Improving Erosion Resistance and Revegetation of Wildfire-Altered Soils Using Microbial Induced Calcite Precipitation

Climate change is causing wildfires to occur more frequently and with higher intensity. Leading to wide range of impacts on agriculture, infrastructure, and the environment. Wildfires affect soils by burning their organic matter, resulting in an immediate deplete of nutrients and a significant reduction in nitrogen level. Wildfires also alter soils’ physical properties and make them less resistant to erosion which results in debris flows when wildfire are followed by a rainfall event. The reduced activity of microorganisms that aid in nutrient absorption makes the soil less effective in supporting plant life. Microbial Induced Calcite Precipitation (MICP) was found to be a sustainable treatment method for enhancing soil stability and reducing erodibility. MICP employs naturally existing microorganisms to precipitate calcium carbonate, which binds soil particles together. However previous studies mainly focused on using sporosarcina in regular soils, not in post-fire conditions. Further research is necessary to assess its effectiveness in soils affected by wildfires. In this research study, MICP was used to treat burned soil, where the efficacy of the treatment was measured by testing the treated samples for their shear strength, erodibility resistance and plants capacity to support vegetation. Soil samples were collected and burned to simulate wildfire conditions. The soil was mainly sandy, with a small percentage of fines and an organic content of 5-7%. Test results showed that the burned soils had decreased shear strength and erosion resistance compared to unburned natural soil. Shear strength was evaluated using Direct Shear test, erodibility was assessed with an erosion box that was designed for this research, under two different water heights of 37 and 18 cm. The improvement in vegetation recovery plant growth was evaluated based visually on the MICP treatment. For burned samples, the friction angle was reduced from 35- 38° to 23°, and erosion rates increased from 0.21-0.22 mm/sec to 0.87-0.91 mm/sec at a water height of 37 cm, and from 0.23-0.25 mm/sec to 0.79-0.87 mm/sec at an 18 cm water height. MICP treatment resulted in an increase in friction angle up to 36° after one-week treatment, and up to 37° after two- week treatment. After one week of treatment, erosion rates decreased to 0.2-0.23 mm/sec and 0-0.3 mm/sec at water heights of 37 cm and 18 cm, respectively. After two weeks of treatment, erosion decreased to negligible rates at both water heights. These results suggest that the MICP treatment can be considered a sustainable method for stabilizing wildfire-affected soils, improving their shear strength, erosion resistance and vegetation recovery. Future efforts will focus on optimizing the MICP treatment protocol targeted for large-scale sections and field implementation.