Microbial necromass carbon and nitrogen persistence are decoupled in agricultural grassland soils

Microbial necromass is a significant component of soil organic matter (SOM), yet its persistence and contribution to soil carbon sequestration remain poorly understood. This study investigates the interaction of necromass with soil minerals and compares its persistence to plant litter in grasslands under varying management intensities. A year-long laboratory incubation showed higher carbon mineralization rates for plant leaf litter than root litter and necromass, but no significant difference in carbon persistence after one year. A field experiment revealed that two-thirds of isotopically labeled necromass carbon became mineral-associated within three days. Mineral-associated carbon declined faster than nitrogen over eight months, with persistence enhanced under increased management intensity. The study concludes that carbon mineralization rates are decoupled from carbon persistence, necromass carbon is less persistent than necromass nitrogen, and agricultural management intensity impacts carbon sequestration in grasslands.

Kate M. Buckeridge, Kelly E. Mason, Nick Ostle, Niall P. McNamara, Helen K. Grant, Jeanette Whitaker