Urban green spaces are highly valuable in supporting the climate and infrastructure of cities through rainwater retention, evaporative cooling and shading (Gunawardena et al., 2017). Hence, understanding the complex interactions of water flux partitioning of incoming precipitation into “green” (i.e. evaporation and transpiration) and “blue” (surface runoff and groundwater recharge) water fluxes through urban vegetation is important to improve urban ecosystems functioning. There is still a lack of knowledge of spatial variability in evaporation and transpiration from urban areas and crucially, what influences this water flux partitioning (Gillefalk et al., 2021 & 2022; Marx et al., 2022).
The naturally occurring stable isotopes of water provide unique fingerprints of a water's origin, as the ratio of heavy to light isotopes is affected by various fractionating processes in the water cycle depicting the flow paths and age of the existing water. Previous research suggests that using stable isotope examinations in urban settings can reveal information about human influences on the hydrological cycle (Ehleringer, et al., 2016; Kuhlemann et al., 2021), as well as changing stream water ages and runoff generating processes (Kuhlemann et al., 2020 & 2021; Marx et al., 2021; Soulsby, et al., 2014). Especially valuable are long-term data sets, which are sampled along different streams throughout a city (Kuhlemann et al., 2022). Furthermore, hydrological models on urban rivers systems can be improved through tracer incorporation (Smith et al., 2023).
Isotopic signatures of atmospheric water vapour are indicators for the relevant evaporation and transpiration processes of green and blue spaces (Braden-Behrens, et al., 2020; Rothfuss et al., 2021) and are rarely studied within the urban surface boundary layer, e.g. within canopy elevation profiles. Those plant-atmosphere interfaces give insights on evapotranspiration partitioning and their impact on atmospheric vapour and consequently on the whole soil-plant-atmosphere continuum (Tetzlaff et al., 2021).
New technological developments allow now stable isotopes sampling and analysis at high temporal resolutions in-situ. The emergence of improved laser spectroscopy technology aids high-frequency capture of data (>1 second resolution) at lower analytical costs and advancing well-established destructive sampling methods (Herbstritt, et al., 2021). This increases our ability to fully unravel vegetation isotope dynamics in time (diurnal cycles) and scale (canopy profile evapotransipration) (Braden-Behrens et al., 2019; Smith et al., 2022). In-situ measurements of stable isotopes in atmospheric water vapour promote understanding the water cycle and helping to plan for climate change (Gao, et al., 2019), e.g. high frequency canopy scale isotope measurements demonstrate necessary insights on the behaviour of kinetic fractionation at the leaf versus canopy scales (Griffis, 2013).
This project aims to gain an improved understanding of the role of “green” and “blue” water flux partitioning at the urban surface boundary layer as well as isotopic dynamics in surface waters to fill the gap in understanding urban influences on water partitioning and isotopic fractionation, particularly evapotranspiration processes.
WP 1) 2021 proof of concept: High resolution in-situ atmospheric vapour dynamics under contrasting urban vegetation
WP 2) Entire Growing season 2022: High resolution in-situ atmospheric vapour dynamics under contrasting urban vegetation
WP 3) Surface water tracer dynamics in urban rivers
WP 4) Seasonal and spatial dynamics in eDNA as tracers in major urban rivers
Bearbeitung | Ann-Marie Ring | ||
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Betreuung | Prof. Dr. rer. nat. Dörthe Tetzlaff (IGB) | Prof. Dr. Chris Soulsby | Prof. Dr. rer. forest. Birgit Kleinschmit (TUB) |
Kollaborationen | W5, W6 |