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 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.