Abrupt and persistent reconfiguration of ecosystem’s structure and function has been observed on a wide variety of ecosystems worldwide. While scientist believe that such phenomena could become more common and severe in the near future, little is known about the patterns of regime shifts’ causes and consequences for human well-being. This thesis aims to assess global patterns of regime shifts in social-ecological systems. A framework for comparing regime shifts has been developed as well as a public forum for discussing knowledge about regime shifts, namely the regime shift database. The most common drivers and expected impacts on ecosystem services have been identified by studying the qualitative topology of causal networks as well as the statistical properties that explain their emergent patters. Given that long time series data for ecosystems monitoring is rather sparse, and experimenting with ecosystems at the scales required to understand their feedback dynamics is rarely an option; we also proposed an indirect computationally based method for monitoring changes in ecosystem services. I hope the results here presented offer useful guidance for managers and policy makers on how to prioritize drivers or impacts of regime shifts: one take home message is that well-understood variables are not necessary the ones where most managerial efforts need to be taken. I also hope the scientific community rigorously criticize our results, but also acknowledge that when doing theoretical or empirical work, our methods tend to ignore the multi-causal nature of regime shifts. By bringing back multi-causality to the scientific debate, I hope our results offer new avenues for hypothesis exploration and theory development on the human endeavour of understanding Nature. / Transiciones críticas o cambios de régimen en ecosistemas se definen como reconfiguraciones abruptas de su estructura y función. Estos cambios, en ocasiones inesperados, se han documentado en una gran variedad de ecosistemas en todo el planeta. Algunos científicos proponen que en el futuro cercano dichos fenómenos pueden volverse más frecuentes y severos. Sin embargo, sabemos muy poco sobre las causas y consecuencias potenciales para el bienestar humano. El objetivo de esta tesis es evaluar patrones globales de cambios de régimen en sistemas socio-ecológicos. Un marco conceptual para comparar cambios de régimen y un foro público de discusión sobre el estado del arte en su conocimiento fue desarrollado en la base de datos virtual www.regimeshifts.org. Las causas más comunes y los impactos en servicios ecosistémicos más esperados han sido identificados estudiando las propiedades topológicas de redes causales, así como las propiedades estadísticas que explican sus propiedades emergentes. Dado que experimentar con ecosistemas a la escala adecuada para capturar sus mecanismos causales generalmente no es una opción, y dado que la disponibilidad de datos de largo plazo necesarios para monitorear cambios de régimen son la excepción y no la regla, proponemos un método indirecto computacional para monitorear cambios en servicios ecosistémicos. Espero que los resultados sean de utilidad para actores encargados del diseño de políticas o del manejo de ecosistemas, especialmente espero que ofrezcan una guía sobre cómo priorizar causas y consecuencias de estos cambios de régimen: una lección clave es que las variables que mejor entendemos o las que más monitoreamos no son necesariamente aquellas en las que debemos enfocar las estrategias de manejo. También espero que la comunidad científica critique con rigor nuestros resultados, pero a su vez reconozca que tanto el trabajo empírico y teórico como los métodos que comúnmente se utilizan para estudiar cambios de régimen tienden a ignorar su naturaleza multi-causal. Al enfatizar la diversidad de sus causas, espero que los resultados ofrezcan nuevas posibilidades para la exploración de hipótesis y el desarrollo de teorías para entender mejor la Naturaleza. / Abrupt och ihållande omkonfigurering av ekosystems struktur och funktion har observerats i en mängd olika ekosystem världen över. Forskning visar på att dessa fenomen antas bli vanligare och allvarligare inom vår närmsta framtid. Kunskapen kring dessa s.k. regimskiften är dock bristfällig, framförallt kring dess konsekvenser för mänskligt välbefinnande. Denna avhandling syftar till att bedöma globala mönster av regimskiften. Ett ramverk för att jämföra regimskiften, samt ett offentligt forum, “the regime shifts database”, för att främja diskussion och sprida kunskap om regimskiften, har utvecklats. De mest förekommande drivkrafter och effekter på ekosystemtjänster har identifierats genom att studera kvalitativa topologiska och kausala nätverk, samt de statistiska egenskaperna som förklarar deras framväxande mönster. Då långvariga tidsserier av ekosystemövervakning är få, och då de experiment som krävs för att förstå regimskiftens återkopplingsdynamik sällan är möjliga, föreslås också en indirekt beräkningsmetod för övervakning av förändringar i ekosystemtjänster. Resultaten från denna avhandling ämnar ger värdefull vägledning för beslutsfattare om prioriteringsordningen mellan olika typer av drivkrafter och effekter av regimskiften. En viktig slutsats är att gedigen kunskap om en viss variabel inte nödvändigtvis ger området där insatser bör tillsättas. Vidare, genom att föra tillbaka multi-kausalitet till den vetenskapliga debatten, erbjuder avhandlingen nya vägar för hypotesprövning och teoriutveckling inom vår gemensamma strävan att förstå Naturen. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 4: Manuscript.</p>

Die Unterzeichnung und Ratifizierung des Übereinkommens über die biologische Vielfalt (Convention on Biological Diversity, CBD), auch als Biodiversitätskonvention bekannt, betreffen auch den Indonesischen Forstwirtschaftsektor. Das Forstwirtschaftsministerium hat allmählich den Fokus seiner Politik von der reinen Holzproduktion auf den international geforderten, sogenannten ökosystemaren Ansatz verlagert, der eine Strategie für das integrierte Management von Land, Wasser und biotischen Ressourcen umschreibt, die Schutz und nachhaltige Nutzung gleichermaßen vorantreibt (siehe www.cbd.int/ecosystem/). Das aktuelle Forst- bzw. Waldgesetz Nr. 41/1999 betont dementsprechend die Bedeutung der verschiedenen Waldfunktionen im Rahmen der forstlichen Bewirtschaftung und hat die betreffenden Manageprinzipien anerkannt. In diesem Zusammenhang sollten landschaftlicher Kontext und Landschaftsökologie als Schlüsselbegriffe genannt werden. Der Forstwirtschaftssektor bzw. die staatliche Forstverwaltung in Indonesien soll nicht länger einzelne Waldgebiete isoliert betrachten, sondern die gesamte Landschaft mit Blick auf die Bedeutung der Wälder und ihre möglichen Funktionen im Auge behalten. Gleichermaßen fordert der ökosystemare Ansatz (ecosystem approach) eine Verlagerung vom traditionellen und segregativen Schutz(gebiets)gedanken, welcher ungeschützte Bereiche ignoriert, zu einer ganzheitlichen Bewahrung natürlicher Ressourcen im landschaftlichen Kontext, was die Berücksichtigung aller Landnutzungstypen und eine intersektorale Zusammenarbeit erfordert. Dementsprechend erfordert das Forstmanagement forstliche Kompetenz mit Blick auf alle Arten von Ökosystemen. Die forstliche Verantwortung erstreckt sich von Naturlandschaften über ländliche bis hin zu urbanen Gebieten. Integrierter Natur- und Umweltschutz auf der Grundlage der Waldfunktionen erfordert auch die Koordination mit anderen Sektoren der räumlichen Entwicklung und die Zusammenarbeit mit den Landbesitzern. Dieses sind die neuen Herausforderungen für den Forstwirtschaftssektor und für die Förster. Diese Studie zeigt nicht nur, wie der ökosystemare Ansatz seitens der Indonesischen Forstpolitik und Forstverwaltung interpretiert und implementiert wird. Sie befasst sich auch damit, wie die in diesem Rahmen proklamierten Prinzipien als Leitfaden für die Forstentwicklung und die forstliche Zusammenarbeit in einem weiter gefassten ökologischen Kontext dienen können. Die Ziele der Studie sind folgende: 1) Fallbeispiele der indonesischen forstlichen Planungspraxis im Hinblick auf ökologische Waldfunktionen in ihrem landschaftlichen Kontext zu analysieren, 2) die Grundsätze des ökosystemaren Ansatzes als ein Konzept zu Schutz und Förderung der Biodiversität im landschaftlichen Kontext auszuloten, 3) die inhaltliche Bedeutung und Konsistenz der gegenwärtigen Waldfunktionenzuweisung in den dafür relevanten Indonesischen Gesetzen sowie deren Umsetzung in neueren Entwicklungsvorhaben zu prüfen, 4) die Hindernisse und Chancen in Indonesien zu identifizieren, 5) die Herausforderungen und Erfordernisse sowie Empfehlungen für die künftige Verbesserung des forstlichen Managements zu benennen. Der Forschungsansatz beruht auf dem Studium schriftlicher Quellen und auf örtliche Fallstudien zur Rolle der Forstverwaltung und ihrer Sektor-übergreifenden Kooperationen im Rahmen forstlicher und anderer Entwicklungsvorhaben im Einzugsgebiet des Solo Flusses auf Java. Das Quellenstudium umfasste zunächst die jeweiligen Projektberichte und -dokumentationen sowie inhaltlich erklärende oder ergänzende wissenschaftliche Veröffentlichungen; danach wurden die relevanten Rechtsgrundlagen und die dazu entwickelten Regelwerke (Ausführungsvorschriften, Richtlinien und Anweisungen) für die Umsetzung eines entsprechenden Managementansatzes entlang der Verwaltungshierarchie bzw. der räumlichen Zuständigkeiten erforscht und schließlich wurden die Beziehungen und Konsistenten zwischen diesen Rechtsgrundlagen und Instrumenten eruiert. Die Ergebnisse wurden involvierten Experten und Schlüsselpersonen vorgelegt, die mit Hilfe eines offenen, grob vorstrukturierten Gesprächleitfadens zu den Hintergründen, zum Projektverlauf und zu Projektergebnissen befragt wurden. Bedingt durch diese Rekonstruktion des Projektverlaufes wurde jedes Projektgebiet mehrfach besucht, und der Besuch dazu genutzt, sich ein eigenes Bild von der jeweiligen Lage zu verschaffen und gegebenenfalls nach weiteren Informationen zu suchen. Die Analyse betrachtet den Umgang mit den Prinzipien des ökosystemaren Ansatzes, gegliedert nach drei wichtigen Themenbereichen, nämlich: 1) den Einsatz eines adaptiven Managements, 2) die Berücksichtigung der gebietsspezifischen Verhältnisse und des Zustandes der jeweiligen Ökosysteme im Hinblick auf deren Aufbau, Funktionen und Integrität, und 3) die Einbeziehung von Stakeholdern und Wirtschaftsaspekten. Der erste Teil konzentriert sich auf das adaptive Management, besonders im Zusammenhang mit Organisations- und Verwaltungsaspekten. Die Ergebnisse der Studie zeigen, dass der Forstwirtschaftssektor in Indonesien strukturell seine Repräsentanz bis auf die lokale Ebene ausgeweitet hat. Allerdings mangelt es immer noch an angemessenen und zielführenden Verwaltungsrichtlinien zur Sicherung und Stärkung der biologischen Vielfalt und zum Schutz der Umwelt. Die derzeitigen Bestimmungen in der Forstwirtschaft sind ungeeignet, um mit den rapiden Entwaldungs- und Urbanisierungsprozessen im Untersuchungsraum umzugehen, denn sie sind ausschließlich auf die noch bestehenden Restwaldflächen ausgerichtet. Der zweite Teil befasst sich mit raumbezogenen Fragen zu Strukturen, Funktionen und Integrität der Waldökosysteme. Alle untersuchten Fälle zeigen, dass essentielle Grundsätze für einen zeitgemäßen Naturschutz sowie die technische Unterstützung und Durchführung fehlen. Aspekte wie die ausreichende Größe von repräsentativen Gebieten, der räumlich-funktionale Verbund von Habitaten, der Uferschutz oder die Berücksichtigung von Gebieten ohne Schutzstatus in einem umfassenden Schutzkonzept für den landwirtschaftlichen und urbanen Bereich bisher auf keiner Ebene forstlicher Zuständigkeiten berücksichtigt oder gar unterstützt worden sind Der dritte Teil der Analyse beschreibt die Berücksichtigung von Stakeholdern und Wirtschaftsaspekten. Die Ergebnisse machen deutlich, dass: 1) sich die Teilnahme und Berücksichtigung von Stakeholdern auf die Forstwirtschaftprogramme ‘social forestry‘ und ‘community forestry‘ und dabei auf die Funktionen der Güterproduktion und einzelne Fragen des Waldschutzes beschränkt. Allerdings umfasst sie auch die Zusammenarbeit zwischen Regierungsorganen, Geschäftssektoren und den Bauern 2) sich die ökonomischen Steuerungsmechanismen seitens der indonesischen Forstwirtschaft auf Anreizmechanismen beschränken, nicht jedoch Umweltkosten und Nutzen internalisiert werden oder gar finanzielle Abschreckungsmechanismen entwickelt worden sind, obwohl diese als Bestandteile des Umweltschutz- und Wirtschaftsrechtsgesetzgebung vorgesehen sind. Damit lässt das Forstmanagement in Indonesien noch immer entscheidende Lücken in der Umsetzung der EsA Managementprinzipien erkennen, wenngleich es v.a. wesentliche regulative und strukturelle Verbesserungen als Voraussetzung für die Umsetzung des ökosystemaren Ansatzes erfahren hat.

The Brenton Blue butterfly, Orachrysops niobe (Trimen) is currently only known to be extant at one locality in the southern Cape (the Brenton Blue Butterfly Reserve = BBBR), and currently globally Red Listed as "Critically Endangered". This research investigates the life history and ecological interactions of o. niobe and recommends management techniques for the BBBR. Adult nectar sources and female oviposition behaviour are described. The first two larval instars feed on the leaflets of the host plant Indigofera erecta Thunb., and the 3rd and 4th instar larvae feed on this plant's woody rootstock, attended by ants Camponotus baynei Arnold. Cannibalism takes place in the early larval stages. Adults emerge from late October - early December, from late January to early March, and occasionally there is a third brood in April. Morphological and behavioural features of the larvae are described, and larval growth patterns are compared to other polyommatines. The nature of the myrmecophilous behaviour is assessed and the phylogenetic relationships between Orachrysops, Euchrysops, Lepidochrysops, and other polyommatine genera are discussed. Ant assemblages at the BBBR are described from pitfall trap sampling and field observations of interactions between O. niobe larvae and ants. The ant assemblages at the BBBR, Nature's Valley Fynbos Reserve (NVFR) and Uitzicht 216/ 40 are compared. The potential impact of the Argentine ant at the BBBR is discussed. Adult and egg counts are used to study the population dynamics of O. niobe, leading to an estimate of the adult butterfly population and its fluctuations. A population dynamics model is constructed, and several factors impacting fecundity and mortality are assessed. Population studies on other polyommatines are compared and discussed. The morphology, reproductive biology and autoecology of the papilionoid legume I. erecta are described. An explanation is offered why the larvae of O. niobe are monophagous on this plant. Microhabitat variations cause changes in its vegetative morphology and this further explains the restricted range of O. niobe. The population dynamics of I. erecta is investigated and the effects of biotic and abiotic factors (including fire) assessed. Braun Blanquet methodology is used to sample and classify the vegetation communities at the BBBR. Ordination techniques are used to confirm the classification and to diagnose for environmental gradients. Hypotheses are generated about the ecological processes functioning at the site, and the environmental niche occupied by I. erecta. Correlations between the occurrence xxii of vegetation types and other plant species and I. erecta are sought and a strong association with Pterocelastrus tricuspidatus is demonstrated. Three study sites are described and the ecological history of the region is reconstructed. Ecosystems are no longer fully functional because natural fire regimes and megaherbivores are absent. It is suggested that O. niobe currently inhabits an interglacial refugium under stress from the current global warming trend. The remaining suitable habitat is threatened by coastal property development and environmental degradation. An increased population of o. niobe at the BBBR, and establishment of new populations is essential to avoid extinction. Management techniques are evaluated and a management strategy for the BBBR is proposed. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2006.

The purpose of this dissertation is to assess the contribution of protected areas (PAs) to the attainment of both conservation and social outcomes including poverty reduction within the Greater Serengeti Ecosystem in Tanzania. The research focused on the role of governance as a factor influencing the attainment of these goals. This research was carried out in the Serengeti, Ngorongoro and Meatu districts of Tanzania in 2012. Two villages were selected from each district using stratified sampling techniques to obtain villages bordering many PAs including the core PA (i.e. Serengeti National Park). A mixed methods approach was used in this research which comprised of quantitative interviews with 389 households, key informants interviews with 88 stakeholders, 12 focus group discussion and document analysis. The study used a quantitative questionnaire to measure the effectiveness of governance as perceived at the household level. The questionnaire yielded 10 governance factors that accounted for 85% percent of the explained variance using factor analysis. The findings indicated weak governance particularly for Ikorongo-Grumeti Game Reserve. When examined across the ecosystem, weak linkages were evident between the PA actors and other actors such particularly at local community level. There was no difference in governance scoring between community-based PAs and the more traditional top-down government owned PAs. Furthermore, local communities were not adequately represented in PA governance despite being important actors. Findings indicated mixed results in terms of conservation and social outcomes. Results indicate implied relationship between mixed outcomes and weak governance with weak outcomes thought to be related to weak governance. This study recommends adaptations in the Serengeti ecosystem particularly the re-engineering of the ecosystem governance structure to bring on-board more actors in decision-making and management processes and actions through increased linkages between governance actors, governance structures and processes. / Graduate / 0366 / 0768 / 0478 / akisingo@mwekawildlife.org

Littoral zone primary production is under-studied relative to the pelagic zone, despite recent work indicating its importance to the lake as a whole. Benthic extracellular material, shown to be important for food web dynamics and stabilization of the surrounding ecosystem in the marine intertidal, is even less frequently studied in lakes. I examined the environmental and community level drivers of benthic primary production, and found production to increase over the summer and to decrease with disturbance. I also found that maximum photosynthesis and efficiency under sub-saturating light both increased with depth, contrary to the existing, laboratory-derived paradigm of a trade-off between the two. I also examined how benthic primary production and environmental factors were correlated with the amount of extracellular material. I found that loosely bound colloidal extracellular material decreased with in situ photosynthesis and was affected by algal community composition, whereas tightly bound capsular extracellular material was affected only by date, indicating that capsular material is refractory in lakes just as it is in marine systems. Contrary to what is seen in marine systems, however, there were no direct effects of the environmental factors, possibly the result of physical differences between these systems. I also performed the first cross-ecosystem comparison of extracellular material. Despite relatively few studies from lakes and streams, and methods which have not been standardized, I found that lakes were similar to marine intertidal zones both in their median amounts of extracellular material and their relationships between extracellular material and chlorophyll a. This relationship appeared to be quite different in streams, with very low amounts of extracellular material found at sites with either high or low chlorophyll a concentrations. While the above studies will improve future estimates of lake carbon budgets and whole-lake production, my development of a permutation test for path analysis, and a novel application of the Bayesian principal components analysis, will assist all ecological studies that are often restricted in their sample sizes or compromised by missing data.

In this research, a recent version of the Boreal Ecosystem Productivity Simulator (BEPS), called BEPS-TerrainLab, was adapted to northern peatlands and evaluated using observations made at the Mer Bleue bog located near Ottawa, Ontario, and the Sandhill fen located near Prince Albert, Saskatchewan. The code was extended and modified with a major focus on the adequate representation of northern peatlands' multi-layer canopy and the associated processes related to energy, water vapour and carbon dioxide fluxes through remotely-sensed leaf area index (LAI) maps. An important prerequisite for the successful mapping of LAI based on remote sensing imagery is the accurate measurement of LAI in the field with a standard technique such as the LAI-2000 plant canopy analyzer. As part of this research, a quick and reliable method to determine shrub LAI with the LAI-2000 instrument was developed. This method was used to collect a large number of LAI data at the Mer Bleue bog for the development of a new remote sensing-based methodology using multiple endmember spectral unmixing that allows for separate tree and shrub LAI mapping in ombrotrophic peatlands. A slight modification of this methodology allows for its application to minerotrophic peatlands and their surrounding landscapes. These LAI maps were used to explicitly represent the tree and shrub layers of the Mer Bleue bog and the tree and shrub/sedge layers of the Sandill fen within BEPS-TerrainLab. The adapted version of BEPS-TerrainLab was used to investigate the in fluence of mescoscale topography (Mer Bleue bog) and macro- and mesoscale topography (Sandhill fen) on wetness, evapotranspiration, and gross primary productivity during the snow-free period of 2004. This research suggests that future peatland ecosystem modelling efforts at regional and continental scales should include a peatland type-specific differentiation of macro- and mesoscale topographic effects on hydrology, to allow for a more realistic simulation of peatlands' soil water balance. This is an important prerequisite for the reduction of currently existing uncertainties in wetlands' contribution to North America's carbon dioxide and methane annual fluxes from an ecosystem modelling perspective.

Littoral zone primary production is under-studied relative to the pelagic zone, despite recent work indicating its importance to the lake as a whole. Benthic extracellular material, shown to be important for food web dynamics and stabilization of the surrounding ecosystem in the marine intertidal, is even less frequently studied in lakes. I examined the environmental and community level drivers of benthic primary production, and found production to increase over the summer and to decrease with disturbance. I also found that maximum photosynthesis and efficiency under sub-saturating light both increased with depth, contrary to the existing, laboratory-derived paradigm of a trade-off between the two. I also examined how benthic primary production and environmental factors were correlated with the amount of extracellular material. I found that loosely bound colloidal extracellular material decreased with in situ photosynthesis and was affected by algal community composition, whereas tightly bound capsular extracellular material was affected only by date, indicating that capsular material is refractory in lakes just as it is in marine systems. Contrary to what is seen in marine systems, however, there were no direct effects of the environmental factors, possibly the result of physical differences between these systems. I also performed the first cross-ecosystem comparison of extracellular material. Despite relatively few studies from lakes and streams, and methods which have not been standardized, I found that lakes were similar to marine intertidal zones both in their median amounts of extracellular material and their relationships between extracellular material and chlorophyll a. This relationship appeared to be quite different in streams, with very low amounts of extracellular material found at sites with either high or low chlorophyll a concentrations. While the above studies will improve future estimates of lake carbon budgets and whole-lake production, my development of a permutation test for path analysis, and a novel application of the Bayesian principal components analysis, will assist all ecological studies that are often restricted in their sample sizes or compromised by missing data.

Ecosystem metabolism is an important indicator of aquatic ecosystem function. This thesis concerns ecosystem metabolism as recorded by daily variation in dissolved oxygen (DO) and δ18O-DO in an impacted temperate river network, the Grand River, Ontario, Canada, and specifically addresses the effects of stream size and human disturbance including agriculture, deforestation, and wastewater treatment plants (WWTPs). A suite of 14 sites in the Grand River network was selected with stream sizes varying from 2nd to 7th order. A transient model of river ecosystem oxygen metabolism, ROM-TM, was developed in order to calculate river ecosystem metabolic rates and reaeration rates from field observation of changes in DO and δ18O-DO. ROM-TM is an inverse modeling approach programmed using MATLAB. Key parameters describing the main metabolic processes, gas exchange, and isotopic fractionation, such as maximum photosynthetic rate (Pm), photosynthetic efficiency (a), respiration rate at 20℃ (R20), gas exchange coefficient (k), respiration isotopic fractionation factor (aR), and photorespiration coefficient (βR), can be obtained by matching of model predictions with field data. Besides being capable of teasing apart metabolic processes and gas exchange to provide daily average estimates of metabolic parameters at the ecosystem level, ROM-TM can be used to address issues related to light including light saturation phenomena at the ecosystem level, the effect of cloud cover on metabolic balance and photorespiration. Primary production responses to light along a longitudinal gradient in the Grand River network were described by means of P-I curves. Both light-limited and light-saturated conditions were observed. Production parameters Pm and Ik in the Grand River network exhibited an increase with stream order, while a was independent of stream size. However, a did vary among and within sites. Higher light availability in small and middle-sized streams without riparian trees was associated with high Pm, Ik and Ec, but low a. Ecosystem-level Pm in both small periphyton-dominated streams and large macrophyte-dominated rivers in the Grand River basin were generally less than community-level Pm values from the literature. However, two Grand River sites had comparable Pm to literature-derived Pm due to the prolific growth of macrophytes supported by high nutrient effluents from upstream WWTPs. Ecosystem-level a in my study streams were also less than those at the community level, indicating there was a declining trend of this parameter with scale, from individual, community to ecosystem. Derived parameters (e.g., Ik, Ec, and saturation point) increased from the individual level to the community level, and then to the ecosystem level. From May to early October, metabolic rates in the Grand River network (gross primary production, GPP = 0.4 to 20 and ecosystem respiration, ER = 2 to 33 g O2 m-2 day-1) were within the broad range of metabolic rates occurring in the temperate region, regardless of stream size. The Grand River network is a net heterotrophic system. The total GPP and ER for whole basin was 3.3e+08 and 4.2e+08 g O2 day-1, respectively. Reach geomorphology controls the spatial patterns of stream metabolism in the Grand River network, although the spatial patterns may be modified by effects of human disturbance on riparian vegetation, nutrients and other factors. Stream order and channel width, as measures of stream size, are good predictors of metabolic rates and ratios of GPP: ER from small streams to the central Grand River. Ecosystem metabolic rates and ratios generally increase with stream size, but with site-specific variation. The Grand River network is experiencing effects of human disturbance, mostly downstream of the urban areas and least in small streams with remaining riparian forest. The small and middle-sized streams (2nd to 4th order) without riparian trees in agriculture regions in the Grand River basin did not exhibit significantly different GPP and ER than their counterparts with riparian trees. The stimulative effect of increased light availability due to open canopy on GPP in non-shaded streams may be offset by shading from stream banks and riparian grasses, and unstable sediments resulting from agricultural activities. Large river sites impacted by WWTPs had significantly increased metabolic rates, both GPP and ER, compared to two upstream sites impacted by agriculture only. This result suggests that urban areas cause impacts on the Grand River that are superimposed on the impacts of agriculture. Three aspects of metabolism of the Grand River differ from the general pattern for the temperate regions: (1) a increase trend of GPP: ER ratios with stream size from 2nd to 7th order; (2) overall, human activities in the Grand River watershed have stronger positive effects on the GPP than on the ER; (3) the middle-sized to large river sites (5th-7th order) had greater influence than small to middle-sized streams (2nd-5th order) in the Grand River on overall GPP and ER. The general trend of GPP: ER ratio in tropical, subtropical, temperate, and global data approximately conforms to the predictions of the River Continuum Concept (RCC). However, the maximum ratio of GPP: ER in mid-reaches of river networks is not usually >1 as proposed in the RCC. There is a latitude and stream size shift phenomenon regarding where the peak ratio of GPP: ER occurs in each climate zone. The maximum GPP: ER ratio is higher at higher latitudes and occurs at higher order streams. The study of stream ecosystem metabolism can benefit from the addition of the second oxygen budget, δ18O-DO, in four ways: (1) it is better to use both DO and δ18O-DO budgets, rather than DO only, in sampling protocols with low temporal frequency but high spatial frequency; (2) the δ18O-DO time series data can provide relatively independent constraints on parameter estimation; (3) the addition of δ18O-DO in using two oxygen budgets to quantify metabolic rates provides a way, the cross-plot of δ18O-DO against fraction of DO saturation, to indicate trophic status of an aquatic ecosystem; and (4) the addition of δ18O-DO can provide an estimate of aR at the ecosystem level that can be used to understand factors affecting respiration.

Whitebark pine (Pinus albicaulis) is declining across its range due to disturbances such as mountain pine beetle and white pine blister rust. In this thesis, I assess the response and vulnerability of whitebark pine ecosystems to multiple stressors and disturbances at the northern edge of P.albicaulis range in the Coastal Mountains of British Columbia, Canada. Both the compositional change over time of overstory and understory communities as well as vegetation spatial patterns suggest that different sites or ecosystem types housing whitebark pine may differ in their response to disturbance and stress. Surveys conducted ~ 20 years apart indicate that overstory community change differed between site types following the decline of P. albicaulis over time, while the understory did not change significantly. The spatial pattern of overstory species and understory communities also indicates that site type may be important in determining forest change under ongoing disturbance to whitebark pine. / Forest Biology and Management

<p>In recent years, a global trend of increasing woody vegetation densities in semi-arid savanna habitats has been recorded, commonly described in South Africa as 'bush encroachment'. The shrubs and trees that do this (Increasers) have wrought significant economic and ecological impacts upon carrying capacities of large areas of savannas. This occurs, as suitable grazing areas are incrementally engulfed in shrubs and trees establishing new equilibria, from open savannas (essentially grasslands with scattered trees) into closed woodlands (treelands with scattered grasses). This thesis demonstrated a link between grass biomass, small mammal abundance and diversity, and their potential increaser seed/seedling predatory activities in the semi-arid Lowveld Savannas of South Africa.</p>