The processes and interactions that determine the width of a river channel remain a fundamental area of investigation in geomorphology. An increasing appreciation of the capacity of riparian vegetation to alter fluvial processes, and thus influence channel form, has highlighted the need to include vegetation in these analyses. However, a disconnect exists between the small spatial and temporal scales over which the linkages among flow patterns, sediment, and plants are evaluated and the larger spatial and temporal scales in which river systems operate. In this dissertation, I strove to identify some of the key mechanisms by which vegetation affects channel width. I worked to reconcile the issue of scale by developing a novel tool that resolves patch-scale (sub-meter) patterns of hydraulic roughness over the reach scale. While the approach can be generalized to evaluate any vegetated floodplain, the multi-scalar model was specifically applied to stands dominated by the non-native riparian shrub, tamarisk, that invaded the riparian corridor of southwestern US rivers during the past century. I focused my analyses on the lower Yampa River in western Colorado. Tamarisk colonized the Yampa in the absence of other environmental perturbations. As a result, adjustments to channel form may be linked to an altered vegetation community. From a careful geomorphic and vegetation reconstruction of the Yampa, I determined that tamarisk was the driving force in channel narrowing. Application of the multi-scalar model of vegetation resistance to the Yampa enabled me to reconstruct the changing hydraulic conditions as tamarisk established and the channel narrowed over time. This hydraulic reconstruction furthered our understanding of the interactions among vegetation recruitment patterns, the increased hydraulic resistance, and the changing flow and sediment transport field. Positive feedbacks between vegetation and geomorphic change created additional areas within the channel where tamarisk could establish, and thus accelerated the rate of channel narrowing. However, these feedbacks also changed the importance of common and large floods for vegetation establishment and sediment transport. Application of this process-based understanding to future flow regimes will help managers anticipate locations along the channel that are susceptible to vegetation encroachment and changes to channel width.

Over the last century, the construction and management of large dams and stream-flow diversions, and periodic drought have resulted in significant declines in stream flow of the lower Rio Grande in the Big Bend region. Reductions in mean annual flow and peak discharge have resulted in channel narrowing by the formation of vertically accreting inset floodplains. Narrowing has been temporarily interrupted by infrequent large dam releases greater than 1000 m3/s that have temporarily widened the channel; however, after each of these events, narrowing has resumed. Prior to 1942, floods of this magnitude occurred approximately once every 4 years and maintained a wide sandy channel. Since 1942, they have occurred 4 times. The decline in frequency of these large floods has resulted in a channel approximately 50% narrower than in the 1940s. Since the most recent channel widening floods in 1991, the channel has narrowed between 35 and 50%. In two large floodplain trenches, we observed between 2.75 and 3.5 m of vertical accretion during the same period. Additionally, nearly 90% of bare active channel bars have been converted to vegetated floodplains. Since 1991, the cross section channel area at the Johnson Ranch gage has decreased by approximately 30%. The reduction in cross section area and the invasion of non-native vegetation have resulted in higher flood stages, flooding at lower discharges, and continued vertical accretion. Channel narrowing has negatively impacted the native and endemic aquatic ecosystem through the loss of ecologically important habitats such as backwaters, side channels, and low velocity portions of the channel. Reductions in cross section area and resultant increased flood stages have also endangered historic cultural sites within the Big Bend region. Restoration efforts are currently underway within the region without a clear understanding of these historical channel changes and why they occurred. Our reconstruction of historical channel changes shows that the most significant periods of channel narrowing occurred during drought and increased stream-flow management. Management practices also appear to have enabled the invasion of non-native riparian species, which promoted sedimentation, bank stabilization, and additional channel narrowing. In order to restore historical measures of channel width, management options include non-native vegetation removal, common low magnitude dam releases that provide flood disturbance and prevent vegetation establishment, and large dam releases in excess of 1000 m3/s that create and maintain a wide channel. Vegetation management is expensive; and time consuming, and managed dam releases are politically unpopular and expensive, however, without the management of non-native riparian species and reinstatement of portions of the historical flood regime, ecological restoration will be difficult.

The diploma thesis assesses the current state of the Hulín gravel and sand plant and pays attention to abrasions of severely damaged banks of the reservoir. With the help of the design of a suitable biotechnical stabilization, the receding of the shoreline in the section of interest will be prevented. The basis for the processing of appropriate bank stabilization proposals is the results achieved using a method of determining shore retreat. The individual developed variants of the bank remediation solution emphasize the use of vegetation support, especially suitable bank stands to ensure the stability of the banks and protection against abrasion.

Northern boreal alluvial meadows are ecologically significant semi-natural ecosystems within the riparian zone. The effects of disturbance like flooding, grazing, and mowing have historically maintained high nutrient turnover and succession disruption that led to high biodiversity, leading to their inclusion in the Natura 2000 network. Today, alluvial meadows are threatened by human abandonment and river flow regulations, both of which provided necessary disturbances. This leads to encroachment by woody plants and a significant reduction in biodiversity. The purpose of this project was to investigate the hydrological conditions required for the long-term maintenance of floodplains of the regulated lower Dal River and how varying water levels affect the species distribution and various vegetation characteristics. This was done by examining plant data from 3 sites in an alluvial meadow in Bredforsen and datalogger water level data to calculate the duration of flooding of plots in a transect study. The effects of altitude, flooding durations, and frequencies on species richness, proportion of woody plants, and vegetation cover were examined. Flooding times showed the most significant effects on vegetation characteristics, while altitude and flooding frequencies differed greatly between sites, with variability explained being low for all explanatory variables. On one hand, this shows that that a lack of seasonal flooding has a negative effect on the alluvial meadow ecosystem and an increase in water flow would be beneficial. On the other hand, the low degree of explained variability implies that flooding solely is not the determining factor and other management methods are necessary to maintain the alluvial meadows.

Watercourses and especially their riparian vegetation are habitats that are very sensitive to spreading of invasive plant species. Rivers create natural migration routes (corridors) and help propagules to spread quickly and easily. The theoretical part of this thesis is focused on plant invasions and covers also the most recent knowledge in the field of invasion ecology. In the practical part of this thesis the spread of invasive neophytes in the riparian vegetation of the Kamenice river in Northern Bohemia is described. The plant species were examined during the field survey along the entire stream of the Kamenice river. In total, common occurence of 7 invasive taxa were recorded, namely Impatiens parviflora, I. glandulifera, Reynoutria japonica, R. sachalinensis, R. bohemica, Solidago gigantea and S. canadensis. The distribution of observed taxa along the stream as well as on the banks was relatively uneven.

As public awareness of river degradation has grown in recent years, the number of stream restoration activities has increased dramatically. Anthropogenic influences at a range of spatial scales from watershed landuse to riparian vegetation management to local channel morphology can have hierarchical relationships to local (meso- and macro-) in-stream habitat characteristics. This research examined these influences first by examining the influence of complex channel morphology on meso-scale brook trout (Salvelinus fontinalis) habitat in Shenandoah National Park, VA, and then by examining the combined influence of watershed urbanization and riparian vegetation (100-200 m reaches) on stream temperature. Moving beyond one-dimensional (1D) averaged representations of fish habitat, this research explored the distribution of two-dimensional (2D) flow complexity metrics at the meso-habitat scale as explanatory variables for brook trout habitat preferences and as potential metrics to evaluate habitat restoration design. Spatial hydraulic complexity metrics, including area-weighted circulation and kinetic energy gradients, were calculated based on 2D depth averaged modeled velocity distributions in two 100-m reaches on the Staunton River. While there were no statistically significant correlations between kinetic energy gradients or area-weighted circulation and fish density, fish density was positively correlated to the percent of the channel dominated by protruding boulders. The structural complexity of areas with protruding boulders create complex flow patterns suggesting that flow complexity plays an important role in available brook trout habitat preferences at the local scale, although the 2D depth averaged model may not have adequately represented this complexity. The 2D distribution of flow characteristics was then investigated further to quantify areas of flow refugia (low velocity shelters) and the relationship between these areas, traditional measures of habitat quality, and fish biomass. Flow complexity in the vicinity of flow obstructions (in this case, boulders) was investigated further using patch classification and landscape ecology metrics. The relative influence of riparian vegetation on stream temperature (another important habitat characteristic) in urban and nonurban watersheds was investigated in 27 paired forested and nonforested reaches in PA, MD, and DE. Riparian vegetation and watershed-scale urbanization both influence stream temperature, which can have profound impacts on in-stream ecosystems. Generally, increased urbanization and removal of riparian forest influenced maximum stream temperatures resulting in higher maximum summer stream temperatures (up to 1.8°C); however, the influence of riparian forests (at at 100-200 m reach scale) decreased with increasing urbanization. Extreme maximum summer temperatures, which are a concern for aquatic biota, increased in both frequency and duration in urban nonforested reaches relative to forested reaches indicating that the addition of a forested 100-200 m long buffer partially mitigated these temperature extremes even in urban watersheds. Overall, changes to channel morphology and riparian vegetation had measurable local effects on stream habitat (temperature and hydraulic complexity) yet the implications of restoration efforts at the local scale on ecosystem services at a larger (km +) scale requires further study. / Ph. D.

Stream ecosystems can be influenced by cattle grazing in the riparian zone due to sediment input, nutrient loading, and soil compaction, which lead to alterations of macroinvertebrate and microbial activity. Recently government programs, such as the Conservation Reserve Enhancement Program (CREP), have provided funding for farmers to exclude cattle from streams and riparian zones. Funding for CREP is limited and does not allow for post exclusion assessment. The objectives for this study were; 1) to explore whether CREP and other cattle exclusion initiatives help restore functional integrity to streams; 2) and if they do, to evaluate the time required for integrity to be restored. I predicted leaf processing (a fundamental ecosystem level function) in streams would be influenced by excluding cattle from the riparian zone due to changes in nutrient availability, sediment abundance, shredding macroinvertebrates, and microbial activity. I tested this prediction by measuring leaf processing at sites that had cattle excluded for <1 to 15 years. Breakdown rates did not correspond linearly to time since cattle exclusion. This was probably due to the opposing effects of elevated sediment versus nutrients on leaf breakdown at recently grazed sites. Leaf breakdown and shredder density were strongly correlated with riparian vegetation density. This study suggests that in addition to cattle exclusion, reforestation of woody riparian vegetation may be essential to restore functional integrity to agricultural streams. / Master of Science

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

Submitted by Mariana Dornelles Vargas (marianadv) on 2015-05-25T18:33:38Z No. of bitstreams: 1 influencia_mata.pdf: 1564434 bytes, checksum: d4085766e9b3221648da1454a2d57cca (MD5) / Made available in DSpace on 2015-05-25T18:33:38Z (GMT). No. of bitstreams: 1 influencia_mata.pdf: 1564434 bytes, checksum: d4085766e9b3221648da1454a2d57cca (MD5) Previous issue date: 2012 / Nenhuma / A presença ou ausência da mata ciliar é um fator que pode afetar a qualidade e disponibilidade de itens alimentares para peixes. O objetivo do presente trabalho foi testar a hipótese de que a extensão lateral da mata ciliar influencia a riqueza, abundância e alimentação da fauna de peixes. A partir da análise do conteúdo estomacal de quatro espécies de peixes, Bryconamericus iheringii (Boulenger, 1887), Characidium pterostictum (Gomes, 1947), Heptapterus mustelinus (Valenciennes, 1835) e Rineloricara microlepidogaster (Regan, 1904), foi possível realizar as análises de seletividade alimentar a fim de identificar alguma diferença e/ou padrão de consumo entre as áreas com vegetação ciliar densa e vegetação ciliar escassa. Os resultados deixaram evidentes que existe uma seleção positiva do consumo dos peixes para invertebrados aquáticos. Porém, não foi possível detectar as diferenças entre os dois tratamentos de mata das dietas das espécies. Nenhuma das espécies consumiu mais do que 2% de material alóctone. A não captação da influência da mata ciliar sobre a dieta dos peixes pode ter sido um efeito da escala espacial em que o trabalho foi realizado. As propriedades químicas, hidráulicas, morfológicas, de substrato e das associações com as comunidades biológicas dos copos hídricos são delineadas por muitos fatores da paisagem, que operam em diferentes escalas temporais e espaciais. Estudos afirmam que quanto maior é o grau de degradação das bacias hidrográficas menor vai ser a explicação dos fatores internos dos arroios sobre as alterações das comunidades. Devido a isso, é de suma importância a determinação dos fatores e da escala de influência sobre a comunidade íctica para se obter sucesso em ações de conservação e reabilitação dos corpos hídricos. / The presence or absence of riparian forest is a factor that can influence the quality and availability of food items for fish. The aim of this work is to test the hypothesis if the lateral extension of the riparian forest influences the richness, abundance and diet of fish fauna. By analyzing the stomach content of four fish species Bryconamericus iheringii (Boulenger, 1887), Characidium pterostictum (Gomes, 1947), Heptapterus mustelinus (Valenciennes, 1835) e Rineloricara microlepidogaster (Regan, 1904), it was possible to study their feeding selectivity in order to identify differences and/or consumption patterns in areas with dense riparian vegetation and areas with spare vegetation. The results show evidence for a positive selection for aquatic invertebrates in the diet of fish. However it was not possible to detect differences in the consumption concerning the type of vegetation. No species consumed more than 2% of allochthone material. The failed capture of the influence of the riparian for est on the diet of fish may have been an effect of the spatial scale design at which the work was done. The chemical, hydraulic, morphologic, substrate and associated biologic communities characteristics of the stream are delineated by many landscape factors, which are constrained by different temporal and spatial scales. Studies affirm that the greater the degradation of the watershed, the less explicable will be the internal factors of streams on changes in the community. Therefore it is of utmost importance to determine factors and scales of influence for ictic communities to ensure success in conservation and rehabilitation of water bodies.

Made available in DSpace on 2017-07-10T14:38:27Z (GMT). No. of bitstreams: 1 ALANA.pdf: 897893 bytes, checksum: e87322b1cd7ba37736824e4dfb614104 (MD5) Previous issue date: 2014-08-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The presence of riparian vegetation is unquestionable for the water quality of streams and rivers, because it buffers impacts coming from the surroundings of these ecosystems, particularly in areas used for agricultural and livestock activities. In this sense, this study aimed to evaluate and compare the composition and structure of the benthic invertebrate community in two first order streams, one located in an ecological corridor and another in continuous vegetation, but not set up as a corridor. We assumed that the riparian vegetation is the main factor influencing the water quality of these environments, especially the one inside the ecological corridor. To test our hypothesis, bimonthly sediment samples were taken with kick sampling for community analysis in three regions (headwaters, middle and mouth) of each stream. Samples were subjected to subsampling technique and invertebrates were identified to genus levels. The distribution and composition of taxa were similar between the two streams, with the exception of the headwaters of Apepu. In this sampling site, the sediment type and the successional stage of the riparian vegetation were not conducive to the integrity of the benthic community. However, community reestablishment was observed along the longitudinal axis of the stream according to the characteristics of natural environments and the presence of sensitive organisms. Furthermore, the similarity in biotic and abiotic composition of both streams highlight the importance of creating one more ecological corridor in the riparian vegetation of the Gualberto Stream, covering its watershed. These actions seek to preserve and maintain the biological diversity of water resources and ensure that measures aimed at water resource management are implemented and enforced as provided for in environmental legislation. / Este trabalho teve o objetivo avaliar espacialmente a influência da vegetação ciliar para a formação de corredores ecológicos, através da comparação da fauna de zoobentos de dois riachos, localizados em áreas internas e externas a um Corredor de Biodiversidade. Foram realizadas coletas bimestrais do sedimento com o coletor kick sampling para análise da comunidade, em três regiões (nascente, meio e foz) de cada riacho. As amostras foram submetidas à técnica de subasmotragem e os invertebrados foram identificados à nível de gênero. A distribuição dos táxons foi semelhante entre os dois riachos, com excessão da nascente do Apepu. Nesse ponto amostral o tipo de sedimento e o estágio sucessional da vegetação ciliar influenciaram negativamente na composição da comunidade. No entanto, foi possível observar a capacidade de resiliência desse riacho, através do reestabelecimento da comunidade de acordo com as carcaterísticas de ambientais naturais e a presença de organismos sensíveis. Devido a similaridade na composição biótica e abiótica ressaltamos a importância da criação de um corredor ecológico na região de mata ciliar do riacho Gualberto, a fim de preservar e manter a diversidade da comunidade de macroinvertebrados bentônicos na da região.