Collaborative Research: Impact of microbial and termite communities on transfer of decaying wood to stable and protected mineral soil carbon pools

As forests age, the death of trees adds dead wood to the forest floor. Even in younger forests, strong wind events, insect outbreaks, fire and forest management all can result in accumulation of dead wood. Dead wood stores carbon, but how much in the long-term is uncertain. Much of the carbon in wood is slowly returned to the atmosphere as CO2 during decomposition. Some, however, also enters the soil, where it can be stored for decades to centuries. In 2011, pine, aspen and birch logs were placed in nine forests across the U.S. to help determine how factors such as climate, wood type, presence of termites and fungi affect wood decomposition rate. The wood used had a unique carbon isotopic signature that allows the research team to trace it as it enters the soil, and to measure how fast carbon is either lost to decomposition or stored as soil carbon. This knowledge will improve understanding of carbon cycling in forests and allow better prediction of how a changing climate or increased tree death from forest disturbance could alter carbon storage in forests. This research will help to determine if forests will be carbon sinks or sources for atmospheric CO2 over long time scales. The project will also give middle and high school students a chance to experience scientific research first-hand, and increase awareness of STEM topics in rural schools near four of the research sites. Project scientists will work with teachers to involve students in research-based discovery and analysis at a nearby field site and incorporate project topics related to ecology and soil science in school curricula, providing a foundation for increasing student interest in science and engineering careers.

The fungal and invertebrate communities that dominate wood decomposition have distinct lignin and carbohydrate decomposition pathways along a white- to brown-rot continuum, and these alter the amount of carbon diverted to the mineral soil. This study's specific objectives are to assess the role of different fungal/bacterial communities and termites on lignin- and carbohydrate-decay pathways for the three wood types and determine how this affects wood carbon movement into labile and protected mineral soil carbon pools. This entails: 1) using the 13C signature of labelled wood to assess the role of decomposer community function on wood-decay pathways, mass loss, and wood carbon movement into mineral soil; and 2) using a unique series of termite-exclusion plots to determine the effect of termite activity on fungal wood-decay community composition, wood-decay pathways, and incorporation of wood carbon into the mineral soil.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.