Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

Does soil pyrogenic carbon determine plant functional traits in Amazon Basin forests?

Amazon forests are fire-sensitive ecosystems and consequently fires affect forest structure and composition. For instance, the legacy of past fire regimes may persist through some species and traits that are found due to past fires. In this study, we tested for relationships between functional traits that are classically presented as the main components of plant ecological strategies and environmental filters related to climate and historical fires among permanent mature forest plots across the range of local and regional environmental gradients that occur in Amazonia. We used percentage surface soil pyrogenic carbon (PyC), a recalcitrant form of carbon that can persist for millennia in soils, as a novel indicator of historical fire in old-growth forests. Five out of the nine functional traits evaluated across all 378 species were correlated with some environmental variables. Although there is more PyC in Amazonian soils than previously reported, the percentage soil PyC indicated no detectable legacy effect of past fires on contemporary functional composition. More species with dry diaspores were found in drier and hotter environments. We also found higher wood density in trees from higher temperature sites. If Amazon forest past burnings were local and without distinguishable attributes of a widespread fire regime, then impacts on biodiversity would have been small and heterogeneous. Alternatively, sufficient time may have passed since the last fire to allow for species replacement. Regardless, as we failed to detect any impact of past fire on present forest functional composition, if our plots are representative then it suggests that mature Amazon forests lack a compositional legacy of past fire

Síndrome de Cogan: apresentação de caso e diagnóstico diferencial Differential diagnosis between Cogan's syndrome

A síndrome de Cogan é uma doença de difícil diagnóstico pois não apresenta nenhum marcador laboratorial específico, assim como a neuronite vestibular. As características clínicas da síndrome de Cogan são: ceratite intersticial não-luética associada à vertigem, tinnitus e disacusia neurossensorial. Evidências de vasculite sistêmica são encontradas em 50% dos pacientes. As formas atípicas da síndrome de Cogan abrangem doenças oculares inflamatórias mais severas. As características clínicas da Neuronite Vestibular são: vertigem incapacitante de aparecimento abrupto e não responsiva ao tratamento clínico, sem associação com alterações cocleares. Exemplificamos essa dificuldade diagnóstica com o caso de um paciente que iniciou quadro de vertigem súbita incapacitante associada à febre e algia ocular unilateral. O paciente foi hospitalizado, sendo iniciada a terapêutica para síndrome vestibular, não respondendo à medicação. Após uma semana, evoluiu com lesão ocular caracterizada por esclerouveíte anterior. Com quinze dias de evolução o paciente apresentou quadro de disacusia neurossensorial rapidamente progressiva. O exame vestibular evidenciou arreflexia à esquerda, ipsilateral à disacusia neurossensorial. A ressonância magnética evidenciou sinais de microvasculite em sistema nervoso central sendo diagnosticada a síndrome de Cogan. Foi iniciada terapia com corticóide oral e pulsoterapia com ciclofosfamida, havendo melhora total da vertigem, do desequilíbrio e da alteração ocular e com melhora parcial da disacusia.<br>Cogan's syndrome is a disease of difficult diagnosis as there is no specific laboratorial exam and the same occurs with Vestibular Neurinitis. The clinical features of Cogan's syndrome are nonsyphilitic interstitial keratitis and vestibuloauditory dysfunction. Evidences of systemic vasculitis are found in 50% of the patients. The atypical forms of Cogan's syndrome array more severe inflammatory ocular disease. The clinical features of the Vestibular Neuronitis are acute episodes of vertigo that doesn't respond to clinical treatment. We exemplify these diagnostical difficulties with the case study of a patient who initiated a state of acute episodes of vertigo associated with fever and unilateral ocular pain. The patient was hospitalized, and initiated therapy for vestibular symptoms, not responding to medications. A week later, the patient evoluted to an ocular disease characterized by anterior sclerouveitis. With fifteen days of evolution, the patient presented a state of rapidly progressive hearing loss. The otoneurological exam showed unilateral diminished caloric response. Magnetic resonance imaging showed signs of microvasculitis in the central nervous system, being diagnosed Cogan's syndrome. Therapy was initiated with oral prednisone and cyclophosphamide, with total improvement of vertigo, dizziness and eye symptoms and partial improvement of sensorineural hearing loss