title: The role of root development of Avena fatua in conferring soil strength.
abstract: •
  
  
  OBJECTIVE
  Roots play an important role in strengthening and stabilizing soils. Existing models predict that tensile strength and root abundance are primary factors that strengthen soil. This study quantified how both factors are affected by root developmental stage.•
  
  
  METHODS
  Focusing on early development of Avena fatua, a common grassland species with a fibrous root system, we chose three developmental stages associated with major changes in the root system. Seeds were planted in rhizotrons for easy viewing and pots to allow root growth surrounded by soil. Tensile strength was determined by subjecting root segments to a progressively larger pulling force until breaking occurred. Root abundance at two depths was characterized by the cross-sectional area of the roots divided by the area of the soil core (i.e., root area ratio). Shear strength of 50 mm saturated soil columns was determined with a modified interface direct shear device.•
  
  
  RESULTS
  Tensile strength increased by a factor of ≥15× with distance from the root tip. Thus, soil-strengthening properties increased with root cell development. Plants grown under dry soil conditions produced roots with higher maximal tensile strength (41.9 MPa vs. approximately 17 MPa), largely explained by 33% thinner diameters. Over 7 weeks of root growth, root abundance increased by a factor of 4.8× while saturated soil shear strength increased by 24% in the upper soil layer.•
  
  
  CONCLUSIONS
  Root development should be incorporated into models of soil stability to improve understanding of this important environmental property.
authors.affiliation: Department of Land, Air, and Water Resources, University of California, Davis, California 95616 USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Dumlao
authors.affiliation: Applied Math Lab, Courant Institute, New York University, New York, 10012 USA.
authors.forename: Sophie
authors.initials: S
authors.lastname: Ramananarivo
authors.affiliation: Department of Land, Air, and Water Resources, University of California, Davis, California 95616 USA.
authors.forename: Vivek
authors.initials: V
authors.lastname: Goyal
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Davis, California 95616 USA.
authors.forename: Jason T
authors.initials: JT
authors.lastname: DeJong
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Davis, California 95616 USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Waller
authors.affiliation: Department of Land, Air, and Water Resources, University of California, Davis, California 95616 USA.
authors.forename: Wendy K
authors.initials: WK
authors.lastname: Silk
mesh_terms: D018554:Avena / Q000254:growth & development*; D008962:Models, Theoretical; D018517:Plant Roots / Q000254:growth & development*; D012987:Soil; D013718:Tensile Strength
chemical_list: D012987:Soil
keywords: Poaceae; biomechanics; grass roots; root area ratio; root development; root tensile strength; soil strength