Microbial successional pattern along a glacier retreat gradient from Byers Peninsula, Maritime Antarctica.

The retreat of glaciers in Antarctica has increased in the last decades due to global climate change, influencing vegetation expansion, and soil physico-chemical and biological attributes. However, little is known about soil microbiology diversity in these periglacial landscapes. This study characterized and compared bacterial and fungal diversity using metabarcoding of soil samples from the Byers Peninsula, Maritime Antarctica. We identified bacterial and fungal communities by amplification of bacterial 16 S rRNA region V3-V4 and fungal internal transcribed spacer 1 (ITS1). We also applied 14C dating on soil organic matter (SOM) from six profiles. Physico-chemical analyses and attributes associated with SOM were evaluated. A total of 14,048 bacterial ASVs were obtained, and almost all samples had 50% of their sequences assigned to Actinobacteriota and Proteobacteria. Regarding the fungal community, Mortierellomycota, Ascomycota and Basidiomycota were the main phyla from 1619 ASVs. We found that soil age was more relevant than the distance from the glacier, with the oldest soil profile (late Holocene soil profile) hosting the highest bacterial and fungal diversity. The microbial indices of the fungal community were correlated with nutrient availability, soil reactivity and SOM composition, whereas the bacterial community was not correlated with any soil attribute. The bacterial diversity, richness, and evenness varied according to presence of permafrost and moisture regime. The fungal community richness in the surface horizon was not related to altitude, permafrost, or moisture regime. The soil moisture regime was crucial for the structure, high diversity and richness of the microbial community, specially to the bacterial community. Further studies should examine the relationship between microbial communities and environmental factors to better predict changes in this terrestrial ecosystem.

Nutrient partition and nutritional efficiency of mango cv. Palmer as a function of plant age in São Francisco Valley, Brazil / Partição de nutrientes e eficiência nutricional da mangueira cv. Palmer em função da idade das plantas no Vale do São Francisco, Brazil

Knowing the accumulation of nutrients in mango plants is essential for calibrating fertilization programs aiming to increase yield in nutritionally unbalanced orchards. The work aimed to evaluate mango nutritional efficiency through nutrient accumulation and partitioning in plants of Palmer cultivar grown in sand soils at São Francisco Valley, Northwest Brazil. Commercial orchards located in Bahia and Pernambuco States, Brazil, under semi-arid climate (BShw; 400-800 mm annual rainfall) had the vegetable biomass and nutrient contents in the mango compartments determined in 1, 2, 4, 7, and 12 years old plants, by evaluating four plants of each age from 20 sample units. The separated samples of the harvested trees originated the compartments roots, stems, thick twigs, thin twigs, leaves and fruits. Nutrient contents and plant dry matter per compartment were determined and plant nutrient accumulation evaluated. Biomass and fruits coefficient of biological utilization were calculated. There was increment in the accumulated content of macronutrients in the mango plants over the years, with superiority for N and K, for which there was a sharp increase as compared to the other macronutrients. Manganese and Fe were the most accumulated micronutrients in the plants over the years. The canopy of the mango Palmer plants is the compartment that accumulates more macro and micronutrients, and the partition within the canopy occurs in the sequence: leaf> thin twig> thick twig. Phosphorus and Mg, and Cu and B are the nutrients more efficient to generate plant biomass and fruit production in the mango Palmer orchards.(AU)

Informações sobre o acúmulo de nutrientes em plantas de mangueira é requisito essencial para calibrar um programa de adubação visando aumento de produtividade em pomares com nutrição desbalanceada. Objetivou-se avaliar o acúmulo e partição de nutrientes e a eficiência nutricional em mangueira 'Palmer' com diferentes idades na região do Vale do São Francisco. As áreas de estudo estão localizadas nos municípios de Casa Nova, Bahia, e de Petrolina, Pernambuco, sob clima semiárido, com precipitação variando de 400 à 800 mm durante o ano. Foi quantificada a biomassa vegetal e calculados os conteúdos dos nutrientes nos compartimentos das plantas de mangueira com idades 1, 2, 4, 7 e 12 anos, sendo avaliadas quatro plantas por idade, totalizando 20 unidades amostrais. As árvores-amostra foram abatidas e separadas em raiz, caule, galho grosso, galho fino, folhas e frutos, para obtenção do conteúdo de nutrientes por compartimento. Em cada compartimento foi quantificada a massa de matéria seca e os teores de alguns nutrientes, calculando-se o conteúdo de cada nutriente e estimando-se o seu acúmulo. Houve incremento no conteúdo acumulado dos macronutrientes nas plantas de mangueira ao longo dos anos, com superioridade para o N e o K, que obtiveram aumento acentuado em relação aos demais macronutrientes. Manganês e Fe foram os micronutrientes mais acumulados nas plantas ao longo dos anos. A partição de macro e micronutrientes na mangueira 'Palmer' ocorreu, geralmente, nos compartimentos que compõem a copa das plantas, e nessa sequência: folha> galho fino > galho grosso. Fósforo, Mg, Cu, e B são os nutrientes com maior eficiência na produção de biomassa e frutos da manga Palmer.(AU)