Background/Question/Methods
Woody debris and its decomposition both play a major role in the global carbon cycle. Trends in wood decomposition have been studied greatly in terrestrial systems, and climatic variables, tree species, and other factors have been found to drive changes in wood decomposition globally. Wetlands, both inland and coastal, have been excluded from global meta-analyses of wood decomposition. I used data from 27 wetland studies with 162 separate measurements of decomposition and fitted a meta-regression model with parameters describing physical (temperature, precipitation, salinity, tide), biological (phylogenetic relationship), and experimental (location of decomposition, length of the experiment, size of wood) differences. Model selection using a maximum likelihood framework tested all combinations of explanatory variables and corresponding two-way interactions before providing a list of the top models.
Results/Conclusions
I found that the size and location of the wood being decomposed explained most of the variation in decomposition rate, followed by salinity, temperature, and precipitation. Buried wood decomposed much slower than wood that was decomposing on the surface, and smaller wood size classes decomposed faster than larger wood size classes. Temperature had a weak inverse relationship with decomposition rate, a stark contrast to the strong positive relationship between temperature and decomposition rate in upland systems. Wetlands with higher salinity saw lower decomposition, while wetlands that experience higher precipitation saw faster decomposition rates. Overall, wetland decomposition rates were several orders of magnitude slower than those found in similar meta-analyses of upland decomposition rates. My findings indicate that wood decomposition is controlled by different factors in wetlands than in uplands.