Prediction of Forest Canopy and Surface Fuels from Lidar and Satellite Time Series Data in a Bark Beetle-Affected Forest

Benjamin Bright,Andrew Hudak,Todd Hawbaker,Arjan Meddens,Jennifer Briggs,Robert Kennedy

doi:10.3390/f8090322

Abstract

Wildfire behavior depends on the type, quantity, and condition of fuels, and the effect that bark beetle outbreaks have on fuels is a topic of current research and debate. Remote sensing can provide estimates of fuels across landscapes, although few studies have estimated surface fuels from remote sensing data. Here we predicted and mapped field-measured canopy and surface fuels from light detection and ranging (lidar) and Landsat time series explanatory variables via random forest (RF) modeling across a coniferous montane forest in Colorado, USA, which was affected by mountain pine beetles (Dendroctonus ponderosae Hopkins) approximately six years prior. We examined relationships between mapped fuels and the severity of tree mortality with correlation tests. RF models explained 59%, 48%, 35%, and 70% of the variation in available canopy fuel, canopy bulk density, canopy base height, and canopy height, respectively (percent root-mean-square error (%RMSE) = 12–54%). Surface fuels were predicted less accurately, with models explaining 24%, 28%, 32%, and 30% of the variation in litter and duff, 1 to 100-h, 1000-h, and total surface fuels, respectively (%RMSE = 37–98%). Fuel metrics were negatively correlated with the severity of tree mortality, except canopy base height, which increased with greater tree mortality. Our results showed how bark beetle-caused tree mortality significantly reduced canopy fuels in our study area. We demonstrated that lidar and Landsat time series data contain substantial information about canopy and surface fuels and can be used for large-scale efforts to monitor and map fuel loads for fire behavior modeling at a landscape scale.

Highlights

Wildfires and other forest disturbances such as insect outbreaks and drought cause widespread forest mortality across the western United States [1,2,3]
Our results showed that canopy and surface fuels fuel be maps to an independent assessment forest mortality to assess relationships fuels and can predicted from lidar and Landsat of time series data with moderate accuracy.between
Our results showed that canopy and surface fuels can be predicted from and could be used to improve fuel maps, fire behavior modeling, and programs like LANDFIRE.lidar

Summary

Introduction

Wildfires and other forest disturbances such as insect outbreaks and drought cause widespread forest mortality across the western United States [1,2,3]. Many aspects of wildfire behavior and effects are greatly influenced by forest fuels [9,10], which are shaped by prior disturbances such as insect epidemics, drought, fire, and disease. Spatially-explicit estimates of forest fuels and the effect of insect-caused tree mortality on fuels can serve as valuable information for forest managers and researchers in their efforts to predict and mitigate the effects of future fire. Forest canopy fuels are commonly characterized with several parameters important to predicting fire behavior [11]. Available canopy fuel (ACF) is defined as fuel capable of burning in a crown fire, and includes foliage and small branches. Downed dead wood (DWD) surface fuels are often defined by how quickly they will reach a new moisture equilibrium, which is a function of their surface area/volume ratio

Methods

Results

Discussion

Conclusion