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Urbanization is causing soil sealing and ecosystem fragmentation, affecting soil health, biodiversity, and carbon storage potential. While green infrastructure is being promoted to address these challenges, small-scale habitats such as urban crevice soils (UCSs), referred to as soils in the gaps between concrete and asphalt surfaces in heavily urbanized areas, remain overlooked. The aim of this study was to determine whether UCSs are advantageous ecological units that sustain microbiological life and perform ecosystem services. This study quantified soil heterotrophic respiration, microbial biomass carbon (MBC) and nitrogen (MBN), soil organic carbon (SOC) and inorganic carbon (SIC), and total nitrogen (TN) in UCSs (with and without plants), nearby roadside soils, and soils from a switchgrass cropland in an urban farm within the Nashville metropolitan area in Tennessee, USA. On average, UCSs exhibited up to 436.2 %, 59.4 %, 217.6 %, and 266.9 % higher SOC, MBC, MBN, and C/N ratio compared to roadside and switchgrass soils, respectively. UCSs with plants have the highest microbial biomass, highlighting the synergistic role of plant presence in enhancing microbial function. These findings challenge the belief that urban soils are universally degraded and biologically inert, and regard UCSs as dispersed, small-scale contributors to urban ecosystem services. UCSs could serve as scalable, low-cost nature-based solutions that support resilient and sustainable cities amid rapid urbanization and environmental stress. Future studies should evaluate the ecological potential of UCSs as microhabitats for microbial biodiversity conservation, carbon storage, and ecosystem service delivery across various cities of different scales. 

Rapid urbanization leads to soil degradation, threatens the ecological benefits of urban soils and vegetation, and deteriorates the urban microenvironment to address climate resilience, pollution, soil degradation, and biodiversity loss. We reviewed the one-century-long history, origins, classification, and characteristics of urban anthropogenic soils (UAS) while emphasizing rarely studied and untapped potential of the crevice soil, plant, and abiotic conditions in the designated cracks of concrete materials of urban roadside. The long-overlooked crevice soils share features with UAS, such as being shallow, heterogeneous, and existing under harsh environmental conditions. Our urban crevice studies were conducted in the Nashville metropolitan area in Tennessee, USA. We collected soil samples from crevices with and without plants, nearby roadsides, and one switchgrass cropland in an urban farm. A total of 34 different plant species growing in crevices were identified, and only 12 species are native to the area, suggesting the dominance of non-native species in crevice soils. Regardless of the presence of plants, the crevice soils showed significantly higher temperature, pH, electrical conductivity, and a lower moisture content than roadside soils and switchgrass soils. The crevice micro-environment thus preserved precious soil resources, promoted urban biodiversity, and inspired innovative strategies for future sustainable urban design. Our ongoing efforts further examine heavy metals, organic and inorganic pollutants, and microbial composition, activity, and function in crevice soils and their counterparts in the urban environment.