Abstract
Fires are a disturbance that can lead to short term dune destabilisation and have been suggested to be an initiation mechanism of a transgressive dune phase when paired with changing climatic conditions. Fire severity is one potential factor that could explain subsequent coastal dune destabilisations, but contemporary evidence of destabilisation following fire is lacking. In addition, the suitability of conventional satellite Earth Observation methods to detect the impacts of fire and the relative fire severity in coastal dune environments is in question. Widely applied satellite-derived burn indices (Normalised Burn Index and Normalised Difference Vegetation Index) have been suggested to underestimate the effects of fire in heterogenous landscapes or areas with sparse vegetation cover. This work assesses burn severity from high resolution aerial and Sentinel 2 satellite imagery following the 2019/2020 Black Summer fires on Kangaroo Island in South Australia, to assess the efficacy of commonly used satellite indices, and validate a new method for assessing fire severity in coastal dune systems. The results presented here show that the widely applied burn indices derived from NBR differentially assess vegetation loss and fire severity when compared in discrete soil groups across a landscape that experienced a very high severity fire. A new application of the Tasselled Cap Transformation (TCT) and Disturbance Index (DI) is presented. The differenced Disturbance Index (dDI) improves the estimation of burn severity, relative vegetation loss, and minimises the effects of differing soil conditions in the highly heterogenous landscape of Kangaroo Island. Results suggest that this new application of TCT is better suited to diverse environments like Mediterranean and semi-arid coastal regions than existing indices and can be used to better assess the effects of fire and potential remobilisation of coastal dune systems.
Highlights
IntroductionShifts in fire regimes (frequency and severity) are associated with climate change, extreme weather events, and drought [5,6,7,8], and may alter vegetation succession [9,10] or landscape stability [11]
Fires are an ordinary, recurring, and integral part of ecosystems around the globe and across many parts of Australia [1], and provide many benefits to ecosystems [2,3,4].Shifts in fire regimes are associated with climate change, extreme weather events, and drought [5,6,7,8], and may alter vegetation succession [9,10] or landscape stability [11]
The results show that differenced Disturbance Index (dDI) is less affected by soil brightness and corresponds to the absolute measures of greenness loss irrespective of varying canopy cover. dDI
Summary
Shifts in fire regimes (frequency and severity) are associated with climate change, extreme weather events, and drought [5,6,7,8], and may alter vegetation succession [9,10] or landscape stability [11]. Measurements of fire severity provide data that can be used to better understand the subsequent postfire recovery, such as shifts in ecological diversity or stability of the landscape [14,15]. Significant research has been applied to mapping and understanding fire severity from space [16], but many conventional methods are influenced by soil conditions and prevegetation communities, or require region-specific adjustments, thresholds, or training data [17,18,19,20], which limit their wider application. The forecast of fires in Australia and globally shows a continued increase in frequency and intensity with extended
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