Sacred Natural Sites are relevant for biodiversity conservation, as in the case of forest sites that, across centuries, developed old growth structures and are now crucial for the conservation of epiphytic lichens and other specialized forest organisms. In this study, we investigated the epiphytic lichen flora of a small forest patch included in the Majella National Park (Abruzzo), whose old growth features and naturalness reflect its long lasting spiritual role that perfectly fits with the concept of Sacred Natural Site. Results revealed that the “Bosco di Sant’Antonio” hosts a rich and interesting epiphytic lichen flora, thus indicating the potential of this Sacred Natural Site for lichen conservation. Fifty-six species were found including two species newly recorded in Abruzzo, two red-listed species, and the sensitive species Lobaria pulmonaria. This study corroborates the hypothesis that sacred forest sites are relevant for the conservation of specialized epiphytic lichens. In particular, in the Italian forest landscape where old-growth stands are practically absent, sacred forest sites may provide unique old-growth structures and buffer anthropogenic disturbance.

conservation, forest lichens, lichen red-list, Lobaria pulmonaria, old-growth stands

Sacred Natural Sites are relevant for biodiversity conservation (Avtzis et al. 2018; Frascaroli et al. 2016) since their spiritual value is intrinsically associated with the maintenance of inspiring natural habitats by non-intervention or non-intensive management. This is, for example, the case of several forest sites that are not exploited for timber production due to the presence of a small church, a shrine, or a crucifix. Across centuries, these forests are allowed to develop old-growth structures that are crucial for the conservation of several forest organisms, such as epiphytic lichens (Nascimbene et al. 2013a).

Epiphytic lichens are a species-rich component of the forest biota playing several ecological roles, thus contributing to forest functioning and underpinning relevant ecosystem services (Zedda and Rambold 2015). Their diversity patterns are strongly influenced by forest structure and dynamics that, in turn, are affected by forest management. In particular, forestry is among the main causes of species loss across European forests (Nascimbene et al. 2013b) due to the exploitation of old trees, short rotation cycles, excessive canopy cover, or excessive exposure to direct light in the final part of the rotation cycle. In contrast, their diversity is enhanced by increasing tree age, which especially benefits rare, threatened (red-listed), and late successional species (Ellis 2012). Old trees provide different and highly variable bark structure as well as other microhabitats such as rot holes, growth anomalies, and moss cover (e.g. Fritz and Heilmann-Clausen 2010). Large old trees also enhance the establishment of dispersal-limited species that have more time for colonization, higher surface availability, and more stable substrate conditions (Nascimbene et al. 2013b).

In this study, we investigated the epiphytic lichen flora of a small forest patch included in the Majella National Park, whose old-growth features (i.e., occurrence of old trees) and naturalness reflect its age-old spiritual role that perfectly fits with the concept of Sacred Natural Site.

Fifty-six species were found (Table 1), representing 17% of the known epiphytic lichen flora of Abruzzo. They include two species that were new records for this Region, namely Arthonia mediella and Gyalecta ulmi, the second of which is also a red-listed species together with Sclerophora pallida. An additional interesting species is Lobaria pulmonaria, occurring with a well-established, but clustered, population including several fertile thalli.

The checklist mainly includes crustose and large-lobed foliose lichens with chlorococcoid green algae as photobiont and sexually reproducing by ascospores. However, we found a high percentage of cyanolichens (17.9%) and vegetatively reproducing species (42.8%), representing about 28% and 20%, respectively of the species occurring at the Regional level.

The analysis of the ecological indicator values (Table 2) revealed that the epiphytic lichen flora of the “Bosco di Sant’Antonio” mainly includes sub-acidophytic-neutrophytic species related to mesic-shaded and humid-mesic conditions, and avoiding or tolerating moderate eutrophication.

Results reveal that the “Bosco di Sant’Antonio” hosts a rich and interesting epiphytic lichen flora, thus indicating the potential of this sacred natural site for lichen conservation. Actually, our field observations in several forest sites of the Majella National Park support the view that this small forest patch may represent a refuge for several lichen species that are virtually missing in the surrounding forest landscape. While for small-sized species (e.g. Sclerophora pallida) there could be a bias related to intrinsic species detectability, for large-sized species this observation could be reliable, as in the case of the large foliose lichen Lobaria pulmonaria whose population in the “Bosco di Sant’Antonio” seems to be unique to the Majella National Park. This species has suffered a general decline throughout Europe as a consequence of air pollution and intensive forest management and is currently red-listed in several European countries (Benesperi et al. 2018). In Italy, it is expected to strongly decline in the next decades due to reduced climatic suitability related to climate change that may exacerbate the effect of local impacts (Nascimbene et al. 2016). In the Majella National Park, the studied sacred forest site is crucial for the conservation of this sensitive and charismatic species, also able to ensure the conservation of co-occurring red-listed species (Nascimbene et al. 2013b).

The conservation importance of this site is further corroborated by 1) the high percentage of cyanolichens, and 2) vegetatively reproducing species that compose its lichen flora. Cyanolichens are a group of functionally relevant species (i.e., they are involved in atmospheric nitrogen fixation) sensitive to climate change and local anthropogenic disturbance that are dramatically declining across Europe, including Italy (Nascimbene et al. 2016). In many Italian regions, the occurrence of most species is only documented by records dating back more than a century ago (Nimis 2016; Nimis and Martellos 2017). Vegetative reproduction is a strategy that characterizes late successional communities (Nascimbene et al. 2017). This may reflect the fact that vegetative propagules are probably poorly adapted to bear harsh conditions typical of pioneer stages, while they meet more favorable conditions in old, more stable sites. The production of vegetative propagules enhances the local competitiveness of the species due to a rapid recruitment of new thalli. This is likely to result in a species-rich community that effectively saturates the available ecological niches.

The ecology of the species, as indicated by the values of the ecological indicators, reflects the main substrate and habitat features, with a high incidence of sub-acidophytic-neutrophytic species growing on beech bark in mesic-shaded and humid conditions. Interestingly, only a few species moderately tolerate eutrophication, probably reflecting a sporadic grazing activity. Our field observations in some forest patches nearby the sacred site revealed an intensive grazing activity that resulted in the establishment of a nitrogen-tolerant lichen flora, while most of the species inventoried in the “Bosco di Sant’Antonio” were almost absent. This situation further supports its important conservation status, likely related to its spiritual value.

This study corroborates the hypothesis that sacred forest sites may be relevant for epiphytic lichen conservation. In particular, in the Italian forest landscape where old-growth stands are scarce, such sites may provide unique old-growth structures and buffer anthropogenic disturbance. This would fit with the concept of ‘shadow network’ (Dudley et al. 2009) that considers Sacred Natural Sites as nodes of a non-official conservation network that may integrate the one based on protected areas. In this perspective, further sampling-based studies are required to confirm these promising speculations.

This floristic survey was financed by the Project “Indagine sulla biodiversita’ lichenica nel territorio del Parco Nazionale della Majella” (scientific collaboration between UNIBO-BiGeA and the administration of the Majella National Park) and by the project “Biodiversity and ecosystem services in Sacred Natural Sites (BIOESSaNS)” (PRIN 2015 2015P8524C, project coordinator Prof. A. Chiarucci; https://site.unibo.it/bioessans/it).

JN and AC conceived the idea; JN, VDC, LDM, PG, CL, CV performed the field work and species identification; FF, PZ, AC contributed expertise in the field of Sacred Natural Sites; JN prepared the first draft of the ms and all the authors contributed to the final version.