Oral Presentation Society for Freshwater Science 2026 Annual Meeting

Unraveling drivers of variation in riparian vegetation recovery following wildfire (136032)

Leah Simantel 1 , Kellie J Carim 2 , Sean A Parks 2 , Lisa A Eby 1
  1. Ecosystem & Conservation Science, University of Montana, Missoula, MT
  2. Aldo Leopold Wilderness Research Institute, Missoula, MT

The effects of fire on stream ecosystem processes and aquatic fauna are highly variable. This variation is, in part, explained by the extent and severity of the burn, as well as the time lag of the sampling and the fire event1. Despite extensive research on fire effects on vegetation and post-fire recovery in terrestrial landscapes2,3, comparatively little is known about how riparian vegetation responds to fire and what factors influence recovery. A better understanding of processes influencing riparian recovery is needed to link the effects of wildfire to stream ecosystems.

This study examined topographic, climatic, and wildfire-related drivers of riparian recovery in watersheds of the Bob Marshall Wilderness Area (Montana) using Landsat Normalized Difference Vegetation Index (NDVI) data spanning 1984-2024. We quantified changes in vegetation as the difference between pre-fire and post-fire greenness (ΔNDVI) for individual Landsat pixels in riparian areas up to 20 years post-fire. Fire severity strongly influenced riparian ΔNDVI during the three years following fire, with moderate and high-severity sites exhibiting significantly reduced greenness compared to low-severity and unburned controls. Even though differences in ΔNDVI among fire severity groups diminished over time, ΔNDVI remained significantly lower in sites that burned at high-severity relative to unburned sites 20 years post-fire. Approximately 90% of high-severity pixels achieved pre-fire levels after 19 years, compared to 16 and 3 years for moderate- and low-severity pixels, respectively.

We used random forest models to assess the influence of fire severity, site specific indices for vegetation type, soil moisture, immediate post-fire drought conditions, and annual seasonal climate variables (snowpack, summertime temperature and precipitation) on riparian recovery. Though all covariates were influential, fire severity was the strongest driver. Seasonal climatic variables influenced ∆NDVI at all time points, but their effect sizes and directional relationship varied with time since fire. These results improve our understanding of fire impacts on riparian zones and the multi-decadal influences on variation in riparian recovery, highlighting the importance of long-term studies to understand legacy impacts associated with wildfire disturbance.

  1. Erdozain, M., Cardil, A., & de-Miguel, S. (2024). Fire impacts on the biology of stream ecosystems: A synthesis of current knowledge to guide future research and integrated fire management. Global Change Biology, 30, e17389.
  2. Hao, B., Xu, X., Wu, F., & Tan, L. (2022). Long-Term Effects of Fire Severity and Climatic Factors on Post-Forest-Fire Vegetation Recovery. Forests, 13(6), 883.
  3. Kurbanov, E., Vorobev, O., Lezhnin, S., Sha, J., Wang, J., Li, X., ... & Wang, Y. (2022). Remote sensing of forest burnt area, burn severity, and post-fire recovery: A review. Remote Sensing, 14(19), 4714.