Environmental Factors Influence Lichen Colonization and the Biodeterioration of Brick Carvings on Roof Ridges of Historic Buildings in Luoyang, China

Lichens that inhabit the roofs of historic buildings create a unique ecosystem. Comprehending the mechanisms underlying lichen colonization and the associated biodegradation within these structures is essential for formulating effective conservation strategies for historic buildings. Here, the microbial communities of lichens on the roofs of 10 historic buildings in Luoyang and nine surrounding counties were investigated via visual assessments and molecular biological analyses. The diversity of lichen species and their biological degradation effects on brick carvings on roof ridges were examined. The findings indicate that both the matrix characteristics of brick carvings and the climatic conditions in Luoyang facilitate the aggregation of lichen communities within these architectural features. Molecular biological tests revealed that Cyanobacteria, Bacillus, Chlorococcus, and Micromonosporaceae were among the most frequently detected bacterial taxa associated with lichens. The fungal associates included Cladosporium and Aspergillus. The infiltration patterns exhibited by certain lichen mycelia correlated with the structural properties at the interface between lichens and brick carvings, allowing mycelial penetration into the interior of these bricks. Additionally, guano not only serves as an organic nutrient source for microbial proliferation but also is a transmission medium for lichen-associated microorganisms residing on roof brick carvings. Whilst there are slight variations in microbial composition among lichens found in mountains and hilly areas around Luoyang, their colonization behaviors and degradation patterns are similar to those observed in analogous communities across different microclimate zones. The results offer a robust theoretical foundation for mitigating lichen-induced bioerosion in the historical buildings of Luoyang and serve as a valuable reference for the sustainable preservation of cultural heritage.