Harvested and burned forests as habitats for polypore fungi

Abstract

This thesis explores the effects of controlled burning and logging intensity on wood-decaying polypore fungi 10 years after the treatments. Intensive forest management, where most of the wood is removed from harvested sites, has resulted in many dead-wood-dependent species becoming Red-listed. The role that managed forests and novel, more biodiversity-oriented silviculture could play in safeguarding fungal diversity has remained largely unclear. This thesis is based on data sets collected from five years: 2000, 2003, 2005, 2008 and 2011 from the same study areas. A large-scale, replicated experiment was established on 24 forest sites that were exposed to logging and burning treatments. The data comprised 98,136 observations of dead wood pieces and 22,150 observations from a total of 122 polypore species. The main findings in this thesis were; (1) Retention tree levels need to be high in order to maintain polypore diversity. I observed more polypore species on sites with 50 m3 ha-1 of retention trees than sites with 10 m3 ha-1. The burning of retention harvested sites accelerates the death and fall of retention trees and diversifies the dead wood quality at a managed site. Red-listed species were found chiefly on the burned sites with the higher retention level. (2) Harvested sites comprise widely different types of dead wood substrates: old natural dead wood, stumps, slash and retention trees, and all these contribute to polypore diversity in managed forests. The response of polypore species to management can typically be seen only after a longer period of time. After a disturbance, such as logging or fire, these four different dead wood substrates are available for polypores over different periods of time. (3) Burning harvested and unharvested sites increases the number of polypore species and diversifies the polypore assemblages. Of the four dead wood types, burning specifically leads to an increase in the number of polypores on stumps. These results demonstrate new possibilities for the conservation of dead-wood-dependent species outside protected areas. Leaving retention trees, abstaining from the extraction of logging residuals and maintaining old naturally formed dead wood are beneficial for polypore species. Prescribed fire can be utilized as an effective method to modify dead wood dynamics and for the creation of more variable dead wood substrates on managed forest sites.