University of Hradec Králové

We study axial gravitational perturbations of the neutral regular black hole generated by a non-local, T-duality-inspired zero-point length and the associated gravitational self-energy. In this geometry, the usual point source is replaced by a regular core, and the zero-point length controls the departure from the Schwarzschild limit. We compute the fundamental quasinormal modes and several overtones with high-order WKB–Padé methods, and we check the dominant mode with a direct time-domain evolution. When the zero-point length is turned on, the real parts of the ADM-scaled frequencies increase for the gravitational modes with ℓ=2,3,4, so the ringdown oscillates faster than in the Schwarzschild limit. The damping rates change more mildly: they first grow slightly and then decrease near the largest deformation values considered here. This behavior is consistent with the effective potential, whose barrier becomes higher as the deformation parameter increases. We also compute the corresponding excitation factors and find that their magnitudes vary much less strongly than the quasinormal frequencies.

We analyze quasinormal modes, grey-body factors, and absorption cross-sections of a massive scalar field in the background of a Schwarzschild black hole surrounded by a Hernquist dark-matter halo. The quasinormal spectrum is obtained through the higher-order WKB method and verified by time-domain evolution, showing consistent results. The field mass increases the oscillation frequency and reduces the damping rate, producing longer-lived modes, while variations in the halo parameters lead to moderate shifts in the spectrum. The grey-body factors reveal a suppression of low-frequency transmission and a displacement of their main features toward higher frequencies, resulting in a corresponding shift in the absorption cross-section.

Regional chronologies of landslide movements are a powerful tool for determining landslide hazard or analyzing potential triggers. This study has compiled a regional chronology of landslide reactivations through tree-ring dating of 12 landslides using data from 366 disturbed common spruce (Picea abies (L.) Karst.) individuals and three other sub-regional landslide chronologies from the study region. The study area is the eastern margin of the Bohemian Cretaceous Basin, a landslide-prone area in Central Europe. The dating detected 20 landslide reactivations in 16 different event years during the last ca 70 years. The frequency of identified growth disturbances and their structure, including their contribution to the reconstructed landslide events, clearly indicates limited slide activity and significant creep activity. Comparing the timing of slide events within the constructed sub-chronology indicates limited synchronicity of these events; however, comparison with other slide event chronologies suggests this synchronicity has increased significantly.

Temporal studies of insect assemblages provide valuable insights into the mechanisms through which communities differ across observation periods, especially in dynamic urban environments where certain insects find refuge. The aim of this study was to describe the temporal variations in pollinator assemblages in an urban context. We studied two insect taxa (i.e., day-active butterflies and flower-visiting beetles) across three periods in Pardubice, Czech Republic. Butterfly assemblages shifted toward species poor communities with relatively high numbers of generalists, whereas beetle assemblages appeared to be increasingly stable and, in some cases, showed persisting or appearing specialists. Our results suggest that urban environments can support different insect groups, albeit unequally. These findings highlight the need to consider urban habitats as potentially valuable for insect conservation while recognizing the increasing influences of built-up areas and the limitations of short-term temporal datasets. Effective urban pollinator conservation requires taxon-specific management, specifically transitioning to mosaic mowing regimes to protect declining butterfly specialists and actively retaining dead wood in parks to support resilient saproxylic beetles. Furthermore, protecting existing urban green spaces from further densification is crucial for maintaining these habitats and overall local biodiversity

Abstract Background Urban trees play a vital role in supporting biodiversity, enhancing human well-being, and promoting climate resilience. However, they are increasingly threatened by invasive insect pests. These pests belong to different feeding guilds, such as leaf-miners and sap-suckers, which may respond differently to the tree spatial arrangement and health of trees. Understanding how specific strategies of these pest groups interact with tree spatial arrangement, tree health, tree size, levels of defoliation, and the proportion of neighboring conspecific trees is crucial for explaining how infestations develop in urban areas. This study investigated how these factors influence infestations by three invasive pests: the horse-chestnut leaf miner (Cameraria ohridella), the plane leaf miner (Phyllonorycter platani), and the sycamore lace bug (Corythucha ciliata). Results Infestation intensity increased across all species as summer progressed (p < 0.001 for all species). C. ohridella reached the highest levels on solitary horse chestnuts, while P. platani was more abundant on plane trees growing in stands or groups. Proximity to conspecific trees reduced C. ohridella infestation, whereas healthier plane trees exhibited lower C. ciliata abundance. Tree size had no consistent effect, and defoliation did not reduce infestation in any species, despite significantly higher defoliation in horse chestnut compared to plane trees (p = 0.002). Leaf-mining and sap-sucking guilds differed in their spatial responses. Conclusions Fine-scale tree spatial arrangement and host condition are associated with variation in invasive pest dynamics in urban environments. Guild-specific differences in spatial responses and the finding that defoliation did not reduce infestation highlight the importance of local tree context for understanding infestation patterns of multivoltine pests. These insights may support the design of more resilient urban plantings, particularly through strategic arrangement of host trees and maintaining host vitality. Graphical abstract