Divergent effects of root and leaf litter on soil microbial diversity decouple soil C-N release

Abstract

Litter decomposition drives grassland biogeochemical cycles, yet the distinct roles of leaf and root litter identity, richness, and functional traits in regulating soil microbial diversity and decomposition remain poorly resolved. Using a 120-day mesocosm experiment with leaf and root litter of the dominant species in Inner Mongolia grassland, we assessed how litter type (leaf vs. root), richness (1, 2, 4 species), and identity (root or leaf litter of 4 dominant species) modulate microbial diversity and soil carbon (C) and nitrogen (N) release. We found that litter type and identity more strongly influenced microbial biomass than species richness, and root litter supported higher bacterial alpha diversity but lower microbial biomass and fungal beta diversity compared to leaf litter. Root litter identity primarily affected the overall beta diversity patterns of both bacterial and fungal communities, while greater leaf litter richness significantly suppressed soil C release. Mechanistically, root litter identity associated with the resource-conservative strategy directly controlled soil C release and indirectly regulated N retention via bacterial beta diversity. Conversely, leaf litter type characterized by the resource-acquisitive strategy primarily affected soil C release by altering microbial alpha diversity, and could also enhance N release by directly increasing soil microbial biomass. Our results underscore the significant influence of litter type, identity, and richness on soil microbial diversity and C and N release, supporting the strategic use of litter identity to modulate C and N release and the enhancement of C sequestration through increased leaf litter richness in grassland restoration efforts.

Graphical abstract

Keywords

litter trait / species identity / species richness / SOM release / litter functional traits / C-N decoupling

Highlight

	● Root litter boosts bacterial diversity but reduces microbial biomass vs. leaf litter.
	● Litter identity outweighs richness in shaping microbial communities and C-N release.
	● Leaf litter richness suppresses CO2 emissions, while root traits control N retention.
	● Root recalcitrance sustains fungal beta diversity, whereas leaf chemistry drives bacterial convergence.
	● Integrated leaf-root management balances grassland C sequestration and nutrient cycling.

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