case study and comparative research methods to develop new knowledge and tools for assessing each of these necessary conditions for success. The potential development of an incentive program to conserve habitat for endangered jaguars in southern Arizona and southwestern New Mexico is used as a case study to understand the attitudes of ranchers toward participation in PES programs and related policies and regulations. Results show that ranchers have strong intrinsic conservation motivations unrelated to economic incentives, coupled with significant concerns about the impacts of government regulations that could accompany participation in a PES program. Comparative research of the institutional structures of existing PES programs is carried out using the Institutional Analysis and Development framework. Focusing on water quality trading, one of the most common types of PES program, a classification system for PES program institutional arrangements is developed and the utility of the classification system for analyzing institutional diversity is demonstrated. Together, the case study and comparative research provide a means of linking empirical assessment of PES governance models with the preferences of targeted participants, increasing the likelihood of successful conservation outcomes.

The intertwined challenges of food insecurity, deforestation, and biodiversity loss remain perennial challenges in Ethiopia, despite increasing policy interventions. This thesis investigates smallholding farmers’ tree- and forest-based livelihoods and management practices, in the context of national development and conservation policies, and examines how these local management practices and policies transform the agriculture–forest mosaic landscapes of southwestern Ethiopia. The thesis is guided by a political ecology perspective, and focuses on an analytical framework of ecosystem services (ESs) and disservices (EDs). It uses a mixed research design with data from participatory field mapping, a tree ‘inventory’, interviews, focus group discussions, population censuses, and analysis of satellite images and aerial photos. The thesis presents four papers. Paper I investigates how smallholding farmers in an agriculture–forest mosaic landscape manage trees and forests in relation to a few selected ESs and EDs that they consider particularly beneficial or problematic. The farmers’ management practices were geared towards mitigating tree- and forest-related EDs such as wild mammal crop raiders, while at the same time augmenting ESs such as shaded coffee production, resulting in a restructuring of the agriculture–forest mosaic. Paper II builds further on the EDs introduced in paper I, to assess the effects of crop raids by forest-dwelling wild mammals on farmers’ livelihoods. The EDs of wild mammals and human–wildlife conflict are shown to constitute a problem that goes well beyond a narrow focus on yield loss. The paper illustrates the broader impacts of crop-raiding wild mammals on local agricultural and livelihood development (e.g. the effects on food security and children’s schooling), and how state forest and wildlife control and related conservation policy undermined farmers’ coping strategies. Paper III examines local forest-based livelihood sources and how smallholders’ access to forests is reduced by state transfer of forestland to private companies for coffee investment. This paper highlights how relatively small land areas appropriated for investment in relatively densely inhabited areas can harm the livelihoods of many farmers, and also negatively affect forest conservation. Paper IV investigates the patterns and drivers of forest cover change from 1958 to 2010. Between 1973 and 2010, 25% of the total forest was lost, and forest cover changes varied both spatially and temporally. State development and conservation policies spanning various political economies (feudal, socialist, and ‘free market-oriented’) directly or indirectly affected local ecosystem use, ecosystem management practices, and migration processes. These factors (policies, local practices, and migration) have thus together shaped the spatial patterns of forest cover change in the last 50 years. The thesis concludes that national development and conservation policies and the associated power relations and inequality have often undermined local livelihood security and forest conservation efforts. It also highlights how a conceptualization of a local ecosystem as a provider of both ESs and EDs can generate an understanding of local practices and decisions that shape development and conservation trajectories in mosaic landscapes. The thesis draws attention to the need to make development and conservation policies relevant and adaptable to local conditions as a means to promote local livelihood and food security, forest and biodiversity conservation, and ESs generated by agricultural mosaic landscapes. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: Submitted. Paper 4: Manuscript.</p>

Climate change and habitat fragmentation are altering the structure and functioning of plant communities world-wide. Understanding how, why and with what consequences are major challenges of ecology today. Trait-based approaches focus on functional rather than taxonomic identity to facilitate process-based explanation and prediction. This thesis develops new ways of operationalising traits to understand plant community responses to the environment and community effects on ecosystem functioning and services. Wetlands, distinct in nature and patchy in their distribution, serve as a natural laboratory to extend plant trait theory and as inspiration for metacommunity modelling. The first part of the thesis (Papers 1 and 2) focuses on wetland plant traits in relation to current and future environmental conditions, ecosystem functioning and ecosystem services. Paper 1 surveys the state of knowledge regarding (i) ultimate and proximate drivers of wetland plant community functional composition, trait covariation and responses of individual traits along gradients, as well as (ii) trait effects on the sets of ecosystem properties and processes that underlie the generation of three key wetland ecosystem services (regulation of water flow, water quality, and climate). Paper 2 modifies species distribution modelling to predict future changes in plant community trait distributions due to climate change in central Sweden, which allows a qualitative estimate of changes in ecosystem service potential. Climate change induced functional changes may benefit water quality and flow regulation provided by fens and riparian wetlands, but compromise carbon sequestration capacity in bogs. The second part of the thesis (Papers 3 and 4) develops trait-based metacommunity models to study the interplay of local and regional dynamics on species, community and whole-metacommunity responses to climate change. Paper 3 finds model assumptions about species dispersal capacity to strongly influence predictions of diversity loss following climate change. While differences in species dispersal capacity drastically increase predicted extinction risk, more realistic models based on an empirically derived seed mass – seed number trade-off strongly moderate these predictions. Without considering fitness effects of covarying traits, models that include variable dispersal capacities thus might overestimate extinction risk from climate change. Paper 4 studies the development and recovery of the regional average trait-lag of response trait distributions, as a direct measure of the instantaneous realised metacommunity response to temperature change with implications for levels of ecosystem functioning. The dynamical response jointly depended on local response capacity and regional adaptive re-organisation via species range shifts. Where habitat was scarce, connectivity network properties mediated response capacity and may guide conservation priorities. This thesis makes contributions to plant trait ecology, wetland functional ecology, ecosystem service science and metacommunity theory. As a whole it furthers progress towards a predictive ecology that can bridge scales from individual physiology to ecosystem dynamics and anticipate global change effects on biodiversity and ecosystem functioning. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p><p> </p>

The marine ecosystems are fundamental for human welfare. A number of current environmental pressures need attention, and the formulation of management strategies requires information from a variety of analytical dimensions. The linkage between environmental change and resulting implications for human welfare is one such dimension. This thesis presents studies on welfare implications from hypothetical future policies which improve the state of the marine environment. The method for these studies is economic valuation. The studied scenarios concern eutrophication in the Baltic Sea (including the Kattegat) and oil spill risk from shipping in the Lofoten-Vesterålen area in the Arctic Barents Sea. The thesis shows that the economic benefits from undertaking policies to improve or protect the marine environment in these cases are substantial and exceed the costs of taking measures. In addition to providing new monetary estimates, the thesis also provides new insights concerning 1) what type of scenario to use when valuing an environmental improvement and 2) whether there may exist trade-offs between precision in estimates and the level of ambition with respect to survey instrument complexity and econometric models when conducting valuation studies. The findings suggest an end of an era for studies in which the environmental change is unspecified or based on a single environmental indicator while the actual consequences of the suggested measures are more multifaceted. In contrast, relevant scenarios to study are well-specified and holistic. The thesis further reveals that it might not always be worth the effort to go for the most advanced scenario presentation or statistically best-fitting model specifications. This is something that needs to be further discussed among practitioners in order to allocate valuation resources wisely and not waste resources on unnecessarily elegant valuation studies. / <p>QC 20161011</p>

Les prairies permanentes peuvent fournir une grande diversité de services écosystémiques. Elles se trouvent dans des conditions contrastées en termes de gestion et de climat en Europe. Cette diversité de conditions induit une grande variété de types de prairies différant par leur végétation et leur fourniture en services écosystémiques. Certains travaux suggèrent que le fonctionnement des écosystèmes prairiaux peut être directement relié à des critères de diversité fonctionnelle végétale. Ces critères, qui pourraient être utilisés pour évaluer les services écosystémiques, sont influencés par la gestion et le climat. L'objectif de ce doctorat est d'évaluer les effets de la gestion et du climat sur la diversité fonctionnelle végétale liée à des services écosystémiques des prairies permanentes. La première étape a consisté à sélectionner 29 critères de diversité fonctionnelles liés à 8 services écosystémiques (quantité de fourrage, qualité du fourrage, stabilité de la production de fourrage, conservation de la biodiversité, pollinisation, la séquestration du carbone, résistance à la sécheresse et fertilité azotée). Cette sélection a été faite à partir d'interviews d'experts et d'une revue de la littérature. La deuxième étape a consisté à évaluer différentes inexactitudes dans le calcul des 29 critères de diversité fonctionnelle à partir de bases de traits fonctionnels et différents jeux de relevés botaniques. La troisième étape a consisté à évaluer les critères de diversité fonctionnelle à partir des données de gestion et de climat, en utilisant notamment la technique mathématique des forêts de Breiman. Les résultats montrent que les variables climatiques ont généralement plus d'effet sur la diversité fonctionnelle que celles de gestion. En outre, pour certaines conditions climatiques, la gestion n'affecte pas certains critères de diversité fonctionnelle. Parmi les 29 critères de diversité fonctionnelle, seulement 8 critères avaient plus de 40% de leur variance expliquée par la gestion et le climat / Permanent grasslands can provide a large diversity of ecosystem services. They are found in contrasted conditions in terms of management and climate in Europe. These conditions induce a wide variety of grassland types that differ in their vegetation and are expected to differ with respect to the provision of ecosystem services. Because ecosystem functioning in grassland has been shown to be linked to plant functional diversity criteria, we put forward that these functional diversity criteria can be used to evaluate the provision of ecosystem services. These criteria are influenced by the management and the climate. The overall objective of this PhD program is to assess the effects of management and climate on the plant functional diversity related to ecosystem services of permanent grasslands. The first step of the PhD program was to select 29 functional diversity criteria related to 8 ecosystem services (quantity of forage, forage quality, stability of the forage production, biodiversity conservation, pollination carbon sequestration, dryness resistance and nitrogen fertility). This selection was made using experts' interview and literature survey. The second step was to evaluate inaccuracies in the calculation of the 29 functional diversity criteria from functional trait databases and different sets of botanical surveys. The third step was to estimate the functional diversity criteria from management and climate data using "Random Forests" methodology. The results show that the climatic variables had generally more effect on the functional diversity than the management ones. Furthermore, for some climatic conditions, the management does not affect some functional diversity criteria. Among the 29 functional diversity criteria, only 8 have more than 40 % of their variance explained by the management and climate variables

The ecosystem services approach has increased throughout the years, becoming a powerful tool for environmental planning as well as guideline for resources management and decision-making. Changes in land use/cover are the main human-driven impact over natural ecosystems, which implies directly in ecosystem services provisioning capacity and the ability to sustain those benefits. Water resources are strongly related to human well-being and survival, as one of the most valuable benefits humans acquire from nature. In this regard, landscapes suffering from extreme or vast changes in land use/cover represent threats over water resources, as is the case for Brazilian Cerrado savannas. The prediction of impacts of land cover exchanges over water-related ecosystem services may become one way to avoid its loss, diminishing uncertainties in decision making of land uses. In this sense, our work aimed the measurement and recognition of thresholds that indicates changes in the availability of seven essential water-related ecosystem services, within Cerrado landscapes of São Paulo State, that are facing the conversion of native forests into eucalyptus plantations. We analyzed water resources at 11 low order catchments which comprised a gradient of forested savanna and eucalyptus plantations. Stream water quality data were obtained for 13 physical-chemical-biological parameters, previously known as indicators for seven water-related ecosystem services. Results highlight the importance of monitoring Turbidity, pH, electric conductivity as indicators of services provision. Best potential gains of the seven services occurred above 45% of natural forest coverage. Landscapes with less than 20% of forest tend to become too unsustainable / A abordagem dos serviços ecossistêmicos aumentou ao longo dos anos, tornando-se uma ferramenta poderosa para o planejamento ambiental, guiando a tomada de decisão sobre o manejo de recursos naturais. Mudanças no uso/cobertura da terra são os principais impactos sobre os ecossistemas naturais, o que implica diretamente na provisão de serviços, e na capacidade do ambiente de sustentar esses benefícios. A água fornece diversos serviços ecossistêmicos hídricos, vitais para a sobrevivência humana. Então, neste contexto, paisagens submetidas a vastas mudanças de uso e cobertura representam uma séria ameaça aos serviços hídricos, como é o caso das áreas em domínio de Cerrado brasileiro. Prever e valorar as conseqüências da conversão de áreas naturais para usos da terra sobre os serviços hídricos pode se tornar uma forma de evitar sua perda e diminuir as incertezas nos processos de tomada de decisão territorial. Com esse propósito, objetivamos mensurar e definir limiares em relação às mudanças na disponibilidade de sete serviços essenciais de água em paisagens savânicas do Estado de São Paulo que sofreram conversão de florestas nativas para reflorestamentos. Analisamos recursos hídricos de onze bacias hidrográficas de pequena ordem, que compreendem composições de sistemas florestados em contato com florestas plantadas de eucalipto. As amostras de água foram avaliadas por meio de treze parâmetros físico-químico-biológicos, presumidos como indicadores de sete serviços hídricos. Os resultados ressaltaram a importância de Turbidez, pH e condutividade elétrica como elementos indicadores da provisão dos serviços. Os melhores ganhos potenciais na provisão ocorreram a partir de 45% de cobertura florestal. Paisagens com menos do que 20% de florestas naturais tendem a tornarem-se menos sustentáveis para a provisão de todos os serviços somados

As populações de insetos e os serviços ecossistêmicos realizados por esses organismos estão ameaçados por ações antrópicas, devido à conversão de habitats naturais em paisagens agriculturáveis extensa e/ou urbanizadas. Essas modificações geradas nas paisagens naturais criaram novos cenários e aumentou os desafios de investigar como o arranjo espacial do uso do solo pode afetar os processos ecológicos. Apesar do aumento do número de estudos com esse foco, ainda são escassas as avaliações na região tropical que analisam os efeitos das mudanças da paisagem sobre os polinizadores e a seus serviços. Assim, a fim de prover mais dados que possam contribuir para o entendimento das questões acima, este estudo foi estruturado em três capítulos com os seguintes objetivos: (1) investigar o papel das abelhas na produção de sementes e qualidade do óleo do girassol; (2) avaliar os efeitos de diferentes proporções da heterogeneidade espacial e de cobertura florestal na comunidade de insetos que visitam o girassol, e; (3) avaliar a provisão do serviço de polinização nessa cultura. Para isso, o primeiro capítulo foi realizado na Escola Superior de Agricultura \"Luiz de Queiroz\" - ESALQ/USP, Piracicaba, e os experimentos dos capítulos subsequentes foram conduzidos em 12 paisagens com gradiente de heterogeneidade espacial e cobertura florestal de Mata Atlântica, no Corredor Cantareira-Mantiqueira, Estado de São Paulo, Brasil. Este estudo mostrou a visitação de abelhas em girassóis híbridos aumentou o peso dos aquênios em 91%, os níveis de vitamina E em 45% e os ácidos graxos insaturados em 0,3%, quando comparados a flores isoladas desses polinizadores. Além disso, estimou-se que, devido aos serviços de polinização fornecidos pelas abelhas, o produtor praticamente duplica o valor de venda dos aquênios por hectare de área cultivada. Em relação aos experimentos conduzidos nas 12 paisagens da Mata Atlântica, foram amostrados 2.181 indivíduos de 130 espécies de insetos, pertencentes a 40 famílias de seis ordens. As abelhas foram os visitantes florais mais abundantes (77,2%) e com maior riqueza (36,9%) dentre os visitantes florais. Apis mellifera dominou a comunidade de insetos visitantes, seguida por Trigona spinipes. Essas espécies são consideradas \"super-generalistas\" quanto às suas preferências florais e importantes polinizadores em áreas degradadas, já que suas populações se mantêm em paisagens mais simplificadas e desfavoráveis a outros polinizadores. Isso pode explicar a relação negativa entre a proporção de floresta e a riqueza de insetos que visitaram os girassóis. A heterogeneidade espacial não teve efeito significativo nos índices de diversidade. No entanto, é necessário cuidado ao interpretar esses dados e levar em consideração a qualidade dos habitats naturais da paisagem circundantes aos girassóis e os traços comportamentais e ecológicos de cada espécie amostrada. Neste estudo, ficou evidente que, apesar de A. mellifera contribuir para o incremento da produtividade do girassol, o serviço de polinização realizado por outros insetos foi mais eficiente e efetivo, uma vez que influenciou positivamente no aumento do número e peso dos aquênios por capítulo, na quantidade de óleo extraído das sementes e no nível de gama- tocoferol contido no óleo. Além disso, houve também a diminuição no teor de ácidos graxos saturados. Como seu consumo aumenta a concentração de colesterol no sangue humano, a melhora da composição nutricional do óleo de girassol foi auxiliada pela ação de polinizadores. Assim, este estudo destacou o importante papel dos polinizadores para a segurança alimentar humana e a relação entre características da paisagem e o serviço de polinização, fornecendo dados básicos úteis para estratégias políticas que podem auxiliar na proteção dos polinizadores. / Insect populations and ecosystem services performed by these organisms are threatened by anthropogenic actions, such as the conversion of natural habitats into extensive agricultural and/or urbanized areas. These changes in natural landscapes have created new scenarios and increased the challenges of investigating the effect of spatial arrangement of land use in ecological processes. Despite the increasing number of studies focusing on this topic, evaluations in tropical region that analyze the effects of landscape changes on pollinators and their provision of pollination services are still scarce. Thus, in order to provide more data that address the aforementioned issues, this study was structured into three chapters, with the following aims: (1) to investigate the role of bees in seed production and sunflower oil quality; (2) to evaluate the effects of spatial heterogeneity and forest cover on sunflower-visiting insect community, and; (3) to evaluate the provision of pollination service in sunflowers. To achieve these goals, the experiments were carried out at the \"Luiz de Queiroz\" College of Agriculture - ESALQ/USP, Piracicaba, and in 12 landscapes across gradients of spatial heterogeneity and Atlantic Rainforest cover, in the Cantareira-Mantiqueira Corridor region, São Paulo State, Brazil. This study showed that bee visitation in hybrid sunflowers increased the achenes weight by 91%, the levels of vitamin E by 45% and unsaturated fatty acids by 0.3%. Furthermore, it was estimated that due to the pollination services provided by the bees, the grower of the sunflower hybrid used in this study doubles the sales value of achenes per hectare of cultivated area. In relation to the experiments conducted in the 12 Atlantic Rainforest landscapes, 2,181 individuals belonging to 130 insect species of 40 families (six orders) were sampled. Bees were the most abundant (77.2%) and the richest (36.9%) sunflower visitors. Apis mellifera dominated sunflower-visitor communities, followed by Trigona spinipes. These species are traditionally considered \"super generalists\" in relation to their floral preferences and important pollinators in degraded areas, since their populations remain in simplified landscapes that are unsuitable to other pollinators. It could explain the negative relationship between the forest proportion and the richness of sunflower-visiting insect community. Spatial heterogeneity had no significant effect on the diversity indexes. However, it is necessary to interpret these data with caution and to take in account the quality of the natural habitats surrounding the sunflowers and the behavioral and ecological traits of each insect species. Although A. mellifera contributed to increase sunflower productivity, the pollination services performed by other insect taxa were more efficient and effective, as they contributed to increase the number and weight of achenes per sunflower head, the quantity of oil extracted from seeds and the gamma-tocopherol oil concentration. In addition, there was a decrease in levels of saturated fatty acids. Since their consumption increases the concentration of cholesterol in human blood, the pollinators had an important role in the improvement of the nutritional composition of sunflower oil. Thus, this study highlighted the important role of pollinators for human food security and the relationship between surrounding landscapes and pollination service, providing useful baseline figures to policy strategies that can help to safeguard pollinators.