Forest, fuel, and fire management strategies and decisions applied at the scale of forest stands influence not just the tree overstory but also understory plant composition and structure. Understory plants and forest floor materials constitute the surface fuels burned in prescribed fires. Airborne Light Detection and Ranging (LiDAR) remote sensing data is sensitive to the trees that comprise overstory tree structure, less sensitive to smaller midstory trees and saplings, and least sensitive to the understory shrubs, forbs, grasses, and dead plant material on the forest floor.
Eglin Air Force Base in Florida (186,350 hectare area) conserves a large reservoir of native longleaf pine stands that land managers highly value and maintain using frequent prescribed fires. They associated LiDAR data from Eglin with field plot data and fire management records, and they determined that understory structure and diversity characteristics are coupled to overstory tree density, basal area, and dominant tree species mapped from LiDAR. Understory plant diversity and surface fuel characteristics measured at 195 field plots were linked in a Geographic Information System to the map of Plot IDs. They applied a predictive modeling technique known as imputation that preserves the functional relationships between the field plot measurements, such as the number of understory plant species and several surface fuel components. Key Findings:
1. Understory characteristics and plant species diversity can be mapped using LiDAR data because they are functionally related to overstory structure. Such mapping can benefit forest, fuel, and fire managers of the Eglin Air Force Base.
2. Airborne LiDAR data explained half of the variation in tree density, basal area, and dominant tree species measured in 195 field plots, sufficient to develop an accurate predictive model.
The scientists report that surface fuel characteristics and understory plant diversity are coupled to the structure and composition of the overstory, as well as the frequency of fires prescribed by managers.