Pablo G. Aceñolaza

Litterfall production in forests located at the Pre-delta area of the Paraná River (Argentina)

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.Résumé• Cette étude avait pour but de mesurer la production de litière dans quatre forêts alluviales et d’analyser les relations entre les litières (selon le type de forêt, l’espèce dominante, et des fractions organiques) et les crues du fleuve Paraná (Argentine).• La production de litière a été mesurée dans deux forêts monospécifiques de Salix humboldtiana ou de Tessaria integrifolia, et dans deux forêts mixtes où l’espèce prédominante était soit Albizia inundata soit Nectandra angustifolia. Cette étude a été menée en 1998 puis de 2000 à 2002.• Les forêts monospécifiques présentent des productions de litières similaires (6.8 et 6.5 Mg matière sèche ha−1 ans−1 respectivement) et étaient significativement différentes des deux forêts mixtes. La plus forte production de litière a été obtenue au cours de la grande crue de 1998, puis a diminué progressivement au cours du temps. Les feuilles représentaient la principale fraction des litières, tandis que les branches, les fleurs et les fruits constituent des fractions mineures.• Les forêts dominées par S. humboldtiana, T. integrifolia et A. inundata ont vu leur production de litière évoluer en fonction des crues du fleuve Parana. Ce type de relation entre crue et production de litière n’a pas été détecté dans le cas des forêts de N. angustifolia.• Il existe ainsi une relation entre la production de litière et la hauteur des crues, elle-même conditionnée par un gradient topographique, qui détermine donc la production de litière de ces forêts.

Litterfall production of forests at the pre-Delta area of the Paraná River (Argentina)

SUMMARY Litter production in four forests of the alluvial plain of the pre-Delta area in the Parana 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.

A phytosociological analysis of Butia yatay (Arecaceae) palm groves and gallery forests in Entre Rios, Argentina

Multivariate floristic analyses of Butia yatay palm groves and gallery forest associated with the Uruguay River basin of Entre Rios Province (Argentina) were performed, including vegetation stands of Rio Grande do Sul State (Brazil). Several new phytosociological associations were identified. These include Eugenio myrcianthis–Butietum yatay association, which represents palm groves on sandy soils evolved from ancient river deposits, and Bignonio callistegioidis–Terminalietum australis association, which represents some gallery forests on regular floodplains of the Uruguay River. Both are placed in the new Pampean alliance Guettardo uruguensis–Bution yatay, which is part of the Dyckio brevifoliae–Terminalietalia australis order and Sebastianio schottiae–Terminalietea australis class, which has been described for Brazil.

Análisis espacial del riesgo de establecimiento de Lymantria dispar en bosques nativos de Sudamérica

Resumen en: Lymantria dispar is a quarantine pest absent in South America. A regional phytosanitary surveillance plan was developed to control this pest due to its h...