Nutrientes foliares de espécies arbóreas de três estádios sucessionais de floresta ombrófila densa no sul do Brasil Leaf nutrient content of tree species from three successional stages of tropical rain forest in south Brazil

As concentrações de macro e micronutrientes foliares de espécies arbóreas foram avaliadas em três estádios sucessionais (inicial, intermediário e avançado) de uma floresta ombrófila densa das terras baixas, no litoral do Estado do Paraná, crescendo sobre solo arenoso e oligotrófico. Dentre as espécies arbóreas mais importantes de cada estádio sucessional (quatro iniciais; oito intermediárias; 11 avançadas), coletou-se folhas maduras de cinco diferentes indivíduos de cada estádio sucessional para a análise química dos seguintes elementos: N, P, K, Ca, Mg, C, Zn, Fe, Cu e Mn. As espécies do estádio inicial possuem as menores concentrações médias foliares de N, P, K, Zn, Fe e a maior concentração de Mg e estas concentrações são estatisticamente diferentes (p <0,05), quando comparadas com os valores médios dos demais estádios. Nos estádios intermediário e avançado, as concentrações médias de N, Ca e Mg, assim como os micronutrientes estão dentro dos valores esperados para florestas tropicais. As concentrações médias de K, nos estádios inicial e intermediário, e as concentrações médias de P, em todos os estádios, encontram-se abaixo dos valores reportados para as florestas tropicais. A relação C/N é alta (>25:1), apesar da tendência de diminuir à medida que avança a sucessão. O aumento da concentração da maioria dos nutrientes foliares analisados ao longo do gradiente sucessional está associado, possivelmente, com o incremento do acúmulo da serapilheira sobre o solo, o que proporciona ciclagem de nutrientes mais intensa e maiores concentrações de nutrientes no solo.<br>We investigated the leaf nutrient content of trees species from three distinct successional stages (early, intermediate, late) of a lowland rain forest located near the coast of Paraná State, Brazil. This forest grows on sandy soil with low nutrient content. We collected mature leaves from five different individuals of each sucessional stages of the most important tree species of each successional stage (four of the early; eight of the intermediate and 11 of the late stages) for chemical analysis of following elements: N, P, K, Ca, Mg, C, Zn, Fe, Cu e Mn. The species from early sucessional stage have lower contents of N, P, K, Zn, Fe, and higher contents of Mg. These concentrations are statistically different (p <0,05) when compared to mean values of the other stages. For the intermediate and late successional stages, the average nutrient concentrations of N, Ca, Mg and micronutrients are within the range of values expected for tropical forests. Foliar K concentration, from early and intermediate successional stages, and foliar P concentration, for all successional stages, are below the reported range of values for tropical forests. The C/N ratio is high (>25:1), despite of the tendency to decrease as succession advances. The increment of concentration of the most studied foliar nutrients along the successional gradient is probably related to the accumulation of litter above the soil that provides a more adequate environment for efficient nutrient cycling and higher nutrient concentration in the soil

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation; analyses timings and patterns of tumour evolution; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity; and evaluates a range of more-specialized features of cancer genomes