Analysis of the Relationship between Land Surface Temperature and Wildfire Severity in a Series of Landsat Images

Lidia Vlassova,Marcos Mimbrero,Raquel Llovería,Alberto García-Martín,Fernando Pérez-Cabello

doi:10.3390/rs6076136

Lidia Vlassova, Marcos Mimbrero + Show 3 more

Open Access

https://doi.org/10.3390/rs6076136

Copy DOI

Abstract

The paper assesses spatio-temporal patterns of land surface temperature (LST) and fire severity in the Las Hurdes wildfire of Pinus pinaster forest, which occurred in July 2009, in Extremadura (Spain), from a time series of fifteen Landsat 5 TM images corresponding to 27 post-fire months. The differenced Normalized Burn Ratio (dNBR) was used to evaluate burn severity. The mono-window algorithm was applied to estimate LST from the Landsat thermal band. The burned zones underwent a significant increase in LST after fire. Statistically significant differences have been detected between the LST within regions of burn severity categories. More substantial changes in LST are observed in zones of greater fire severity, which can be explained by the lower emissivity of combustion products found in the burned area and changes in the energy balance related to vegetation removal. As time progresses over the 27 months after fire, LST differences decrease due to vegetation regeneration. The differences in LST and Normalized Difference Vegetation Index (NDVI) values between burn severity categories in each image are highly correlated (r = 0.84). Spatial patterns of severity and post-fire LST obtained from Landsat time series enable an evaluation of the relationship between these variables to predict the natural dynamics of burned areas.

Highlights

Land surface temperature (LST) is one of the most important factors controlling physical processes responsible for the land surface balance of water, energy and CO2 [1,2,3]
Our results demonstrate that the land surface temperature (LST) increase in fire-affected areas was evident in the analyzed series of images, which cover all of the seasons of the two post-fire years, except winter
After the fire, the burned zones were, on average, 7.6 °C warmer than the unburned; the difference with the unburned areas was above 10 °C for the zones of high burn severity

Summary

Introduction

Land surface temperature (LST) is one of the most important factors controlling physical processes responsible for the land surface balance of water, energy and CO2 [1,2,3]. Burn severity, defined for the current study as the amount of change in a burned area with respect to the pre-fire conditions [10,11,12], is very dependent on fire intensity [13] and can be considered a key variable in understanding the spatial distribution of LST in the immediate post-fire environment [8]. The regrowth of vegetation is one of the most important factors controlling LST in the years following a fire, as vegetation cover and bare ground have different emissivity, defined as the ratio between the object emitting capacity and that of a blackbody at the same temperature. That is why spatio-temporal patterns of LST can help monitor the processes that structure ecosystem development and may assist in developing appropriate management strategies following forest fires

Objectives

Methods

Results

Conclusion