Warming effects on wood decomposition depend on fungal assembly history

Climate warming has the potential to drive changes in fungal community development and dead wood decomposition, but our understanding of this process is obscured by complex interactions between temperature and multiple other factors. A pivotal factor driving decay dynamics is fungal assembly history, yet its response to elevated temperature is poorly understood. We investigated the combined effect of warming and assembly history on community composition, respiration and decomposition using experimental communities of wood-decaying fungi on spruce wood. Assembly histories were assigned to microcosms under normal and elevated temperatures in a factorial design. Both temperature and assembly history influenced wood mass loss and respiration. Temperature was the most important factor, but the effects of warming on decomposition varied greatly with fungal assembly history. Depending on which fungal species colonized first, warming of 5 degrees C increased wood mass loss by 7%-57% after 9 months. The large variation in decomposition response to warming resulted from differential responses in the growth of initial colonizers (pre-inoculated) and their competitive ability, resulting in different decomposer communities. Synthesis. Our study demonstrates that temperature and assembly history jointly determine deadwood decomposition and fungal community composition under controlled laboratory conditions. Further investigations are needed to confirm these results under natural conditions. Nevertheless, our findings highlight the importance of considering interactions between priority effects and climate factors to understand forest carbon feedbacks in the context of climate change.