Mechanisms influencing physically sequestered soil carbon in temperate restored grasslands in South Africa and North America
Abstract
Sequestering carbon (C) into stable soil
pools has potential to mitigate increasing atmospheric
carbon dioxide concentrations. Carbon accrues in
grassland soil restored from cultivation, but the amount
of physically protected C (here measured as microaggregate-within-macroaggregate C) and predominant
mechanisms of accrual are not well understood. We
modeled the rate of physically protected carbon
accrued in three mesic temperate perennial restored
grasslands from cross-continental regions using datasets with a wide range of restoration ages from
northeast Kansas, USA; southeast Nebraska, USA;
and northeast Free State, South Africa. Further, we investigated major controls on the amount of physically protected C in each site using structural equation
modeling. Variables in the structural equation model
were root biomass, root C:N ratio, soil structure
(indicated by bulk density, percent of macroaggregates
on a per whole soil mass basis, and percent of
microaggregate-within-macroaggregates on a per
macroaggregate mass basis), microbial composition
(indicated by microbial biomass C, total phospholipid
fatty acid [PLFA] biomass, and PLFA biomass of
arbuscular mycorrhizae fungi [AMF] biomass), and
microaggregate-within-macroaggregate C on a per
whole soil mass basis.