DUET-Distribution of Understory using Elliptical Transport: A mechanistic model of leaf litter and herbaceous spatial distribution based on tree canopy structure

Heterogeneity in surface fuels produced by overstory trees and understory vegetation is a major driver of fire behavior and ecosystem dynamics. Previous attempts at predicting tree leaf and needle litter accumulation over time have been constrained in scope to probabilistic models that consider a limited number of key factors influencing tree litter dispersal patterns and decomposition processes. We present a mechanistic model for estimating variation in surface fuels called the Distribution of Understory using Elliptical Transport (DUET). DUET uses a pre-generated voxelated canopy array and distributes the leaf litter from the trees in an elliptical shape based on tree species characteristics, wind data, and location-specific features. DUET then calculates grass growth between trees and around the litter patterns and sets moisture levels based on relative humidity. In this study, we use DUET to simulate spatial distributions of leaf litter and illustrate model sensitivity to several parameters, providing inputs for testing fuel spatial heterogeneity impacts on fire behavior using process-based models.

Automated summary

Heterogeneity in surface fuels, influenced by tree leaf and needle litter accumulation, is important for understanding fire behavior and ecosystem dynamics. A new model called DUET is presented, which estimates variation in surface fuels by considering tree species characteristics, wind data, and location-specific features. The model simulates spatial distributions of leaf litter and grass growth, and sets moisture levels based on relative humidity. This model provides inputs for testing the impact of fuel spatial heterogeneity on fire behavior using process-based models.