Ecosystem resistance in the face of climate change: a case study from the freshwater marshes of the Florida Everglades

Shaped by the hydrology of the Kissimmee-Okeechobee-Everglades watershed, the Florida Everglades is composed of a conglomerate of wetland ecosystems that have varying capacities to sequester and store carbon. Hydrology, which is a product of the region’s precipitation and temperature patterns combined with water management policy, drives community composition and productivity. As shifts in both precipitation and air temperature are expected over the next 100 years as a consequence of climate change, CO2 dynamics in the greater Everglades are expected to change. To reduce uncertainties associated with climate change and to explore how projected changes in atmospheric CO2 concentration and climate can alter current CO2 exchange rates in Everglades freshwater marsh ecosystems, we simulated fluxes of carbon among the atmosphere, vegetation, and soil using the DAYCENT model. We explored the effects of low, moderate, and high scenarios for atmospheric CO2 (550, 850, and 950 ppm), mean annual air temperature (þ1, þ2.5, and þ4.28C) and precipitation (2, þ7, and þ14%), as predicted by the IPCC for the year 2100 for the region, on CO2 exchange rates in short- and long-hydroperiod wetland ecosystems. Under 100 years of current climate and atmospheric CO2 concentration, Everglades freshwater marsh ecosystems were estimated to be CO2-neutral. As atmospheric CO2 concentration increased and under climate change projections, there were slight shifts in the start and length of the wet season (1 to þ7 days) and a small enhancement in the sink capacity (by 169 to 573 g C m2 century1 ) occurred at both short- and longhydroperiod ecosystems compared to CO2 dynamics under the current climate regime. Over 100 years, rising temperatures increased net CO2 exchange rates (þ1 to 13 g C m2 century1 ) and shifts in precipitation patterns altered cumulative net carbon uptake by þ13 to 46 g C m2 century1 . While changes in ecosystem structure, species composition, and disturbance regimes were beyond the scope of this research, results do indicate that climate change will produce small changes in CO2 dynamics in Everglades freshwater marsh ecosystems and suggest that the hydrologic regime and oligotrophic conditions of Everglades freshwater marshes lowers the ecosystem sensitivity to climate change. Key word

Plasticity in bundle sheath extensions of heterobaric leaves

PREMISE OF THE STUDY: Leaf venation is linked to physiological performance, playing a critical role in ecosystem function. Despite the importance of leaf venation, associated bundle sheath extensions (BSEs) remain largely unstudied. Here, we quantify plasticity in the spacing of BSEs over irradiance and precipitation gradients. Because physiological function(s) of BSEs remain uncertain, we additionally explored a link between BSEs and water use efficiency (WUE). METHODS: We sampled leaves of heterobaric trees along intracrown irradiance gradients in natural environments and growth chambers and correlated BSE spacing to incident irradiance. Additionally, we sampled leaves along a precipitation gradient and correlated BSE spacing to precipitation and bulk δ(13)C, a proxy for intrinsic WUE. BSE spacing was quantified using a novel semiautomatic method on fresh leaf tissue. KEY RESULTS: With increased irradiance or decreased precipitation, Liquidambar styraciflua decreased BSE spacing, while Acer saccharum showed little variation in BSE spacing. Two additional species, Quercus robur and Platanus occidentalis, decreased BSE spacing with increased irradiance in growth chambers. BSE spacing correlated with bulk δ(13)C, a proxy for WUE in L. styraciflua, Q. robur, and P. occidentalis leaves but not in leaves of A. saccharum. CONCLUSIONS: We demonstrated that BSE spacing is plastic with respect to irradiance or precipitation and independent from veins, indicating BSE involvement in leaf adaptation to a microenvironment. Plasticity in BSE spacing was correlated with WUE only in some species, not supporting a function in water relations. We discuss a possible link between BSE plasticity and life history, particularly canopy position.Douglas J. Lynch, Francesca A. McInerney, Lenny L.R. Kouwenberg and Miquel A. Gonzalez-Melerhttp://www.ncbi.nlm.nih.gov/pubmed/2275381

Leaf dark respiration as a function of canopy position in Nothofagus fusca

1. Mass-based and area-based rates of respiration, leaf nitrogen content, leaf total protein content, non-structural carbohydrates and leaf mass per unit area (LMA) all decreased with depth in the canopy of Nothofagus fusca (Hook. F.) Oerst. (Red beech) trees grown for 5 years at ambient (36 Pa) or elevated (66 Pa) CO2 partial pressures. 2. Elevated CO2 partial pressure had a strong effect on dark respiration, decreasing both mass-based and area-based rates at all canopy positions, but had little or no effect on leaf physical and biochemical properties. 3. Leaf sugars, starch, protein, N and LMA were all correlated with respiration rate, and are therefore strong predictors of area-based dark respiration rates. The y axis intercept of regressions of respiration rate on mean leaf N, protein, starch and LMA was lower for plants grown at elevated compared to ambient CO2 partial pressures because of the differential effect of growth at elevated CO2 partial pressure on leaf gas-exchange, chemical and physical characteristics. 4. The lower respiration rates for leaves from trees grown at elevated CO2 partial pressure resulted in a significant increase in the ratio of light-saturated net photosynthesis to respiration, increasing the potential carbon-use efficiency of these leaves

Manejo del ictus agudo. Tratamientos y cuidados específicos de enfermería en la Unidad de Ictus

Resumen: Objetivo: Proporcionar un conjunto de recomendaciones actualizadas y basadas en la evidencia disponible para el manejo del ictus agudo. Nuestro objetivo es proporcionar una base para el desarrollo de los protocolos internos de cada centro, sirviendo de referencia para los cuidados de enfermería. Métodos: Revisión de evidencias disponibles sobre los cuidados del ictus agudo. Se han consultado las guías nacionales e internacionales más recientes. Los niveles de evidencia y grados de recomendación se han basado en la clasificación del Centro de Medicina Basada en la Evidencia de Oxford. Resultados: Se describen la atención y los cuidados del ictus agudo en la fase prehospitalaria, el funcionamiento de código ictus, la atención por el equipo de ictus a la llegada al hospital, los tratamientos de reperfusión y sus limitaciones, el ingreso en la Unidad de Ictus, los cuidados de enfermería en la Unidad de Ictus y el alta hospitalaria. Conclusiones: Estas pautas proporcionan recomendaciones generales basadas en la evidencia actualmente disponible para guiar a los profesionales que atienden a pacientes con ictus agudo. En algunos casos, sin embargo, existen datos limitados demostrando la necesidad de continuar investigando sobre el manejo del ictus agudo. Abstract: Objective: This study provides a series of updated, evidence-based recommendations for the management of acute stroke. We aim to lay a foundation for the development of individual centres’ internal protocols, serving as a reference for nursing care. Methods: We review the available evidence on acute stroke care. The most recent national and international guidelines were consulted. Levels of evidence and degrees of recommendation are based on the Oxford Centre for Evidence-Based Medicine classification. Results: The study describes prehospital acute stroke care, the operation of the code stroke protocol, care provided by the stroke team upon the patient's arrival at hospital, reperfusion treatments and their limitations, admission to the stroke unit, nursing care in the stroke unit, and discharge from hospital. Conclusions: These guidelines provide general, evidence-based recommendations to guide professionals who care for patients with acute stroke. However, limited data are available on some aspects, showing the need for continued research on acute stroke management