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.

-In a forest stand, litterfall is primarily responsible for the retention and return of nutrients to the soil. The objective of this study was to evaluate the return of nutrients through litterfall in a stand of Eucalyptus dunnii in a Pampa biome. For quantification of litterfall, four 420-m² installments were marked; within each one, four 0.50-m² collection plots were distributed. For the collection of thick branches, four 7.00-m² subplots were staked out. The collected litterfall was separated into leaf, twig, thick branch, and miscellany fractions for subsequent chemical analysis. The total litterfall measured was 6.99 Mg ha -1 yr -1 , and comprised 61.57% leaves, 17.34% twigs, 13.83% thick branches, and 7.26% miscellany. The total amount of macronutrients in the litterfall was 160.22 kg ha -1 yr -1 , and the macronutrient transfer order was the same for the leaf, twig, and thick branch fractions (Ca > N > K > Mg > S > P). The total quantity of micronutrients was 7.55 kg ha -1 yr -1 , and the transfer order was Mn > Fe > B > Zn > Cu. Maintaining litterfall on the site, especially in degraded or low fertility soils like in the Pampa biome, may contribute to possible improvements in soil characteristics.Keywords: Forest nutrition; Nutrient cycling; Pampa biome. DEVOLUÇÃO DE NUTRIENTES ATRAVÉS DA SERAPILHEIRA PRODUZIDA EM UM POVOAMENTO DE Eucalyptus dunnii Maiden EM SOLO ARENOSORESUMO -A produção de serapilheira é a principal responsável pela retenção e devolução de nutrientes para o solo em um povoamento florestal. O objetivo deste trabalho foi avaliar a devolução de nutrientes por meio da serapilheira produzida em um povoamento de Eucalyptus dunnii, no bioma Pampa. Para a quantificação da serapilheira produzida, foram demarcadas quatro parcelas de 420 m², e no interior de cada parcela foram distribuídos quatro coletores de 0,50 m². Para a coleta dos galhos grossos demarcou-se quatro sub-parcelas de 7,00 m 2 . O material coletado foi separado nas frações folhas, galhos grossos, galhos finos e miscelânea, com posterior análise química. A serapilheira produzida foi de 6,99 Mg ha -1 ano -1 , distribuída em 61,57%, 17,34%, 13,83% e 7,26%, nas folhas, galhos finos, galhos grossos e miscelânea, respectivamente. A quantidade de macronutrientes na serapilheira foi de 160,22 kg ha -1 ano -1 , sendo que, a ordem de transferência foi a mesma para as frações folhas, galhos finos e galhos grossos (Ca > N > K > Mg > S > P). Para os micronutrientes a quantidade foi 7,55 kg ha -1 ano -1 , seguindo a ordem decrescente de Mn > Fe > B > Zn > Cu. A manutenção da serapilheira no sítio, principalmente em solos degradados ou de baixa fertilidade natural, como é o caso da região do bioma Pampa, poderá contribuir com possíveis melhorias nas características do solo.Palavras-chave: Nutrição florestal; Ciclagem de nutrientes; Bioma Pampa.

The present work aims to quantify the precipitation partition after interaction with the Eucalyptus urophylla canopy under two fertilization treatments. The experimental design was completely causalized with two fertilization treatments. Each plot had a dimension of 30 m x 60 m, and the spacing of the seedlings was 3 m x 2 m. The study was developed in a arenizaded area located in the municipality of Maçambará, state of Rio Grande do Sul, Brazil. The duration of the study was one year (from April 2017 to March 2018). Biweekly over twelve months the volume of precipitation was quantified. The experiment consists of two fertilization treatments in a Eucalyptus urophylla stand: T1 with smaller and T2 greater fertilization. In each treatment 3 throughfall collectors were installed at one meter of the soil level and three stemflow collectors. In the open area 3 collectors of the incident precipitation were installed 1.5 meters from the ground level. The percentages of the throughfall, stemflow and canopy interception in relation to the incident precipitation were 95.3; 1.3 and 4.3% for treatment 1 and 91.7; 3.2 and 6.2% for treatment 2. The coefficients of determination for throughfall, stemflow and canopy interception were 0.99; 0.96 and 0.85 for treatment 1 and 0.99; 0.97 and 0.89 for treatment 2. The graphical analysis of the regression residues shows independence of the errors. The fertilization management described for treatment 2 results in a greater interception of rainfall due to the greater amount of biomass of the canopy.

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 present work was to quantify the nutrient input of the incident rainfall, throughfall, stemflow and canopy enrichment in an Eucalyptus dunnii plantation, established in soil with low natural fertility. Four plots of 20 m × 21 m were demarcated. The rainfall consists 3 rain collectors in an open área. 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. Through rainfall, 29.5 kg ha-1 of nutrients were supplied. When we consider the sum of the throughfall and stemflow, the amount of nutrients was 77.6 kg ha-1. After interaction with the tree canopy 48.2 kg ha-1 of nutrients were incorporated. Potassium showed the highest enrichment: 607%. The average nutrient enrichment was 163%. The input of N and K via incident rainfall was 1.8 and 3.1 kg ha-1. Considering the fertilization described in the methodology, this contributed amount represents 6.1 and 2.6% of the total. If we consider the rotation of 7 years for Eucalyptus dunnii, the contribution at the end of rotation represents 42.4 and 18% of N and K2O. The interaction with the canopy of Eucalyptus dunnii enriches the rainwater with nutrients making the solution with a more basic character.

The objective of this study was to estimate the biomass, nutrient stocks, and simulate the export of nutrients, in different genotypes of Eucalyptus. The experiment was conducted in São Gabriel, RS, Brazil, in 43-month-old stands. The selected trees were fractionated into leaves, branches, stembark and stemwood. An estimate of nutrient exports by biomass was calculated for three scenarios. The amount of total biomass ranged from 33.68 to 84.00 Mg ha -1 , with the highest production being E. uroglobulus, and E. dunnii the lowest. The tree canopy accumulated between 47% and 65% of the total macronutrients and 46% to 67% of the total micronutrients (E. benthamii (P2) and E. urograndis). The highest amount of nutrients exported with biomass harvesting, for the first and second scenario (harvesting the stemwood and harvesting the stemwood with stembark), occurred in E. uroglobulus (N, K, and S), E. urograndis (P, Mg, and Cu) and E. saligna (Fe, Zn, and B). For the third scenario (stem and canopy), the highest nutrient exportation occurred in E. urograndis, except for S, where the highest removal occurred in E. uroglobulus. The harvesting of only the stemwood resulted in the removal of the least nutrients from the system, independent of the genotypes.Produção de biomassa e conteúdo de nutrientes em diferentes genótipos de Eucalyptus no Pampa gaúcho RESUMO: O objetivo deste trabalho foi estimar a biomassa, o estoque de nutrientes e simular a exportação de nutrientes em diferentes genótipos de Eucalyptus. O experimento foi conduzido em São Gabriel, RS, em povoamentos com 43 meses de idade. As árvores selecionadas foram fracionadas em folhas, galhos, casca do fuste e madeira do fuste. A estimativa da exportação de nutrientes por biomassa foi calculada para três cenários. A quantidade de biomassa total variou de 33,68 a 84,00 Mg ha -1 , destacando-se o E. uroglobulus com a maior produção e o E. dunnii com a menor. A copa das árvores acumulou entre 47% e 65% do total de macronutrientes e 46% a 67% do total de micronutrientes (E. benthamii (P2) e E. urograndis). Para o primeiro e segundo cenário (colheita da madeira do fuste e colheita da madeira do fuste com casca), a maior quantidade de nutrientes exportados ocorreu no E. uroglobulus (N, K e S), E. urograndis (P, Mg e Cu) e E. saligna (Fe, Zn e B). Para o terceiro cenário (fuste e copa), a maior exportação de nutrientes ocorreu no E. urograndis, com exceção de S, onde a maior remoção ocorreu no E. uroglobulus. A colheita apenas da madeira do fuste apresentou a menor remoção de nutrientes do sistema, independente do genótipo.Palavras-chave: clones de Eucalyptus; nutrição de florestas; silvicultura; sustentabilidade Biomass production and nutrient content in different Eucalyptus genotypes in Pampa Gaúcho, Brazil Rev. Bras.