This study addresses the extrinsic factors which have shaped the evolution and maintenance of sociality in the African mole-rats. Specifically, the common mole-rat was used as a model to assess the Aridity Food-Distribution Hypothesis (AFDH), as an explanation for the evolution of bathyergid sociality. The AFDH correlates mole-rat sociality with habitat aridity and the pattern of food distribution. Aspects relating to ecological constraints, foraging behaviour, population demography, reproductive biology and aggressive behaviour were compared between an arid and a mesic population of C. h. hottentotus, to assess how inter-habitat divergence in ecological attributes has influenced social behaviour within these two populations. In evaluating the AFDH as an explanation for the evolution of sociality within C. h. · hottentotus two broad questions were addressed: (1) do the assumptions of the AFDH hold true i.e. do arid and mesic habitats exhibit ecological differences, specifically with regard to the pattern of resource dispersion and the energetic costs of foraging, which influence foraging risks and consequently the costs of dispersal? and (2) do these inter-habitat differences have implications for bathyergid social evolution i.e. do the common mole-rat populations inhabiting arid and mesic areas exhibit regional differentiation in social behaviour? Substantial inter-site divergence in ecological characteristics, notably climate and resource attributes, were revealed in this study. Rainfall at the arid site was markedly lower and more sporadic, and evaporation levels significantly higher, than at the mesic site. Moreover, thermal constraints were more limiting at the arid site. These features will greatly elevate the costs of soil excavation and the risks of hyperthermia, severely restricting the occurrence of suitable burrowing opportunities at the arid locality. Consequently, foraging will be severely constrained in this area. At the mesic site, higher, more predictable rainfall, low evaporation rates and reduced thermal constraints will translate into more suitable burrowing opportunities for much, if not all, of the year. Regional differentiation in food resource characteristics was also evident. Although geophytes were clumped at both study localities, the density of geophytes was lower and the distance between geophytes or geophyte clumps concomitantly greater at the arid relative to the mesic site. Differences in resource dispersion in turn influenced the patterns of foraging. In response to the low geophyte density and associated longer foraging distances, burrow systems were notably longer and more linear at the arid site. Furthermore, food storage and in situ harvesting were essential components of cooperative foraging in C. h. hottentotus as they minimised the risks of starvation, particularly in arid habitats. Thus, resource characteristics together with the climatic restrictions on burrowing in arid areas may have a marked impact on foraging behaviour, imposing severe constraints on the mole-rats occurring there and ultimately shaping their foraging responses. Together, these factors satisfactorily account for the underlying premise of the AFDH, that arid and mesic habitats exhibit ecological differences with regard to the pattern of resource dispersion and the energetic costs of foraging, which are likely to influence foraging risks and the costs of dispersal. In evaluating the AFDH, the second question which needed to be addressed was whether the study populations exhibited divergence in their social behaviour. The populations revealed no differences in absolute group size or in reproductive characteristics which were related to the effects of aridity per se. However, distinct inter-population divergence was readily apparent in phenotypically plastic traits such as dispersal behaviour and xenophobia. Clear differences were evident between the arid and mesic sites in both the quantitative and qualitative nature of dispersal; dispersal was markedly constrained at the arid site and colonies demonstrated greater temporal stability, with more predictable temporal group membership. The ecological constraints on successful foraging at the arid site will curb opportunities for dispersal and promote cooperation in the C. h. hottentotus occurring there. Colony members should therefore maximise their inclusive fitness by natal philopatry, delayed dispersal and cooperative foraging. Inter-site differences were also apparent in the response of colony members to foreign conspecifics. Common mole-rats from the arid site were markedly more xenophobic than those from the mesic site, and aggressively rejected foreigners. For arid-occurring populations, the fitness penalties for failing to exclude foreigners from the colony burrow system and associated resources, will be more severe than for mesic-occurring populations, resulting in heightened levels of xenophobia. Again, colony cohesion and cooperation in arid areas are essential to individual survival and inclusive fitness. The regional differences in dispersal patterns and xenophobia revealed in this investigation may reflect adaptive variation in social behaviour between the study populations, and the results suggest that delayed dispersal and cooperation may be more crucial to individual survival in arid than in mesic areas. As such these findings provide support for the underlying contention of the AFDH that ecological constraints on foraging in arid areas have promoted a greater degree of social elaboration in mole-rats occurring there. This study provides persuasive support for the AFDH as an explanation for the adaptive significance of social behaviour and cooperation in the common mole-rat, and together with other investigations, suggests that the AFDH provides a valid explanation for the evolution of group-living in the Bathyergidae.

Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-05-12T01:02:35Z No. of bitstreams: 1 NatanaelSP_TESE.pdf: 4294671 bytes, checksum: 7e2280a13326e374e43e597c5a5f40d9 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-05-16T12:05:06Z (GMT) No. of bitstreams: 1 NatanaelSP_TESE.pdf: 4294671 bytes, checksum: 7e2280a13326e374e43e597c5a5f40d9 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-05-16T12:05:25Z (GMT) No. of bitstreams: 1 NatanaelSP_TESE.pdf: 4294671 bytes, checksum: 7e2280a13326e374e43e597c5a5f40d9 (MD5) / Made available in DSpace on 2017-05-16T12:05:56Z (GMT). No. of bitstreams: 1 NatanaelSP_TESE.pdf: 4294671 bytes, checksum: 7e2280a13326e374e43e597c5a5f40d9 (MD5) Previous issue date: 2016-12-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The watermelon crop has great economic and social importance in the State of Rio Grande do Norte and, in this way, there is a great demand for information for an adequate management of fertilization, particularly for P, due to its dynamics in the soil and its Low availability in many soils of the region. Thus, the objective of this work was to evaluate the production and accumulation of nutrients by the cv. Magnum under the influence of the management of phosphate fertilization. The experiments were carried out in a Cambisol of medium texture, originating from limestone (Upanema-RN) and in a Ultisol of sandy texture (Mossoró-RN), in a randomized complete block design, with four replications. In the limestone experiment, treatments consisted of 76, 168, 275 and 397 kg ha-1 of P2O5, which were applied in two ways: F0- in pre-planting and F1-in pre-planting + cover (50 kg ha-1 of P2O5 by fertigation). Two additional treatments were applied: without phosphate; and with phosphate only in the cover (50 kg ha-1 of P2O5 by fertigation). In the experiment carried out in a sandy soil the treatments consisted of 34, 80, 168 and 206 kg ha-1 of P2O5, which were applied in two ways: F0- in pre-planting and F1-in pre-planting + cover (34 kg ha-1 of P2O5 by fertigation). Two additional treatments were applied: without phosphate; and with phosphate only in the cover (103 kg ha-1 of P2O5 by fertigation). In calcareous soil there was an isolated effect of doses and forms of application on the production characteristics, especially the highest dose of F1 fertilization in relation to F0. However, in general, the additional treatment with 103 kg ha- 1 of P2O5 in fertigation was shown to be more efficient, with commercial productivity equivalent to a dose of 204 kg ha-1 of P2O5 in F1 fertilization. Fertilization F1 provided higher accumulations of P and S, but in general the effects of fertilization were dose-dependent, with treatments F0275 and F1168 in terms of accumulation of biomass and other macronutrients. In sandy soil, there was an isolated effect of doses and forms of application on the production characteristics, especially the highest dose of F1 fertilization in relation to F0. However, in general, the additional treatment with 103 kg ha-1 of P2O5 in fertigation was shown to be more efficient, with commercial productivity equivalent to a dose of 204 kg ha-1 of P2O5 in F1 fertilization. At the dose of 137 kg ha-1 of P2O5, occurred higher accumulations of P in F1 fertilization, both in shoot and fruit. For Ca and Mg, greater accumulations occurred with F1 fertilization only in the vegetative part. Overall, about 50% of total macronutrient demand occurs in the last quarter of the cycle / A cultura da melancia tem grande importância econômica e social para o semiárido nordestino, existindo uma grande demanda por informações para um manejo adequado das adubações, particularmente para o P, em razão de sua dinâmica no solo e por sua baixa disponibilidade em muitos solos da região. Nesse contexto, o objetivo com este trabalho foi avaliar a produção, qualidade e o acúmulo de nutrientes pela melancieira cv. Magnum sob influência do manejo da adubação fosfatada. Os experimentos foram realizados em um Cambissolo de origem calcária de textura média (Upanema-RN) e em um Argissolo de textura arenosa (Mossoró-RN), no delineamento experimental de blocos ao acaso, com quatro repetições. Em solo calcário, os tratamentos consistiram nas doses de 76, 168, 275 e 397 kg ha- 1 de P2O5, as quais foram aplicadas de duas formas: F0- em pré-plantio e F1 – em pré-plantio + cobertura (50 kg ha-1 de P2O5 por fertirrigação). Foram aplicados ainda dois tratamentos adicionais: sem fosfato; e com fosfato somente por cobertura (50 kg ha-1 de P2O5 na fertirrigação). No experimento realizado em solo arenoso, os tratamentos consistiram nas doses de 34, 80, 168 e 206 kg ha-1 de P2O5, as quais foram aplicadas de duas formas: F0- em préplantio e F1 – em pré-plantio + cobertura (34 kg ha-1 de P2O5 por fertirrigação), sendo aplicados ainda dois tratamentos adicionais: sem fosfato; e com fosfato somente em cobertura (103 kg ha- 1 de P2O5 por fertirrigação). Em solo calcário houve efeito isolado de doses e formas de aplicação sobre as características de produção, com destaque para a maior dose da adubação F1 em relação a F0. Porém, de forma geral, o tratamento adicional com 103 kg ha-1 de P2O5 na fertirrigação mostrou ser mais eficiente, com produtividade comercial equivalente a uma dose de 204 kg ha-1 de P2O5 na adubação F1. A adubação F1 proporcionou maiores acúmulos de P e de S, porém, de forma geral, os efeitos das formas de adubação foram dependentes das doses, destacando-se os tratamentos F0275 e F1168 em termos de acúmulo de biomassa e dos demais macronutrientes. Em solo arenoso, houve efeito isolado de doses e formas de aplicação sobre as características de produção, com destaque para a maior dose da adubação F1 em relação a F0. Porém, de forma geral, o tratamento adicional com 103 kg ha-1 de P2O5 na fertirrigação mostrou ser mais eficiente, com produtividade comercial equivalente a uma dose de 204 kg ha- 1 de P2O5 na adubação F1. Na dose de 137 kg ha-1 de P2O5, maiores acúmulos de P, tanto na parte aérea, como nos frutos ocorrem na adubação F1. Para Ca e Mg ocorreram maiores acúmulos com a adubação F1 apenas na parte vegetativa. De forma geral, cerca de 50% da demanda total dos macronutrientes ocorre no quarto final do ciclo / 2017-05-11

Submitted by Mario BC (mario@bc.ufrpe.br) on 2018-08-14T12:38:57Z No. of bitstreams: 1 Cybelle Lais Souto Maior Sales de Melo.pdf: 1701463 bytes, checksum: 4dffd75db6cbeb936380aad9ca10f778 (MD5) / Made available in DSpace on 2018-08-14T12:38:57Z (GMT). No. of bitstreams: 1 Cybelle Lais Souto Maior Sales de Melo.pdf: 1701463 bytes, checksum: 4dffd75db6cbeb936380aad9ca10f778 (MD5) Previous issue date: 2016-08-31 / Among the dry tropical forest in the world, the caatinga stands out for being one of the most modified environment, where an enormous portion of its vegetation is replaced by farming activities or cattle grazing, rendering these present studies of the remaining flora relevant, aiming to understand its answer when it is submitted to dry seasons and anthropic actions specially when discussion is about its structure and dynamics. Therefore, this present study had as objective analyses the dynamics of individuals of shrub-arboreal species and its natural regeneration into anthropized caatinga area, at Floresta, in Pernambuco, Brazil. For data collection, the individuals were measured within 2011, 2013 and 2015, for results comparison the data ware arranged accordingly the following periods 2011-2013 and 2013-2015. The arrays of adults individuals/boles were made with 40 permanent plots of 20 x 20 m and for the regenerates were done with a 40 sub-plots of 5 x 5 m. Phytosociological parameters of horizontal structures and natural regeneration were estimated as well as the diversity and equability, mortality rate and ingrowth, gross and liquid growth, periodic annual increment of diameter and basal area and diametric distribution analysis. The individuals number and bole of shrub-arboreal species decreased from 2011 to 2015 (p < 0.01), otherwise, the basal area as similar (p ≥ 0.01). The Poincianella bracteosa overcame in terms of density, frequency and dominance of boles and individuals. The number of regenerates species into the area also decreased, showing the tough establishment of young plants linked with the long drought period. The Croton blanchetianus had the most highlight in natural regeneration. The mortality rate overcame the individuals ingrowth in 7.82 and 8.81%, between 2011-2013 and 2013-2015, respectively, but for boles the overcome was 0.82 and 3.97%. Regarding the growth, the species had small gross and liquid growth, negative in some cases, due the high mortality rate as well long drought period when the system was studied, causing a reduction over the periods 2011-2013 and 2013-2015, of individuals and their boles. The annual periodic increment of individuals and their boles also where insignificant between 2013-2015, likewise the growth, this variation might be a part of the elevated mortality rate, climate condition and uncontrolled goat breeding. Between 2011 and 2015, the diametric distribution of the community and P. bracteosa, were not similar, most due to the mortality rate higher than the ingrowth, specially in first class or advances between classes. This group had observed an imbalance of diametric distribution for the community as well for the P. bracteosa specially in 2011. The composition and floristic diversity of suppressed vegetation 29 years ago, are found within existed values for others preserved caatinga areas, but in the period of study the species had difficulty regeneration. The adult communities and regenerates, as well their species, exhibit more evidenced structural and phytosociological changes when a four year interval is considered. The extensive drought period was the main disturbance factor which affect the vegetation dynamic. / Dentre as florestas tropicais secas do mundo, a caatinga se destaca por ser um dos ambientes mais modificados, com grande parte da vegetação substituída por cultivo agrícola ou pastagem, tornando importante os estudos nos remanescentes existentes, visando o entendimento de suas respostas quando submetidas a ações antrópicas e a períodos de seca, especialmente quanto a sua estrutura e dinâmica. Desta forma, este trabalho teve como objetivo analisar a dinâmica de indivíduos de espécies arbustivo-arbóreas e de sua regeneração natural em área de caatinga antropizada, no município de Floresta, Pernambuco, Brasil. Para o levantamento dos dados, foram medidos os indivíduos nos anos 2011, 2013 e 2015 visando à comparação de resultados considerando os períodos 2011-2013 e 2013-2015. Para amostragem foram utilizadas 40 parcelas permanentes de 20 x 20 m, para estudo dos indivíduos/fustes adultos e 40 sub-parcelas de 5 x 5 m para o dos regenerantes. Foram estimados parâmetros fitossociológicos das estruturas horizontal e da regeneração; diversidade e equabilidade; taxas de mortalidade e ingressos; crescimentos bruto e líquido; incrementos periódicos anuais em diâmetro e área basal, bem como realizada a análise de distribuição diamétrica. No componente arbustivo-arbóreo, o número de indivíduos e de fustes diminuiram de 2011 para 2015 (p < 0,01), no entanto, a área basal foi similar (p ≥ 0,01). A Poincianella bracteosa se sobressaiu em termos de densidade, frequência e dominância de indivíduos e fustes. O número de indivíduos regenerantes na área também diminuiu, demonstrando a dificuldade de estabelecimento de plantas jovens, associada ao longo período de estiagem. A Croton blanchetianus apresentou maior destaque na regeneração natural. A taxa de mortalidade superou a taxa de indivíduos ingressos em 7,82 e 8,81%, nos períodos 2011-2013 e 2013-2015, já para fuste superou a de ingresso em 0,82 e 3,97%. Em relação ao crescimento, foi verificado que as espécies tiveram pequenos crescimento bruto e líquido, e alguns casos negativos, resultante da elevada mortalidade, bem como do longo período de estiagem no tempo estudado, que acarretaram na diminuição nos intervalos de 2011-2013 e 2013-2015, tanto dos indivíduos quanto de seus fustes. Os incrementos periódicos anuais de indivíduos e de seus fustes também foram menores entre 2013-2015, essa variação também ocorreu por causa da alta mortalidade, das condições climáticas e do pastejo de caprinos não controlado. As distribuições diamétricas da comunidade e da P. bracteosa, não foram similares entre 2011 e 2015 (p < 0,01), devido a taxa de mortalidade superior à de ingressos, especialmente na primeira classe, ou aos avanços entre classes. Observou-se desequilíbrio da distribuição diamétrica, tanto para a comunidade quanto para a P. bracteosa, especialmente no ano de 2011. A composição e a diversidade florística da vegetação suprimida há 29 anos se encontram dentre valores existentes para outras áreas de caatinga preservada, porém no período estudado houve dificuldade de regeneração das espécies. As comunidades de adultos e de regenerantes, bem como suas espécies, apresentaram mudanças estruturais e fitossociológicas mais evidenciadas quando considerado um intervalo de 4 anos. O período de estiagem prolongada foi o principal fator de distúrbio a afetar a dinâmica da vegetação.

La question de l’accès à l’eau potable se pose avec acuité pour les pays de la régionsubsaharienne où un individu sur trois n’a pas accès à une source d’eau améliorée.L’objectif de cette thèse vise à définir les conditions d’une gestion durable de l'eau pourla ville de Djibouti. Dans ce contexte, la question de l'approvisionnement en eau estenvisagée dans une perspective patrimoniale afin de tenir compte des particularités dela ressource en zone aride et des usages spécifiques qui lui sont associés dans unenvironnement marqué par la pauvreté. Un apport majeur de la thèse réside d'une partdans l’analyse du contenu d’une politique durable de l'eau à Djibouti en présenced’inadéquation entre l’offre et la demande de l’eau et, d'autre part, des implications decette politique en termes de tarification de la ressource selon les usages mais aussi enterme de répartition plus équitable de l'eau au sein de la population. La première partiede la thèse s’intéresse à l’étude de la disponibilité de cette ressource rare à travers sonmode de gestion ainsi qu’à sa mesure à l’aide d’indicateurs. Elle propose également uncadre d’analyse de la ressource en resituant les principaux concepts utiles à ladéfinition d’une gestion durable de l’eau. La seconde partie met l’accent sur l’analysedes déterminants de la demande en eau et des choix en matière d’approvisionnementpour Djibouti-ville. Pour ce faire, elle s’appuie sur une étude économétrique réalisée àpartir d’enquêtes auprès d’un échantillon de 400 ménages. L’estimation d’un modèleprobit multivarié permet de considérer que le choix d’être raccordé à un branchement àdomicile dépend des caractéristiques socio-économiques du ménage. Cette thèseapporte des résultats originaux sur l’accès à l’eau des ménages et montre en particulierle rôle joué par des facteurs tels que le revenu, la taille de la famille ou le niveaud’éducation du chef de famille dans les choix opérés par les ménages. / The issue of access to drinking water is one which is of paramount importance for thecountries of the sub-Saharan region where one individual out of three does not haveaccess to a water source. The aim of this thesis is to determine the conditions ofsustainable water management for the city of Djibouti. In this context, the issue ofwater supply is considered from an asset perspective in order to take into considerationthe peculiarities of this resource in a dry zone and its uses in particular in anenvironment marked by poverty. The main contribution of this thesis lies not only inthe analysis of the content of a sustainable water policy in Djibouti at a time when isthere is discrepancy between supply and demand, but also with an examination of theimplications of such a policy in terms of the pricing of this resource based on both itslevel of use and on a more even distribution within the population. The first part of thisthesis deals with an analysis of the access to this scarce resource according to how it ismanaged and measured with the help of indicators. A framework is then developedwith the help of some main concepts that are useful for defining a sustainablemanagement of water. The second part emphasizes the study of the determinants ofdemands in water and the choices in terms of the supply for Djibouti-city by using aneconometric study based on investigations into a sample of 400 households. Theassessment of multivariate probit model allows taking into account the connection of ahousehold to the service depends on its socio-economic markers. This thesis generatenew findings about household access to water supply and highlights the extent towhich such factor as income, the household size or the level of education of the head ofthe family influence the choices made by the household.

The critical zone (CZ) is the heterogeneous, near-surface layer of the planet that regulates life-sustaining resources. Previous research has demonstrated that a quantification of the influxes of effective energy and mass transfer (EEMT) to the CZ can predict its structure and function. In this study, we quantify how climate variability in the last 3 decades (1984–2012) has affected water availability and the temporal trends in EEMT. This study takes place in the 1200 km² upper Jemez River basin in northern New Mexico. The analysis of climate, water availability, and EEMT was based on records from two high-elevation SNOTEL stations, PRISM data, catchment-scale discharge, and satellite-derived net primary productivity (MODIS). Results from this study indicated a decreasing trend in water availability, a reduction in forest productivity (4 g C m⁻² per 10 mm of reduction in precipitation), and decreasing EEMT (1.2–1.3 MJ m² decade⁻¹). Although we do not know the timescales of CZ change, these results suggest an upward migration of CZ/ecosystem structure on the order of 100 m decade⁻¹, and that decadal-scale differences in EEMT are similar to the differences between convergent/hydrologically subsidized and planar/divergent landscapes, which have been shown to be very different in vegetation and CZ structure.

To achieve water resource sustainability in the water-limited southwestern US, it is critical to understand the potential effects of proposed forest thinning on the hydrology of semi-arid basins, where disturbances to headwater catchments can cause significant changes in the local water balance components and basinwise streamflows. In Arizona, the Four Forest Restoration Initiative (4FRI) is being developed with the goal of restoring 2.4 million acres of ponderosa pine along the Mogollon Rim. Using the physically based, spatially distributed triangulated irregular network (TIN)-based Real-time Integrated Basin Simulator (tRIBS) model, we examine the potential impacts of the 4FRI on the hydrology of Tonto Creek, a basin in the Verde–Tonto–Salt (VTS) system, which provides much of the water supply for the Phoenix metropolitan area. Long-term (20-year) simulations indicate that forest removal can trigger significant shifts in the spatiotemporal patterns of various hydrological components, causing increases in net radiation, surface temperature, wind speed, soil evaporation, groundwater recharge and runoff, at the expense of reductions in interception and shading, transpiration, vadose zone moisture and snow water equivalent, with south-facing slopes being more susceptible to enhanced atmospheric losses. The net effect will likely be increases in mean and maximum streamflow, particularly during El Niño events and the winter months, and chiefly for those scenarios in which soil hydraulic conductivity has been significantly reduced due to thinning operations. In this particular climate, forest thinning can lead to net loss of surface water storage by vegetation and snowpack, increasing the vulnerability of ecosystems and populations to larger and more frequent hydrologic extreme conditions on these semi-arid systems.

This thesis demonstrates achieving a net-zero energy commercial building in the hot, arid region of Saudi Arabia. The development process uses three main concepts: evaluating and assessing selected existing commercial buildings, incorporating energy efficiency strategies, and implementing renewable energy source technologies. This study has been divided into five chapters: Introduction and Problem Statement, The Net-Zero Approach, Background of Saudi Arabia and Its Climatic Variations, Case Studies, and Project Development and Demonstration. Initially, an assessment of the Umm Al-Qura University administration building was conducted in two steps: 1) collecting building data and creating a building simulation in eQUEST software to obtain accurate performance prediction results and 2) implementing energy efficient strategies for both passive and active systems to mitigate energy use in commercial buildings located in hot, arid climates. Finally, embracing renewable energy sources through adopting Photovoltaic (PV) Panels will meet remaining energy needs after energy efficiency strategies have been applied. To summarize, the main focus is on designing energy efficiency strategies rather than focusing on technologies. After conducting this research, the following results were achieved in the simulation and calculation: 1. The energy savings were beyond expectation at 150,036 kWh in remaining energy. 2. A utility bill savings of more than half the cost of building operations. 3. The simple payback on the entire solar panel system for the proposed design will be approximately 3.3 years.

Riparian Zones are considered biodiversity and ecosystem services hotspots. In arid environments, these ecosystems represent key habitats, since water availability makes them unique in terms of fauna, flora and ecological processes. Simple yet powerful remote sensing techniques were used to assess how spatial and temporal land cover dynamics, and water depth reflect distribution of key land cover types in riparian areas. Our study area includes the San Miguel and Zanjon rivers in Northwest Mexico. We used a supervised classification and regression tree (CART) algorithm to produce thematic classifications (with accuracies higher than 78%) for 1993, 2002 and 2011 using Landsat TM scenes. Our results suggest a decline in agriculture (32.5% area decrease) and cultivated grasslands (21.1% area decrease) from 1993 to 2011 in the study area. We found constant fluctuation between adjacent land cover classes and riparian habitat. We also found that water depth restricts Riparian Vegetation distribution but not agricultural lands or induced grasslands. Using remote sensing combined with spatial analysis, we were able to reach a better understanding of how riparian habitats are being modified in arid environments and how they have changed through time.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Doctor of Philosophy, 2017 / Plant phenology, the study of the timing of biological events such as leaf flush, has been identified as a key tool in monitoring and understanding the impacts that changing climates may have on the world. Unfortunately there is a noticeable lack of phenological research in Africa’s savannas in comparison to other global ecosystems, such as temperate forests. Savannas are known for their complexity in structure and composition and the phenology of their flora is no exception to this. Owing to the highly seasonal climates in this system, plants have had to evolve a range of phenological strategies to cope with the limited window of suitable growth conditions during the periodic wet season in the austral summer. One of these phenological strategies is that of early-greening; where deciduous trees will produce new flush prior to the onset of seasonal rainfall when the environmental conditions are at their driest. There is likely no other ecosystem in the world where the early-greening phenomenon occurs, however, it has been recorded in savannas from Africa, Australia, Asia and South America. The global prevalence of this strategy suggests that early-greening trees must gain some benefit from utilising this seemingly risky leaf flushing strategy. The main aim of this study was to investigate two of the hypothesised benefits of an earlygreening strategy for semi-arid savanna trees. The first hypothesis suggested that earlygreeners are extending their growing season beyond that of grasses and late-greeners – whose leaf flush is limited by the availability of water through the onset of seasonal rainfall. The second hypothesis is that early-greeners produce new leaves ahead of the emergence of invertebrate herbivores with the onset of the first rains, therefore decreasing the risk of damage to the vulnerable tissues and allowing the defence mechanisms within/upon the leaf to develop. This study took place in the Nylsvley Nature Reserve (NNR) over three consecutive austral growing seasons (August 2012 to April 2015) and was conducted on the two dominant deciduous broad-leaved trees: Burkea africana and Terminalia sericea. Burkea africana is known to flush prior to the onset of seasonal rainfall and was considered the earlygreening species in this study. Terminalia sericea has been recorded as flushing leaves prior to the onset of rainfall, but is more often a facultative-greener – rapidly producing new leaves with the onset of seasonal rainfall. This study experienced high seasonal variability between years with early-greening only occurring during the final (2014-2015) season. Nevertheless, I was able to assess the weekly green-up phenology of both species during the first three months of green-up and found that the green-up of the trees was largely disconnected from the main system driver – water – while grass green-up was closely linked to the onset of rainfall. This complements the theory of temporal niche separation; however, when assessing the functionality of the new leaves produced, carbon gain only occurred after the first two weeks post bud-break. In a system such as the NNR where rainfall onset variability is high, trees will only gain the advantage of an extended growing season if the onset of rainfall is more than two weeks after the start of flush. Using historical rainfall records (1980-2014), I estimated that 46% of years could have potentially experienced early-greening with rainfall commencing after the 15th October – the earliest date of green-up prior to rainfall onset in the NNR during this study. One of the benefits tested relating to early-greening in this study was that early-greeners avoid invertebrate herbivore damage on vulnerable new leaves. This study provided evidence for the use of a phenological defence strategy to cope with invertebrate herbivory pressure. Leaves which emerged before the rains had lower rates of herbivore damage than those which emerged after. Moreover, it was demonstrated that the constant turnover of leaves with high photosynthetic rates (T. sericea) is a reasonable mechanism for dealing with high leaf herbivory, and can result in equivalent end of season leaf area (and carbon gain) to species which invest in defence and have slower turnover rates (B. africana). Using the ground-based phenological measures in conjunction with remotely sensed NDVI imagery, the frequency of early-greening across seven comparable broad-leaved woodland sites in southern Africa from 2002 to 2014 was quantified. Of the environmental variables considered, the predictability of early-season rain (rather than total rainfall amount) was best correlated with early-greening. In savannas where rainfall onset and annual amounts were highly variable (such as the NNR), early-greening was less frequent (20% of the years) while in savannas closer to the equator where rainfall amounts were consistently >900 mm per annum and the onset dates began within a two week window each season, early-greening occurred in 80-90% of all years. The decrease in the proportion of early-greening events in the NNR from the 1980s to the past decade could be driven by the changing rainfall regimes over South Africa – with a predicted decrease in the number of precipitation events, but an increase in the storm intensity and rainfall amounts in each of these events. Fewer precipitation events may increase the risks associated with the early-greening strategy and this may be driving the NNR trees to use this strategy less frequently. This study has highlighted the need for a long-term phenological monitoring network within southern Africa’s savannas and has illustrated how early-greening species can benefit over other flora when environmental conditions are suitable for them to commence early leaf flush. This thesis has shown that early-greening broad-leaved savannas trees in South African savannas are more likely to avoid invertebrate herbivory than extend their growing seasons. / XL2017

Remotely sensed data can be used as an alternative to ground based observations to predict river discharge and water storage variability. The latter dataset used consists of meteorological records from four stations (2003-2014) and daily river discharge records from one stations (2010-2014). A model was developed named ‘Leicester Model for Semi-Arid Region’ (LEMSAR). It was applied in the semi-arid Kurdistan region of Northern Iraq. TRMM Multi-satellite Precipitation Analysis (TMPA) data products (TMPA 3B42 and 3B42RT) were used with and without a bias correction. The uncorrected TMPA underestimated observed mean catchment rainfall by 10% compared to corrected data with 0.7%. Four methods of computing reference evapotranspiration (ETₒ) were applied which include Hargreaves-Samani (HS), Jensen-Haise (JH), McGuinness-Bordne(MB) and FAO Penman Monteith(PM). The variables utilised are air temperature, relative humidity and cloud cover fraction from the Atmospheric Infrared Sounder / Advanced Microwave Sounding (AIRS/AMSU), and wind speed at 10 m height from MERRA (Modern-Era Retrospective Analysis for Research and Application). Compared to ETₒ-G (PM), ETₒ-RS (HS) underestimated ETₒ-G (PM) by 3% while JH and MB overestimated by 8% to 40% at different stations. Nash-Sutcliffe Efficiency (NSE) for the LEMSAR fit with the observed hydrograph was 0.75, for a calibration period (2010-2011) using gauged rainfall data with ETₒ-G (PM). Model validation performance (2012–2014) was best (NSE =0.61) using the corrected 3B42 data with ETₒ-RS HS and poorest when driven by uncorrected 3B42RT data with ETₒ-RS JH (NSE =0.07). Data from the Gravity Recovery and Climate Experiment (GRACE: 2003-2014) were used to evaluate total water storage variability and compared with that of well observations data and LEMSAR. Trends in GRACE_TWSA were approximately -33.72 mm y-1 for the Lesser Zab catchment and -35.4 mm y-1 for the Hawler well monitoring zone while LEMSAR predicted 15 mm y-1 for the Lesser Zab Catchment. This suggest that reduction in recharge (modelled by LEMSAR) may only be responsible for about 50% of the reduction in groundwater storage. The rest could be the result of increased abstraction in response to the drought. Overall, results suggest that RS data can be usefully employed to simulate river discharge and to evaluate terrestrial water storage variability in semi-arid areas. It has the potential to help decision-makers improve water resources management.