Abstract: Western forest regeneration failure is linked to persistent drought conditions, reduced soil moisture, and increased distance to seed sources due to increasingly large areas burned at high severity. As climate conditions continue to become less suitable for forest regeneration and wildfire activity increases in size, severity, and frequency in the western United States, points on the landscape that provide suitable regeneration conditions are increasingly important to avoid loss of ecosystem services. Springs provide increased soil moisture and may act as important ecosystem regeneration foci. The emergence of groundwater produces cooler, wetter microclimate conditions, increasing soil moisture, and potentially reducing burn severity during wildfires. Such conditions may preserve seed banks and enhance regeneration. Additionally, the combination of increased solar radiation due to decreased canopy cover and persistent soil moisture provide suitable conditions for germination and growth following wildfire. Despite the alignment between conditions at springs and requirements for post-fire ecosystem regeneration, minimal prior investigation and quantification of the role of springs as regeneration foci and fire refugia have been conducted, limiting understanding of spring ecosystems response to wildfire and post-fire forest regeneration.
The goal of this research is to synthesize emerging knowledge of spring ecosystem response to wildfire. This presentation will summarize new insights from three ongoing investigations in Arizona, California, and Idaho into spring ecosystem response to wildfire within five response domains including geomorphologic impacts, water quantity and quality, habitat changes, biotic impacts, and ecosystem functionality. The study in central Idaho quantified the pattern of conifer regeneration around 20 springs using belt transects stratified by environmental variables influencing regeneration. Data collection along transects included soil burn severity, confer seedling density, age, distance to live seed source, and height. An analysis of 16 pre- and post-fire springs in central eastern Arizona and 120 springs near Yosemite National Park in California revealed highly variable fire impacts but rapid regrowth of herbaceous wetland vegetation, with ecosystem trajectory changes related to reduced shading by forest canopy. Preliminary results from these studies show new insights into each response domain including increases in discharge and filtration with loss of forest vegetation, enhanced plant species diversity with decreased canopy shading, persistence of seed bank due to lower burn severity, increased ungulate and predator use, and substrate distribution change leading to altered habitat use. The cumulative response of spring ecosystems to wildfire in each of these domains points to spring ecosystems as important regeneration foci with landscape-scale implications.
