Submitted by LUIS RENATO JUNQUEIRA null (lrenatoj2@yahoo.com.br) on 2016-10-20T02:48:44Z No. of bitstreams: 1 Dissert_LRJ_corrigida.pdf: 5636293 bytes, checksum: 259084ad9da1cc625f5f79130569e026 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-10-20T19:36:38Z (GMT) No. of bitstreams: 1 junqueira_lr_me_bot.pdf: 5636293 bytes, checksum: 259084ad9da1cc625f5f79130569e026 (MD5) / Made available in DSpace on 2016-10-20T19:36:38Z (GMT). No. of bitstreams: 1 junqueira_lr_me_bot.pdf: 5636293 bytes, checksum: 259084ad9da1cc625f5f79130569e026 (MD5) Previous issue date: 2016-08-25 / Introduzido no início do século XX, o eucalipto, se adaptou bem a diversos locais no Brasil, sendo hoje o gênero florestal mais plantado no país. Dentre suas inúmeras utilizações, destacam-se a produção de celulose, papel, carvão e chapas de fibras. Desde o início dos anos 2000 houve a introdução de pragas exóticas, que devido à ausência competição e controle natural e presença de alimento e clima apropriados, tornaram-se problemas para os cultivos de eucalipto. Dentre as pragas introduzidas no país, destaca-se o percevejo bronzeado do eucalipto, Thaumastocoris peregrinus. Esta espécie teve sua detecção no Brasil em 2008 e desde então já atacou mais de 500 mil hectares de florestas. Contudo, ainda não existem informações consolidadas sobre as perdas ocasionas pelo seu ataque. Os objetivos deste trabalho foram quantificar a perda em produção de madeira causada por T. peregrinus sob duas situações: (1) utilizando-se como hospedeiro um mesmo clone em duas idades diferentes e (2) utilizando-se dois clones de eucalipto distintos em uma mesma idade. Para isolar o ataque de T. peregrinus os ensaios foram conduzidos em parcelas pareadas com aplicação de calda inseticida para proteger algumas parcelas de seu ataque. Para quantificar o impacto do ataque por T. peregrinus foram contados o número de insetos em folhas e armadilhas, mensuradas o crescimento em diâmetro e altura das árvores com posterior cálculo de volume. Os resultados mostraram redução em diâmetro, altura e volume devido ao ataque de T. peregrinus, com a técnica de aplicação de inseticidas pulverizados sendo mais eficiente que o método de drench. Como conclusões a perda potencial causada por T. peregrinus levando-se em consideração apenas um pico populacional da praga foi de R$ 1,4 mil/hectare. / Introduced in the early twentieth century, eucalypt has adapted well to different locations in Brazil, being the most planted genus in the country. Among its many uses, it highlights the production of pulp, paper, coal and fiberboard. Since early 2000s the introduction of exotic pests which encountered no competition or natural enemies and presence of food and suitable climate have become pests for eucalypt plantations. Among the main pests introduced in Brazil is the bronze bug, Thaumastocoris peregrinus. Its first detection in Brazil was in 2008 and since then it has attacked more than 500 thousands hectares of eucalypt forest. However, there are no consolidated information about growth losses caused by its attack. The objectives of this study were to quantify the loss in wood production caused by T. peregrinus in two situations: (1) using as a host the same material in two different ages and (2) using two different Eucalyptus materials in the same age. To isolate T. peregrinus attack the experiment were conducted in twin plots with insecticide spraying to protect trees from T. peregrinus attack. To quantify the impact caused by T. peregrinus attack the number of insects were counted on leaves and traps, the growth on diameter and height of trees were measured for subsequent volume calculation. The results showed a reduction in diameter, height and volume due to the attack of T. peregrinus. Insecticide spraying method got better results than drench method. As conclusions the potential loss caused by T. peregrinus taking into consideration only one pest outbreak was R$ 1.400, 00/ hectare.

Orientador: Carlos Frederico Wilcken / Banca: Leonardo Rodrugues Barbosa / Banca: Everton Pires Soliman / Resumo: Introduzido no início do século XX, o eucalipto, se adaptou bem a diversos locais no Brasil, sendo hoje o gênero florestal mais plantado no país. Dentre suas inúmeras utilizações, destacam-se a produção de celulose, papel, carvão e chapas de fibras. Desde o início dos anos 2000 houve a introdução de pragas exóticas, que devido à ausência competição e controle natural e presença de alimento e clima apropriados, tornaram-se problemas para os cultivos de eucalipto. Dentre as pragas introduzidas no país, destaca-se o percevejo bronzeado do eucalipto, Thaumastocoris peregrinus. Esta espécie teve sua detecção no Brasil em 2008 e desde então já atacou mais de 500 mil hectares de florestas. Contudo, ainda não existem informações consolidadas sobre as perdas ocasionas pelo seu ataque. Os objetivos deste trabalho foram quantificar a perda em produção de madeira causada por T. peregrinus sob duas situações: (1) utilizando-se como hospedeiro um mesmo clone em duas idades diferentes e (2) utilizando-se dois clones de eucalipto distintos em uma mesma idade. Para isolar o ataque de T. peregrinus os ensaios foram conduzidos em parcelas pareadas com aplicação de calda inseticida para proteger algumas parcelas de seu ataque. Para quantificar o impacto do ataque por T. peregrinus foram contados o número de insetos em folhas e armadilhas, mensuradas o crescimento em diâmetro e altura das árvores com posterior cálculo de volume. Os resultados mostraram redução em diâmetro, altura e volume devido ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Introduced in the early twentieth century, eucalypt has adapted well to different locations in Brazil, being the most planted genus in the country. Among its many uses, it highlights the production of pulp, paper, coal and fiberboard. Since early 2000s the introduction of exotic pests which encountered no competition or natural enemies and presence of food and suitable climate have become pests for eucalypt plantations. Among the main pests introduced in Brazil is the bronze bug, Thaumastocoris peregrinus. Its first detection in Brazil was in 2008 and since then it has attacked more than 500 thousands hectares of eucalypt forest. However, there are no consolidated information about growth losses caused by its attack. The objectives of this study were to quantify the loss in wood production caused by T. peregrinus in two situations: (1) using as a host the same material in two different ages and (2) using two different Eucalyptus materials in the same age. To isolate T. peregrinus attack the experiment were conducted in twin plots with insecticide spraying to protect trees from T. peregrinus attack. To quantify the impact caused by T. peregrinus attack the number of insects were counted on leaves and traps, the growth on diameter and height of trees were measured for subsequent volume calculation. The results showed a reduction in diameter, height and volume due to the attack of T. peregrinus. Insecticide spraying method got better results than drench method. As conclusions the potential loss caused by T. peregrinus taking ... / Mestre

O estudo teve por objetivo verificar se existe um gradiente de estresse nutricional entre fisionomias distintas na ARIE Pé-de-Gigante e verificar se às plantas de cerrado podem ser aplicadas (1) a hipótese da disponibilidade de recursos (Coley et al., 1985), segundo a qual plantas em ambientes com menos recursos investem mais em defesas e (2) a hipótese de que plantas sob estresse abiótico tornam-se mais susceptíveis a insetos herbívoros (Rhoades, 1979; White, 1969, 1984). Além disso, pretendeu-se verificar a composição da fauna de insetos herbívoros e de predadores e parasitóides associadas à planta. Foram comparados os padrões de herbivoria foliar, bem como a fauna de insetos herbívoros e de predadores e parasitóides associada a Didymopanax vinosum E. March. em fisionomias de campo cerrado, cerrado e cerradão, relacionando-os com possíveis variações nutritivas, da dureza foliar e dos teores de celulose, ligninas e taninos. Foi constatado que as folhas jovens de D. vinosum possuem maior conteúdo de água e nitrogênio, menor dureza e menores teores de celulose, ligninas e taninos. As análises de solo não apontaram diferenças entre as áreas em termos de composição química, indicando a ausência de um gradiente de estresse nutricional. No entanto, as plantas do cerrado e do cerradão apresentaram folhas mais ricas em água e nitrogênio e menor dureza que as plantas do campo cerrado. As plantas das duas primeiras áreas investem mais em taninos e menos em ligninas, os principais tipos de defesas quantitativas. Outros fatores abióticos podem exercer grande influência nas concentrações destes compostos, como a luminosidade, cuja deficiência parece colocar as plantas do sub-bosque do cerrado e do cerradão em situação de estresse. Desse modo, a hipótese 1 aplica-se a D. vinosum apenas quando se considera o investimento em taninos, mas não em ligninas. A herbivoria por insetos mastigadores foi muito baixa tanto em folhas jovens quanto em adultas (inferior a 2 e 5%, respectivamente). Em folhas adultas, foi maior apenas no cerradão, corroborando parcialmente a hipótese 2. Por outro lado, a herbivoria por insetos sugadores em folhas jovens foi intensa, principalmente no campo cerrado e no cerradão, sendo Lyothrips didymopanacis (Thysanoptera) a principal espécie responsável pelos danos foliares. As populações desta espécie demonstraram ser influenciadas primariamente pela disponibilidade de folhas jovens da planta. Populações de aranhas e coccinelídeos acompanharam parcialmente as flutuações das populações de L. didymopanacis. / This study aimed at verifying the existence of a nutritional stress gradient among distinct physiognomies at Pé-de-Gigante Relevant Ecological Interest Area (ARIE), and in such case, verifying whether the following hypotheses can be applied to cerrado plants: (1) the resource availability hypothesis (Coley et al., 1985), according to which plants in environments with fewer resources invest more in defence strategies, and (2) the hypothesis stating that plants under abiotic stress become more susceptible to herbivorous insects (Rhoades, 1979; White, 1969, 1984). In addition, the study also aimed at verifying the composition of the herbivorous insects fauna as well as those of predators and parasitoids associated with the plant. The leaf herbivory standards were compared and so were the faunas of herbivorous insects, predators and parasitoids associated with Didymopanax vinosum E. March in physiognomies of “campo cerrado”, “cerrado” and “cerradão”. Such standards were then related to possible variations in leaf nutrition, toughness and levels of cellulose, lignins and tannins. It was observed that young leaves of D. vinosum had more water and nitrogen content, less hardness and smaller levels of cellulose, lignins and tannins. Soil analyses did not show differences among the areas as to chemical composition, which indicates the absence of a nutritional stress gradient. However, cerrado and cerradão plants presented leaves with greater water and nitrogen contents as well as less toughness than campo cerrado plants. The plants in the two first areas invested more in tannins and less in lignins, which are the two major types of quantitative defences. Other abiotic factors can exert great influence on the concentration of these compounds, such as luminosity, whose deficiency seems to place cerrado and cerradão understory plants in a stressing situation. Therefore, hypothesis 1 applies to D. vinosum only when the investment in tannins is taken into account, but not that in lignins. Herbivory in chewer insects was low both in young and adult leaves (lower than 2 and 5%, respectively). As to adult leaves, it was higher only in cerradão, which partly supports hypothesis 2. On the other hand, herbivory by sucking insects on young leaves was intense, especially in campo cerrado and cerradão where Lyothrips didymopanacis (Thysanoptera) was the mainly responsible species for leaf damage. This species’ population showed to be primarily influenced by the availability of the plant’s young leaves. Populations of spiders and Coccinelideae partly followed L. didymonopacis population flows.

Submitted by dayse paz (daysepaz@hotmail.com) on 2016-04-06T12:26:42Z No. of bitstreams: 1 Trabalho_de_dissertao__kelen_veiga.pdf: 657170 bytes, checksum: 52dae3899c44e07081a8da2ebe09a390 (MD5) / Approved for entry into archive by cleuza maria medina dos santos (cleuzamai@yahoo.com.br) on 2016-04-06T23:51:01Z (GMT) No. of bitstreams: 1 Trabalho_de_dissertao__kelen_veiga.pdf: 657170 bytes, checksum: 52dae3899c44e07081a8da2ebe09a390 (MD5) / Made available in DSpace on 2016-04-06T23:51:01Z (GMT). No. of bitstreams: 1 Trabalho_de_dissertao__kelen_veiga.pdf: 657170 bytes, checksum: 52dae3899c44e07081a8da2ebe09a390 (MD5) Previous issue date: 2013 / O gênero Cavia pertence à família Caviidae. No Rio Grande do Sul são encontradas as espécies C. aperea e C. magna, sendo a última ocorrente na Ilha dos Marinheiros, local onde foi realizado este estudo. A disponibilidade de alimentos no ambiente é importante para o desenvolvimento da espécie. Assim, o objetivo desse estudo foi determinar preferência alimentar de Cavia magna, relacionando as espécies vegetais encontradas na dieta com suas disponibilidades no ambiente. Foram realizadas sazonalmente, no período de um ano, coletas e levantamento da vegetação, estimando a cobertura de cada espécie para posteriormente calcular o Índice de valor de importância (IVI). Mensalmente, nesse mesmo período, foram coletadas amostras de fezes dos preás, para análise micro-histológica, técnica esta amplamente utilizada para determinação da dieta de herbívoros. Os dados foram coletados em dois transectos, um ao Norte e outro ao Sul da Ilha em 30 unidades amostrais de 1m², cada. Testes MANOVA e de Mantel foram realizados para determinar a relação entre a distribuição e abundância das espécies vegetais no ambiente, e as espécies encontradas nas amostras fecais. No ambiente foram registradas 96 espécies distribuídas em 44 famílias durante os períodos amostrados, sendo Asteraceae, Poaceae e Cyperaceae as mais representativas. Juncus acutus apresentou maior Índice de Valor de Importância (IVI) na área Norte nos quatro períodos estudados e no verão e outono na área Sul. Cladium jamaicense e Plantago australis tiveram maior IVI nos períodos de inverno e primavera, respectivamente. Nas amostras fecais foram identificadas 24 espécies vegetais pertencentes a 19 famílias. Poaceae foi a família com maior número de espécies frequente na dieta para ambas as áreas. Na área Norte, Hypoxis decumbens e Juncus acutus foram as espécies de maior frequência nas amostras de fezes, enquanto que na área Sul, a espécie mais frequente foi Paspaum urvillei. Os testes MANOVA demonstraram variabilidade de espécies tanto no ambiente quanto nas amostras de fezes, no que se refere às estações do ano. O teste de Mantel mostrou influência significativa entre a disponibilidade da vegetação e as espécies consumidas pelo preá, porém com baixa correlação. As espécies mais consumidas foram buscadas por C. magna em maiores distâncias, ou selecionadas, mesmo quando ofertadas em menores quantidades no ambiente, demonstrando seletividade e preferência deste roedor por algumas espécies vegetais no presente estudo. / The Genus Cavia belongs to the family Caviidae. In Rio Grande do Sul are found the species C. aperea and C. magna, the last occurring on the Marinheiros Island, where the study was conducted. The availability of food in the environment is crucial for the development of the species. The objective of this study was to determine the feeding preference of Cavia magna listing the plant species found in the diet with their availability in the environment. Were conducted seasonally, during one year, sampling and survey of vegetation, estimating the coverage of each species to subsequently calculate the importance value index (IVI). Monthly, during the same period, samples of cavies’s feces were collected for microhistological analysis, this technique is widely used to determine the diet of herbivores. Data were collected in two transects, one North and the other South of the island in 30 sampling units of 1m² each. MANOVA and Mantel’s Test was conducted to determine the relationship between the abundance and distribution in the environment of the plant species and species found in fecal samples. The environment has been recorded 96 species in 44 families in the sample periods, and Asteraceae, Poaceae and Cyperaceae were the most representative. Juncus acutus showed greater Importance Value Index (IVI) in the North area in the four periods and during summer and autumn, in the South area. Cladium jamaicense and Plantago australis had higher IVI during winter and spring, respectively. In fecal samples were identified 24 plant species belonging to 19 families. Poaceae was the family with the highest number of species in the diet for both areas. In the North, Hypoxis decumbens and Juncus acutus were the species most frequently in stool samples, while in the South, the most frequent was Paspaum urvillei. MANOVA tests demonstrate that there is both species variability in the environment and in the feces sample, with respect to seasons. The Mantel test showed significant influence between the availability of vegetation and species consumed by cavy, but with low correlation. The most consumed species were sought by C. magna at greater distances, or selected, even when offered in smaller quantities in the environment, demonstrating selectivity and preference of this rodent by some vegetal species in this study

A perda de área foliar, em sua maior parte resultante da ação de herbívoros, é um dos fatores que regulam o sucesso reprodutivo de uma planta e indiretamente de todos os consumidores relacionados na comunidade. A maior parte dos estudos feitos com perda foliar e herbivoria são pontuais, ou seja, referem-se a uma ou poucas espécies vegetais. Para os cerrados, a savana tropical brasileira, a maior savana em extensão e diversidade no mundo, não há nenhum estudo que investigue a dinâmica de perda de área foliar ao longo do tempo na comunidade, considerando os fatores climáticos e fenológicos que podem influenciar este processo, além da presença dos principais predadores de herbívoros atrópodes na vegetação de cerrado, as formigas, sendo este o principal objetivo do presente estudo. O estudo foi desenvolvido em uma área de reserva de Cerrado de 628 ha, situada em Uberlândia, MG (18º59S, 48º18O), tendo os dados sido coletados de janeiro a dezembro de 2007 (bimestralmente) e de 2008 (mensalmente). Foram estabelecidos aleatoriamente na área de cerrado sensu stricto da reserva, 15 quadrantes de 10m x 10m onde todos os indivíduos com diâmetro à altura do peito igual ou superior a três centímetros foram marcados e incluídos na amostra. Em cada quadrante observou-se (sem remoção), seis folhas (escolhidas aleatoriamente duas da parte alta, duas da parte mediana e duas de ramos mais baixos), por planta de cada espécie, sendo registrada a porcentagem de área foliar perdida. Foram amostrados um total de 1006 indivíduos distribuídos em 82 espécies e 34 famílias. A espécie Ouratea spectabilis (137 indivíduos) foi a mais abundante na área de estudo, seguida de Banisteriopsis malifolia (122), Machaerium acutifolium (59) e Tabebuia ochracea (41). A perda de área foliar variou significativamente ao longo do tempo (meses) e entre as famílias e espécies de plantas. Os meses mais secos do ano apresentaram a maior perda de área foliar tanto em 2007 (abril, junho e agosto) quanto em 2008 (de maio a agosto). Os fatores climáticos influenciaram significativamente a perda de área foliar, pois ela variou ao longo do tempo. Portanto, os resultados do presente estudo indicaram que a perda de área foliar da comunidade de plantas de cerrado varia sazonalmente e ocorre com maior intensidade na estação seca. Fatores abióticos como temperatura e precipitação influenciam a fenologia das espécies de plantas, que buscam o melhor momento para maximizar seu desenvolvimento e evitar que inimigos naturais causem perdas significativas para sua sobrevivência e sucesso reprodutivo. As características de cada espécie promovem diferenças na perda de área foliar, devido às defesas e/ou associações mutualísticas que possuem. A presença de nectários extraflorais associados às formigas desempenha um papel significativo para as plantas. Dentre os fatores bióticos, a presença de ninhos de formigas Ectatomma teve um impacto positivo para as plantas reduzindo a perda de área foliar. / The loss of leaf area, mostly resulting from the action of herbivores is one of the factors that regulate the reproductive success of a plant and indirectly to all consumers connected to the community. Most studies of herbivory and leaf loss are punctual, i.e., refer to one or a few plant species. In the cerrado, a tropical savanna in Brazil, the largest savanna in scope and diversity in the world, there are no studies to investigate the dynamics of loss of leaf area over time in the community, considering the climatic factors, phenology and carnivorous ants that can influence this process, which is the main objective of this study. The study was conducted in a closed area of 628 ha of Cerrado, located in Uberlandia, Brazil (18 º 59\'S, 48 18\'W) and the data were collected from January to December 2007 (bimonthly) and 2008 (monthly). Were established randomly in the area of cerrado of the reserve, 15 quarters of 10m x 10m where all trees with diameter at breast height greater than or equal to three centimeters were marked with numbered label and sampled. In each quadrant was observed (without removal), six leaves (randomly chosen two of high part, two of the middle, and two of the lower branches), in plant species, and recorded the percentage of leaf area lost. We sampled a total of 1006 individuals belonging to 82 species and 34 families. The species Ouratea spectabilis (137 individuals) was the most abundant in the study area, followed by Banisteriopsis malifolia (122), Machaerium acutifolium (59) and Tabebuia ochracea (41). The loss of leaf area varied significantly over time (months) and between families and species of plants. The driest months of the year showed the greatest loss of leaf area in both 2007 (April, June and August) and in 2008 (May-August). Climatic factors also significantly influenced the loss of leaf area, as it varied over time, depending on the rainfall and temperature variation. Therefore, the results of this study indicated that the loss of leaf area community of cerrado plants varies seasonally and occurs mostly in the dry season. Abiotic factors like temperature and rainfall influence the phenology of species of plants, seeking the best time to maximize their development and prevent natural enemies result in significant losses for their survival and reproductive success. The characteristics of each species promote differences in leaf area loss due to defenses and / or mutualistic associations they have. The presence of extrafloral nectaries associated with ants play a significant role for plants. For this reason, among the biotic factors, the presence of Ectatomma nests had a significant positive impact on reducing the loss of leaf area, since these ants are predators of herbivores.

Abstract In northernmost Fennoscandia, grazing by reindeer (Rangifer tarandus L.) has a substantial impact on the vegetation of boreal forests and arctic-alpine tundra heaths, which are reflected in below-ground processes, such as nutrient mineralization and soil organic matter decomposition. In the present thesis, the effects of reindeer grazing on soil nutrient cycling were studied by comparing grazed situation with an ungrazed control area in ten boreal forests and six arctic-alpine tundra heaths. In boreal forests, reindeer grazing reduced microbial respiration in both the oligotrophic and mesotrophic study areas, indicating a deficiency of labile substrates for the soil microbes due to reindeer grazing. Simultaneously, there was heterogeneity in the impact on nitrogen mineralization rates as at some sites, mineralization was enhanced by grazing. The fertilization effect of urine and faeces can therefore be strong enough a factor to outweigh a reduction in quality of soil organic matter. In the oligotrophic forests, low soil moisture content in the grazed areas could sometimes limit the mineralization rates even when the potential for mineralization was enhanced by grazing. In the tundra ecosystems, there was spatial variation in the impact of grazing on microbial respiration and nitrogen mineralization. Low grazing intensity occurring outside the growing season had a retarding impact on nutrient cycling in both unfertilized, nutrient-poor and fertilized, nutrient-rich conditions. In contrast, a relatively high grazing intensity enhanced the mineralization rates in two nutrient-poor and two nutrient-rich tundra heaths. When three different grazing intensities were compared in one oceanic, nutrient-rich and one continental, nutrient-poor tundra heath, the strongest positive effect of grazing on soil nutrient cycling occurred in the heavily grazed areas. The data do not support the assumption that soil nutrient availability regulates whether herbivores enhance or retard nutrient cycling in the soil. Instead, the net effect of grazing is determined by the balance between the underlying mechanisms that may work at opposite directions. The most important of these mechanisms are the grazer-mediated impact on the decomposability of the dominant vegetation and fertilization by urine and faeces. The duration, intensity and seasonal timing of the grazing seem to be important factors that regulate whether reindeer grazing enhances or retards soil nutrient cycling in each specific area. Due to the high spatial and temporal variation in the effects of grazing observed in this study, it is not possible to generalize the overall impact of grazing. Further study is required in order to determine the exact conditions under which grazing enhances or it retards soil nutrient cycling.

Abstract This thesis operates at two levels of ecological research, describing the effects of withdrawal and re-introduction of management on grasslands. The aim of the community-level survey was to explore the effects of abandonment, mowing and grazing on semi-natural meadows in northern Finland. At the species level, the aim was to evaluate the responses of three monocarpic meadow species to various degrees of simulated grazing under natural growth conditions. The community-level studies suggest that strongly competitive grass species with rapid vegetative growth, especially those forming tussocks, are able to retain or increase their cover in abandoned meadows. However, most species are able to persist in a meadow for a long time after abandonment, even when a group of immigrants arrive. This leads to a temporary increase in species diversity, and it may therefore be used as an indicator of ongoing succession. Nevertheless, abandonment is harmful for the rare archaeophytic species in the long run. Late mowing does not have extensive short-term impacts on grass-dominated semi-natural meadows. Therefore, it is neither an efficient nor a substitutional way of management when the goal is to restore a formerly grazed pasture. Mowing executed early in the season may, however, be a more appropriate way of inducing changes in species composition and enhancing species richness. According to the results of the species-level studies, Erysimum strictum and Rhinanthus minor tolerate well minor apical damage, while more severe damage has a detrimental impact on the performance of both species. The observed differences in regrowth responses between the two species are presumably due to their different habitat requirements in relation to competition. The species-level experiment with two late-flowering populations of field gentian Gentianella campestris ssp. campestris revealed that the southern, Swedish population that has been regularly grazed and mown overcompensated for the intermediate (50%) damage level, whereas the northern, Finnish field gentians growing in unmanaged habitats showed at best partial or full compensation. Regular grazing and mowing have presumably favoured grazing-tolerant plant species, i.e. species with a good regrowth capacity. Herbivory reshapes grassland plant communities in two ways: directly by affecting the survival and reproductive success of individual plants and indirectly by changing the competitive environment. Tall and competitive perennial species suffer relatively more from damage than true grassland species, i.e. small herbs and grasses, which are better able to tolerate regular tissue losses and respond to damage within the ongoing growing season. As a result, certain species benefit from grazing and mowing in the sense that they may gain more through competitive relaxation than they lose in defoliation.

Rising temperatures associated with climate change will alter the fundamental physiological processes of most ectothermic species. Drastic changes in catabolic and anabolic reaction rates exert strong effects on growth, reproduction, and consumption rates that cascade up through all levels of the biological hierarchy. This dissertation determined how climate warming might alter the important relationship between plants and insect herbivores, as mediated through changes in herbivore physiology. Consumption and fitness increased with temperature for almost all consumers. However, all consumers also exhibited a critical temperature, beyond which consumption declined rapidly through metabolism continued to increase. This mismatch in metabolic demands and energy intake reduced consumer fitness at high temperatures. Furthermore, increased metabolic nitrogen demand can induce nitrogen limitation in insect herbivores at high temperatures. These basic physiological changes can modify the way herbivores interact with plants in a number of ways. For example, the Japanese beetle, Popillia japonica, altered its feeding behavior on numerous host plant species, depending on host plant quality. Unfortunately, the effects of temperature on plant-herbivore interactions will be difficult to predict, as there was no predictable relationship between consumption and temperature across numerous plant-herbivore pairs. Finally, rising temperatures disrupt insect herbivore control of plant fitness, thereby altering one of the most important components of plant-herbivore interactions. Thus, climate change will fundamentally change the nature of plant-herbivore interactions in the future.

Himatanthus tarapotensis (Apocynaceae) connu au Pérou comme "bellaco caspi", est un arbre répandu dans plusieurs types d’habitat de l’Amazonie péruvienne où il est très utilisé en médicine traditionnelle pour le traitement de certaines maladies. Les propriétés médicinales des espèces de Himatanthus sont liées notamment à la présence du terpène bioactif pluméricine. Le potentiel pharmacologique de la pluméricine et le succès reproductif de H. tarapotensis ont mené à la réalisation de cette étude afin d’explorer les patrons de production de ce composé le long des variations des gradients environnementaux déterminés par les différents types d’habitat où la plante pousse naturellement. Cependant, il existe une confusion autour de la délimitation des espèces du genre Himatanthus qui pousseraient au Pérou et les noms scientifiques qui doivent être utilisés. En conséquent une partie de cette étude a consisté en l’évaluation taxonomique du genre Himatanthus. Dans la première partie de la thèse est présentée une révision synoptique des espèces de Himatanthus de l'Amazonie péruvienne, avec la finalité d'introduire une stabilité taxonomique de ces espèces au Pérou. Trois espèces de Himatanthus se trouvent au Pérou : H. tarapotensis, H. phagedaenicus et H. revolutus, distinguées entre eux notamment par des traits reproductifs. Dans la seconde partie, les feuilles d’individus juvéniles de H. tarapotensis qui se développent sur deux types d’habitat ont été prélevées pour évaluer la production de pluméricine en fonction des facteurs environnementaux : type de sol, période de précipitations, et pression des insectes en tenant compte de la croissance de la plante. La production de pluméricine chez H. tarapotensis ne montre pas différences significatives en fonction des types de sol. Mais, il a été observé une variation temporelle de la concentration du composé corrélée positivement avec la pression des insectes, notamment avec la larve herbivore Isognathus leachii (Lepidoptera : Sphingidae) et négativement avec la croissance. En même temps, ces deux facteurs ont été corrélés avec la précipitation, ce qui suggère que l’intensité de pluie influencerait la production de pluméricine de manière indirecte. Le composé bioactif pluméricine pourrait avoir un patron de production déterminé par son rôle médiateur des interactions de H. tarapotensis avec son environnement. / Himatanthus tarapotensis (Apocynaceae) known in Peru as "bellaco caspi", is a common tree from several habitats in the Peruvian Amazon, where is widely used in traditional medicine for the treatment of various diseases. Medicinal properties from species of Himatanthus have been mainly related to the presence of a bioactive terpene plumericin. The pharmacological potential of plumericin and reproductive success of H. tarapotensis gave rise to the present study to explore the production patterns of this compound in function of environmental gradients determined by the different habitat types where this species grows in nature. However, the delimitation of Himatanthus species has long been problematic, and much confusion remains as to which names should be used and which species delimitations should be adopted. Consequently, a part of this study was dedicated to a taxonomic revision of Himatanthus species occurring in Peru. Therefore, in chapter 1 is presented a synoptic revision of Himatanthus species from the Peruvian Amazon, with the aim of introducing taxonomic stability of those species in Peru. Three species of Himatanthus are present in Peru: H. tarapotensis, H. phagedaenicus and H. revolutus, distinguished among themselves mainly by reproductive traits. In chapter 2, leaves collected from juvenile individuals of H. tarapotensis growing on two Amazonian habitats were used to evaluate the plumericin production in relation to environmental factors: soil type, period of precipitation, and insects pressure, keeping in mind their relation with the growth patterns of the plant. Plumericin production in H. tarapotensis was not affected by differences in soil types. However, it was observed a temporal variation in the concentration of this compound correlated positively to the insects pressure, mainly with the herbivorous larva of Isognathus leachii (Lepidoptera: Sphingidae) and negatively to the growth pattern of the plant. These two factors were correlated to the rainfall, thus suggesting that precipitation would be affecting indirectly on plumericin production. The bioactive compound plumericin would have a production pattern determined by its mediator role in interactions phenomena of H. tarapotensis and its environment.

A perda de área foliar, em sua maior parte resultante da ação de herbívoros, é um dos fatores que regulam o sucesso reprodutivo de uma planta e indiretamente de todos os consumidores relacionados na comunidade. A maior parte dos estudos feitos com perda foliar e herbivoria são pontuais, ou seja, referem-se a uma ou poucas espécies vegetais. Para os cerrados, a savana tropical brasileira, a maior savana em extensão e diversidade no mundo, não há nenhum estudo que investigue a dinâmica de perda de área foliar ao longo do tempo na comunidade, considerando os fatores climáticos e fenológicos que podem influenciar este processo, além da presença dos principais predadores de herbívoros atrópodes na vegetação de cerrado, as formigas, sendo este o principal objetivo do presente estudo. O estudo foi desenvolvido em uma área de reserva de Cerrado de 628 ha, situada em Uberlândia, MG (18º59S, 48º18O), tendo os dados sido coletados de janeiro a dezembro de 2007 (bimestralmente) e de 2008 (mensalmente). Foram estabelecidos aleatoriamente na área de cerrado sensu stricto da reserva, 15 quadrantes de 10m x 10m onde todos os indivíduos com diâmetro à altura do peito igual ou superior a três centímetros foram marcados e incluídos na amostra. Em cada quadrante observou-se (sem remoção), seis folhas (escolhidas aleatoriamente duas da parte alta, duas da parte mediana e duas de ramos mais baixos), por planta de cada espécie, sendo registrada a porcentagem de área foliar perdida. Foram amostrados um total de 1006 indivíduos distribuídos em 82 espécies e 34 famílias. A espécie Ouratea spectabilis (137 indivíduos) foi a mais abundante na área de estudo, seguida de Banisteriopsis malifolia (122), Machaerium acutifolium (59) e Tabebuia ochracea (41). A perda de área foliar variou significativamente ao longo do tempo (meses) e entre as famílias e espécies de plantas. Os meses mais secos do ano apresentaram a maior perda de área foliar tanto em 2007 (abril, junho e agosto) quanto em 2008 (de maio a agosto). Os fatores climáticos influenciaram significativamente a perda de área foliar, pois ela variou ao longo do tempo. Portanto, os resultados do presente estudo indicaram que a perda de área foliar da comunidade de plantas de cerrado varia sazonalmente e ocorre com maior intensidade na estação seca. Fatores abióticos como temperatura e precipitação influenciam a fenologia das espécies de plantas, que buscam o melhor momento para maximizar seu desenvolvimento e evitar que inimigos naturais causem perdas significativas para sua sobrevivência e sucesso reprodutivo. As características de cada espécie promovem diferenças na perda de área foliar, devido às defesas e/ou associações mutualísticas que possuem. A presença de nectários extraflorais associados às formigas desempenha um papel significativo para as plantas. Dentre os fatores bióticos, a presença de ninhos de formigas Ectatomma teve um impacto positivo para as plantas reduzindo a perda de área foliar. / The loss of leaf area, mostly resulting from the action of herbivores is one of the factors that regulate the reproductive success of a plant and indirectly to all consumers connected to the community. Most studies of herbivory and leaf loss are punctual, i.e., refer to one or a few plant species. In the cerrado, a tropical savanna in Brazil, the largest savanna in scope and diversity in the world, there are no studies to investigate the dynamics of loss of leaf area over time in the community, considering the climatic factors, phenology and carnivorous ants that can influence this process, which is the main objective of this study. The study was conducted in a closed area of 628 ha of Cerrado, located in Uberlandia, Brazil (18 º 59\'S, 48 18\'W) and the data were collected from January to December 2007 (bimonthly) and 2008 (monthly). Were established randomly in the area of cerrado of the reserve, 15 quarters of 10m x 10m where all trees with diameter at breast height greater than or equal to three centimeters were marked with numbered label and sampled. In each quadrant was observed (without removal), six leaves (randomly chosen two of high part, two of the middle, and two of the lower branches), in plant species, and recorded the percentage of leaf area lost. We sampled a total of 1006 individuals belonging to 82 species and 34 families. The species Ouratea spectabilis (137 individuals) was the most abundant in the study area, followed by Banisteriopsis malifolia (122), Machaerium acutifolium (59) and Tabebuia ochracea (41). The loss of leaf area varied significantly over time (months) and between families and species of plants. The driest months of the year showed the greatest loss of leaf area in both 2007 (April, June and August) and in 2008 (May-August). Climatic factors also significantly influenced the loss of leaf area, as it varied over time, depending on the rainfall and temperature variation. Therefore, the results of this study indicated that the loss of leaf area community of cerrado plants varies seasonally and occurs mostly in the dry season. Abiotic factors like temperature and rainfall influence the phenology of species of plants, seeking the best time to maximize their development and prevent natural enemies result in significant losses for their survival and reproductive success. The characteristics of each species promote differences in leaf area loss due to defenses and / or mutualistic associations they have. The presence of extrafloral nectaries associated with ants play a significant role for plants. For this reason, among the biotic factors, the presence of Ectatomma nests had a significant positive impact on reducing the loss of leaf area, since these ants are predators of herbivores.