Abstract This study evaluates litterfall production, forest floor mass and leaf-litter decomposition and growth in an 8-year- old Eucalyptus grandis stand and 467 treesha-1 and in another 16-year-old Pinus elliottii stand with 533 treesha-1, in the northeast of Corrientes, Argentina. In each stand, three permanent plots of 1000 m2 were established. Four collectors of 1.0 m2 and 12 litterbags of 20 cm2 were randomly distributed in each plot. The measurements were made over 3 years. The relationship between environmental factors and leaf-litterfall was analyzed using the Pearson correlation coefficient (r). The E. grandis stand showed an annual increment (IMA) of 25.2 m3ha-1year-1, a mean annual litter production (PAL) of 10.1 Mgha-1, an annual decomposition constant (K) of 0.7 and a half-life time (THL) of 1.0 years. The P. elliottii stand presented an IMA of 26.1 m3ha-1year-1, a PAL of 14.3 Mgha-1, a K of 0.6 and a THL of 1.15 years. The highest material fall occurred during the summer for both species with maximum monthly mean values of 1.5 Mgha-1 for E. grandis and 2.3 Mgha-1 for P. elliottii. The leaves were the most representative component of the fallen material. The climatic variable that presented the highest correlation with material fall was the average monthly temperature. The dynamics observed in the stands, production, formation of mulch and its decomposition are characteristic of subtropical forests.

Resumen Este estudio evalúa la producción de hojarasca, la acumulación y descomposición del mantillo y el crecimiento en un rodal de Eucalyptus grandis de 8 años de edad y 467 árbolesha-1 y en otro de Pinus elliottii de 16 años de edad y 533 árbolesha-1, en el nordeste de Corrientes, Argentina. En cada rodal fueron instaladas 3 parcelas permanentes de 1000 m2. Se distribuyeron 4 canastos de 1,0 m2 y 12 litterbags de 20 cm2, por parcela. Las mediciones fueron realizadas durante 3 años. La relación entre factores ambientales y caída de hojarasca se analizó mediante el coeficiente de correlación de Pearson (r). El rodal de E. grandis presentó un incremento medio anual (IMA) de 25,2 m3ha-1año-1, una producción de hojarasca anual media (PHA) de 10,1 Mgha-1, una constante de descomposición anual (K) de 0.7 y un tiempo de media vida (TMV) de 1,0 año. El rodal de P. elliottii presentó un (IMA) de 26,1 m3ha-1año-1, PHA de 14,3 Mgha-1, K de 0,6 y un TMV de 1,15 años. La mayor caída de material se presentó durante el verano para ambas especies con valores medios mensuales máximos de 1,5 Mgha-1 para E. grandis y de 2,3 Mgha-1 para P. elliottii. Las hojas fueron el componente más representativo del material caído. La variable climática que presentó mayor correlación con la caída de material fue la temperatura media mensual. La dinámica observada en los rodales, producción, formación de mantillo y su descomposición es característica de los bosques subtropicales.

ABSTRACT The objective of this study is to evaluate the damage caused by Acromyrmex heyeri Forel, 1899 and Acromyrmex lobicornis Emery, 1887 to Pinus taeda L. seedlings during the first two months after replanting. The experiment was conducted in the company Bosques del Plata, located in the province of Corrientes, Argentina. The evaluations were carried out at seven, 14, 21, 36, 50 and 65 days after replanting the seedlings, when the number of dead, alive, non-attacked, alive deneedled, and alive deneedled with cuts/damage to the apical bud by leaf-cutting ants was quantified. The results allow us to conclude that A. heyeri and A. lobicornis are responsible for losses to the order of 20.8% of the seedlings in an initial P. taeda stand at 65 days. The damage caused to seedlings by the two leaf-cutting ant species is constant over time, in which A. lobicornis is more voracious than A. heyeri.

RESUMO A presente pesquisa foi realizada com o objetivo de estudar e modelar o efeito dos desbastes pré-comerciais e das podas no crescimento diamétrico, em um povoamento de Pinus taeda L. de 15 anos de idade, no Nordeste da Argentina. O estudo localizou-se em solo vermelho argiloso profundo com um delineamento sistemático de faixas para intensidades de desbastes e subfaixas para intensidades de podas. Os tratamentos de desbaste, realizados aos 3 anos de idade, foram: 1666 (sem desbaste); 833; 416 e 208 árvores ha-1. As podas foram realizadas a partir dos 3 anos e com frequência anual por 2, 3 ou 4 anos consecutivos, com remoção de 30, 50 e 70% da copa viva, respectivamente. O modelo geral obtido por regressão linear permitiu estimar o diâmetro da árvore de área basal média (dg) em função da idade com boa precisão (desvio médio absoluto em percentagem igual a 5.71), sendo as variáveis: árvores remanescentes, copa remanescente e número de podas consideradas nos modelos estimadores dos coeficientes da função geral. Aos 15 anos de idade, os diâmetros variaram entre 25.6 e 41.5 cm, para as densidades de 1666 e 208 árvores ha-1, respectivamente, sem poda. O crescimento do dg foi afetado negativamente pelas podas e positivamente pelos desbastes.

ABSTRACT The aim of this research was to study and to model the effect of pre-commercial thinning and pruning on diameter growth, on a 15th year old stand of Pinus taeda L. in northeastern Argentina. The study was established in a deep red clay soil, with a systematic design of blocks for thinning intensity and sub-blocks for pruning intensity. The thinning treatments, performed at 3 year old were: 1666 (without thinning); 833; 416 and 208 trees ha-1. The pruning were done annually, starting at 3 year old, and applied by 2, 3 or 4 consecutive years removing 30, 50 and 70 % of the living crown, respectively. The general model obtained by linear regression allowed to estimate, with good precision (mean absolute deviation as a percentage equal to 5.71), the quadratic mean diameter (QMD) in function of age. The variable remnant trees, remnant crown, and number of prunings were considered to estimate the general function coefficients. At 15 year old, the QMD varied from 25.6 to 41.5 cm to 1666 and 208 trees ha-,1 respectively, without pruning. The QMD growth was negatively affected by pruning and positively affected by thinning.

RESUMO Com o objetivo de avaliar a sobrevivência e o crescimento de mudas de Pinus taeda produzidas em recipientes e em raiz nua com diferentes diâmetros do colo (DC) inicial, foram estabelecidos dois experimentos em solo de drenagem deficiente localizados na província de Corrientes, Argentina. O delineamento experimental utilizado foi o de blocos completos ao acaso, com três repetições por tratamento, sendo cada unidade experimental composta por 64 plantas e bordadura perimetral dupla. Os tratamentos avaliados, no experimento 1, foram mudas de recipientes com DC de 1,6 mm; 2 mm; 3 mm e 4 mm, e no experimento 2, foram mudas de raiz nua com DC de 3 mm; 4 mm; 5 mm e 6 mm. Aos 4 anos de idade, as mudas de recipientes não apresentaram diferenças significativas em sobrevivência e crescimento; enquanto que nas mudas de raiz nua, a sobrevivência foi maior nos tratamentos de 4 e 5 mm não se encontrando diferença significativa em crescimento entre os tratamentos. Para os dois tipos de produção de mudas, o diâmetro do colo não teve influência significativa no crescimento a campo.

ABSTRACT The aim of this research was to evaluate the survival and growth of Pinus taeda seedlings produced in containers and bare root with different collar diameters. Two trials were established in a poor drained area located in the Corrientes province, Argentina. The experimental design was randomized complete blocks, with 3 replications and experimental units with 64 seedlings with double lines buffer. The treatments evaluated on the trial 1 were seedlings produced in containers with collar diameter of 1,6 mm; 2 mm; 3mm and 4 mm and on the trial 2 were bare root seedlings with collar diameters of 3 mm; 4 mm; 5 mm and 6 mm. At 4-year-old the seedlings produced in containers did not showed significant differences in survival and growth however in the bare root seedlings production, the seedlings with 4 and 5 mm showed the best survival. No significant differences in growth were detected for all the treatments. For both types of seedling production the collar diameter did not showed significant influence in field growth.

ABSTRACT In order to describe the population structure of Myrocarpus frondosus Allemão, the structure of size class and the spatial distribution of the individuals species was studied, in a riparian area of the Paranaense Forest in Misiones, Argentina, at 27º39’00” S and 55º44’30” W. The species was studied in circular plots. All the individuals of Myrocarpus frondosus with diameter greater or equal to 10 cm (at 1.3 m height - DBH) were considered for the tree stage, and all seedlings with diameter ranging from 2 cm to 9.9 cm were considered for natural regeneration. Three hundred and ninety six individuals were found (431 ind. ha-1), with 180 individuals in the tree stage and 216 individuals in the natural regeneration stage. The results show that the diameter size of the population varied from 2 cm to 50 cm with reverse J distribution, representing a substantial recruitment in the younger age classes. The species presented a clustered pattern of spatial distribution.

RESUMEN Para describir la estructura poblacional de Myrocarpus frondosus Allemão fue estudiada una población de la especie, caracterizando los estadios de tamaño y la distribución espacial de los individuos, en un bosque en galería de la Selva Paranaense en Misiones, Argentina, a 27º39’00” S y 55º44’30” O. La especie fue estudiada en parcelas circulares. En las parcelas fueron considerados todos los individuos de Myrocarpus frondosus con diámetro DAP (a 1,3 metros de altura) mayor o igual a 10 cm para el estrato arbóreo y para la regeneración natural fueron considerados los plantines de la especie con DAP variando de 2 cm hasta 9,9 cm. Fueron encontrados 396 individuos (431 ind. ha-1), de los cuales 180 pertenecieron al estrato arbóreo y 216 correspondieron a la regeneración natural. Los resultados muestran que la amplitud de tamaño en diámetro varió desde 2 cm hasta 50 cm, con una distribución de la población estudiada en forma de J invertida, representando una población con substancial reclutamiento de individuos en sus primeras etapas de desarrollo. La especie presentó un patrón agrupado de distribución espacial.

RESUMO O presente trabalho teve como objetivo avaliar o crescimento de mudas de Eucalyptus globulus subsp. maidenii em resposta a diferentes doses de NPK, originadas da combinação de fertilizantes de liberação rápida e lenta. O estudo foi realizado em casa de vegetação climatizada, localizada no Centro Tecnológico de Silvicultura, pertencente ao Departamento de Ciências Floretais da Universidade Federal de Santa Maria-RS, no perído de setembro a dezembro de 1997. As plantas foram cultivadas em substrato à base de uma composto orgânico de casca de Pinus spp.. O delineamento utilizado foi o inteiramente casualizado, constando de 4 tratamentos, constituídos de doses de fósforo (superfostato simples (0-18-0)) e de um fertilizante de liberação lenta N-P-K (1414-14) denominado Osmocote, sendo derivado de nitrato de amônio, fosfato de amônio, fosfato de cálcio e sulfato de potássio. Os tratamentos, resultantes da combinação de 60% de superfostato simples e 40% de osmocote foram 0,0; 2,5; 5,0 e 7,5 Kg m-3 de substrato. Para cada tratamento foram usadas 4 repetições, sendo cada uma composta de 11 plantas. Ao final de 100 dias, foram avaliados a altura, o diâmetro do colo, a massa seca da parte aérea, a massa seca do sistema radicular e o número de folhas. Pelos resultados obtidos verificou-se que o crescimento das plantas de Eucalyptus globulus subsp. maidenii, respondeu positivamente à fertilização NPK [60% Super Simples (0-18-0) + 40% fertilizante de liberação lenta (14-14-14)]. Quando não foi aplicado fertilizante as mudas apresentaram um menor crescimento enquanto que os máximos crescimentos em altura, diâmetro do colo, massa seca da parte aérea, massa seca radicular e número de folhas foram obtidos no intervalo de doses de 6,7 a 7,5 Kg m-3 de substrato.

ABSTRACT The present study has had as its objectives to evaluate the seedlings of Eucalyptus globulus subspecies maidenii, in response to different NPK originated from the combination of slow release and quick release fertilizers. The study was conducted in a climatized green house at a the Technological Center of Forestry, in the Forest Department of the Federal University of Santa Maria-RS, from September to December of 1997. The plants were cultivated in a compost of pine bark substrate, in a completely randomized design, consisting of 4 treatments which consisted of Phosphorus dosages (60% of Super Simple (0-18-0)) and a slow release NPK fertilizer (14-14-14), known as Osmocote, which derived from ammonium nitrate, ammonium phosphate, calcium phosphate and potassium sulfate. The treatments, resulting from the combination of 60% super simple and 40% osmocote were 0,0; 2,5; 5,0 and 7,5 Kg m-3 of substrate. There were 4 repetitions of 11 plants for each treatment. After 100 days the height, collar diameter, above-ground dry matter, root dry matter and number of leaves were evaluated. The results indicate that the E. globulus subsp. maidenii seedlings growth responded positively to NPK fertilization [60% of Super Simple (0-180)+40% of slow release fertilizer (14-14-14)]; when the fertilizer was not applied the seedlings did not grow as much while the maximum increment in height, collar diameter, above-ground dry matter, root dry matter and number of leaves were obtained in the dosage range of 6,7 Kg m-3 to 7,5 Kg m-3 of substrate.