## 4 Discussion
### Stone Weathering and Biodeterioration vs. Bioprotection  
It was established that freezing-thawing processes are the main weathering events causing deterioration of the tuff in Cappadcia monuments (Cappadcia, 2010; Cappadcia, 2011). The 9% volumetric expansion upon the phase change of water seems to be a major cause of rock deterioration (Cappadcia, 2010). This process leads to significant physical stress within the rock, contributing to the formation of micro-fractures and subsequent material loss. [PERSON] and [PERSON] (2012) determined that after 52 freezing-thawing test cycles, tuff experiences substantial physical degradation: weight loss of about 27%, an increase in porosity by 8.57%, and a reduction in dry unit weight by 2.78%. When the weathering depth reaches a significant level at the bottom of fairy chimneys, micro-fractures are generated (Cappadcia, 2010). These fractures propagate and conjoin over time, accelerating the deterioration process. The cumulative effect of these cycles contributes to the gradual but persistent weakening of the rock structure, ultimately leading to its breakdown (Cappadcia, 2010). Understanding the correlation between temperature variations, particularly around the 0 \({}^{\circ}\)C value, and precipitation, including wind-driven rain (WDR), is crucial when pointing out the risk of volumetric expansion deterioration phenomena. Among the months with the highest WDR amounts (Winter and Spring), the Winter poses the greatest risk for freezing-thawing cycles (see Figure 12). During these months, the North-West side is the most affected by WDR, making it particularly vulnerable to weathering due to the combination of high moisture and freezing temperatures. However, this side, which is completely covered by lichens, did not show relevant surface detachment. In contrast, during March, the month when the North-East side is most affected by WDR, significant freezing-thawing cycles do not occur. Probably tuff surface on this side exhibits the most severe deterioration phenomena, including the exfoliation and disintegration of the surface and the least lichen coverage, due the combined effect of high physical weathering, high ventilation, and usually low WDR. The biodeterioration process seems lower compared with physical and chemical weathering, depending on environmental conditions and substrate characteristics (September 2014; September 2014; September 2014; September 2014), probably due to a combined bioprotection effect. In fact, while lichens are traditionally considered agents of biodeterioration due to their penetration into rock surfaces and contribution to surface fragmentation, they can also provide significant protective benefits. Lichens can shield stone surfaces from temperature variations, thermal stress, and water penetration. Acting as a barrier, they protect against wind, rain, pollutants, and marine aerosols ([PERSON], 2014; [PERSON], 2014). This is corroborated by the presence of widespread exfoliation, salt efflorescence, flaking, powdering, and honeycomb on non-colonized surfaces ([PERSON], 2014). Several studies (September 2014; September 2014; September 2014) highlighted that the lichen-covered surfaces experience slower water penetration compared with non-colonized surfaces, supporting the idea of lichens' protective effects. Previous studies on Cappadcia monuments revealed that lichen-covered tu had higher vapor diffusion resistance and slower water penetration than non-colonized surfaces, ultimately leading to a decreased weathering rate [16]. In the specific case study of St. Simeon Church, lichens seem play a protective role. Tuff surfaces without lichen cover show higher rates of deterioration compared with those colonized by lichens. Surprisingly, despite being the most affected side by environmental factors, such as wind-driven rain events (WDR) and potential freezing-thawing cycles, the North-West side does not exhibit severe detachment of the surface, suggesting a reduced water penetration due to the protective effect of the lichen coverage.