H091-0007
Stable isotope transformations in the critical zone of contrasting urban green spaces
Thursday, 10 December 2020
Poster
Christian Marx1,2, Chris Soulsby3,4, Reinhard Hinkelmann1 and Doerthe Tetzlaff2,5, (1)Technische Universität Berlin, Berlin, Germany, (2)Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, (3)University of Aberdeen, Aberdeen, United Kingdom, (4)Technische Universität Berlin, Institute of Civil Engineering, Berlin, Germany, (5)Humboldt University of Berlin, Berlin, Germany
Abstract:
Urban greenspaces play a fundamental role as a “green lung” in urban areas providing numerous important ecosystem services. They often act as crucial natural groundwater recharge zones in many cities. Out understanding of ecohydrological processes at the urban atmosphere-soil interface in complex urban green spaces is still quite limited. Here, we aimed to quantify the partitioning between “green” and “blue” water fluxes in contrasting urban greenspaces under different vegetation cover. We applied the direct- water vapour equilibrium method to determine soil water stable isotopes sampled in three different greenspaces with seven representative land covers (ranging from grassland to woodland), within Berlin, Germany. We also conducted extensive surface soil moisture monitoring in order to understand the spatial and temporal variability of water storage within the critical zone of urban greenspaces.
Contrasting sites show different degrees of isotopic fractionation due to variation in evaporation dynamics over time and space, implicating distinct storage and mixing processes which reflects contrasting ecohydrological partitioning driven by land cover. Clear seasonality in soil moisture content and isotopic fractionation during the growing season can be followed in each of the investigated greenspaces, with different amplitudes of variation. Whilst forest and tree-cover sites were generally drier than grassland sites, evaporative fractionation differences (indexed by lc-excess) were complex and also reflected the density of vegetation ground cover. Fieldwork and data evaluation will be continued during 2020. This research provides insights into spatially distributed ecohydrologic fluxes in the urban critical zone to understand how different vegetation and soil characteristics affect local partitioning. This provides a quantitative framework for future tracer-aided modelling and an evidence base for management of urban green spaces.
