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We evaluated the nutrient input via incident rainfall in a Eucalyptus dunnii stand in the Brazilian Pampa biome. During the two-year study, we analyzed nutrient concentrations in incident rainfall (P), throughfall via drip (Pi), and stemflow (Et

ResumoA liberação de nutrientes via decomposição da serapilheira foliar representa parte significativa da ciclagem biogeoquímica. Avaliou-se a decomposição e a liberação de nutrientes da serapilheira foliar de Eucalyptus dunnii estabelecido no Bioma Pampa. Após o fechamento das copas das árvores (18 meses de idade) instalaram-se sobre o solo 648 litterbags distribuídos em três parcelas, realizando-se coletas mensais (18 amostras) durante um período de 36 meses. Para cada amostra foi pesada a massa remanescente e determinada a concentração de nutrientes. A massa foliar remanescente após três anos foi de 27,4%. O coeficiente de decomposição (k) foi de 0,37, com um tempo de meia vida (t 1/2 ) de 1,55 anos. A serapilheira foliar, após dois anos em decomposição, liberou mais de 50% da quantidade inicial de cada nutriente avaliado, com exceção ao Fe, Cu e Zn. O potássio foi o nutriente com maior percentual de liberação nos meses iniciais de decomposição da serapilheira foliar, com 60% no primeiro mês e mais de 80% aos três meses. Para os demais nutrientes a liberação foi lenta e gradual, como observado, principalmente, para N e P, com 19 e 39% ao final de 12 meses e com 60 e 67% ao final dos 36 meses de decomposição da serapilheira foliar, respectivamente. Palavras-chave: nutrição florestal; litterbag; ciclagem de nutrientes. AbstractThe release of nutrients by leaf litter decomposition is a significant part of biogeochemical cycling. The decomposition and nutrient release from leaf litter of Eucalyptus dunnii located in the Pampa Biome was evaluated. After closing of the canopy (18 months old), 648 litterbags were distributed in three plots on the soil; and, 18 samples per month during 36 months were collected. For each sample, the remaining mass was weighed and the concentration of nutrients determined. The remaining leaf mass after three years was 27.4%. The decomposition coefficient (k) was 0.37 with a half-life time (t 1/2 ) of 1.55 years. The leaf litter after two years decomposition released more than 50% of the initial amount of each nutrient evaluated, except for the Fe, Cu and Zn. Potassium was the nutrient with the highest percentage of release during the initial months of decomposition of leaf litter, with 60% in the first month and more than 80% at three months. For other nutrients release was slow and gradual, as seen mainly for N and P, with 19 and 39% after 12 months and 60 and 67% at the end of 36 months of decomposition of leaf litter, respectively.

Atmospheric deposition is responsible for the ions input, which may be due to dust and aerosols and rainfall. During rainfall a portion is intercepted by the tree canopy and returned to the atmosphere by evapotranspiration, another part crosses the forest canopy called throughfall and stemflow. The objective of the study was to quantify incident rainfall partitioning into throughfall, stemflow and canopy interception in a Eucalyptus dunnii stand in southern Brazil. Four plots of 20 m × 21 m were demarcated. The rainfall consists 3 rain collectors in an open area. The throughfall consisted 3 collectors per plot in the line, interlining and diagonal positions of the trees. The stemflow consisted in the installation of three systems per plot formed by a hose in the trunk of the tree that leads the solution to a reservoir. The adjustment of the throughfall, stemflow and canopy interception in function of the incident precipitation was of 99%, 90% and 52%. As the volume of rainfall increases, the coefficient of variation decreases. The annual rainfall was 1903 mm, with a canopy interception average of 8.9%.

Resumo: Estudos relacionados à produção de biomassa e acúmulo de nutrientes são a base para a compreensão da dinâmica nutricional em povoamentos florestais. O objetivo do presente trabalho foi quantificar a biomassa e o estoque de nutrientes, em um povoamento de Eucalyptus dunnii, aos 60 meses de idade, estabelecido em Alegrete, Rio Grande do Sul. A amostragem da biomassa foi realizada a partir de doze árvores, que foram seccionadas ao nível do solo e a biomassa foi fracionada nos componentes: folhas, galhos, casca do tronco e madeira do tronco, com determinação de massa seca e tores de nutrientes. A biomassa total acima do solo foi de 58,76 Mg ha -1 , com sequência decrescente de alocação em madeira do tronco > casca do tronco > galhos > folhas. O estoque total de nutrientes foi de 175,5; 18,2; 171; 278,1; 69,1 e 21,5 kg ha -1 de N, P, K, Ca, Mg e S, respectivamente. Ressalta-se a importância da manutenção de resíduos da colheita sobre o solo, a fim de otimizar a ciclagem de nutrientes em função dos altos teores destes contidos nas folhas, casca e galhos.Palavras -chave: Nutrição florestal; Silvicultura; Ciclagem de nutrientes. Nutrients and biomass quantification in Eucalyptus dunnii Maiden stand established in Pampa biomeAbstract: Studies related to biomass production and accumulation of nutrients, are the basis for understanding the nutritional dynamics in forest stands. The objective of this study was to quantify the biomass and nutrient stocks, in a Eucalyptus dunnii stand, at 60 months old, established in Alegrete, Rio Grande do Sul. The sampling of biomass was taken from twelve trees which were cut at soil level and the fractional biomass components: leaf, branches, trunk bark and stem wood, with dry mass determination and nutrients concentration. The total above ground biomass was 58.76 Mg ha -1 , with decreasing sequence in the magnitude of the stem wood > trunk bark > branches > leaves. The total stock of nutrients was 175.5; 18.2; 171; 278.1; 69.1 and 21.5 kg ha -1 of N, P, K, Ca, Mg and S, respectively. We emphasize the importance of maintaining of harvest residues in the soil to optimize nutrient cycling due to high levels of these in the leaves, bark and branches.

The quantification of wood stock and other components of biomass is fundamental for forest planning. Given the difficulty of obtaining these data, the present study aims at the formulation of equations and the estimation of the different components of biomass, volume with and without bark, form factor and height of the trees at the end rotation. The study was carried out in the municipality of São Gabriel state of Rio Grande do Sul, Brazil with Eucalyptus saligna 10-year-old. The experimental design of the inventory and biomass quantification were completely randomized. In the inventory the DBH of all individuals of the 5 plots were measured. After determination of 4 classes of diameter were felled 12 trees and quantified leaves, branches, bark and wood. The selection of the models obtained coefficients of determination higher than 97%. The total biomass was 269 Mg ha-1, of which 89% was wood. The total volume was 546 and 494 m³ ha-1 with and without bark, representing an average annual increase of 54,6 and 49,4 m³ ha-1 year-1. The mean form factor was 0,48. The modeling presented excellent adjustments and certainly serves for future estimates of the stock biomass.

The aim of the present study was to quantify macronutrient stock in the hybrid Eucalyptus urograndis, for different soil types in Telemaco Borba, Parana, Brazil. Sandy texture (Cambisols Inceptisols), and clayey texture (Ferralsols Oxisols) soils were selected for the study. Based on the diameter at breast height (DBH) survey of all the trees comprising each plot, 12 trees were selected per soil type for biomass sampling. The trees were sectioned at soil level and separated into: leaves, branches, stembark, stemwood, tree tops wood, tree tops bark and roots, and a representative sample of each component was collected and grounded in a Wiley-type mill for analytical determination of the macronutrients. The analyses of the experiment were performed considering a completely randomized design. The concentrations of the macronutrients in the different biomass components were significantly different in both types of soil. With the exception of calcium, in the sandy soil and calcium and magnesium in the clayey soil, which were more present in the stembark component, the other components present the highest concentration values in the leaves component. The lowest concentration values of macronutrients, both for the sandy soil and for the clayey soil, were found in the stemwood and roots components. Total nutrient stock found in the biomass, in the sandy soil was 1.65 Mg ha-1, distributed in the following order of magnitude: stemwood > root > stembark > leaves > branches > tree tops wood > tree tops bark. For the clayey soil the order was: stemwood > stembark > root > branches > leaves > tree tops wood > tree tops bark, presenting a total stock of 2.41 Mg ha-1. The highest amount of macronutrients in the biomass was found in soil with a clayey texture.

Resumo: O monitoramento da qualidade do solo, como das propriedades químicas, pode fornecer subsídios para o manejo silvicultural e conservação do solo, visando à manutenção da produtividade de sítios florestais. O presente trabalho teve como objetivo avaliar as mudanças nos atributos químicos do solo em um povoamento de Eucalyptus dunnii, aos dois e aos cinco anos de idade, no bioma Pampa do Rio Grande do Sul. Para tanto, foram coletadas amostras de solo em cinco profundidades (0-20, 20-40, 40-60, 60-80 e 80-100 cm), com posterior determinação de atributos físicos, além de pH, matéria orgânica, teores de alumínio, cálcio, magnésio, potássio e fósforo, bem como CTC potencial e efetiva, saturação por bases e por alumínio. Aplicou-se o teste t (α = 5 %) para detecção de diferenças significativas nas propriedades do solo, em função do tempo. A análise química do solo revelou que, em ambas ocasiões, houveram baixos teores de nutrientes, matéria orgânica, bem como pH ácido, além de alta saturação por alumínio. Após três anos de crescimento das árvores de Eucalyptus dunnii o pH reduziu em todas as profundidades do solo, o cálcio e potássio reduziram em 20-40 cm e 0-20 cm, respectivamente. Já o teor de alumínio aumentou em todas as profundidades, assim como o fósforo e a matéria orgânica de 40 até 100 cm do solo. Após três anos da primeira avaliação do solo, verificou-se alteração da fertilidade do mesmo, principalmente no pH, matéria orgânica e teores de potássio e fósforo.Palavras -chave: Nutrição florestal; Fertilidade do solo; Silvicultura. Characterization of soil fertility in a Eucalyptus dunnii Maiden stand in Pampa biome of RioGrande do Sul state Abstract: Monitoring ecological aspects, such as chemical soil quality, can provide subsidies for silvicultural management and soil conservation, to maintain the productivity of forest sites. This study aimed to evaluate changes in soil chemical properties in a Eucalyptus dunnii stand, in two and five-year-old, in the Pampa biome of Rio Grande do Sul state. Therefore, at two and the five-year-old stand soil samples were collected at five depths (0-20, 20-40, 40-60, 60-80 e 80-100 cm), with subsequent determination of physical attributes and pH, organic matter, content of aluminum, calcium, magnesium, potassium and phosphorus, as well as potential and effective CEC, base saturation and aluminum saturation. We applied the t-test (α = 5%) to detect significant differences in the properties of soil in function of time. The soil chemical analysis revealed that, on both occasions, there were low levels of nutrients, organic matter as well as acid pH, and high aluminum saturation. After three years of growth of Eucalyptus dunnii trees, the pH decreased in all soil depths, Ca and K decreased by 20-40 cm and 0-20 cm, respectively. The aluminum content increased at all depths, as well as phosphorus and organic matter from 40 to 100 cm of soil. After three years of the first evaluation of the soil, there was change of fertility, especially in pH, organic matter and phosphorus and...