Efecto de los gradientes de pastoreo ovino sobre la vegetación y el suelo en Península Valdés, Patagonia Argentina

La introducción de ganado doméstico provocó modificaciones en la vegetación y en el suelo de la Patagonia extra-andina. Estos cambios alteraron procesos ecosistémicos, aumentaron la desertificación y causaron pérdida de biodiversidad. Es frecuente encontrar gradientes decrecientes de actividad animal partiendo de las aguadas (piósferas), que resultan adecuados para determinar el impacto del pastoreo sobre los ecosistemas. El objetivo de este estudio fue evaluar el efecto de la intensidad de pastoreo ovino a partir de gradientes de piósfera sobre la estructura de la vegetación y el suelo en estepas arbustivas representativas de Península Valdés, Argentina. Mediante modelos lineales generalizados mixtos (GLMM) y técnicas multivariadas se estudiaron las variaciones en la cobertura vegetal, complejidad vertical de la vegetación, número y área de parches vegetados, microtopografía del suelo y su compactación en relación con el gradiente de pastoreo. La intensidad del pastoreo disminuyó con la distancia a la aguada y explicó más de 50% de la variabilidad ambiental. Esto demuestra la existencia de efecto piósfera. La cobertura de herbáceas, mantillo, complejidad vertical de la vegetación y la microtopografía aumentaron al disminuir la presión de pastoreo en los sitios más alejados de la aguada, mientras que el porcentaje de suelo desnudo, gravas, cobertura de anuales y la compactación del suelo presentaron un patrón opuesto. Este estudio evidencia, por primera vez, la existencia de piósferas ovinas en Península Valdés e indica que la intensidad de pastoreo en la región se asocia con alteraciones ambientales compatibles con procesos importantes de degradación ecosistémica. Dada la importancia que reviste la península en el contexto de la conservación biológica de la región, se requieren más estudios de este tipo para una implementación efectiva de medidas de manejo que integren la ganadería y la conservación de los recursos naturales.The introduction of domestic livestock in the arid Patagonia produced changes in vegetation and soil that altered fundamental ecosystem processes, increasing desertification and biodiversity loss. In this region, it is common to observe gradients of decreasing animal activity from watering points where livestock impact is greatest near the watering sites, called piospheres, particularly suitable for assessing the effect of grazing on arid ecosystems. The aim of this study was to evaluate the effect of sheep-grazing intensity using piospheres on the structure of the vegetation and soil in shrubby steppes of Peninsula Valdes, Argentina. Variation of plant cover, vertical complexity of the vegetation, number and area of vegetated patches, micro-topography and soil compaction in relation to piosphere gradients were studied using Generalized Linear Mixed Models (GLMM) and multivariate analyses. Grazing intensity decreased according to increasing distance to the watering point. This fact, explaining more than 50% of the overall environmental variability, confirmed the existence of a piosphere gradient on each studied site. Such environmental changes were characterized by a gradual increase in grass and litter cover, vertical complexity of vegetation and soil microtopography at increasing distances from the watering point. Percentages of bare soil and gravel, cover of annual grasses and soil compaction showed the opposite pattern. This study demonstrates, for the first time, the existence of sheep piospheres in the shrubby steppes of Peninsula Valdes. Our results indicate that sheep-grazing intensity is associated with changes in the structure and composition of the vegetation and the soil characteristics that are compatible with degradation processes in the study region. Taking into account the importance of Peninsula Valdes in the context of biodiversity conservation, more studies of this type are required to implement effective management actions integrating livestock and conservation efforts on the terrestrial ecosystems of the regionFil: Cheli, Germán H. CCT-CONICE-CENPAT. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia San Juan Bosco. Facultad de Ciencias Naturales; ArgentinaFil: Pazos, Gustavo E. CCT-CONICE-CENPAT. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia San Juan Bosco. Facultad de Ciencias Naturales; ArgentinaFil: Flores, Gustavo E. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Argentino de Investigaciones de las Zonas Áridas. Laboratorio de Entomología; ArgentinaFil: Corley, Juan Carlos. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Grupo de Ecología de Poblaciones de Insectos; Argentin

The Ground-Dwelling Arthropod Community of Península Valdés in Patagonia, Argentina

This is the first study based on a planned and intensive sampling effort that describes the community composition and structure of the ground-dwelling arthropod assemblage of Península Valdés (Patagonia). It was carried out using pitfall traps, opened for two weeks during the summers of 2005, 2006 and 2007. A total of 28, 111 individuals were caught. Ants (Hymenoptera: Formicidae) dominated this community, followed by beetles (Coleoptera) and spiders (Araneae). The most abundant species were Pheidole bergi Mayr (Hymenoptera: Formicidae) and Blapstinus punctulatus Solier (Coleoptera: Tenebrionidae). Two new species were very recently described as new based on specimens collected during this study: Valdesiana curiosa Carpintero, Dellapé & Cheli (Hemiptera, Miridae) and Anomaloptera patagonica Dellapé & Cheli (Hemiptera, Oxycarenidae). The order Coleoptera was the most diverse taxa. The distribution of abundance data was best described by the logarithmic series model both at the family and species levels, suggesting that ecological relationships in this community could be controlled by a few factors. The community was dominated by predators from a trophic perspective. This suggests that predation acts as an important factor driving the distribution and abundances of surface-dwelling arthropods in this habitat and as such serves as a key element in understanding desert, above-ground community structure. These findings may also be useful for management and conservation purposes in arid Patagonia

The Ground-Dwelling Arthropod Community of Península Valdés in Patagonia, Argentina

This is the first study based on a planned and intensive sampling effort that describes the community composition and structure of the ground-dwelling arthropod assemblage of Península Valdés (Patagonia). It was carried out using pitfall traps, opened for two weeks during the summers of 2005, 2006 and 2007. A total of 28, 111 individuals were caught. Ants (Hymenoptera: Formicidae) dominated this community, followed by beetles (Coleoptera) and spiders (Araneae). The most abundant species were Pheidole bergi Mayr (Hymenoptera: Formicidae) and Blapstinus punctulatus Solier (Coleoptera: Tenebrionidae). Two new species were very recently described as new based on specimens collected during this study: Valdesiana curiosa Carpintero, Dellapé & Cheli (Hemiptera, Miridae) and Anomaloptera patagonica Dellapé & Cheli (Hemiptera, Oxycarenidae). The order Coleoptera was the most diverse taxa. The distribution of abundance data was best described by the logarithmic series model both at the family and species levels, suggesting that ecological relationships in this community could be controlled by a few factors. The community was dominated by predators from a trophic perspective. This suggests that predation acts as an important factor driving the distribution and abundances of surface-dwelling arthropods in this habitat and as such serves as a key element in understanding desert, above-ground community structure. These findings may also be useful for management and conservation purposes in arid Patagonia

Effi cient Sampling of Ground-Dwelling Arthropods Using Pitfall Traps in Arid Steppes

ABSTRACT -Pitfall trapping is probably the most frequently used method for sampling grounddwelling arthropods. While the capture of specimens in pitfall traps largely depends on the number of individuals in the sampled area, trap design and trapping effort for a given environment, can also affect sampling success. The aim of this study was to determine the best pitfall trapping design for collecting ground-dwelling arthropods in the wind-blown and cold arid steppe areas of Patagonia. We tested four designs of traps, six types of preservative and different times of activation as well as the quantity of traps. Both preservation attributes and sampling effi ciency differed between different trap designs and fl uids compared. We conclude that in order to obtain reliable data on the structure of a community of ground-dwelling arthropods in Patagonia, at least three pitfall traps per experimental unit are required. In addition, traps should be opened for a minimum of 10 days fi lled with 300 ml of 30% ethylene glycol. We also suggested the use of a simple trap design (i.e. without funnel or roof). We believe these fi ndings will contribute to more appropriate sampling of the ground dwelling fauna of Patagonia as well as other arid areas, leading to more reliable diversity studies

from Argentinean Patagonia with zoogeographical and ecological remarks

www.mapress.com/zootaxa

Patrones biogeográficos de los tenebriónidos epigeos (Coleoptera: Tenebrionidae) del Área Natural Protegida Península Valdés, Argentina: implicaciones para su conservación Biogeographic patterns of epigean tenebrionids (Coleoptera: Tenebrionidae) from Protected Natural Area Península Valdés, Argentina: implications for its conservation

Se realizó un estudio sobre los patrones biogeográficos de los tenebriónidos epigeos (Coleoptera: Tenebrionidae) que habitan el Área Natural Protegida Península Valdés (Chubut, Argentina), basado en datos de colecciones y material recolectado en viajes a la zona. Se presenta una lista exhaustiva de las especies en la que se consigna el grado de adaptación a la aridez de cada una de ellas; un análisis de la calidad del inventario y la estimación de la riqueza total de especies; una evaluación de los patrones de distribución y riqueza, y la identificación de áreas de significativa mayor riqueza o hotspots. Los resultados indicaron que 25 especies con diferente grado de adaptación a la aridez habitan la península, aunque se estima que la riqueza total del área debería ser de 27. Además, se reconoció que los rangos de distribución de los tenebriónidos siguen una distribución log-normal y que sólo 3 especies son endémicas. Espacialmente, la riqueza se distribuyó de forma agregada en la península y se determinaron 10 hotspots. Finalmente, considerando que en la península Valdés están permitidas actividades productivas que originan una importante degradación del hábitat, se examina la implicancia de los resultados para la conservación de los tenebriónidos epigeos.<br>We conducted a study of the biogeographic patterns of epigean tenebrionids (Coleoptera: Tenebrionidae) that inhabit the Protected Natural Area Península Valdés (Chubut, Argentina), based on data obtained from collections and collecting trips. We present a comprehensive species list, where we detail the degree of adaptation to aridity shown by each species, an analysis of the quality of the inventory, an estimation of total species richness, and an evaluation of distribution and richness patterns, with the identification of areas of significantly greater richness or "hotspots". The results indicated that 25 species with different degrees of adaptation to aridity inhabit the peninsula, although it was estimated that the total richness of the area should be 27 species. In addition, it was recognized that the species range sizes follow a log-normal distribution and that only three species are endemic. The spatial distribution of richness was aggregate within the peninsula and we can identify 10 "hotspots". Finally, considering that in the Península Valdés are allowed productive activities that cause significant habitat degradation, we discuss the implicances that have these findings for epigean tenebrionids conservation