Abstract: Large areas of the sagebrush steppe are lost to fire, which catalyzes invasive species growth, increases soil nitrogen availability, reduces soil water retention, and disrupts soil symbiont-plant interactions. These changes in biogeochemical properties may explain why restoration success remains limited. Biochar is a soil amendment created from pyrolyzed plant biomass that may reduce soil N availability, and increase water retention and arbuscular mycorrhizal fungi (AMF) colonization. Our study aims to evaluate whether changing soil properties using biochar may enhance the survival of sagebrush seedlings.
We installed an experiment south of Boise, Idaho at a site that burned in 1983. Nursery-grown sagebrush seedlings were hand-planted in November 2021 and were amended with three biochar types that vary in particle size and chemical composition and a no biochar control (n=5). Treatments were applied in two areas, one was directly adjacent to the fire boundary exhibiting sagebrush seedling regrowth. The other was located farther away from the fire boundary and showed no sagebrush seedling recruitment. We analyzed planted seedling survival, soil C, pH, NO3- and NH4+, and AMF colonization on seedlings harvested after eight months. We used a general linear mixed model to analyze the effects of treatments on our response variables.
Biochar did not significantly affect seedling establishment, but we found that seedling survival was greater (+17 %) in the zone with natural sagebrush recruitment compared to the area with no recruitment. We also found significant differences in biogeochemical soil properties between the two zones. Soil pH, carbonates, and soil organic matter were significantly higher in the area closest to the unburnt sagebrush stand compared to the area located farther away. Our results indicate that soil biogeochemical properties in the area closest to the unburnt sagebrush stand that experienced recolonization by sagebrush may have favored survival of the sagebrush seedlings we planted. Together, our results indicate that changing soil properties due to succession after a fire have important impacts on late-successional species' success. These results can help land managers as they prioritize resource allocation toward ecosystem restoration projects.
