Forest restoration in Eastern Madagascar: Post-fire survival of select Malagasy tree species

Abstract

As fire becomes more common in rainforests due to climate change, understanding rainforest tree species’ tolerance to fire becomes increasingly important. Madagascar’s northeast coast is particularly vulnerable to fire given the 20th century invasion of Dicranopteris linearis fern that is extremely flammable, promoting its own dominance in this region. The objective of the study was to investigate which Malagasy tree species were better able to survive a fire disturbance and under what conditions. We planted 4,000 trees of 11 different Malagasy tree species in 160 small monoculture islands consisting of 25 trees each. At this time, we recorded site conditions such as fuel depth, slope, sapling height, and position within the island. Just after the wildfire we scored the intensity and severity of the fire at each of the 4,000 saplings. Several months later during the rainy season, we returned to each of the 4,000 saplings and recorded survival. We found that choice of species and low perimeter:area ratio planting designs are two of the most important factors that determined sapling survival of a wildfire. The timing of outplanting was the third most important choice that required species-specific knowledge of the relative importance of larger sapling size and days of establishment to harden in the field. A number of diverse life history traits also emerged that described how each species was able to survive wildfire. We categorized these into three broad categories: retardance, resistance, resilience. For restoration practitioners worldwide who work amidst highly flammable fuels, our results suggest that at the time of outplanting careful planning for the possibility of subsequent fire disturbances can greatly increase the chance of the project reaching maturity.