Ladder Fuels

Ladder fuels are those that provide vertical continuity between understory or midstory surface fuels and canopy fuels. Ladder fuels consist of vine or liana fuels, draped foliage fuels, and hanging broken branches. Most surface fires in southeastern ecosystems involve isolated ladder fuels, though in particular circumstances ladder fuels can accumulate and lead to high severity fires.

Vine fuels include several southeastern species that are important in surface fires, such as yellow jessamine (Gelsemium sempervirens), greenbriers (Smilax spp.) and wild grape (Vitus spp.). Vines ascend trees and shrubs creating vertically continuous fuels. Dead and live foliage, stems, and flower structures have low fuel moisture, are bathed in convective heat, and contain volatile compoundscrown fires. Vine fuel availability is governed by fuel moisture, flame height, windspeed, and the live-to-dead ratio. Vine fuels are usually measured as presence/absence, height in canopy, vine loads, and live to dead ratios.

Draped dead foliage (especially pine needle litter) on vines and living or dead shrubs is another important ladder fuel type. Draped fuels have very low fuel moisture (wind, sun, and humidity effects are increased) and are highly flammable. Draped fuels increase the height of the combustion zone, linking understory and midstory fuels to canopy fuels. Southeastern pine plantations and long-unburned forested ecosystems with well-developed vine and/or shrub layers are especially prone to draping.

Hanging broken branches become important ladder fuels in forests following hurricanes, tornadoes, ice storms, and other disturbances.