NITRIFICAÇÃO E QUALIDADE DE SOLOS SOB PLANTAÇÕES DE EUCALIPTOS COM DIFERENTES IDADES

O estudo foi realizado utilizando amostras de solos coletadas em áreas de plantios comerciais de Eucalyptus grandis e de híbridos de E. grandis com E. urophylla, em seis diferentes idades, variando entre 3 e 84 meses; em um pomar de matrizes com 180 meses e em uma mata secundária de vegetação nativa pertencentes à empresa CENIBRA Celulose Nipo-Brasileira S.A., MG. Este trabalho teve como objetivo estudar o efeito do distúrbio causado pelo corte da floresta no processo de nitrificação e em outros processos bioquímicos e microbiológicos do solo. As atividades das enzimas-glicosidase e fosfomonoesterases, o teor de amônio e as taxas de amonificação e de nitrificação líquidas aumentaram com o avanço da idade da vegetação, sendo que os maiores valores foram detectados na área com vegetação nativa e numa área sob eucalipto aos 3 anos de idade, que recebeu cultivo mínimo. O teor de nitrato, ao contrário, apresentou relação inversa com a idade das árvores. A taxa de nitrificação potencial também foi mais elevada em áreas de plantios mais jovens, com idade até 3 anos. Trinta e cinco variáveis de natureza física, química, bioquímica e microbiológica foram utilizadas para análise de agrupamento das áreas estudadas. As áreas com povoamentos de eucalipto mais jovens posicionaram-se mais distantes da área com vegetação nativa, usada como referência, e da área com eucalipto aos 7 anos de idade. A retirada da floresta e posterior implantação de um povoamento de eucalipto causou distúrbio na comunidade microbiana do solo. O aumento da idade do povoamento de eucalipto e a adoção de um sistema de preparo do solo considerado mais conservador, qual seja, o cultivo mínimo, contribuíram para o restabelecimento das condições bioquímicas e microbiológicas encontradas na área com vegetação nativa.

Comprehensive In Silico Analysis and Transcriptional Profiles Highlight the Importance of Mitochondrial Dicarboxylate Carriers (DICs) on Hypoxia Response in Both Arabidopsis thaliana and Eucalyptus grandis

Plant dicarboxylate carriers (DICs) transport a wide range of dicarboxylates across the mitochondrial inner membrane. The Arabidopsis thalianaDIC family is composed of three genes (AtDIC1, 2 and 3), whereas two genes (EgDIC1 and EgDIC2) have been retrieved in Eucalyptus grandis. Here, by combining in silico and in planta analyses, we provide evidence that DICs are partially redundant, important in plant adaptation to environmental stresses and part of a low-oxygen response in both species. AtDIC1 and AtDIC2 are present in most plant species and have very similar gene structure, developmental expression patterns and absolute expression across natural Arabidopsis accessions. In contrast, AtDIC3 seems to be an early genome acquisition found in Brassicaceae and shows relatively low (or no) expression across these accessions. In silico analysis revealed that both AtDICs and EgDICs are highly responsive to stresses, especially to cold and submergence, while their promoters are enriched for stress-responsive transcription factors binding sites. The expression of AtDIC1 and AtDIC2 is highly correlated across natural accessions and in response to stresses, while no correlation was found for AtDIC3. Gene ontology enrichment analysis suggests a role for AtDIC1 and AtDIC2 in response to hypoxia, and for AtDIC3 in phosphate starvation. Accordingly, the investigated genes are induced by submergence stress in A. thaliana and E. grandis while AtDIC2 overexpression improved seedling survival to submergence. Interestingly, the induction of AtDIC1 and AtDIC2 is abrogated in the erfVII mutant that is devoid of plant oxygen sensing, suggesting that these genes are part of a conserved hypoxia response in Arabidopsis.

The ectomycorrhizal fungus Pisolithus microcarpus encodes a microRNA involved in cross-kingdom gene silencing during symbiosis

Small RNAs (sRNAs) are known to regulate pathogenic plant–microbe interactions. Emerging evidence from the study of these model systems suggests that microRNAs (miRNAs) can be translocated between microbes and plants to facilitate symbiosis. The roles of sRNAs in mutualistic mycorrhizal fungal interactions, however, are largely unknown. In this study, we characterized miRNAs encoded by the ectomycorrhizal fungus Pisolithus microcarpus and investigated their expression during mutualistic interaction with Eucalyptus grandis. Using sRNA sequencing data and in situ miRNA detection, a novel fungal miRNA, Pmic_miR-8, was found to be transported into E. grandis roots after interaction with P. microcarpus. Further characterization experiments demonstrate that inhibition of Pmic_miR-8 negatively impacts the maintenance of mycorrhizal roots in E. grandis, while supplementation of Pmic_miR-8 led to deeper integration of the fungus into plant tissues. Target prediction and experimental testing suggest that Pmic_miR-8 may target the host NB-ARC domain containing transcripts, suggesting a potential role for this miRNA in subverting host signaling to stabilize the symbiotic interaction. Altogether, we provide evidence of previously undescribed cross-kingdom sRNA transfer from ectomycorrhizal fungi to plant roots, shedding light onto the involvement of miRNAs during the developmental process of mutualistic symbioses.

HYPSOMETRY AND VOLUMETRY OF Eucalyptus urograndis IN A CROP-FOREST INTEGRATION SYSTEM

Due to the positive impact that the eucalyptus species has on the Brazilian economy, it is currently the most used forest essence. The objective of this work was to evaluate different hypsometric and volumetric models for Eucalyptus urograndis clones (Eucalyptus urophylla S.T. Blak and Eucalyptus grandis W. Hill ex Maiden) in a Crop-Forest Integration (CFI) system. The trees were evaluated at 7 years of age and arranged in double rows, occupying 20.76% of the total system area. The individuals were subjected to rigorous volumetric cubing according to the Smalian method at intervals of one meter up to full height. The following models were evaluated for the collected height data: Linear, Trorey, Stofels, Curtis, Henriksen, Prodan, Chapman & Richards, Petterson and Bailey & Clutter. Furthermore, the Spurr, Hohenald-Krenn, Stoate, Schumacher Hall, Meyer, Husch, Ogaya and Takata models were used for volume data. The results were determined through the coefficient of determination (R2), standard error of the estimate in percentage (Syx%), significance of the regression coefficients (𝛽) and graphical distribution. The hypsometric model which best fit the database among tested models was the Prodan equation, with a coefficient of determination (R²) of 0.89, while the best result for volumetric models was found using the Meyer model, with a coefficient of determination (R²) of 0.99. All evaluated models were efficient in estimating the height and volume of the Crop-Forest Integration (CFI) system, thus demonstrating that GG100 eucalyptus is a good option in integrated systems.

HAND-ARM VIBRATION IN DIFFERENT OPERATING CONDITIONS WITH A CHAINSAW

The mechanization of forest harvesting is a trend in Brazil. However, small and medium-sized companies in the forestry sector, even today, opt for semi-mechanized harvesting, using chainsaws for the harvesting and sectioning of trees. Despite technological advances, when operated continuously, chainsaws may cause damage to the operator’s body, acting as a stressor, and vibration excess is responsible for numerous health disorders, among them the Raynaud syndrome. In this sense, this study aimed to determine the vibration levels to which a chainsaw operator is subjected, during the transversal cut (tracing) of the wood, in different forest species and cutting sets. The treatments consisted of three forest species (Eucalyptus grandis, Eucalyptus dunnii and Acacia mearnsii De Wild) and two cutting sets, consisting of square tooth chains of the semi-chisel and chisel types. The vibration assessment was based on the criteria established by the Regulatory Standards NR15, NHO10 and ISO 2631-4. The results of vibration levels were higher than the reference limits established by ISO 2631-4, and, for both cutting sets, the highest vibration levels occurred on the “x” axis. After the data processing, the acceleration values resulting from the normalized exposure to hand-arm vibrations showed significant differences for the “y” and “z” axes. Therefore, it can be inferred that the chainsaw operation is a stressor, potentially capable of causing damage to workers' health.

Instrumento digital para medição de diâmetro florestal usando microcontrolador de baixo custo

Este estudo descreve o processo de criação e montagem de um sistema para aquisição de dados de diâmetro à altura do peito de forma automatizada. A construção do protótipo móvel contou com os seguintes componentes: Arduino Pro mine, Módulo Cartão Micro SD, Sensor de Distância, Display LCD e Módulo Joystick. A montagem do sistema foi realizada em recipiente de plástico transparente. A validação dos dados foi feita por meio da comparação dos valores de diâmetro à altura do peito coletados com a suta convencional e o protótipo construído, por meio de medidas frontais e laterais de um plantio de Eucalyptus grandis. Os resultados demonstraram correlação linear positiva entre os dados obtidos pelo método convencional, utilizando suta mecânica e os dados obtidos atrás do protótipo confeccionado. O coeficiente de correlação de Pearson foi de 0,92 e 0,91 para as medidas frontal e lateral, respectivamente. O projeto se mostra viável para o uso dentro do setor florestal, principalmente em razão do baixo custo para confecção. No entanto, o protótipo apresentado necessita de maiores ajustes, principalmente em sua estrutura, a fim de facilitar o manuseio.