Spectral biases in tree-ring climate proxies

External forcing and internal dynamics result in climate system variability ranging from sub-daily weather to multi-centennial trends and beyond1, 2. State-of-the-art palaeoclimatic methods routinely use hydroclimatic proxies to reconstruct temperature (for example, refs 3, 4), possibly blurring differences in the variability continuum of temperature and precipitation before the instrumental period. Here, we assess the spectral characteristics of temperature and precipitation fluctuations in observations, model simulations and proxy records across the globe. We find that whereas an ensemble of different general circulation models represents patterns captured in instrumental measurements, such as land–ocean contrasts and enhanced low-frequency tropical variability, the tree-ring-dominated proxy collection does not. The observed dominance of inter-annual precipitation fluctuations is not reflected in the annually resolved hydroclimatic proxy records. Likewise, temperature-sensitive proxies overestimate, on average, the ratio of low- to high-frequency variability. These spectral biases in the proxy records seem to propagate into multi-proxy climate reconstructions for which we observe an overestimation of low-frequency signals. Thus, a proper representation of the high- to low-frequency spectrum in proxy records is needed to reduce uncertainties in climate reconstruction efforts.

Organic vs. Conventional Grassland Management: Do N-15 and C-13 Isotopic Signatures of Hay and Soil Samples Differ?

Distinguishing organic and conventional products is a major issue of food security and authenticity. Previous studies successfully used stable isotopes to separate organic and conventional products, but up to now, this approach was not tested for organic grassland hay and soil. Moreover, isotopic abundances could be a powerful tool to elucidate differences in ecosystem functioning and driving mechanisms of element cycling in organic and conventional management systems. Here, we studied the delta N-15 and delta C-13 isotopic composition of soil and hay samples of 21 organic and 34 conventional grasslands in two German regions. We also used Delta delta N-15 (delta N-15 plant - delta N-15 soil) to characterize nitrogen dynamics. In order to detect temporal trends, isotopic abundances in organic grasslands were related to the time since certification. Furthermore, discriminant analysis was used to test whether the respective management type can be deduced from observed isotopic abundances. Isotopic analyses revealed no significant differences in delta C-13 in hay and delta C-13 in both soil and hay between management types, but showed that delta C-13 abundances were significantly lower in soil of organic compared to conventional grasslands. delta C-15 values implied that management types did not substantially differ in nitrogen cycling. Only delta C-13 in soil and hay showed significant negative relationships with the time since certification. Thus, our result suggest that organic grasslands suffered less from drought stress compared to conventional grasslands most likely due to a benefit of higher plant species richness, as previously shown by manipulative biodiversity experiments. Finally, it was possible to correctly classify about two third of the samples according to their management using isotopic abundances in soil and hay. However, as more than half of the organic samples were incorrectly classified, we infer that more research is needed to improve this approach before it can be efficiently used in practice.

Table-mounted ring retractor for consistent visualization in endoscopy-assisted anterior reconstruction of burst fractures of the thoracolumbar junction

The authors tested an autoclavable external ring retractor, fixed to the operation table, for the endoscopic reconstruction of anterior column injuries of the thoracolumbar junction. It served as a retractor for the diaphragm, and offered a stable support for the scope and other instruments, making an assistant superfluous. Moreover, it allowed bimanual manipulation. Of course, the two-dimensional image, provided by the scope, necessitated proper eye-hand coordination. Twenty-eight consecutive patients underwent either a monosegmental (n = 10) or a bisegmental (n = 18) anterior stabilization in the area Th11L1. Three portals were necessary, but an assistant was not needed. The overall (mean +/- SD) operating time was 196 +/- 56 min, the blood loss was 804 +/- 719 mL. Intraoperatively, one epidural bleeding and a single screw cut-out occurred. All complications were managed endoscopically. Postoperatively, evacuation of a haemothorax (n = 1) was necessary. In all patients, wounds and fractures healed uneventfully. The combination of the endoscopic technique and the retractor system was feasible, successful, safe, and time efficient. Moreover, it allowed for anterior instrumentation of thoracolumbar fractures by a single surgeon. It became the standard approach in the authors' department.

Genomic signatures of relaxed disruptive selection associated with speciation reversal in whitefish

Background: Speciation reversal: the erosion of species differentiation via an increase in introgressive hybridization due to the weakening of previously divergent selection regimes, is thought to be an important, yet poorly understood, driver of biodiversity loss. Our study system, the Alpine whitefish (Coregonus spp.) species complex is a classic example of a recent postglacial adaptive radiation: forming an array of endemic lake flocks, with the independent origination of similar ecotypes among flocks. However, many of the lakes of the Alpine radiation have been seriously impacted by anthropogenic nutrient enrichment, resulting in a collapse in neutral genetic and phenotypic differentiation within the most polluted lakes. Here we investigate the effects of eutrophication on the selective forces that have shaped this radiation, using population genomics. We studied eight sympatric species assemblages belonging to five independent parallel adaptive radiations, and one species pair in secondary contact. We used AFLP markers, and applied FST outlier (BAYESCAN, DFDIST) and logistic regression analyses (MATSAM), to identify candidate regions for disruptive selection in the genome and their associations with adaptive traits within each lake flock. The number of outlier and adaptive trait associated loci identified per lake were then regressed against two variables (historical phosphorus concentration and contemporary oxygen concentration) representing the strength of eutrophication. Results: Whilst we identify disruptive selection candidate regions in all lake flocks, we find similar trends, across analysis methods, towards fewer disruptive selection candidate regions and fewer adaptive trait/candidate loci associations in the more polluted lakes. Conclusions: Weakened disruptive selection and a concomitant breakdown in reproductive isolating mechanisms in more polluted lakes has lead to increased gene flow between coexisting Alpine whitefish species. We hypothesize that the resulting higher rates of interspecific recombination reduce either the number or extent of genomic islands of divergence surrounding loci evolving under disruptive natural selection. This produces the negative trend seen in the number of selection candidate loci recovered during genome scans of whitefish species flocks, with increasing levels of anthropogenic eutrophication: as the likelihood decreases that AFLP restriction sites will fall within regions of heightened genomic divergence and therefore be classified as FST outlier loci. This study explores for the first time the potential effects of human-mediated relaxation of disruptive selection on heterogeneous genomic divergence between coexisting species.

Atypical Mo isotope signatures in eastern Mediterranean sediments

Suboxic sapropel S1 sediments of the eastern Mediterranean carry an untypically light δ98/95Mo signal, being even lighter than oxic Mn-enriched sediments and Mn-crusts/nodules, which were previously thought to carry the lightest Mo isotope values. The evaluation and comparison of oxic S1, diagenetically overprinted oxic S1, and suboxic S1 sediments indicates that this light isotope signal is primarily an oxic signal that has been overprinted by secondary diagenetic processes occurring after sediment burial. Such secondary processes bear the potential of additional Mo isotope fractionation in particular in non-steady state diagenetic environments that involve the discontinuous re-location of the redox boundary.

Signatures of slope failures and river-delta collapses in a perialpine lake (Lake Lucerne, Switzerland)

Historical reports from the 17th Century document two destructive tsunamis with runups exceeding 5 m, affecting proximal basins of Lake Lucerne (Switzerland). One event in AD 1601 is coeval with a strong nearby earthquake (MW ca 5.9), which caused extensive slope failures in many parts of the lake. The second event in AD 1687 is associated with an apparently spontaneous partial collapse of the Muota river delta. This study combines high-resolution bathymetry, reflection seismic and lithological data in order to document the sedimentary and morphological signatures of the two subaqueous mass movements that probably generated the observed tsunamis. Such mass movements are significant as a common sedimentation process and as natural hazard in fjord-type lakes and similar environments. The deposits, covering large parts of the basins with thicknesses reaching >10 m, consist of two subunits: A lower ‘massflow deposit’ contains variably deformed sediments from the source areas. Its emplacement affected pre-existing sediments, incorporating thin sediment slices into the deposit and increasing its volume. Deep-reaching deformation near This is an Accepted Article that has been peer-reviewed and approved for publication in the Sedimentology, but has yet to undergo copy-editing and proof correction.

What are predictors for patients' quality of life after pelvic ring fractures?

Background Our knowledge of factors influencing mortality of patients with pelvic ring injuries and the impact of associated injuries is currently based on limited information. Questions/purposes Weidentified the (1) causes and time of death, (2) demography, and (3) pattern and severity of injuries in patients with pelvic ring fractures who did not survive. Methods We prospectively collected data on 5340 patients listed in the German Pelvic Trauma Registry between April 30, 2004 and July 29, 2011; 3034 of 5340 (57%) patientswere female. Demographic data and parameters indicating the type and severity of injury were recorded for patients who died in hospital (nonsurvivors) and compared with data of patients who survived (survivors). The median followup was 13 days (range, 0–1117 days). Results A total of 238 (4%) patients died a median of 2 days after trauma. The main cause of death was massive bleeding (34%), predominantly from the pelvic region (62% of all patients who died because of massive bleeding). Fifty six percent of nonsurvivors and 43% of survivors were male. Nonsurvivors were characterized by a higher incidence of complex pelvic injuries (32% versus 8%), less isolated pelvic ring fractures (13% versus 49%), lower initial blood hemoglobin concentration (6.7 ± 2.9 versus 9.8 ± 3.0 g/dL) and systolic arterial blood pressure (77 ± 27 versus 106 ± 24 mmHg), and higher injury severity score (ISS) (35 ± 16 versus 15 ± 12). Conclusion Patients with pelvic fractures who did not survive were characterized by male gender, severe multiple trauma, and major hemorrhage.

Emergency stabilization of the pelvic ring: Clinical comparison between three different techniques

Background: Emergency devices for pelvic ring stabilization include circumferential sheets, pelvic binders, and c-clamps. Our knowledge of the outcome of these techniques is currently based on limited information. Methods: Using the dataset of the German Pelvic Trauma Registry, demographic and injury-associated characteristics as well as the outcome of pelvic fracture patients after sheet, binder, and c-clamp treatment was compared. Outcome parameters included transfusion requirement of packed red blood cells, length of hospital stay, mortality, and incidence of lethal pelvic bleeding. Results: Two hundred seven of 6137 (3.4%) patients documented in the German Pelvic Trauma Registry between April 30th 2004 and January 19th 2012 were treated by sheets, binders, or c-clamps. In most cases, c-clamps (69%) were used, followed by sheets (16%), and binders (15%). The median age was significantly lower in patients treated with binders than in patients treated with sheets or c-clamps (26 vs. 47 vs. 42 years, p = 0.01). Sheet wrapping was associated with a significantly higher incidence of lethal pelvic bleeding compared to binder or c-clamp stabilization (23% vs. 4% vs. 8%). No significant differences between the study groups were found in sex, fracture type, blood haemoglobin concentration, arterial blood pressure, Injury Severity Score, the incidence of additional pelvic packing and arterial embolization, need of red blood cell transfusion, length of hospitalisation, and mortality. Conclusions: The data suggest that emergency stabilization of the pelvic ring by binders and c-clamps is associated with a lower incidence of lethal pelvic bleeding compared to sheet wrapping.