Resumo: Pontederia crassipes é uma planta aquática flutuante livre nativa da América do Sul, que colonizou rios tropicais em vários continentes, tornando-se dominante nas planícies aluviais. Objetivo Neste estudo testamos a relação entre o comprimento das folhas e a biomassa foliar, e comparamos a precisão da estimativa fenométrica indireta com a biomassa direta acima do solo. Métodos Recolhemos folhas verdes de aguapé com diferentes tamanhos num lago de planície de inundação do rio Paraná (Argentina). As folhas foram secas em estufa de laboratório para obter um peso seco constante. Para determinar a acuracidade da estimativa fenométrica indireta foi comparada com a biomassa direta para a parte aérea. A análise de regressão foi utilizada para testar a relação entre o peso e o comprimento das folhas. O comprimento de 279 folhas verdes variou entre 7 e 115 cm. Resultados O método não destrutivo foi um bom preditor da biomassa foliar (R2 = 0,87 p < 0,0001). Não foram encontradas diferenças significativas entre o peso seco obtido diretamente e o peso estimado através do método indireto. Conclusões Os nossos resultados sugerem que o comprimento da folha é um bom atributo para estimar a biomassa aérea de P. crassipes. Este método é útil para reduzir o impacto do método direto de colheita de aguapé e necessário para aplicação em estudos experimentais que determinam a duração da vida foliar e a produtividade primária em clones. Resumo Sul continentes tornandose tornando se aluviais solo Argentina. Argentina . (Argentina) constante 27 11 cm R2 R (R 087 0 87 0,8 0,0001. 00001 0,0001 0001 0,0001) indireto P clones (Argentina 2 1 08 8 0, 0000 0,000 000 0,00 00 0,0

Abstract: The water hyacinth, Pontederia crassipes, is a free-floating aquatic plant native to South America, which has colonized tropical rivers in several continents and has become dominant in floodplains. Aim This study aimed to evaluate the relationship between leaf length and leaf biomass (as an indirect phenometric estimation) and to compare the accuracy of the indirect phenometric estimation (which is a non-destructive method) with that of the direct estimation of aboveground biomass (which is destructive). Methods Pontederia crassipes green leaves of all sizes were collected from a floodplain lake of the Paraná River (Argentina). The leaves were oven-dried in the laboratory to obtain the constant dry weight. To determine the accuracy the indirect phenometric estimation was compared with the direct estimation of aboveground biomass. The relationship between leaf weight and leaf length was evaluated by regression analysis. The length of the 279 green leaves collected ranged between 7 and 115 cm. Results The non-destructive method was a good predictor of leaf biomass (R2 = 0.87 p < 0.0001). No significant differences were found between the dry weight obtained directly and that estimated by the indirect method. Conclusions Our results suggest that leaf length is a good attribute to estimate the aboveground biomass of P. crassipes. This method can contribute to diminish the impact of the direct method of harvest of P. crassipes and can be applied in experimental studies aimed to determine the leaf life span and primary productivity of P. crassipes clones. Abstract hyacinth freefloating free floating America floodplains as nondestructive non destructive destructive. . destructive) Argentina. Argentina (Argentina) ovendried oven dried analysis 27 11 cm R2 R (R 087 0 87 0.8 0.0001. 00001 0.0001 0001 0.0001) P clones (Argentina 2 1 08 8 0. 0000 0.000 000 0.00 00 0.0

Resumen Los estudios de la araneofauna en los agroecosistemas son cruciales para la implementación de las arañas como agentes potenciales de control biológico de plagas. En este trabajo se analiza la distribución del ensamble de arañas en los microhábitats (follaje, tronco y suelo) de los cultivos de Citrus sinensis, (Rutaceae) de la Provincia de Corrientes, Argentina. Los muestreos se realizaron mensualmente mediante cuatro técnicas de captura: agitación de follaje, tamizado de hojarasca, pitfall y captura manual. En total se obtuvieron 2 160 muestras y 7 194 ejemplares de arañas (2 462 en follaje, 983 en tallo y 3 749 en suelo) pertenecientes a 35 familias y 200 especies de Araneomorphae. Hubo diferencias significativas en la estructura de las comunidades de arañas de los tres microhábitats y entre los meses, según el análisis de similitud (ANOSIM). El follaje presentó mayor diversidad, seguido por el suelo y el tronco. Araneidae, Theridiidae y Salticidae predominaron en el follaje; las especies dominantes fueron: Jessica erythostoma y Cheiracantium inclusum, esta araña es una de las principales depredadoras de las larvas de Phyllocnistis citrella (Lepidoptera) que atacan las hojas de Citrus. En el tronco abundaron: Tetragnathidae, Hersiliidae y Theridiidae, destacándose Iviraiva pachyura, una especie especialista en dicho microhabitat; y Leucauge venusta la cual consideramos que es una especie oportunista, debido a que su abundancia se incrementa notablemente en sitios modificados por el hombre. En el suelo abundaron: Lycosidae, Linyphiidae y Coriniidae; Lycosa erythrognatha fue la especie dominante, seguida de Pardosa plumipedata. El índice de similitud Chao-Jaccard fue mayor entre el follaje y el tronco (J-C = 0.95), asimismo el ordenamiento Escalado Multidimencional no Métrico (NMDS) mostró una clara diferenciación de la composición de especies del suelo con respecto al follaje y al tronco. Además, en el suelo hubo mayor recambio temporal de especies y el método de seriación resultó significativo (z = 3.82, P = 0 .00) por lo tanto hubo una sucesión de especies durante el año de muestreo. Las especies en cada microhabitat probablemente evitan la competencia al utilizar distintas estrategias de caza y recursos ecológicos, además de patrones específicos de distribución temporal. Nuestros resultados sugieren que las modificaciones del ambiente, como en estos cultivos de C. sinensis, tienden a albergar varias poblaciones de arañas que se adaptaron a dicho cambio e interactúan de manera equilibrada en espacio y tiempo.

Abstract Arachnofauna studies from agroecosystems are crucial for implements spider as biological control agents. In this work we analyze the distribution of spider assemblages at three microhabitats (canopy, tree trunk and soil) in Citrus sinensis orchards (Rutaceae) in the Province of Corrientes, Argentina. Spiders were collected monthly using four sampling techniques: beating foliage, leaf litter sifting, pitfall traps and direct capture by hand. A total of 2 160 samples were examined and 7 194 spiders were collected (2 462 on the canopy, 983 on trunk and 3 749 on the floor) belonging to 34 families and 200 species/ morphospecies of Araneomorphae. There were significant differences among microhabitats and months in the structure of the spider communities, according to analysis of similarity (ANOSIM). The diversity was highest on the canopy, followed by soil and tree trunk. Araneidae, Salticidae and Anyphaenidae were the most abundant taxa in the canopy; the dominant species were Jessica erythostoma and Cheiracanthium inclusum, a predator of the leaf herbivore Phyllocnistis citrella (Lepidoptera) a pest of Citrus spp. The most abundant families on the tree trunk were Tetragnathidae, Hersiliidae and Theridiidae, Iviraiva pachyura was a species specialist in such microhabitat; and Leucauge venusta was an opportunistic species, because their abundance increaseds markedly in anthropic environments that modified by man. The most abundant families on the floor were Lycosidae, Linyphiidae and Coriniidae. In this habitat, Lycosa erythrognatha and Pardosa plumipedata were dominant species. The Chao-Jaccard similarity index was highest between the canopy and trunk (J-C = 0.95), likewise ordination by nonmetric multidimensional scaling (NMDS) revealed strong differentiation between assemblages of soil spiders and canopy and trunk spiders. Also, on the soil the temporary replacement of species was greater and the seriation method was significant (z = 3.82, P = 0.00) therefore there was a succession of species during the year. The different species in each microhabitat probably avoided competition by using different hunting strategies and different ecological resources, in addition to specific patterns of temporal distribution. Our results suggest that anthropic environments, such as in Citrus orchards, tend to harbor populations of spiders able to adapt to those environments and interact in a balanced way in space and time.

This paper analyzes the academic performance of students entering the School of Natural Sciences and Surveying, National University of the Northeast (FACENA-UNNE, its Spanish acronym) in Corrientes, Argentina, during their first year, in relation to their socio-educational characteristics. Performance was measured by whether or not they passed the partial or final exams of the first mathematics course that students take. A binary logistic regression model was adjusted, which properly classified 75% of the data. Among the most important variables for explaining academic performance is obtaining the high school diploma, the major chosen, and the educational level attained by the student's mother.

En este trabajo se analiza la relación del rendimiento académico de los alumnos ingresantes a la Facultad de Ciencias Exactas y Naturales y Agrimensura de la Universidad Nacional del Nordeste (FACENA-UNNE) en Corrientes, Argentina, durante el primer año de carrera con las características socioeducativas de los mismos. El rendimiento fue medido por la aprobación de los exámenes parciales o finales de la primera materia de Matemática que los alumnos cursan. Se ajustó un modelo de regresión logística binaria, el cual clasificó adecuadamente el 75% de los datos. Entre las variables más relevantes para explicar el rendimiento académico se encuentran el título secundario obtenido, la carrera elegida y el nivel educacional alcanzado por la madre.

Se da a conocer la diversidad de isópteros en tres pastizales del nordeste de la provincia de Corrientes, sometidos a manejo ganadero (potreros de pastoreo) de variada intensidad. Se utilizó el protocolo rápido de estimación de la diversidad de isópteros, consistente en el trazado de transectos. En cada transecto, los porcentajes de secciones donde se hallaron termitas variaron entre el 75% y el 90%. Se recolectaron en total 74 muestras de termitas, correspondieron a diez especies de isópteros, todas pertenecientes a la familia Termitidae (subfamilias Nasutitermitinae, Termitinae y Apicotermitinae). Las especies que se detectaron con mayor frecuencia fueron Cornitermes cumulans y Anoplotermes sp. 1. Sólo dos especies ( Neocapritermes opacus y Grigiotermes sp . 1) resultaron comunes a los tres sitios. La riqueza específica resultó similar entre dos de los predios, con siete especies presentes, en tanto que en el tercer pastizal este valor fue de cinco especies. Los microhábitats más frecuentemente colonizados por termitas fueron los nidos epígeos, el suelo entre raíces de vegetación y el suelo superficial. Predominaron las especies alimentadoras de suelo (70%), representadas en su mayoría por la subfamilia Apicotermitinae. No se evidenciaron influencias notables de las alteraciones causadas por la actividad ganadera y por el tipo de manejo sobre la termitofauna de los predios analizados .

The isopteran diversity was studied in three pastures from the northeast of the province Corrientes under intensive grazing management (grazing paddocks). A protocol for the rapid assessment of termite diversity was used, consisting of transect sampling. In each transect, the percentage of sections where termites were detected varied between 75 and 90%. A total of 74 termite samples was collected, all belonging to the family Termitidae (subfamilies Nasutitermitinae, Termitinae, and Apicotermitinae). The species most frequently collected were Cornitermes cumulans and Anoplotermes sp. 1. Only two species ( Neocapritermes opacus and Grigiotermes sp . 1) were common to the three sites. The species richness was similar between two of the habitats, with seven species present, while the value was five species in the third pasture. The microhabitats most frequently colonized by termites were epigeal nests, soil between plant roots and surface soil. The soil- feeding termites (70%) dominated the termite assemblage, represented mainly by the subfamily Apicotermitinae. There was no notable influence of the perturbations caused by grazing activity or the type of management on the termite fauna of the analyzed sites .