Response Of Epiphytic Lichens Research Articles

The response of epiphytic lichens on living and dead Pinus sylvestris to prescribed fires of varying severity

Prescribed burning can be used to restore forest ecosystems degraded by anthropogenic pressures. However, some species such as epiphytic lichens may be vulnerable to fire. We studied the effects of fire on epiphytic lichens on living and dead Pinus sylvestris (Scots pine) by surveying lichens up to two meters on the trunks 21 years after experimental and replicated prescribed burnings in pine-dominated boreal forests in Finland. We investigated three types of stands that had faced different levels of fire severity: 1) unburned semi-natural mature stands (i.e., control sites), 2) burned semi-natural mature stands, and 3) burned retention groups on clearcut sites. In the semi-natural mature stands, the fires were low-severity surface fires and induced negligible mortality in P. sylvestris. In the retention groups, the fires induced high tree mortality and made fresh deadwood the dominant substrate type. Low-severity fires reduced the occurrence of several species, but usually did not eliminate them. High-severity fires eliminated some species, but the abundant deadwood frequently hosted some species that were absent or infrequent on the unburned sites. Thus, the fires had only small effects on total species richness. However, fires substantially changed species composition: they reduced the occurrence of species associated with late-successional habitats, while increasing the occurrence of early-successional species. We also found fires to decrease the occurrence of microlichens and increase that of macrolichens. The magnitude of the compositional changes increased with fire severity. Our findings indicate that the high quantities of fresh deadwood in post-disturbance forests provide habitat only to a limited portion of deadwood-associated lichens. Fire can increase landscape-scale variation in epiphytic lichen communities, but we observed negative effects, which increased with fire severity, on lichen flora of conservation concern. Thus, we recommend prescribed burning to be applied primarily in sites with a history of intensive management. Fire should be avoided in sites with substrates that are fire-sensitive and important to lichen diversity.

An assessment of the sampling procedure for estimating air pollution using epiphytic lichens as indicators

Abstract: Using the response of epiphytic lichens in and around the city of Thessaloniki (Greece) to an air pollution source, the value of sampling lichens at breast height and the base of trees was compared. The data obtained were processed with detrended correspondence analysis and polythetic divisive two-way indicator species analysis, and IAP (index of atmospheric purity) values were estimated for each experimental site. The tree base IAP values were higher than those at breast height, reflecting the higher number of species present, the generally increased cover and frequency of occurrence. IAP values at the two sampling heights suggest a linear relationship and the same holds for the tree base IAP values and the first axis ordination scores. Sampling at the base resulted in better discrimination of sites, and may, therefore, offer more accurate monitoring of changes induced by air pollution.