4.5 Article

Influence of living grass Roots and endophytic fungal hyphae on soil hydraulic properties

Journal

RHIZOSPHERE
Volume 22, Issue -, Pages -

Publisher

ELSEVIER
DOI: 10.1016/j.rhisph.2022.100510

Keywords

Switchgrass ( Panicum virgatum ); Serendipita indica; Porosity; Soil water retention; Hydraulic conductivity

Funding

  1. METER Group Inc. through a Grant A. Harris Fellowship
  2. U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research
  3. DOE [DE-AC05-00OR22725]

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This study reviews the current knowledge on the effects of soil biotic components, such as roots and mycorrhizal fungi, on hydraulic properties. Laboratory experiments were conducted to specifically test the impact of these components on two different soils. The results demonstrate that the presence of roots and mycorrhizal fungi significantly affects the hydraulic properties of soil, highlighting the importance of considering these factors in soil hydraulic models.
Soil hydraulic properties are often estimated based on laboratory data or pedotransfer functions dependent on soil physical properties, which often do not consider potential impacts of soil roots or fungal hyphae. Here, we first review current knowledge of how these soil biotic components affect hydraulic properties, then we con-ducted laboratory experiments to specifically test if the presence of roots and mycorrhizal fungi had a significant effect on the hydraulic properties of two soils with contrasting textures: Flint sand and Hamblen silt loam. Soil cores were seeded with (Panicum virgatum) and grown in a greenhouse over three separate growth periods. The endophytic fungus Serendipita indica was injected as liquid inoculant into designated mycorrhizal cores. Satu-rated hydraulic conductivity (K-sat) measurements were made with a constant head permeameter, and soil water retention curves were obtained by the evaporation method, supplemented at the dry end for Hamblen silt loam with water activity meter data. Retention curve parameters were obtained by fitting the van Genuchten equation to the resulting measurements. Mean root volume ratios were higher in the mycorrhizal inoculated treatment than in the uninoculated treatment for both soils. For Flint sand, analysis of variance revealed that K-sat was reduced by the presence of roots as compared to bare soil. This was likely due to roots clogging soil pores. Results also indicated the presence of roots changed the shape of the water retention curve for Flint sand by increasing water content at saturation and by reducing the slope of the curve. These changes suggested roots created additional porosity and broadened the pore-size distribution. The presence of mycorrhizal fungi accentuated the root effects. The influence of roots and mycorrhizal fungi on hydraulic properties was less obvious for the Hamblen silt loam, as none of the treatments differed from each other at p < 0.05. The results highlight the necessity to consider the impact of root and fungal structures on models of soil hydraulic properties.

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