The Amazon rain forest plays an important role in regional and global biogeochemical cycling, but the region may undergo an increase in the frequency and severity of drought conditions driven by global climate change, regional deforestation and fire. The effects of this drought on carbon cycling in the Amazon, particularly below-ground, are potentially large but remain poorly understood. This thesis examines the impacts of seasonal and longer-term drought upon ecosystem carbon allocation and cycling at an Amazon rain forest site with a particular focus upon below-ground processes. Measurements are made at three one-hectare forest plots with contrasting soil type and vegetation structure, to observe responses across a range of Amazon primary forest types. A fourth plot is subjected to partial rainfall exclusion to permit measurement of forest responses to a wider range of soil moisture levels than currently exists naturally. An analysis of the number of samples required to accurately quantify important ecosystem carbon stocks and fluxes is used to guide the sampling strategy at the field site. Quantifying root dynamics, in particular, presents methodological challenges. Thus, I critically review existing methods, and develop techniques to accurately measure root standing biomass and production. Subsequently, these techniques are used to record root responses, in terms of standing biomass, production, morphology, turnover and nutrient content, to variation in soil moisture across the four rain forest plots. There is substantial environmental variation in root characteristics. However, several responses remain consistent across plots: root production of biomass, length, and surface area, is lower where soil is dry, while root length and surface area per unit mass show the opposite pattern. The other major component of the below-ground carbon cycle is soil carbon dioxide efflux. I partition this efflux, on each plot, into contributions from organic ground surface litter, roots and soil organic matter, and investigate abiotic and biotic causes for observed differences within and between plots. On average, the percentage contribution of soil organic matter respiration to total soil carbon dioxide efflux declines during the dry season, while root respiration contribution displays the opposite trend. However, spatial patterns in soil respiration are not directly attributable to variation in either soil moisture or temperature. Instead, ground surface organic litter mass and root mass account for 44 % of observed spatial heterogeneity in soil carbon dioxide efflux. Finally, information on below-ground carbon cycling is combined with aboveround data, of canopy dynamics and stem wood production and mortality, to analyze the potential effects of drought upon carbon cycling in an Amazon forest ecosystem. Comparison of the rainfall exclusion plot with a similar, but unmodified, control plot reveals potentially important differences in tree carbon allocation, mortality, reproduction, soil respiration and root dynamics. The apparent net consequence of these changes is that, under drier conditions, the amount of CO2 moving out of the forest and into the atmosphere is diminished. This synthesis of above-ground and below-ground data advances understanding of carbon cycling in rain forests, and provides information which should allow more accurate modelling of the response of the Amazon region to future drought. Additional measurements at other sites, and of other ecosystem carbon fluxes, should further refine modelling predictions.

No description available.

A conservação das áreas remanescentes de Mata Atlântica envolve o desenvolvimento de programas de uso sustentável que requerem um amplo conhecimento da fauna e da flora. Myrtaceae é uma família de grande importância no bioma, sendo dominante em muitos fragmentos, e destaca-se pela produção de óleos voláteis, substâncias com grande potencial de utilização pelas indústrias alimentícia, cosmética e farmacêutica. Considerando-se que a variabilidade de óleos essenciais é pouco conhecida para espécies brasileiras de Myrtaceae, este trabalho teve por objetivo avaliar as alterações destes metabólitos nas folhas algumas destas espécies, em função de aspectos diuturnos, sazonais e de localização geográfica, bem como investigar algumas atividades biológicas. Os óleos foram obtidos por hidrodestlilação e analisados por CG-EM. Os resultados demonstraram uma predominância de compostos sesquiterpênicos para sete das nove espécies estudadas, especialmente espatulenol, β-cariofileno, α-cadinol e ς-elemeno. Entretanto, não foram verificados padrões de variabilidade diuturna ou de sazonalidade para os óleos em nenhuma das espécies alvo, observando-se, porém, alterações na composição entre os diferentes anos de coleta para as espécies Campomanesia guaviroba (DC.) Kiaersk., Myrcia splendens (Sw.) DC., e Myrcia macrocarpa DC. Alterações na composição dos óleos de espécimes coletados em fragmentos distintos foram verificadas em Eugenia cuprea (O. Berg) Nied. e Calyptranthes lucida Mart. Ex DC., porém com inversão, entre as duas espécies, da rota biossintética de sesquiterpenos mais ativa em cada localidade, sugerindo que as variações não são decorrentes de diferenças ambientais. A análise das atividades biológicas demonstrou que os óleos voláteis investigados não apresentam potencial anticolinesterásico, mas possuem potencial para a utilização como antimicrobianos, destacando-se a atividade antifúngica dos óleos de C. guaviroba, M. splendens e M. macrocarpa frente a Cladosporium cladosporioides e C. sphaerospermum. Os resultados obtidos neste trabalho sugerem que os fatores endógenos são mais importantes para a variabilidade dos óleos voláteis nas espécies de Myrtaceae estudadas do que os aspectos ambientais. A ampla variabilidade individual verificada sugere grande diversidade genética para estas espécies, informação fundamental a ser considerada para a definição de estratégias de conservação da Mata Atlântica. / The conservation of the Atlantic Rain Forest remnants involves the development of sustainable use programs that require an extensive knowledge of its flora and fauna. Myrtaceae is an important family in this biome, being dominant in many fragments, and is also recognized by the production of volatile oils, substances with great potential for food, cosmetic and pharmaceutical industries. Considering that there is a lack of scientific information on essential oil variability for Brazilian Myrtaceae species, this work aimed to evaluate the changes of these metabolites in the leaves of some species, considering diurnal and seasonal aspects, and geographical location, as well as to investigate some biological activities. The oils were obtained by hydrodistlillation and analyzed by GC-MS. The results showed a predominance of sesquiterpenes compounds for seven of the nine species studied, especially espatulenol, β-caryophyllene, α-cadinol and ς-elemene. However, no diurnal or seasonal patterns of variability were observed for all target species, but changes in the composition among the analyzed years were found for Campomanesia guaviroba (DC.) Kiaersk., Myrcia splendens (Sw.) DC. and Myrcia macrocarpa DC. Differences in volatile oil composition for specimens collected in different locations were observed for Eugenia cuprea (O. Berg) Nied. and Calyptranthes lucida Mart. Ex DC., but with an inversion, between the two species, of the main sesquiterpene biosynthetic routes acting in each area, suggesting that the variations are not due to environmental differences. The analysis of the biological activities showed that the investigated volatile oils do not exhibit an important anticholinesterasic potential, but rather an antimicrobial one, particularly the antifungal activity of C. guaviroba, M. splendens and M. macrocarpa oils against Cladosporium cladosporioides and C. sphaerospermum. The obtained results suggested that endogenous factors are more important for the volatile oil variability in the studied Myrtaceae species than the environmental aspects. The wide individual variability observed suggests a high genetic diversity for these species, which is an important issue for the establishment of strategies for Atlantic Rain Forest conservation programs.

A Floresta Amazônica, o maior bioma brasileiro, é caracterizado pela ampla diversidade e heterogeneidade de seus ecossistemas. Os solos amazônicos, em geral, abrigam elevada diversidade microbiana que desempenha papeis importantes na ciclagem de nutrientes, mediante a decomposição da matéria orgânica. Dentre os micro-organismos, os fungos se destacam como os principais agentes envolvidos na biodegradação. Esses micro-organismos produzem um coquetel de enzimas do complexo celulolítico que são de grande importância biotecnológica. Desse modo, diante da importância econômica dos fungos, o presente trabalho propôs, acessar fungo do gênero Trichoderma, obtidos de solos da Floresta Amazônica, na busca por linhagens com alto potencial celulolítico. Assim, a partir de amostras de solos coletados em doze pontos da floresta foram obtidos 151 isolados de Trichoderma spp. O sequenciamento do gene que codifica para o de elongação da transcrição alfa-1, evidenciou a prevalência de sete espécies de Trichoderma. Do total de isolados, as mais abundantes foram: Trichoderma spirale (37%), Trichoderma strigosum (22%), Trichoderma harzianum (18%) e Trichoderma asperellum (17%). As linhagens foram submetidas a triagem para atividade celulolítica. Duas linhagens, T. harzianum AMS 23.14 e T. harzianum AMS 29.14 apresentaram atividade enzimática superior ao padrão, T. reesei RUT C-30 e foram submetidas a avaliação da atividade enzimática em diferentes condições de cultivos (bagaço de cana-deaçúcar tratado e não tratado, em dois pHs: 3 e 5). Foi observado atividade superior das linhagens amazônicas para as três enzimas estudadas (endoglucanase, exoglucanase e β-glicosidase), quando comparadas à linhagem padrão utilizada. A atividade enzimática foi positivamente influenciada pelo pH ácido, assim como pelo substrato não tratado. A partir destes resultados é notório que as linhagens isoladas desse bioma possuem grande potencial de atividade celulolítica, e que estudos mais aprofundados podem proporcionar o futuro emprego desses fungos em diversas áreas industriais. / The Amazon Rain Forest, the largest Brazilian biome, is characterized by the wide diversity and heterogeneity of its ecosystems. Amazonian soils, in general, harbor high microbial diversity that plays important roles in the cycling of nutrients, through the decomposition of organic matter. Among the microorganisms, fungi stand out as biodegradation agents. These microorganisms produce cellulolytic enzymes that are of great economic and biotechnological importance. The present work proposed to access the fungal population of the genus Trichoderma, isolated from Amazonian Forest soils, in the search for lineages with high potential of cellulolytic activity. Twelve soil samples were collected, resulting in the isolation of 151 strains of Trichoderma spp. Gene sequencing of the alpha-1 transcription elongation factor region with the EF1 and TEFR primers evidenced the prevalence of seven Trichoderma species. Of the total isolates, Trichoderma spirale (37%), Trichoderma strigosum (22%), Trichoderma harzianum (18%) and Trichoderma asperellum (17%) were the most abundant. The strains were screened for qualitative cellulolytic activity in solid medium and quantitative in liquid medium. Two strains, T. harzianum AMS 23.14 and T. harzianum AMS 29.14 showed enzymatic activity superior to T. reesei RUT C-30, and were sent to the evaluation of the enzymatic activity in different conditions (sugarcane bagasse treated and untreated, in two pHs: 3 and 5). Superior activity of the Amazonian strains was observed for the three enzymes studied (endoglucanase, exoglucanase and β-glucosidase) when compared to the T. reesei RUT C-30 standard. The enzymatic activity was positively influenced by pH 3, as well as by the untreated substrate. From these results, it is well known that isolated strains of the Amazonian environment have a great potential for cellulolytic activity, and that further studies may provide the future employment of these strains in several areas of industry.

A Floresta Amazônica, o maior bioma brasileiro, é caracterizado pela ampla diversidade e heterogeneidade de seus ecossistemas. Os solos amazônicos, em geral, abrigam elevada diversidade microbiana que desempenha papeis importantes na ciclagem de nutrientes, mediante a decomposição da matéria orgânica. Dentre os micro-organismos, os fungos se destacam como os principais agentes envolvidos na biodegradação. Esses micro-organismos produzem um coquetel de enzimas do complexo celulolítico que são de grande importância biotecnológica. Desse modo, diante da importância econômica dos fungos, o presente trabalho propôs, acessar fungo do gênero Trichoderma, obtidos de solos da Floresta Amazônica, na busca por linhagens com alto potencial celulolítico. Assim, a partir de amostras de solos coletados em doze pontos da floresta foram obtidos 151 isolados de Trichoderma spp. O sequenciamento do gene que codifica para o de elongação da transcrição alfa-1, evidenciou a prevalência de sete espécies de Trichoderma. Do total de isolados, as mais abundantes foram: Trichoderma spirale (37%), Trichoderma strigosum (22%), Trichoderma harzianum (18%) e Trichoderma asperellum (17%). As linhagens foram submetidas a triagem para atividade celulolítica. Duas linhagens, T. harzianum AMS 23.14 e T. harzianum AMS 29.14 apresentaram atividade enzimática superior ao padrão, T. reesei RUT C-30 e foram submetidas a avaliação da atividade enzimática em diferentes condições de cultivos (bagaço de cana-deaçúcar tratado e não tratado, em dois pHs: 3 e 5). Foi observado atividade superior das linhagens amazônicas para as três enzimas estudadas (endoglucanase, exoglucanase e β-glicosidase), quando comparadas à linhagem padrão utilizada. A atividade enzimática foi positivamente influenciada pelo pH ácido, assim como pelo substrato não tratado. A partir destes resultados é notório que as linhagens isoladas desse bioma possuem grande potencial de atividade celulolítica, e que estudos mais aprofundados podem proporcionar o futuro emprego desses fungos em diversas áreas industriais. / The Amazon Rain Forest, the largest Brazilian biome, is characterized by the wide diversity and heterogeneity of its ecosystems. Amazonian soils, in general, harbor high microbial diversity that plays important roles in the cycling of nutrients, through the decomposition of organic matter. Among the microorganisms, fungi stand out as biodegradation agents. These microorganisms produce cellulolytic enzymes that are of great economic and biotechnological importance. The present work proposed to access the fungal population of the genus Trichoderma, isolated from Amazonian Forest soils, in the search for lineages with high potential of cellulolytic activity. Twelve soil samples were collected, resulting in the isolation of 151 strains of Trichoderma spp. Gene sequencing of the alpha-1 transcription elongation factor region with the EF1 and TEFR primers evidenced the prevalence of seven Trichoderma species. Of the total isolates, Trichoderma spirale (37%), Trichoderma strigosum (22%), Trichoderma harzianum (18%) and Trichoderma asperellum (17%) were the most abundant. The strains were screened for qualitative cellulolytic activity in solid medium and quantitative in liquid medium. Two strains, T. harzianum AMS 23.14 and T. harzianum AMS 29.14 showed enzymatic activity superior to T. reesei RUT C-30, and were sent to the evaluation of the enzymatic activity in different conditions (sugarcane bagasse treated and untreated, in two pHs: 3 and 5). Superior activity of the Amazonian strains was observed for the three enzymes studied (endoglucanase, exoglucanase and β-glucosidase) when compared to the T. reesei RUT C-30 standard. The enzymatic activity was positively influenced by pH 3, as well as by the untreated substrate. From these results, it is well known that isolated strains of the Amazonian environment have a great potential for cellulolytic activity, and that further studies may provide the future employment of these strains in several areas of industry.

A investigação sobre morcegos cavernícolas brasileiros foi iniciada por TRAJANO (1981) que entre 1978 e 1980, estudou a comunidade que utiliza cavernas na área cárstica do Alto Ribeira, Sul do Estado de São Paulo. Seguiram-se estudos no norte de São Paulo, Distrito Federal e Bahia, sendo que trabalhos recentes estão sendo realizados em novas áreas, preenchendo uma lacuna importante no país. O presente estudo teve como objetivo realizar um novo levantamento da quiropterofauna do Alto Ribeira, complementando o levantamento prévio e verificando possíveis alterações devidas a perturbações antrópicas na área. Para tal, foram amostrados 13 pontos em áreas epígeas e 12 cavidades, das quais 10 foram estudadas mensalmente. O trabalho de campo consistiu de viagens mensais ao longo de um ano, com duração de cerca de 10 dias cada, com início em fevereiro de 2006 e término em janeiro de 2007. Todos os procedimentos seguiram, na medida do possível, os métodos adotados por Trajano (1981), sendo as redes colocadas nos mesmos locais amostrados há mais de duas décadas. No presente estudo, foram realizadas 121 noites de amostragem, com um esforço total de 25.320 m2 de rede x hora. No total, foram capturados 1.493 morcegos pertencentes a 35 espécies, representando cinco famílias (Emballonuridae, Furipteridae, Natalidae, Phyllostomidae e Vespertilionidae). No conjunto das doze cavernas foram obtidas 29 espécies, algumas delas representando os primeiros registros em caverna no Brasil, como Lasiurus ega e Chiroderma doriae. Nas localidades epígeas, foram registradas 24 espécies com algumas exclusivas desse ambiente, como Artibeus glaucus, Eptesicus furinalis, Eptesicus taddeii, Histiotus velatus, Vampiressa pusilla e Phylloderma stenops. Dos 1.493 morcegos capturados, 1.091 foram marcados com anilhas no antebraço, dos quais 330 foram recapturados pelo menos uma vez, havendo recapturas múltiplas, totalizando 519 recapturas. Em uma das recapturas, um espécime de Artibeus lituratus chamou a atenção por representar o maior deslocamento já registrado no país com 113 km de distância em 443 dias. As espécies com maior número de captura foram L. aurita (N = 508), seguida de D. rotundus (N = 223) e Carollia perspicillata (N = 217) e aquelas com maior número de recapturadas foram Lonchorhina aurita (N = 189), Desmodus rotundus (N = 166) e Diphylla ecaudata (N = 98); para estas últimas foi estimado o tamanho das populações em uma área de 113 km2: L. aurita, 1.639 indivíduos, D. rotundus, 548 indivíduos e D. ecaudata, 206 indivíduos. Na comparação com o estudo de TRAJANO (1981), para o mesmo esforço de coleta, foram considerados, no presente estudo, 483 indivíduos de 21 espécies (Emballonuridae, Natalidae e Phyllostomidae), sendo Lonchorhina aurita (N = 155) a espécie mais freqüente, seguida de Desmodus rotundus (N = 89) e Diphylla ecaudata (N = 71). A partir desses dados, verificaram-se diferenças no número de capturas, abundância relativa das espécies e posições no ranking de abundância entre os dois estudos, porém não na riqueza da quiropterofauna cavernícola. Dessa forma, o turismo crescente na região pode estar provocando efeitos negativos sobre algumas espécies provavelmente mais sensíveis, como os insetívoros Furipterus horrens, Micronycteris megalotis e Myotis nigricans, porém ainda não vem causando alterações significativas na riqueza e abundância total dos morcegos cavernícolas no Alto Ribeira. / The survey on Brazilian cave bats was initiated by TRAJANO (1981) that between 1978 and 1980, studied the community that uses caves in a carstic area of Alto Ribeira, south of the State of São Paulo. Another studies had been followed in the north of São Paulo, Distrito Federal and Bahia, and recent works are being carried through in new areas, filling an important gap in the country. The present study it had as objective to carry through a new survey of quiropterofauna of the Alto Ribeira, being complemented the previous survey and verifying possible changes due the antropics disturbances in the area. For such, was sampled 13 points in epígeas areas and 12 caves, of which 10 had been studied monthly. The field work consisted of monthly trips throughout one year, with duration of about 10 days each, with beginning in February of 2006 and ending in January of 2007. All the procedures had followed, in the measure of the possible one, the methods adopted for TRAJANO (1981), being the nets placed in the same sampled places have two decades more than. In the set of the twelve caves 29 species had been gotten, some of them representing the first registers in cave in Brazil, as Lasiurus ega and Chiroderma doriae. In the epigeas localities, they had been registered 24 species with some exclusive of this environment, as Artibeus glaucus, Eptesicus furinalis, Eptesicus taddeii, Histiotus velatus, Vampiressa pusilla and Phylloderma stenops. Of the 1.493 captured bats, 1.091 had been banded with metal and plastic bands in forearm, of which 330 had been recaptured at least one time, having recapture multiple, totalizing 519 recapture. One recapture of a specimen of Artibeus lituratus called the attention for representing the biggest registered movement already in the country with 113 km of distance in 443 days. The species with larger number of capture had been L. aurita (N = 508), followed of D. rotundus (N = 223) and Carollia perspicillata (N = 217), and those with larger number of recaptured had been L. aurita (N = 189), Desmodus rotundus (N = 166) and Diphylla ecaudata (N = 98); for these last ones km2 was estimated the size of the populations in an area of 113: L. aurita, 1,639 individuals, D. rotundus, 548 individuals and D. ecaudata, 206 individuals. In the comparison with the study of TRAJANO (1981), for the same collection effort, they had been considered, in the present study, 483 individuals of 21 species (Emballonuridae, Natalidae and Phyllostomidae), being Lonchorhina aurita (N = 155) the species most frequent, followed of Desmodus rotundus (N = 89) and Diphylla ecaudata (N = 71). With these data, differences in the number of captures, relative abundance of the species and position in ranking of abundance between the two studies had been verified, however not in the richness of cave bats. Therefore, the increasing tourism in the region can be causing negative effect on some species probably more sensible, as the insectivorous Furipterus horrens, Micronycteris megalotis and Myotis nigricans, however still it does not come causing significant alterations in the richness and total abundance of the cave bats in the Alto Ribeira.

Os meliponíneos atuam como importantes polinizadores de espécies nativas nas regiões tropicais e subtropicais e apresentam uma grande relevância para as unidades de conservação. A disponibilidade de sítios de nidificação, conforme a oferta de diferentes substratos (cavidades em árvores e no solo, por exemplo), pode determinar a estrutura da comunidade de meliponíneos. Tendo como área de estudo o Parque Estadual das Fontes do Ipiranga (23º 39\' S, 46º 37\'W), situado em meio de uma intensa urbanização na cidade de São Paulo - SP, este trabalho teve como objetivo principal o levantamento de ninhos de espécies de meliponíneos em duas áreas com fitofisionomias distintas: áreas de estágio sucessional secundário inicial (SI), com menor densidade de indivíduos arbóreos, e áreas de estágio secundário tardio (ST), com maior densidade de indivíduos arbóreos. Foram formuladas as seguintes hipóteses: 1) a riqueza e a diversidade de espécies de meliponíneos serão maiores nas áreas ST; 2) nas áreas ST, a maior disponibilidade de substratos para nidificação (ocos de árvores) implicaria em uma densidade maior de ninhos de meliponíneos, com o predomínio de espécies que nidificam em árvores; 3) nas áreas SI, os valores de riqueza e de abundância relativa de espécies de meliponíneos que nidificam no solo serão maiores que os valores para as espécies que nidificam em árvores, pela baixa densidade de indivíduos arbóreos; 4) ninhos de espécies do gênero Melipona só serão encontrados nas áreas ST, por nidificarem em ocos de árvores com grandes CAPs (circunferência à altura do peito). No total, foram encontrados 14 ninhos, de 4 espécies, todas da subtribo Trigonina. A espécie Paratrigona subnuda, que nidifica no solo, foi a que apresentou a maior abundância relativa de ninhos (n = 11; 78,57 %), com ninhos tanto em áreas SI (n = 2), como em áreas ST (n = 9). As demais espécies estiveram representadas por apenas um ninho cada: Trigona braueri (n = 1; 7,14 %) em SI, Scaptotrigona bipunctata (n=1; 7,14 %) e Trigona spinipes (n = 1; 7,14 %), ambas em ST. As áreas ST apresentaram a maior abundância relativa de ninhos (n = 11, 78,57 %) e, ao contrário do que esperávamos, nessas áreas, a abundância de ninhos subterrâneos foi maior que a de ninhos de árvores, fossem eles de suporte ou de cavidades. Também não foram encontrados ninhos de espécies do gênero Melipona, como suposto. Os valores de diversidade foram praticamente os mesmos (baixos) para ambos os estágios (SI - H\' = 0,60; ST- H\' = 0,64). Já a riqueza e a densidade de ninhos foram significativamente maiores nas áreas ST (SI - riqueza = 2, densidade = 1,43 ninhos/ha; ST - riqueza = 3, densidade = 5,24 ninhos/ha). A densidade de ninhos para toda a área de estudo (3,33 ninhos/ha) foi maior que a média encontrada para outros levantamentos realizados em áreas naturais / Stingless bees act as important pollinators of native species in tropical and subtropical regions and have a great relevance to conservation units. The availability of nesting sites, according to substrates\' supply (cavities in trees and soil, for example), can determine the structure of stingless bees community. This study was conducted in the Parque Estadual das Fontes do Ipiranga (23º 39\' S, 46º 37\'W), situated in the middle of an intense urbanization in São Paulo city - SP. The study aimed to survey the nest of species of stingless bees in two areas with different vegetation types: areas of initial secondary successional stage (SI), with a lower density of individual trees, and areas of late secondary stage (ST), with a higher density of individual trees. The following hypotheses were formulated: 1) richness and diversity of stingless bees species will be higher in the ST areas; 2) in these areas as well, the increased availability of nesting sites (tree hollows) will entail in a higher density of stingless bees nests with a predominance of species that nest in trees; 3) in the SI areas, richness and relative abundance of stingless bees species that nest in the soil will be greater than the values for species that nest in trees, due to the low density of individual trees; 4) nests of species of the genus Melipona will only be found in the ST areas due to their preference to nest in hollows of trees with large CAPs (circumference at breast height). In total, 14 nests of 4 species were found, all of them belonging to the subtribe Trigonina. Paratrigona subnuda, which nests on the ground, presented the highest relative abundance of nests (n = 11, 78.57 %), with nests in both SI (n = 2) areas, as in ST areas (n = 9). The other species were represented by only one nest each: Trigona braueri (n = 1, 7.14 %) in SI, Scaptotrigona bipunctata (n = 1, 7.14 %) and Trigona spinipes (n = 1, 7.14 %), both in ST. The ST areas had the highest relative abundance of nests (n = 11, 78.57 %) and, contrary to what we had expected, in these areas, the number of underground nests was higher than of tree nests, whether they were supportive or cavities. Also contrary to our predictions, no nests of species of the genus Melipona were found. Diversity values were practically the same (low) for both stages (SI - H \' = 0.60; ST - H\' = 0.64). Richness and nest density were significantly higher in ST areas (SI - richness = 2, density = 1.43 nests/ha; ST - richness = 3, density = 5.24 nests/ha). The nest density for the entire study area (3.33 nests/ha) was higher than the average found in other surveys in natural areas

Tropical rainforests have an unparalleled capacity to sequester carbon, harbor biodiversity, and cycle water and nutrients due to their high rates of primary production. The large biomass stocks and rapid regeneration rates of these forests are often attributed to ample soil nitrogen and quick recovery of the nitrogen cycle in tropical soils following disturbance. Symbiotic nitrogen-fixing trees, which are relatively abundant at tropical latitudes, have the greatest capacity to provide tropical rainforests with new nitrogen, yet the ecological drivers of tropical symbiotic nitrogen fixers and their effects on the forests they inhabit are not well understood. This dissertation consists of four chapters that examine the patterns, environmental controls, and ecological consequences of symbiotic nitrogen-fixing trees in regenerating and intact rainforests in the Caribbean lowlands of Costa Rica. In chapter 1, I use field sampling in a chronosequence of rainforest plots to show that symbiotic nitrogen fixation declines through succession despite increases in the basal area of nitrogen-fixing trees. Chapters 2 and 3 describe results from a controlled shadehouse experiment assessing the effects of light, soil nitrogen, and plant competition on nitrogen fixation rates and the growth and biomass allocation of nitrogen fixers and non-fixers. In chapter 2, I demonstrate that light regulates nitrogen fixation more strongly than soil nitrogen availability. This is a departure from the historical focus on soil nitrogen as the primary regulator of nitrogen fixation and has the potential to resolve longstanding paradoxes of tropical nitrogen cycling. In chapter 3, I show that nitrogen fixation provides some resistance to competitive effects from neighboring plants in nitrogen-limited conditions, and that nitrogen fixers in these conditions downregulate their fixation rates in the presence of a competitor. This chapter also demonstrates that nitrogen fixation does not represent a significant structural cost to the plant, as reduced root biomass of nitrogen fixers more than compensates for allocation to nodule production. Finally, in Chapter 4, I demonstrate that nitrogen-fixing trees in our chronosequence plots do not promote forest growth, as expected given their capacity to fertilize their neighbors, but rather inhibit forest growth because they are strong competitors. These chapters describe several unexpected findings – i.e. that light primarily drives nitrogen fixation and that nitrogen fixers slow forest growth – which provide new and important insight into the role that nitrogen-fixing trees play in the growth of Costa Rican rainforests.

O presente trabalho propõe-se a investigar alguns aspectos referentes a estrutura e função de 71 jardins-quintais como subunidades dos sistemas agrícolas das comunidades quilombolas do Vale do Ribeira, município de Eldorado Paulista, São Paulo. Dessa forma, pretende-se compreender e problematizar a importância desses espaços no sistema produtivo agrícola mais abrangente desses caipiras negros, bem como as transformações pelas quais essas mesmas subunidades agrícolas vêm passando ao longo das últimas décadas. A agricultura itinerante uma das principais fontes de subsistência para populações humanas que habitam as florestas tropicais ao redor mundo. De maneira geral, os sistemas agrícolas baseiam-se criticamente na mão de obra familiar, sendo altamente influenciados pela organização social e dinâmica da unidade doméstica (Ali 2005, Pedroso-Júnior 2008, Pedroso-Júnior et al 2008). O estudo desses sistemas tem crescido em importância e visibilidade, com enfoque voltado principalmente para a dinâmica de roças e florestas. No entanto, a unidade jardim-quintal, até então considerada secundária na produção e reprodução doméstica, constitui um importante elo no entendimento das práticas agroflorestais locais. Para execução deste trabalho lançou-se mão de duas bases analíticas: uma qualitativa e etnográfica e a outra quantitativa e sistemática. As unidades de análise deste estudo foram o indivíduo e a unidade doméstica (UD). As mulheres foram as informantes-chave já que são reconhecidamente as principais mantenedoras de jardins e quintais. Assim, cada UD pesquisada teve uma informante. Os métodos utilizados para caracterizar e quantificar a composição e diversidade dos jardins e quintais foram questionários abertos e listagens livres. Para a descrição de alguns elementos estruturais e funcionais dos jardins-quintal foi utilizada a estatística descritiva. As comparações entre as comunidades estudadas foram realizadas através de testes de hipótese. A conjugação de dados socioeconômicos com os conjuntos de dados referentes aos jardins-quintal foi analisada utilizando-se a estatística multivariada. Os resultados mostraram que os jardins-quintal das comunidades quilombolas aqui referenciadas são sistemas agrícolas altamente complexos, tanto em seu aspecto estrutural quanto funcional, estando submetidos a transformações significativas principalmente ao longo das 6 últimas décadas. As diferenças socioeconômicas existentes entre as unidades domésticas não têm relação direta com a diversidade de etnovariedades dos jardins-quintal. / This study aims to describe several aspects related to the structure and function of 71 homegardens which are here interpreted as subunities of the complex agricultural system present in the quilombola communities of the Ribeira Valley, municipality of Eldorado, SP. This description allows for the comprehension of the importance of these swidden plots in the productive systems of the caipiras negros, as well as for a better understanding of the several socioeconomic transformations that these homegardens have been going through during the last few decades. Agricultural systems are one of the most important subsistence activities for human populations that inhabit the tropical forests around the world. Generally, this productive systems are based on family labor, thus being strongly influenced by the social organization and the household dynamics (Ali, 2005; Pedroso-Júnior, 2008; Pedroso-Júnior, et al., 2008). Studies regarding these systems have grown in importance and visibility, mainly focused in the swidden lots and forests. However, the homegardens, until now considered a secondary activitie in the household production and reproduction, are gaining importance as an essential link for the understanding of the agroflorestal practices. This work is built on two analytical bases: a more qualitative and ethnographic one, and a more quantitative and systemic one. The units of analysis were the individual and the household (UD). Women were the key informants since they are recognized as the main keepers of the homegardens. Therefore, each studied UD had one informant. The methods used for the survey of homegarden plant diversity included open questionnaires and free listing. The description of homegardens structural and functional elements was done by means of descriptive statistics. Comparisons among the three studied quilombola communities were realized using hypothesis tests tools. The combination between de socioeconomic data and the data collected from homegardens was analyzed using cluster analysis. The results presented here show that the homegardens are a complex and diversified system, that have multiple functions (aesthetics, social, recreational and utilitarian) and several structural aspects. Also, they have been submitted to several and critical transformations at least during the last six decades. The socioeconomic differences among the households don´t have any relationship with the diversity of local homegarden crops.

This study was conducted at the Ailao Mountain National Natural Reserve (NNR) in natural vegetation described as: Lithocarpus xylocarpus/Castanopsis wattii (Oak /Chestnut association) forest. Study sites were located in the Xujiaba area of the reserve at an altitude of ~ 2450 m with slopes of 10-15 degrees. This type of forest is believed to be unique to the NEAR area. The forest is floristically characterized by multiple families and genera. It has two tall tree layers, a well-developed bamboo (Sinarundinaria nitida) layer and evergreen fern species. Bryophyte, ferns and lichen occur and abundant epiphytic bryophyte is present on tree boles.A number of important aspects of nutrient cycling, including patterns of biomass and nutrient accumulation; nutrient return in litterfall and release from decomposing leaf litter; annual nutrient uptake and retention, and nutrient input and output budgets through hydrological flux in natural Lithocarpus/Castanopsis forest in the reserve, were investigated.This natural forest is characterized by high biomass accumulation of living and dead materials. Trees account for >90 % of total biomass. Dead wood comprises a high proportion (9-41 %) of total stand biomass. The sequence of inorganic nutrient element content decreased in the order leave s>b ranche s>roots> stems. Elemental content of the total stand decreased in the order of C>Ca>N>K>AI>Mg>P>Fe>Mn. The elements C, Ca and N were mainly in stems while AI and Fe were mainly in roots.Litterfall was sampled using traps during the period 1991-1999. High variations in litter production between years were associated with masting years of canopy species, and exceptional physical events (strong winds and snow). The mean annual litterfall is 7.12 t ha-1 with a bimodal seasonal pattern in litterfall: the main litterfall peak occurred in April-May and a lesser one in October-November. Woody ++ / litter and reproductive parts contribute relatively high proportions in this natural forest compared with other montane forests. Woody litter had low N and P concentrations compared with the leaf and reproductive parts. Elements return to the soil through small litterfall decreases in the order C>N>Ca>K>Mg>Mn>AI>P>Fe.The standard litter-bag technique was used to determine decomposition of leaf litter from three dominant canopy species (L. xylocarpus, L. chintungensis, C. wattii), one dominant understory species (the bamboo S. nitida) and a mixture of dominant bryophytes between Nov. 1997 and Oct. 1999. In each case, fast initial litter decomposition was followed by lower rates. Decomposition rates of canopy species and bamboo leaf litter appear to be controlled by initial concentration of lignin, N and P more than by morphological features of the leaves. P seemed to limit decomposition of all leaf litter, both initially and later. Nutrient release from decomposing leaf litter is in the order of K>Mg>Ca>N>P>~Fe, except for bamboo (S. nitida) K>Ca> P>N>Mg>Mn>Fe.Nutrient fluxes in bulk precipitation, throughfall and stemflow were measured in the natural forest between Jan. 1998 and Dec. 1999. This forest exhibited low interception by the canopy (13 % of total rainfall). N, P, Ca and S annual throughfall inputs were mainly from precipitation, while most of the K and two thirds of the Mg throughfall input was due to canopy leaching. There were significant effects of epiphytes on the amount and chemical composition of stemflow. Water volume and annual amounts of N, Ca and Mg were reduced, while K, P and S 1 were increased in stemflow after removing epiphytes on boles and branches.Plot- and catchment level approaches were applied to determine nutrient output from the ecosystem during the study period. The results indicated that this catchment has a subsurface flow system. ++ / The amounts of percolation water varied with soil depths. Concentrations of all nutrient elements studied were greater in surface water than in soil solution and stream water. The budgets for all nutrient elements between atmospheric inputs and outputs by both seepage and stream flow were positive, except for calcium (negative).This forest appears to be characterized by relatively high nutrient return (5.6-8.0 % of the total storage) and low nutrient retention (2.0-2.7 % of the total storage). The relative rate of nutrient cycling occupies an intermediate position between temperate evergreen broad-leaved forest and tropical montane rain forest, it is closer to montane rain forests in rates of nutrient circulation.