Monitoring lichen recolonization on a restored calcareous statue

Monitoring lichens on monuments can have different purposes, one of which is monitoring the effectiveness of restoration. In the present work, lichen recolonization on a calcareous statue was monitored for evaluating the long-term effectiveness of restoration in preventing new biological growth. Species richness and composition of lichen communities from three surveys (one pre-restoration and two post-restoration) covering a twelve years period, are compared. The long-term effectiveness of the restoration of the statue was low, and even the use of water repellents failed in avoiding lichen recolonization. The short durability of the treatment applied to the statue was also confirmed by the recolonization pattern which seemed more related to the geometry of the statue than to the hydrorepellence of its surface. Recolonization involved lichen communities which differed from those covering the statue before restoration. Some species were significantly associated with each step of the succession, as well as to pre-restoration conditions. The pre-restoration lichen community was more differentiated across the statue, indicating a complex "Statue Ecosystem" that is perhaps more typical of a later successional stage. On the contrary, only a few communities dominated by a few species were involved in the recolonization. The management of stoneworks exposed in the parks of villas could be more effective focusing on maintenance than on repeated cleaning or restoration, whose effects are hindered by practical difficulties in preventing the causes of biological growth. If restorations are not going to be maintained, it would be better to retain a more historic, diverse, and complex lichen community than a simplified community of "weedy" lichens that quickly cover almost the same area as the pre-restoration community did. With this perspective, in the environmental and artistic context of these parks, biodiversity should be included in the concept of the historic and artistic value of the artworks. © 2008 Elsevier B.V. All rights reserved