**2. Materials and Methods**

We analyzed lichen diversity data collected within a long-term monitoring project focused on old-growth forests of The Cilento, Vallo di Diano e Alburni National Park, in Southern Italy (see the results here: [21–26]).

#### *2.1. Study Area*

The Cilento, Vallo di Diano e Alburni National Park extends over 181,000 ha, stretching between the Tyrrhenian coast and the margin of the Lucania mountains, in the Campania Region (southern Italy). This study was carried out in the interior forest habitats, from

300 to 1696 m, in a survey area of 30 × 42 km (Figure 2). The hilly substrates mainly develop on flysch formations; the inner mountains are carbonate massifs predominantly constituted by carbonate and dolostone [27]. Native forests are mostly represented by turkey oak (*Quercus cerris* L.) woodlands of the hilly and sub-montane belts (from 450 to 850 m in altitude), mesophilous mixed forests dominated by turkey oak mostly on the north-facing slopes (between 800 and 1000 m in altitude), and beech (*Fagus sylvatica* L.) woodlands (thermophilous and microthermal coenoses) in upland areas. Chestnut (*Castanea sativa* Mill.) coppices and holm oak (*Quercus ilex* L.) woods are less common. In this area, bioclimatic characteristics range from Mediterranean to temperate with a cooler and more humid climate, and inland areas are usually subject to a temperature lower than 10 ◦C for three months per year. Rainfall increases along with altitude from 730 to 1700 mm year<sup>−</sup>1.

#### *2.2. Sampling Design*

Thirty-six plots (50 × 50 m) were randomly selected, taking into account structural attributes, "old-growths", and forest types, in proportion to their area within the park (Figure 2). They represented a sub-sample of the 132 sites investigated during a preliminary extensive survey on forest structural attributes (systematic survey, grid dimension 500 m; see [28]). The selected plots were classified as old-growth (OG) or non-old growth (NOG) forests according to their structural attributes. In particular, OG stands were considered to be structurally more heterogeneous than younger ones in relation to the following criteria: (1) the presence of OG individual trees (individuals with DBH >50 cm); (2) weak or no human disturbance; (3) multi-layered canopy; (4) large volumes of standing and fallen deadwood; and (5) decaying ancient and veteran trees (standing dead trees). OG forest sites significantly differed (Wilcoxon test, *p* < 0.05) from NOG forests with regard to higher tree circumference (median: 113 vs. 72 cm), number of diameter classes (median: 11 vs. 9), and volume of fallen deadwood (median: 1.394 vs. 0.0 vol ha−1). The other structural variables were similar between the two forest types (Table 1).

The sampling plots represented overall five forest types as follows: (1) beech woodlands (10 NOG, 7 OG plots); (2) turkey oak woodlands (7 NOG, 4 OG plots); (3) mixed broadleaf forests (2 NOG, 2 OG plots); (4) chestnuts woods (2 NOG plots); and (5) holm oak woods (2 OG plots). The dominant tree species of each forest type were considered as tree substrate for lichen sampling. In each plot, three sampling trees were considered within one randomly selected circular sub-plot (7-m radius). In mixed broadleaf forests we sampled different tree species (*Alnus cordata* (Loisel.) Desf., *Quercus pubescens* Willd., *Q. cerris*, and *C. sativa*). OG and NOG stands showed moderate differences in the proportion of the sampled tree species composition, with a predominance of beech and turkey oak, as well as seven less frequent tree species (see Table S1).


**Table 1.** Descriptive statistics of the structural variables included in the models. Results of the Wilcoxon test performed for the two forest types are also reported. n.s.: not significant (*p* > 0.05).

**Figure 2.** Study area: Cilento National Park (South Italy), with 36 sampling plots.
