The Fluvial Forests as Indicators of the Flow and Permanence of Water

We evaluated the influence of the horizontal flows of the Paraná River on the composition and distribution of the floodplain landscape and we defined the ecohydrologicalsignature of some species-index in the low Paraná River section, (27° 38? 04? S and 58° 50? 46? W). During the drought phase, the structure of the vegetation were characterizad using a Cottam & Curtis method. The trees were positioned in the topographic gradients during the flood phase, taking as reference the river water sheet in the nearest hydrometric gauge. To obtain the pulse attributes in different positions of the geomorphological gradient, PULSO software was used considering the daily water levels at Corrientes city between 1985 and 2015. Two main types of flooded forests were identified: pionner forest, dominated by one or two species (Salix humboldtiana, Tessaria integrifolia) in recent bars and islands, and pluri-specific flooded forests (Albizia inundata, Cecropia pachystachya, Croton urucurana, Inga uruguensis, Ocotea diospyrifolia, Nectandra angustifolia and Peltophorum dubium) occupying bars of the highest islands, with shorter flood phases, with trees are distributed in 2-3 strata in a closed canopy. Pulses were more frequent in pioneer forests than in multispecific forests. The ecohydrological signature allows the optimum condition and distribution limits of each species to be established. It is a tool to know the adjustment of biotic elements (populations) to the river variability regime. The procedure usedcan be used to anticipate the possible reorganization of the river plain landscape as a result of flow variations predicted by climate change models.Fil: Zambiasio, Violeta Amancay. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Casco, Sylvina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Neiff, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

Tasa de crecimiento de espigas de trigo (Triticum aestivum) en diferentes niveles de radiación incidente en Corrientes

El trigo (Triticum aestivum) es el cultivo invernal más importante de Argentina y en la región NEA es utilizado en la rotación. En condiciones potenciales, el crecimiento del cultivo depende de la radiación solar y de la temperatura, que se vinculan en el cociente fototermal (Q). En el intervalo desde 20 días prefloración a 10 días posfloración se genera el número de granos (NG), el cual está ligado al crecimiento de espigas (CE) durante este período. El objetivo de este trabajo fue determinar el efecto de la radiación solar en el período de crecimiento de espigas de trigo y relacionarlo con el rendimiento potencial. Se instalaron experimentos en el Campo Experimental de la Facultad de Ciencias Agrarias (UNNE), Corrientes, durante los años 2009 y 2010. Se sembró la variedad Baguette 13 el 29 de mayo y el 2 de junio respectivamente, sin limitantes hídricas ni nutricionales, y se ensayaron tres niveles de radiación aplicados durante el período de crecimiento de espigas (testigo, S50% y S80%). Se determinó el rendimiento, sus componentes numéricos (NG y PG), CE y la eficiencia del uso de la radiación (EUR). Los rendimientos promedio de ambas campañas oscilaron entre 6895,55 y 3402,10 Kg ha-1 (p=0,0002); mientras que el NG osciló entre 17245,91 y 9267,36 (p=0.0004). En el PG, el testigo (40,00 g) se diferenció de los tratamientos S50% y S80% (p=0.0930), no encontrándose diferencias entre los dos últimos (37.63 y 37.90 g respectivamente). Se ajustaron tres ecuaciones diferentes para el CE. Se encontraron asociaciones entre rendimiento y NG (R²=0.98), y éste último se asoció positivamente (r=0.62) con el peso de espigas al finalizar el período de crecimiento de las mismas.Wheat (Triticum aestivum) is the most important winter crop in Argentina. In the North East region, it is commonly used in rotation. Potential growth depends on solar radiation and temperature, combined in the photothermal quotient (Q). The grain number (GN) is determined in the interval from 20 days before to 10 days after anthesis, and this is related to spike growth (SG) during this period. The aim of this study was to determine the effect of solar radiation on the spike growth period of wheat, and to relate it to yield potential. Two experiments were performed in the experimental field of Facultad de Ciencias Agrarias (UNNE), Corrientes, during the growing seasons of 2009 and 2010, under potential conditions (i.e., without water and nutrient limitations). Baguette 13 variety was planted on May 29 and June 2, and three radiation levels were tested during the spike growth period (control, S50% and S80%). Yield, its numerical components (GN and GW), SG and radiation use efficiency (RUE) were determined. Average yields of both years ranged from 6895.55 to 3402.10 kg ha-1 (p = 0.0002), NG varied between 17245.91 and 9267.36 (p= 0.0004) and, for GW, the control (40.00 g) differed from the S50 and the S80 treatments (p = 0.0930), with no differences between the last two (37.63 and 37.90 g, respectively). Three different equations were fitted to SG. Associations were found between yield and GN (R²= 0.98), and the last one was positively associated (r = 0.62) with spike weight at the end of the spike growth period.Fil: Balbi, Celsa N.. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; ArgentinaFil: Rodríguez, Erica. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; ArgentinaFil: Neiff, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentin

Distribution pattern of trees in a hydrological gradient below the Paraná-Paraguay River confluence

Riparian and riverine aquatic plant species have evolved within the context of flowing water habitats for which the flooding and droughts are the forcing factors that shape the community features, either through a positive or negative effect on the ecosystem’s function, according to the timing, frequency and magnitude of such events. In the Paraná floodplain landscape, topographic position is a crude indicator of the position along the complex gradient, but it also includes information about flood/drought periods and trees’ resilience to extreme hydrological phases. We present the occurrence of major tree species in riparian forests of the Paraná River on islands of different topographies in a section of the Paraná River downstream from the confluence with the Paraguay River. Our results suggest that each tree species had a preferred position in the topographic gradient, sites where the observed counts were more frequent. This trees species were more frequent between 2 and 8 m in the topographic position and were affected by 5 and 202 hydrosedi- mentologic pulses between 1949 and 1999. We suggest that knowledge of the distribution curves of the vegetation spe- cies present can help draw possible future scenarios of the river landscape. Future engineering works to alter the hydro- logical dynamics of Paraná should pay more attention to the distribution of riparian forests because they are indicators of changes at the landscape level and they are the support for the wildlife of the river.Fil: Casco, Sylvina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Centro de Ecologia Aplicada del Litoral (i); Argentina;Fil: Neiff, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Centro de Ecologia Aplicada del Litoral (i); Argentina

Selectivity of the gill- nets as the management tool of fish resource in the confluence of Parana and Paraguay riverine system

Esta contribución trata sobre las pesquerías de la Confluencia de los ríos Paraná - Paraguay. Comparamos las capturas de peces usando redes agalleras, con diferente tamaño de mallas, de 22 centímetros a 31 centímetros entre nudos, para determinar la selectividad y la eficacia de la pesca y conocer la malla de tamaño más apropiado, la que admite que el pez pueda reproducirse al menos dos veces antes de ser capturado. Con este objetivo, estudiamos las capturas de peces en Barranqueras (Chaco, Argentina) de 1990 a 1999, para peces de interés de comercial. Llegamos a la conclusión de que el tamaño de malla más apropiado debe ser de 27 cm., para admitir la renovación del stock pesquero.This paper deals with the fisheries of the Paraná-Paraguay Confluence riverine system. We compared the captures of fishes using gill-nets, with different size of meshes, from 22 cm to 31 cm between knots to determine the selectivity and effectiveness of the fishing and to know the most appropriate size mesh, the one that allows at least two reproductive events before being captured. With this objective, we study the captures of fish at Barranqueras (Chaco, Argentina) from 1990 to 1999, for the species of commercial interest. We conclude that the most appropriate mesh size of the gill-nets should be of 27 cm, to allow the renovation of the fishing stockFil: Neiff, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Canon Veron, Marta Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin

Aporte de las plantas de Eichhornia crassipes a la acumulacion de materiales organicos e inorganicos

#Eichhornia crassipes est l'une des plantes les plus abondantes de la plaine d'inondation du fleuve Parana. Les détritus formés dans les îles flottantes s'accumulent à l'interface eau-sédiment ou bien dans le système racinaire des plantes. La quantité de matière organique et minérale déposée par #E. crassipes a été mesurée dans un réservoir (10 m x 2 m x 1,5 m de profondeur). Le réservoir a été rempli avec de l'eau d'un bras mort de la plaine d'inondation et #E. crassipes y a été ajoutée. Dans ces conditions la production nette des plantes a été de 1743 g/m2/an. La moyenne annuelle de matière organique sédimentée sous #E. crassipes a été de 5,1 g/m2/jour, avec des variations saisonnières significatives. Le maximum de dépôt de matière minérale et organique a eu lieu en mars et le minimum en août. La teneur en matière organique fine représentait 40 à 69% de ce dépôt. (Résumé d'auteur

Efecto de las crecidas sobre las poblaciones de invertebrados que habitan macrofitas emergentes en islas del rio Parana

Les échantillons ont été prélevés de janvier 1982 à janvier 1983 dans les franges à #Panicum grumosum et à #Polygonum acuminatum des îles Palomera et Choui, qui sont situées sur le Parana à 45 km en aval de sa confluence avec le Paraguay. Durant la période d'étude, des périodes de hautes et de basses eaux ont été observées, y compris une crue exceptionnelle au cours des derniers mois. En période de basses eaux, les invertébrés associés à la végétation suivent une distribution d'abondance log-normale, avec une forte densité et une diversité de 3,81 bits. Les Copépodes, Cladocères, Oligochètes, et Ostracodes forment les groupes les plus abondants. Lors des périodes prolongées de forte crue, l'abondance et la diversité diminuent, et la distribution est du type géométrique. Durant les crues de plus faible durée, la distribution d'abondance relative est semblable à celle des basses eaux. (Résumé d'auteur

Feeding spectra and activity of the freshwater crab Trichodactylus kensleyi (Decapoda: Brachyura: Trichodactylidae) at La Plata basin

Background: In inland water systems, it is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments. The aim of this study is to analyze the natural diet of Trichodactylus kensleyi of subtropical rainforest streams and corroborate the temporal variation in the trophic activity during day hours. Results: A total of 15 major taxonomic groups were recognized in gut contents. The index of relative importance identified the following main prey items in decreasing order of importance: vegetal remains, oligochaetes, chironomid larvae, and algae. A significant difference was found in the amount of full stomachs during day hours showing a less trophic activity at midday and afternoon. The index of relative importance values evidenced the consumption of different prey according to day moments. Results of the gut content indicate that T. kensleyi is an omnivorous crab like other trichodactylid species. Opportunistic behavior is revealed by the ingestion of organisms abundant in streams such as oligochaetes and chironomid larvae. The consumption of allochthonous plant debris shows the importance of this crab as shredder in subtropical streams. However, the effective assimilation of plant matter is yet unknown in trichodactylid crabs. Conclusions: This research provides knowledge that complements previous studies about trophic relationships of trichodactylid crabs and supported the importance of T. kensleyi in the transference of energy and matter from benthic community and riparian sources to superior trophic levels using both macro- and microfauna.Fil: Williner, Verónica. 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; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; ArgentinaFil: de Azevedo Carvalho, Debora. 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: Collins, Pablo Agustin. 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; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentin

El pleuston de Pistia stratiotes de la laguna Barranqueras (Chaco, Argentina)

A floating carpet of Pistia stratiotes in the “Barranqueras” pond (near Paraná river) has been studied in their vegetation and faunal composition during the period October, 1974 to December, 1975 by monthly sampling operations.The samples were collected in several points along the main radial section by mean a special circular sampler with 32 cm diameter. In the freíd operations, also were taken structural data of vegetal population, like density, plant size, growth phases, and general fenology, recording at the same time the most interesting limnological parameters.In the laboratory, the animáis were removed by washing the vegetation in sieves of different size, followed by Berlese funnel treatment. The material was identified at the best posible systematic level, estimating the numerical density and the biomass. The population of aquatic invertebrates associated with Pistia stratiotes varied between 3200 and 18000 organisms/m^, and the standing crop was less than 4,45 g/m2 (dry weigth). The result did not exceed 21,5 g/m2 including the macrofauna.The vegetal biomass fluctuate between 394 and 166 g/m^ (dry weigth) According to the data obtained, the mesofauna never reach 5 o/o of the total vegetal biomass, attaining a maximun of 8 o/o if the macrofauna are considered

Cambios estacionales en la biomasa de Eichhornia crassipes (Mart.) Somls y su fauna en una laguna del Chaco (Argentina)

Biomass determinations were made in natural stands of Eichhornia crassipes throughout two year. The samples were monthly collected with a 62 cm diameter ring. The values indicated in the text are the averages of five replicates taken in a transection from a littoral to a central position.The annual net production was obtained from the difference between the final and initial biomass.Four functional compartments were considering: total standing crop; green leaves, roots and rhizomes biomass; dead attached leaves and litter. The greatest total standing crop found in mid summer, was 25 Tn/ha. In the same period, the máximum biomass was recorded. The roots and rhizomes have representad between 31 and 55% of the biomass.The máximum rate of biomass change was found in setember (6,30 Tn/ha).Losses by death (attached leaves and litter) were small before the seasonal máximum plant biomass. The litter ocurring in spring time, has been produced during the last winter.The fauna biomass in the Barranqueras pond was much lower than in other subtropical lakes (8 g/m3 in winter and 16 g/m3 in summer).The high losses from a E. crassipes community are related with the fast activity of the fitofagous during the summer

Enemigos naturales de Eichhornia crassipes en el nordeste argentino y posibilidades de su aplicación al control biológico

In the lentic shallow water bodies related to the Paraná and Paraguay rivers, the water hyacinth (Eichhornia crassipes) forms dense populations that may cover the entire surface of the water, determining strong limnological changes with severe negative impacts on other aquatic communities. Lower temperatures and hydrological factors—particularly river floods—regulate the areal cover and density of such populations. However, as the progressive damming of the rivers reduces the impact of floods, the large populations of water hyacinth may represent a real risk to biological productivity, water quality, navigation, recreational activities, and several other practical purposes. This paper deals with the evolution of the plants and the associated fauna in natural populations of water hyacinth in some ponds and oxbows related to the Paraná River in Chaco Province (Argentina), over the course of an annual cycle, with the aim of contributing to the development of biological control methods. Vegetal and animal fluctuations are discussed in order to determine the quantitative damage to the plant, along with some observations on the biology of potential control agents.En los cuerpos de agua lentos y poco profundos asociados a los ríos Paraná y Paraguay, el camalote (Eichhornia crassipes) forma poblaciones densas que pueden cubrir toda la superficie del agua, provocando cambios limnológicos significativos con un impacto negativo severo sobre otras comunidades acuáticas. Las bajas temperaturas y los factores hidrológicos —particularmente las crecidas de los ríos— regulan la cobertura superficial y la densidad de dichas poblaciones. Sin embargo, a medida que el embalsamiento progresivo de los ríos reduce el impacto de las crecidas, las grandes poblaciones de camalote pueden representar un riesgo real para la productividad biológica, la calidad del agua, la navegación, las actividades recreativas y diversos otros usos prácticos. Este trabajo trata sobre la evolución de las plantas y la fauna asociada en poblaciones naturales de camalote en algunos estanques y meandros abandonados relacionados con el río Paraná en la provincia del Chaco (Argentina), a lo largo de un ciclo anual, con el objetivo de contribuir al desarrollo de métodos de control biológico. Se discuten las fluctuaciones vegetales y animales con el fin de determinar el daño cuantitativo a la planta, junto con algunas observaciones sobre la biología de los posibles agentes de control