Fire Management and Melaleuca Swamps

Melaleuca (Melaleuca quinquenervia), an invasive, non-native tree originating in Australia, has become well established in south Florida where it invades both disturbed sites and intact natural communities. Melaleuca is well adapted to fire and flooding, both of which are driving processes in the ecosystems of south Florida. Introduced in the early 1900’s it has quickly spread and covered almost a half million acres in south Florida as of 1993. The limiting factor in establishment seems to be adequate soil moisture to allow seedling establishment without prolonged flooding that causes seedling death. Once established melaleuca survives under a variety of moisture regimes regardless of soil type. Infestations tend to start as single outlier trees that become dense monocultures over time displacing native plants and animals. Animals do use melaleuca stands, but to a lesser extent than native habitats.

Melaleuca is extremely well adapted to fire. Thick bark and the ability to sprout from anywhere on the stem or branches not killed by fire provide the ability to recover after even intense fires. Fires also release large quantities of minute seeds from serotinous capsules into a fire prepared seedbed. Only the smallest individuals are killed by fire, often for only 1 year following germination or until saplings reach 1 m in height.

Melaleuca has altered the fire regime of south Florida by altering fire behavior. Melaleuca foliage is extremely flammable due to the arrangement of foliage and to its chemical content. The papery bark of melaleuca acts as a ladder fuel carrying fires into the canopy. Dense melaleuca stands are the only vegetation type in south Florida that will support and perpetuate crown fires. Native vegetation often succumbs to the intense crown fires that melaleuca supports. Canopy species such as pine and cypress, though adapted to surface fires, are often top killed by intense melaleuca crown fires and subsequently outcompeted.

Prescribed fire managers charged with maintaining the health of Florida’s natural communities must continue burning, but must take measures to prevent fire from accelerating the spread of melaleuca. This approach is most effective if it is aimed at containing starting infestations (i.e., scattered melaleuca within natural lands). Fire can be used as one of several tools to help control melaleuca if applied judiciously. Fire managers must avoid fire triggered seed release into fire prepared seedbeds. Instead, fire managers must use an alternate method, often herbicides, to trigger seed release into intact fuel beds and subsequently burn seedlings and saplings while they are in a fire-susceptible stage. Fire is not a recommended management tool for dense melaleuca stands.