| The species richness of wood decaying fungi in boreal forests is declining, mainly due to lack of dead wood. Consequently, a large number of species occur on the national redlist. This decline is strongly associated with the loss of particular types of dead wood with certain qualities. Dead standing pine snags, so called Kelo trees (Niemelä et al 2002), belongs to this group of unique but diminishing substrates and is the focus of the present study. Kelos can remain standing for a very long time (in some cases up to 500y) in the forest due to high amounts of phenols and resin. It has been suggested that Kelos are species poor while standing, but become a substrate for many species when they fall (Renvall 1995). These assumptions are based on fruiting body inventories. A study based on mycelial constituents within the trunks may, however, give a different picture. We intend to investigate if old Kelos harbor remnants of past colonizations and thus if they have the potential to contain threatened or even presumed locally extinct species.
Studies of fungal mycelia communities in other types of dead wood have found a much higher species richness compared to fruiting body inventories. In these studies, results of Next Generation Sequencing (NGS) (Lim et al. 2010; Kubartova et al. 2012) suggests that the dynamics of mycelium communities within logs are governed by different processes than those causing fruiting body formation (Kubartova et al. 2012; Hoppe et al. 2016) and has confirmed that small mycelia can persist for extended time inside a log without fruiting. Thus, theoretically, the mycelium community within dead wood may represent several decades, or potentially centuries, of colonization.
Hence, there is reason to believe that the species composition within Kelos; i) is not well reflected by fruiting body studies, ii) can be studied using NGS, iii) represent not only the current, but also the historic species community in a forest stand, iv) include species that appear locally extinct, v) could become sources for these species at stand and landscape level. Kelos may therefore act as lifeboats for threatened species, a refuge in which specialized and rare species may persist until the Kelo has fallen down and is finally decayed.
In this project, we will sample Kelos of different ages for wood fungi mycelium DNA and use NGS to determine the species composition. Eighteen sites in northern Sweden, with different level of habitat fragmentation will be selected. By dating the age and time since death through dendrochronology and combining this with data on landscape composition and configuration, we will explore whether, when and how Kelo trees can serve as temporal life boats and contribute to the protection of threatened wood fungi in boreal pine forests.
We aim to test the following hypotheses:
1. Kelos harbor rare or even locally extinct species not detected by fruit body inventories
2. Time since death of a Kelo influence the species composition, i.e. contains a signal from earlier landscape structure, and thus old Kelos have a higher frequency of rare and threatened species
3. The species composition in Kelos differ from that of other dead wood and relate to the spatial and temporal occurrence of old forest in the surrounding landscape |