Analysis of the Correlation between Curing and Moisture Content in Australia Grasslands with MODIS-based Observations

Abstract

Fire is common in Australia grasslands, and it is becoming more frequent and serious due to climate change. Fire has significant impacts upon economy, human-health and ecology, so the management of bushfire is important. Degree of curing (C) and fuel moisture content (FMC) are applied as input variables in different fire prediction models in Australia to evaluate fuel conditions. Indirect satellite observations of FMC are based on the assumption that FMC is related to C. Studying the relationship between C and FMC helps understand fuel dynamics, improve fire prediction model and spectral indices. The relationship between C and FMC has been intensively discussed, despite of different options. Instead of field observation used in previous studies, C and FMC derived from satellite-based observation would be applied in this analysis. In this thesis, C and FMC estimated at a large-scale with high spatial resolution and temporal resolution were compared to study their relationship. Using satellite-observed C and FMC data, this study investigated the relationship between C and FMC across grasslands in Australia and over a time series. Moreover, this study aimed to investigate the relationship between C and FMC at smaller-scale to examine the influences of grass species, seasonal change, and fire histories on the correlation between C and FMC. It was hypothesised that there would always be a negative linear relationship between C and FMC in Australian grasslands regardless of grass species, fire history, or seasons. Results of this study confirmed that there were strong negative linear correlations between C and FMC across Australian grasslands; however, in different grasslands the correlation coefficients varied. The correlation between C and FMC was influenced by grass species, previous fire events, and seasonal change. In blue grass (Dichanthium) and tall bunch grass (Chrysopogon) tussock grasslands, temperate tussock grasslands, other tussock grasslands, and non-native grasslands, C and FMC had a very strong negative linear correlation. In other types of grasslands, the correlation between C and FMC was weaker. In areas with frequent fire events and during the extreme dry or rainy seasons, the correlations between C and FMC were also weaker. This study implicates that the correlation between C and FMC is grass species specific, so fire prediction models should also be developed using various grass species. Strong correlation between C and FMC in southern grasslands except for sedgelands, rushes, or reeds, confirmed that it is suitable to evaluate fuel condition by C. FMC data should be included in fire prediction models for grasslands that do not have very strong significant correlations between C and FMC. Spectral indices that focused on the contrast between red and NIR were questioned by this study because C and FMC were not always very strongly negatively correlated in grasslands in Australia. Show more