Fire, frost and alternative biome states in Asia

The dry tropics is an important but overlooked region spanning Latin America, Africa, Asia and Australia. It supports a huge proportion of the world’s population and experiences intense human pressure across much of its range. It is characterised by savannas and mosaic landscapes where trees and grasses co-exist under the same climate and experience frequent disturbance, most commonly through fire or herbivory. Biomes and alternative biome states are important concepts in understanding vegetation distribution and dynamics and the persistence of mixed tree-grass systems through time into a warmer, more extreme and higher CO2 future . Forest-centric colonial legacies in the tropics confused terminology and the varied appearance and complex non-linear behaviour of these landscapes have combined to make them under-valued, mis-represented and misunderstood, particularly in Asia. Tropical montane landscapes - disproportionately important in the ecosystem services they provide and the diversity they hold and especially vulnerable to the impacts of climate and land-use change - suffer the most from this want of data. Fire is widely recognised for its role in maintaining open, grassy vegetation and frost has been reported as important in high elevation systems. However, it is not well known how these processes interact to influence vegetation structure and function and their relative importance across elevation, nor what the impacts of climate change will be. Given these unknowns my project aims to improve our understanding of Asia’s dry tropics, first by illustrating through a comparison of historical vegetation maps and classifications what we don’t know and therefore highlighting the need for an updated and more modern understanding of tree-grass distributions. Using newly available, high resolution remote sensing tools I will focus on this need by mapping the distribution of tree-grass mosaics across the continent’s dry tropics and by examining vegetation patterns across space and in response to disturbances such as fire. I will then focus on plot-based investigations along an elevational gradient in the Western Ghats in India, an example of a stable and persistent tree-grass mosaic to gain a more detailed and nuanced understanding of the role of fire and frost in structuring vegetation and what the likely impacts of climate change will be on these montane landscapes.