https://hdl.handle.net/20.500.14178/908 2026-09-07T20:23:44Z 2026-09-07T20:23:44Z Pandey, Aayushi Kropáček, Jan https://hdl.handle.net/20.500.14178/3914 2026-09-04T01:00:27Z 2026-01-01T00:00:00Z

Modeling glacial lake bathymetry and water storage from UAV data in proximity to former Gornersee, Monte Rosa Massif, Western Alps Pandey, Aayushi; Kropáček, Jan Formation and sudden drainage of glacial lakes pose increasing hazards in high-mountain regions, threatening downstream communities, infrastructure and ecosystems. Accurate bathymetric reconstruction and lake volume estimation are crucial for flood modeling, hazard assessment, and monitoring climate-driven glacial lake dynamics. This study uses a recently drained lake at the margin of Gornergletscher, Monte Rosa Massif, Western Alps, to reconstruct its bathymetry and estimate its volume by combining a high-resolution digital elevation model (DEM) from low-cost uncrewed aerial vehicle (UAV) imagery with multispectral Sentinel-2 data. The UAV data were used to generate an orthomosaic and a high-resolution DEM of the empty lake basin. Lake extents corresponding to five filling stages, together with the DEM, enabled pixelwise depth estimation, yielding a mean lake depth for maximal filling of 21.94 m and an estimated corresponding water volume of 0.298 +/- 0.11 & times; 10(6) m3. Field observations indicated direct glacier contact and subglacial drainage through vertical conduits. Sentinel-2 also revealed smaller lakes in 2017 and 2018. Comparative analysis of climate variables from lake (2017, 2018 and 2022) and no-lake (2019-21) years highlighted higher April-June temperatures as the dominant factor controlling lake formation. This study demonstrates the value of integrating UAV three-dimensional (3-D) terrain modeling with satellite remote sensing for high-resolution glacial lake monitoring.

2026-01-01T00:00:00Z Tumajer, Jan Grudd, Hakan Kuželová, Hana Lange, Jelena Ana Treml, Václav https://hdl.handle.net/20.500.14178/3913 2026-09-04T01:00:23Z 2026-01-01T00:00:00Z

Frequency-dependent climate sensitivity of sub-daily radial growth of tree stems at the dry Arctic treeline Tumajer, Jan; Grudd, Hakan; Kuželová, Hana; Lange, Jelena Ana; Treml, Václav Radial growth of tree stems shows remarkable variability over the year but also within individual days. Understanding the frequency-dependent growth sensitivity, i.e., the shifting responses of wood formation to meteorological conditions between annual and daily temporal scales, is essential for predicting forest growth under future climates. However, this knowledge is limited for the cold Arctic margins of species distribution. To address this gap, we monitored intra-annual and sub-daily stem radius variation of Pinus sylvestris L. for 2 years using xylogenesis microsampling and dendrometers at the cold-dry treeline beyond the Arctic Circle near Abisko, Northern Sweden. Using linear statistics, cell growth modeling and wavelet transformation, we separated individual frequencies of stem oscillations, ranked their statistical importance and identified immediate and lagged meteorological drivers of stem radius increment. Radial growth of tree stems showed overlapping oscillations at annual and daily frequencies. On an annual scale, radial growth and cell production peaked during the warm summer months. However, within the summer, stem radius increment accelerated toward the cool, moist midnight hours and ceased during the day as the temperature and solar altitude increased. Accordingly, we identified two growth-optimal intervals with peak growth rates, jointly accounting for 68% of the total growth: (i) an air temperature of 8-16 degrees C with a vapor pressure deficit (VPD) of <0.2 kPa, and (ii) an air temperature of 4-16 degrees C and VPD = 0 kPa. While correlations between peak-summer growth rates and immediate temperature and VPD were negative, these correlations switched to positive when considering lagged meteorological variables preceding growth by up to 4 days. Our results suggest frequency-dependent shifts and lagged responses of radial growth to meteorological variables at the Arctic treeline, particularly for air temperature and humidity. We propose that the midday growth reduction during summer may help explain non-linear responses of northern boreal forests to recent climate warming.

2026-01-01T00:00:00Z Dhyani, Rupesh Martin-Benito, Dario Verschuren, Louis Matskovsky, Vladimir van den Bulcke, Jan Dogan, Mehmet Kvaratskhelia, Revaz Kose, Nesibe Guner, Huseyin Tuncay Schneider, Lea https://hdl.handle.net/20.500.14178/3911 2026-09-02T01:00:21Z 2026-01-01T00:00:00Z

Limited early-industrial warming and strong volcanic imprints in the Caucasus: the first temperature reconstruction based on maximum latewood density Dhyani, Rupesh; Martin-Benito, Dario; Verschuren, Louis; Matskovsky, Vladimir; van den Bulcke, Jan; Dogan, Mehmet; Kvaratskhelia, Revaz; Kose, Nesibe; Guner, Huseyin Tuncay; Schneider, Lea The Caucasus occupies a unique climatic region influenced by European, Mediterranean, and Asian circulation systems, yet it remains underrepresented in tree ring-based Northern Hemisphere temperature proxy networks. Here, we present the first summer temperature reconstruction for the Caucasus region based on maximum latewood density (MXD). We used X-ray micro-computed tomography of tree-ring samples from Pinus sylvestris growing at the upper tree line in the Lesser Caucasus and an ensemble nested regression approach to develop a robust 326 year-long June-September temperature reconstruction (1697-2022). The record explains - regionally unprecedented - 72 % of temperature variance during the instrumental period (1901-2022) and captures distinct interannual and multi-decadal variability including pronounced warming since the 1990s and a strong imprint of major volcanic eruptions. Temperatures in the second half of the 19th century were not significantly colder in the Caucasus than in the second half of the 20th century. The reconstruction highlights the exceptional magnitude and pace of 21st century warming in the region, which is without analogue at least in the past three centuries. Comparison with regional and large-scale temperature reconstructions reveals strong agreement within the Caucasus but negative correlations with Central Europe, indicating distinct temperature variability patterns across Europe and western Asia. Future work should focus on the climate dynamics behind this dipole and the extension of temperature-sensitive tree-ring records in the region.

2026-01-01T00:00:00Z Piataková, Adrianna Julia Šmahel, Michal https://hdl.handle.net/20.500.14178/3910 2026-09-02T01:00:27Z 2026-01-01T00:00:00Z

Macrophages in tumors with downregulated MHC-I expression: emerging therapeutic opportunities and translational challenges Piataková, Adrianna Julia; Šmahel, Michal Tumor-associated macrophages (TAMs) are the dominant component of the tumor microenvironment and exhibit remarkable phenotypic plasticity and heterogeneity that extends beyond the classical M1/M2 polarization, as revealed by single-cell transcriptomics across multiple cancer types. Downregulation of major histocompatibility complex class I (MHC-I) on tumor cells is a common immune evasion strategy that profoundly shapes TAM composition and function. Conversely, TAMs reciprocally modulate tumor MHC-I expression. This review provides an overview of the verified and hypothetical mechanisms of bidirectional regulatory interactions between MHC-I on tumor cells and TAMs. Since these interactions likely differ between tumors with reversible and irreversible MHC-I downregulation, their potential significance in tumor immunotherapy should be assessed separately for each MHC-I reduction mechanism. Bidirectional regulatory interactions between tumor-associated macrophages (TAMs) and major histocompatibility complex class I (MHC-I) molecules on tumor cells shape the tumor microenvironment and immunotherapy responses. MHC-I downregulation alters TAM composition and function, including phagocytosis. Repolarizing TAMs and activating phagocytosis represent promising therapeutic strategies for "cold" tumors with MHC-I deficiency, but translational challenges require distinguishing MHC-I loss mechanisms.

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