Riparian ecosystems are of great importance in the landscape, connecting landscape elements longitudinally and laterally and often encompassing sharp environmental gradients in ecological processes and communities. They are influenced by fluvial disturbances such as flooding, erosion and sediment deposition, which create dynamic and spatially heterogeneous habitats that support a high diversity of species. Riverine ecosystems belong among the world’s most threatened systems. In rivers throughout the world, human alterations to fluvial disturbance regimes have resulted in degraded ecosystems and species loss. For example, in Sweden, watercourses of all sizes have been channelized to facilitate timber floating, but in the last 10–20 years the impacts in some of the affected rivers have been reduced by restoration actions. The objectives of this thesis are to evaluate how riverine ecosystems in general, with specific focus on riparian communities, are affected by (1) restoration of channelized reaches by boulder replacement, (2) ice formation, and (3) restoration of in-stream wood abundance in the stream channel. Objective (1) was assessed by quantifying the retention of plant propagules in channelized and restored stream reaches and by evaluating effects on riparian plant and bryophyte communities in disconnected and re-opened side channels. Retention of plant propagule mimics was highest at low flows and in sites where boulders and large wood had been replaced into the channel. Propagules are however unlikely to establish unless they can be further dispersed during subsequent spring high flows to higher riparian elevations suitable for establishment. Thus, immigration to new suitable sites may occur stepwise. Our study demonstrates that restoration of channel complexity through replacement of boulders and wood can enhance retention of plant propagules, but also highlights the importance of understanding how restoration effects vary with flow. We detected no differences in riparian diversity between re-opened and disconnected side channels, but we did observe significant differences in species composition of both vascular plant and bryophyte communities. Disconnected sites had more floodplain species, whereas restored sites had more species characteristic of upland forest. This suggests that the reopening of side channels resulted in increased water levels, resulting in new riparian zones developing in former upland areas, but that the characteristic floodplain communities have not had time to develop in response to the restored fluvial regime. Objective (2) was approached by evaluating the effect of both natural anchor ice formation and experimentally created ice in the riparian zone. Riparian plant species richness and evenness proved to be higher in plots affected by anchor ice. Plants with their over-wintering organs above the ice sheet suffered from the treatment but the overall species richness increased in ice-treated plots. Objective (3) was evaluated by studying wood recruitment and movement, channel hydraulics, propagule retention and fish abundance in streams restored with large wood. Only one stream experienced reduced velocities after large wood addition. The large size and reduced velocity were probably also the reasons why this stream proved to be the best one in trapping natural, drifting wood. Increased retention and decreased mechanical fragmentation in large wood sites will lead to decreased loss of detritus from the site and therefore higher availability of coarse particulate organic matter which can result in more species rich shredder communities. Our study did not show that the occurrence of large wood had an important role in controlling density or biomass of brown trout.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2018-05-22T12:40:15Z No. of bitstreams: 1 PDF - Marcos Medeiros Cavalcanti Júnior.pdf: 17695727 bytes, checksum: 8ec8c3d905e6ccd4d28ac1d4edaf0ff2 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2018-05-22T20:48:40Z (GMT) No. of bitstreams: 1 PDF - Marcos Medeiros Cavalcanti Júnior.pdf: 17695727 bytes, checksum: 8ec8c3d905e6ccd4d28ac1d4edaf0ff2 (MD5) / Made available in DSpace on 2018-05-22T20:48:40Z (GMT). No. of bitstreams: 1 PDF - Marcos Medeiros Cavalcanti Júnior.pdf: 17695727 bytes, checksum: 8ec8c3d905e6ccd4d28ac1d4edaf0ff2 (MD5) Previous issue date: 2017-02-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Leaf traits are directly linked to the life history of the organism. The amount of leaf N, the phenol content, or even the hardness of the leaves are important determinants for the survival and development of the plant, and, moreover, can directly influence ecosystem processes such as decomposition of organic matter. The amount and disposal of chemical and physical constituents of the leaf can determine its quality to the organisms responsible for accelerating the decomposition process, such as benthic invertebrates. Thus, the decay rates may be higher or lower, with direct effects on the cycling of matter within the ecosystem. In streams w ith riparian vegetation, leaf decomposition is an important process for input of matter and energy in the aquatic ecosystem. In semi-arid regions, plant species commonly need to develop strategies to mitigate the effects of drought and herbivores, such as the decrease in leaf nitrogen content, or the accumulation of secondary compounds in their leaves, which reduces its nutritional quality for invertebrates. The decrease in leaf quality of the riparian zone may have direct effects on the energy balance of aquatic systems. In addition, semi-arid regions have few papers related to the process of decomposition in aquatic ecosystems, which compromises the knowledge about an important part of cycling of organic matter in riparian vegetation regions. Among the questions on the subject, our goal with this study was to evaluate the effect of leaf traits of common species in semiarid regions on the colonization of invertebrates during decomposition in a stream. Based on the results obtained, we can characterize in a pioneering way how the process of leaf decomposition and colonization by invertebrates occurs in a stream in the semiarid. / Os atributos foliares estão diretamente ligados à história de vida do organismo. A quantidade de nitrogênio foliar, os teores de fenóis, ou mesmo a dureza da folha são importantes características determinantes para a sobrevivência e desenvolvimento do vegetal, e, além disso, podem influenciar diretamente processos ecossistêmicos como a decomposição da matéria orgânica. A quantidade e disposição dos constituintes químicos e físicos da folha podem determinar sua qualidade para os organismos responsáveis por acelerar o processo de decomposição, como os invertebrados bentônicos. Assim, as taxas de decomposição podem ser maiores ou menores, com efeitos diretos para a ciclagem da matéria dentro do ecossistema. Em riachos com vegetação ripária, a queda de folhas e sua decomposição é um importante processo para entrada de matéria e energia no ecossistema aquático. Em regiões semiáridas, as espécies vegetais comumente precisam desenvolver estratégias para diminuir os efeitos da seca e da herbivoria, como a diminuição dos conteúdos de nitrogênio foliar, ou o acúmulo de compostos secundários em suas folhas, o que reduz sua qualidade nutricional para invertebrados. A diminuição da qualidade foliar da zona ripária pode ter efeitos diretos sobre o equilíbrio energético dos sistemas aquáticos. Além disso, regiões semiáridas apresentam escassez de trabalhos relacionados ao processo de decomposição em ecossistemas aquáticos, o que compromete o conhecimento acerca de uma parte importante da ciclagem de matéria orgânica em regiões de vegetação ripária. Em meio aos questionamentos acerca do tema, nosso objetivo com o presente trabalho foi avaliar o efeito dos atributos foliares de espécies comuns em regiões semiáridas sobre a colonização de invertebrados durante a decomposição em um riacho. Com base nos resultados obtidos poderemos caracterizar de forma pioneira como se dá o processo de decomposição foliar e colonização por invertebrados em um riacho no semiárido.

Amostras da água subterrânea foram coletadas em poços piezométricos localizados em dois transectos ao longo das vertentes e dois transectos ao longo da cabeceira de drenagem de uma microbacia experimental, durante o período de maio de 2005 a abril de 2006. Em cada transecto os poços piezométricos estavam localizados respectivamente na parte alta da vertente, sob floresta plantada de Eucalyptus, na meia encosta, sob mata ciliar, e adjacente ao riacho. As análises destas amostras também foram comparadas com a análise simultânea da água do riacho, coletada na calha da estação linimétrica da microbacia. As análises químicas incluíram principalmente nitrato (N-NO3 -) e amônio (N-NH4 +), além do ferro, silício, alumínio, carbono orgânico dissolvido (DOC) e pH. O objetivo foi inferir sobre aspectos do funcionamento hidrológico da zona ripária, em termos de alteração da concentração dos íons analisados entre os pontos amostrados. A fim de inferir sobre o efeito da vegetação e das características do solo nas modificações da água subterrânea ao longo da vertente, foi realizado inventário para determinação da área basal da vegetação e análise granulométrica e química do solo. Os principais resultados mostram que na zona ripária adjacente ao riacho há maior concentração de matéria orgânica no solo e de amônio na água subterrânea. As concentrações de amônio e nitrato na água do riacho foram sempre menores do que as concentrações nos piezômetros adjacentes ao riacho próximo ao vertedor. Isso indica que na zona ripária ocorrem modificações na água subterrânea que garantem a manutenção do ecossistema lótico. Também foi possível identificar diferenças ao longo da microbacia, entre a cabeceira de drenagem e a área próxima ao vertedor, o que demonstra que a zona ripária não é homogênea na área da microbacia. A geologia, a granulometria e o teor de matéria orgânica do solo, a precipitação, o aumento do nível freático e a influência da água subterrânea, foram os principais fatores de alteração das demais variáveis do estudo. / Groundwater samples were collected in piezometers located in two transects through the hillslope and two in the headwater of an experimental catchment from May 2005 to April 2006. In each transect there were one piezometer in the upland under the Eucalyptus planted forest, one piezometer at the middle slope in the riparian area, and the other piezometer was located by the stream with a total of 12 piezometers. The samples collected fortnightly were analyzed and compared with the stream water collected in the stream gauging station. The main variables analyzed were nitrate (N-NO3 -) and ammonium (N-NH4 +) as well as iron, silicon, aluminum, dissolved organic carbon (DOC) and pH. The objective was to infer about riparian zone hydrology, based on the difference among chemical composition of the samples. A characterization of the experimental catchment was performed from a vegetation inventory and soil analysis in order to assess the influence of soil properties and vegetation nutritional demand on the chemistry of the solutions. Chemical analyses demonstrated that in the riparian zone close to the stream soil organic matter content was higher than in other topographic positions as well as concentrations of ammonium in the groundwater throughout the year. The concentrations of ammonium and nitrate in the groundwater beside the stream were always higher. These results indicated that in riparian zone the modifications in the groundwater contribute to the lotic ecosystem maintenance. The results also indicated that the riparian zone is heterogeneous along the catchment area and that the behavior of headwater and downstream may be different. The geology, soil granulometric and organic matter level, precipitation and groundwater level were the main factors that influenced the studied variables.

Freshwater systems have, during human history, endured large-scale impacts. According to the water framework directive, measures must be developed to create a better environment for species in, and connected to, freshwater systems. Hydropower plants has caused loss of natural disturbance (e.g., floodings). Using already collected data from vegetation inventory in the riparian zone, probable distribution curves were created to find flooding requirements of different plant species, and linear regression analyses were run to see if hours of flooding and elevation above sea level had an effect on species richness and vegetation cover in the riparian zone. A model of Bredforsen 3 was conducted by using modelled values obtained from Vattenfall AB, with the aim to answer the following questions: How is riparian vegetation in mixed alluvial forests in reaches affected by static minimum flow levels structured according to flow dynamics? What would the zonation of riparian vegetation look like in an unregulated situation? How can minimum flow in Bredforsen be designed to better match the flooding regime similar to a natural riparian vegetation? Species richness showed to be dependent on elevation. Furthermore, significant results for species richness and vegetation cover both showed to be dependent on hours of flooding in the riparian zone for two of the three inventoried areas. In the alluvial forest, Picea abies, was not affected by hours of flooding. This might be caused by a low number of replicates available in Bredforsen of P. abies. In contrast, Quercus robur did show a significance towards hours of flooding and a vague negative trend for trees with high inundation distributed on lower elevations, though, it seems more parameters are affecting its distribution. The probable species distribution curves revealed the riparian zone in Bredforsen lack the clear vegetative zones visible along unregulated rivers. However, the model created for Bredforsen 3, following the assumptions of Ström et al. (2012) showed that today two vegetative zones, are apparent in Bredforsen 3 (amphibian zone and upland vegetation). With the modelled flow, a third zone (riparian forest) could appear. Because Bredforsen is a Natura 2000 reserve, the minimum flow needs alteration to mimic a relatively natural flow, which could lead to all vegetative zones to develop (amphibian zone, graminoids, willow shrubs, riparian forest, and upland vegetation). This could be achieved by using the spill water from Söderfors and time the release of spill to natural flow events. The model made from Bredforsen 3 indicates that this could cause positive changes in the riparian zone where a more natural distribution of vegetative zones is in place, meaning that species distribution returns to previous distribution patterns and would help disturbance dependent species.

Understanding the effects of land use on riparian systems is dependent upon the development of methodologies to recognize changes in sedimentation related to shifts in land use. Land use trends in southern New England consist of shifts from forested precolonial conditions, to colonial and agrarian land uses, and toward modern industrial-urban landscapes. The goals of this study were to develop a set of stratigraphic indices that reflect these land use periods and to illustrate their applications. Twenty-four riparian sites from first-and second-order watersheds were chosen for study. Soil morphological features, such as buried surface horizons (layers), were useful to identify periods of watershed instability. The presence of human artifacts and increases in heavy metal concentration above background levels, were also effective indicators of industrial-urban land use periods. Increases and peak abundance of non-arboreal weed pollen (Ambrosia) were identified as stratigraphic markers indicative of agricultural land uses. Twelve 14C dates from riparian soils indicated that the rise in non-arboreal pollen corresponds to the start of regional deforestation (AD 1749 ± 56 cal yr; mean ± 2 SD) and peak non-arboreal pollen concentration corresponds to maximum agricultural land use (AD 1820 ± 51 cal yr). These indices were applied to elucidate the impact of land use on riparian sedimentation and soil carbon (C) dynamics. This analysis indicated that the majority of sediment and soil organic carbon (SOC) stored in regional riparian soils is of postcolonial origins. Mean net sedimentation rates increased ∼100-fold during postcolonial time periods, and net SOC sequestration rates showed an approximate 200-fold increase since precolonial times. These results suggest that headwater riparian zones have acted as an effective sink for alluvial sediment and SOC associated with postcolonial land use.

No description available.

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.

Alteration of river flow regimes due to dams result in modifications of riparian ecosystem, with impacts on vegetation, landforms, and habitats. A key characteristic that differentiates riparian zones from adjacent aquatic and terrestrial environments is the event of periodic flooding and water logging. In the regulated Dalälven and other regulated rivers, the Norway spruce (Picea abies) has been seen to replace deciduous hardwood forests over the years due to decrease in the frequency and duration of floods. This thesis aims to gain knowledge on the inundation duration needed to maintain riparian forests with deciduous hardwood trees along the regulated Dalälven. A laboratory experiment was conducted to assess the sensitivity of spruce seedlings to inundation with treatments varying in duration and depth of inundation and level of oxygenation. My hypotheses were that (1) mortality of spruce seedlings would be higher with complete submergence compared to only soils being waterlogged, and that (2) mortality would increase with duration of inundation, and (3) the mortality of spruce seedlings would be higher without oxygenation of water. The data was analyzed by comparing the plant vitality among treatments using analysis of variance using a binary logistic regression. The results indicated that as inundation time increased, the mortality of the seedlings increased. Since the laboratory experiment showed that a large proportion of spruce seedling died after being inundated for 22 and 44 days, reintroductions of floods shorter than the natural spring floods lasting about 1.5 months may be enough to aid in restore riparian forests dominated by oaks and other deciduous hardwood trees, e.g., in the regulated Dalälven river.

Water is a limited and highly valued resource in the semi-arid Great Basin. Surface water sources are often small and widely spaced apart, comprising only 1-3% of the surface area of the overall landscape. Despite their small size, these springs and surrounding wet meadows have a substantial effect on the surrounding environment. Springs provide drinking water, forage and cover for livestock and wildlife, habitat for diversity of plant species and a resource for human-related activities. In recent years, many of these springs have become dewatered due to diversions of groundwater for municipal water and agriculture, and climatic shifts in precipitation affecting recharge. These hydrologic changes can cause a drop in the local water table that promotes a shift in the plant community from wetland-obligates to species that have more drought-tolerance. The root masses of the new plant community are insufficient to secure soils resulting in the erosion of the thalweg. This leads to channelization through the wet meadow, which drives the water table further underground. As degradation progresses, springs and wet meadows lose their ability to store water. The purpose of this thesis is to examine the responses of both the hydrologic and biologic factors to different springbox restoration techniques. Twenty-four spring sites were chosen in the Sheldon National Wildlife Refuge in northwestern Nevada. Each site was randomly assigned one of six different treatment designs. Variables for these studies included: surface soil moisture, soil moisture at varying depths, flow rates, water chemistry, plant community cover and frequency, biomass, wildlife visits and wildlife species numbers. We observed soil moisture increase over the majority of our sites, while flow rates only increased at the control sites. This may indicate that more water is being held in the soils around the spring source instead of being allowed to flow downstream. Biomass increased in four of our six treatments. All treatment types exhibited a similar effect on springs with none having a clearly more restorative effective than any others. This research suggests that springs in the Great Basin have unique characteristics and responses to restoration, and may need individualized approaches. Additionally, studies have shown that it may take many years for plant communities to recover after hydrologic restoration. Yearly variation caused by increased precipitation may be partially responsible for changes in hydrologic and biologic aspects of springs and wet meadows. Further data collection is needed to determine the true extent of treatment and yearly effects on spring restoration. In spite of the need for individualized approaches, restoration is possible. Simple solutions may be sufficient to recover hydrologic processes that maintain ecologic resilience.

Nonpoint source (NPS) pollution is possibly the greatest form of contamination to our nation's waters. Nutrient pollutants, such as nitrate and ammonium, often enter aquatic ecosystems through surface and subsurface hydrological transport that drain agricultural watersheds. The over-abundance of nitrogen within these watersheds is easily transported to receiving stream and rivers, and result in aquatic ecosystem degradation. In response to the problem of nutrient loading to aquatic ecosystems, ecosystems scientists and federal and state governments have recommended the use of streamside management zones (SMZ) to reduce the amount of NPS pollutants. A small agricultural watershed in southwestern North Carolina was utilized to quantify subsurface transport of nitrate and ammonium to a naturally developing riparian area along Cartoogechaye Creek. Vertical and lateral transport of nitrate and ammonium were measured along three transect perpendicular to the stream. Transects were instrumented with time domain reflectometry (TDR) and porous cup tension lysimeters to monitor soil water and nutrient flux through the pasture and riparian area located at the base of the watershed. The HYDRUS 2-D flow and transport model was used to predict and simulate subsurface flow. Predicted flow was coupled with observed field nutrient data to quantify nutrient flux as a function of slope location. HYDRUS 2-D was capable of simulating subsurface flow (saturated and unsaturated) as a function of observed soil physical properties (bulk density, saturated hydraulic conductivity, particle size distribution, water retention characteristics) and climatic data (precipitation, air temperature, wind speed, etc.). The riparian area was effective in reducing the amount of nonpoint source pollution to a naturally developing riparian area from an agricultural watershed. Dramatic decreases in both NO3- -N and NH4+ -N in upland pasture water were observed within the riparian area. Seasonal percent reductions of NO3- from the pasture to riparian area in subsurface water within the study watershed are as follows: summer (2002) = 456%; fall (2002) = 116%; winter (2003) = 29%; spring = 9%, pasture and riparian, respectively. / Master of Science