Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates

Extreme drought events and plant invasions are major drivers of global change that can critically affect ecosystem functioning and alter ecosystem-atmosphere exchange. Invaders are expanding worldwide and extreme drought events are projected to increase in frequency and intensity. However, very little is known on how these drivers may interact to affect the functioning and resilience of ecosystems to extreme events. Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event (2011/2012) in a Mediterranean woodland, we show that native shrub invasion and extreme drought synergistically reduced ecosystem transpiration and the resilience of key-stone oak tree species. Ecosystem transpiration was dominated by the water use of the invasive shrub Cistus ladanifer, which further increased after the extreme drought event. Meanwhile, the transpiration of key-stone tree species decreased, indicating a competitive advantage in favour of the invader. Our results suggest that in Mediterranean-type climates the invasion of water spending species and projected recurrent extreme drought events may synergistically cause critical drought tolerance thresholds of key-stone tree species to be surpassed, corroborating observed higher tree mortality in the invaded ecosystems. Ultimately, this may shift seasonally water limited ecosystems into less desirable alternative states dominated by water spending invasive shrubs

A proposed methodology for the correction of the Leaf Area Index measured with a ceptometer for pinus and eucalyptus forests = Proposta de uma methodologia para a correcao do indice de area foliar medido pelo ceptometro em provoamentos de pinus e eucalyptus

Leaf area index (LAI) is an important parameter controlling many biological and physiological processes associated with vegetation on the Earth's surface, such as photosynthesis, respiration, transpiration, carbon and nutrient cycle and rainfall interception. LAI can be measured indirectly by sunfleck ceptometers in an easy and non-destructive way but this practical methodology tends to underestimated when measured by these instruments. Trying to correct this underestimation, some previous studies heave proposed the multiplication of the observed LAI value by a constant correction factor. The assumption of this work is LAI obtained from the allometric equations are not so problematic and can be used as a reference LAI to develop a new methodology to correct the ceptometer one. This new methodology indicates that the bias (the difference between the ceptometer and the reference LAI) is estimated as a function of the basal area per unit ground area and that bias is summed to the measured value. This study has proved that while the measured Pinus LAI needs a correction, there is no need for that correction for the Eucalyptus LAI. However, even for this last specie the proposed methodology gives closer estimations to the real LAI values

Auswirkungen der Landwirtschaft auf physikalische und chemische Funktionen Europäischer Torfböden

Torfböden bieten zahlreiche Funktionen: sie bilden den weltweit größten terrestrischen Kohlenstoffspeicher, stellen wichtige Nährstofffilter dar und erhöhen hydrologische Pufferkapazitäten. Torfböden sind in Mittel- und Nordeuropa zum überwiegenden Teil landwirtschaftlich genutzt. Kultivierung führt zu extremen Mineralisierungsraten der organischen Substanz und hohen THG-Emissionen. Die Anfälligigkeit für Bodensackung, Boden- und Wasserqualitätsverschlechterung und folglich Ernteausfall steigt. Das Ziel dieser Studie ist es, Auswirkungen des Agrarmanagements auf Funktionen von Torfböden in Europa zu analysieren. In Deutschland, den Niederlanden, Dänemark, Estland, Finnland und Schweden wurden standardisierte Bodenkartierungen, bodenphysikalische und -chemische Analysen, Grundwassermonitoring und Betriebsdatenerhebungen durchgeführt. Die Ergebnisse belegen einen starken Einfluss der bisherigen Bewirtschaftung auf die Funktionen von Torfböden in Europa. Torfböden unter intensiver Ackernutzung bieten im Vergleich zu extensiver und intensiver Grünlandnutzung die niedrigste Tragfähigkeit in den oberen 10 cm, welche eine erfolgreiche landwirtschaftliche Praxis auf Torfböden stark einschränkt. Der Unterschied lässt sich allein durch Wurzelstabilisierung erklären, da die Bodenverdichtung in den oberen 25cm unter Ackernutzung am höchsten ist. Hieraus folgt eine starke Verringerung der nutzbaren Feldkapazität und der gesättigten hydraulischen Leitfähigkeit, wodurch sich hydrologische Probleme wie Staunässe und Trockenstress, die häufig auf kultivierten Torfböden vorkommen, weiter intensivieren. Bodenkohlenstoffvorräte sinken deutlich mit steigender Nutzungsintensität und sind im Vergleich auf extensivem Grünland am höchsten. Dies wird bestätigt durch den Zersetzungsgrad, der hier am niedrigsten ist. Die Ergebnisse deuten auf eine starke Auswirkung des Managements auf Bodenkohlenstoffverluste und Torfkonservierung auf europäischer Ebene hin

Soil water content effects on net ecosystem CO2 exchange and actual evapotranspiration in a Mediterranean semiarid savanna of Central Chile

Biosphere-atmosphere water and carbon fluxes depend on ecosystem structure, and their magnitudes and seasonal behavior are driven by environmental and biological factors. We studied the seasonal behavior of net ecosystem CO2 exchange (NEE), Gross Primary Productivity (GPP), Ecosystem Respiration (RE), and actual evapotranspiration (ETa) obtained by eddy covariance measurements during two years in a Mediterranean Acacia savanna ecosystem (Acacia caven) in Central Chile. The annual carbon balance was −53 g C m−2 in 2011 and −111 g C m−2 in 2012, showing that the ecosystem acts as a net sink of CO2, notwithstanding water limitations on photosynthesis observed in this particularly dry period. Total annual ETa was of 128 mm in 2011 and 139 mm in 2012. Both NEE and ETa exhibited strong seasonality with peak values recorded in the winter season (July to September), as a result of ecosystem phenology, soil water content and rainfall occurrence. Consequently, the maximum carbon assimilation rate occurred in wintertime. Results show that soil water content is a major driver of GPP and RE, defining their seasonal patterns and the annual carbon assimilation capacity of the ecosystem, and also modulating the effect that solar radiation and air temperature have on NEE components at shorter time scales.This work was funded by FONDECYT projects 1120713 and 1170429, a grant from the Inter-American Institute for Global Change Research (IAI) [grant number CRN3056], which is supported by the US National Science Foundation [grant number GEO-1128040], and the Spanish Ministry of Economy and Competitiveness project GEI Spain (CGL2014-52838-C2-1-R), including ERDF founds. F. Bravo-Martínez is grateful to CONICYT for the grants “Formación de Capital Humano Avanzado-2009′′, “Beca de Apoyo al término de la tesis doctoral-2012′′, and CORFO INNOVA Grant N° 09CN14-5704. We thank to Enrique Pérez Sanchez-Cañete and Borja Ruíz- Reverter for technical support. We also thank “CODELCO–División Andina” for use of the site. C. Montes acknowledges the NASA Postdoctoral Program and to Universities Space Research Association

"Prognostic implications of residual tricuspid regurgitation grading after transcatheter tricuspid valve repair

BackgroundThe safety profile of transcatheter tricuspid valve (TTV) repair techniques is well established, but residual tricuspid regurgitation (TR) remains a concern.ObjectivesThe authors sought to assess the impact of residual TR severity post–TTV repair on survival.MethodsWe evaluated the survival rate at 2 years of 613 patients with severe isolated functional TR who underwent TTV repair in TRIGISTRY according to the severity of residual TR at discharge using a 3-grade (mild, moderate, and severe) or 4-grade scheme (mild, mild to moderate, moderate to severe, and severe).ResultsResidual TR was none/mild in 33%, moderate in 52%, and severe in 15%. The 2-year adjusted survival rates significantly differed between the 3 groups (85%, 70%, and 44%, respectively; restricted mean survival time [RMST]: P = 0.0001). When the 319 patients with moderate residual TR were subdivided into mild to moderate (n = 201, 33%) and moderate to severe (n = 118, 19%), the adjusted survival rate was also significantly different between groups (85%, 80%, 55%, and 44%, respectively; RMST: P = 0.001). Survival was significantly lower in patients with moderate to severe residual TR compared to patients with mild to moderate residual TR (P = 0.006). No difference in survival rates was observed between patients with no/mild and mild to moderate residual TR (P = 0.67) or between patients with moderate to severe and severe residual TR (P = 0.96).ConclusionsThe moderate residual TR group was heterogeneous and encompassed patients with markedly different clinical outcomes. Refining TR grade classification with a more granular 4-grade scheme improved outcome prediction. Our results highlight the importance of achieving a mild to moderate or lower residual TR grade during TTV repair, which could define a successful intervention.Cardiolog

Embolization of percutaneous left atrial appendage closure devices: Timing, management and clinical outcomes.

peer reviewed[en] BACKGROUND: Left atrial appendage (LAA) occluder embolization is an infrequent but serious complication. OBJECTIVES: We aim to describe timing, management and clinical outcomes of device embolization in a multi-center registry. METHODS: Patient characteristics, imaging findings and procedure and follow-up data were collected retrospectively. Device embolizations were categorized according to 1) timing 2) management and 3) clinical outcomes. RESULTS: Sixty-seven centers contributed data. Device embolization occurred in 108 patients. In 70.4 % of cases, it happened within the first 24 h of the procedure. The device was purposefully left in the LA and the aorta in two (1.9 %) patients, an initial percutaneous retrieval was attempted in 81 (75.0 %) and surgery without prior percutaneous retrieval attempt was performed in 23 (21.3 %) patients. Two patients died before a retrieval attempt could be made. In 28/81 (34.6 %) patients with an initial percutaneous retrieval attempt a second, additional attempt was performed, which was associated with a high mortality (death in patients with one attempt: 2.9 % vs. second attempt: 21.4 %, p < 0.001). The primary outcome (bailout surgery, cardiogenic shock, stroke, TIA, and/or death) occurred in 47 (43.5 %) patients. Other major complications related to device embolization occurred in 21 (19.4 %) patients. CONCLUSIONS: The majority of device embolizations after LAA closure occurs early. A percutaneous approach is often the preferred method for a first rescue attempt. Major adverse event rates, including death, are high particularly if the first retrieval attempt was unsuccessful. CONDENSED ABSTRACT: This dedicated multicenter registry examined timing, management, and clinical outcome of device embolization. Early embolization (70.4 %) was most frequent. As a first rescue attempt, percutaneous retrieval was preferred in 75.0 %, followed by surgical removal (21.3 %). In patients with a second retrieval attempt a higher mortality (death first attempt: 2.9 % vs. death second attempt: 24.1 %, p < 0.001) was observed. Mortality (10.2 %) and the major complication rate after device embolization were high

Quantification of dynamic soil–vegetation feedbacks following an isotopically labelled precipitation pulse

The presence of vegetation alters hydrological cycles of ecosystems. Complex plant-soil interactions govern the fate of precipitation input and water transitions through ecosystem compartments. Disentangling these interactions is a major challenge in the field of ecohydrology and a pivotal foundation for understanding the carbon cycle of semiarid ecosystems. Stable water isotopes can be used in this context as tracer to quantify water movement through soilvegetation- atmosphere interfaces. The aim of this study is to disentangle vegetation effects on soil water infiltration and distribution as well as dynamics of soil evaporation and grassland water use in a Mediterranean cork oak woodland during dry conditions. An irrigation experiment using delta O-18 labelled water was carried out in order to quantify distinct effects of tree and herbaceous vegetation on the infiltration and distribution of event water in the soil profile. Dynamic responses of soil and herbaceous vegetation fluxes to precipitation regarding event water use, water uptake depth plasticity, and contribution to ecosystem soil evaporation and transpiration were quantified. Total water loss to the atmosphere from bare soil was as high as from vegetated soil, utilizing large amounts of unproductive evaporation for transpiration, but infiltration rates decreased. No adjustments of main root water uptake depth to changes in water availability could be observed during the experiment. This forces understorey plants to compete with adjacent trees for water in deeper soil layers at the onset of summer. Thus, understorey plants are subjected to chronic water deficits faster, leading to premature senescence at the onset of drought. Despite this water competition, the presence of cork oak trees fosters infiltration and reduces evapotranspirative water losses from the understorey and the soil, both due to altered microclimatic conditions under crown shading. This study highlights complex soilplant- atmosphere and inter-species interactions controlling rain pulse transitions through a typical Mediterranean savannah ecosystem, disentangled by the use of stable water isotopes

Quantification of dynamic soil–vegetation feedbacks following an isotopically labelled precipitation pulse

The presence of vegetation alters hydrological cycles of ecosystems. Complex plant–soil interactions govern the fate of precipitation input and water transitions through ecosystem compartments. Disentangling these interactions is a major challenge in the field of ecohydrology and a pivotal foundation for understanding the carbon cycle of semi-arid ecosystems. Stable water isotopes can be used in this context as tracer to quantify water movement through soil–vegetation–atmosphere interfaces. The aim of this study is to disentangle vegetation effects on soil water infiltration and distribution as well as dynamics of soil evaporation and grassland water use in a Mediterranean cork oak woodland during dry conditions. An irrigation experiment using δ18O labelled water was carried out in order to quantify distinct effects of tree and herbaceous vegetation on the infiltration and distribution of event water in the soil profile. Dynamic responses of soil and herbaceous vegetation fluxes to precipitation regarding event water use, water uptake depth plasticity, and contribution to ecosystem soil evaporation and transpiration were quantified. Total water loss to the atmosphere from bare soil was as high as from vegetated soil, utilizing large amounts of unproductive evaporation for transpiration, but infiltration rates decreased. No adjustments of main root water uptake depth to changes in water availability could be observed during the experiment. This forces understorey plants to compete with adjacent trees for water in deeper soil layers at the onset of summer. Thus, understorey plants are subjected to chronic water deficits faster, leading to premature senescence at the onset of drought. Despite this water competition, the presence of cork oak trees fosters infiltration and reduces evapotranspirative water losses from the understorey and the soil, both due to altered microclimatic conditions under crown shading. This study highlights complex soil–plant–atmosphere and inter-species interactions controlling rain pulse transitions through a typical Mediterranean savannah ecosystem, disentangled by the use of stable water isotopes