GENERAL FIRE EFFECTS

Within the last 50 years, new light has been shed upon fire's function within ecosystems.  Having always been considered harmful to the environment, the natural process of fire has been suppressed from much of the land due to human colonization.  Fire has become regarded as a natural and essential component to many ecosystems in the world for both its generative and destructive abilities (Pyne, 1982).  Prescribed fire reprises the role that natural, wide-sweeping fires once had on the landscape.  In order to conduct a prescribed burn in a safe and effective manner, one must attempt to understand fire's role in each natural community to be managed.  With thousands of different ecosystem types in the world, a large amount of variability exists among the effects that fire has, from the plant community down to the species level.  In order for land managers to effectively gauge the success of their prescribed fire program, the study of ecosystem response to these fires is a crucial portion of the planning and feedback process.

Many, if not all, of Florida's ecosystems were at one point in time fire-maintained.  Fire would burn through the community on an interval unique to that system.  For example, the fire interval range for pine flatwoods communities is 1 - 8 years (Florida Natural Areas Inventory, 1990).  This fire maintenance would reduce the height and amount of fuels and would provide the heat needed for species regeneration.  These species are considered fire-dependent.  They need the heat generated by fires to open their cones and the fuel reduction capabilities of fire to open up the ground cover and allow for the growth of native species.  Fire-dependent species are typically very flammable.  They not only allow for the quick spread of fire though the community but they also burn at higher temperatures, preventing the growth of other non fire-dependent species (Abrahamson and Hartnett, 1990).  These fire-dependent characteristics are fundamental to the survival of many plant communities in Florida.

Fire can behave differently and therefore have different effects on plant communities depending on many variables, including the weather.  One must take into account all variables when determining the effects a future prescribed burn may have on a particular plant community (Wade et al., 1980).  The following is a general list of effects that fire has been found to have upon the different components of a ecosystem.  This list was originally based on south Florida ecosystems but has been modified here to fit those in central Florida.  It should be noted that not all of the following occur in every ecosystem after every burn.

1. Fire influences the physical-chemical environment by:

• Releasing mineral elements as ash
• Volatilizing some nutrients
• Increasing insolation due to reduced plant cover
• Changing soil temperatures due to increased insolation