Degradation of logs installed underground for a half century and the microbial communities involved

Abstract The use of wood in civil engineering projects is attractive from the perspective of utilizing renewable materials and reducing CO 2 emissions. Furthermore, civil engineering presents an appealing opportunity to expand the demand for wood. Wood degradation rates are low in anaerobic environments, such as underground conditions. In this study, the degradation of wood after 55 years in an underground environment was examined by analyzing logs that had been driven underground for a soil stabilization project. Log density was measured and wood cell walls were observed under a microscope to estimate the degree of degradation, and the bacterial and fungal communities living in the sapwood of the logs were examined using a metagenomic approach. The results showed that the wood density was hardly reduced, and that anaerobic cellulolytic bacteria were dominant in the microbial communities in the wood. The degree of wood degradation over 55 years was low, indicating that these logs retained their ground improvement function for at least half a century.