DEADMON: A protocol for long-term monitoring of deadwood-associated species

Dead wood has a vital role in maintaining biodiversity and ecosystem processes in boreal forests. A large proportion of deadwood-dependent species are threatened by habitat loss and degradation resulting from intensive forest management practices. In Finland, approximately 25% of all forest-dwelling species, around 5,000 species, are dependent on deadwood, of which 596 are red-listed. Currently, there is no large-scale, long-term monitoring programme for saproxylic species in Finland, and the tools required to implement such monitoring remain underdeveloped. Here, we develop, test and report a DNA-based monitoring method for dead wood associated organisms including fungi, lichens, bryophytes, and insects. Three study sites were selected for the research, one from each boreal vegetation zone. From each study site, 16 study logs were selected and permanently marked for long-term monitoring. Our results show that the method is applicable to all studied species groups. However, especially fungi and lichens show considerable difference between species detected morphologically and those detected using DNA-based methods. We conclude that two partly contrasting strategies emerge for implementing long-term monitoring of deadwood -associated boreal species. The first strategy emphasizes as comprehensive geographical sampling of habitat types and tree species as possible. The second approach focuses on long-term monitoring of individual deadwood units across their full decomposition trajectory. We recommend that solutions for unifying the currently fragmented monitoring research on deadwood-associated organisms would be sought together with potential coordinating institutions.