In-situ measurements of stable water isotopes in soils and plants to quantify ecohydrological fluxes in an urban setting
Abstract
Understanding the ecohydrological fluxes in the critical zone is crucial for an efficient water management. However, these fluxes are usually difficult to observe without disturbances and at a high temporal resolution. Now, in-situ measurements of stable water isotopes via cavity ring down spectroscopy provide promising means for high-resolution field experiments over longer time periods. Still, such measurements are extremely limited in urban settings.
We conducted in-situ measurements at an urban site in the City of Berlin, the capital of Germany. Adjacent to the largest lake in the city, the Lake Müggelsee, which is connected to a shallow ground water aquifer, we quantified water fluxes in soil and trees during the growing period of 2020. Measured data include time series of stable water isotopes in precipitation, groundwater, soil and plant water, soil moisture, soil and air temperature, sap flux, stem-size variation, and eddy covariance. This integrated data set was used to investigate the ecohydrological fluxes of the soil-plant-atmosphere continuum in an urban setting. Isotopic measurements were conducted in two soil profiles and two willow trees at 2-hourly data resolution. Precipitation events resulted in heterogeneous responses in soil moisture and isotopic signatures of soil and plant water. Largest dynamics of the isotopic composition were observed in the top 20 cm of the soil. More negative soil water isotopic signals reflected the composition of winter precipitation. The top soil corresponded to younger, more enriched precipitation of the summer period and showed a strong evaporative signal. Preliminary results suggest that xylem isotopes reflect the spatially and temporal integrated signal of the dynamic top soil water but being less variable, a mixed uptake of shallow soil waters and lake water is plausible. Our findings improve the interdisciplinary perspective on critical zone processes offering a high-resolution perspective of urban soil water dynamics and corresponding tree water use dynamics during different seasons.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH091.0001L
- Keywords:
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- 0454 Isotopic composition and chemistry;
- BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1875 Vadose zone;
- HYDROLOGY