Changes in vegetation composition and structure following livestock exclusion in a temperate fluvial wetland

Questions: Responses of wetland systems to grazing can be highly variable with both positive or negative responses. However, the sustainable use of wetlands for grazing will depend on the management implemented and the resilience of each type of them. In this context, we addressed the question: will the vegetation in the studied wetland be able to recover its structural and functional parameters in the short term after livestock exclusion?. Location: Temperate fluvial wetlands in the middle Delta of the Paraná River, Argentina, South America. Methods: We evaluated the effect of cattle ranching on vegetation composition and diversity by determining changes in species richness and evenness, biomass (green and dry vegetative, and reproductive biomass), and litter content. We also analyzed the changes in biomass of weeds and of species according to their forage quality, toxicity, and growth form. We applied a randomized block design (by topographic position) with repeated measures over time, using livestock exclusion as treatment. Results: After 16 months, livestock exclusion affected vegetation species richness, but did not have a significant effect on diversity due to a slightly compensatory effect of evenness. Species composition differed markedly among treatments over time. There was an increase in dry and green vegetative biomass and litter content after eight months of exclusion, while changes in reproductive biomass occurred later. The increase in these variables was closely related to changes in biomass of species with erect habit and good forage quality. Conclusions: Livestock exclusion increased the forage value for the studied wetland by the development of natural palatable species typical of these environments. This shift in species composition promoted a higher production in biomass in the ungrazed areas. This suggests a remarkable recovery of the structural and functional parameters of the vegetation communities in the short term (two years).Fil: Magnano, Andrea Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Krug, Cecilia Pamela. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; ArgentinaFil: Casa, Valeria. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; ArgentinaFil: Quintana, Ruben Dario. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; Argentin

Temporal variation of bird assemblages in a wetland: influence of spatial heterogeneity

The temporal variation of bird assemblages at three sites within a wetland of the Parana River was examined. The aim was to obtain an overview of the influence of spatial heterogeneity on communities in such a variable environment as the wetlands. We recorded 1,662 individuals belonging to 139 species from 40 families. There were no significant differences between sites in richness, abundance nor diversity. Species richness in the first year was greater than during the second year. Number of resident and migrant species decreased in the second year. Community composition differed between the two years of study and was significantly different among seasons. Species were grouped into 19 trophic guilds. In this study, number of species and their abundances were not significantly different among sites; there were differences in the composition of birds among sites. Thus, the structure of the environments influenced the composition of assemblages in different areas. Guild composition remained fairly constant between years and among seasons. Geomorphological and hydrological dynamics of the river produce a heterogeneous availability of habitats and resources that affect the composition of bird assemblages. Annual and seasonal changes in meteorological variables can lead to changes in the structure and/or composition of those assemblages.Fil: Ronchi Virgolini, Ana Laura. Universidad Autónoma de Entre Ríos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lorenzón, Rodrigo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Blake, John G.. University of Florida; Estados UnidosFil: Beltzer, Adolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin

Pre-hispanic settlements in hydrometeorologically susceptible areas during the late Holocene: The Upper Delta of the Paraná River case

In this paper, we present the results of the geoarchaeological studies carried out in two archaeological localities of the Upper Delta of the Paraná River (Argentina). The main objective of these studies is to depict the pre-Hispanic strategies involved in the colonization and settlement of southern South America wetlands. Paraná Delta is one of the most conspicuous areas of these lowlands and comprises a large wetland macrosystem. Its current geomorphological configuration was established after the last transgressive mid-Holocene event c. 600014C yr BP. In this environment, a high ecological heterogeneity, with diverse and abundant tropical and temperate biota, was developed. These features were important factors to the human colonization and utilization of these wetlands. However, this environment has the highest hydrometeorological susceptibility of La Plata basin. This susceptibility had an impact on settlement systems and resource exploitation strategies established in the area since at least 200014C yr BP. These strategies involved at least two settlement types: semi-permanent residential camps and transitory camps oriented to exploit particular resources. The semi-permanent settlements were located in anthropogenic elevated mounds, locally known as ‘cerritos’, and were not subjected to seasonal inundations. Conversely, the transitory camps are found in levees exposed to recurrent flooding.Fil: Castiñeira Latorre, Carola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Mineralogía y Petrología; ArgentinaFil: Apolinaire Vaamonde, Eduardo Saúl. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Arqueología; ArgentinaFil: Blasi, Adriana. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Mineralogía y Petrología; ArgentinaFil: Bonomo, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Arqueología; ArgentinaFil: Politis, Gustavo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Investigaciones Arqueológicas y Paleontológicas del Cuaternario Pampeano. Universidad Nacional del Centro de la Provincia de Buenos Aires. Investigaciones Arqueológicas y Paleontológicas del Cuaternario Pampeano; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Arqueología; ArgentinaFil: Bastourre, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Arqueología; ArgentinaFil: Mari, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentin