Evaluación de tratamientos pregerminativos en seis especies nativas del ecotono Monte-Espinal del noreste de la Patagonia

El cultivo de plantas nativas es una herramienta para promover la conservación de la biodiversidad y aumentar la valoración pública de los ecosistemas naturales. El objetivo del presente trabajo fue generar información sobre la obtención de individuos de especies nativas del Monte y Espinal del noreste de la Patagonia para contribuir con la formación de un Jardín Botánico. Se trabajó con Brachyclados megalanthus, Cyclolepis genistoides, Grindelia brachystephana, Lycium chilense, Melica bonariensis y Senecio subulatus. Se realizaron ensayos en estufa y en tierra en invernáculo, con la aplicación de los siguientes tratamientos: exposición al frío, imbibición en giberelina, escarificado mecánico y semillas sin tratar (control). Se evaluaron el porcentaje de germinación, el tiempo medio de germinación y la supervivencia de las plántulas. No se encontraron diferencias significativas entre tratamientos, por lo que se concluye que estas especies pueden ser producidas masivamente por semillas a bajo costo, con el fin de conservar ex situ la variabilidad genética nativa.Native plant cultivation is a tool to promote biodiversity conservation and to enhance population awareness and interest in natural ecosystems. The objective of this study was to generate information on the obtaining of native species of Monte and Espinal ecoregions in northeast Patagonia to contribute with the creation of a botanical garden. We worked with Brachyclados megalanthus, Cyclolepis genistoides, Grindelia brachystephana, Lycium chilense, Melica bonariensis and Senecio subulatus. The applied treatments were cold shock, gibberellic acid imbibition, mechanical scarification and control (untreated). We performed two essays: one in germination stove and the second in soil in glasshouse conditions. We evaluated germination percentage, mean germination time and survival of seedlings. We did not observe statistically significant differences among treatments, so it is concluded that these species could be produced in masse from seeds at low cost, with the finality of ex situ conservation of native genetic variability.Fil: Peter, Guadalupe. Universidad Nacional de Río Negro. Sede Atlántica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; ArgentinaFil: Leder, Cintia Vanesa. Universidad Nacional de Río Negro. Sede Atlántica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; ArgentinaFil: Calvo, Dianela Alejandra. Universidad Nacional de Río Negro. Sede Atlántica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; ArgentinaFil: Cruz, Anabella Marisel. Universidad Nacional de Río Negro. Sede Atlántica; ArgentinaFil: Torres Robles, Silvia Susana. Universidad Nacional de Río Negro. Sede Atlántica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentin

Seed rain and soil seed bank compensatory roles on Nassella tenuis (Phil.) Barkworth seedling recruitment in ungrazed and grazed sites

In semi-arid lands, vegetation is distributed in shrub patches immersed in a less vegetated interpatch matrix. Grazing affects perennial grass seed bank through a decrease in seed rain and an increase in seed predation and soil compaction. Nevertheless, some species with anchorage mechanisms in their seeds might overcome this, such as Nassella tenuis (Phil.) Barkworth. This is an important species in grazing paddocks because it has an intermediate palatability and its relatively tolerant to grazing. These characteristics allow N. tenuis to increase its abundance in grazed sites. Our objective was to assess how grazing affects the key palatable species from seeds to seedlings: i.e., seed rain, soil seed bank, and seedling recruitment in different microsites along a windward-leeward transect across shrub canopy. We hypothesized that: (1) the negative effects of grazing on N. tenuis fructification are reflected in its seed rain, soil seed bank, and seedling recruitment, especially in interpatches; (2) Nassella tenuis seed rain reduction, soil compaction by cattle in grazed sites, and removal of seeds by wind decrease its soil seed bank, especially in microsites exposed to the predominant wind; and (3) the decrease in N. tenuis soil seed bank and cover increase in annual species in grazed sites have negative effects on its seedling recruitment, especially in microsites exposed to predominant wind. We placed seed traps, collected soil samples, and monitored seedling recruitment in different locations around shrub canopy to address our hypotheses. Also, we established a manipulative experiment in which we sow N. tenuis seeds and followed its recruitment in different microsites. We compared the seed rain, soil seed bank, natural seedling recruitment, and sown seeds recruitment of N. tenuis between grazed and ungrazed sites. We analyzed differences between microsites along a windward-leeward transect across shrubs patches. Seed rain and soil seed bank had the same density in patches and interpatches both in ungrazed and grazed sites. But seed rain was higher, and soil seed bank was lower in ungrazed sites than in grazed sites. Almost all under-canopy microsites showed greater soil seed bank abundance and natural seedling recruitment in ungrazed sites. Sown seeds recruitment was the same between grazed and ungrazed sites, but it showed protective effects of shrubs in leeward microsites under grazed sites. As a conclusion, seed rain and soil seed bank are complementary under grazed sites.Fil: Leder, Cintia Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentina. Universidad Nacional de Río Negro. Sede Atlántica. Centro de Estudios Ambientales desde la Norpatagonia; ArgentinaFil: Calvo, Dianela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentina. Universidad Nacional de Río Negro. Sede Atlántica. Centro de Estudios Ambientales desde la Norpatagonia; ArgentinaFil: Peter, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentina. Universidad Nacional de Río Negro. Sede Atlántica. Centro de Estudios Ambientales desde la Norpatagonia; Argentin

Effects of biological soil crust and water availability on seedlings of three perennial Patagonian species

Biological soil crusts are communities composed of mosses, lichens and cyanobacteria. They cover a large portion of the arid and semiarid regions of the world and play key roles in nutrient cycles and soil erosion diminution. Biological soil crust might affect germination, establishment and growth of vascular plants. In this study we examined the differential response to soil cover and water availability of grasses and shrubs. Our hypothesis was that seed germination and seedling survival are greater in soils with biological soil crust cover because crust have positive effects on vascular plant establishment. We evaluated the effect of biological soil crust cover on seed emergence, survival and seedling growth of Nassella tenuis, Senecio subulatus and Larrea divaricata. The experiment had four treatments combining biological soil crust (C) or bare soil (BS) with drought (D) or soil at field capacity (FC). Seeds of L. divaricata did not germinate and S. subulatus only germinated in BS-FC. Emergence and biomass of seedlings of N. tenuis were higher with C and at FC. There were no differences in seedling survival. Soil cover with biological soil crust and water availability influenced germination and seedling growth and their effects are different according to the species or plant functional groups. Germination of seeds varies with the composition and structure of the biological soil crust and the vascular plants, and the response may change with different species or plant functional groups.Fil: Peter, Guadalupe. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Leder, Cintia Vanesa. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Funk, Flavia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin

Seed rain alteration related to fire and grazing history in a semiarid shrubland

In arid environments, vegetation is distributed in patches. Herbivory and fires promote changes and seed rain plays a key role in the soil seed bank and the colonization of new spaces. This study focuses on the effect of different land use histories on the spatial and temporal seed rain distribution in Patagonia. We placed traps to capture seed rain of perennial grasses, shrubs and annual forage dicots at five sites with different grazing and fire histories. With grazing and fire seed rain diversity is higher than in absence of disturbances. Functional groups seed rain in vegetation patches did not show differences between sites, but at the interpatch level, grazing increased shrub seed and decreased perennial grass seed in the seed rain. Fire decreased the effects of grazing on shrub seed rain, but did not change its effects on perennial grasses. Shrub species showed a minimum abundance in the seed rain in the undisturbed site. Our re- sults suggest that changes described for vegetative attributes are reflected in the seed rain, and this could reinforce the patch-interpatch pattern; fire did not reduce the grazing effects because it decreased the seed rain of the preferred grasses and increased the less preferred ones.Fil: Leder, Cintia Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro. Sede Atlántica; ArgentinaFil: Peter, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro. Sede Atlántica; ArgentinaFil: Funk, Flavia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin

Consequences of anthropogenic disturbances on soil seed bank diversity and nurse shrub effect in a semiarid rangeland

What is the effect of common land use histories on the diversity, richness, spatial distribution and abundance of the soil seed bank (SSB)? Does the effect change between different microsites under shrub canopy? To address these questions we selected seven sites with different grazing and fire histories in the Patagonian Monte desert. We took soil samples in seven microsites at different distances of the trunk along a windward/leeward transect through shrub patches to estimate the SSB of perennial grasses, shrubs and annuals. Shrubs SSB was scarce. The nurse shrub effect on perennial grass SSB was evident at sites with a low disturbance intensity (as sites without continuous grazing), and higher on the leeward side under the shrub canopy. High disturbance intensity (such as permanent grazing) promoted a decrease in perennial grass SSB and an increase in annuals SBB (especially non-native). Land use histories related to fire showed a moderated disturbance response (medium values for both groups). Differences between land use histories varied depending on the windward/leeward microsite from which the SSB was analysed. Our results suggest a nurse effect of the shrub patches on the spatial distribution and abundance of the SSB, but this effect decrease under continuous grazing. Fire seems to have a positive effect on perennial grass SSB. Nevertheless, fire characteristics must be controlled. Moreover, perennial grass SSB was almost depleted under continuous grazing, driving the grazed system towards a vulnerable state; and annual non-native species take advantage of this disturbance and dominate the SSB.Fil: Leder, Cintia Vanesa. Universidad Nacional de Rio Negro. Sede Atlantica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Peter, Guadalupe. Universidad Nacional de Rio Negro. Sede Atlantica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Funk, Flavia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Pelaez, Daniel Valerio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentin

Montículos fitogénicos bajo diferentes presiones de pastoreo en el monte rionegrino

En el noreste rionegrino la vegetación se distribuye en islas dominadas por arbustos que forman montículos fitogénicos. El objetivo de este estudio fue evaluar la variación en el tamaño, la forma y la riqueza específica de las islas bajo diferentes intensidades de pastoreo: alta (IPA), media (IPM) y baja (IPB). Los sitios se ordenaron a través de ACP. Se observó un agrupamiento de las islas de IPA con mayor riqueza específica y mayor tamaño. Las islas con IPB se asociaron con menor tamaño y menor altura del montículo. El pastoreo aumentaría el tamaño de las islas como resultado de la arbustificación del sistema. In the northeastern of Río Negro vegetation is distributed in islands dominated by shrubs, which form phytogenic mounds. The objective was to study variation in size, shape and specific richness under different grazing pressures: high (IPA), medium (IPM) and low (IPB). The sites were ordered with PCA. The islands of the IPA sites were grouped by their greater specific richness and size; IPB islands were associated by their minor size and lower height. Grazing would increase the island size as a result of the system encroachment.Fil: Peter, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional del Comahue. Centro Universidad Región Zona Atlántica; Argentina. Universidad Nacional de Río Negro. Sede Atlántica; ArgentinaFil: Funk, Flavia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Loydi, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Leder, Cintia Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Casalini, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin

The impact of livestock grazing on the spatial pattern of vegetation in north-eastern Patagonia, Argentina

Background: The occurrence of shrub patches, alternating with either bare soil or low herbaceous cover, is a common feature in arid and semi-arid shrublands throughout the world. This patchy pattern of vegetation may result from water limitation, modulated by plant interactions; grazing (offtake and tramping) by livestock may cause further patchiness vegetation structure. Aims: We hypothesised that vegetation patchiness in the semi-arid shrublands of north-eastern Patagonia would be increased by livestock grazing, but not by positive interactions between adult plants of shrubs and grasses. Methods: We compared vegetation cover and pattern at three grazing intensities (exclosure, light and heavy grazing) and measured the growth of a representative shrub and grass in the presence and absence of the other to quantify the role of plant-to-plant interactions and its interaction with grazing for vegetation structure. Results: In the grazing exclosure and in moderately grazed areas, vegetation cover among shrub patches was larger, whereas the top cover of shrubs was lower than in the heavily grazed areas. We did not find any evidence of positive interactions between shrub and grass life forms. Conclusions: Our results were consistent with the hypothesis that livestock grazing increased the formation of patchy vegetation cover in arid and semi-arid shrublandsFil: Funk, Flavia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Peter, Guadalupe. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Leder, Cintia Vanesa. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Loydi, Alejandro. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Kröpfl, Alicia Inés. Universidad Nacional del Comahue. Centro Universidad Región Zona Atlántica; ArgentinaFil: Distel, Roberto Alejandro. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin