Thinning of beech forests stocking on shallow calcareous soil maintains soil C and N stocks in the long run

Sustainable forest management should avoid disturbance and volatilization of the soil carbon (C) and nitrogen (N) stocks both under present and projected future climate. Earlier studies have shown that thinning of European beech forests induces a strong initial perturbation of the soil C and N cycles in shallow Rendzic Leptosol, which consists of lower soil N retention and strongly enhanced gaseous losses observed over several years. Persistence of these effects could decrease soil organic matter (SOM) levels and associated soil functions such as erosion protection, nutrient retention, and fertility. Therefore, we resampled untreated control and thinned stands a decade after thinning at sites representing both typical present day and projected future climatic conditions for European beech forests. We determined soil organic C and total N stocks, as well as δ13C and δ15N as integrators of changes in soil C and N cycles. Thinning did not alter these parameters at any of the sampled sites, indicating that initial effects on soil C and N cycles constitute short-term perturbations. Consequently, thinning may be considered a sustainable beech forest management strategy with regard to the maintenance of soil organic C and total N stocks both under present and future climat

Semiconductor charge qubit relaxation due to two-phonon processes

We theoretically study the relaxation of electron orbital states of a double quantum dot system due to two-phonon processes. In particular, we calculate how the relaxation rates depend on the separation distance between the quantum dots, the strength of quantum dot confinement, and the lattice temperature. Enhancement of the rates by specific inter-dot distances and lattice temperatures, and the relative strength of different scattering channels are discussed. Our results show that although at low temperatures ($T \sim 1$ K) two-phonon processes are almost four orders of magnitude weaker compared to one-phonon processes in relaxing electron orbital states, at room temperature they are as important as one-phonon processes.Comment: Submitted to PR

Enhanced ozone strongly reduces carbon sink strength of adult beech (Fagus sylvatica) – Resume from the free-air fumigation study at Kranzberg Forest

Ground-level ozone (O3) has gained awareness as an agent of climate change. In this respect, key results are comprehended from a unique 8-year free-air O3-fumigation experiment, conducted on adult beech (Fagus sylvatica) at Kranzberg Forest (Germany). A novel canopy O3 exposure methodology was employed that allowed whole-tree assessment in situ under twice-ambient O3 levels. Elevated O3 significantly weakened the C sink strength of the tree–soil system as evidenced by lowered photosynthesis and 44% reduction in whole-stem growth, but increased soil respiration. Associated effects in leaves and roots at the gene, cell and organ level varied from year to year, with drought being a crucial determinant of O3 responsiveness. Regarding adult individuals of a late-successional tree species, empirical proof is provided first time in relation to recent modelling predictions that enhanced ground-level O3 can substantially mitigate the C sequestration of forests in view of climate change

Interactive regulation of root exudation and rhizosphere denitrification by plant metabolite content and soil properties

Aims Root exudates are known to shape microbial activities in the rhizosphere and to be of fundamental importance for plant-soil-microbe-carbon–nitrogen interactions. However, it remains unclear how and to what extent the amount and composition of root exudation affects rhizosphere denitrification. Methods In this study root exudation patterns and rhizosphere denitrification enzyme activity of three different grass species grown on two agricultural soils under two different soil water contents were investigated under controlled conditions. Results We found that root exudation of primary metabolites largely depends on plant species, soil type, soil moisture and root exudation medium. In dependence of soil properties and soil moisture levels, plants largely controlled amount and quality of root exudation. Exudates affected denitrification activity and plant–microbe competition for nitrate. Specifically, exudation of organic acids stimulated denitrifying activity while the sugar lyxose exhibited an inhibitory effect. Conclusion We show that interactive effects of physicochemical soil properties and species-specific effects of plant metabolism on root exudation act as a dominant control of rhizosphere denitrification, thereby explaining more than half of its variance

Heart Rate Variability and Recurrent Stroke and Myocardial Infarction in Patients With Acute Mild to Moderate Stroke

Objectives: In patients with acute ischemic stroke, reduced heart rate variability (HRV) may indicate poor outcome. We tested whether HRV in the acute phase of stroke is associated with higher rates of mortality, recurrent stroke, myocardial infarction (MI) or functional outcome. Materials and Methods: Patients with acute mild to moderate ischemic stroke without known atrial fibrillation were prospectively enrolled to the investigator-initiated Heart and Brain interfaces in Acute Ischemic Stroke (HEBRAS) study (NCT 02142413). HRV parameters were assessed during the in-hospital stay using a 10-min section of each patient's ECG recording at day- and nighttime, calculating time and frequency domain HRV parameters. Frequency of a combined endpoint of recurrent stroke, MI or death of any cause and the respective individual events were assessed 12 months after the index stroke. Patients' functional outcome was measured by the modified Rankin Scale (mRS) at 12 months. Results: We included 308 patients (37% female, median NIHSS = 2 on admission, median age 69 years). Complete follow-up was achieved in 286/308 (93%) patients. At 12 months, 32 (9.5%), 5 (1.7%) and 13 (3.7%) patients had suffered a recurrent stroke, MI or death, respectively. After adjustment for age, sex, stroke severity and vascular risk factors, there was no significant association between HRV and recurrent stroke, MI, death or the combined endpoint. We did not find a significant impact of HRV on a mRS ≥ 2 12 months after the index stroke. Conclusion: HRV did not predict recurrent vascular events in patients with acute mild to moderate ischemic stroke

Redox states of glutathione and ascorbate in root tips of poplar (Populus tremula×P. alba) depend on phloem transport from the shoot to the roots

Glutathione (GSH) and ascorbate (ASC) are important antioxidants that are involved in stress defence and cell proliferation of meristematic root cells. In principle, synthesis of ASC and GSH in the roots as well as ASC and GSH transport from the shoot to the roots by phloem mass flow is possible. However, it is not yet known whether the ASC and/or the GSH level in roots depends on the supply from the shoot. This was analysed by feeding mature leaves with [14C]ASC or [35S]GSH and subsequent detection of the radiolabel in different root fractions. Quantitative dependency of root ASC and GSH on shoot-derived ASC and GSH was investigated with poplar (Populus tremula×P. alba) trees interrupted in phloem transport. [35S]GSH is transported from mature leaves to the root tips, but is withdrawn from the phloem along the entire transport path. When phloem transport was interrupted, the GSH content in root tips halved within 3 d. [14C]ASC is also transported from mature leaves to the root tips but, in contrast to GSH, ASC is not removed from the phloem along the transport path. Accordingly, ASC accumulates in root tips. Interruption of phloem transport disturbed the level and the ASC redox state within the entire root system. Diminished total ASC levels were attributed mainly to a decline of dehydroascorbate (DHA). As the redox state of ASC is of particular significance for root growth and development, it is concluded that phloem transport of ASC may constitute a shoot to root signal to coordinate growth and development at the whole plant level

Calcium sensor kinase activates potassium uptake systems in gland cells of Venus flytraps

The Darwin plant Dionaea muscipula is able to grow on mineral-poor soil, because it gains essential nutrients from captured animal prey. Given that no nutrients remain in the trap when it opens after the consumption of an animal meal, we here asked the question of how Dionaea sequesters prey-derived potassium. We show that prey capture triggers expression of a K+ uptake system in the Venus flytrap. In search of K+ transporters endowed with adequate properties for this role, we screened a Dionaea expressed sequence tag (EST) database and identified DmKT1 and DmHAK5 as candidates. On insect and touch hormone stimulation, the number of transcripts of these transporters increased in flytraps. After cRNA injection of K+-transporter genes into Xenopus oocytes, however, both putative K+ transporters remained silent. Assuming that calcium sensor kinases are regulating Arabidopsis K+ transporter 1 (AKT1), we coexpressed the putative K+ transporters with a large set of kinases and identified the CBL9-CIPK23 pair as the major activating complex for both transporters in Dionaea K+ uptake. DmKT1 was found to be a K+-selective channel of voltage-dependent high capacity and low affinity, whereas DmHAK5 was identified as the first, to our knowledge, proton-driven, high-affinity potassium transporter with weak selectivity. When the Venus flytrap is processing its prey, the gland cell membrane potential is maintained around -120 mV, and the apoplast is acidified to pH 3. These conditions in the green stomach formed by the closed flytrap allow DmKT1 and DmHAK5 to acquire prey-derived K+, reducing its concentration from millimolar levels down to trace levels

Clinical correlates and prognostic impact of neurologic disorders in Takotsubo syndrome

Cardiac alterations are frequently observed after acute neurological disorders. Takotsubo syndrome (TTS) represents an acute heart failure syndrome and is increasingly recognized as part of the spectrum of cardiac complications observed after neurological disorders. A systematic investigation of TTS patients with neurological disorders has not been conducted yet. The aim of the study was to expand insights regarding neurological disease entities triggering TTS and to investigate the clinical profile and outcomes of TTS patients after primary neurological disorders. The International Takotsubo Registry is an observational multicenter collaborative effort of 45 centers in 14 countries (ClinicalTrials.gov, identifier NCT01947621). All patients in the registry fulfilled International Takotsubo Diagnostic Criteria. For the present study, patients were included if complete information on acute neurological disorders were available. 2402 patients in whom complete information on acute neurological status were available were analyzed. In 161 patients (6.7%) an acute neurological disorder was identified as the preceding triggering factor. The most common neurological disorders were seizures, intracranial hemorrhage, and ischemic stroke. Time from neurological symptoms to TTS diagnosis was <= 2 days in 87.3% of cases. TTS patients with neurological disorders were younger, had a lower female predominance, fewer cardiac symptoms, lower left ventricular ejection fraction, and higher levels of cardiac biomarkers. TTS patients with neurological disorders had a 3.2-fold increased odds of in-hospital mortality compared to TTS patients without neurological disorders. In this large-scale study, 1 out of 15 TTS patients had an acute neurological condition as the underlying triggering factor. Our data emphasize that a wide spectrum of neurological diseases ranging from benign to life-threatening encompass TTS. The high rates of adverse events highlight the need for clinical awareness