General statistical scaling laws for stability in ecological systems

Ecological stability refers to a family of concepts used to describe how systems of interacting species vary through time and respond to disturbances. Because observed ecological stability depends on sampling scales and environmental context, it is notoriously difficult to compare measurements across sites and systems. Here, we apply stochastic dynamical systems theory to derive general statistical scaling relationships across time, space, and ecological level of organisation for three fundamental stability aspects: resilience, resistance, and invariance. These relationships can be calibrated using random or representative samples measured at individual scales, and projected to predict average stability at other scales across a wide range of contexts. Moreover deviations between observed vs. extrapolated scaling relationships can reveal information about unobserved heterogeneity across time, space, or species. We anticipate that these methods will be useful for cross-study synthesis of stability data, extrapolating measurements to unobserved scales, and identifying underlying causes and consequences of heterogeneity

Recuperação de campos nativos suprimidos no Bioma Pampa: um estudo de caso em escala de paisagem em Rosário do Sul (RS).

Uma parceria entre Exército Brasileiro, Ibama, Embrapa Pecuária Sul, Unipampa e UFRGS conduziu um Projeto de Recuperação de Área Degradada (Prad) no Campo de Instrução Barão de São Borja, em Rosário do Sul/RS, visando recuperar campos nativos com histórico de uso com lavouras de arroz e soja. A hipótese central trabalhada no Prad é de que o pastejo pode ser um instrumento para restaurar as formações campestres, impedindo que a vegetação evolua para uma fisionomia arbustiva e acelerando a regeneração natural. O gado bovino foi usado como ?roçadeira biológica? e dispersor de sementes, prática complementada por roçadas mecânicas, nivelamento do solo e isolamento temporário da área em recuperação. O monitoramento da estrutura e da riqueza da vegetação norteou o ajuste de carga animal e os períodos de diferimento. Passados cinco anos, a área apresenta fisionomia campestre desejada, tendo sido observado aumento na riqueza de espécies nativas, e composição botânica com maior similaridade à da área de referência, com aumento na cobertura de espécies das famílias Poaceae e Fabaceae. Houve diminuição do solo exposto, com o aumento da cobertura vegetal, e registrado o aumento da cobertura de Eragrostis plana (capim-annoni), gramínea exótica invasora

Character and environmental lability of cyanobacteria-derived dissolved organic matter

Autotrophic dissolved organic matter (DOM) is central to the carbon biogeochemistry of aquatic systems, and the full complexity of autotrophic DOM has not been extensively studied, particularly by high-resolution mass spectrometry (HRMS). Terrestrial DOM tends to dominate HRMS studies in freshwaters due to the propensity of such compounds to ionize by negative mode electrospray, and possibly also because ionizable DOM produced by autotrophy is decreased to low steady-state concentrations by heterotrophic bacteria. In this study, we investigated the character of DOM produced by the widespread cyanobacteriaMicrocystis aeruginosausing high-pressure liquid chromatography-electrospray ionization-high-resolution mass spectrometry.M. aeruginosaproduced thousands of detectable compounds in axenic culture. These compounds were chromatographically resolved and the majority were assigned to aliphatic formulas with a broad polarity range. We found that the DOM produced byM. aeruginosawas highly susceptible to removal by heterotrophic freshwater bacteria, supporting the hypothesis that this autotroph-derived organic material is highly labile and accordingly only seen at low concentrations in natural settings

Transanal endoscopic microsurgery versus endoscopic mucosal resection for large rectal adenomas (TREND-study)

Background: Recent non-randomized studies suggest that extended endoscopic mucosal resection (EMR) is equally effective in removing large rectal adenomas as transanal endoscopic microsurgery (TEM). If equally effective, EMR might be a more cost-effective approach as this strategy does not require expensive equipment, general anesthesia and hospital admission. Furthermore, EMR appears to be associated with fewer complications. The aim of this study is to compare the cost-effectiveness and cost-utility of TEM and EMR for the resection of large rectal adenomas. Methods/design. Multicenter randomized trial among 15 hospitals in the Netherlands. Patients with a rectal adenoma 3 cm, located between 115 cm ab ano, will be randomized to a TEM- or EMR-treatment strategy. For TEM, patients will be treated under general anesthesia, adenomas will be dissected en-bloc by a full-thickness excision, and patients will be admitted to the hospital. For EMR, no or conscious sedation is used, lesions will be resected through the submucosal plane i