Spatial analysis of lichen species richness in a disturbed ecosystem (Niepołomice Forest, S Poland)

Abstract

The spatial pattern of lichen species richness was analyzed in a forest ecosystem impacted for 50 years by industrial emissions from a steelworks. Geostatistical tools were used to characterize the spatial pattern of the number of lichen species and multiple regression analysis was used to identify factors influencing it. Spatial analysis showed high variation of lichen species richness on a local scale, caused by patchiness of natural habitat factors (species composition of trees, their age, shade, etc.). On a large spatial scale, species richness differentiated the western from the eastern part of the forest. The western part, closer to the sources of pollution, had fewer species (average 6–10 per locality) than the eastern part (10–15 per locality). Multiple regression analysis was used to examine the relationships between the species richness of lichens and several environmental variables: input of ions with bulk precipitation (SO₄²⁻, NO−3, Cl⁻, Ca²⁺, Mg²⁺, Fe³⁺, Zn³⁺, Pb²⁺, Cd²⁺), distance to forest edge, tree stand age, and number of species per locality. Regression analysis was preceded by factor analysis for the input of ions to obtain uncorrelated variables. Regression explained 53% of the variation of lichen species richness. Highly significant predictor variables were the factor connected with the input of pollutants (Fe³⁺, Zn²⁺) emitted by the steelworks (negative effect) and the number of trees per locality (positive effect). Species richness was also affected by the age structure of the tree stand; more species were recorded in old forests.