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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Distribution des communautés végétales sous l'influence des lisières forestières dans des bois fragmentés / Distribution of vegetation communities under forest edge influence in fragmented forests

Alignier, Audrey 05 November 2010 (has links)
Les lisières forestières constituent un enjeu pour la gestion des territoires, par la biodiversité qu’elles abritent, les processus écologiques qu’elles régulent et les services environnementaux qu’elles rendent à l’agriculture et à la foresterie. C’est pourquoi il est nécessaire de connaitre et quantifier précisément leurs influences sur la végétation pour proposer des mesures de gestion adaptées à la variabilité des situations de lisière. En référence aux hypothèses de la littérature, ce travail vise à comprendre comment varie la répartition des communautés végétales forestières en réponse à la diversité des types de lisières, dans un paysage agriforestier. Les espèces vasculaires de la strate basse de la végétation forestière ont été recensées le long de 28 transects, représentatifs de sept types de lisières des coteaux de Gascogne. Ces transects, perpendiculaires à la bordure et dirigés vers l’intérieur du bois, comportent 20 quadrats contigus de 2 m × 2 m. J’ai cherché à mesurer la profondeur d’influence des effets de lisières sur la végétation par la méthode de régression à deux phases. Face à l’hétérogénéité observée, j’ai caractérisé les patrons de distribution des communautés végétales par cinq modèles continus pour les comparer. Les lisières structurent la répartition des communautés végétales suivant un gradient, de la bordure vers l’intérieur du bois, mais les patrons sont plus variables qu’attendus et remettent en cause la généricité du modèle théorique à deux phases largement admis dans la littérature. Néanmoins, un patron de distribution de la végétation commun à l’ensemble des lisières a été identifié au moyen de la méthode STATIS d’analyse à k-tableaux. L’analyse des effets de lisière sur un sous-échantillon d’espèces a été affinée par la prise en compte des caractéristiques biologiques et écologiques des espèces d’une part, et des variables environnementales, à différentes échelles spatio-temporelles d’autre part. Les traits biologiques et écologiques des espèces répondent davantage à l’âge et l’histoire des lisières qu’à la distance à la bordure. La hiérarchie des facteurs environnementaux, paysagers et historiques confirment le rôle prépondérant de la qualité locale de l’habitat dans la structure des communautés. La variabilité temporelle des effets de lisière a été abordée par un suivi horaire des variations microclimatiques au cours d’une année. Les faibles écarts microclimatiques entre la lisière et l’intérieur du bois au cours des saisons suggèrent un rôle faible du microclimat sur la structure des assemblages d’espèces. Enfin, la variabilité spatiale des lisières dans un paysage de large étendue a été évaluée par la mise au point d’une méthode originale afin de caractériser et cartographier la diversité des segments de lisières. Les résultats remettent en cause les modèles théoriques antérieurs et ouvrent des perspectives pour une meilleure compréhension des principes d’organisation des communautés végétales en lisières de forêt. La complexité des patrons de réponse aux effets de lisière justifie de porter une attention plus soutenue à la diversité des lisières dans la perspective de mieux les gérer. / Forest edges are a challenge for land management. They contain high biodiversity, regulate ecological processes and provide environmental services to agriculture and forestry. Therefore, it is necessary to evaluate and quantify precisely edge influence on vegetation to propose management measures adapted to edge diversity. Referring to the literature asusmptions, this paper focuses on understanding the variation in the distribution patterns of forest plant communities in response to contrasted edge types in rural landscape. All vascular plant species of the understorey forest vegetation have been identified along 28 transects, pertaining to seven edge types of “coteaux de Gascogne”. Transects were perpendicular to the forest border and included 20 contiguous quadrats of 2 m × 2 m, towards forest interior. I tried to measure the depth of edge influence on vegetation using the two-phase linear regression method. Facing to high heterogeneity, I characterized the distribution patterns of plant communities by five continuous models for comparison. Edge effect structure the distribution of plant communities along a gradient from the border toward the forest interior. Response patterns to edge influence were more variable than expected and challenge the hypothetical response model pattern widely accepted in the literature. However, a common pattern of vegetation for all transects was identified using the k-tables STATIS method. Analysis of edge effects on a sub-sample of species was refined using on the one hand biological and ecological species traits and environmental variables at different spatio-temporal scales, on the other. The functional response of plant species better suited to the age and history of the edges than the distance from the border. Nevertheless, the hierarchy of environmental, landscape and historical context confirm the role of habitat quality on distribution patterns of forest vegetation. Temporal variability of edge effects has been addressed by monitoring hourly microclimatic variations over one year. The small differences in microclimate between edge and forest interior over seasons suggest a weak role of microclimate on the structure of plant species assemblages. Finally, the spatial variability of edges at the landscape level has been evaluated. An original method, Cartolis, has been developed to characterize and map the diversity of forest edge segments. Our results, calling into question the earlier theoretical models, provide opportunities for a better understanding of plant distribution patterns in forest edges. The complexity of responses obtained warrants to bring more attention to edge diversity for better management and conservation of plant species.
12

Kantzoner utmed äldre och yngre granbestånd i västra Götaland och dess effekt på trädens höjd- och diametertillväxt samt markvegetationens artsammansättning / Forest edges between young and old Norway Spruce stands in south-western Sweden and its influence on tree growth and field vegetation

Nord, Mikael January 2015 (has links)
Det svenska skogsbruket har med fokus på beståndsvis avverkning och återbeskogning genererat ett mosaikartat landskap med en mängd väl avgränsande kantzoner mellan yngre och äldre bestånd, och att uppkomna förändringar hos växtmiljön i anslutning till dessa beståndsgränser kan påverka såväl tillväxt som artsammansättning har konstaterats i ett flertal tidigare studier. Men även om dessa studier påvisat förekomsten av kanteffekter har resultaten varierat utifrån geografiskt undersökningsområde och studerade trädslag. Tidigare studier har utifrån ett nordiskt perspektiv dessutom främst fokuserat på tillväxtförändringar hos tall i Finland och norra Sverige, vilket föranlett att denna studie valt att undersöka förekomst och omfattning av tillväxteffekter inom kantzoner belägna mellan angränsande äldre och yngre granbestånd i västra Götaland. Studien har genomförts genom att inom ett antal representativa objekt samla in data utifrån utlagda provyor i terrängen och undersökningen har avgränsats till att omfatta trädens höjd- och diametertillväxt samt markvegetationens artsammansättning. Vidare jämförelser har därefter gjorts utifrån avstånd från aktuell beståndsgräns, kantzonernas väderstreck i nordlig respektive sydlig riktning samt de yngre beståndens skötselhistorik i form av röjt eller oröjt. För att undersöka förekomsten av signifikanta skillnader mellan grupperna har insamlad data analyserats med hjälp av variansanalys (ANOVA) samt Tukey’s test för skillnader mellan medelvärden. Resultatet visade på signifikanta kanteffekter hos yngre granbestånd där tillväxtnedsättningarna var som tydligast närmast beståndsgränsen, oavsett väderstreck och tidigare skötselhistorik. Dessa tillväxtnedsättningar var dock mindre än de som tidigare konstaterats hos tall, och till skillnad från tidigare studier kunde inga tillväxteffekter konstateras hos angränsande äldre bestånd. Inga tydliga skillnader kunde heller konstateras utifrån kantzonernas väderstreck eller de yngre beståndens skötselhistorik. Markvegetationens artsammansättning uppvisade i sin tur en ökad förekomst av lavar och bärris intill beståndsgränserna. Bärris, lavar och ljung förekommer frekvent inom sydligt exponerade kantzoner medan smal- och bredbladigt gräs i sin tur uppvisade en ökad förekomst inom nordligt exponerade kantzoner. Utifrån dessa resultat skulle en tänkbar rekommendation inför kommande skogsbruksåtgärder och återbeskogning kunna vara att utifrån konstaterade tillväxtnedsättningar ej prioritera plantering av gran inom ett avstånd av 0-2,5 m från beståndsgräns angränsande mot äldre granbestånd. Därmed skulle kantzonen kunna nyttjas för naturvårdande ändamål då dessa områden gynnar den biologiska mångfalden och utgör intressanta miljöer för arter som annars skulle riskera att bli utkonkurrerade i angränsande mer slutna granskogsbestånd. / The aim of this study was to evaluate edge effects along forest edges between young and old Norway spruce stands in south-western Sweden, and examine its influence on tree growth and field vegetation. Comparison between distance from stand edge, exposure (north or south facing) and young forest clearing (cleared or not cleared) showed a reduced growth among young trees near the stand edge, mainly at a distance of 0-2,5 m. This edge effect occurred regardless of exposure or forest clearing history. On the other hand, in contrary to earlier studies, no positive growth effect was found in older stands adjacent to younger stands. Regarding edge effects found on field vegetation, blueberries, lingonberries and lichens showed an increased incidence adjacent to stand edges. Berries, lichens and heather showed an increased incidence at south facing edges while grass showed an increased incidence at north facing edges.
13

UNIDADES DE CONSERVAÇÃO COM FRONTEIRA AGRÍCOLA PODEM EVITAR INVASÕES? O CASO DA RÃ-TOURO NA MATA ATLÂNTICA DO SUL DO BRASIL

Madalozzo, Bruno 26 February 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Lithobates catesbeianus, the bullfrog is considered one of the 100 more prejudicial invasive species of the planet. Predictions based on climatic and topographic models showed atlantic forest biome regions of southern Brazil as favorable to invasive populations become established. Models that predict increase of temperature and gases concentration related with greenhouse effect, showed protected areas of the biome as propitious to invasion in the coming years. We conducted surveys at 36 waterbodies located in a protected area and anthropic adjacent locations through a forest-edge-farming gradient. We collected data on abundance and breeding to understand which the main descriptors (local and landscape) explained the bullfrog distribution. Our results showed that L. catesbeianus is mainly related with area-hidroperiod-deep gradient (local descriptors) and secondarily with environment gradient florest-edge-agriculture (landscape descriptors). Management strategies of aquatic invader populations as bullfrogs should focus both the management of landscape and waterbodies located at the edge. The supervision of large waterbodies (permanent or deep) construction in the park edge and adjacent areas can be effective, and the use of forest-agriculture management could be an important complement to prevent invasions. / Lithobates catesbeianus, a rã-touro, é considerada uma das 100 espécies invasoras mais prejudiciais do planeta. Predições com base em modelagens climáticas e topográficas evidenciam muitas regiões pertencentes ao bioma Mata Atlântica como favoráveis para o estabelecimento da espécie. Modelos que preveem o aumento de temperatura e maior concentração de gases ligados ao efeito estufa colocaram áreas protegidas do bioma como propícias à invasão nos próximos anos. Nós amostramos 36 corpos de água localizados em uma unidade de conservação e áreas agrícolas do entorno através de um gradiente floresta-borda-lavoura. Buscamos dados de abundância e indícios de reprodução de L. catesbeianus nesses locais para compreender quais os principais fatores locais e da paisagem que explicam a distribuição da espécie. Nossos dados demonstraram que a Lithobates catesbeianus responde principalmente ao gradiente área-hidroperíodo-profundidade (fatores locais) e de maneira secundária ao gradiente ambiental floresta borda-lavoura (fatores da paisagem). Estratégias de manejo de populações invasoras aquáticas como L. catesbeianus devem enfocar tanto no manejo da paisagem quanto em manejo dos corpos d água presentes na zona do entorno. A fiscalização da construção de corpos d água com grandes áreas (ou profundos e permanentes) nas bordas e áreas de entorno às unidades de conservação pode ser eficaz , sendo a utilização do manejo florestal-agrícola um complemento importante para evitar invasões.
14

The roles of forest fragments and an invasive shrub in structuring native bee communities and pollination services in intensive agricultural landscapes

Minnick, Michael John 07 February 2020 (has links)
No description available.
15

Quelle est la contribution des milieux semi-naturels à la diversité et la répartition des assemblages de Carabidae circulants et hivernants dans un paysage rural tempéré ? / What is the contribution of semi-natural habitats to the diversity and distribution of circulating and overwintering Carabidae in a temperate rural landscape ?

Roume, Anthony 09 June 2011 (has links)
Pour des raisons patrimoniales autant que pour les services qu'elle rend à l'humanité, il apparaît nécessaire de soutenir la diversité des organismes vivants et, pour cela, de connaître leur utilisation des milieux dans les paysages ruraux. En particulier, des travaux récents soutiennent un modèle de colonisation cyclique qui énonce qu'une partie des espèces circulant dans les milieux cultivés en été trouvent un abri propice à l'hivernation dans les milieux semi-naturels. Notre but était ici de mettre au jour les facteurs locaux et paysagers déterminant la répartition spatiale et la structure des assemblages de Carabidae dans un paysage rural des coteaux de Gascogne. Les patrons de répartition des Carabidae, obtenus à deux échelles spatiales différentes, celle du paysage et celle de la parcelle, et à deux moments clés de la vie de ces insectes, la période durant laquelle ils sont actifs (circulants) et la période d'hivernation, ont été interprétés en termes de processus écologiques grâce à la prise en compte des traits biologiques et écologiques des espèces de Carabidae. Les résultats montrent que le type de milieu a un effet structurant majeur sur les assemblages de Carabidae circulants comme hivernants, comparable aux effets des conditions environnementales locales et paysagères réunies. Par ailleurs, les effets de lisière sur les Carabidae circulants, au niveau des interfaces entre les bois et les cultures, sont limités à quelques mètres ou quelques dizaines de mètres. Concernant les Carabidae hivernants, nous avons noté de manière surprenante que leur densité était de deux à six fois plus élevée dans les marges (cultivées) des cultures que dans les milieux semi-naturels. De plus, nous n'avons noté aucun contraste de répartition spatiale entre les Carabidae hivernants et les Carabidae circulants, quels que soient les espèces ou les groupes fonctionnels considérés. Ceci indique donc que les marges des cultures sont des milieux d’hivernation très importants dans le contexte considéré et que si un mouvement de colonisation cyclique existe pour les Carabidae des cultures, il doit se dérouler entre leur zone intérieure et leur marge. L'ensemble de nos résultats soutient l'idée que si l'agencement spatial des milieux seminaturels dans le paysage est important pour promouvoir les populations de Carabidae auxiliaires dans les cultures, la gestion des cultures elles-mêmes, et notamment de leurs marges, est également de première importance. / Supporting biodiversity is an ethical as well as a practical issue since it provides numerous ecosystem services. In that purpose, it is necessary to determine how organisms use the different habitats in rural landscapes. In this view, recent studies suggest that a number of arthropods cyclically colonise cultures, where they feed and reproduce, and semi-natural areas, where they overwinter. We aimed to determine the local and landscape determinants of spatial distribution and structure of ground beetle (Coleoptera: Carabidae) assemblages in a rural landscape of south-western France. We studied spatial distribution patterns of ground beetles at landscape and habitat scales, and at two key periods of their life, that when they are active, and winter. We then considered biological and ecological traits to deduce from these spatial patterns ecological processes affecting ground beetles. Our results show that habitat type has a major effect on species assemblages of active (circulating) as well as overwintering ground beetles, equivalent to that of local conditions and landscape context combined. Edge effects on circulating ground beetles at the woodlot-filed interface were limited to a few meters or a few dozen of meters in both habitats. Amazingly, we found that the density of overwintering ground beetles was two-to six-fold higher in crop margins than in semi-natural habitats. Moreover, we failed to show any difference between the spatial distribution of overwintering ground beetles and circulating ground beetles, whatever the species or functional group considered. Crop margins are thus major overwintering sites in the context studied and cyclic colonisation of ground beetles in crops, if real, may take place between the inner zone and the margins of crops. These results suggest that, in addition to spatial arrangement of semi-natural habitats, crop management, and in particular management of crop margins, is important to promote ground beetles and their beneficial effects on crop protection in agro-forested landscapes.
16

Rôle de la diversité des arbres dans la régulation des populations d’insectes défoliateurs en forêts matures d’Europe / Tree diversity effect on insect herbivore regulation in european mature forests

Guyot, Virginie 18 September 2015 (has links)
Qui du phénomène de résistance (RA) ou de susceptibilité (SA) par association est prépondérant en milieu forestier ? En d’autres termes, la défoliation par les insectes herbivores est-elle moins (RA) ou plus (SA) importante sur des arbres hôtes situés en mélange comparés à des monocultures ? A cause des contraintes méthodologiques, les connaissances sur la relation diversité - résistance en forêts matures restent faibles. Pour répondre à cette question, nous avons utilisé le dispositif exploratoire du projet FunDivEUROPE. Sur un réseau de 209 parcelles forestières sélectionnées le long de deux gradients orthogonaux de richesse spécifique (d’une à cinq essences en mélange) et de latitude (de la forêt méditerranéenne à la boréale), nous avons évalué la défoliation des houppiers des arbres. A l’aide d’un échantillon constitué de onze essences différentes, nous avons démontré pour la première fois un patron global de diminution de l’herbivorie (RA) en forêts matures à travers l’Europe. Nous avons également comparé l’herbivorie des insectes dans des placettes constituées de chênes purs ou mélangés à d’autres espèces, placées en lisière ou à l’intérieur de petits bois présents dans les vallées et coteaux de Gascogne. Nous avons observé moins de dégâts foliaires sur les chênes entourés par des voisins hétérospécifiques, et nous avons montré que la magnitude de cette résistance (RA) était plus importante en lisière qu’à l’intérieur des bois. Enfin, nous avons testé cette hypothèse de RA sur une espèce d’herbivore invasif en Italie, le cynips du châtaignier. Basée sur la même approche méthodologique, notre étude a montré de plus faibles dégâts de galles sur les châtaigniers lorsque la richesse spécifique de la parcelle était élevée. Notre travail fournit donc de nouvelles preuves supportant l’hypothèse de RA à travers trois contributions originales : i) la RA existe en forêt mature, ii) quelle que soit l’espèce d’herbivore, iii) y compris sur des espèces exotiques. Ces résultats devraient avoir d’importantes implications pour la gestion des insectes herbivores en forêt puisque le maintien et l’amélioration de la diversité des essences représentent un outil prometteur pour prévenir les dégâts d’insectes. / Whether increasing forest diversity should result in less insect damage (Associational Resistance, AR) or more damage (Associational Susceptibility, AS) is still debated. Moreover little is known about the diversity - resistance relationships in mature forests due to methodological constraints. To answer this question we used the FundivEUROPE exploratory platform. In this network of 209 mature forest plots sampled along two orthogonal gradients of tree species richness (from one to five species mixtures) and latitude (from the Mediterranean to the boreal forest biomes), we assessed insect defoliation in tree crown. Focusing on eleven broadleaved species, we could for the first time demonstrate a global pattern of reduced defoliation (AR) in mature forests across Europe. We replicated the comparison of insect herbivory in pure vs. mixed plots of oak trees, at the edge or within forest patches of the valleys and hills of Gascony. Here we found significantly less damage on oaks surrounded by heterospecific neighbors, and showed that the magnitude of AR was larger at forest edge than in forest interiors. Last we tested the AR hypothesis with an invasive alien species, the Asian chestnut gall wasp, in Italy. Based on the same methodological approach, our study showed lower gall damage on chestnuts when tree species richness was higher in mixed mature stands. Our work therefore provide new evidences to support the AR hypothesis with three original contributions: i) AR does apply to mature forests, ii) irrespective of the identity of insect herbivores, iii) including exotic species. These findings may have important implications for pest management in forest since the maintenance or improvement of tree species diversity represent a promising tool to prevent insect damage.
17

Life on the Edge: Structural Analysis of Forest Edges to Aid Urban Management

Benjamin Zachary McCallister (11205411) 30 July 2021 (has links)
<div>The accelerating expansion of agricultural and urban areas fragments and degrades forests</div><div>and their capacity to provide essential ecosystem services while increasing physiological stress</div><div>and mortality rates of trees growing near forest edges. Previous studies have documented that</div><div>edges are hotter and drier than forest interiors and trees nearer the edge grow slower. However,</div><div>the physical structure of a forest’s canopy may serve to mitigate to these effects. This study</div><div>quantifies forest fragmentation across the Central Hardwoods Region (CHR; containing Missouri,</div><div>Illinois, and Indiana) and characterizes structural differences between the canopies of forest edges</div><div>and forest interiors. Importantly, we distinguish between edges that neighbor developed land and</div><div>agricultural lands since these landcover types may impose distinct effects on forest structure. We</div><div>characterized forest canopy structure in a subset of the CHR region using the 2016-2020 Indiana</div><div>3DEP Lidar Program data. Our findings indicate edge forest (forests within 30m of an edge) makes</div><div>up 29.8% of the total forest in our study extent, with urban and agricultural edges accounting for</div><div>17.8% and 72.8% of the edge edges in the region, respectively. Analysis of 15 separate structural</div><div>metrics derived from aerial laser scanning (ALS) showed no significant structural differences</div><div>between developed and agricultural edge canopies but did find differences between structure of</div><div>canopies in forest cores and those in forest edges of any kind. As developed and agricultural lands</div><div>increase so too will forest fragmentation and the creation of new forest edges. If there are no</div><div>significant differences between forest edge types, then we could begin to treat edges without</div><div>distinction. This could lead to simplified management practices for foresters and urban foresters</div><div>alike to protect and preserve forest fragments.</div>
18

At the edge : the north Prince Albert region of the Saskatchewan forest fringe to 1940

Massie, Merle Mary Muriel 18 January 2011
Canadians have developed a vocabulary of regionalism, a cultural shorthand that divides Canada into easily-described spaces: the Arctic, the Prairies, the Maritimes, and Central Canada, for example. But these artificial divisions obscure the history of edge places whose identity is drawn from more than one region. The region north of Prince Albert, Saskatchewan, is a place on the edge of the boreal forest whose self-representations, local history, and memorials draw heavily on a non-prairie identity. There, the past is associated with the forest in contrast to most Canadians' understanding of Saskatchewan as flat, treeless prairie. This dissertation presents the history of the north Prince Albert region within a framework that challenges common Saskatchewan and Canadian stereotypes. Through deep-time place history, layers of historical occupation in the study region can be compared and contrasted to show both change and continuity. Historical interpretations have consistently separated the history of Saskatchewans boreal north and prairie south, as if the two have no history of interchange and connection. Using edge theory, this dissertation argues that historical human occupation in the western interior found success in the combination of prairie and boreal lifeways.<p> First Nations groups from both boreal forest and open plain used the forest edge as a refuge, and to enhance resilience through access to resources from the other ecosystem. Newcomer use of the prairie landscape rebranded the boreal north as a place of natural resources to serve the burgeoning prairie market. The prairies could not be settled if there was not also a nearby and extensive source for what the prairies lacked: timber and fuel. Extensive timber harvesting led to deforestation and the rise of agriculture built on the rhetoric of mixed farming, not King Wheat. The mixed farming movement tied to landscape underscored the massive internal migrations from the open prairies to the parkland and forest edge.<p> Soldier settlement, long viewed as a failure, experienced success in the north Prince Albert region and gave a model for future extensive government-supported land settlement schemes. South-to-north migration during the 1920s was based on a combination of push and pull factors: drought in the Palliser Triangle; and a strengthening northern economy built on cordwood, commercial fishing, freighting, prospecting and fur harvesting, as well as mixed farming. The economy at the forest edge supported occupational pluralism, drawing subsistence from both farm and forest, reflecting the First Nations model. As tourism grew to prominence, the Saskatchewan dual identity of prairie/forest led to the re-creation of the north Prince Albert region as a new vacationland, the Playground of the Prairies. The northern forest edge drew thousands of migrants during the Great Depression. Historical analysis has consistently interpreted this movement as frantic, a reactionary idea without precedent. Through a deep-time analysis, the Depression migrations are viewed through a new lens. The forest edge was a historic place of both economic and cultural refuge and resilience predicated on the Saskatchewan contrast of north and south.
19

At the edge : the north Prince Albert region of the Saskatchewan forest fringe to 1940

Massie, Merle Mary Muriel 18 January 2011 (has links)
Canadians have developed a vocabulary of regionalism, a cultural shorthand that divides Canada into easily-described spaces: the Arctic, the Prairies, the Maritimes, and Central Canada, for example. But these artificial divisions obscure the history of edge places whose identity is drawn from more than one region. The region north of Prince Albert, Saskatchewan, is a place on the edge of the boreal forest whose self-representations, local history, and memorials draw heavily on a non-prairie identity. There, the past is associated with the forest in contrast to most Canadians' understanding of Saskatchewan as flat, treeless prairie. This dissertation presents the history of the north Prince Albert region within a framework that challenges common Saskatchewan and Canadian stereotypes. Through deep-time place history, layers of historical occupation in the study region can be compared and contrasted to show both change and continuity. Historical interpretations have consistently separated the history of Saskatchewans boreal north and prairie south, as if the two have no history of interchange and connection. Using edge theory, this dissertation argues that historical human occupation in the western interior found success in the combination of prairie and boreal lifeways.<p> First Nations groups from both boreal forest and open plain used the forest edge as a refuge, and to enhance resilience through access to resources from the other ecosystem. Newcomer use of the prairie landscape rebranded the boreal north as a place of natural resources to serve the burgeoning prairie market. The prairies could not be settled if there was not also a nearby and extensive source for what the prairies lacked: timber and fuel. Extensive timber harvesting led to deforestation and the rise of agriculture built on the rhetoric of mixed farming, not King Wheat. The mixed farming movement tied to landscape underscored the massive internal migrations from the open prairies to the parkland and forest edge.<p> Soldier settlement, long viewed as a failure, experienced success in the north Prince Albert region and gave a model for future extensive government-supported land settlement schemes. South-to-north migration during the 1920s was based on a combination of push and pull factors: drought in the Palliser Triangle; and a strengthening northern economy built on cordwood, commercial fishing, freighting, prospecting and fur harvesting, as well as mixed farming. The economy at the forest edge supported occupational pluralism, drawing subsistence from both farm and forest, reflecting the First Nations model. As tourism grew to prominence, the Saskatchewan dual identity of prairie/forest led to the re-creation of the north Prince Albert region as a new vacationland, the Playground of the Prairies. The northern forest edge drew thousands of migrants during the Great Depression. Historical analysis has consistently interpreted this movement as frantic, a reactionary idea without precedent. Through a deep-time analysis, the Depression migrations are viewed through a new lens. The forest edge was a historic place of both economic and cultural refuge and resilience predicated on the Saskatchewan contrast of north and south.
20

Small remnant habitats : Important structures in fragmented landscapes

Lindgren, Jessica January 2017 (has links)
The world-wide intensification of agriculture has led to a decline in species richness due to land use change, isolation, and fragmentation of natural and semi-natural habitats in agricultural and forestry landscapes. As a consequence, there is a current landscape management focus on the importance of green infrastructure to mitigate biodiversity decline and preserve ecosystem functions e.g. pollination services and pest control. Even though intensification in agriculture has been ongoing for several hundreds of years, remnant habitats from earlier management practices may still be remaining with a surprisingly high plant richness. Preserving these habitats could help conserving plant species richness in agricultural landscapes, as well as other organisms that are dependent on plants for food and shelter. In this thesis I focus on two small remnant habitats; midfield islets and borders between managed forest and crop field in southeastern Sweden. In the past, both habitats were included in the grazing system and therefore often still have remnant population of grassland specialist species left today. I have used these two remnant habitats as model habitats to investigate the effect of landscape factors and local factors on species richness of plants, flower morphologies and plants with fleshy fruits. Additively, I analysed the effect of surrounding landscape and local openness on the functions; pollination success, biological pest control of aphids and seed predation on midfield islets. One of my studies showed that spatial distribution and size of the habitat affected plant species richness. Larger habitat size and higher connectivity between habitats increased species richness of plants in the habitats. Openness of the habitats was shown to be an important factor to increase species richness and richness of flower morphologies, both on midfield islets and in forest borders. Even though midfield islets had the highest species and morphology richness, both habitat types are needed for habitat complementary as forest borders have more plants with fleshy fruits and a higher richness of plant species that flowers in spring/early summer. It was also shown that a more complex forest border, not just with gaps in the canopy, but also with high variation in tree stem sizes increases plant species richness in the field layer. The conclusion is that by managing small remnant habitats to remain or become more semi-open and complex in their structure, would increase species richness of plants, grassland specialist species, and flower morphologies. It would also increase some ecosystem functions as seed predation and biologic pest control of aphids are more effective close to trees. If both midfield islets and forest borders would be managed to be semi-open, the area and connectivity of semi-open habitat would increase in the agricultural landscape, which may also improve pollination success as the connectivity between populations has a possibility to increase. Grassland specialist species are clearly abundant in the small remnant habitats. As the decline of semi-natural grasslands is causing a decline in grassland specialists’ species, not only plants, I recommend that small remnant habitats are included in conservation and management plans and strategies to improve habitat availability and connectivity for grassland species in agricultural landscapes. / <p>Research funder Ekoklim. Project:4339602.</p><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

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