Fire Regime Changes and Melaleuca

Melaleuca is a true fire-type species. It not only persists and reproduces after fire, but its presence promotes fire. Melaleuca foliage is highly flammable. It contains volatile oils that promote burning. The papery bark of melaleuca acts as a ladder fuel that can carry fire into the canopy. Further, the arrangement of aerial fuels can create intense crown fires. The bark can also act as a firebrand as it is transported in the smoke plume starting spot fires (Wade 1981).

Melaleuca stands have created a novel fire environment in south Florida. Dense melaleuca stands are the only vegetation type in South Florida that will support a crown fire. Melaleuca stands have been characterized as having a mixed fire regime, i.e., able to support a high intensity fire with low mortality (Myers 2000). In addition, melaleuca stands can support a variety of fire behaviors ranging from low intensity surface fires after which little seed is released to high intensity crown fires after which huge amounts of seed are released (Myers 2000, Wade1981). Vegetation adapted to the natural fire regime in South Florida, one of frequent surface fires, does not fare well with the addition of crown fires. High intensity crown fires often kill pine or cypress in forested communities invaded by melaleuca. Dense stands of melaleuca shade out herbaceous vegetation and reproduction from other canopy species (Myers 1983) (Wade et al. 1980).

Melaleuca tends to perpetuate itself. Crown fires create a sunny environment on the forest floor by removing the canopy. Melaleuca has been found to germinate better in sun than in shade (Meskimen 1962). In addition, loss of foliage reduces transpiration, thereby increasing soil moisture, which is a requirement for successful melaleuca establishment. Established trees then resprout (Wade 1981). Elimination of native vegetation and creation of nearly monospecific melaleuca stands results.