Made available in DSpace on 2016-12-12T20:12:27Z (GMT). No. of bitstreams: 1 PGEF13MA002.pdf: 1189364 bytes, checksum: 02eb7d4aa15b616a2256de136a1b1c23 (MD5) Previous issue date: 2013-07-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present study aimed to evaluate the community dynamics of tree species in a fragment of Montane Araucaria Forest, in the municipality of Lages, SC, over a period of four years (2008-2012). For this, were ploted 50, 10x20m, permanent plots was performed the environmental characterization (terrain, soils and canopy cover), obtained the spatial coordinates, determined the regeneration guilds [Pioneer (P), Climax Light Demanding (CEL) and Climax Shade Tolerant (CTS)] and calculated dynamics rates (mortality, recruitment, loss and gain in basal area, turnover and net change in abundance and basal area) of all surveyed species (diameter at breast height &#8805; 5cm). The existence of significant association between regeneration guilds and dynamic rates was verified by qui-square tests, applied to contingency tables. Changes in relative participation of regeneration guilds between years were analyzed using proportion tests. The spatial structuration of dynamics rates was evaluated through I Moran correlograms and the influence of environmental variables analyzed through regression trees. In 2008, 84 species were found (P: 9, CLD: 64 and CST: 11), with a density of 1.841 ind.ha-1 and basal area of 36.17 m².ha-1. In 2012, 83 species (P: 9, CLD: 63 and CST: 11), with a density of 1.882 ind.ha-1 and basal area of 39.17 m².ha-1 were observed. The dynamics rates did not demonstrated spatial autocorrelation. The gain and turnover in basal area rates were higher, respectively, in locations with lower values of canopy cover (<80.63%) and with higher values of sum of base in the soil (&#8805;61.77%). No significant association between the dynamics patterns and regeneration guilds was observed. The relative participation of guilds stayed constant during the evaluated period, with a low floristic substitution. Thus, it is possible to conclude that, in general, the dynamics occurred randomly in the space, and the forest fragment is in the process of structural instability and floristic-successional stability / O presente estudo teve como principal objetivo avaliar a dinâmica da comunidade de espécies arbóreas, em um fragmento de Floresta Ombrófila Mista Montana, no Município de Lages, SC, ao longo de um período de quatro anos (2008-2012). Para isto, foram alocadas 50 parcelas permanentes, de 10x20m, onde foram realizadas a caracterização ambiental (relevo, solos e cobertura do dossel), obtidas as coordenadas espaciais, determinadas as guildas de regeneração [Pioneiras (P), Climácicas Exigentes em Luz (CEL) e Climácicas Tolerantes ao Sombreamento (CTS)] e calculadas as taxas de dinâmica (mortalidade, recrutamento, ganho e perda em área basal, rotatividade e mudança liquida em abundância e área basal) de todas as espécies amostradas (diâmetro na altura do peito &#8805; 5cm). A existência de associação significativa entre guildas de regeneração e padrões de dinâmica foi verificada por meio de testes de qui-quadrado, aplicados a tabelas de contingência. Mudanças das participações relativas das guildas de regeneração entre os anos foram analisadas por meio de testes de proporção. A estruturação espacial das taxas de dinâmica foi avaliada por meio de correlogramas de I de Moran e a influência dos fatores ambientais verificada através de árvores de regressão. No ano 2008 foram verificadas 84 espécies (P: 9, CEL: 64 e CTS: 11), possuindo uma densidade de 1.841 ind.ha-1 e área basal de 36,17m2.ha-1. No ano de 2012, verificou-se 83 espécies (P: 9, CEL: 63 e CTS: 11), com densidade de 1.882 ind.ha-1 e área basal de 39,17m2.ha-1. As taxas de dinâmica não apresentaram autocorrelação espacial. As taxas de ganho e rotatividade em área basal foram maiores, respectivamente, nos locais com menores valores de cobertura do dossel (<80,63%) e com maiores valores de soma de base no solo (&#8805;61,77%). Não foi verificada associação significativa entre os padrões de dinâmica observados e guildas de regeneração. A participação relativa das guildas permaneceu constante durante o período avaliado, com uma baixa substituição florística. Desta forma, conclui-se que, de modo geral, a dinâmica ocorreu de forma espacialmente aleatória e o fragmento florestal encontra-se em fase de instabilidade estrutural e estabilidade florística-sucessional

En 2013, Le Groupe d'experts Intergouvernemental sur l'Evolution du Climat (GIEC) publie son cinquième rapport concernant les changements climatiques. Il y est souligné que le réchauffement climatique est sans équivoque, et que de nouvelles émissions de gaz à effet de serre impliqueront une poursuite du réchauffement et des changements affectant toutes les composantes du système climatique. En région tropicale, une hausse de la température, ainsi qu'une intensification des événements de sécheresse et de pluviométrie extrêmes sont à prévoir. C'est dans ce contexte que s'inscrit ce travail, dont le but est d'étudier la réponse de la forêt tropicale à ces changements climatiques prédits en Guyane Française. Pour ce faire, j'ai utilisé les données du dispositif de suivi forestier de Paracou pour construire un modèle de dynamique individuel basé sur les traits fonctionnels des arbres. Un modèle de mortalité a d'abord été réalisé puis couplé à un modèle de croissance.Le modèle couplé ainsi construit permet de modéliser la croissance et la mortalité des arbres sur un pas de temps de 2 ans tout en tenant compte de leur ontogénie et de leurs traits fonctionnels. Ce modèle a d'abord été appliqué aux essences commerciales de Guyane Française en forêt naturelle et exploitée en y ajoutant un indice de stress hydrique. Ceci permet de montrer que le stress hydrique fait baisser la croissance et augmenter la mortalité, tandis que l'exploitation a l'effet inverse. Malgré le signal commun, différentes réponses sont observées selon les espèces. Le modèle a ensuite été appliqué à la communauté en forêt naturelle pour identifier les drivers climatiques et les processus impactés. Il ressort que la croissance est impactée par le stress hydrique et la température, et que la mortalité est impactée par le stress hydrique et la pluviométrie totale.Ces résultats ont enfin permis de construire un modèle complet de dynamique forestière climat dépendant, et de simuler l'évolution d'une communauté pendant un siècle selon différents scénarios correspondant aux prédictions du GIEC. Les simulations mettent en évidence une très forte diminution de la croissance, ainsi qu'une plus faible diminution de la mortalité. Ceci entraine une diminution notable de la surface terrière, du diamètre quadratique et de la biomasse fraiche. Une analyse de sensibilité montre que ces changements sont principalement dus à l'augmentation sévère des températures prédites pour le siècle à venir. Des pistes de réflexion sur les enjeux de modélisation et les échelles considérées sont proposées en discussion de ce travail. / In 2013 the intergovernmental panel on climate change (ipcc) publishes its fifth report. This report underlines that an increase of temperature and a strengthening of drought and extreme rainfall are expected in tropical regions. This work was made in this context of climate changes, and aimed to study the response of the rainforest to predicted climate changes. To do this, i used the data from the study site of Paracou French Guiana to build an individual based dynamics model based on the functional traits of trees. This model was first applied to species with a commercial interest in French Guiana, in natural and logged forest and adding a water stress index as predictor. Water stress decreases growth and increases mortality, while logging had the opposite effect. The model was then applied to the community in natural forest for identifying potential climate drivers and impacted processes. Growth is impacted by the water stress and temperature and mortality is imp acted by the water stress and the total rainfall. These results allowed us to build a climate dependent model of forest dynamics and to run simulations of the evolution of a community under different scenarios for the next century. Simulations showed a decrease of growth and a small decrease of mortality. This resulted in a substantial decrease of basal area, squared diameter and fresh biomass.

Le changement climatique (CC) actuel, très rapide, va imposer aux espèces de faire évoluer leurs traits d’histoire de vie ou leur aire de répartition. En raison de leur long cycle reproductif, les arbres pourraient ne pas avoir la capacité à s’adapter suffisamment vite et leur aptitude à la migration devrait être déterminante. Les vitesses de colonisation des essences forestières lors de l'holocène ont fortement été revues à la baisse aux cours de la dernière décennie (quelques centaines contre quelques centaines de m/an). Dans ce contexte et en s'appuyant sur le sapin pectiné (Abies alba Mill.) en tant qu'espèce modèle nous avons étudié les principaux facteurs conditionnant l'aptitude à la migration. A partir de placettes de régénérations situées sur la face nord du Mont Ventoux, nous avons estimé la dispersion et le recrutement du sapin, en intégrant les sources de graines et les principales caractéristiques environnementales. La dispersion a également été estimée à partir de données génétiques. Dans les deux cas, les distances de dispersion sont de l’ordre du décamètre. La diversité génétique et l'évolution démographique ont été étudiées au sein de la régénération de sapins afin de tester l'hypothèse de purge de consanguinité. L'espèce présente en effet un régime de reproduction mixte, et la part d'autofécondation, à laquelle s'ajoute la reproduction entre individus consanguins, est à l’origine de l'excès d’homozygotie observé généralement dans la régénération, excès diminuant avec l’âge sous l’action d'une probable purge des individus les plus homozygotes. Les semis étudiés ne présentent pas un fort excès d’homozygotie, néanmoins, les individus les plus homozygotes meurent préférentiellement. Enfin, un modèle de dynamique forestière intégrant les processus, qui contrôlent la migration, a été implémenté afin d'évaluer la compatibilité entre la migration des espèces à long cycle de vie et le CC. Les premiers résultats de nos simulations indiquent que le sapin n’est pas capable de migrer aussi vite que s’opère le réchauffement. / Current climate change (CC), really fast, will impose species to change their history life traits or their distribution range. Trees may not be able to adapt because of their long reproductive cycles hence their potentialities of migration is decisive. Past tree migration rates, during Holocene, were revised in downward these rates (several decameters against several hundred m/year). In this context, and focusing on silver fir (Abies alba Mill.) as “model species”, we studied main factors decisive for migration potentialities. Using regeneration plots, installed on Mont Ventoux north face, silver fir dispersal and seedling recruitment have been studied, including seed sources and main environmental characteristics. Dispersal was also estimated using genetic data. For both cases, dispersal distances are of the order of decameters. This species shows a mixed mating system, and auto-fertilization rate, plus reproduction between half-sibs, induces homozygosity excess, generally observed in regeneration, this excess decreases probably under the purge of inbred individuals. Our results show that seedlings do not have show homozygosity excess, however inbred seedlings die preferentially. Lastly, we constructed a model of forest dynamics that includes processes that determine migration, in order to evaluate the concordance between long life cycle species and CC. Our results show that silver fir does not migrate as fast as climate warming velocity.

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Disturbance in a forest’s canopy, whether caused by treefall, limbfall, landslide, or fire determines not only the distribution of well-lit patches at any given time, but also the ways in which the forest changes over time. In this dissertation, I use a 25 year record of treefall gap formation find a novel and highly patterned process of forest disturbance and regeneration, providing a local mechanism by examining the factors that influence the likelihood of treefall. I then develop a stochastic cellular automaton for disturbance and regeneration based on the analysis of this long term data set and illustrate the potential of this model for the prediction and detection of patterned forest dynamics in general. Finally, I investigate the spatial structure of a population of one of the most common gap colonist species in this forest, Didymopanax pittieri, and illustrate the effect of local aggregation of treefalls and on the population dynamics of D. pittieri in the process.

No description available.

No description available.

The objectives of this study were to determine the loading of dead and down forest fuels in 6 forest cover types on the upper Coastal Plain of Virginia, specifically in the Richmond National Battlefield Park, and to determine the relationships between the fuels and the vegetation. The forest fuels and vegetation were sampled in stands of the following cover types: pine, oak-pine, mixed hardwood-pine, oak, mixed hardwood, and oak-mixed hardwood. The planar intersect method was utilized to quantify the woody fuels. and the forest floor was sampled in fixed area plots. The weight. volume, depth. and species of fuel particles was determined for each stand sampled in the Park, and this information was combined for an estimate of fuel loading by cover type. The overstory trees were sampled within prism plots, and the understory was sampled in fixed area plots. Standard forestry information was collected for each sampled stand, and estimates of species dominance, density, frequency and importance were determined. In general, the fuel loading was not different between the six cover types as determined with ANOVA procedures. due to the large variation of loads within each. The loading of certain sizes of fuel particles were different between a few cover types, due to both the influence of the overstory species and the site they had occupied. For example, the 1-hr. time-lag branch fuel loading was significantly greater in the oak cover type than in the pine or mixed hardwood cover types. Another significant difference was in the forest floor loads: the mixed hardwood cover type had a lighter forest floor than the pine or oak-pine cover types. This was most likely due to the higher quality of sites upon which the mixed hardwood stand were found, and the higher palatability of litter produced by these species, which would favor the decomposition of litter more than conditions found in the pine or oak-pine cover types. To quantify relationships between the fuel loads and forest vegetation and site characteristics, Spearman's rank correlation coefficients were calculated between all the variables. Many significant relationships were found, though all but one correlation coefficient was under 0.51: total forest floor load and forest floor depth had a correlation coefficient of 0.75. Forest and site variables significantly related to fuel loadings were tested for their predictive value with multiple regression statistics. The resulting set of regressions had low coefficients of determination and varying levels of precision; their usefulness would depend on the level of sampling intensity and precision one would want to expend to get an estimate of fuel loading in a stand. If a rough estimate requiring little time in the field is desirable, then these regressions would be useful. / Master of Science

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No description available.