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Soil Penetration by Earthworms and Plant Roots--Mechanical Energetics of Bioturbation of Compacted Soils.

Ruiz S, Or D, Schymanski SJ - PLoS ONE (2015)

Bottom Line: The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip).The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters.Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Systems Science, ETHZ, Zurich, Switzerland.

ABSTRACT
We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip). The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

No MeSH data available.


Related in: MedlinePlus

Cylindrical cavity expansion sequentially determines steady state penetration of acute cones.The conical cross section applies a boundary pressure that opens a cavity to some final steady state cylindrical burrow.
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pone.0128914.g003: Cylindrical cavity expansion sequentially determines steady state penetration of acute cones.The conical cross section applies a boundary pressure that opens a cavity to some final steady state cylindrical burrow.

Mentions: Dexter [14, 18], Bengough and Mullins [13] report that plant roots and earthworms penetrate soil in a similar manner as that of sharp penetrometers, deforming the soil cylindrically (see Fig 3). To model soil penetration by earthworms, a cavity expansion based cone penetration model is employed. Yu [31] and Durban and Fleck [32] developed a semi-analytic expression based on cavity expansion for rough and smooth penetration at different angles. This formulation considers the angular effects when neglecting friction. The penetration resistance stress can be expressed as [31, 32]:σz=su(π+2α+sin-1(m)+D2+mcotα-1-m2-1)+σr(15)where α is the semi-apex cone insertion angle, m ∈ [0, 1] is the gauge of roughness where m = 0 is lubricated, and m = 1 is rough, andD=sin(π-α2)+msin(π-α)cos(π-α2)-cos(π-α)


Soil Penetration by Earthworms and Plant Roots--Mechanical Energetics of Bioturbation of Compacted Soils.

Ruiz S, Or D, Schymanski SJ - PLoS ONE (2015)

Cylindrical cavity expansion sequentially determines steady state penetration of acute cones.The conical cross section applies a boundary pressure that opens a cavity to some final steady state cylindrical burrow.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4472233&req=5

pone.0128914.g003: Cylindrical cavity expansion sequentially determines steady state penetration of acute cones.The conical cross section applies a boundary pressure that opens a cavity to some final steady state cylindrical burrow.
Mentions: Dexter [14, 18], Bengough and Mullins [13] report that plant roots and earthworms penetrate soil in a similar manner as that of sharp penetrometers, deforming the soil cylindrically (see Fig 3). To model soil penetration by earthworms, a cavity expansion based cone penetration model is employed. Yu [31] and Durban and Fleck [32] developed a semi-analytic expression based on cavity expansion for rough and smooth penetration at different angles. This formulation considers the angular effects when neglecting friction. The penetration resistance stress can be expressed as [31, 32]:σz=su(π+2α+sin-1(m)+D2+mcotα-1-m2-1)+σr(15)where α is the semi-apex cone insertion angle, m ∈ [0, 1] is the gauge of roughness where m = 0 is lubricated, and m = 1 is rough, andD=sin(π-α2)+msin(π-α)cos(π-α2)-cos(π-α)

Bottom Line: The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip).The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters.Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Systems Science, ETHZ, Zurich, Switzerland.

ABSTRACT
We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip). The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

No MeSH data available.


Related in: MedlinePlus