BayCEER Workshop 2025

Fungal biomass and microbial necromass in highly decomposed deadwood of 13 tree species.

P 21 in Posters

Highly decomposed deadwood could represent a potentially stable organic matter fraction that contributes to long-term carbon storage in forest ecosystems. Microorganisms, in particular fungi, drive the transformation of deadwood into stable organic matter. However, little is known about fungal biomass and microbial necromass in highly decomposed deadwood. We quantified fungal biomass via ergosterol and fungal and bacterial necromass via analysis of amino sugars (Glucosamin, Muramic acid) in two deadwood fractions of the final decay stage. The two fractions were sampled from logs of 13 tree species in four pine forests at Schorfheide-Chorin (BELongDead experiment) and comprise deadwood fragments of low density (hereafter DW-V) and powdery deadwood (< 2 mm, hereafter DW-H). In addition, soil organic matter from the Oh horizons was analyzed in the same way as reference material for each forest site.  

Our results confirm that the phylogenetic group of tree species is a key driver of fungal biomass, with significantly higher ergosterol contents in Angiosperms than in Gymnosperms. Fungal biomass in deadwood of Angiosperms was 1.36 times higher in DW-V compared to DW-H whereas no difference was found for Gymnosperms. Ergosterol in DW-V was significantly higher than in soil, while DW-H showed no significant difference. Likewise the fungal necromass did not differ among decay stages, but it tended to be higher in angiosperm than in gymnosperm deadwood. The fungal-to-bacterial necromass ratio declined from DW-V to DW-H and soil, although this pattern was not statistically significant. In summary, wood phylogeny governs fungal biomass, which does not uniformly increase with decay. Also the tree chemistry may influence fungal necromass production, whereas decay progression has a weaker effect on the fungal-to-bacterial ratio. 

Keywords: highly decomposed deadwood, fungal biomass, microbial necromass, ergosterol, amino sugars