RESUMO O presente estudo teve por objetivo quantificar a massa e o estoque de nutrientes da serapilheira sobre o solo em um fragmento de Floresta Estacional Decidual no município de Itaara, RS. Para a quantificação da serapilheira, a amostragem foi realizada conforme frações estabelecidas em metodologias: uma para folhas e galhos com diâmetro menor a 1 cm (S0) e outra para material lenhoso com diâmetro de 1 cm a 3 cm (S1), 3,1 cm a 6 cm (S2) e maior que 6 cm (S3). Para a avaliação da fração S0, foram coletadas aleatoriamente cinquenta amostras com moldura metálica de 25 cm x 25 cm, já para a avaliação das frações S1, S2 e S3, foram distribuídas aleatoriamente dez parcelas de 3 m x 2 m na área de estudo. O material amostrado foi acondicionado e levado ao Laboratório de Ecologia Florestal da Universidade Federal de Santa Maria onde foram secas, pesadas, moídas e analisadas quanto aos teores de macro e micronutrientes. Cerca de 45% da serapilheira depositada sobre o solo é formada por materiais lenhosos senescentes (galhos e troncos). As frações da serapilheira diferiram significativamente (p < 0,05), quanto aos teores de nutrientes, com exceção de Mg e Cu; geralmente a fração S0 apresentou teores mais altos de nutrientes. As frações S1, S2 e S3 apresentaram um acúmulo de nutrientes variando de 53,3% para o K a 8,7% para o Fe em relação ao total da serapilheira, demonstrando a importância da quantificação desses componentes durante a avaliação do estoque de nutrientes contidos na serapilheira de ecossistema florestal.

ABSTRACT The aim of the present study was to quantity aboveground mass and nutrients in a deciduous seasonal forest fragment in the district of Itaara, RS, Brazil. For quantification and fractionation of the litter, sampling was carried out using two methodologies: the first one for leaves and branches with diameter smaller than 1 cm (S0) and the second one for woody material with diameter varying from 1 cm to 3 cm (S1), 3.1 cm to 6 cm (S2), and greater than 6 cm (S3). To evaluate the S0 fraction, 50 randomly sample were collected with a metallic frame of 25 cm x 25 cm, and for S1, S2 and S3 10 plots of 3 m x 2 m were distributed randomly in the area of study. Samples was packed and taken to the Laboratory of Forest Ecology of the Universidade Federal de Santa Maria, where they were dried, weighed, ground and analyzed for nutrient contents. The woody senescent litter represented about 45% of the litter layer. Litter classes differed statistically in relation to nutrient content (p < 0.05), except for Mg and Cu; usually the S0 fraction presented higher contents. The fractions S1, S2 and S3 showed an accumulation of nutrients ranging from 53.3% to 8.7% K for Fe in the total litter, demonstrating the importance of quantification of these components during the evaluation of nutrient stocks contained in the litter of the forest ecosystem.

The aim of the present work was to evaluate the litter production and decomposition in a mixed araucaria forest in the south of Brazil. The vegetation of the area is characterized by two forest types: forest type I, with the upper canopy dominated by Araucaria angustifolia; and forest type II, with higher diversity of tree species, predominantly broad-leafed species in the dominant canopy strata. To evaluate the litter production, 20 wood traps with 0.25 m² of surface were installed. Ten samples of 0.25 m² were monthly collected from the litter layer. Litter decomposition was evaluated from the instantaneous decay rate (K). The average of three years concluded that litter production did not differ significantly in the two types of forest studied: 7,661 kg ha-1 year-1 in forest type I and 8,624 kg ha-1 year-1 in forest type II. The months with the highest production in forest type II were correlated with periods of higher precipitation (spring and summer). The litter layer was significantly different for the two forest types, being heavier in forest type I with values of 9,924 kg ha-1 and 7,906 kg ha-1 for forest type II. The area with predominance of Araucaria angustifolia presented a slower rate of litter decomposition and nutrient release.

El objetivo del presente trabajo fue evaluar la producción y descomposición de hojarasca de la selva ombrófila mixta en el sur de Brasil. La vegetación del área presentó dos tipos forestales: I, cuyo dosel superior estaba dominado por Araucaria angustifolia y II, con mayor diversidad de especies arbóreas predominando latifoliadas en el estrato superior. Para evaluar la producción de hojarasca fueron instalados 20 colectores de 0,25 m² de superficie. Para la cuantificación del mantillo, mensualmente se retiraron 10 muestras de 0,25 m². La descomposición de la hojarasca fue determinada a partir de la tasa instantánea de descomposición (K). De los resultados observados en tres años de estudio se concluye que la producción de hojarasca no difirió significativamente en los dos tipos forestales estudiados, con 7.661 kg ha-1año-1 en el tipo forestal I y 8.624 kg ha-1año-1 en el tipo forestal II. Los meses de mayor cantidad de hojarasca en el tipo forestal II estuvieron correlacionados con períodos de mayores precipitaciones (primavera y verano). Para el mantillo hubo diferencias significativas entre los dos tipos forestales, presentando mayor cantidad el tipo forestal I con valores de 9.924 kg ha-1 y de 7.906 kg ha-1 el tipo forestal II. El bosque con predominio de Araucaria angustifolia presentó una tasa de descomposición y una liberación de nutrientes más lentas.

The effect of weed control on the stand growth of 4-year-old Pinus taeda L., Pinus elliottii Engelm. var. elliottii L. & D. and Pinus elliottii var. elliottii x Pinus caribaea var. Mor. hondurensis B. & G. was investigated in Northeast Corrientes Province, Argentina. Data from 21 treatments were evaluated (three species with two area intensities and weed control, and three periods of weed control, plus a further check without such control). A statistical pattern of complete blocks was taken at random, with three repetitions and 36 plant plots. Plant survival was not affected by the weed control. The band or total weed control area did not influence the growth of Pinus taeda and Pinus elliottii var. elliottii, which gained a volume during the monitoring of 85.6% and 85.2%, respectively. For Pinus elliottii var. elliottii x Pinus caribaea var. hondurensis the response was greater, increasing the control surface area and generating volume differences of 114.4% (total) and 69.7% (band). There was no difference in growth when weed control was applied for up to three periods; the general average volume increase during the observation was 88.6%. Pinus elliottii var. elliottii x Pinus caribaea var. hondurensis exhibited the greatest growth.

Se estudió el efecto del control de malezas en el crecimiento de una plantación de Pinus taeda L., Pinus elliottii Engelm. var. elliottii & L. & D. y Pinus elliottii var. elliottii x Pinus caribaea var. hondurensis B. & G., de 4 años de edad, localizada al NE de la provincia de Corrientes, Argentina. Fueron evaluados 21 tratamientos (3 especies x 2 intensidades de área con maleza controlada x 3 períodos de control de malezas + un testigo sin control de malezas por especie). Se utilizó un diseño estadístico de bloques completos al azar con 3 repeticiones y parcelas de 36 plantas. La sobrevivencia no fue afectada por el control de malezas. El control de malezas en la banda o en la totalidad del área no presentó diferencias de crecimiento para las especies Pinus taeda y Pinus elliottii var. elliottii, generando una diferencia volumétrica con el testigo del 85,6% y 85,2% respectivamente. Para Pinus elliottii var. elliottii x Pinus caribaea var. hondurensis la respuesta fue mayor al aumentar la superficie controlada, generando diferencias del 114,4% (total) y del 69,7% (banda). No existieron diferencias de crecimiento al ser realizado el control de malezas por 1, 2 ó 3 períodos; la diferencia volumétrica media general con el testigo fue del 88,6%. La especie Pinus elliottii var. elliottii x Pinus caribaea var. hondurensis presentó los mayores crecimientos.