The Science

Current projections suggest an increase in dead wood biomass as a result of more frequent and intense climate extremes and disturbances (e.g., deforestation, storms, drought, heat waves, and fire) in the future and thus wood decomposition plays a key role in regulating local and regional climates after disturbances. The decomposition rates depend on both wood characteristics (i.e., traits) and associated climates. This global meta-analysis study found that global variation in wood decomposition rates are mostly contributed by stoichiometric and geometric (e.g., surface area) wood traits (>50%), an amount much larger than that contributed by climates (~20%).

The Impact

Understanding wood decomposition rates under global change is important for modeling the ecosystem feedbacks to climate. This study highlights the importance of wood traits for wood decomposition across global climate gradients, challenging the conventional view that climate is the dominant driver of decomposition rates at broad spatial scales. This perspective provides the basis for future development and parameterization of decomposition within most Earth system models.

Summary

Wood decomposition is a major component of the global carbon cycle. Decomposition rates vary across climate gradients, which are thought to reflect the effects of temperature and moisture on the metabolic kinetics of decomposers. However, decomposition rates also vary with wood traits, which may reflect the influence of stoichiometry on decomposer metabolism as well as geometry relating the surface areas that decomposers colonize with the volumes they consume. This study combined metabolic and geometric scaling theories to formalize hypotheses regarding the drivers of wood decomposition rates. It assessed these hypotheses using a global compilation of data on climate, wood traits, and wood decomposition rates. These results are consistent with predictions from both metabolic and geometric scaling theories. Approximately half the global variation in decomposition rates was explained by wood traits (nitrogen content and diameter), whereas only a fifth was explained by climate variables (air temperature, precipitation, and relative humidity). These results indicate that global variation in wood decomposition rates is best explained by stoichiometric and geometric wood traits. The findings suggest that inclusion of wood traits in global carbon cycle models can improve predictions of carbon fluxes from wood decomposition.

Principal Investigator

Chonggang Xu
Los Alamos National Laboratory
cxu@lanl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

The manuscript’s first author, Zhenhong Hu, was also supported by China Postdoctoral Science Foundation (2017M622709) and Foundation for High Level Talents in Higher Education of Guangdong, China (2014KZDXM018), which supported his visit to Los Alamos National Laboratory (LANL). Sean T. Michaletz and Daniel J. Johnson were supported by Director’s Fellowships from LANL. Nate McDowell and Chonggang Xu were supported by the Next-Generation Ecosystem Experiments (NGEE)–Tropics project and Survival–Mortality experiment (SUMO) support from the U.S. Department of Energy Office of Science.

References