Post-fire shifts in vegetation composition or successional trajectory will have broad impacts for carbon storage, hydrology, nutrient cycling, and wildlife habitat. However, information characterizing post-fire recovery patterns and their drivers is lacking over large spatial extents. Researchers tracked dual-season rates of post-fire recovery for more than 12,500 burned points across the western United States. Landsat imagery collected when snow cover (SCS) was present was used in combination with growing season (GS) imagery to distinguish evergreen vegetation from deciduous vegetation. The analysis sought to (1) identify spatial and temporal patterns in the rate of post-fire recovery across the western United States, (2) relate remotely sensed patterns to plot-scale, field-measured patterns of post-fire re-vegetation, and (3) model variability in post-fire rates of recovery as a function of burn severity, site conditions, and climatological factors.
The post-fire recovery under snow cover was indicative of evergreen regeneration, while the rate of recovery in the growing season primarily represented understory vegetation (grass, herbaceous, shrubs). Furthermore, the rates of recovery in the growing season were only weakly correlated with the rates of recovery under snow cover. The seasonal distinction in vegetation type had important implications for understanding the drivers of post-fire recovery. Although temperature was important in both seasons, the seasons showed opposite directionality, with warmer conditions associated with faster rates of evergreen regeneration and cooler conditions associated with faster rates of deciduous recovery. The temperature finding suggests that in snowy, mountainous areas, conifer regeneration may react differently to warming temperatures compared to deciduous species. Efforts that use both growing season and snow cover Normalized Difference Vegetation Index to evaluate post-fire recovery can help guide predictions of where active vegetation management should be focused at the scale of the western United States. This approach provides a powerful tool to inform landscape-scale, post-fire analysis and monitor long-term impacts of fires on ecosystems across the West.
The rate of post-fire recovery, defined using the Normalized Difference Vegetation Index (NDVI), by forest type and season (growing season [GS] and snow cover season [SCS]) including (a) Douglas fir (GS), (b) Douglas fir (SCS), (c) Ponderosa pine (GS), (d) Ponderosa pine (SCS), (e) California mixed conifer (restricted to California) and pinyon–juniper woodland (Nevada, Utah, Colorado, Arizona) in GS, and (f) California mixed conifer and pinyon–juniper woodland (SCS). Blue represents rapid post-fire recovery, yellow represents slow post-fire recovery, and red represents no post-fire recovery.