The FACE experiment: Wood decomposition and its role in the forest carbon cycle

Dead wood is a huge portion of the total carbon pool in forests. But despite its ecological importance, there is not enough information on the factors that affect wood decomposition. For example, there are no mechanistic models that effectively simulate wood decay and the incorporation of wood carbon into soil across North America. New research is providing insights and tools for improving our understanding of the forest carbon cycle.

Cut pine logs lie on the ground; other logs stand upright on plastic cylinders. — The FWDE installation within a lodgepole pine (*Pinus contorta*) stand on the Tenderfoot Creek Experimental Forest. Logs are incubated on the ground (foreground) and to emulate standing dead wood (on plastic cylinders). USDA Forest Service photo by Carl Trettin.

A long-term research project called the Free Air Carbon Dioxide Enrichment (FACE) Wood Decomposition Experiment is providing foundational knowledge on wood decomposition and associated interactions with the underlaying soil. The study is being conducted across nine experimental forests in the U.S.

The study uses logs from three species: loblolly pine, aspen, and birch. The logs are unique because they all come from FACE sites. This means they have distinct isotopic signatures. These signatures allow researchers to follow individual carbon atoms as they move from wood to soil. In 2011, these logs were placed horizontally on the soil surface and vertically without soil contact to simulate standing dead trees.

The long-term study is still underway, but it has already provided the basis for new insights into the fungal communities that colonize wood and their role in decomposition. Researchers have also used the study results to model effects of management and climate change on wood decomposition. The study provides a unique capability to understand the fate of wood consumed by subterranean termites, insight relevant to the soil carbon pools and greenhouse gases.

Principal Investigator: Carl C. Trettin, Team Leader, Supervisory Research Soil Scientist
RWU: 4353 - Center for Forest Watershed Research
Publications: Wood-decay type and fungal guild dominance across a North American log transplant experiment; The fate of carbon utilized by the subterranean termite Reticulitermes flavipes; Coarse Woody Debris Decomposition Assessment Tool: Model validation and application
Research Partners: Debbie Page-Dumroese, Rocky Mountain Research Station; Daniel Lindner, Northern Research Station; Randall Kolka, Northern Research Station; Pete Wohlgemuth, Pacific Southwest Research Station; Jackson Leonard, Rocky Mountain Research Station; Elizabeth Keppeler, Pacific Southwest Research Station; Helen Smith, Rocky Mountain Research Station; Banning Starr, Rocky Mountain Research Station; Kelly Elder, Rocky Mountain Research Station
External Partners: Andrew Burton, Michigan Technological University; Martin Jurgensen, Michigan Technological University; Zhaohua Dai, Michigan Technological University; Jonathan Schilling, University of Minnesota; Brian Forschler, University of Georgia; Ram Orem, Duke University