Lichen-mediated limestone weathering: contrasting biomechanical and biochemical contributions in subtropical and highland regions

Abstract Lichens play an important role in rock alteration across diverse terrestrial environments, yet the relative contributions of biomechanical and biochemical processes under different climatic conditions are still poorly constrained. Here, we investigated interactions between dominant lichen species and limestone in two climatically contrasting regions of China: the warm, humid subtropical monsoon climate of Jiande and the cold, arid highland environment of the Karakoram Range. In Jiande, hydration-dehydration cycles of epilithic thalli promote pervasive peeling and detachment of limestone fragments, whereas biochemical effects are weak and localised, being mainly expressed as deeply penetrating hyphal perforation networks. The net effect of lichen colonisation in this region appears to be species-specific, ranging from bioprotection to biodeterioration. In the Karakoram, lichens exert strong biomechanical effects by driving dense hyphal clusters into the porous substrate and wedging off limestone fragments. Biochemical processes are also strongly expressed through the dissolution of both limestone and aeolian minerals by oxalic acid and, potentially, carbonic acid, resulting in calcium oxalate formation, marked elemental redistribution, and net biodeterioration. Together, these results reveal species- and climate-associated patterns of lichen−limestone interactions and provide insights into the management of lichen colonisation on stone heritage in different climatic regions.