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With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed. [ABSTRACT FROM AUTHOR]

With the increased planting of non-native trees within urban environments there is a need for investigating the impacts they may have on the indigenous biodiversity. In this study, we explored the diversity of epiphytic lichens and bryophytes as well as the tree-related microhabitats on planted, non-native green ash Fraxinus pennsylvanica and compared it to that of indigenous Fraxinus excelsior and Quercus robur. We conducted sampling on trees of similar growing conditions and size within two cities of eastern Germany (Dresden and Dessau-Roßlau). In our analysis we did not find any significant differences in epiphyte diversity and abundance. By contrast, microhabitat diversity was significantly higher on F. pennsylvanica than on the indigenous tree species, which we attribute to the pioneer character of F. pennsylvanica with faster ageing. Our results underline a low impact of F. pennsylvanica on epiphytic lichen and bryophyte diversity, while indigenous animals might even benefit from the higher diversity and frequency of microhabitats on trees of this species. Therefore, its use as an ornamental tree should not be generally rejected in urban environments. [ABSTRACT FROM AUTHOR]

Old-growth forests are important stores for carbon as they may accumulate C for centuries. The alteration of biomass and soil carbon pools across the development stages of a forest dynamics cycle has rarely been quantified. We studied the above- and belowground C stocks in the five forest development stages (regeneration to decay stage) of a montane spruce ( Picea abies) forest of the northern German Harz Mountains, one of Central Europe's few forests where the natural forest dynamics have not been disturbed by man for several centuries. The over-mature and decay stages had the largest total (up to 480 Mg C ha) and aboveground biomass carbon pools (200 Mg C ha) with biomass C stored in dead wood in the decay stage. The soil C pool (220-275 Mg C ha, 0-60 cm) was two to three times larger than in temperate lowland spruce forests and remained invariant across the forest dynamics cycle. On the landscape level, taking into account the frequency of the five forest development stages, the total carbon pool was approximately 420 Mg C ha. The results evidence the high significance of over-mature and decaying stages of temperate mountain forests not only for conserving specialized forest organisms but also for their large carbon storage potential. [ABSTRACT FROM AUTHOR]

Abstract: Lichen substances (i.e. lichen-specific carbon-based secondary compounds) are known to be involved in the uptake and immobilization of metal ions, though the biochemical mechanisms of this interaction are largely unexplained. Previous research on potential effects of lichen substances on heavy metal uptake and tolerance mostly focused on lichens in heavily polluted areas with exceptionally high metal concentrations. In the present study, we aimed at gathering information as to whether lichen substances might be involved in the fine-tuning of metal uptake even at not or low-polluted sites. Therefore, we studied lichen substance concentrations in the epiphytic lichen Hypogymnia physodes and metal concentrations in its substratum in a montane spruce forest of Germany. H. physodes produces two depsides and five depsidones, which had been shown to be involved in metal homeostasis, namely in Cu and Mn uptake, in previous laboratory experiments. The amount of lichen substances increased with increasing heavy metal concentration in the substratum, though the latter varied only in the range of a few μmolg−1 between the sample trees. Variability of lichen substance concentrations in H. physodes within the individual trees was low. Among the different lichen substances of H. physodes, the amount of the depsidone physodalic acid relative to the total of lichen substances was most closely correlated to the concentrations of Cu and Mn in the substratum, whereas the amount of the depsidone 3-hydroxyphysodic acid decreased both with increasing concentrations of these two metals and physodalic acid. Thus, our data suggest that lichen substances contribute to metal homeostasis not only in heavy metal-rich habitats, but also at not or low-polluted sites where the lichen substances apparently help to maintain constant intracellular metal concentrations despite of spatially varying availabilities of metal ions. [Copyright &y& Elsevier]

Aims: The MicraVR™ transcatheter pacing system (TPS) has been implemented into clinical routine for several years. The primary recipients are patients in need for VVI pacing due to bradycardia in the setting of atrial fibrillation (AF). Implantation safety and acute success have been proven in controlled studies and registries. So far only few long-term real-life data on TPS exist. We report indication, procedure and outcome data from two high-volume implanting German centers., Methods: Between 2016 and 2019, 188 (of 303) patients were included. During follow-up (FU), TPS interrogation was performed after 4 weeks and thereafter every 6 months., Results: Indication for TPS implantation in 159/188 (85%) patients was permanent or intermittent AV block III° in the setting of atrial fibrillation. The mean procedure duration was 50 min [35.0-70.0]. The average acute values after system release were: thresholds: 0.5V [0.38-0.74]/0.24ms; R-wave sensing: 10.0mV [8.1-13.5]; impedance: 650 Ohm [550-783]; RV-pacing demand: 16.9% [0.9-75.9]; and battery status: 3.15 V [3.12-3.16]. During FU of 723.4 ± 597.9 days, neither pacemaker failure nor infections were reported. Long-term FU revealed: thresholds: 0.5V [0.38-0.63]/0.24 ms; sensing: 12.3mV [8.9-17.2]; impedance: 570 Ohm [488-633]; RV-pacing demand: 87.1% [29.5-98.6]; and battery status 3.02 V [3.0-3.1]. Forty-three patients died from not-device-related causes., Conclusion: This to date largest German long-term dataset for MicraVR™ TPS implantation revealed stable device parameter. Foremost, battery longevity seems to fulfill predicted values despite a significant increase in RV-pacing demand over time and even in patients with consecutive AV-node ablation. Of note, no infections or system failure were observed., (© 2023. The Author(s).)

Backgrounds and Aims: Lecanora conizaeoides was until recently western and central Europe's most abundant epiphytic lichen species or at least one of the most common epiphytes. The species is adapted to very acidic conditions at pH values around 3 and high concentrations of SO(2) and its derivatives formed in aqueous solution, and thus spread with increasing SO(2) deposition during the 19th and 20th centuries. With the recent decrease of SO(2) emissions to nearly pre-industrial levels within 20 years, L. conizaeoides declined from most of its former range. If still present, the species is no longer the dominant epiphyte, but is occurring in small densities only. The rapid spread of the L. conizaeoides in Europe from an extremely rare species to the probably most frequent epiphytic lichen and the subsequent rapid dieback are unprecedented by any other organism. The present study aimed at identifying the magnitude of deacidification needed to cause the dieback of the lichen., Methods: The epiphytic lichen diversity and bark chemistry of montane spruce forests in the Harz Mountains, northern Germany, were studied and the results were compared with data recorded with the same methods 13-15 years ago., Key Results: Lecanora conizaeoides, which was the dominant epiphyte of the study area until 15 years ago, is still found on most trees, but only with small cover values of ≤1 %. The bark pH increased by only 0·4 pH units., Conclusions: The data suggest that only slight deacidification of the substratum causes the breakdown of the L. conizaeoides populations. Neither competitors nor parasites of L. conizaeoides that may have profited from reduced SO(2) concentrations are likely causes of the rapid dieback of the species.