Comparison of Post-fire Patterns in Brazilian Savanna and Tropical Forest from Remote Sensing Time Series

Níckolas Castro Santana,Osmar Abílio De Carvalho Júnior,Renato Fontes Guimarães,Roberto Arnaldo Trancoso Gomes

doi:10.3390/ijgi9110659

Níckolas Castro Santana, Osmar Abílio De Carvalho Júnior + Show 2 more

Open Access

https://doi.org/10.3390/ijgi9110659

Copy DOI

Abstract

Monitoring of fire-related changes is essential to understand vegetation dynamics in the medium and long term. Remote sensing time series allows estimating biophysical variables of terrestrial vegetation and interference by extreme fires. This research evaluated fire recurrence in the Amazon and Cerrado regions, using Moderate Resolution Imaging Spectroradiometer (MODIS) albedo time series, enhanced vegetation index (EVI), gross primary productivity (GPP), and surface temperature. The annual aggregated time series (AAT) method recognized each pixel’s slope trend in the 2001–2016 period and its statistical significance. A comparison of time trends of EVI, GPP, and surface temperature with total fire recurrence indicates that time trends in vegetation are highly affected by high fire recurrence scenarios (R2 between 0.52 and 0.90). The fire recurrence and the albedo’s persistent changes do not have a consistent relationship. Areas with the biggest evaluated changes may increase up to 0.25 Kelvin/Year at surface temperature and decrease up to −0.012 EVI/year in vegetation index. Although savannas are resistant to low severity fires, fire regime and forest structure changes tend to make vegetation more vulnerable to wildfires, reducing their regeneration capacity. In the Amazon area, protection of forests in conservation units and indigenous lands helped in the low occurrence of fires in these sensitive areas, resulting in positive vegetation index trends.

Highlights

Fire is a natural agent present in most terrestrial biomes, contributing to the dispersion, evolution, and diversity of species, especially in biomes with intermediate primary productivity such as savannas [1,2]
This study aims to examine the post-fire impact in Amazon and Cerrado environments from remote sensing time series considering the following attributes: albedo, enhanced vegetation index (EVI), gross primary productivity (GPP), and surface temperature; and how these parameters behave over 15 years
This research presents the behavior of four biophysical variables for 15 years in different scenarios of fire recurrence in the Brazilian Amazon and Cerrado

Summary

Introduction

Fire is a natural agent present in most terrestrial biomes, contributing to the dispersion, evolution, and diversity of species, especially in biomes with intermediate primary productivity such as savannas [1,2]. The regions with high primary productivity, such as tropical forests, present a low natural fire occurrence because of their high humidity. Fire in savanna areas generally does not obey the natural fire regime, occurring mainly at the end of dry periods, when there is a higher probability of high-severity fires [5]. The albedo change from the burning is due to the ash’s vegetation cover, which directly influences the surface energy balance. Albedo changes are short-lived, changes in plant cover can cause albedo changes in the medium term, both in the increase of surface albedo in forest areas or the decrease in savannas, given the floristic differences [10,11]. The temperature directly correlates with the fire severity, biomass converted to ash and exposed soil area [12]

Objectives

Methods

Results

Discussion

Conclusion