Tesi sul tema "Limite supérieure de la forêt"
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Jolly, Marie-Claude. "Variations holocènes de la limite supérieure de la forêt sur les versants du Cantal d'après l'analyse pollinique". Paris 7, 1991. http://www.theses.fr/1991PA070098.
Testo completoThis study is a contribution of the vegetation of the upper sloppe of cantal during the late holocene. It differs from early studies by high altitude borings, corresponding to the limit of "mountain aera" and "subalpine aera" and on the middle of the subalpine aera", but also by the horizontal and vertical fineness of samplings. Several borings realised on bogs and soils between 1260 and 1750 meters have allowed to hold 14 profils analysed for their content of pollens and spores ; besides four soils on the occidental slope are studied through their chimical and sedimentologie aspects. After a description of the geographical environnement, and the vegerationstory during geological times up to now and from a new serie of climatological datas collected from the high altitude of the massif, we can give an outline of temporal succession of vegetal formation and their arangement all along slopes. The study of past vegetation includes direct comparison with modern pollen assemblages, it shows the followings results : the abondunce of fire and beech pollens which are hever very numerous today under fir plantations and aside it constitutes a serious presumption for wooded conditions during the. .
Belet, Jean-Marc. "Variations tardiglaciaires et holocènes dans la limite supérieure de la forêt dans les Pyrénées centrales : l'exemple du vallon d'Estibère (Hautes-Pyrénées, France)". Toulouse 3, 2001. http://www.theses.fr/2001TOU30195.
Testo completoIn the central Pyrénées, the Estibère valley is the subject of actuo- and paleoecological work aiming to reconstruct timberline fluctuations during the last 15000 years. In the first part, we present the main physic and biologic elements of the study area. The aim of the second part is to verify in actual whether it's possible to caracterize the timberline in term of modern pollen rain. Three altitudinal transects are presented (80 modern pollen spectra and floristic inventory). .
Birre, Deborah. "Dynamique spatio-temporelle de la limite supérieure de la forêt dans la partie orientale des Pyrénées françaises : le rôle de l’anthropisation et des changements climatiques". Electronic Thesis or Diss., Paris 13, 2024. https://theses.hal.science/tel-04651374.
Testo completoThe position of the upper forest limit, which delineates the transition between forested areas and alpine grasslands in mountainous regions, is theoretically determined by temperatures. However, its response to current climate warming is intricate and heterogeneous, carrying significant ecological and socio-economic implications. This thesis focuses on the Eastern Pyrenees to unravel the interactions between various potential factors and the dynamics of the upper forest limit. The central hypothesis suggests that the hierarchy of influencing factors, whether climatic or anthropogenic, varies depending on the scale of analysis. To test this hypothesis, a methodology combining geomatics for diachronic mapping at the scale of the entire study area, regional statistical analyses of potential factors, and local field surveys has been employed. Four major results have emerged from these analyses : (i) the lowering of the forest limit altitude compared to its theoretical altitude; (ii) the complementary nature of dynamic indicators beyond mere altitude changes; (iii) the multidimensionality of the dynamic depending on the indicator and scale considered; and (iv) the multiscale nature of the dynamic, where local contexts variably influence outcomes. These findings confirm the central hypothesis of the thesis and shed light on the relative effects of climate at regional and local scales
Belingard, Christelle. "Etude dendroécologique de la dynamique de la limite supérieure de la forêt dans les Alpes du sud, en relation anec les facteurs climatique et anthropique". Aix-Marseille 3, 1996. http://www.theses.fr/1996AIX30110.
Testo completoPETITCOLAS, VERONIQUE. "Dendroécologie comparée de l'épicéa, du mélèze, du pin cembro et du pin à crochets en limite supérieure de la foret dans les Alpes françaises : influence de la variabilité macro-écologique". Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10012.
Testo completoBouka, Biona Clobite. "Echanges forêt-atmosphère en milieu tropical humide. Dynamique de la couche limite. Expérience DECAFE". Toulouse 3, 1994. http://www.theses.fr/1994TOU30143.
Testo completoDavid, Fernand. "Evolutions de la limite supérieure des arbres dans les Alpes françaises du nord depuis la fin des temps glaciaires". Aix-Marseille 3, 1993. http://www.theses.fr/1993AIX30045.
Testo completoMarquis, Benjamin. "La limite de répartition supérieure de l'érable à sucre et du bouleau jaune sous contrôle climatique: étude dendroécologique le long d'un gradient d'élévation". Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8735.
Testo completoBrion, Elisabeth. "Mesure du flux de rayons gamma entre 50 et 350 GeV du blazar Mrk 501 avec l'expérience CELESTE". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2005. http://tel.archives-ouvertes.fr/tel-00089747.
Testo completoCette thèse présente la démarche effectuée jusqu'à la détection de Mrk 501 : dans un premier temps, par la validation de l'analyse utilisée sur des observations de la nébuleuse du Crabe, chandelle standard des télescopes Tcherenkov atmosphériques ; puis la détermination des coupures d'analyse, dépendantes de la région du ciel pointée, à partir d'observations du blazar Mrk 421, de même déclinaison que Mrk 501, dont la forte activité permet une détection claire. Enfin, des simulations, tenant compte de la qualité de l'atmosphère et améliorées pour mieux reproduire le détecteur, ont permis d'établir la surface effective de l'instrument pour en déduire le flux de Mrk 501 entre avril et juin 2000. Ce flux a été comparé avec un modèle d'émission de type synchrotron self-Compton et avec des données prises en rayons X. Elles indiquent que Mrk 501 apparaissait légèrement plus actif durant cette période par rapport au reste de l'année et à l'année 2001. Une limite supérieure au flux est calculée pour l'ensemble des autres mesures. C'est une première mesure dans le domaine d'énergie 50 - 350 GeV (gamme représentant les limites en énergie pour lesquelles le taux de comptage, c'est-à-dire la convolution du spectre de l'astre avec la surface effective de collection de l'instrument, se révèle supérieur à 20 % du maximum de comptage). Elle apporte des contraintes sur la position du maximum d'émission Compton inverse et tend à favoriser, dans ce cas précis, des processus d'émission X et gamma par deux populations d'électrons différentes (la variation dans le domaine X est faible comparée à celle du domaine gamma).
DURAND, Emmanuel. "Recherche de photons pulsés au-dessus de 30 GeV dans le pulsar du Crabe et PSR B1951+32 avec le détecteur Tchérenkov atmosphérique CELESTE". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2003. http://tel.archives-ouvertes.fr/tel-00002815.
Testo completoAdroit, Benjamin. "Structures des paléoforêts européennes de la fin du Cénozoïque : apport des interactions plante-insecte". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG008/document.
Testo completoInsects are the most diverse animals on Earth, and neatly associated with plants they represent two of the major groups of organisms both in species diversity and biomass quantity. The majority of their interactions involves insect feeding and insect parasitism mostly on leaves. Plant and insect compose one of the main trophic levels in ecosystems over the 325 million years. Today, the continuous and fast rising of temperature mostly due to human activities since the last century is disturbing the balance of ecosystems on Earth. Consequently, to understand the role of plant and insect interactions, through time but also trophic networks, becomes crucial. The fossil record is an exceptional opportunity to survey responses of plant-insect interaction to climate variations over long time interval through traces of plants reactions caused by interaction with insects, as Earth has already experienced many climate changes. For the last 3 million years, oscillations between long cold periods and short warm periods have occurred. Europe ecosystems has been particularly impacted. The Lagerstätte of Willershausen (Germany) was specifically study. It is an exceptional fossil outcrop that contains ca. 8000 collected fossil leaves. These leaves testify a paleoforest developed there around 3—2.6 Ma ago in a climate warmer than today (ca. +5°C). Under these conditions, many plant species typical of the Mediterranean ecosystems were settled there, such as Montpellier maple or Olive tree. For comparison, other paleoforests were studied: Berga (similar in age and geographically close to Willershausen) and Bernasso (younger than Willershausen (2.16—1.96 Ma) and located in southern France close to Mediterranean. These forests were compared as many common plant taxa were similar between each other. Furthermore, some species today endemic to the Caucasian region, such as Persian ironwood or Caucasian elm, were also present in these outcrops. The aim of this study is to determine how far the climate differences could be involved in the changes of plant-insect interactions in European paleoforests of the late Pliocene – early Pleistocene. Results highlighted the impacts of both hydric and temperature seasonality, hitherto underestimated in the fossil record, on the patterns of plant-insect interaction in the European paleoforests. It appeared that ecosystems subject to intense hydric seasonality could led to higher specialization of plant-insect interaction inferred by higher rate of observed damages due to ‘specialists insects’. In parallel, the coolest temperature during the year seems to be a major factor in the low diversity of damage in paleoforest, presumably due to lower insect metabolism. Absence of convergent correlations between plant richness and damage richness could suggested that influence of climatic factors override impact of these local biotic factors. In order to understand the whole parameters that could have an impact on plant-insect interactions, our current knowledges are still insufficient. It would be wise to make more investigations on modern forests with the methods as applied in fossil record community structure studies. These investigations could help to understand the factors potentially involved in the establishment of a pattern of plant-insect interactions. It is in this perspective that a part of this study was precisely focused on one plant species (Parrotia persica) currently endemic to the Hyrcanian forest (Iran). This forest is supposed to be an analogue forest of the European paleoforests as those studied in this thesis. For now, observations made in Iran tend to corroborate our interpretation. Finally, the studies on plant-insect interactions in past and extant ecosystems, combined with the study of climatic changes, should permit us to better characterize the relations between plants and insects in forests through time
Bodin, Jeanne. "Observed changes in mountain vegetation of the Alps during the XXth century - Role of climate and land-use changes". Phd thesis, Université Henri Poincaré - Nancy I, 2010. http://tel.archives-ouvertes.fr/tel-00592144.
Testo completoMansuy, Nicolas. "Régimes des feux et dynamique forestière post-feu de part et d'autre de la limite nordique des forêts commerciales au Québec". Thèse, 2013. http://www.archipel.uqam.ca/5504/1/D2490.pdf.
Testo completoEl, Guellab Ahmed. "Variations du régime des feux en réponse aux changements climatiques holocènes à la limite nordique de la forêt commerciale au Québec". Mémoire, 2012. http://www.archipel.uqam.ca/5154/1/M12546.pdf.
Testo completoPaul, Véronique. "Les facteurs écologiques limitant la répartition nordique du thuya de l'est (Thuja occidentalis L.)". Mémoire, 2011. http://www.archipel.uqam.ca/5266/1/M12501.pdf.
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