Screening fungal species for soil-mycelia systems

Landslides induced by heavy rainfall and water infiltration into granular soils, pose a substantial challenge worldwide. As water infiltrates the soil, the degree of saturation increases and soil suction reduces with an associated reduction in soil shear strength, which can trigger the instability of these slopes. Landslides can have severe consequences, with 4,862 individual incidents resulting in more than 55,000 fatalities between 2004 and 2016 (Froude and Petley, 2018). Economically, landslides generate substantial financial burdens, for example in Europe, as much as 4.7 billion Euros each year (Haque et al., 2016) due to the cost of reconstruction and recovery efforts. Environmental consequences include the destruction of ecosystems, alteration of landscapes, and potential long-term impacts on soil quality.

Traditional strategies to mitigate slope failures rely on localised engineering interventions, including for example soil nailing, ground anchors, retaining walls, soil grouting, geotextiles, and drainage systems. Moreover, these solutions can have a high carbon footprint due to the reliance on the use of materials like cement and steel. Balancing the need for effective landslide prevention with minimising environmental impact and cost requires innovative, sustainable approaches. This research explores the potential of using filamentous fungi as a nature-based solution to mitigate landslides.

Filamentous fungi, through their unique structure composed of hyphae, create a vast network known as the mycelium. This mycelial network extends through the soil and binds particles together, enhancing soil stability (El Mountassir et al., 2018). Moreover, filamentous fungi also secrete hydrophobins, proteins that turn the surface they inhabit more hydrophobic (Salifu & El Mountassir, 2021). This induced hydrophobicity can delay and reduce soil water infiltration (Salifu et al., 2022) which could be beneficial in the context of slopes where failures are triggered by heavy rainfall and water infiltration.

This study explores various Basidiomycota fungal species, evaluating their potential to grow in diverse soil types under varying conditions, ranging from sterile to non-sterile environments. Growth patterns were monitored using time-lapse photography and image analysis techniques to determine the extent of growth over time within different soil compositions. Water Droplet Penetration Tests were conducted on specimens to evaluate how each fungal species influenced soil water repellency. Moreover, the impact of fungal growth on soil aggregation was evaluated using Soil-Aggregate Stability Tests. By correlating the growth patterns, water repellency, and soil aggregation outcomes, the most promising fungal species capable of enhancing soil stability and mitigating landslide risks in specific soil environments were identified.

References:

El Mountassir, G., et al. 2018. Applications of microbial processes in geotechnical engineering. Adv. Appl. Microbiol. doi: 10.1016/BS.AAMBS.2018.05.001

Froude, M. J. and Petley, D. N.: Global fatal landslide occurrence from 2004 to 2016, Nat. Hazards Earth Syst. Sci., 18, 2161–2181, https://doi.org/10.5194/nhess-18-2161-2018, 2018.

Haque, U., et al. 2016. Fatal Landslides in Europe, Landslides, doi: 10.1007/s10346-016-0689-3.

Salifu, E., El Mountassir, G. 2021. Fungal-induced water repellency in sand. Géotechnique. 71, 7. https://doi.org/10.1680/jgeot.19.P.341

Salifu, E., et al. 2022. Hydraulic behaviour of fungal treated sand, Geomechanics for Energy and the Environment, Volume 30.