Carbon fractions in the world's dead wood

A key uncertainty in quantifying dead wood carbon (C) stocks-which comprise similar to 8% of total forest C pools globally-is a lack of accurate dead wood C fractions (CFs) that are employed to convert dead woody biomass into C. Most C estimation protocols utilize a default dead wood CF of 50%, but live tree studies suggest this value is an over-estimate. Here, we compile and analyze a global database of dead wood CFs in trees, showing that dead wood CFs average 48.5% across forests, deviating significantly from 50%, and varying systematically among biomes, taxonomic divisions, tissue types, and decay classes. Utilizing data-driven dead wood CFs in tropical forests alone may correct systematic overestimates in dead wood C stocks of similar to 3.0 Pg C: an estimate approaching nearly the entire dead wood C pool in the temperate forest biome. We provide for the first time, robust empirical dead wood CFs to inform global forest C estimation.

Automated summary

The study highlights the uncertainty in quantifying dead wood carbon pools globally due to a lack of accurate dead wood carbon fractions. By analyzing a global database, the study found that dead wood carbon fractions in trees average 48.5%, which deviates from the commonly used default value of 50%. Utilizing data-driven dead wood carbon fractions may help correct systematic overestimates in dead wood carbon stocks and provide more accurate global forest carbon estimation.