Examining post-fire vegetation recovery with Landsat time series analysis in three western North American forest types

Benjamin C Bright,Andrew T Hudak,Azad Henareh Khalyani,Robert E Kennedy,Justin D Braaten

doi:10.1186/s42408-018-0021-9

Benjamin C Bright, Andrew T Hudak + Show 3 more

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https://doi.org/10.1186/s42408-018-0021-9

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Abstract

BackgroundFew studies have examined post-fire vegetation recovery in temperate forest ecosystems with Landsat time series analysis. We analyzed time series of Normalized Burn Ratio (NBR) derived from LandTrendr spectral-temporal segmentation fitting to examine post-fire NBR recovery for several wildfires that occurred in three different coniferous forest types in western North America during the years 2000 to 2007. We summarized NBR recovery trends, and investigated the influence of burn severity, post-fire climate, and topography on post-fire vegetation recovery via random forest (RF) analysis.ResultsNBR recovery across forest types averaged 30 to 44% five years post fire, 47 to 72% ten years post fire, and 54 to 77% 13 years post fire, and varied by time since fire, severity, and forest type. Recovery rates were generally greatest for several years following fire. Recovery in terms of percent NBR was often greater for higher-severity patches. Recovery rates varied between forest types, with conifer−oak−chaparral showing the greatest NBR recovery rates, mixed conifer showing intermediate rates, and ponderosa pine showing slowest rates. Between 1 and 28% of patches had recovered to pre-fire NBR levels 9 to 16 years after fire, with greater percentages of low-severity patches showing full NBR recovery.Precipitation decreased and temperatures generally remained the same or increased post fire. Pre-fire NBR and burn severity were important predictors of NBR recovery for all forest types, and explained 2 to 6% of the variation in post-fire NBR recovery. Post-fire climate anomalies were also important predictors of NBR recovery and explained an additional 30 to 41% of the variation in post-fire NBR recovery.ConclusionsLandsat time series analysis was a useful means of describing and analyzing post-fire vegetation recovery across mixed-severity wildfire extents. We demonstrated that a relationship exists between post-fire vegetation recovery and climate in temperate ecosystems of western North America. Our methods could be applied to other burned landscapes for which spatially explicit measurements of post-fire vegetation recovery are needed.

Highlights

Few studies have examined post-fire vegetation recovery in temperate forest ecosystems with Landsat time series analysis
Random forest analysis We explored the relationship between climate, topography, and post-fire Normalized Burn Ratio (NBR) recovery by relating percent NBR recovery nine years post fire to post-fire climate anomaly and topographic variables (Table 2) via random forest (RF) modeling, implemented in R (Breiman 2001; Liaw 2002; R Core Team 2017)
We described post-fire vegetation recovery using NBR time series, and related post-fire climate and topographic variables to NBR recovery for 12 fires that occurred in temperate ecosystems of western North America

Summary

Introduction

Few studies have examined post-fire vegetation recovery in temperate forest ecosystems with Landsat time series analysis. We analyzed time series of Normalized Burn Ratio (NBR) derived from LandTrendr spectral-temporal segmentation fitting to examine post-fire NBR recovery for several wildfires that occurred in three different coniferous forest types in western North America during the years 2000 to 2007. The degree to which fire has affected vegetation and soil (Keeley 2009), can have a large influence on post-fire vegetation recovery (Chappell 1996; Turner and Romme 1999; Crotteau and Varner III 2013; Meng et al 2015; Liu 2016; Yang et al 2017; Meng et al 2018). Long-term measurements of post-fire vegetation recovery for differing forest types and burn severities can provide useful information to researchers and land managers who seek to identify areas that could benefit from post-fire management. Good correlation has been found between ground estimates of burn severity and the differenced Normalized Burn Ratio (dNBR; van Wagtendonk et al 2004, Key 2006, Hudak et al 2007, Keeley 2009) NBR is defined as: NBR

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