Comunidades vegetales de los bofedales de la Cordillera Real (Bolivia) bajo el calentamiento global

Los humedales altoandinos (bofedales) son uno de los más amenazados frente al calentamiento global. Dada la estrecha relación entre bofedales y agua, el retroceso glacial podrá causar su contracción. Con tres proxis del cambio climático (área de bofedales, influencia glaciar y altitud) se infirió indirectamente cómo éstos pueden afectar a las comunidades vegetales. Las hipótesis fueron 1) que la reducción del área del bofedal podría afectar negativamente la diversidad de plantas - la influencia glaciar y la altitud podrían afectar ésta relación por su efectos en la heterogeneidad ambiental y la diversidad – y 2) que el retroceso glacial puede afectar indirectamente la diversidad a través de cambios en las especies dominantes. Se midió la diversidad α y β aditiva de plantas en 20 bofedales (>4.400 m) de la Cordillera Real (Bolivia). Se encontraron 63 especies (riqueza especifica: 5-22/cuadrante 1m²). Variaciones del área e influencia glacial no se relacionaron con cambios en la vegetación, pero la diversidad fue menor a mayor altitud. Las hojas de Oxychloe andina son más resistentes al estrés ambiental por su mayor masa foliar seca, a diferencia de Distichia spp., indicando que los bofedales dominados por O. andina son más secos. Además tienen más especies que también se pueden encontrar en las laderas. Mientras, las comunidades de Distichia spp. son menos tolerantes al déficit hídrico. Si el retroceso glacial reducirá el agua en las próximas décadas, el bofedal de O. andina podrá ser más abundante a expensas de los de Distichia spp., generando desafíos para la conservación. Oxychloe andina , Retroceso glacial

Compositional shifts of alpine plant communities across the high Andes.

Aim: Climate change is transforming mountain summit plant communities worldwide, but we know little about such changes in the High Andes. Understanding large-scale patterns of vegetation changes across the Andes, and the factors driving these changes, is fundamental to predicting the effects of global warming. We assessed trends in vegetation cover, species richness (SR) and community-level thermal niches (CTN) and tested whether they are explained by summits' climatic conditions and soil temperature trends. Location: High Andes. Time period: Between 2011/2012 and 2017/2019. Major taxa studied: Vascular plants. Methods: Using permanent vegetation plots placed on 45 mountain summits and soil temperature loggers situated along a ~6800 km N-S gradient, we measured species and their relative percentage cover and estimated CTN in two surveys (intervals between 5 and 8 years). We then estimated the annual rate of changes for the three variables and used generalized linear models to assess their relationship with annual precipitation, the minimum air temperatures of each summit and rates of change in the locally recorded soil temperatures. Results: Over time, there was an average loss of vegetation cover (mean = −0.26%/ yr), and a gain in SR across summits (mean = 0.38 species m2/yr), but most summits had significant increases in SR and vegetation cover. Changes in SR were positively related to minimum air temperature and soil temperature rate of change. Most plant communities experienced shifts in their composition by including greater abundances of species with broader thermal niches and higher optima. However, the measured changes in soil temperature did not explain the observed changes in CTN. Main conclusions: High Andean vegetation is changing in cover and SR and is shifting towards species with wider thermal niche breadths. The weak relationship with soil temperature trends could have resulted from the short study period that only marginally captures changes in vegetation through time.EEA Santa CruzFil: Cuesta, F. Universidad de las Américas. Grupo de Investigación en Biodiversidad Medio Ambiente y Salud – BIOMAS; Ecuador.Fil: Carilla, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Carilla, Julieta. Universidad Nacional de Tucumán. Instituto de Ecología Regional; Argentina.Fil: Llambí, L.D. Universidad de Los Andes. Instituto de Ciencias Ambientales y Ecológicas; Venezuela.Fil: Llambí, L.D. Consorcio para el Desarrollo Sostenible de la Ecorregión Andina (CONDESAN); Perú.Fil: Muriel, P. Pontificia Universidad Católica del Ecuador. Escuela de Ciencias Biológicas Laboratorio de Ecofisiología; Ecuador.Fil: Lencinas, María Vanessa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas (CADIC); Argentina.Fil: Meneses, R. I. Universidad Católica del Norte. Instituto de Investigaciones Arqueológicas y Museo; Chile.Fil: Feeley, K. J. University of Miami. Biology Department. Coral Gables; Estados UnidosFil: Pauli, H. Austrian Academy of Sciences. Institute for Interdisciplinary Mountain Research; Austria.Fil: Pauli, H. University of Natural Resources and Life Sciences. Department of Integrative Biology and Biodiversity Research; Austria.Fil: Aguirre, N. Universidad Nacional de Loja. Carrera de Ingeniería Forestal. Centro de Investigaciones Tropicales del Ambiente y Biodiversidad (CITAB); Ecuador.Fil: Beck, S. Museo Nacional de Historia Natural - Instituto de Ecología (UMSA). Herbario Nacional de Bolivia; Bolivia.Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina.Fil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina.Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Tovar, C. Royal Botanical Gardens Kew. Jodrell Laboratory; Reino Unid

Effects of grazing pressure on plant species composition and water presence on bofedales in the Andes mountain range of Bolivia

Bofedales are high-Andean peatland plant communities with high capacity for water retention, which are regarded as oases of biodiversity. These areas have great social and economic value for livestock grazing, which plays an important role in their vegetation dynamics. However, the effects of increased livestock pressure on vegetation composition and surface water have not yet been clarified. The goal of this study was to assess the impact of current grazing practices on bofedal vegetation, species diversity and function. Specifically, the study aimed to (1) quantify carrying capacity and stocking rate in grazed bofedales and (2) quantify the effects of grazing pressure on plant composition and the extents of bare soil and surface water. Biomass and stocking rate estimates for 25 bofedales along the Cordillera Real (Tropical Andes, Bolivia) showed that all bofedales were overgrazed (carrying capacity/stocking rate (CC/SR) <1). Regression analyses showed significant decreases in number of plant species, species dominance, diversity and percent surface water as CC/SR declined (p < 0.05). Bofedales are negatively affected by increased grazing pressure and potentially affected by changes in livestock species. These pressures, combined with land use changes and climate change, could result in long-term negative effects for the ecological functioning and sustainability of bofedales

Role of age and comorbidities in mortality of patients with infective endocarditis

Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Phylogenomics and the rise of the angiosperms

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Métodos para estudiar el efecto del cambio climático sobre los bofedales y sus servicios ambientales inherentes

A pesar que las montañas tropicales son uno de los biomas más amenazados del mundo, es escasa la investigación fundamental y aplicada sobre los efectos de los cambios globales en la biodiversidad y los beneficios de los ecosistemas. Las zonas húmedas de los ambientes altoandinos tropicales - los bofedales - son espacios verdes dentro de una matriz árida que concentran una rica biodiversidad y variedad de beneficios asociados (almacenamiento de carbono, regulación de agua y producción de ganado), de los que dependen millones de personas. Estos frágiles ecosistemas están amenazados por la rapidez del derretimiento de los glaciares de los cuales dependen significativamente. El proyecto BIOTHAW - Biodiversidad e interacciones de uso de los suelos frente a la evolución de la disponibilidad de agua de los glaciares en las zonas húmedas de los Andes tropicales - tiene por objetivo desarrollar un marco de modelización para establecer escenarios de biodiversidad y uso de las tierras en un contexto de cambios globales. El enfoque del proyecto integra tres componentes: 1) la modificación de los aportes de agua glaciares a las zonas húmedas, 2) la biodiversidad (animal y vegetal) de estas zonas y 3) las prácticas de cultivo (patrones de utilización de las tierras, dinámica de las estructuras de la ganadería). Nutridos por escenarios climáticos y socioeconómicos, los diferentes modelos combinados con mapas de distribución de las zonas húmedas permitirán establecer escenarios de la biodiversidad y los servicios de los bofedales, con el fin de definir zonas prioritarias de conservación. (résumé d'auteur

Comunidades vegetales de los bofedales de la Cordillera Real (Bolivia) bajo el calentamiento global

International audienceHigh-Andean wetlands (bofedales) are one of the most threatened ecosystems in the face of global warming. Given the close relationship between bofedales and water, it is expected that glacial retreat will cause their gradual shrinkage. With three proxies of climate change (bofedal area, glacier influence and elevation) we inferred how these changes may affect plant communities. The hypotheses were 1) that loss in the area of bofedales should reduce plant diversity - the glacier influence and elevation could affect this relationship through effect on environmental heterogeneity and diversity - and 2) glacial retreat may indirectly affect diversity through changes in dominant species. We measured ? and ? additive diversity of plants in 20 bofedales (>4.400 m) in the Cordillera Real (Bolivia). Sixty three species were found (species richness: 5-22 /plot 1 m2). Variations in bofedales área and glacial influence weren't correlated with vegetation changes whereas diversity reduced at higher elevation. In reference to our second hypothesis, leaves of Oxychloe andina were shown more resistant to drought stress because of its higher leaf dry mass content (LDMC) than the other cushions, indicating that the bofedales dominated by O. andina may be drier and the communities are dominated by species that also can be found in drier environments. In contrast, communities of Distichia spp. are less tolerant to water déficit. If glacial retreat reduces water availability in the coming decades, the bofedales of O. andina may be more abundant at the expense of Distichia spp. creating challenges for the biodiversity conservationLos humedales altoandinos (bofedales) son uno de los más amenazados frente al calentamiento global. Dada la estrecha relación entre bofedales y agua, el retroceso glacial podrá causar su contracción. Con tres proxis del cambio climático (área de bofedales, influencia glaciar y altitud) se infirió indirectamente cómo éstos pueden afectar a las comunidades vegetales. Las hipótesis fueron 1) que la reducción del área del bofedal podría afectar negativamente la diversidad de plantas - la influencia glaciar y la altitud podrían afectar ésta relación por su efectos en la heterogeneidad ambiental y la diversidad – y 2) que el retroceso glacial puede afectar indirectamente la diversidad a través de cambios en las especies dominantes. Se midió la diversidad α y β aditiva de plantas en 20 bofedales (>4.400 m) de la Cordillera Real (Bolivia). Se encontraron 63 especies (riqueza especifica: 5-22/cuadrante 1m²). Variaciones del área e influencia glacial no se relacionaron con cambios en la vegetación, pero la diversidad fue menor a mayor altitud. Las hojas de Oxychloe andina son más resistentes al estrés ambiental por su mayor masa foliar seca, a diferencia de Distichia spp., indicando que los bofedales dominados por O. andina son más secos. Además tienen más especies que también se pueden encontrar en las laderas. Mientras, las comunidades de Distichia spp. son menos tolerantes al déficit hídrico. Si el retroceso glacial reducirá el agua en las próximas décadas, el bofedal de O. andina podrá ser más abundante a expensas de los de Distichia spp., generando desafíos para la conservación. Oxychloe andina , Retroceso glacial