Classification of relevé data aims to present the best possible explanation of the vegetation within a specific study area. The variety of multivariate techniques available to classify vegetation into ecological communities has developed in recent years, which contributes to uncertainty among vegetation scientists as to which methods and computer software to select for optimum classification results. The wide application of the classical TWINSPAN algorithm along with the Braun-Blanquet approach of plant community descriptions and diagnostic species identification in southern Africa prompted a comparison of classification results between these classical approaches and a modern approach. The modern approach, as being referred to in this study, entails the recent improvement on the classical TWINSPAN algorithm, namely the Modified TWINSPAN algorithm in combination with statistical measures of species fidelity. Comparisons between classification end-results were undertaken at various spatial scales to test whether discrepancies between results obtained from the different approaches are similar when applied to a broad-scale synthesis, an intermediate synthesis and a local-scale classification within a similar vegetation type, the Mopaneveld. Such a comparative study is envisaged to present insight on the credibility of the use of classical approaches in phytosociology at various spatial scales. A modern approach was tested upon three previous vegetation classification studies which followed the classical approach. These vegetation classification studies were all undertaken at different spatial scales and are being referred to as the reference classifications. The data that were subjected to the modern approach were analogous to those used in the reference classifications. The computer package JUICE 7.0 was used in which the Modified TWINSPAN algorithm was applied in combination with statistical measures of species fidelity, which was obtained as a function directly in the JUICE program. Classification hierarchies were constructed for both the classical and modern approach results to compare and describe similarities and discrepancies between the different hierarchical dendrograms. Fidelity syntables were constructed to assist in the grouping of diagnostic species according to highest fidelity values. Such diagnostic species groups were compared with the lists of diagnostic species in the reference classifications. At the broadest spatial scale, comparisons revealed discrepancies between classification results from the classical and the modern approach. The modern approach presented a more robust synthesis of the Mopaneveld in southern Africa since the vegetation units and their associated diagnostic species are ecologically better expressed. The intermediate scale synthesis comparison revealed similar discrepancies, which again question the credibility of the classical approach at broader spatial scales. The application of the modern approach to the local scale classification, however, revealed little difference with the results obtained through the classical approach. Although more alternative classification techniques need to be applied to report on the most robust technique for vegetation classifications across spatial scales, it could be reported that the classical TWINSPAN algorithm is not favorable for vegetation classifications and syntheses beyond the local scale. The ecological reliability of the modern approach at the intermediate scale prompted its application in a synthesis of the riparian vegetation within the Mopane Bioregion of South Africa, which was not achieved in any previous study. Riparian vegetation plays an important role in maintaining good water quality and also provides habitat for many species. Riparian vegetation therefore needs to be classified and described. The synthesis of the riparian vegetation in the Mopane Bioregion of South Africa revealed six distinct plant communities which are described and discussed in terms of diagnostic, constant and dominant species along with variance in plant species diversity. / Thesis (Ph.D. (Botany))--North-West University, Potchefstroom Campus, 2012

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Low-order forested streams are dependent on allochthonous material input and the main energy source is obtained from leaf litter provided by the surrounding vegetation. Several gaps need to be filled to the knowledge of this process in subtropical environments and, accordingly, the thesis aimed to conduct some investigations considering the decomposition of leaf litter in streams. Four studies were conducted in subtropical streams with the following objectives: a) to verify the quantitative importance of the leaf input into streams, the main sources of input and its variation over the year; b) to analyze the influence of the leaf litter quality on decomposition and macroinvertebrate colonization; c) to evaluate the influence of the land use on the decomposition process, including the macroinvertebrate community and fungi; d) to conduct an initial investigation about the influence of insecticide application on the macroinvertebrate community that colonizes leaves in streams. Leaf litter was the main plant component to come in stream and the main route of entry allochthonous material was vertical. We observed the influence of season on this entry, with an increase mainly in the autumn and in the months with high rainfall. The chemical characteristic of leaves influenced the decomposition of leaf litter and its colonization by the macroinvertebrate community. Leaves with higher nitrogen content and lower amount of components that hinder decomposition were processed more quickly and, for these reasons, showed a higher amount of shredders. Moreover, different land uses did not significantly influence the decomposition process, just modifying some aspects of the macroinvertebrate community, especially in streams with urban influence. The results may be due to high currents found in local streams that make homogeneous its consequences for water quality, for the biological component and hence for ecological processes such as decomposition. We observed an influence of insecticide application on the macroinvertebrate community, decreasing the abundance of the target groups of the product, but generating an increase in the richness and abundance of other groups after an initial period of colonization. / Os riachos florestados de baixa ordem são dependentes da entrada de material alóctone e a principal fonte de energia é obtida de detritos foliares provenientes da vegetação de entorno. Várias lacunas precisam ser preenchidas para o conhecimento desse processo em ambientes subtropicais e, nesse sentido, esta tese teve como objetivo realizar algumas investigações considerando o processamento de detritos foliares em riachos. Foram conduzidos quatro estudos em riachos subtropicais com os seguintes objetivos: a) verificar a importância quantitativa da entrada foliar em riachos, as principais vias de entrada e sua variação ao longo do ano; b) analisar a influência da qualidade do detrito foliar sobre a decomposição e colonização por macroinvertebrados; c) avaliar a influência do uso e ocupação da terra sobre o processo de decomposição, incluindo a comunidade de macroinvertebrados e fungos; d) realizar uma investigação inicial acerca da influência da aplicação de inseticida sobre a comunidade de macroinvertebrados que coloniza folhas em riachos. Detritos foliares foram o principal componente vegetal a entrar no riacho e a principal via de entrada do material alóctone foi a lateral. Foi observada influência da época do ano sobre esta entrada, com aumento principalmente nos meses do outono e com alta pluviosidade. A característica química das folhas influenciou a decomposição de detritos foliares e sua colonização pela comunidade de macroinvertebrados. Folhas com maior teor de nitrogênio e menor quantidade de componentes que dificultam a decomposição foram processadas mais rapidamente e apresentaram maior quantidade de fragmentadores. Por outro lado, diferentes usos da terra não influenciaram significativamente o processo de decomposição, apenas modificando alguns aspectos da comunidade de macroinvertebrados, principalmente em riachos com influência urbana. Os resultados podem ter ocorrido devido às altas correntezas encontradas nos riachos da região, que tornam homogêneas suas consequências para a qualidade da água, para o componente biológico e, consequentemente, para os processos ecológicos como a decomposição. Foi observada uma influência da aplicação de inseticida sobre a comunidade de macroinvertebrados, diminuindo a abundância dos grupos-alvo do produto, mas gerando um aumento na riqueza e abundância dos demais grupos após um período inicial de colonização.

Au cours du XXe siècle, les lits de nombreuses rivières ont été sujets à l'installation de végétation alluviale. Dans le cas des rivières aménagées, cette tendance est souvent associée à des altérations géomorphologiques directes (extractions de granulats, endiguements, etc.) ainsi qu'à des modifications anthropiques de leur régime hydrologique et sédimentaire conduisant à une stabilisation du lit qui permet l'installation de la végétation. Cette végétation augmente le risque d'inondation en diminuant les vitesses d'écoulement et en augmentant les niveaux d'eau en crue. Par ailleurs la biodiversité est dégradée par la diminution des habitats pionniers caractéristiques de ces environnements. Manipuler artificiellement le régime hydrologique d'une manière qui pourrait limiter l'installation de végétation sur les bancs est une option considérée par les gestionnaires. Dans ce contexte, ce projet de thèse a pour objectif de comprendre les impacts des crues d'amplitude variable sur la destruction de végétation, et d'identifier les mécanismes associés. Le site d'étude sur lequel cette thèse se focalise est l'Isère en Combe de Savoie, une rivière à galets très aménagée des Alpes françaises.Dans le cadre de cette étude, la destruction de végétation a été étudiée à l'échelle du tronçon à partir d'une analyse des données hydrologiques, des photos aériennes, et des données topographiques disponibles pour la période 1996-2015. À l'échelle du banc, un suivi de terrain avant et après les événements hydrologiques marquants entre avril 2014 et septembre 2015 nous a permis d'étudier l'action des crues sur la mobilité sédimentaire et sur la végétation. Ces observations ont été complétées par une modélisation numérique bidimensionnelle de l'écoulement en crue.À l'échelle du tronçon (20 km), nous avons trouvé une corrélation très forte entre les volumes d'eau ayant transité dans le chenal sur une période donnée, et la destruction de végétation associée au cours de la période 1996-2015. Les débits associés à des temps de retour infra-annuels semblent permettre la destruction de végétation. Le mécanisme de destruction le plus efficace que l'on observe à cette échelle est l'érosion latérale ; les mécanismes prenant place à la surface des bancs sont très minoritaires. Cependant, les surfaces détruites sont modestes ; 3,4 % de la surface végétalisée est détruite annuellement en moyenne. À l'échelle du banc, la période de suivi de terrain a couvert une série de crues fréquentes (temps de retour < 1 an) et une crue de temps de retour 10 ans. Seule cette crue a partiellement détruit la végétation pionnière sur les bancs suivis. La destruction de végétation ligneuse jeune a eu lieu par le biais de quatre mécanismes : 1) déracinement par érosion de surface supérieure à 20 cm, 2) enfouissement sous une couche de sédiment grossiers supérieure à 30 cm, 3) déracinement par une combinaison d'érosion et de dépôt, et 4) érosion latérale en marge des bancs. La destruction de végétation est toujours associée à une mobilité sédimentaire importante.Ces résultats montrent qu'une crue très importante est nécessaire pour détruire la végétation par la mobilisation de la surface des bancs sur ce site. Par contraste, les débits forts mais non exceptionnels (temps de retour infra-annuel) sont en mesure de détruire la végétation par érosion latérale. Dans le cas de l'Isère en Combe de Savoie, il semble que l'utilisation de crues artificielles ne peut pas seule permettre de maintenir la largeur inter-digues libre de végétation. Pour la suite, on propose de s'intéresser à la destruction de végétation dans le contexte de la dynamique des bancs alternés plus ou moins végétalisés, en prenant en compte les apports et le transport des sédiments en plus de l'hydrologie. / Many rivers worldwide have seen vegetation establish within their beds throughout the 20th century. In the case of managed rivers, this trend is usually linked to direct geomorphological alterations (sediment mining, diking, etc.) as well as anthropic alterations of flow regime and sediment supply. These pressures have stabilized river beds, allowing vegetation to establish permanently. This vegetation increases the risk of flooding by decreasing flow velocities and increasing water levels. In addition, the associated reduction in availability of pioneer habitats characteristic of these stabilized environments typically degrades biodiversity. Managing hydrology in a way that would limit vegetation establishment on bars presents an interesting management option. In this context, our study was aimed at understanding the impacts of floods of varying magnitude on vegetation removal, as well as identifying and quantifying the underlying mechanisms. This work focused on the Isère River, a heavily managed gravel bed river located in the western French Alps.Vegetation removal was studied at the reach scale using hydrological data, aerial photographs, and topographic data available between 1996 and 2015. At the bar scale, field monitoring before and after floods from april 2014 to september 2015 allowed us to document the impact of floods on sediment mobility and vegetation. A 2D numerical model was used to document fine scale hydraulics.At the reach scale, we found a strong correlation between water volume flowing through the river channel and the amount of vegetation removal. Discharges with return intervals of less than one year seem to have an impact on vegetation removal. The main mechanism observed from aerial photographs was lateral erosion; surface processes were negligible in comparison. However, global vegetation removal was modest: since 1996, on average 3,4 % of vegetated area was removed annually. At the bar scale, our study period permitted monitoring of a series of high frequency floods (return interval < 1 year) and a 10-year food event. Only the largest flood partially removed pioneer vegetation from bars. Young vegetation removal occurred through four different mechanisms: 1) uprooting by surface scour > 20 cm, 2) burial under a thick layer of coarse sediments > 30 cm, 3) uprooting by a combination of surface scour and sediment deposition resulting in no net topographic change, and 4) lateral erosion of bars. Vegetation removal was always associated with significant sediment mobility.We conclude that on the Isere River a very important flood is required to remove vegetation by mobilizing bar surfaces. In contrast, high but not exceptional flows (return interval < 1 an) are capable of removing vegetation through lateral erosion. However, artificial floods alone are unlikely to maintain the full width of the channelized bed of the Isere River free of vegetation. In the future, vegetation removal needs to be studied in the context of alternate bar dynamics with or without vegetation. It seems necessary to consider sediment transport as well as hydrology to understand the overall dynamics of the bed.

My thesis deals with the collecting of basic information and data on riparian vegetation in surroundings of the minor watecourse Rosička through field research and subsequent inventory. In the theoretical part, I outlined the theme of watercourses and their modifications, revitalization and solutions. I also focused on vegetation accompaniment of the flows and their typology. I described the riparian and associated vegetation in detail, focused on their functions and establishment and on taking care of them. The final section of the thesis includes data of my field research. Here can be found the current condition of the species structure and the state of health of the riparian vegetation.

Made available in DSpace on 2016-06-02T19:31:37Z (GMT). No. of bitstreams: 1 DissJPNR.pdf: 3002286 bytes, checksum: 62a2e2cd9b25b8284d5df444cfa8fb99 (MD5) Previous issue date: 2007-02-26 / Universidade Federal de Sao Carlos / Both the biotic and abiotic characteristics of a habitat determine which species can live in this habitat. The frontier of two different habitats creates a transition zone, called ecotone. The transition of the Atlantica Forest and the Restinga is normally related to the presence of salt. The salt is a border line for vegetation. In costal habitats, the salt spray increases the salt in the soil, besides having a direct effect on the vegetations tissues. Riparian vegetation on the other hand, has its characteristics linked with the characteristics of the adjacent water bodies. We worked in an estuary in Caraguatatuba, São Paulo, where the Atlantic and Restinga Forests co-occurs in its margins. Our objective was to determine how the salt spray and the estuary water influence the composition of the vegetation of the arboreal component of its margins. Our results show abiotic and floristical composition differences between three different ambients. The characteristics of the estuary water and soil have little influence and the salt spray has great influence on the separation of these ambients, but the salt spray did. / As características bióticas e abióticas de um ambiente determinam quais espécies que vão ocupá-lo. O encontro de ambientes diferentes gera uma zona de transição, chamada ecótono. A transição de Mata Atlântica e restinga estão em geral relacionadas com alterações na salinidade. O sal é um fator limitante para a vegetação. Em ambientes costeiros, o spray marinho é um dos meios pelo qual o sal atinge as plantas. Vegetações ripárias, por outro lado, têm suas características ligadas aos corpos d água que as cercam. Trabalhamos em um estuário em Caraguatatuba, São Paulo, onde Restinga e Mata Atlântica e se encontram nas suas margens. Nosso objetivo foi determinar de que forma o spray marinho e as características da água do estuário influenciam a composição arbórea da sua margem. Os resultados indicam que existem diferenças na composição florística que nos permitem dividir a margem do rio em três diferentes ambientes. As características da água e do solo do estuário têm pouca influência sobre essa divisão, ao contrário do spray marinho, que tem grande influência sobre ela.

Submitted by Luciana Sebin (lusebin@ufscar.br) on 2016-10-07T13:06:43Z No. of bitstreams: 1 TeseLALR.pdf: 3856057 bytes, checksum: 10fbc03e49473d6963719567da88bceb (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-13T20:05:24Z (GMT) No. of bitstreams: 1 TeseLALR.pdf: 3856057 bytes, checksum: 10fbc03e49473d6963719567da88bceb (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-13T20:05:40Z (GMT) No. of bitstreams: 1 TeseLALR.pdf: 3856057 bytes, checksum: 10fbc03e49473d6963719567da88bceb (MD5) / Made available in DSpace on 2016-10-13T20:05:57Z (GMT). No. of bitstreams: 1 TeseLALR.pdf: 3856057 bytes, checksum: 10fbc03e49473d6963719567da88bceb (MD5) Previous issue date: 2016-03-04 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / With the purpose of elucidating some aspects concerning the influence of leaf chemical composition on Chironomidae (Diptera) larvae colonization and their role in decomposition, field experiments were carried out here presented in four chapters: i) Chemical and elemental composition of leaf litter of Hedychium coronarium, Pteridium arachnoideum and Magnolia ovata during decomposition in a low-order stream; ii) Influence of leaf chemical composition in the colonization of Hedychicium coronarium, Pteridium arachnoideum and Magnolia ovata leaf litters by Chironomidae (Diptera) larvae; iii) Feeding habits of the Chironomidae (Diptera) larvae and their contribution to the consumption of plant tissues during decomposition in low order streams; iv) Influence of Chironomidae (Diptera) larvae in the kinetics of aerobic decomposition of Hedychium coronarium, Pteridium arachnoideum and Magnolia ovata leaf litters. The experiments were performed in low order streams in São Carlos-SP and consisted on incubation of polyethylene bottles with small holes containing dried leaves of the three plant species, being removed from time to time over 85 days. Overall, the results indicated that: i) the invader leaf litter showed major quantities of refractory and allelopathic materials than native one; ii) differences in the leaf litter chemical composition influenced the Chironomidae larvae colonization; iii) the chironomids feeding habits differed among plant species and vary with the time of incubation of the leaf litter, amount of remaining mass and adhered organic matter; iv) Chironomidae larvae, mainly shredders, that colonize leaf litters can influence mass loss. / Buscando esclarecimentos sobre a influência da composição química foliar na colonização por larvas de Chironomidae (Diptera) e seu papel na decomposição foram realizados experimentos aqui apresentados em 4 capítulos: i) Composição química de detritos foliares de H. coronarium, P. arachnoideum e M. ovata durante a decomposição em um córrego de baixa ordem; ii) Influência da composição química foliar na colonização de detritos de H. coronarium, P. arachnoideum e M. ovata por larvas de Chironomidae (Diptera); iii) Hábitos alimentares das larvas de Chironomidae (Diptera) e sua contribuição para o consumo de tecidos vegetais durante a decomposição de detritos em riachos de baixa ordem; iv) Influência das larvas de Chironomidae (Diptera) na cinética da decomposição aeróbia de detritos foliares de H. coronarium, P. arachnoideum e M. ovata. Os experimentos foram realizados em riachos tropicais de baixa ordem e consistiram na incubação de frascos de polietileno com pequenos furos contendo folhas desidratadas das três espécies vegetais, sendo retirados parceladamente ao longo de 85 dias. De maneira geral, os resultados indicaram que: i) as plantas invasoras apresentaram maior teor de materiais refratários e alelopáticos do que a nativa; ii) as diferenças na composição química dos detritos influenciaram na colonização pelas larvas de Chironomidae; iii) os hábitos alimentares de quironomídeos diferiram entre as espécies vegetais e variaram com o tempo de incubação dos detritos, quantidade de massa remanescente e matéria orgânica aderida; iv) as larvas de Chironomidae, em especial os fragmentadores, que colonizam os detritos foliares podem influenciar na perda de massa. / FAPESP: 2012/13642-8

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The atrophic disordinated action over an area leads to degradation of the natural resources, mainly the soil, water and native vegetation, changing the landscape, altering the ambience and bringing negative consequences to the social and economical conditions of the population. In such context, the current study had as its aims assess, through an ambience dossier, the physical-conservationist, social-economical and environmental degradation, giving priority to recuperation goals, as well as carry on a floristic survey of the riparian vegetation aiming, its recovering and a case study in family agro ecological system as an alternative way of management in the Watershed of Lajeado Biguá, Alecrim - RS. The ambiance dossier was carried on through observations and interviews with farmers of the studied micro basin. The floristic survey was done in randomly demarcated parcels along the banks of the Lajeado Biguá stream, where arboreal, herbaceous and shrub strata were sampled. In the agro ecological case study, a history of the property use was done, the current soil status was assessed and samples of the soil were taken in order to assess it main chemical and physical characteristics. The dossier results show that, among the main problems, the ones inherent to soil and water degradation stand out, mainly due to the inadequate management of this natural resources. The main cause of degradation is the soil preparation in a conventional way and the soil use in areas which should be of permanent reservation, as banks of rivers and steep areas. The degradation of riparian vegetation was caused by the use of the bank soil with crops and grazing, affecting the stream water quality and quantity and the water sources used by the population, as well as the riparian vegetation species and their natural regeneration capability. The riparian vegetation recover with the use of the species found in the floristic survey is recommended aiming its functions reestablishment. The agro ecology seems to be a viable system, mainly for small rural property, offering good productivity, crop diversification, healthy products, with higher demand and value-added smaller cost production with higher income to the producer, therefore increasing his/her social and economical conditions, being and alternative to the agricultural system in the studied micro basin. However, conservationist management ways are recommended, such as no-tillage, aiming the improvement of the chemical and physical soil characteristics, mainly the support of organic matter, which is the most affected by the conventional preparation used in the area studied and all over the watershed. / A ação antrópica desordenada sobre uma área leva à degradação dos recursos naturais, principalmente do solo, da água e da vegetação nativa, modificando a paisagem, alterando a ambiência e trazendo conseqüências negativas às condições sócio-econômicas da população. Neste contexto o presente estudo teve como objetivos avaliar através de um dossiê de ambiência a degradação físico-conservacionista, sócio-econômica e ambiental, priorizando metas de recuperação, bem como realizar um levantamento florístico da vegetação ciliar visando sua recuperação e um estudo de caso em sistema familiar agroecológico como forma alternativa de manejo na Microbacia Hidrográfica do Lajeado Biguá, Alecrim - RS. O dossiê de ambiência foi realizado através de observações in loco e de entrevistas com os agricultores da microbacia estudada. O levantamento florístico foi realizado em parcelas demarcadas aleatoriamente ao longo das margens do arroio Lajeado Biguá, onde se amostrou os estratos arbóreo, arbustivo e herbáceo. No estudo de caso agroecológico realizou-se um histórico de uso da propriedade, avaliou-se o uso atual dos solos e coletou-se amostras de solo para avaliar suas principais características químicas e físicas. Os resultados do dossiê mostram que, entre os principais problemas, destacam-se os inerentes a degradação do solo e da água, devido principalmente, ao manejo inadequado destes recursos naturais. A principal causa de degradação é o preparo do solo de forma convencional e o uso do solo em áreas que deveriam ser de preservação permanente, como margens de rios e áreas com declividade muito acentuada. A degradação da mata ciliar foi ocasionada pelo uso do solo das margens com lavouras e pastagens, afetando a qualidade e quantidade de água do arroio e das fontes usadas pela população, bem como as espécies da vegetação ciliar e a capacidade de regeneração natural destas. Recomenda-se uma recuperação da mata ciliar com o uso das espécies encontradas no levantamento florístico, visando restabelecer as funções desta. A agroecologia apresentou-se como um sistema agrícola viável, principalmente para a pequena propriedade rural, fornecendo boa produtividade, diversificação de culturas, produtos saudáveis, com maior procura e valor agregado, menor custo de produção e maior renda para o agricultor, melhorando assim suas condições sócio-econômicas, podendo ser indicada como alternativa de sistema agrícola na microbacia estudada. Entretanto, recomenda-se o uso de formas de manejo conservacionistas, como o plantio direto, visando melhorar as características químicas e físicas do solo, principalmente o aporte de matéria orgânica, que é o mais afetado pelo preparo convencional adotado na propriedade estudada e em toda microbacia.

Les cours d’eau font l’objet de prescriptions législatives encourageant leur restauration, et l’arasement de barrages est une des solutions utilisées actuellement en France pour y parvenir. La végétation riparienne participe à l’intégrité et à la stabilité des systèmes fluviaux, Elle est donc une composante majeure à évaluer dans le cadre des actions de restauration .Les objectifs de la thèse sont d'analyser la dynamique de colonisation des berges exondées à court terme dans le contexte de l’arasement des barrages de la Sélune (Normandie) et de développer des indicateurs de suivi à long terme des zones ripariennes. Dans un premier temps, une analyse des dynamiques de colonisation aux échelles intra et interannuelles réalisée à l’aide d’images drone et de relevés terrain a révélé la pertinence de l’utilisation d’images drones pour cartographier la végétation, ainsi que des dynamiques successionnelles rapides, avec un potentiel de restauration passive et de stabilisation des sédiments. Dans un second temps, l’analyse de nuages de points LiDAR en trois dimensions acquis en hiver et en été a montré la complémentarité des deux dates d’acquisition pour cartographier des indicateurs de statut des ripisylves à large échelle tels que les essences principales, l’ombrage ou la densité de strates herbacées et arbustives. Ces résultats permettent de discuter les dimensions méthodologiques et opérationnelles de l’utilisation des approches par télédétection pour le suivi des ripisylves. / Rivers are the object of legislation encouraging their restoration, and dam removal operations represent one of the solution to achieve it in France. Riparian vegetation plays a fundamental role in stabilizing and maintaining fluvial systems, being at the interface between terrestrial and aquatic environments. It is therefore a very important component which has to be evaluated in river restoration operations. One of the consequences of dam removal on riparian vegetation is the colonization of the dewatered sediments in the reservoir. The objective of the thesis are to define short term colonization dynamics of vegetation in context of dam removal (Sélune River, Normandy), and to develop long term indicators for the monitoring of riparian vegetation. First, an analysis of intra and interannual colonization dynamics revealed the potential of using drone images to map riparian vegetation, and fast successional dynamics with high passive restoration and sediment stabilization potential. Secondly, the analysis of 3D point clouds extracted from LiDAR data acquired in winter and summer highlighted the complementarity of the two acquisition dates to map indicators of riparian status at large scale, such as main riparian species, shading or density of herbaceous and shrubby strata. These results make it possible to discuss the methodological and operational dimensions of the use of remote sensing approaches for the monitoring of riparian vegetation

No description available.

Master of Arts / Department of Geography / Melinda Daniels / Large woody debris, (LWD), defined as pieces measuring ≥ 1 meter in length and ≥ 10 centimeters in diameter (Swanson and Lienkaemper, 1978; Marston, 1982) is an influential stream component. Once stable LWD obstructs streamflow and regulates key processes, causing increases in storage capacity, scouring, and variations to the bed, the extent contingent upon LWD’s average length of residence time within a system. Several North American studies have acknowledged the effects of interactions between wood, sediment, and flow regimes (Bilby, 1981; Keller, E.A., and Swanson, F.J., 1979; Montgomery et al., 1995; Wohl, E., 2008), linking the triad to geomorphic changes, the redistribution of bed materials, and ecological benefits. A consensual baseline reference for LWD’s function over time does not exist however, partly due to previous research being primarily conducted in the Northeast and Pacific Northwest regions where historic actions of humans, particularly riparian logging and stream clearing, have greatly impacted the condition of the watersheds. Researchers having long-overlooked the Great Plains and other regions not commonly associated with woody vegetation has increased the ambiguity regarding the transferability of LWD findings between regions. By shifting the focus to a non-forested region, the goal of this thesis is to measure the dynamics and influence of a prairie stream’s wood load on sediment storage and bed morphology. The Kings Creek network study area is located on the Konza Prairie Biological Station in northeastern Kansas, and drains one of few remaining unaltered North American watersheds. Results document the ongoing forest expansion into the surrounding pristine grassland, and provide a temporal context of the regions changing climate representative of atypical stream conditions caused by drought. In total, 406 individual pieces of wood were measured. The wood load was lower than most forest streams referenced (13.05 m[superscript]³/100 m), though higher than expected resulting from the absence of streamflow. LWD stored 108 m[superscript]³ of sediment within the channel, and the cumulative volume of LWD-formed pools was 169 m[superscript]³. Additionally, statistical analysis showed longitudinal bed variations to be strongly associated to LWD abundance, further indicating that LWD influences prairie stream processes similarly to those in a forest stream.