Dataset for: Urban lichenometry: growth of Circinaria contorta on city sidewalks

Lichenometry, a dating method that relies on the largest lichen to infer the age of a surface, is widely used, due to its simplicity and affordability. However, several of the processes underlying the basic assumptions are assumed to be constant, while in reality they are climate-dependent, particularly those concerning colonisation, mortality, and thallus growth rates. This limits the comparability of lichenometric studies in different climates. Therefore, a better understanding of the environmental influence on lichen growth is required. Urban environments, with many homogeneous dated surfaces, can offer a unique opportunity to study lichen growth. To get a better understanding of urban lichen growth patterns, we investigated the largest C. contorta thalli on sidewalks of varying ages in three temperate cities. Results suggest a sigmoidal growth pattern, reaching a peak radial growth rate of 1.68 mm y⁻¹, similar to other temperate crustose lichens. Variation within and between cities is substantial and only partially explained by shade and sidewalk area. However a rough estimation of concrete pavement age can be inferred from the largest thallus diameter.