Species-species and species-habitat interactions have been demonstrated to be important in influencing diversity across a variety of ecosystems. Despite generalities in the importance of these interactions, appropriate mechanisms to explain them are absent in many systems. In sandhill systems of the southeast U.S., gopher tortoises have been hypothesized to be a crucial species in the maintenance of diversity and function. However, the mechanisms and magnitude in which they influence their communities and habitats have rarely been empirically quantified. I examined how habitat structure influences tortoise abandonment of burrows and how tortoise densities influence nonvolant vertebrate community diversity. Tortoise burrow abandonment is directly influenced by canopy closure, with each percent increase in canopy cover relating to a ~2% increase in the probability of burrow abandonment. In addition, tortoise burrow density was positively correlated with diversity and evenness, but not species richness. This influence was directly proportional to burrow density, supporting a dominance role for this species and rejecting the commonly asserted keystone species mechanism. I also quantified the influence of tortoises in influencing diversity relative to other environmental and habitat variables. Through this research, I have demonstrated that disturbance and habitat structure are important, but diversity responds most to density of burrows in the habitat. These findings demonstrate the intricate relationships interacting to maintaining diversity in sandhill systems. In particular, habitat change leading to declines of gopher tortoises may have drastic negative impacts on vertebrate species diversity.

No description available.

No description available.

Cavity-nesting communities are structured by the creation of and competition for cavities as nest-sites. Viewing these communities as interconnected webs can help identify species interactions that influence community structure. This study examines cavity-nesting bird community interactions within the fire-maintained longleaf pine (Pinus palustris) ecosystem at Eglin Air Force Base, Florida. In chapter 1, I provide a background review of the ecology of my study system. In chapter 2, I use nest webs to depict the flow of cavity-creation and use at Eglin. I identified 2 webs into which most species could be placed. One web contained 6 species associated with pines. The second web contained 5 species associated with hardwoods. Red-cockaded woodpeckers (Picoides borealis) and northern flickers (Colaptes auratus) created most cavities used by other species within this community. In chapter 3, I describe snag densities and nest-site selection of the cavity-nesting bird community at Eglin. Large, mature pine snags were abundant, exceeding other reported densities for southern pine forests. Pine snags were heavily-used, despite the abundance of available red-cockaded woodpecker cavities in living pine. Hardwood snags accounted for 10% of nests found, and were used by 12 of 14 species. Diameters of nest-trees and available snags were below the range of optimal nest-snag diameters reported in other studies, indicating the need for site-specific snag management guidelines. In chapter 4, I combine a study of basic ecological principles with endangered species management to examine interactions within the cavity-nesting bird community at Eglin. I used a nest web to identify a potential indirect interaction between the red-cockaded woodpecker and large secondary cavity-nesters, mediated by the northern flicker. I used structural equation modeling to test a path model of this interaction. By experimentally manipulating cavity availability, I blocked links described in the model, confirming cavity creation and enlargement as mechanisms that influence this indirect relationship. I demonstrated that a red-cockaded woodpecker cavity-management technique could disrupt this indirect relationship by affecting northern flicker behavior, and provided an empirical example of how, in interactive ecological communities, single-species management can have indirect effects on non-target species. / Ph. D.

Abstract This thesis focuses on two important challenges in wireless downlink transmission: multi-user (MU) precoder design and scheduling of users over time, frequency, and spatial resources at any given instant. Data streams intended for different users are transmitted by a multiple-input multiple-output (MIMO) multi-antenna orthogonal frequency division multiplexing (OFDM) system. The transmit precoders are designed jointly across space-frequency resources to minimize the number of backlogged packets waiting at the coordinating base stations (BSs), thereby implicitly performing user scheduling. Then the problem of multicast beamformer design is considered wherein a subset of users belonging to a multicasting group are served by a common group-specific data. The design objective is to either minimize the transmit power for a guaranteed quality-of-service, or to maximize the minimum achievable rate among users for a given transmit power. Unlike existing techniques, the proposed design utilizes both the spatial and frequency resources jointly while designing multi-group beamformers. As an extension to coordinated precoding, the problem of beamformer design for cloud radio access network is considered wherein beamformers are designed centrally, quantized and sent along with data to the respective BSs via backhaul. Since the users can be served by multiple BSs, beamformer design becomes a nonconvex combinatorial problem. Unlike existing solutions, beamformer overhead is also included in the backhaul utilization along with the associated data. As the number of antennas increases, backhaul utilization is dominated by the beamformers. Thus, to reduce the overhead, two techniques are proposed: varying the quantization precision, and reducing the number of active antennas used for transmission. Finally, to reduce the complexity involved in the design of joint space- frequency approach, a two-step procedure is proposed, where a MU-MIMO scheduling algorithm is employed to find a subset of users for each scheduling block. The precoders are then designed only for the chosen users, thus reducing the complexity without compromising much on the throughput. In contrast to the null-space-based existing techniques, a low-complexity scheduling algorithm is proposed based on vector projections. The real-time performance of all the schedulers are evaluated by implementing them on both Xilinx ZYNQ-ZC702 system-on-chip (SoC) and TI TCI6636K2H multi-core SoC. / Tiivistelmä Tässä väitöskirjassa keskitytään kahteen tärkeään langattoman tiedonsiirron haasteeseen alalinkkilähetyksissä: usean käyttäjän (MU) esikooderisuunnitteluun ja käyttäjien skedulointiin aika-, taajuus- ja tilaresurssien yli. Eri käyttäjille tarkoitettuja datavirtoja lähetetään käyttämällä monitulo-monilähtötekniikkaa (MIMO) yhdistettynä monikantoaaltomodulointiin (OFDM). Lähettimien esikooderit suunnitellaan yhteisesti tila- ja taajuusresurssien yli, jotta keskenään yhteistoiminnallisten tukiasemien jonossa olevien pakettien määrää voitaisiin minimoida samalla kun tehdään epäsuorasti käyttäjien skedulointia. Tämän jälkeen työssä paneudutaan monilähetysten (multicast) keilanmuodostussuunnitteluun, jossa monilähetysryhmään kuuluvien käyttäjien alijoukolle lähetetään yhteistä ryhmäspesifistä dataa. Suunnittelun päämääränä on joko minimoida kokonaislähetysteho tietyllä palvelunlaatuvaatimuksella tai maksimoida pienin saavutettavissa oleva siirtonopeus käyttäjien joukossa tietyllä lähetysteholla. Toisin kuin olemassa olevat menetelmät, ehdotetussa mallissa käytetään yhteisesti sekä aika- että taajuusresursseja usean ryhmän keilanmuodostusta suunniteltaessa. Laajennuksena yhteistoiminnalliselle esikoodaukselle, väitöskirjassa käsitellään myös keilanmuodostusta pilvipohjaisessa radioliityntäverkkoarkkitehtuurissa. Keilanmuodostajat suunnitellaan keskitetysti, kvantisoidaan ja lähetetään datan mukana tukiasemille käyttäen runkoverkkoyhteyttä. Koska käyttäjiä voidaan palvella usealta tukiasemalta, keilanmuodostussuunnittelu muuttuu ei-konveksiksi kombinatoriseksi ongelmaksi. Toisin kuin olemassa olevissa ratkaisuissa, ehdotettu malli sisällyttää käyttäjien datan lisäksi keilanmuodostajien resursoinnin tarpeen runkoverkkoon. Tukiaseman antennien määrän lisääntyessä, keilanmuodostajien osuus runkoverkon käyttöasteesta kasvaa suureksi. Jotta keilanmuodostajien aiheuttamaa ylimääräistä tiedonsiirtotarvetta voitaisiin minimoida, esitellään kaksi tekniikkaa: kvantisointitarkkuuden muunteleminen sekä lähetykseen käytettävien aktiivisten antennien määrän vähentäminen. Lopuksi, jotta yhdistetyn tila-taajuussuunnittelun aiheuttamaa kompleksisuutta saataisiin vähennettyä, ehdotetaan kaksivaiheista menetelmää. MU-MIMO skedulointialgoritmin avulla etsitään ensin alijoukko käyttäjiä jokaiselle skedulointilohkolle. Esikooderit suunnitellaan vain valituille käyttäjille, mikä vähentää kompleksisuutta, heikentämättä suorituskykyä kuitenkaan olennaisesti. Poiketen nolla-avaruuteen perustuvista tekniikoista, esitetään yksinkertainen vektoriprojektioihin perustuva skeduleri. Kaikkien skedulerien reaaliaikasuorituskykyä on arvioitu toteuttamalla ne ohjelmoitavilla Xilinx ZYNQ-ZC702 system-on-chip (SoC) ja TI TCI6636K2H moniydinalustoilla.

No description available.

Cette thèse avait pour objectif principal d'approfondir nos connaissances sur l'écologie des différents types de milieux humides lacustres afin d'optimiser leur conservation. Pour ce faire, j’ai étudié la résilience, les fonctions et les services écologiques (FSE), ainsi que la biodiversité de trois types de milieux humides lacustres. Ces milieux humides sont riverains au lac Papineau, qui est situé dans la réserve naturelle de Kenauk Nature, entre les Laurentides et l’Outaouais. Cette thèse combine des approches globales, multifonctionnelles et ciblées, axées sur la conservation des milieux humides et de leur biodiversité. Dans mon premier chapitre, j'ai d’abord identifié les déterminants écologiques de la typologie des trois types de milieux humides étudiés : des tourbières, des aulnaies (marécages arbustifs) et des frênaies (marécages arborescents). À l’aide de données récoltées sur le terrain et de données cartographiques, j'ai quantifié 12 prédicteurs hydrogéomorphologiques (HGM) et j'ai pu identifier la pente et l'élévation comme étant les déterminants écologiques les plus importants. Mes résultats ont également apporté des nuances supplémentaires quant aux variables associées à chaque type de milieu humide. En utilisant ces 12 prédicteurs HGM, j'ai créé un modèle de forêts d’arbres décisionnels capable de prédire à la fois la présence des milieux humides lacustres et leur typologie. Ce modèle a permis de prédire avec une précision de 89 % la typologie des sites étudiés, ce qui en fait un outil intéressant pour étudier la répartition des milieux humides riverains à d'autres lacs. J'ai également utilisé ce modèle pour simuler différents scénarios de changements du niveau d'eau, mettant en évidence la résilience des tourbières et des aulnaies, ainsi que la vulnérabilité des frênaies, aux changements globaux. Dans mon second chapitre, j'ai quantifié huit FSE à l'aide de 25 indicateurs différents, dont 15 ont été quantifiés à partir de données terrain. J'ai ensuite développé une approche multifonctionnelle permettant d'étudier simultanément toutes les interactions de synergies et de compromis entre les indicateurs de FSE et les trois types de milieux humides. Mes résultats ont montré que chaque type de milieu humide maximise différentes FSE, mais que le choix des indicateurs influence considérablement les patrons de synergies et de compromis. Bien que certains types de milieux humides maximisent les mêmes FSE, ils le font à travers différents mécanismes écologiques. Enfin, la biodiversité floristique et faunique (plantes, oiseaux, poissons, zooplanctons et insectes chanteurs) présentait les patrons d'interaction les plus diversifiés, chaque type de milieu humide maximisant différents aspects de la biodiversité. Dans mon troisième chapitre, j'ai optimisé l'approche des espèces clés (keystone species) pour permettre son utilisation en conservation afin d’identifier les espèces indicatrices de la biodiversité. Pour cela, je me suis basée sur l’approche la plus récente proposée dans la littérature et j'ai identifié les éléments qui limitaient son utilisation pour les praticiens et les praticiennes. J'ai ensuite proposé des modifications pour surmonter ces limites. Ces modifications ont permis : 1) d'élargir l'utilisation de cette approche aux données d'inventaires terrain, 2) d'identifier les espèces ayant un impact négatif sur la biodiversité, et 3) de définir des seuils rigoureux pour identifier les espèces clés au sein d'une communauté. J'ai ensuite testé cette approche sur les communautés de plantes, d'oiseaux et de poissons des milieux humides échantillonnés dans le cadre de cette thèse. Mes résultats ont montré que cette approche permettait d'identifier des espèces possédant effectivement des caractéristiques écologiques expliquant leur importance dans l'augmentation ou la diminution de la biodiversité. Ensemble, les trois approches présentées dans cette thèse offrent une perspective intégratrice de la conservation des milieux humides lacustres. Les méthodes qui y sont proposées représentent des outils intéressants, qui ont le potentiel d’optimiser notre gestion du territoire à court et à long terme, mais aussi à petite et à grande échelle. / The main objective of this thesis was to deepen our understanding of the ecology of different types of lake-edge wetlands to optimize their conservation. To achieve this, I studied the resilience, the ecosystem functions and services (EFS), and the biodiversity of three types of lake-edge wetlands. All studies wetlands were riverine to Lake Papineau, which is located in a Kenauk Nature natural reserve, between the Laurentides and Outaouais regions. This thesis therefore combines a global, a multifunctional, and a targeted approach, all focused on wetland conservation. In my first chapter, I first identified the ecological determinants of the typology of the three types of wetlands studied: peatlands, alder swamps (shrub swamps), and ash swamps (trees swamps). Using both data collected on the field and map data, I quantified 12 hydrogeomorphological (HGM) predictors and identified slope and elevation as the most important ecological determinants. My results also provided additional nuances regarding the variables associated with each wetland type. Using these 12 HGM predictors, I then created a Random Forest model capable of predicting both the presence of lake-edge wetlands and their typology. This model predicted the typology of the studied sites with 89 % accuracy, making it an interesting tool to study the distribution of lake-edge wetlands along the shore of other lakes. I also used this model to simulate different scenarios of water level changes, highlighting the resilience of peatlands and alder swamps, as well as the vulnerability of ash swamps, to global changes. In my second chapter, I quantified eight EFS using 25 different indicators, with 15 indicators quantified using field data. I developed a multifunctional approach to simultaneously study all the synergies and trade-offs between the EFS indicators and the three wetland types. My results showed that each wetland type maximizes different EFS, and that the choice of indicators significantly influences the patterns of synergies and trade-offs. Although some wetland types maximized the same EFS, they do so through different ecological mechanisms. Finally, biodiversity exhibited the most diverse interaction patterns, with each wetland type maximizing different aspects of it. In my third chapter, I optimized the keystone species approach to allow its use in conservation to identify indicator species for biodiversity monitoring. To do so, I relied on the most recent approach proposed in the literature and identified the elements that limited its use for practitioners. I then proposed modifications to overcome these limitations. These modifications allowed 1) to expand the use of this approach to field inventory data, 2) to identify species that have a negative impact on biodiversity, and 3) to define rigorous thresholds to identify keystone species within a community. I then tested this approach on plant, bird, and fish communities in the wetlands sampled in this thesis. My results showed that this approach effectively identified species with ecological characteristics that explained their importance in increasing or decreasing biodiversity. Together, the three approaches presented in this thesis provide an integrative perspective on the conservation of lake-edge wetlands. The methods I propose represent interesting tools that have the potential to optimize land management in the short and long term, as well as at small and large scales.

South Africa’s growing elephant populations are concentrated in relatively small enclosed protected areas resulting in the over utilisation of the available food sources. Elephants and other herbivores as well as other natural disturbances such as fires and droughts play an important role in maintaining savannah environments. When these disturbances become too concentrated in a particular area the vegetation composition may be negatively affected. Excessive damage to the vegetation would result from exceeding the capacity of a protected area to provide food resources. The effect of the 120 elephants on the vegetation of Welgevonden Private Game Reserve, is not known. The rugged terrain of this reserve makes it a difficult, time consuming and labour intensive exercise to conduct ground studies. Satellite images can be used as a monitoring tool for vegetation change and improve the quantity and quality of environmental data to be collected significantly, allowing more informed management decision-making. This study evaluated the use of satellite imagery for monitoring elephant induced vegetation change on Welgevonden Private Game Reserve. The LANDSAT Thematic Mapper multispectral images, acquired at two yearly intervals from 1993 until 2007 were used. However, no suitable images were available for the years 1997, 2001 and 2003. A series of vegetation change maps was produced and the distribution of water sources and fire occurrences mapped. The areas of change were then correlated with the spatial distribution of water points and fire occurances, with uncorrelated areas of change. This was analysed using large animal population trends, weather data and management practices. On the visual comparison of the vegetation maps, it was seen that over this time period there was some decrease and thinning of woodland, but the most notable change was the increase of open woodland and decrease in grasslands. Using only the digital change detection for the period 1993 to 2007, a general increase in vegetation cover is seen. But this generalisation is misleading, since comparing the digital change detection to the vegetation maps indicates that while vegetation cover may have increased, significant changes occurred in the vegetation types. Most of the areas of significant change that were identified showed a strong positive correlation with burnt areas. The distribution of the water sources could not be directly linked to the vegetation change although rainfall fluctuations seemed to have accelerated vegetation changes. Years with high game counts, such as 1999, also coincide with very low rainfall making it difficult to differentiate between the effects of heavy utilisation of vegetation and low rainfall. Furthermore, many of the initial vegetation changes could be the result of land use changes due to the introduction of browsers, selective grazers and elephants that allow for more natural utilisation of the vegetation. Remote sensing makes it possible to successfully track changes in vegetation and identify areas of potential elephant induced vegetation change. Vegetation changes caused by disturbances, such as fire and anthropogenic activities, can be accounted for but it is not possible to conclude with a high level of certainty that the further changes seen are solely a result of elephant damage. Further work is required to reliably isolate elephant induced vegetation changes, as well as to establish the effects these changes have on the ecosystem as a whole. / Environmental Sciences / (M. Sc. (Environmetal Sciences))

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Climate has shown some remarkable changes over the past century, especially at the polar and sub-polar regions. Southern Ocean Islands provide good models for studies related to climate change effects, since effects may be evident in the short term and may also be clearer. Marion Island is an example of such a system with a harsh abiotic environment, and low species richness often vulnerable to change. Climate change is predicted, and also reported, to have biological consequences on plant communities, affecting the phenology, morphology, and the interaction between individuals and species. This study examines the association between the keystone plant species, Azorella selago Hook. (Apiaceace), and its dominant epiphyte Agrostis magellanica Lam. (Poaceae). Two complimentary approaches were used, one observational and the other experimental. The main objective for the observational study was to quantify bioticallyrelevant microclimate temperature, as well as the morphology, epiphyte load and phenology of A. selago at three different altitude sites on Marion Island. This provided information on baseline variation for understanding specific variability in plant response to the experimental part of this study, against which future patterns arising from biological monitoring can be compared. Studying plants at different altitudes provides a possible analogue for temperature-related climate change consequences for the ecology of A. selago, and its interaction with A. magellanica. The microclimate temperature associated with A. selago differed between the three sites examined. This difference was related to local topographic conditions and altitude differences. Cushion size differed distinctively between the three altitude sites, with this difference related to environmental heterogeneity such as differences in age and substrate structure. Azorella selago annual growth rate was estimated through stem length and the number of leaves on both exposed and shaded stems. Within-site variability, as well as epiphyte cover were found to be the contributing factors on A. selago annual growth rate. This highlights the importance of site-specificity when estimating growth rate within and between different altitude sites. Leaf characteristics differed between the sites, with this attributed to local habitat conditions, such as topography, as well as epiphyte cover. As expected, the difference in leaf size between exposed and shaded leaves demonstrated a larger specific leaf area on leaves shaded by A. magellanica. Agrostis magellanica abundance and density were altitudinally related, with A. selago demonstrating facilitation effects on A. magellanica. The trend shown in this study suggests that in spite of general facilitative effect of A. selago on A. magellanica towards higher altitudes, the abiotic environmental threshold for A. magellanica occurs at lower altitudes than it does for A. selago. Phenological differences were also apparent between the three sites. The objectives of the experimental part of this study were to quantify the effect of the dominant epiphyte, A. magellanica on biotically-relevant microclimatic temperatures, as well as on the phenology and physical condition of A. selago. Different treatments were applied to cushions at the three altitude sites to examine the shading effect of epiphytic A. magellanica on cushion plants, as well as the effect of treatment-related disturbance. Azorella selago microclimate temperature showed no significant difference between treatments, suggesting that on average epiphytic A. magellanica cover has no effect on cushion microclimate temperature. The percentage of flower budding and flowering of A. selago was negatively related to epiphyte cover. Cushion vitality was also responsive to epiphyte cover, with higher vitality scores on low grass covered cushions than on high grass cushions. This shows that A. magellanica competes with A. selago, while A. selago facilitates A. magellanica. Heavy epiphyte numbers impose negative effects on A. selago vegetative and reproductive performance, as well as cushion vitality. Therefore, the results of this research show that the vegetative and reproductive performance of A. selago and cushion vitality are likely to be negatively affected under ongoing climate change on Marion Island if this brings about heavier epiphyte loads on this keystone cushion plant species. / AFRIKAANSE OPSOMMING: In die afgelope eeu het die klimaat in die Antarktiese en sub-Antarktiese gebiede merkwaardige verandering getoon. Die Suidelike See Eilande dien as goeie modelle vir studies verwant aan die gevolge van klimaatsverandering, aangesien die kort termyn effekte in die gebiede duideliker mag wees in die toekoms. Marion Eiland is ‘n voorbeeld van so ‘n sisteem, met ‘n ruwe abiotiese omgewing en lae spesies rykheid, wat vatbaar is vir verandering. Daar word voorspel, en is reeds bevind dat klimaatsverandering biologiese gevolge op plant gemeenskappe het, in terme van morfologie, fenologie en die interaksie tussen individue en spesies. Hierdie studie ondersoek die assosiasie tussen die hoeksteen plant spesie, Azorella selago (Apiaceace), en sy dominante epifietiese gras, Agrostis magellanica Lam. (Poaceae). Die studie is op twee komplimentêre maniere benader, naamlik deur waarneming en eksperiment. Die hoof doel van die studie was om die biotiese belang van mikroklimaat temperatuur te kwantifiseer, en die hoeveelheid epifiete, die morfologie en die fenologie van A. selago te bepaal by drie verskillende hoogtes op Marion Eiland. Laasgenoemde het inligting verskaf oor die variasie in die reaksie van plante tot die eksperimentele aspek van die studie, waarteen patrone vanaf toekomstige biologiese beheer vergelyk kon word. Deur plante te bestudeer by verskillende hoogtes bo seespieël word ‘n moontlike analoog vir die gevolge van temperatuur-verwante klimaatverandering in terme van die ekologie van A. selago, en laasgenoemde se interaksie met A. magellanica verskaf. Die mikroklimaat temperatuur geassosieer met A. selago verskil tussen dié drie liggings. Die versil was verwant aan die plaaslike topografiese toestande en die verskillende hoogtes bo seespieël. Die grootte van die kussingplante het duidelik versil tussen die drie liggings, met die verskille verwant aan die omgewing se heterogeneïteit, byvoorbeeld die verskille in ouderdom en substraat struktuur. Azorella selago se jaarlikse groeitempo was bepaal deur die stingel lengte en die aantal blare, op beide die wat oorskadu is deur die gras, en die was nie oorskadu is nie. Daar is gevind dat die faktore wat bygedra het tot die jaarlikse groeitempo van A. selago, varieër binne die verskillende liggings, en bedekking deur epifiete. Dit beklemtoon die belang van spesifisiteit van ligging wanneer groeitempo in en tussen die liggings van verskillende hoogtes bepaal word. Die blaar eienskappe het verskil tussen verskillende liggings, as gevolg van plaaslike habitat toestande, soos topografie en bedekking deur epifiete. Soos verwag, het die blare wat oorskadu was deur A. magellanica ‘n groter spesifieke blaar area getoon as blare wat blootgestel was. Die hoeveelheid en digtheid van Agrosits magellanica was verwant aan hoogte bo seespieël, met A. selago wat fasiliterende effekte toon op A. magellanica. Die tendens waargeneem in hierdie studie is dat ten spyte van die algemene fasiliterende effek van A. selago op A. magellanica, die abiotiese omgewingsdrempel op ‘n laer hoogte is vir A. magellanica as vir A. selago. Fenologiese verskille was ook duidelik tussen die drie liggings. Die doel van die eksperimentele deel van die studie was om die effek van die dominante epifiet, A. magellanica, te bepaal op bioties relevante mikroklimaat temperature, asook op die fenologie en fiesiese toestand van A. selago. Verskeie behandelings is aangewend op die kussingplante by die drie liggings om die effek van skaduwee van die epifietiese A. magellanica op die plante te bepaal, asook die effek van versteurings versoorsaak deur die behandelings. Azorella selago se mikroklimaat temperatuur het geen betekenisvolle verskille tussen behandelings getoon nie, wat voorstel dat epifitiese A. magellanica oor die algemeen geen effek op die kussingplante se mikroklimaat temperatuur het nie. Daar was ‘n negatiewe verwantskap tussen die hoeveelheid epifiete op A. selago en die persentasie blomme en blomknoppe op die kussingplante. Die plante se vitaliteit was ook afhanklik van epifiet bedekking, met ‘n hoër vitaliteit telling vir kussingplante bedek met lae gras as die bedek met hoë gras. Dit toon dat A. magellanica met A. selago wedywer, terwyl A. selago vir A. magellanica fasiliteer. Hoë epifiet getalle het negatiewe effekte op A. selago se vegetatiewe en reproproduktiewe nakoming, asook die kussingplante se vitaliteit. Die resultate van hierdie studie toon dus dat die vegetatiewe en reproduktiewe nakoming van A. selago en kussingplant vitaliteit heel moontlik negatief geaffekteer sal word indien klimaatsverandering op Marion Eiland hoër epifiet getalle op die sleutel kussingplant spesie tot gevolg sal hê.

This thesis is a case study using paleoethnobotanical analysis of Kilgii Gwaay, a 10,700-year-old wet site in southern Haida Gwaii to explore the use of plants by ancestral Haida. The research investigated questions of early Holocene wood artifact technologies and other plant use before the large-scale arrival of western redcedar (Thuja plicata), a cultural keystone species for Haida in more recent times. The project relied on small-scale excavations and sampling from two main areas of the site: a hearth complex and an activity area at the edge of a paleopond. The archaeobotanical assemblage from these two areas yielded 23 plant taxa representing 14 families in the form of wood, charcoal, seeds, and additional plant macrofossils. A salmonberry and elderberry processing area suggests a seasonal summer occupation. Hemlock wedges and split spruce wood and roots show evidence for wood-splitting technology. The assemblage demonstrates potential for site interpretation based on archaeobotanical remains for the Northwest Coast of North America and highlights the importance of these otherwise relatively unknown plant resources from this early time period. / Graduate / cohenjenny2@gmail.com