O objetivo deste trabalho foi analisar e comparar a composição florística e estrutura horizontal da floresta manejada (FM) e da floresta não manejada (FNM). Utilizou-se amostragem casual estratificada com 12 parcelas na FM e 12 na FNM. Em parcelas de 28 x 350 m mensuraram-se todos os indivíduos com circunferência a altura do peito (CAP) maior ou igual a 31,4 cm e menor do que 94,2 cm (nível I de inclusão), subparcelas de 28 x 100 m, os indivíduos com 94,2 cm ≤ CAP <157,1 cm (nível de inclusão II), subparcelas de 28 x 250 m e indivíduos com CAP ≥ 157,1 m (nível de inclusão III). Em ambas as florestas foram encontradas 216 espécies, distribuídas em 44 famílias botânicas. A FNM apresentou maior índice de diversidade de Shannon-Weaver (H')(H'= 4,47). A composição florística, na FM, não sofreu alterações significativas durante o manejo empresarial realizado. Entretanto, houve alterações significativas de riqueza e área basal entre FM e FNM devido à colheita realizada que implicou na retirada de indivíduos em classes comerciais e também ao dano causado às árvores remanescentes. As espécies de maior importância ecológica em FNM foram Rinorea guianensis Aubl (Violaceae), Pouteria bilocularis (H. Winkler) Baehni (Sapotaceae) e Sclerolobium paniculatum Vogel (Fabaceae). Em FM foram Rinorea guianensis Aubl (Violaceae), Manilkara huberi (Ducke) Chevalier (Sapotaceae) e Eschweilera coriacea (DC.) S.A. Mori (Lecythidaceae). Para o período considerado, a área basal parece estar se recuperando adequadamente.

ESTRUTURA E USO POTENCIAL DE ESPÉCIES ARBÓREAS EM FLORESTA MANEJADA, PA MOJU, SANTARÉM-PARÁRESUMO: Neste estudo, objetivou-se analisar a fitossociologia e o uso múltiplo das espécies arbóreas em floresta manejada na comunidade Actaaia, Assentamento Moju I e II, Santarém-Pará. Foram amostrados 10 ha de floresta manejada, alocando-se, sistematicamente, 20 parcelas de 20 m x 250 m e mensuradas todas as árvores com DAP ≥ 10 cm. Foram encontradas 128 espécies, pertencentes a 37 famílias botânicas. A diversidade pelo Índice de Shannon foi 4,04, que resultou em 83% da diversidade máxima da amostra. Cada espécie foi representada, em média, por oito indivíduos e a densidade e área basal foram 341,83 árv . ha -¹ e 18,05 m² . ha -¹, respectivamente. A floresta remanescente apresentou espécies com potencial madeireiro e não madeireiro, para a utilização pela comunidade; a ocorrência de 58% de espécies com, pelo menos, dois usos revelou a importância de estudar as suas funcionalidades para a melhoria da qualidade de vida dos comunitários, o que deve ser considerado em um plano de manejo florestal comunitário. STRUCTURE AND POTENTIAL USE OF TREE SPECIES IN A MANAGED FOREST IN PA MOJU, SANTÁREM-PARÁ ABSTRACT:The study aimed to analyze the phytosociology and multipurpose tree species use in a managed forest in the Actaaia community, Settlement Moju I and II, Santarém, Pará. 10 ha of managed forest were sampled, systematically allocating 20 plots of 20 m x 250 m, with all trees with DBH ≥ 10 cm measured. 128 species belonging to 37 families were found. The Shannon diversity index was 4.04, which resulted in 83% of the maximum diversity of the sample. Each species was represented on average by eight individuals and the density and basal area were 341.83 trees . ha -1 and 18.05 m² . ha -1 , respectively. After exploration, the forest contained species with timber and non-timber potential use by the community, with the occurrence of 58% of species with at least two uses, revealing the importance of studying their features to improve the quality of life of the community, which should be considered in a community forest management plan.

Mistletoes are considered keystone species on woodlands and savannas worldwide, providing a food resource for a diversified fauna, as well as a nutrient-enriched litter. Infections can be large (∼1–3 m) and, in some parts of the Amazonian savannas, parasitize up to 70% of hosts locally. Despite these facts, biomass of mistletoes is rarely investigated. Here we constructed allometric models to predict the biomass stock of the shrubby mistletoe Psittacanthus plagiophyllus in an Amazonian savanna. In addition, we determined whether host size could be used as a proxy for mistletoe biomass. Finally, we compared the biomass of mistletoes with that of trees, to evaluate their relative importance. We have shown that: (1) biomass of leaves (46.1% ± 13.5%) are as important as of stems (47.8% ± 13.5%), and relative contribution of stems increases as plant grows; (2) the model including width, breadth and vertical depth was the best (SE = 0.39, R2 = 0.9) for predicting individual mistletoe biomass; (3) mistletoe load and biomass per host had a positive, but weak (R2 = 0.11 and 0.09, respectively), relationship with host size, and thus such host information is a poor predictor of mistletoe biomass; and (4) in comparison with trees, mistletoes constituted less than 0.15% (0.5–22 kg ha−1) of the total above-ground biomass, suggesting that this life-form is irrelevant to the local biomass stock despite its unequivocal biological importance.

Phosphorus (P) reacts with soil minerals, which makes it less available to plants. Considering that Amazonian soils have a low pH and nutrient availability, both of these properties contribute to an increase in P limitation. Here, we investigate how the addition of P to the substrate affects morpho-physiological traits of Brazil nut trees (Bertholletia excelsa Bonpl.). The experiment was carried out in a greenhouse with 24-month-old saplings, and the P treatments consisted of a control (Ferrasol without P addition) and 100, 200, 400, and 500 mg P kg−1 of added to the soil. When B. excelsa saplings were fertilized with phosphate, the N:P leaf ratio reduced from 50 to 26. Addition of P favored the photochemical efficiency of PSII (FV/FM), and the application of 200 mg kg−1 increased photosynthesis (PN) by 50%. Furthermore, phosphorus enhanced light and nutrient use efficiency. An increase in B. excelsa dry biomass was observed when 200 mg P kg−1 was added, with maximum yield occurring at 306.2 mg P kg−1. Physiological parameters suggest robust responses by B. excelsa to P fertilization. In addition, our findings reveal the critical role of P on B. excelsa growth in Ferralsol, as well as the potential of P fertilization to improve functional traits of this important Amazonian tree.