View article

Fire is a common disturbance in tropical and temperate savanna and grassland ecosystems. The impact and intensity of fire are strongly influenced by available fuel loads, local plant community composition and structure. Invasion by exotic species in grasslands can alter fuel availability and contiguity and, consequently, influence several aspects of the fire regime such as intensity, frequency and spread. Woody invaders in grasslands, in particular, have the potential to alter fire regimes significantly as they have starkly different structural and physiological characteristics from the native grasses. In this study, we assessed how three woody invaders-Acacia mearnsii (black wattle, or wattle), Cytisus scoparius (scotch broom) and Ulex europaeus (common gorse, or gorse) impacted fire intensities in the montane grasslands of the Nilgiri Biosphere Reserve, in the southern Western Ghats, India. We used the differenced Normalized Burn Ratio (dNBR) as an index of fire intensity. Our results indicate that invaded areas burned at higher intensities than native grasslands. Fire intensities were highest in areas invaded by gorse, followed by black wattle and scotch broom. Fire relationships with long term landscape changes like invasion are currently understudied, and such studies highlight the cascading impacts for ecosystem dynamics like fire with such changes. We also find that such increases in fire intensities as a result of woody plant invasion can potentially have long term consequences for community and ecosystem processes in this landscape.