STRUCTURE AND DIVERSITY OF THE ARBOREAL COMPONENT IN CERRADO SENSU STRICTO IN NORTHERN MINAS GERAIS

Due to a rapid change in the land use in northern Minas Gerais State, southeastern Brazil, large amounts of cerrado have been converted into crops. There is little information about the structure and diversity of the remaining communities in the region. The present study aimed to characterize the structure of the tree vegetation in a cerrado sensu stricto area. We delimited thirty 20m x 20m plots and sampled tree individuals with diameter equal to or greater than 4.8 cm at 30 cm from the ground level (DGH30). We sampled a total of 2616 individuals of 76 species and 33 botanical families. The community showed a density of 2180 ind/ha and a basal area of 17.3 m2/ha. Qualea grandiflora, Terminalia fagifolia, and Dimorphandra mollis showed high importance values. Standing dead individuals stood out in the community. The Shannon diversity index (3.10) and Pielou’s evenness (0.70) indicate that the community is in an intermediate stage of succession in comparison with others. Despite the signs of disturbance, the community still includes species of great social and economic importance for the local population. This community’s floristic and structural patterns can be used to reference extractive management, restoration, and conservation initiatives of other cerrado areas in the region

Dinâmica climática e biogeográfica do Brasil no Último Máximo Glacial: o estado da arte

A partir de meados do século XX, cresceu significativamente o interesse em se compreender a dinâmica das vegetações em respostas às mudanças climáticas do Último Máximo Glacial - UMG (18 mil anos atrás). Nesse contexto, uma paisagem pode ser fruto de mudanças recentes ambientais ou relíquias de condições ainda mais remotas. Isso pode determinar, inclusive, o grau de complexidade e diversificação da paisagem. Diversos pesquisadores têm proposto modelos para explicar a cobertura da vegetação brasileira sob as condições do UMG desde a década de 1960, porém, o recente avanço dos modelos climáticos globais tem proporcionado novas perspectivas para uma reconstrução mais fiel das condições pretéritas. Nesse sentido, aqui discutimos sobre teorias biogeográficas formuladas e modificadas ao longo dos últimos 60 anos de estudos sobre a reconstrução das vegetações do Brasil para o UMG.From the mid-20th century onwards, there has been significant growing interest in understanding the dynamics of vegetation in response to the climatic changes of the Last Glacial Maximum (LGM, 18 thousand years ago). In this context, landscapes may be the result of recent environmental changes or relics from even more remote times, and this may even determine the degree of their complexity and diversification. Since the 1960s, several researchers have proposed models to explain the coverage of Brazil’s vegetation under the LGM, but the recent advance of global climate models has provided new perspectives for a more faithful reconstruction of the past conditions. We also discuss biogeographic theories formulated and modified over the last 60 years of studies on the reconstruction of Brazilian vegetation of the LGM

Relação espécie-área em campos de murundus com diferentes históricos de perturbação

Atividades antrópicas promovem alterações em diversas características abióticas do meio, ocasionando mudanças em um dos mais consistentes padrões da ecologia, a relação espécie-área. Objetivamos avaliar as relações entre riqueza/abundância de plantas e área dos montes em campos de murundus (campos sazonalmente alagados com montes espaçados) circundados por matriz antrópica. Ademais, avaliamos como atividades antrópicas afetam essas relações e as síndromes de dispersão das comunidades. Amostramos dois campos de murundus, ambos circundados por monoculturas, um impactado (CMI) e outro protegido (CMII). Encontramos redução no número de espécies com o aumento da área do murundu no CMI e relação oposta no CMII. A abundância de indivíduos foi positivamente relacionada à área do murundu nos dois campos. Já em relação à síndrome de dispersão, a maior diversidade de síndromes foi encontrada no CMI. A área é um fator determinante dos padrões de riqueza e abundância de plantas nos murundus, mesmo em ecossistemas circundados por matriz antrópica. Como os campos avaliados estão expostos às mesmas condições climáticas e apresentam estrutura semelhante, a relação espécie-área negativa encontrada no CMI indica que a pressão antrópica nesse campo já foi efetiva em eliminar espécies e romper com um padrão esperado para as comunidades naturais

Aspectos estruturais e similaridade florística entre fragmentos de floresta tropical seca com diferentes históricos de manejo no norte de minas gerais, Brasil

In order to produce useful knowledge to the initiatives of protection and management of forest fragments, more specifically for tropical dry forests which suffer with frequent anthropic activities, and due to the lack of specific studies, this article aimed describe the structure and the floristic similarity among three areas of dry forest with different management histories. The study was developed in Capitão Enéas municipality, Northern Minas Gerais, Brazil, where three fragments were evaluated, being one in regeneration for 30 years, another submitted to occasional fire and the third with selective cut in small scale. The sampling was developed through the point quarter method considering all the alive phanerophyte individuals with circumference at breast height (CBH) ≥ 15 cm. In the three fragments, 512 individuals, distributed in 60 species, 47 genera, and 23 families were sampled. The most representative families were Fabaceae (26), Anacardiaceae (4), Bignoniaceae (3) and Combretaceae (3). However, fourteen families were represented by only one species. Only eight species were common to all fragments - Myracrodruon urundeuva standed out with 26.9% of all sampled individuals - while a great number of species were exclusive of each fragment. The floristic and structural differences between the fragments are possibly related to the history and intensity of management in each area besides the topography variations and the presence or absence of limestone outcrops. These results show the importanceof each fragment, indicating that the loss of anyone would cause negative impacts on the regional flora and consequently to the associated biodiversity

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Edaphic gradients and their relationship with the vegetation types of semi-arid southern Brazil

O semi-árido no Brasil representa uma importante extensão territorial, onde o clima é marcadamente sazonal, com baixas precipitações, elevadas taxas de evapotranspiração e maiores temperaturas. Sua porção sul compreende o limite norte entre os Estados de Minas Gerais e Bahia. Essa região é dominada pela fitofisionomia de floresta decidual, no entanto, diversas fisionomias de cerrado também estão presentes. As diferentes porções da paisagem e sua variação edáfica são responsáveis pelo estabelecimento de diferentes fisionomias. No entanto, estudos que abordam tais relações e que buscam a compreensão dos gradientes pedovegetacionais são escassos nas paisagens do semi-árido brasileiro. Dessa forma, objetivou-se caracterizar os solos e as comunidades vegetais de diferentes segmentos da paisagem (topo, encosta e baixada) e testar as seguintes hipóteses: (1) solos de um mesmo segmento da paisagem, submetidos a mesma condição climática e fitofisionômica, se assemelham mesmo em localidades distintas; (2) as comunidades vegetais sobre um mesmo segmento se assemelham floristicamente e (3) as espécies mais abundantes apresentam preferência a determinados segmentos da paisagem. Para isso, foram amostrados os solos e as comunidades vegetais em 14 ambientes sobre diferentes segmentos em Januária (MG), Porteirinha (MG), Guanambi (BA) e Ibiassucê (BA). As variáveis dos solos analisados foram submetidas à análise de componentes principais, com o objetivo de verificar a existência de gradiente (Capítulo 1). As espécies amostradas nos diferentes segmentos foram submetidas à análise de similaridade; e as mais abundantes foram correlacionadas com as variáveis de solos por meio de análise de correspondência canônica para observar suas tendências ao longo do gradiente (Capítulo 2). Um gradiente de fertilidade dos solos pôde ser observado, no qual os mesmos segmentos se agrupam em função de suas características edáficas, confirmando a hipótese da similaridade edáfica. Em um extremo do gradiente, os topos apresentaram-se mais distróficos, com elevados teores de alumínio e baixa saturação por bases. Nessa porção, concentraram-se as fisionomias de cerrado. O outro extremo do gradiente apresentou-se eutrófico, com os maiores valores de saturação por bases. Nessa porção, concentraram-se as fisionomias de floresta decídua associadas às diferentes encostas. O centro do gradiente apresentou valores medianos das variáveis edáficas, sendo considerado a porção mesotrófica. Nessa porção, concentraram-se os segmentos de baixada associados à floresta decídua. As encostas do interior do Espinhaço se diferenciaram pedologicamente das demais paisagens da bacia do médio São Francisco, devido às influências orográficas e quartzíticas. A análise de similaridade florística não agrupou as comunidades de segmentos semelhantes e sim as de maior proximidade geográfica, rejeitando a hipótese da similaridade florística. As comunidades da baixada e encosta leste de Ibiassucê, formação arbustiva-arbórea previamente caracterizadas como caatinga hipoxerófila, apresentaram semelhança florística com as demais florestas decíduas da bacia do médio São Francisco, e por isso consideradas um estado de sucessão das florestas decíduas. No entanto, a floresta decídua da encosta oeste mostrou grande dissimilaridade das demais comunidades. As espécies de maior abundância de cada comunidade mostraram preferência de segmentos no gradiente após associadas às variáveis edáficas, confirmando a hipótese da preferência das espécies. Em geral, as comunidades das encostas mostraram-se mais densas, com menor área basal e maior dominância de uma espécie, com destaque para Myracrodruon urundeuva e Handroanthus ochraceus. Tais características das encostas foram associadas aos constantes distúrbios, predominantemente naturais, aos quais estes ambientes estão submetidos.The semi-arid region in Brazil represents a significant territorial extension, where the climate is markedly seasonal, with low rainfall, high evapotranspiration and higher temperatures. Its southern portion comprises the northern boundary between the states of Minas Gerais and Bahia. This region is dominated by dry forest vegetation type, however, different cerrado ́s vegetation type are also present. The different portions of the landscape and its edaphic variation are responsible for the establishment of different vegetation type. However, studies approach these relationships and seeking to understand the edaphic-vegetational gradients are scarce in the landscapes semi-arid. Thus, the objective was to characterize the soils and plant communities of different landscape segments (top, slope and low) and test the following hypotheses: (1) soils of the same segment of the landscape, subject to the same climatic conditions and vegetation types, are similar even in different locations, (2) the plant communities on the same segment are similar floristically and (3) the most abundant species show preference to certain segments of the landscape. For this, we sampled soils and plant communities in 14 different environments on segments Januária (MG), Porteinha (MG), Guanambi (BA) and Ibiassucê (BA). The variables of the analyzed soils were subjected to Principal Components Analysis, in order to verify the existence of gradient (Chapter 1). The species sampled in different segments were subjected to similarity analysis, and the most abundant were correlated with the variables of soils through of canonical correspondence analysis to observe trends along the gradient (Chapter 2). A gradient of soil fertility could be observed, in which the same segments grouped according to their soil characteristics, confirming the hypothesis of edaphic similarity. At one extreme of the gradient, the tops were more dystrophic with high aluminum levels and low base saturation. In this portion, was concentrated cerrado ́s vegetation type. The other end of the gradient presented eutrophic, with higher values of saturation. In this portion, was concentrated vegetation types of dry forest associated with different slopes. The center of the gradient showed median values of soil characteristics, the portion being considered mesotrophic. In this portion, concentrated segments of the lowland associated with dry forest. The slopes of the interior of Espinhaço differed edaphically from the other landscapes of the middle São Francisco basin, due to orographic influences and quartzite. The floristic similarity analysis did not group the communities of similar segments, but the greater geographical proximity, rejecting the hypothesis of floristic similarity. The communities of the low and eastern slope of Ibiassucê, formation shrubs-trees previously characterized as savanna hypoxerophytic showed floristic similarities with other dry forests of the San Francisco river basin, and therefore considered a state of succession of dry forests. However, the dry forest of the western slope showed great dissimilarity of the other communities. The most abundant species of each community showed preference segments of the gradient after associated with soil characteristics, confirming the hypothesis of the preference of the species. In general, the communities of the slopes were denser, with lower basal area and greater dominance of one species, especially Myracrodruon urundeuva and Handroanthus ochraceus. These characteristics of the slopes were associated with constant disturbances, naturally predominant, which these environments are submitted.Fundação de Amparo a Pesquisa do Estado de Minas Gerai

Dinâmica da vegetação do Ultimo Máximo Glacial (21 ka) e Holoceno médio (6 ka): um modelo ecológico de nicho de biomas baseado em clima e solo

Diversas técnicas de modelagem tem sido utilizadas para predizer o paleoespaço ocupado por biomas ou espécies. Porém, a liberdade de escolha das variáveis respostas e disponibilidade de preditores diferentes dos climáticos têm sido a maior restrição dos modelos, gerando distribuições com baixa acurácia ou incoerente com a cobertura real. Objetivou-se caracterizar o nicho fundamental dos biomas mais representativos do Brasil e predizer suas coberturas para o momento atual e para dois episódios passados, o Ultimo Máximo Glacial e o Holoceno Médio. Para tanto, foi utilizada a modelagem de nicho ecológico, com preditores climáticos e pedológicos. Como unidades amostrais, foram utilizadas 500 células de 100 km2 para 10 biomas, derivados do mapa de vegetação oficial do Brasil. Foi utilizado um total de 10 preditores em um modelo gerado pelo classificador RandomForest. Para a predição do clima pretérito, foram utilizados preditores climáticos de três modelos de circulação geral (CCSM4, MPI- ESM-P e MIROC-ESM). A calibração foi executada com 200 amostras de treinamento de cada bioma. Foram utilizados sítios de fosseis polínicos com uma comparação direta para a validação das reconstruções. Para a condição atual, um Kappa de 0,82 foi possível, gerando um predição altamente coerente com a cobertura real do país. Mostramos aqui que a diversidade de biomas existentes, marcadamente diferentes, não deve ser subestimada, e que, embora apresentem complexa relação, são passiveis de serem modelados com grande acurácia utilizando preditores climáticos e pedológicos. O clima pretérito foi mais frio e úmido em quase todo território, porém, a bacia Amazônica foi a região mais afetada pelas alterações climáticas dos últimos 21 ka. Isso fez com que a dinâmica de vegetações fosse mais intensa nesse local. Na região sul, a floresta subtropical se desloca para menores latitudes, enquanto os campos sulinos expandiam sua cobertura. Para a maioria dos biomas, as maiores alterações foram restritas às porções ecotonais, corroborados pelos fosseis polínicos. Os preditores utilizados mostram-se eficientes e complementares, pois abrangem partes distintas do nicho multidimensional, possibilitando reconstruções da cobertura vegetal mais plausíveis com a realidade abiótica.Several modeling techniques have been used to predict the paleospace occupied by biomes or species. However, the freedom of choice of response variables and availability of different climatic predictors have been the major limitation of the models, generating distributions with low accuracy or inconsistent with the actual coverage. This study aimed to characterize the fundamental niche of the most representative biomes of Brazil and predict their coverage for the current moment and for the two past episodes, the Last Glacial Maximum and the middle Holocene. Therefore, the ecological niche modeling was used, with climatic and pedologic predictors. For sampling units were used 500 cells 100 km2 for 10 biomes, derived from official vegetation map of Brazil. It used a total of 10 predictors in a model generated by RandomForest classifier. For the prediction of the past climate, climate predictors three general circulation models were used (CCSM4, MPI-ESM-P and MIROC-ESM). The calibration was performed with 200 training samples of each biome. Fossil pollen sites were used with a direct comparison to validate the reconstructions. For the current condition a Kappa of 0.82 was possible, generating a highly consistent prediction with the actual coverage of the country. We show here that the diversity of biomes, markedly different, should not be underestimated, and that although present complex relationship, are likely to be modeled with great accuracy using climatic and pedologic predictors. The preterite climate was cooler and humid throughout most of the territory, however, the Amazon basin was the region most affected by climate change of the past 21 ka. This caused the dynamics of vegetation was more intense there. In the southern region, the subtropical forest shifts to lower latitudes, while the southern fields expanding their coverage. For most biomes, the biggest changes were restricted to ecotonal regions, supported by pollen fossils. Predictors used show to be efficient and complementary, because they cover different parts of the multidimensional niche, allowing reconstructions of more plausible vegetation with abiotic reality.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio