Physical soil architectural traits are functionally linked to carbon decomposition and bacterial diversity.
Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence of pore geometry on the organic carbon decomposition rate and bacterial diversity in both macro- (250-2000 μm) and micro-aggregates (53-250 μm) using field samples. Four sites of contrasting land use on Alfisols (i.e. native pasture, crop/pasture rotation, woodland) were investigated. 3D Pore geometry of the micro-aggregates and macro-aggregates were examined by X-ray computed tomography (μCT). The occluded particulate organic carbon (oPOC) of aggregates was measured by size and density fractionation methods. Micro-aggregates had 54% less μCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, the pore connectivity in micro-aggregates was lower than macro-aggregates. Despite both lower μCT observed porosity and pore connectivity in micro-aggregates, the organic carbon decomposition rate constant (Ksoc) was similar in both aggregate size ranges. Structural equation modelling showed a strong positive relationship of the concentration of oPOC with bacterial diversity in aggregates. We use these findings to propose a conceptual model that illustrates the dynamic links between substrate, bacterial diversity, and pore geometry that suggests a structural explanation for differences in bacterial diversity across aggregate sizes.
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.|Plant, Soil and Environment Systems, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
S M F
SM
Rabbi
Plant, Soil and Environment Systems, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
H
H
Daniel
Plant, Soil and Environment Systems, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
P V
PV
Lockwood
Hawkesbury Institute for the Environment, Western Sydney University, Sydney, Australia.
C
C
Macdonald
School of Science and Technology, University of New England, Armidale, NSW, Australia.
L
L
Pereg
Plant, Soil and Environment Systems, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
M
M
Tighe
Plant, Soil and Environment Systems, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
B R
BR
Wilson
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
I M
IM
Young
D000383:Agriculture; D001419:Bacteria; D044822:Biodiversity; D002244:Carbon / Q000378:metabolism*; D005591:Chemical Fractionation; D065928:Forests; D007091:Image Processing, Computer-Assisted; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D014057:Tomography, X-Ray Computed
D012987:Soil; D002244:Carbon