- Author
- Deborah Isocrono
- Co-authors
- Silvia Ongaro , Paolo Gonthier
- Abstract
-
European ash (Fraxinus excelsior) forests are typical of steep slopes at low altitudes in the Western Alps, and they have different ecological functions representing an irreplaceable habitat for some groups of organisms. Previous studies showed that Fraxinus can host a rich ash-associated lichen community (hundreds of lichens, many of them threatened or rare in several European countries). Moreover, some species seem ecologically exclusively bound to ash populations. Since the 1990s, ash dieback, caused by the non-native pathogenic fungus Hymenoscyphus fraxineus, spread all over Europe severely impacting F. excelsior. Symptoms of the disease include diffused necrosis on branches and leaves, crown desiccation, development of cankers, and death of trees. It is known that outbreaks and tree death can lead, in the worst scenarios, to local extinctions of lichens and other sensitive organisms. Lichen species richness and abundance have been studied in ash forests displaying different degrees of disease severity in the Aosta Valley (NW Italy). Ash trees were measured (height, diameter at breast height), classified for symptom severity (crown desiccation, number of lesions), and inspected for the presence of epiphytic lichens at breast height and at the base of the stem. Preliminary results show that lichen species richness and abundance seem not linearly related with symptoms severity. In particular, light availability caused by high defoliation rate and occurrence of deadwood in various stages of decomposition lead to a complexity of microhabitats that seems to improve lichen populations in terms of abundance. Another synergistic factor to consider is the availability of a “source” community in the surroundings: when the main host populations decline, other tree species may serve as alternative hosts for epiphytic organisms. Hence, mixed ash forests could better support lichen biodiversity than pure forests. Co-funding: INTERREG V-A Italy-Switzerland 2014/2020, Project MONGEFITOFOR id 540693
- Keywords
- Modality
- Pôster
- Subject Area
- Other
