Abstract• The objectives of this study were to measure litterfall production of the four floodplain forest types and to analyze the relationship between litterfall (forest type, dominant species, and organic fractions) and flood pulses.• Litterfall production was measured in two mono-specific stands of Salix humboldtiana or Tessaria integrifolia, respectively, and two mixed forests dominated by A. inundata or Nectandra angustifolia, during 1998 and the 2000-2002 periods.• Mono-specific stands presented similar productivities (6.8 and 6.5 Mg dry matter ha −1 y −1 , respectively), but differed significantly from the two other. The highest litterfall production was obtained during the large flood that occurred during 1998, decreasing later throughout the study period. Leaves were the dominant fraction of litterfall, followed by branches, flowers, and fruits.• Only S. humboldtiana, T. integrifolia and A. inundata forests showed distinct patterns of litterfall production, depending on the flooding pulse. N. angustifolia did not show a distinctive litterfall pattern.• The forests studied here presented patterns of litter production associated with the flood pulse according to its location along a topographic gradient, that controls the litter productivity of these forests.

INTRODUCCIÓNGran parte de la materia orgánica del suelo (MOS) deriva de la humificación de los residuos orgánicos que llegan al suelo tras su abscisión: hojas, ramas, flores, frutos y demás estructuras vegetales (incluso árboles enteros) que conforman la hojarasca. Esta MOS, tras su mineralización, libera bioelementos que pueden ser reabsorbidos por las plantas, contribuyendo así al ciclo biogeoquímico. Esta liberación de nutrientes, por tanto, está determinada, en última instancia, por las características genéticas de las especies, la variación anual de la composición de la hojarasca, sus propiedades físico-químicas y por las conAporte de hojarasca en bosques del predelta del río Paraná (Argentina) SUMMARYLitter production in four forests of the alluvial plain of the pre-Delta area in the Paraná River (Argentina) was studied during the period 1998-2002. Monospecific forests dominated by Salix humboldtiana (SSh) and Tessaria integrifolia (STi) presenting similar production (6.8 ± 1.2 and 6.5 ± 1.3 Mg dry matter ha -1 yr -1 , respectively), and pluri-specific forests of Albizia inundata (MAi) and Nectandra angustifolia (MNa), presenting statistical differences in their average production. Plurispecific forests also showed significant differences between them in terms of production (3.3 ± 0.5 and 9.6 ± 1.1 Mg dry matter ha -1 yr -1 , respectively). The highest values of litter production were obtained during 1998 (year of the highest overflooding); afterwards, it started decreasing during the period studied. A seasonal pattern of litterfall was enhanced with the flood pulse (spring-summer, primarily from November to February), except in the Mai forest, where trees are deciduous (autumn leaf abscission). Regarding the composition of the litter, leaves are the most abundant fractions (reaching 69% of the total in SSh forest), while reproductive structures account for less than 3% of the litter produced in all studied forests.Key words: litter production, alluvial plain, overflooding pulses, forest biomass. RESUMENSe estudió la caída de hojarasca en cuatro bosques representativos de la llanura aluvial del río Paraná, área predelta (Argentina), durante el período 1998-2002. Los bosques monoespecíficos dominados por Salix humboldtiana (SSh) y Tessaria integrifolia (STi) presentaron valores de producción aérea similares entre sí (6,8 ± 1,2 y 6,5 ± 1,3 Mg materia seca ha -1 año -1 , respectivamente) y se diferenciaron significativamente de los bosques mixtos de Albizia inundata (timbó blanco, MAi) y Nectandra angustifolia (laurel del río, MNa). Los bosques mixtos también presentaron diferencias significativas entre sí en cuanto a dicho aporte (3,3 ± 0,5 y 9,6 ± 1,1 Mg materia seca ha -1 año -1 , respectivamente); los valores más altos de aporte de hojarasca se obtuvieron durante 1998 (año de fuerte crecida del río), decreciendo luego durante el tiempo estudiado. Se observó un patrón de aporte de hojarasca estacional, que se acentuó con la finalización del pulso de inundación (primavera-verano, principalmente de noviembr...

Influencia de los atributos del paisaje en la ocupación de parches de bosque y en la demografía de Alouatta caraya en un ambiente fragmentado del noreste de Argentina Influence of landscape attributes on forest patch occupancy and demography of Alouatta caraya in a fragmented landscape of northeastern Argentina