The response of lichen growth forms to fire frequency: a case study in oak forests of the southern Russian Far East

Abstract

Epiphytic lichens are used as sensitive indicators of environmental changes. Lichen growth forms are related to biotic and abiotic factors. In the present study, we investigate the response of lichen growth form diversity to fire frequency. In the oak forests of the southern Primorsky Krai, we established 43 sampling plots of 25 m x 25 m each. All plots were assigned to four fire history regimes defined by the combination of fire marks. A total of 168 epiphytic lichen species were recorded. They were classified into 12 groups of growth forms. The linear regression model demonstrated that the taxonomic diversity of epiphytic lichens and the growth form diversity were highly and positively correlated. Increasing fire frequency resulted in limited damage to growth form diversity of the epiphytic lichen communities, whereas species diversity drastically decreased with increasing fire frequency. The diversity of most growth form groups were connected with the gradient of fire frequency. Diversity of growth forms tolerant to a wide environmental variety, such as foliose species with narrow lobes, crustose granular verrucose, and compact crustose, drastically decreased under regular fire events. In contrast, growth forms adapted to sheltered and humid environments, such as foliose gelatinous, foliose inflated, and foliose with broad lobes, were absent on the plots with regular and frequent fire events. Thus, due to the close relationship between morphological traits and specific environmental conditions, certain groups of growth forms can be used as indicators of fire regimes of forests.