This study uses a fieldwork-modelling research methodology to investigate hydrological pathways and chemical transport in floodplains and riparian zones, which occupy a key position in the landscape at the catchment-river interface. A numerical model is developed (ESTEL2D-SUBIEF2D) that is capable of modelling subsurface water and chemical movement at a high spatial and temporal resolution. The model is used in conjunction with data from two field sites (a lowland floodplain on the River Severn, UK, and a headwater riparian zone on Sleepers River, USA), and with hypothetical tracers, to quantify the effect of a range of factors on the operation of hydrological and biogeochemical processes in floodplain systems. This study shows the relative importance of river and hillslope inputs of water and chemicals to the floodplain, and how the scale of hydrological event (overbank flow, bankfull flow and low flow) affects the interaction of these sources. For example, in the case of an overbank flood event, hillslope inputs can be held back by the steep hydraulic gradient induced by flood water for up to 10 days. A comparison of headwater and lowland floodplains is attempted for the first time and indicates that different hydrological processes operate in these two environments. This implies that results from existing smaller scale riparian zone studies cannot simply be 'scaled up' to larger, lowland floodplain zones. The operation of the denitrification process within the floodplain is investigated as a relevant example of the more general transport modelling capability of the numerical code. This supports and extends the results of previous studies which have suggested that denitrification in the floodplain may be fundamentally limited by the interaction of hydrological processes and carbon availability. This comprehensive exploration of the full range of subsurface flow pathways through the floodplain highlights the importance of an understanding of hydrological pathways as critical to understanding chemical transport within the floodplain system.

As part of the effort to satisfy the ever increasing demand for a greater understanding of fluvial, hydrological, chemical, sedimentological and geomorphological processes operating on the floodplain, mathematical simulation models have come to play a significant role in the understanding, prediction and management of the floodplain environment. Underlying the accurate numerical representation of hydraulically driven processes is the provision of a suitable floodplain hydrology model which accounts for the interaction between surface hydraulics and subsurface hydrology. Such a numerical representation is currently not available at the spatial and temporal resolution required. It is the aim of this thesis to develop a novel conceptual approach to modelling floodplain hydrology in which the fundamental need to consider the interaction between surface and subsurface flow is the floodplain environment is addressed. This is achieved through the interactive coupling of a one-dimensional finite difference infiltration model with the state-of-the-art two-dimensional physically based finite element hydraulic model, TELEMAC2D. The coupled model provides an unparalleled spatial and temporal representation of surface and subsurface flow processes within the floodplain environment. The utility of this integrated approach is explored through an application of the model to two areas of contemporary floodplain research. In the first of these the model is run to assess the impact of infiltration on flood flow prediction for an llkm reach of the River Culm, UK, over a range of flood and soil conditions. In the second the model is run to investigate the nitrate buffering potential of floodplain riparian soils during flooding. For this investigation a model accounting for nitrate transport and denitrification is developed within the existing integrated hydraulic-infiltration model structure. An evaluation of the results from both of these investigations supports the need for a new approach to modelling fluvially driven floodplain processes which accounts for the spatially interactive nature of floodplain hydrology.

Public recognition of the value of wetlands has risen quickly over the past 25 years and numerous policies and programs have been developed to address threats to the quantity and quality of wetlands. However, management of wetland resources located on private land often involves a perceived conflict between social and private interests since landowners usually cannot benefit economically from keeping wetlands on site unless they convert them to alternative uses such as agricultural crops. In order to avoid further degradation and ensure the various environmental benefits wetlands provide, there is a need for government intervention by delivering effective policies. This will be realized through an effective economic valuation process for wetland benefits.<p> This thesis investigates wetland and riparian zones management, with greater emphasis placed on the Prairie Pothole Region (PPR) of Saskatchewan where the majority of the land is privately owned. Using data from a survey of landowners, the perceived cost of conserving wetland and associated riparian zones is quantified through their willingness to accept (WTA) compensation for a proposed 10-year economic incentive-based program. In addition, the role of landowner and farm characteristics on this perceived cost of conservation has also been assessed. As indicated by the results from two probit models that were developed, per acre payment has a significant positive effect on the probability a landowner will accept the program offer; the average payment respondents required being $32.58/acre. Other factors such as the landowners previous experience dealing with the wetland, personal preferences correlated with economic benefits and landowners who have an heir to take over the farm are also found to have significant impact on their participation decision. For those respondents who did not complete the WTA question, past relative experience, knowledge about wetlands, age, and the agricultural region the farm is located are revealed to be factors that affect to the provision of an explicit answer.

Public recognition of the value of wetlands has risen quickly over the past 25 years and numerous policies and programs have been developed to address threats to the quantity and quality of wetlands. However, management of wetland resources located on private land often involves a perceived conflict between social and private interests since landowners usually cannot benefit economically from keeping wetlands on site unless they convert them to alternative uses such as agricultural crops. In order to avoid further degradation and ensure the various environmental benefits wetlands provide, there is a need for government intervention by delivering effective policies. This will be realized through an effective economic valuation process for wetland benefits.<p> This thesis investigates wetland and riparian zones management, with greater emphasis placed on the Prairie Pothole Region (PPR) of Saskatchewan where the majority of the land is privately owned. Using data from a survey of landowners, the perceived cost of conserving wetland and associated riparian zones is quantified through their willingness to accept (WTA) compensation for a proposed 10-year economic incentive-based program. In addition, the role of landowner and farm characteristics on this perceived cost of conservation has also been assessed. As indicated by the results from two probit models that were developed, per acre payment has a significant positive effect on the probability a landowner will accept the program offer; the average payment respondents required being $32.58/acre. Other factors such as the landowners previous experience dealing with the wetland, personal preferences correlated with economic benefits and landowners who have an heir to take over the farm are also found to have significant impact on their participation decision. For those respondents who did not complete the WTA question, past relative experience, knowledge about wetlands, age, and the agricultural region the farm is located are revealed to be factors that affect to the provision of an explicit answer.

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / According to the River Continuum Concept, in small rivers, corresponding to ~ 80% of river basins, the main energy source for the trophic chain is the material produced in riparian zones, especially leaves. This material goes through the process of decomposition, which is responsible for the nutrients cycling and maintenance of aquatic communities. In this context, the objective of this study is to investigate the effects of physical, chemical and physiological traits of plant species on microbial activity and fragmentation, and as a consequence on decomposition rates. In the first chapter we investigated the activity of Phylloicus fragmentation in relation to food resources with different leaf traits. We found that the shredders have their food activity stimulated by substrate with less amount of lignin, which facilitates fungus conditioning and promotes the palatability of the detritus. In the second chapter, we investigated the feeding preference and assimilation of C3 and C4 carbon by Phylloicus and Aegla longirostri. We found that the shredders consume more the C4 species, but do not alter its isotopic signature and the intense activity of the hyphomycetes in the leaves C4 stimulated the consumption by the shredders. In the third chapter we investigated the effect of nutrient enrichment on soil and water on leaf nutritional quality and decomposition rates. We showed that the fertilized trees promoted leaves more nutritious than leaves of unfertilized trees. In addition, we found that the effect of nutrient enrichment on water was stronger than the nutrient enrichment of leaves in the decomposition process. Within the three chapters, we verified that the activities of the shredders and fungi are influenced by the characteristics of the leaves and are related to the riparian vegetation, especially by C3 carbon. We verified that the structural compounds are determinant for the microbial colonization and consequently for the fragmentation and litter decomposition. We also verified that the enrichment of nutrients in the water may be more important for the process of leaf decomposition than the nutrients in the leaves. / De acordo com a teoria do Contínuo Fluvial, nos pequenos rios florestados, que correspondem a ~80% das bacias hidrográficas, a principal fonte de energia para a cadeia trófica é o material produzido nas zonas ripárias, especialmente folhas. Este material passa pelo processo de decomposição, que é responsável pela ciclagem de nutrientes e manutenção das comunidades aquáticas. Neste contexto, o objetivo deste estudo é investigar os efeitos dos traços físicos, químicos e fisiológicos das espécies vegetais na atividade de microrganismos e invertebrados decompositores, e como consequência nas taxas de decomposição. No primeiro capítulo investigamos a atividade de fragmentação de Phylloicus frente a recursos alimentares com características foliares diferentes. Nós constatamos que os fragmentadores têm sua atividade alimentar estimulada por substrato com menor quantidade de lignina, o que facilita o condicionamento por fungos e promove a palatabilidade do detrito. No segundo capítulo, investigamos a preferência alimentar e assimilação C3 e C4 por Phylloicus e Aegla longirostri. Constatamos que os fragmentadores consomem mais a espécie C4, porém não alteram sua assinatura isotópica. E a intensa atividade dos hifomicetos nas folhas C4 estimulou o maior consumo pelos fragmentadores. No terceiro capítulo investigamos o efeito do enriquecimento de nutrientes no solo e na água na qualidade nutricional das folhas e nas taxas de decomposição. Evidenciamos que as plantas fertilizadas geraram folhas mais nutritivas que as não fertilizadas. Além disso, averiguamos que o efeito do aumento de nutrientes na água foi mais forte do que o efeito de nutrientes das folhas no processo de decomposição. Com os três capítulos verificamos que as atividades dos fragmentadores e fungos são influenciadas pelas características das folhas e estão relacionadas com a vegetação ripária, especialmente por carbono C3. Constatamos que os compostos estruturais são determinantes para a colonização microbiana e por consequência para a fragmentação e decomposição foliar. Verificamos também que o enriquecimento de nutrientes na água pode ser mais importante para o processo de decomposição foliar do que os nutrientes nas folhas.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: see item for full text / AFRIKAANSE OPSOMMING: sien item vir volteks

<ul><li>As the human population expands, agricultural expansion and intensification will exert an increasing pressure on remaining habitats, especially in the tropics. Oil palm is one of the most rapidly expanding crops in these regions, and identifying management strategies that conserve biodiversity and ecosystem services in these landscapes is therefore a priority. I assess whether riparian forest fragments (riparian reserves) conserve species and the functions they support within oil palm landscapes. Riparian forests are legally required for their beneficial impact on hydrological dynamics and their potential to contribute to the conservation of terrestrial species is poorly documented. I focussed on two ecologically important indicator groups (ants and dung beetles) and the ecosystem processes that they support. Whilst protecting primary forest will remain the most important strategy for biodiversity conservation, I found that riparian reserves do support species of ants and dung beetles that would not otherwise persist in oil palm landscapes. However, the extent to which riparian reserves maintained key ecological functions differed between these two taxa. The amount of nutrient distribution carried out by ants in riparian reserves was similar to logged forest areas, and higher than in oil palm. In contrast, dung removal functions did not vary between these land uses. I also investigated how the vegetation structure and landscape context of riparian reserves affects the dung beetle communities they support. Increasing reserve width and proximity to other forest fragments had a positive impact on the species richness and diversity of dung beetles in riparian reserves. There was little evidence that riparian reserves enhance the provision of dung removal or pest control services in adjacent areas of oil palm. >The results provide evidence to support the introduction and/or enforcement of legislation to protect riparian forest reserves in order to conserve biodiversity and ecological processes in oil palm landscapes.

Embora o nitrogênio seja um nutriente limitado, em excesso, ele pode causar a degradação de sistemas aquáticos. Apesar de, no âmbito nacional, o Brasil não apresentar problemas de escassez hídrica, regiões altamente populosas já tem enfrentado problemas de déficit hídrico, inclusive em função da poluição difusa de nitrogênio. Zonas ripárias têm sido apontadas como um dos atributos da bacia hidrográfica que pode ajudar na melhoria e manutenção da qualidade hídrica devido a sua capacidade de retirar nitrogênio do sistema terrestre oriundo de fontes difusas. Essa característica lhe é conferida por serem ambientes favoráveis ao processo de desnitrificação. A desnitrificação é um dos processos, se não o primeiro, responsável por converter o nitrato para formas gasosas N2O e N2. Considerando que os estudos sobre a função desempenhada por vegetações ripárias como sumidouro de nitrogênio se concentraram em países de clima temperado e que paisagens alteradas são o uso da terra majoritário no Estado de São Paulo, onde o problema de déficit hídrico já é uma realidade. Entender o papel que zonas ripárias desempenham sobre a dinâmica do nitrogênio torna-se fundamental para o desenvolvimento de estratégias de manejo do uso da terra voltadas para a manutenção da qualidade de sistemas aquáticos em regiões tropicais. O objetivo do trabalho é investigar se existe mudança dos processos que regulam a dinâmica do nitrogênio no solo em paisagens alteradas, enfatizando o papel desempenhado por vegetações ripárias como sumidouros de nitrogênio. A bacia hidrográfica do ribeirão Caxambu, com elevada influência antrópica, foi selecionada. Dentro dela dois rios foram escolhidos: (i) ribeirão Cachoeira drenando uma vertente com uso pastoril, na qual o pasto se estende até a zona ripária e (ii) ribeirão Caxambu drenando uma vertente agrícola com presença de floresta ripária. Extratores de solução do solo foram instalados ao longo de ambas vertentes para a quantificação do nitrogênio inorgânico dissolvido (NID) transportado ao longo de um ano. Amostras de solo foram coletadas nas porções: ripária e encosta de ambas vertentes para a quantificação das taxas líquidas de mineralização e nitrificação e também da desnitrificação potencial em cinco meses ao longo de um ano. Variáveis físico-químicas, incluindo NID, foram monitoradas em ambos os ribeirões. Os resultados indicam que as florestas ripárias estão processando o nitrogênio mais ativamente do que pastos ripários. As taxas líquidas de mineralização e nitrificação foram significativamente superiores no solo de florestas ripárias em relação ao solo de pasto ripário. No entanto, não houve diferença estatística significativa entre solo de floresta ripária e pasto ripário com relação à desnitrificação potencial. Não houve mudança das concentrações de NID na solução do solo ao longo da vertente pastoril, sendo estas relativamente baixas. Contrariamente, na vertente agrícola, submetida à fertilização, houve redução da concentração de NID na solução do solo quando se passou da encosta agrícola para a floresta ripária. Essa redução pode ser atribuída também ao processo de desnitrificação. Porém, outros processos além da desnitrificação devem estar atuando como moduladores da dinâmica do nitrogênio no solo de florestas ripárias. Tendo em vista que houve redução da ciclagem de nitrogênio na pastagem em relação à floresta, a inferência sobre o papel que o pasto ripário poderia desempenhar caso haja um elevado aporte de nitrogênio para essa zona ripária foi limitada. Concluí-se que as florestas ripárias podem atuar como sumidouro de nitrogênio em ambientes tropicais alterados. Portanto, podem ser uma ferramenta para o manejo sustentável de recursos hídricos na propriedade rural / Although nitrogen is a limiting nutrient, in excess, it can lead to the degradation of aquatic systems. Despite the fact that at national level Brazil does not have problems of water scarcity; regions highly populated are already facing deficit of water, caused among other things by nitrogen diffuse pollution. Riparian zones have been indicated as an attribute of the watershed that can maintain quality of water because their capacity in preventing diffuse pollution. Denitrification is one, if not the primary process responsible for this function, converting nitrate to gaseous N2O or N2. Considering that studies about the role of riparian vegetations in removing nitrogen loads are concentrated in temperate countries, and that altered landscapes is the main land cover of the State of Sao Paulo, where water scarcity is already a problem; understanding about the role of riparian zones on nitrogen dynamics is fundamental to orient land management practices aiming at preservation of aquatic systems in tropical regions. The objective of this study is to investigate whether processes that regulate the nitrogen dynamic in the soil change among altered landscapes, emphasizing the role of riparian vegetations as nitrogen sinks. The study area is the Caxambu watershed which is under intense anthropogenic influence. Two streams were selected: (i) Cachoeira stream draining a pasture slope with a riparian zone under pasture use and (ii) Caxambu stream draining an agricultural slope with riparian forests. Soil solution extractors were installed in each slope to quantify the concentration of dissolved inorganic nitrogen (DIN) at 50 cm deep during one year. Soil samples were collected at four sites: riparian zone with pasture, upland with pasture, riparian zone with forest, and upland with agriculture in order to quantify net mineralization, net nitrification, and denitrification potential during five months, in a period of one year. Physical-chemical variables, including DIN, in each stream were monitored during one year. The results show that nitrogen cycling in riparian forests soils is more intense than riparian pastures. Net mineralization and net nitrification are higher at riparian forests in relation to riparian pastures and other sampled sites. However there is no significant difference between riparian forests and riparian pastures in relation to denitrification potential. There is no significant difference between DIN concentration in the soil solution at pasture slope, and these concentrations are relatively low. On the contrary, at the agricultural slope under fertilization DIN concentrations are reduced significantly as soil solution moves through the riparian forests. This reduction could be the result of higher denitrification that occurs at riparian forest soils. However, besides denitrification other processes may be playing important role as modulators of nitrogen dynamic in the soils of riparian forests. Because the results show that nitrogen cycling is lower in the pasture compared to forest, inferring about the role that riparian pastures could play as nitrogen sinks was limited. In conclusion there is an indication that riparian forests can play an important role as nitrogen sink at altered landscapes in tropical region. Therefore restoring riparian zones could be an interesting tool to further deterioration of aquatic systems

This study investigated the effects of a seasonally variable forage resource on herbivore population dynamics. This involved estimating the relative importance of environmental conditions, and the accessible and used forage resources, at different stages of the seasonal cycle to herbivores in different life-stages and at different points in the reproductive cycle. This study was carried out in the Richtersveld region in South Africa, using goats kept by semi-nomadic Nama pastoralists. In the main study site, the Richtersveld National Park (RNP), herd movements follow a general seasonal migratory pattern: herds are based in the riparian zone of the Orange River during the dry season, and on plains away from the river in the wet season. Over 800 uniquely marked female goats in three life-stages (adults, yearlings and kids) were monitored over a three year period (2007 to 2009). These goats were weighed at 2 - 3 month intervals to provide an estimate of body condition. Browse availability in the riparian zone was estimated using measurements at an individual branch-level and a whole tree-level. FPAR satellite imagery was used to estimate forage abundance outside the riparian zone. Goat density was mapped for each week of the study using census data and the herd positions. Goat body condition, survival rates and fecundity rates for each life-stage were modelled as a response to forage availability, density and climatic conditions. The riparian zone in the RNP was found to function as the key resource of the RNP goat population. Forage depletion by goat browsing resulted in a negative feedback on goat body condition. This decline in body condition was directly related to lower adult survival over the dry season. Fecundity was also most influenced by dry season conditions through the negative effect of poor body condition on pregnancy rates and birth rates. Asymmetric competition between life-stages, resulting from the riparian browse profile being depleted from the bottom-up, was predicted to have a strong effect on goat demography by contributing to differences in body condition and survival rates between life-stages. Wet season conditions appeared to have little effect on goat population dynamics, either through increased neonate survival or through a mass carry-over effect influencing dry season survival. Goat body condition and vital rates were compared between the RNP and the neighbouring Kuboes rangeland, which does not have access to the Orange River, to assess the impact of differences in their dry season forage resource. The long-term size and variability of the livestock population in the RNP was also compared with livestock dynamics in Paulshoek, a rangeland 250 km south east of the RNP. The a priori predictions of relative population dynamics in each region, based on perceived differences in the nature of the key resource in each region, were largely supported.