Post-fire resprouting strategies of rainforest and savanna saplings along the rainforest–savanna boundary in the Australian monsoon tropics

Abstract

In tropical areas where climatic conditions support both rainforests and savannas, fire is considered one of the main factors determining their distribution, particularly in environments where growth rates are limited by water availability. The observed expansion of some rainforests into savannas suggests that rainforest saplings could have traits that enable them to survive in the savanna environment, including recovering from infrequent fires. We applied the Clarke (New Phytol 197:19–35, 2013) buds-protection-resources framework to the rainforest–savanna system of the North Kimberley (Western Australia), to compare the resprouting response of five savanna species saplings burnt by an ambient early dry season fire with seven rainforest species saplings burnt using an experimental treatment that mimicked a savanna fire. Most plants survived the fire, although plant mortality was higher for rainforest (19 %) than savanna (2 %) individuals, as was stem mortality (37 vs. 12 %). All rainforest and savanna species expressed aerial resprouting; two of the savanna species and two of the rainforest species did not express basal resprouting. After 1 year, most savanna individuals had more and longer shoots than the rainforest saplings and had regained their original height, while rainforest plants were on average 43 % shorter than their pre-fire height. These results suggest that, although rainforest species are less able to escape the ‘fire trap’ than savanna species, they are able to recover from a low-intensity fire.