Fig 1.
The distribution of prescribed fires (yellow) from 2000–2019 in the Loess Canyons Biologically Unique Landscape in Nebraska.
The map inset shows the location of the Loess Canyons in the continuous USA, taken from the U.S. Department of Commerce [44]. States where Juniperus virginiana occurs are shaded green based on the USDA-NRCS PLANTS Database (https://plants.usda.gov/). Maps were generated using ArcGIS [45].
Table 1.
Summary of fuel models and their percent cover within the Loess Canyons.
Fuel models and descriptions are from Anderson, [53]. The percent cover of each fuel model type within the Loess Canyons and a surrounding 5 mile buffer were calculated using data from LANDFIRE [52].
Table 2.
Model parameters for calculating flame length values to be input into surface fire spotting distance models.
Table 3.
Fuel model parameters and justification for spot fire distance models.
Fig 2.
The difference in maximum spot fire distance under prescribed fire (0–32 km/h) versus wildfire (0–129 km/h) conditions relative to 3 different levels of juniper encroachment: The grassland state, a woody encroached grassland, and the woodland state.
Fig 3.
A comparison of maximum potential spot fire distance under prescribed fire (8 and 32 km/h) versus wildfire (8, 32, 64, 97, and 129 km/h) wind speeds relative to the grassland state (yellow), juniper encroached grasslands (orange), and the juniper woodland state (red) in the Loess Canyons Experimental Landscape.
Column 1 shows a landscape representation of changes in the potential exposure of receptive fuels relative to maximum spot fire distance from burn units in the Loess Canyons if they were all grassland (yellow), all juniper encroached grassland (orange), and all woodland (red). Column 2 focuses on changes in maximum spot fire distance relative to a single burn unit, where black lines represent the circumference of potential spot fire exposure and coloured lines represent the maximum spot fire distance if the burn unit was all grassland (yellow), woody encroached grassland (orange), or woodland (red). Column 3 lists maximum spot fire distances for each encroachment scenario. Green areas in maps represent receptive fuels and grey areas represent non-receptive fuels (urban areas, agriculture, water, barren areas) [52]. Maps were generated using ArcGIS [45].
Fig 4.
The change in receptive fuel area exposed to potential spot fire surrounding individual burn units in the Loess Canyons Experimental Landscape as juniper encroachment level and wind speed increase.