Soil carbon and silicon pools across an un-drained toposequence in central Ohio

Abstract

Numerous studies have been conducted to assess soil carbon pools, but few studies have been carried out on Si pools across landscapes. However, most have focused on the upper 30cm depth. Thus, this study focused on soil carbon (organic and inorganic) and silicon pools across a soil toposequence encompassing all landscape positions (summit, shoulder, backslope, footslope, and toeslope), and for the soil profile. A soil toposequence, derived from till parent material with an un-drained closed depression, was selected for the study. All soil samples were analyzed for selected physical and chemical properties. Soil bulk density (ρb) generally decreased down slope from 1.21 to 0.88Mgm−3 for the surface horizons at the summit and toeslope landscape positions, respectively. The pH was generally acidic, and it slightly increased down slope from 5.2 to 6.5 for the surface horizons at the summit and toeslope, respectively. Soil total carbon (STC) increased substantially down slope from 2.12% for the A horizon at the summit to 23.8% for the Oa3 horizon at the toeslope. Soil organic carbon (SOC) followed the same trend of STC across the landscape because soil inorganic carbon (SIC) was not present in these soils. Soil total N (STN) followed the same distribution of STC across the toposequence and within pedons. It increased from 0.19 to 0.85% for the surface horizons at the summit and toeslope landscape positions, respectively. Plant available Si (PASi) and amorphous Si (ASi) concentrations increased downslope across the toposequence and increased downward within pedons. PASi increased from 43 to 101mgkg−1 and ASi increased from 809 to 1091mgkg−1 for the surface horizons at the summit and toeslope positions, respectively.