2,561 research outputs found
Stable water isotope dataset of precipitation, groundwater, soil water, stemflow and throughfall water, and xylem water of Norway maple (Acer platanoides) and small-leaved lime (Tilia cordata) growing at different urban sites in the city of Freiburg, Germany
No full textTrees in urban ecosystems play a pivotal role in enhancing the climate resilience of cities through their ecohydrological processes, such as transpiration and interception, to mitigate the urban heat island effect and reduce the risk of flooding. However, the complex spatial heterogeneity in urbanized areas and the occurrence of extreme weather events, such as droughts, may disrupt ecohydrological dynamics of trees. In this study, we conducted an extensive field study on 25 urban trees growing in contrasting urban environments. Addressing the limited understanding of water source uptake dynamics of trees planted in complex urban ecosystems, we investigate the composition and temporal pattern of stable water isotopes of groundwater, urban soils, twig xylem water and precipitation to determine the proportional source water uptake over two vegetation periods. Bayesian mixing analyses with three potential sources, including young and old precipitation as well as groundwater, indicated that trees were mainly dependent on older precipitation events, occurred two to six months before the twig sampling events, while another mixing analysis, including groundwater and two soil layers, indicated soil water in 20-40 cm depth as the primary water source. Groundwater showed the lowest proportion in all mixing models variants. Despite some significant differences in the proportional uptake of tree water sources between study sites, the primary source remained consistent. The most significant contrast between sites was the reliance of trees in tree pits on soil water in 20-40 cm depth and older precipitation during drier periods. Our study generated a unique dataset on the soil-plant-atmosphere continuum within an urban ecosystem, which highlighted the dynamics of water uptake by urban trees. However, long-term investigations on different urban tree species are crucial to understand the mechanisms of tree water cycling, including influences of droughts and heat waves
Quantification of ecohydrological processes of urban trees
No full textAnthropogenic activities, such as the rapid expansion of impermeable surfaces in cities and the growth of urban populations, have major impacts on urban hydrology and meteorology. Compared to natural reference conditions, these activities reduce rainwater infiltration and groundwater recharge while runoff generation processes are enhanced, which increases the risk of both fluvial and pluvial flooding. Additionally, the reduced evapotranspiration processes and heightened solar radiation absorption by anthropogenic infrastructures such as buildings and streets, leading to higher urban air temperatures and greater evaporative demand. This intensifies the urban heat island effect. These human-induced changes in urban environments reduce the health, liveability, and safety of urban residents, making cities less resilient to extreme events like heatwaves and heavy rainfall.The utilisation of green infrastructure, such as urban trees, indicate a pivotal role in terms of its ecosystem services and is an essential urban management and adaptation tool. Urban trees regulate water infiltration into the soil, ensuring a higher available soil water content and facilitating transpiration. Ecohydrological processes such as interception, infiltration and transpiration reduce the peak and magnitude of stormwater runoff. In particular, the air cooling effect of transpiration contributes to mitigating the urban heat island effect and increasing the climate resilience of cities. However, the complex spatial heterogeneity within cities, the occurrence of extreme weather events such as droughts and heatwaves, and harsh growth conditions may disrupt the ecohydrological dynamics and vitality of urban trees.In this thesis, extensive in-situ field measurements and sampling campaigns were conducted over two growing seasons, 2021 and 2022, to investigate the main ecohydrological processes of Norway maple (Acer platanoides) and small-leaved lime (Tilia cordata) growing in different urban settings in the city of Freiburg, Germany. To consider site-specific differences, four different urban sites with various degrees of surface sealing underneath their crowns were chosen for both tree species. These sites included urban parks, parking lots, grass verges, and tree pits.The investigation of rainfall interception by eight trees per species was analysed across seventy-six recorded rainfall events in the vegetation period of 2021. Average interception values were higher for small-leaved lime (70.3 ± 6.6%) than for Norway maple (54.8 ± 10.3%), surpassing those in typical forested environments. The average interception loss of all recorded events was 2.6 ± 0.6 mm for Norway maple and 3.7 ± 0.3 mm for small-leaved lime. For both tree species, significant linear correlations were found between the relative interception and factors such as rainfall depths, the leaf area index (LAI), and the plant area index (adj. R2 > 0.45). Unlike Norway maple, small-leaved lime demonstrated significant relationships between several tree morphological parameters and interception (adj. R2 > 0.43).Furthermore, small-leaved lime exhibited higher average daily transpiration rates (1.8 ± 0.5 mm) compared to Norway maple (1.5 ± 0.5 mm). Notably, tree planting sites with larger impermeable surfaces beneath tree crowns experienced reduced transpiration rates (1.1 ± 0.3 mm) independent of the species, indicating the impact of surface sealing on root water uptake. Solar radiation emerged as the primary driver of day-to-day transpiration dynamics, followed closely by vapour pressure deficit and finally by soil water content. Additionally, tree morphological traits such as LAI and leaf area density, along with surface sealing, significantly influenced transpiration rates.Moreover, small-leaved lime exhibited a 5% greater reduction in daily transpiration during drought periods compared to Norway maple, which experienced a 34% decline in transpiration compared to non-drought periods. Among selected urban sites, tree pits with 90% surface sealing caused the mostIIsignificant drought-induced transpiration reduction for small-leaved lime (58%), and both species displayed the lowest transpiration to potential evapotranspiration ratio in these locations. Significant differences were observed in the diurnal sap velocity patterns for both species, and a notable relationship between soil water deficit and relative transpiration rates during drought periods was identified.Remarkably, LAI demonstrated a strong correlation with the sealing degree within the crown projection area, highlighting the interconnectedness between tree characteristics and urban conditions, which in turn affected both interception and transpiration processes, especially during drought periods.Bayesian mixing analyses, incorporating three potential sources—namely young and old precipitation as well as groundwater—indicated that trees primarily depended on older precipitation events occurring between two and six months prior to twig sampling events. Another mixing model approach including groundwater and two soil layers suggested that soil water in the 20-40 cm depth range served as the primary water source, while groundwater exhibited the lowest proportion in twig (xylem) water mixtures. Despite some significant differences in the proportional uptake of tree water sources between study sites, the primary source remained consistent over the entire study period. The most notable contrast between sites was observed in the reliance of trees planted in tree pits on soil water in the 20-40 cm depth range or on older precipitation during drier periods, respectively.Overall, a unique dataset on the soil-plant-atmosphere continuum in a complex urban ecosystem was generated for typical urban tree species in Central European cities. This thesis advanced the understanding of the interception process and hydrometeorologically-dependent transpiration dynamics by solitary trees in urban contexts and enabled the parameterization of key ecohydrological processes using measurable properties. Additionally, crucial insights into tree species' responses to drought-induced transpiration and the dynamics of water source uptake by urban trees across varied urban settings are provided. However, the necessity for long-term field measurements is emphasized, encompassing various meteorological conditions and extremes such as droughts and heatwaves, diverse tree species, and urban growing conditions, to comprehensively quantify tree ecohydrological process dynamics and assess their role in the urban water cycle
Evidence based leadership
No full textAuthor Markus PodduikinMasterarbeit Johannes Kepler Universität Linz 2024Arbeit gesperr
Improving the search for monitoring tools using recommender technology
No full textAuthor Markus Eisl BSc.Masterarbeit Universität Linz 2023Arbeit gesperr
Improving the search for monitoring tools using recommender technology
No full textAuthor Markus Eisl BSc.Masterarbeit Universität Linz 2023Arbeit gesperr
metal-organic framework 4H, 4H-octafluoroazobenezene perfluoroazobenzene
No full textauthor: Markus RödlKumulative Masterarbeit aus einem ArtikelMasterarbeit University of Innsbruck 2022Arbeit gesperr
metal-organic framework 4H, 4H-octafluoroazobenezene perfluoroazobenzene
No full textauthor: Markus RödlKumulative Masterarbeit aus einem ArtikelMasterarbeit University of Innsbruck 2022Arbeit gesperr
Strategi Pelayanan Lintas Budaya Berdasarkan Markus 4:1-34
No full textHarming & Katarina, Cross-cultural Service Strategy based on Mark 4: 1-34. The author conducted a study of the text of Mark 4: 1-34 using qualitative research literature study using the biblical hermeneutic principle. Based on the analysis of the text of Mark 4: 1-34 the authors find there are four cross-cultural service strategies namely by understanding local culture, using media. Harming & Katarina, Strategi Pelayanan Lintas budaya Berdasarkan Markus 4:1-34. Penulis melakukan penelitian terhadap teks Markus 4:1-34 dengan menggunakan penelitian kualitatif studi pustaka dengan menggunakan prinsip hermeneutik Alkitab. Berdasarkan analisis terhadap teks Markus 4:1-34 penulis menemukan ada empat strategi pelayanan lintas budaya yaitu dengan memahami budaya lokal, menggunakan media yang ada dalam budaya, memberdayakan potensi yang ada, dan menciptakan terobosan
Development of a Software Tool for Analyzing Experimental Data of a Recycling Machine
No full textAuthor DI Markus Kirchmayr, BScMasterarbeit Universität Linz 2022Arbeit nach Ablauf der Sperre auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
Machine-Learning-Based Photometric Stereo for Fracture Surface Reconstruction of Metal Samples
No full textAuthor Markus PrombergerMasterarbeit Johannes Kepler Universität Linz 2025Arbeit nach Ablauf der Sperre auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
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