This paper deals with archery in the Viking Age settlement of Birka and in particular the presence of Euro Asiatic, steppe nomadic archery equipment at the Birka Garrison and one Birka grave. The equipment contains for example closed quivers and a bow case. This paper also contains a discussion of archery battle techniques and tactics in Viking Age Birka and the implications of the above mentioned equipment to this discussion. The analysis insinuates the importance and status of archery in 10th century Birka.

VIDAL, Francisco Élder Freitas. Identidade e Mobilidade Angolanas na Ficção de Pepetela. 2013. 134f. – Dissertação (Mestrado) – Universidade Federal do Ceará, Programa de Pós-graduação em Letras, Fortaleza (CE), 2013. / Submitted by Márcia Araújo (marcia_m_bezerra@yahoo.com.br) on 2014-05-21T11:09:16Z No. of bitstreams: 1 2013_dis_fefvidal.pdf: 1156155 bytes, checksum: fae8828a80ac5a197c86a57dbdbdd26b (MD5) / Approved for entry into archive by Márcia Araújo(marcia_m_bezerra@yahoo.com.br) on 2014-05-21T12:09:14Z (GMT) No. of bitstreams: 1 2013_dis_fefvidal.pdf: 1156155 bytes, checksum: fae8828a80ac5a197c86a57dbdbdd26b (MD5) / Made available in DSpace on 2014-05-21T12:09:14Z (GMT). No. of bitstreams: 1 2013_dis_fefvidal.pdf: 1156155 bytes, checksum: fae8828a80ac5a197c86a57dbdbdd26b (MD5) Previous issue date: 2013 / This research aims to analyze the Angolan national identity in Pepetela’s literary works, with emphasis on the novel O Planalto e a estepe [The Plateau and the steppe], published in 2009. The hypothesis that guides this dissertation is that Pepetela, in his works, argues that any model that takes the Angolan national identity as something fixed and finished is doomed to failure because, as well as its history, the identity of Angola is dynamic and mobile, i.e., it is in a constant process of reconfiguration. In order to verify this assumption, we choose as research corpus four Pepetela’s works in which the discussion of Angolan identity is clearly evident: the short story “Estranhos pássaros de asas abertas” ["Strange birds with open wings"] (from the book Contos de morte [Tales of Death], 2008) and the novels Yaka (1980), Mayombe (1985) and O Planalto e a estepe (2009). To the development of this work, we turn to some important ideas linked to identity discussion and to Pepetela’s fiction, being more important the following concepts: a) the ellipse of the hero, a thesis by which Robson Dutra shows that Pepetela, in order to criticize the authoritarian and hegemonic discourses, intentionally avoids to build characters inspired in classic heroes; b) the concept of unsubmissive literature developed by professor Roberto Pontes and that is linked with some works written by African Portuguese speakers who, even before the independence of their countries, rebelled against colonial literature forms prevailed in the former Portugal colonies in Africa; c) memory identity, an expression created by Janine Ponty and that is used by Jöel Candau (2012) in a study on the close relationship between memory and identity; and d) the understanding of nation as narration, argument developed by Homi Bhabha, and that has its origin in the fact that the nation, like literature, is also a narrative, given that it is developed from an arrangement of symbols, events, formulations and mythical characters that give meaning to the trajectory of the members of a given country. Through these and other theoretical constructs, we demonstrate that the different Angolas arisen from the Pepetela’s works shelter a diversity of individual identities that preclude any construction project of an Angolan national identity based on fixity and homogeneity. / Esta pesquisa tem como objetivo analisar a questão da identidade nacional angolana em obras de Pepetela, com ênfase para o romance O planalto e a estepe, publicado em 2009. A hipótese que serve como horizonte de trabalho é a de que Pepetela, através de suas obras, demonstra que qualquer modelo que tome a identidade nacional angolana como algo fixo e acabado está condenado ao fracasso, pois, assim como sua história, a identidade dessa nação é dinâmica e móvel, ou seja, está em constante processo de reconfiguração. Com o fim de verificarmos tal premissa, elegemos como corpus de pesquisa quatro obras de Pepetela em que a discussão sobre a identidade angolana fica claramente evidenciada: o conto “Estranhos pássaros de asas abertas” (extraído da obra Contos de morte, de 2008) e os romances Yaka (1980), Mayombe (1985) e O planalto e a estepe (2009). Para a consecução do trabalho, recorremos a alguns conceitos importantes ligados tanto à questão da identidade quanto às marcas da produção ficcional de Pepetela, merecendo destaque a) a elipse do herói, tese através da qual Robson Dutra demonstra que Pepetela, com o fim de criticar os discursos hegemônicos e autoritários, intencionalmente evita construir personagens à imagem e semelhança dos heróis clássicos; b) literatura insubmissa, conceito desenvolvido pelo professor Roberto Pontes e que se refere às obras de autores africanos lusófonos que, mesmo antes da independência de seus países, se insurgiram contra as formas de literatura colonial que predominavam na ex-colônias africanas de Portugal; c) memória identitária, expressão cunhada por Janine Ponty e que é utilizada por Jöel Candau (2012) em um estudo sobre as relações estreitas entre memória e identidade; e d) nação como narração, argumento desenvolvido por Homi Bhabha, e que diz respeito ao fato de que a nação, como a literatura, é também uma narrativa, tendo em vista que se desenvolve a partir de um arranjo de símbolos, acontecimentos, formulações míticas e personagens que visa atribuir sentidos para a trajetória dos membros de uma dada nação. Através desses e de outros construtos teóricos, mostramos que as diferentes Angolas que surgem das páginas da obra de Pepetela abrigam uma diversidade de identidades individuais que impossibilitam qualquer projeto de construção de uma identidade nacional angolana que se baseie na fixidez e na homogeneidade.

No description available.

After falling under the power of the Russian Crown, the Northern Black Sea steppe from the end of eighteenth century crystallized as the Russian government’s prime venue for socioeconomic and sociocultural reinvention and colonization. Vast ethnic, sociocultural and even ecological changes followed.  Present study is preoccupied with the marriage of the immigrant population from the German lands who came to the region in the course of its state orchestrated colonization, and was officially categorized as “German colonists.” The book illuminates the multiple ways in which marriage and household formation among the colonists was instrumentalized by the imperial politics in the Northern Black Sea steppe, and conditioned by socioeconomic rationality of its colonization. Marriage formation and dissolution among the colonists were gradually absorbed into the competencies of the colonial vertical power. Intending to control colonist marriage and household formation through the introduced marriage regime, the Russian government and its regional representatives lacked the actual means to exert this control at the local level. On the ground, however, imperial politics was mediated by the people it targeted, and by the functionaries tasked with its implementation. As the study reveals, the paramount importance was given to functional households and sustainable farms based on non-conflictual relations between parties. Situated on the crossroads of state, church, community, and personal interests, colonist marriage engendered clashes between secular and ecclesiastical bodies over the supremacy over it. The interplay of colonization as politics, and colonization as an imperial situation with respect to the marriage of the German colonists is explored in this book by concentrating on both norms and practices. Another important consideration is the ways gender and colonization constructed and determined one another reciprocally, both in legal norms and in actual practices. Secret divorces and unauthorized marriages, open and hidden defiance, imitations and unruliness, refashioning of rituals and discourses, and desertions – a number of strategies and performances which challenged and negotiated the marriage regime in the region, were scholarly examined for the first time in this book. / År 1804 formulerade tsar Alexander I:s regering nya riktlinjer för rysk migrationspolitik. Invandrare från de krigshärjade tyska länderna skulle värvas till kolonisering av stäppen norr om Svarta havet i en omfattande kampanj orkestrerad av den ryska staten. Dessa nykomlingar, som av myndigheterna kategoriserades som “tyska kolonister,” etablerade kolonier i hela regionen inom ett par årtionden. Boken presenterar den första studien av hur äktenskap och hushållsformering användes som instrument i den ryska koloniseringspolitiken i området, och hur dessa faktorer primärt styrdes av koloniseringens socioekonomiska rationalitet. Stabila hushåll och jordbruk som genererade avkastning eftersträvades in i det längsta. Ibland ledde detta till konflikter mellan den sekulära och den andliga makten om tolkningsföreträde rörande äktenskapets upplösning och ingående. Genom analys av både normer och praxis blottläggs samspelet mellan kolonisering som politik, och kolonisering som en imperiesituation, där äktenskapet och hushållet omförhandlades i skärningspunkten mellan myndigheter, kyrkosamfund, lokalsamhälle och enskilda. Studien visar att den ryska centralmakten och dess regionala representanter saknade verktyg för att utöva den effektiva kontroll som eftersträvades över kolonistäktenskap och hushållsformering på lokal nivå. Denna slutsats stöds genom att ett antal strategier och handlingsmönster som utmanade och bidrog till att omförhandla äktenskapsregimen i regionen identifieras och diskuteras.

Many land systems experience massive ecological pressure due to ongoing land use changes for the increasing demand for food, but also need to sustain essential ecosystem services. Computer-based model scenarios help to anticipate the consequences of different socio-economic future transition pathways for humans and nature and evaluate trade-offs between various demands on land. In many grassland ecosystems, the processes of agricultural abandonment in less attractive regions coexist with agricultural intensification in others. At the same time, the ecological value of natural grassland is rarely considered in decision making. By using the CLUMondo land use modelling framework I mapped the future composition of the land system of Orenburg province under five socio-economic scenarios with different ranges of food production intensification. The outcomes allowed me to identify hotspot areas for arable land expansion, grassland restoration, and agricultural abandonment. Most agricultural expansion is prevalent in three scenarios with high ambition for food production, and, without active policy interventions, some natural grassland areas in northern parts of the province are likely to be converted to cropland. In a scenario with low demand for food production, large areas in southern parts could be abandoned creating good opportunities for grassland restoration on former cropland, but possibly having negative socio-economic consequences, such as people’s migration to northern parts of the province. In a scenario with lesser ambition for crop production, but an increase in meat production, agricultural abandonment is less widespread and will even include some additional conversion of cropland to pasture. With appropriate policies aimed at supporting sustainable grazing practices (together with favourable global socio-economic conditions), such scenario can provide an opportunity for satisfying demands for food, providing livelihoods, and ensuring the flow of ecosystem services by grassland ecosystems.

No description available.

Die semiaride Steppe der Inneren Mongolei (China) ist ein gefährdetes Ökosystem. Der Wandel vom traditionellen nomadischen Lebensstil hin zur konventionellen Landwirtschaft überlastet die Steppe und führt zu Degradierung und Desertifikation. Besonders die intensive Beweidung belastet die weiten Grasflächen und mindert deren natürliches Potential Kohlen-stoff (C) im Boden zu speichern. Um den Einfluss unterschiedlicher Beweidungsintensitäten auf die semiaride Steppe zu untersuchen, wurden im Rahmen des Projektes Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) das Einzugsgebiet des Xilin Flusses in der Inneren Mongolei von 2004 bis 2009 untersucht. Dafür wurden u. a. meteorologische und Eddykovarianz-Messungen an definierten Standorten durchgeführt. Ziel dieser Messungen war es, die Unterschiede im Energiehaushalt und den Kohlendioxid- und Wasserflüssen (CO2- und H2O-Flüsse) für die dominanten Steppenarten und unter verschiedenen Beweidungsintensitäten zu erfassen. Die Schließung der Energiebilanz ergab eine Schließungslücke von 10 – 30% in Abhängigkeit der meteorologischen Bedingungen, wobei die Lücke unter feuchten Bedingungen kleiner ist. Die gemessenen CO2- und H2O-Flüsse sind klein im Vergleich zu Grasländern in den gemäßigten Zonen und reagieren sensitiv auf Veränderungen der Einflussfaktoren. Dabei ist die Evapotranspiration (ET) eng an den eingehenden Niederschlag (P) gekoppelt und über längere Zeiträume wie ein Jahr entspricht ET dem P (ET: 185,7 mm a-1 bis 242 mm a-1; P: 138 mm a-1 bis 332 mm a-1). Die Jahressummen für den Nettoökosystemaustausch (NEE) reichen von -10,7 g C m-2 a-1 (2005) bis -67,5 g C m-2 a-1 (2007) für die unbeweidete Steppe und charakterisieren diese als eine leichte Nettosenke für atmosphärisches CO2. Grundsätzlich zeigt die unbeweidete Steppe eine höherer C-Sequestrierung (maximale C-Sequestrierung im Mittel -0,06 g C m-2 s-1) als die beweidete Steppe (maximale C-Sequestrierung im Mittel -0,02 g C m-2 s-1). Die Messergebnisse zeigen, dass die Steppe unter trockenen Verhältnissen zur CO2-Quelle wird, unter erhöhten Niederschlagsbedingungen zur CO2-Senke und die Beweidung die C-Sequestrierung des Ökosystems unter beiden Bedingungen einschränkt. Im Vergleich der beiden Steppenarten (Leymus chinensis und Stipa grandis) konnte für Leymus chinensis eine höhere Trockentoleranz beobachtet werden. Diese führt zu einer höheren C-Sequestrierung unter trockeneren Verhältnissen. Unabhängig von der Steppenart sind die wichtigsten Einflüsse auf das Ökosystem die Bodenfeuchte, die vom eingehenden P abhängt, die Temperatur (T) und die Beweidung. Diese Faktoren können dabei nicht unabhängig voneinander betrachtet werden. Der Einfluss durch die Beweidung beeinflusst das Ökosystem nachhaltig, wobei die Intensität und die Dauer (Jahre) der Beweidung entscheidend sind, da nicht nur die oberirdische Biomasse reduziert wird, sondern gleichzeitig die Bodeneigenschaften. Um die Sensitivität auf den CO2- und H2O-Austausch der semiariden Steppe über die Messungen hinaus abzuschätzen, wurden Simulationen mit den Modellen BROOK90 und DAILYDAYCENT (DDC) durchgeführt. Beide Modelle konnten gut an die Bedingungen der semiariden Steppe angepasst werden, wobei die Übereinstimmung zwischen der gemessenen und modellierten ET für BROOK90 besser war (r2 = 0,7) als für DDC (r2= 0,34). Beide Modelle konnten gut die Dynamik der ET-Messungen wiedergeben. Die Sensitivitätsanalyse hat gezeigt, dass die Beziehung zwischen P und ET entscheidend für das Ökosystem ist und sich Änderungen in der T nur zum Ende und Beginn der Vegetationsperiode auf den Wasseraustausch auswirken. DDC konnte sehr gut den gemessenen CO2-Austausch simulieren. Die Ergebnisse zeigen die Sensitivität gegenüber den klimatischen Faktoren T, P und der Beweidung. Die CO2-Flüsse werden durch hohe Beweidungsintensitäten so stark minimiert, dass andere Einflussfaktoren dahinter zurücktreten. Bei leichten Beweidungsintensitäten wirkt sich dagegen besonders der P auf die Austauschprozesse aus. Die DDC-Ergebnisse zeigen, dass unter den derzeitigen Bedingungen der bodenorganische Kohlenstoff (SOC) verringert wird, also C aus dem Boden freigesetzt wird. Auch unter unbeweideten Verhältnissen steigt der SOC nicht wieder auf das Ausgangsniveau (von vor der Beweidung) an. Die Ergebnisse zeigten, dass die C-Sequestrierung der Steppe nur erhöht werden kann, wenn der P steigt, die T in einem Optimumbereich (+/- 2°C) bleibt und die Beweidung minimiert wird. Die Messungen und Modellergebnisse zeigen, dass der Niederschlag der limitierende Faktor der semiariden Steppe ist. P bestimmt die Bodenfeuchte, diese wiederum beeinflusst das Pflanzenwachstum und somit den CO2- und H2O-Austausch der Pflanzen. Die Beweidung strapaziert das Ökosystem und reduziert dadurch die CO2- und H2O-Flüsse und verändert die Bodeneigenschaften nachhaltig. Unabhängig von der klimatischen Entwicklung, ist die derzeitige überwiegend hohe Beweidungsintensität der Steppe eine Belastung für das Ökosystem und schränkt das Pflanzenwachstum langfristig ein, was u. a. die Desertifikation begünstigt. / Semiarid grasslands in Inner Mongolia (China) are degrading. The change from the traditional Nomadic lifestyle to conventional agriculture stresses the semiarid grasslands and increases desertification. In particular, intense grazing of the semiarid grasslands reduces their potential of storing carbon (C) in the soil. In the project Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) a team of scientists researched the catchment area of the Xilin River to investigate impacts of different grazing intensities on semiarid grasslands. Meteorological and eddy covariance measurements took place from 2004 to 2009. The aim of the measurements was to examine the energy balance and the exchange of the carbon dioxide (CO2) and water (H2O) fluxes of the dominant grasslands in Inner Mongolia under different grazing intensities. The energy balance could be closed by 70 – 90% depending on the driving factors. The energy balance shows a smaller gap for moist conditions. The CO2 und H2O fluxes in the study area are much smaller than in temperate grasslands and show a high sensitivity towards the driving factors. Evapotranspiration (ET) is closely connected to the precipitation (P) and over longer periods of a year or more, ET nearly matches P (ET: 185.7 mm a-1 to 242 mm a-1; P: 138 mm a-1 to 332 mm a-1). The annual net ecosystem exchange (NEE) of ungrazed grassland ranges from -10.7 g C m-2 a-1 (2005) to -67.5 g C m-2 a-1 (2007), which makes the grassland a small CO2-sink. Overall, ungrazed grassland shows higher C sequestration (averaged maximum -0.06 g C m-2 s-1) than grazed grassland (averaged maximum -0.02 g C m-2 s-1). The measurements show the semiarid grassland as a CO2-source under dry conditions and as a CO2-sink under moist conditions, while grazing decreases the C sequestration for both climatic conditions. A comparison of the two dominant steppe types (Leymus chinensis and Stipa grandis) showed a higher tolerance for Leymus chinensis under dry conditions, which resulted in higher C sequestration for this vegetation. Besides the steppe type, the main driving factors are P, temperature (T) and grazing. These factors can not only be considered in isolation, but cross correlation needs to get considered as well. Grazing affects the sustainability of the ecosystem, with an increasing impact due to grazing intensity and duration (years). The impact of grazing influences the vegetation directly and shows indirect impacts for the soil properties. Simulations with the models BROOK90 and DAILYDAYCENT (DDC) enable a sensitivity analysis of CO2 and H2O fluxes of the semiarid grassland. Both models performed well, but BROOK90 showed a better fit to observed ET (r2 = 0.7) than DDC (r2= 0.34). Both models simulated the dynamics of the measured ET well. The sensitivity analysis showed a close relationship between P und ET and a smaller impact on ET due to a change in T. DDC performs well in the simulation of CO2 exchange dynamics of the semiarid grassland. The results show for high grazing intensities a decreasing influence of the other driving factors. A change in P has an influence on CO2 and H2O fluxes under low grazing intensities. The results also show a decrease in soil organic carbon (SOC) as grazing intensity increases (under current climatic conditions). An increase in SOC could only be achieved under an increase in P, an optimum T and low grazing intensities. The measurements and results of the simulations indentify P as the main driving factor controlling the CO2 and H2O fluxes in the semiarid grassland. P influences the soil moisture and this influences plant growth, which governs the CO2 and H2O exchange of the vegetation. Grazing decreases the CO2 and H2O exchange and affects the soil properties in the long term. Besides climate change, the current high grazing intensities of the semiarid grassland have a negative impact on the ecosystem, decreasing plant growth and increasing desertification.

Thermophilous oak forests are a habitat characterized by a large diversity of vascular plants. In the case of open canopy woodlands, the diversity of the herb undergrowth is enhanced by the significant heterogeneity of the environment. It can be demonstrated for example at the Dětaň Chlum in neighborhood of the Doupovské hory Mts. However, it has not yet been fully known which natural characteristic have the most significant influence on the formation of such a diverse vegetation. One of the possible causes can be found in historical management. Therefore, this work provides some insight into the history of forest management in the Podbořany region based on archival materials such as Historical Forest Survey, Management Plans or Archive Maps. The obtained information is to a large extent surprising. It has been shown that coniferous stands with a long time of timber extraction have dominated the Dětaň chlum in the past. However, this contradicts the assumption that it is an ancient oak coppice, as suggested by the current appearance of vegetation with a high incidence of polycormones in the local nature reserve. To find out the environmental causes of the current heterogeneity of vegetation, I used the CANOCO statistical program to analyze the dependence of my own phytosociological data on selected...

Les écosystèmes herbacés méditerranéens, caractérisés par une importante biodiversité, ont subi de considérables changements d‟usage. Désormais, leur conservation est devenue insuffisante au regard de l‟augmentation des dommages causés par les activités humaines. La restauration écologique apparaît donc comme un outil approprié pour participer à leur préservation. Des recherches préalables sur les différents compartiments de l‟écosystème ainsi que sur les facteurs responsables de l‟assemblage de leurs communautés avant et après dégradations sont donc nécessaires afin de mettre en place des méthodes de restauration adaptées à ces écosystèmes. Ainsi, en utilisant comme modèle biologique les Coussouls de Crau et leurs friches post-culturales (Bouches-du-Rhône, France), représentatif de nombreux écosystèmes steppiques méditerranéens, nous avons choisi de déterminer et d‟étudier les principaux filtres potentiellement responsables de l‟organisation de cette communauté végétale. Le pâturage ovin, les changements trophiques du sol, les phénomènes de compétition et la capacité de reproduction et/ou de dispersion des espèces, identifiés lors d‟une première étude sur la régénération de la steppe, ont ainsi été étudiés dans trois expérimentations différentes. Deux protocoles de restauration écologique in situ (transfert de foins et semis d‟espèces structurantes) et un protocole d‟expérimentation ex-situ testant les interactions d‟une sélection d‟espèces de la steppe ont permis de réaliser ces recherches. Nos principaux résultats montrent que les filtres de reproduction/dispersion, le niveau trophique du sol, la compétition et le régime de perturbations récurrentes lié au pâturage ovin ont un rôle déterminant dans les changements de la composition et de la structure de la communauté et ils expliquent ainsi en partie le ralentissement de sa dynamique successionnelle vers la steppe de référence. Nous avons également pu démontrer que ces filtres interagissaient entre eux. Au niveau de la recherche appliquée, les protocoles testés favorisent le retour de la végétation steppique, néanmoins la composition des parcelles restaurées reste toujours très différente de l‟écosystème de référence à très court terme (deux à trois années après la restauration). Cela démontre que même si nous comprenons mieux aujourd‟hui les facteurs expliquant l‟organisation de cette communauté, il est cependant toujours difficile de la restaurer dans son intégralité car il n‟est pas aisé de manipuler et de trouver un équilibre entre l‟action de ces différents facteurs. Il est donc désormais plus que nécessaire de poursuivre ces recherches fondamentales et appliquées notamment au niveau des processus de maturation et de structuration des vieilles communautés végétales herbacées. / Mediterranean herbaceous ecosystems which are characterized by a high biodiversity have been submitted to a lot of changes in use. Their conservation is not sufficient enough and ecological restoration seems to be an adapted solution to improve conservation efforts as it can mitigate damages induced by human activities. To develop restoration methods adapted to these ecosystems, preliminary researches on the different communities composing an ecosystem and the filters which are responsible for community assemblage before and after disturbance are necessary. Representative of numerous Mediterranean steppe ecosystems, the “Coussouls de Crau” and their ex-arable-fields (Bouches-du-Rhône, France) are the biological models used to identify and study the principal filters potentially responsible for organizing the plant communities. Sheep grazing, trophic changes, competition and reproduction and /or species dispersal, were identified in a first study on steppe regeneration; these filters were then the core of the following three research experiments. We carried out two in-situ restoration protocols (hay transfer and sowing foundation species) and one ex-situ experiment testing interactions between a selection of steppe species. The main results show that reproduction, seed dispersal, soil trophic level, competition, extensive sheep grazing are filters which have a determinant role in structuring the communities, in determining plant composition and partly in explaining the slow dynamics towards the reference steppe. Also, we show that filters interact between them. For applied restoration, the tested methods promote steppe vegetation come back, but in the short term (two or three years after restoration), the composition of restored areas remains different to the reference ecosystem. Even if we understand better the different factors which explain community organization, these results demonstrate that it is difficult to restore it integrally because it is not easy to manipulate and find an equilibrium between the different filters actions. Now it is necessary to continue these fundamental and applied researches, in particular on the maturation and structure of the old herbaceous plant communities.

Les steppes algériennes sont situées entre le Sahara et la méditerranée. Le climat semi-aride autorise le développement d’une végétation naturelle et le maintien du pâturage. Ce milieu, à équilibre environnement fragile est le théâtre de changements, avec le déclin du nomadisme, la transformation des éleveurs en agro-pasteurs, l’extension de l’agriculture et l’urbanisation. Nous abordons ces points en articulant le passé au présent pour mettre en lumière le poids de l’activité d’élevage fortement enracinée dans la polarisation des tendances actuelles.Basé sur une méthode quantitative par télédétection et d’analyse d’un nombre important d’images satellitaires, ce travail capte les changements opérés sur les processus environnementaux et recherche des liens utiles d’interactions entre eux. L’analyse des précipitations par un indicateur spécialisé (SPI) révèle son caractère fluctuant. Les séquences sèches laissent des conséquences dommageables sur la végétation, l’activité humaine et la réactivation d’ensablement.Des changements spectaculaires sont observés, l’agriculture est sortie des endroits préférentiels pour conquérir de nouveaux espaces dans les plaines et terrasses. Le sable réapparaît occasionnellement, sa corrélation avec la sécheresse a pu être démontrée. L’ensablement s’amorce après la persistance de trois années sèches. En revanche, une année humide est suffisante pour réduire substantiellement la surface ensablée. C’est pourquoi, l’interaction entre l’activité hydrique et éolienne est analysée. Nous proposons un modèle d’échange sédimentaire, en introduisant la notion de recyclage sédimentaire, transport additionné et transport opposé.En termes d’aménagement, les mesures protectrices a priori sont privilégiées à la gestion postérieure des impacts de la dégradation. Par ailleurs, la gestion prospective est abordée à travers l’exploitation des données de prévisions météorologiques et l’identification des variations spectrales indicatrices de réactivation du processus d’ensablement dans l’imagerie satellitaire. / The Algerian steppes are located between the Sahara and the Mediterranean. The semi-arid climate allows the development of natural vegetation and the maintenance of pasture. This fragile environment is the scene of change, with the decline of nomadism, the transformation of pastoralists into agro-pastoralists, the extension of agriculture and urbanization. We approach these points by articulating the past to the present to highlight the weight of the livestock activity strongly rooted in the polarization of current trends.Based on a quantitative remote sensing and analysis method for large number of satellite images, this work captures changes in environmental processes and seeks useful links between them. The precipitation analysis by a specialized indicator (SPI) reveals its fluctuating nature. Dry sequences leave damaging consequences on vegetation, human activity and sand drift reactivation.Spectacular changes are observed, agriculture has emerged from preferential places to conquer new spaces in the plains and terraces. The sand occasionally reappears, its correlation with the drought could be demonstrated. The sand drift begins after the persistence of three dry years. On the other hand, a wet year is enough to substantially reduce the sand area. This is why the interaction between water and wind activity is analyzed. We propose a model of sedimentary exchange, introducing the concept of sedimentary recycling, added transport and opposite transport.In terms of management, anticipatory protective measures are favored for the later management of the impacts of degradation. Furthermore, the prospective management is approached through the exploitation of meteorological forecast data and the identification of spectral variations indicative of reactivation of the sand drift in satellite imagery.