Fire plays a natural role in determining how the various habitats exist. They may change through time in response to changing conditions of temperature and moisture and other factors. The habitats can be described within a range of natural variation and these parameters are partly defined by the role that natural fire takes.
Looking at the landscape in the absence of modern human mechanical intervention, but including the possible influence of aboriginal fire use, a classification of natural fire regimes is produced.
Fire factors involved in determining these regimes include the average number of years between fires which is basically the fire frequency or mean fire interval. This could take a significant amount of data covering a fairly lengthy time period to determine reliable figures.
The severity of the fires will also influence the resulting habitat. One way to measure the severity is the percentage of replacement. A totally even age stand would indicate that the previous fire was severe enough to eliminate the previous stand regardless of however mixed the ages were.
Effects Of Fire Suppression
Of course, the various studies did not take place before the start of fire suppression. Scientists thus have to take into account that for many decades fire suppression has made the forests vary from normal.
But once the base level of fire conditions under natural conditions is determined, scientists can start determining how far from those levels a particular forest is today. This difference from normal fire regime to present day conditions is the key.
Vegetation conditions, species composition, structural stage, stand age, canopy closure, mosaic pattern, fuel composition, fire frequency, severity, fire pattern, insect and disease mortality, grazing, drought, fire suppression, timber harvest, and introduction and establishment of exotic species are all parameters in which the forest can vary.
Prescribed Fire - Getting Back To Normal
When all these conditions are taken into consideration, the use of prescribed fire can then be used to take the forest from present conditions to the condition it would most likely be in today if fire had been allowed to play its natural role over the intervening years. After all the forest and all its species have adapted to surviving under natural conditions and those conditions have included fire.
It was not until fire was thought of as destructive for a period of time and was thus suppressed that there were the deviations from normal. Now we realize that we must live with nature instead of trying to control nature.