Abstract
Annual row cropping systems converted to perennial bioenergy crops tend to accrue soil C, likely a function of increased root production and decreased frequency of tillage; however, very little is known about the mechanisms governing the accrual and stability of this additional soil C. To address this uncertainty, we assessed the formation and stability of aggregates and soil organic C (SOC) pools under switchgrass, giant miscanthus, a native perennial grass mix and continuous corn treatments in Michigan and Wisconsin soils differing in both texture and mineralogy. We isolated different aggregate size fractions, >2 mm, 0.5–2 mm, and <0.5 mm, using a procedure intended to minimize alterations to aggregate biological and chemical properties. We determined SOC, permanganate oxidizable C (POXC), and microbial activities (i.e. enzyme activities and soil respiration rates) associated with these aggregates. Soil type strongly influenced the trajectory of aggregate formation and stabilization with differences between sites in mean aggregate size, stability, SOC and microbial activity under perennial vs. corn cropping systems. At the Michigan site, soil microbial activities were highest in the >2 mm aggregates, and higher under the perennial grasses compared to corn. Contrastingly, in Wisconsin soils, microbial activities were highest in the <0.5 mm aggregates and evidence for soil C accrual under perennial grasses was observed only in a fast turnover pool in the <0.5 mm aggregate class. Our results help explain cross-site variability in soil C accrual under perennial bioenergy crops by demonstrating how interactions between belowground productivity, soil type, aggregation processes and microbial communities influence the rates and extent of SOC stabilization. Bioenergy cropping systems have the potential to be low-C energy sources but first we must understand the complex interactions controlling the formation and stabilization of SOC if we are to maximize soil C accrual.
Department
Soil Biogeochemistry and Microbial Ecology
Publication Date
3-1-2014
Journal Title
GCB Bioenergy: Bioproducts for a Sustainable Bioeconomy
Publisher
Wiley
Digital Object Identifier (DOI)
Document Type
Article
Recommended Citation
Tiemann, L.K. and Grandy, A.S. (2015), Mechanisms of soil carbon accrual and storage in bioenergy cropping systems. GCB Bioenergy, 7: 161-174. https://doi.org/10.1111/gcbb.12126
Comments
This is an open access article published by Wiley in GCB Bioenergy: Bioproducts for a Sustainable Bioeconomy in 2014, available online: https://dx.doi.org/10.1111/gcbb.12126