Biodiversity of polypores inhabiting Populus tremula L. within regenerating stands of the Białowieża Primeval Forest (E Poland)

Abstract

Human-induced disturbances have a significant impact on populations of polypores. In the 20th century, Białowieża Primeval Forest (BPF) was strongly affected by harvesting disturbance. As a result of natural regeneration, forest stands are composed predominantly of pioneer species regenerated in harvested areas. We asked how substrate type, stand age, site conditions, substrate size, and decay stage of post-clearcut stands affect species richness and composition of polypore communities inhabiting aspen Populus tremula.Data was collected in broadleaf stands representing two levels of site conditions (mesic and wet) and two categories of age (young 30–60 years and old 80–110 years old), seven stands for each factor combination, a total of 28. In each forest stand 11 sampling plots were systematically established where basidiomata were registered on a 4-m fragment of the nearest log and up to a 4-m height of the nearest living aspen tree, a total of 308 samples for each substrate category. Due to the hierarchical structure of data, the influence of environmental variables on number of species registered was modeled with mixed effect models. The influence of environmental factors on polypore composition was assessed with db-RDA models.Twenty-five species of polypores were found, including seven red-listed and one legally protected in Poland. The number of observed polypore species was significantly higher on logs and in older stands, but site conditions did not influence it. The stand age influenced the number of species on living trees but not on logs. The increase in log diameter and moderately advanced decay stage positively affected species number. The same factors were found to impact polypore community composition. The results confirm the high importance of aspen for polypore diversity maintenance.