Climate and wood quality have decayer-specific effects on fungal wood decomposition

Any process that affects wood decomposition and decomposers in boreal forests may also affect the role that dead wood has on global carbon storages. We investigated under controlled laboratory conditions the impact of three major variables - temperature, humidity and wood quality - on Scots pine wood decomposition by four different fungal species. To reveal these effects, we conducted a nine-month factorial experiment. Wood quality was found to have a much more pronounced effect on fungal wood decay than climate variables. Furthermore, the fast-grown pine wood from managed forests decayed much faster than centuries old 'kelo' pine trees from natural forests as well as the slow-grown wood from managed forests. We found an overall increase in decomposition with temperature and humidity in Gloeophyllum protractum, except that the decay rate of the fast-grown wood declined with increasing temperature at higher humidity levels. The overall decomposition rates varied greatly with decayer species and wood type, and several interactions between temperature, humidity and wood quality effects were documented. In particular, we found that the fast decayers, Dichomitus squalens and Fomitopsis pinicola did not show any response to climate variables, but responded to wood quality only. The slow decayers Antrodia xantha and G. protractum responded to wood quality and interaction effects of climate and wood quality. Our results demonstrated species-specific effects of climate and wood quality when tested simultaneously, and show that it is critical to understand the different and complex mechanisms that affect wood decomposition and, consequently, carbon storages in forests, in order to increase the reliability of the climate-carbon prediction models.