No description available.

Seventeen Earth system models (ESMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) were evaluated, focusing on the seasonal sensitivities of net biome production (NBP), net primary production (NPP), and heterotrophic respiration (Rh) to interannual variations in temperature and precipitation during 1982-2005 and their changes over the twenty-first century. Temperature sensitivity of NPP in ESMs was generally consistent across northern high-latitude biomes but significantly more negative for tropical and subtropical biomes relative to satellite-derived estimates. The temperature sensitivity of NBP in both inversion-based and ESM estimates was generally consistent in March-May (MAM) and September-November (SON) for tropical forests, semiarid ecosystems, and boreal forests. By contrast, for inversion-based NBP estimates, temperature sensitivity of NBP was nonsignificant for June-August (JJA) for all biomes except boreal forest; whereas, for ESM NBP estimates, the temperature sensitivity for JJA was significantly negative for all biomes except shrublands and subarctic ecosystems. Both satellite-derivedNPP and inversion-based NBP are often decoupled from precipitation, whereas ESM NPP and NBP estimates are generally positively correlated with precipitation, suggesting that ESMs are oversensitive to precipitation. Over the twenty-first century, changes in temperature sensitivities of NPP, Rh, and NBP are consistent across all RCPs but stronger under more intensive scenarios. The temperature sensitivity of NBP was found to decrease in tropics and subtropics and increase in northern high latitudes in MAM due to an increased temperature sensitivity of NPP. Across all biomes, projected temperature sensitivity of NPP decreased in JJA and SON. Projected precipitation sensitivity of NBP did not change across biomes, except over grasslands in MAM.

This thesis describes the biogeoclimatic zones on the southwestern British Columbia mainland and gives a detailed analysis of the vegetation-environmental patterns within the Coastal western hemlock zone. Ecosystem classifications are proposed utilizing coordination techniques and stratification. The major underlying causes of variations in the floristic structure among individual ecosystems are identified by four environmental gradients: regional climate, parent material, local climate (exposure), and soil-moisture regime. The orographic influence of Vancouver Island and the Coast Mountains results in a regional climatic gradient from low to high elevations. Natural segments of this gradient, recognized on the basis of zonal (climatic climax) vegetation and mesic soils, constitute the biogeoclimatic zones and subzones. Land types are separated from within the Coastal western hemlock zone on the basis of parent materials. The rock outcrop land type includes a mosaic of peaks, knolls, and crevices characterized by a coincident pattern of the vegetation types. All glacial drift deposits, except those of the swampy habitats, belong to the glacial drift land type. Maximum floristic variations in the glacial drift land type occur along a soil-moisture gradient. A lesser variation in the floristic structure is attributed to a local climatic gradient from cool to warm exposure. These gradients signify different sets of vegetation types in the different subzones of the Coastal western hemlock zone. The spring-water swamp land type includes waterlogged mineral soils and waterlogged woody peats in the vicinity of spring lines. The vegetation of the spring-water swamps has remarkable uniformity throughout both subzones. Narrow valley-like depressions with permanent or semipermanent streamlets and intermittent overflow water constitute the ravine alluvial land type. The vegetation of the ravines shows little variation among the two subzones. The flood-plain communities of the Squamish alluvial plain land type reflect the influence of overflow water and post-flood drainage. The basic unit of classification used is the ecosystem type, a segment in a simple vegetation-environmental gradient. A vegetation-environmental gradient is simple if it consists of a single set of vegetation types along an environmental gradient. Ecosystem type mapping involved approximately 85 acres in the southwestern part of the University of British Columbia Research Forest; a map is enclosed (in the thesis). / Science, Faculty of / Botany, Department of / Graduate

MENVSC / Department of Geography and Geo-Information Sciences / Many South African nature reserves, like the Kruger National Park (KNP) suffer from monthly below average rainfall that puts pressure in the diversity of wildlife animals in the park. Very little attention has been given to the behaviour of zebra population during period of low rainfall in KNP. Hence, this thesis seeks to examine the role of rainfall in the distribution of burchell’s zebra population from 1983 to 2012. Previous work has failed to explain the abundance of zebras in areas of low rainfall resulting from a long period of no rainfall in the area. Readily available data on rainfall and zebra population distribution was acquired from the KNP. The semi-logarithmic model was also proposed to estimate the probability of rainfall in the Kruger National Park. Three periods of low rainfall period were estimated from the graph and the years were further used to make comparison of how zebra behaves during periods when rainfall is low, medium or highest. GIS tools (spline and kernel) were used to analyse the trend between the years of zebras in relation to rainfall availability in Kruger National Park and a map was created with these tools. The study was based on a hypothesis that there exist a relationship between rainfall and the zebra population. The study advances our understanding of what determines the movement of burchell’s zebra in the park. The findings from the research show that the impact of rainfall on zebra distribution is more complex than previously assumed. The findings based on mapping were able to indicate that rainfall variability does not influence the distribution of zebra, rather more zebras were found in areas with sparse vegetation and avoid dense vegetation as much as possible. / NRF

Indiana University-Purdue University Indianapolis (IUPUI) / Water is fundamental for plant growth, and vegetation response to water availability influences water, carbon, and energy exchanges between land and atmosphere. Vegetation plays the most active role in water and carbon cycle of various ecosystems. Therefore, comprehensive evaluation of drought impact on vegetation productivity will play a critical role for better understanding the global water cycle under future climate conditions. In-situ meteorological measurements and the eddy covariance flux tower network, which provide meteorological data, and estimates of ecosystem productivity and respiration are remarkable tools to assess the impacts of drought on ecosystem carbon and water cycles. In regions with limited in-situ observations, remote sensing can be a very useful tool to monitor ecosystem drought status since it provides continuous observations of relevant variables linked to ecosystem function and the hydrologic cycle. However, the detailed understanding of ecosystem responses to drought is still lacking and it is challenging to quantify the impacts of drought on ecosystem carbon balance and several factors hinder our explicit understanding of the complex drought impacts. This dissertation addressed drought monitoring, ecosystem drought responses, trends of vegetation water constraint based on in-situ metrological observations, flux tower and multi-sensor remote sensing observations. This dissertation first developed a new integrated drought index applicable across diverse climate regions based on in-situ meteorological observations and multi-sensor remote sensing data, and another integrated drought index applicable across diverse climate regions only based on multi-sensor remote sensing data. The dissertation also evaluated the applicability of new satellite dataset (e.g., solar induced fluorescence, SIF) for responding to meteorological drought. Results show that satellite SIF data could have the potential to reflect meteorological drought, but the application should be limited to dry regions. The work in this dissertation also accessed changes in water constraint on global vegetation productivity, and quantified different drought dimensions on ecosystem productivity and respiration. Results indicate that a significant increase in vegetation water constraint over the last 30 years. The results highlighted the need for a more explicit consideration of the influence of water constraints on regional and global vegetation under a warming climate.

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Tsunamis impose significant threat to human life and coastal infrastructure. The goal of my dissertation is to develop a robust, accurate, and computationally efficient numerical model for quantitative hazard assessment of tsunamis. The length scale of the physical domain of interest ranges from hundreds of kilometers, in the case of landslide-generated tsunamis, to thousands of kilometers, in the case of far-field tsunamis, while the water depth varies from couple of kilometers, in deep ocean, to few centimeters, in the vicinity of shoreline. The large multi-scale computational domain leads to challenging and expensive numerical simulations. I present and compare the numerical results for different important problems --- such as tsunami hazard mitigation due to presence of coastal vegetation, boulder dislodgement and displacement by long waves, and tsunamis generated by an asteroid impact --- in risk assessment of tsunamis. I employ depth-integrated shallow water equations and Serre-Green-Naghdi equations for solving the problems and compare them to available three-dimensional results obtained by mesh-free smoothed particle hydrodynamics and volume of fluid methods. My results suggest that depth-integrated equations, given the current hardware computational capacities and the large scales of the problems in hand, can produce results as accurate as three-dimensional schemes while being computationally more efficient by at least an order of a magnitude. / Ph. D.

Laboratory experiments were conducted to investigate the velocity and turbulence characteristics in flows through rigid vegetation. The vegetation was simulated by an array of acrylic dowels mounted to the bed of a recirculating hydraulic flume. Velocity measurements were taken in both the longitudinal and vertical directions using a one-dimensional laser doppler velocimeter (LDV). Experiments were conducted under partially submerged, fully submerged and double layer flow conditions. The term double layer flow is used to describe flows that contain two different heights of vegetation. In each experiment, velocity and turbulence intensity profiles were taken at several different locations within the array. Additional experiments were conducted to examine how bed and vegetative skin roughness influence the velocity and turbulence characteristics. Belt sander strips were glued to the bed of the flume to simulate bed roughness and adhesive sandpaper was attached to the dowels to simulate vegetative skin roughness. Finally, experiments were conducted to study sediment transport and deposition in flows containing vegetation. / Master of Science

Thesis (Ph.D.)--University of Adelaide, Dept. of Geographical and Environmental Studies, 2001. / Includes bibliographical references (p. 301-319).

Please read the abstract in the section 00front of this document / Dissertation (MSc (Botany))--University of Pretoria, 2007. / Plant Science / MSc / unrestricted