What can be done with de-sealed urban soil? A multidisciplinary case study in northern Germany

Within urban settings, soil sealing is one of the most degrading forms of anthropogenic alteration, affecting all pedosphere ecosystem services. To address this issue, an interdisciplinary study is presented in which physical, chemical, biological, and mechanical properties of soil sealed for 10 years were analyzed to evaluate the extent of anthropogenic impacts. Disturbed and undisturbed soil samples were collected from the edge and the center of a freshly de-sealed site, as well as from an adjacent green reference area, at depths of 0–5 cm, 15–20 cm and 40–50 cm. The analyses revealed an increase in soil pH from 6.0 to 6.4 in the reference profiles to 8.1–8.6 in the de-sealed soils. Electrical conductivity in the edge subsoil reached 341 µS cm −1 , compared to 31–53 µS cm −1 in the reference. Total nitrogen declined from 1.31 mg kg −1 in the reference topsoil to 0.17–0.44 mg kg −1 under sealed conditions, while C/N ratios increased, reaching 78 at the edge compared to 15 in the reference. Organic carbon decreased in the lower layers from 0.44 mg kg −1 (reference) to 0.03–1.03 mg kg −1 (center). Bacterial and fungal counts dropped from 6.6 × 10 5 CFU g −1 (reference) to 9–51 CFU g −1 , and from 8.2 × 10 4 CFU g −1 (edge) to 1–3 CFU g −1 (center), respectively. Bulk density increased in the de-sealed subsoil from 1.57 g cm −3 (reference) to 1.84 g cm −3 (center). Saturated hydraulic conductivity of the topsoil decreased from 1,157 (reference) to 543 cm d −1 (center). In the de-sealed subsoil field capacity decreased from 0.38 to 0.16 cm 3 cm −3 . X-ray computed tomography (CT) imaging revealed extensive fracture networks and debris-rich matrices that differed between sampling locations. The obtained data were used for modelling various scenarios aimed at restoring soil ecosystem services. Results show that lower water storage capacity in the de-sealed soil increases hydraulic stress, elevates percentage loss of conductivity (PLC), and may lead to drought-induced mortality under extreme conditions, while the reference soil supports higher transpiration and cooling potential. Modelling approach suggest that soil hydraulic properties critically constrain early-stage vegetation establishment in de-sealed urban environments and should be considered in restoration strategies. In-situ analysis revealed edge as transitional zone exhibiting characteristic gradients that may serve as predictive indicators of de-sealing succession trajectories.