Necromass of diverse root-associated fungi suppresses decomposition of native soil carbon via impacts of their traits

We investigated the decomposition of diverse root-associated fungi, their influence on native soil carbon (C) dynamics and the relationship of these processes with fungal traits. We quantified the decomposition of ¹³C-labelled mycelium of 14 species, their priming of native soil C, impact on functional soil C pools, microbial use of C and microbial community size and composition and evaluated chemical, morphological and physiological traits of the fungi to investigate their potential to control C processes. Fungal melanin, blackness, C/N and growth rates were linked to necromass decomposability and its stabilisation. Necromass addition commonly caused suppression of native soil C decomposition (negative priming), including that of the resistant C pool, and this suppression was stronger as fungal decomposability decreased. We provide novel, clear evidence of linkages between root-associated fungal traits, necromass decomposition, microbial C use and soil C stability which builds our mechanistic understanding of the role of dead fungi on soil C storage.