Increasing Giant Sequoia Reforestation Success after Catastrophic Wildfire Using Soil and Microbial Indicators

Ancient groves of giant sequoia trees inspire people all over the world. Recently, however, unprecedented droughts and wildfires in California have killed 13-19% of mature sequoia trees. In severely burned areas, it is uncertain if natural seedling regeneration will be enough to restore the groves. While replanting efforts will occur, seedling success depends largely on sufficient soil moisture. Beneficial microorganisms in the soil can enhance drought resistance and increase growth in many tree species, but wildfires also change microbes and soils in ways that could either help or harm sequoia seedlings. The effects of post-fire soil and microbial conditions on sequoia seedlings, and whether those conditions can be manipulated to increase growth and survival, has not been tested. 

This project aims to find simple ways to improve sequoia seedling success. By analyzing soils and microorganisms associated with seedlings, this research team will: (1) assess whether natural variations in soils and microorganisms are related to wildfire severity and soil moisture, and (2) determine if manipulating soil conditions or microbial communities during seedling propagation improves their growth and survival in severely burned areas. The work will guide land managers in selecting effective strategies to increase seedling survivorship and identify areas where seedlings are most likely to survive. 

As fires become more frequent and severe, and precipitation patterns become less predictable, land managers need strategies that help sequoia seedlings thrive, and forests regrow, under increasing environmental stress. Results from this project will classify giant sequoia groves by terrain indices, evaluate wildfire impacts on soils and microbes, and assess the effectiveness of microbial and soil treatments for improving seedling success in burned groves. This project will produce scientific publications, a digital product for the National Park Service (NPS) application, a final report, and a factsheet.