Data from: Wildfire disturbance and ecological cascades: teasing apart the direct and indirect effects of fire on tick populations

Wildfires are a significant ecological force in the western United States,
reshaping landscapes and ecological communities. However, assessing
wildfires full impact is challenging due to the complexity of fire
severity and its varied effects on ecological dynamics. Understanding
species-specific responses to disturbances within their environmental
context is essential for predicting cascading ecological impacts.
Arthropods, including ticks, are particularly sensitive to both abiotic
and biotic changes, making them especially vulnerable to the impacts of
wildfire. In this study, we tease apart the complex direct and indirect
effects of wildfire on tick populations through a combination of
field-level measurements and remote sensing. We assessed tick densities
across 88 plots within large, protected reserves in California following
three wildfires in August 2020, using data on soil conditions, vegetation
cover, tick densities, and landscape-level remotely sensed variables
related to vegetation regeneration and vertebrate recolonization. To
support a multi-scalar approach, we applied piecewise structural equation
models (SEMs) to incorporate factors across distinct spatial scales and
assess how fire severity affects tick populations, with vegetation and
habitat structure as mediating variables, thereby evaluating the relative
importance of local drivers within a broader landscape context. Our
results indicate that tick densities were consistently lower in burned
plots across all vegetation types, with higher fire severity associated
with the greatest reductions. This direct effect of fire severity
outweighed indirect influences such as the presence of remaining woody
debris, which can support tick populations by offering microhabitat for
vertebrate hosts following a fire event. Landscape-level characteristics –
such as proximity to the fire perimeter and the percentage of the reserve
burned – exerted stronger influences on tick densities than plot level
fire severity. These broader spatial characteristics likely facilitate the
movement of vertebrate hosts into unburned areas, promoting tick
recolonization and recovery following wildfire disturbance. Our results
suggest that simplified field assessments focusing on key habitat
indicators may be effective for monitoring tick responses to wildfire.
Synthesis and applications: This study highlights the importance of
integrating multiple data sources and ecological scales to predict
wildfire impacts on ecosystems and public health. By advancing our
understanding of wildfire effect on ticks, the research offers valuable
insights for ecosystem management and disease vector control. The use of
advanced statistical tools, like piecewise SEMs, combined with remotely
sensed data, can facilitate rapid assessments and targeted monitoring
efforts.