Assessing the deteriogenic vascular flora of castles and towers in Campania, Italy

Abstract

Biodeterioration is defined as the alteration of stone monuments, wall paintings, wood, paper, vegetal/animal fibers, and parchment artworks, caused by the combined action of physical and chemical factors produced by living organisms colonizing these substrates. The present study examines the role of vascular plants in the biodeterioration of castles and towers in Campania (southern Italy), analysing their relationships with building materials (substrates), exposure, distance from the sea, and elevation. The impact of plant colonization was assessed using the Hazard Index (HI), revealing substrate as the most influential factor both for species diversity and biodeterioration risk. Phanerophytes, known as the most aggressive biodeteriogens, decreased with increasing elevation, despite the greater presence of surrounding wooded areas. This pattern is likely related to the higher occurrence of limestone structures at inland and higher-altitude sites, which are less susceptible to colonization. Finally, distance from the sea and elevation showed no consistent effects on HI, although intermediate ranges exhibited lower HI values, possibly reflecting better maintenance practices at these sites. These findings underscore the need for site-specific conservation strategies that consider substrate vulnerability, such as the high bioreceptivity of tuff and the selective colonization of compact materials like piperno by Capparis spinosa, as well as the role of maintenance practices. The lower Hazard Index values observed in coastal and low-elevation sites suggest that regular interventions are effective in limiting plant-induced deterioration.