Combined Application of Multiple Global Change Factors Negatively Influences Key Soil Processes across an Urban Gradient in Berlin, Germany

Urbanization is a growing phenomenon affecting soils worldwide. Urban centers have been highlighted as hotspots for global change factors due to heightened anthropogenic activity. However, few studies have investigated the multifaceted impacts of global change factors (GCFs) acting in concert with urban soils. Thus, the objective of this study was to add GCFs in different combinations (0, 1, 2, 5, and 8 simultaneously) in three high-urbanity and three low-urbanity soils in Berlin and to evaluate their effects on soil parameters and functions. We hypothesized four potential outcomes of soil process responses to GCF exposure, Site-Specific Resistance, General Susceptibility, Low-Urbanity Resistance, and High-Urbanity Resistance. We provide evidence for the negative impacts of individual and multiple GCF application on litter decomposition, water repellency, and water-stable aggregates. Additionally, we highlight the General Susceptibility of litter decomposition to GCF exposure regardless of urbanity, as well as the Low-Urbanity Resistance of water repellency and High-Urbanity Resistance of water-stable aggregates under increased exposure to GCFs. This study expands on evidence of the growing threat of global change factors in urban settings and highlights some potential consequences regarding soil function.