Fire as a Tool in Habitat Management is also necessary for maintaining them in their savannah state. Their structural complexity and species composition are also influenced by the severity of the annual fires. Fire can be caused by some natural phenomena and by man consciously or inadvertently through his actions. Most of the semi-natural savannah owes their origin to fire.
Fire is an important tool in the management or range lands and livestock, and in the control of the ecto-parasites of livestock. It is equally important in wildlife management.
It should be pointed out that even though effects of the fires caused by lightning, volcanic eruptions and sparks from rock boulders may be significant in natural ecosystems, they are relatively milder in their destructive effects and spread than the man causing fires.
Man deliberately sets fire to vegetation to prepare land for cultivation, to flush out animals during hunting expeditions, to remove old unpalatable growth while promoting new flush, to control bush and encroachment of range land by woody species and to destroy parasites.
You should know that fire is a good servant but a bad master. Therefore, the use of fire must be adopted with adequate consideration of fire break.
The Range of Fire Effects in Habitat Management
According to Rogers (1979) fire can affect the following environmental variables either directly or indirectly:
l. Soils by
a. Affecting numbers and rate of activity of soil organisms.
b. Removing or changing rates of organic matter formation andaccumulation in the soil.
c. Affecting surface compactness.
d. Affecting soil water retention properties.
e. Affecting amounts and availability of essential nutrients.
f. Removing soil surface horizons through surface run off and sheeterosion.
2. Land Surface by
a. Affecting degree and rate of surface erosion by effects on soil and vegetation cover.
b. Effects on environment water.
3. Water by
a. Changing rates of transpiration and evaporation.
b. Changing rates of permeability and subsurface flow.
c. Affecting amount and rate of sedimentation.
d. Changing stream and river structure, through bank and surrounding vegetation destruction.
4. Vegetation, both directly and indirectly through the habitat effects mentioned above e.g.
a. Changing direction and speed of vegetation succession.
b. Affecting plant biomass, structure and shape.
c. Affecting plant phenology.
d. Affecting plant quality in terms of nutrient content and availability.
5. Animals by
a. Changing the shape or amount of vegetation cover.
b. Changing in plant palatability and availability.
c. Indirectly altering water availability.
d. Causing death or injury (especially lower orders of animals).
He further stated that many of these effects are related and interacting, thus the study of fire ecology and implementing its management is extremely complex.
Types of Fire Regime
Daubenmire (1974) recognized three main types of fires considering the portion of the vegetation that is consumed by the fire. There are ground fires, surface fires and crown fires. Ground fires are usually flameless and can penetrate to subterranean depths. They are mostly common in places where the soil is overlaid with thick layers of organic matter.
Surface fires feature above the ground surface and their flames usually consume the litter, living herbs and shrubs. They also scorch the basis of any tree along their route. Crown fires are those fires that burn to the crowns of trees and shrubs. Fires are also classified on the basis of the time of the year when they occur.
A cool fire (other wise known as early burning) is an early dry season fire, set when the grasses are still green and have high moisture content. A cool fire is usually mild, and as such does not consume all the vegetation. Early burning fires move close to the ground, shooting up to grass tops as they are encountered.
Temperatures rarely reach 300oC and are minimal at 2 m. below ground level. Tree tops escape damage as do the denser shrubs and greener shade loving grasses. Dead wood is slowly consumed. Small tracks, watercourses, valleys and ridges can act as barriers to these fires, and a heavy dewfall can extinguish them.
Thus, they rarely cover very large areas. A hot fire (late burning) occurs towards the end of the dry season, when the grass cover is completely dry and has low moisture content. According to Rogers (1979), this kind of fire moves rapidly at 1.2m above ground level, temperature can reach 600oC or more, and temperature effects can reach down to 5cm below ground level.
Tree tops are scorched and leaves killed, shrubs and seedling are engulfed. Dead wood is rapidly consumed, small barriers as mentioned above, can be jumped and such fires can cover large areas in a short space of time. Late burning in addition to its severity is also devastating on vegetation.
Cool and hot fires are no necessarily determined by calendar months. The severity (temperatures) of any of the different types of fires, and the degree of their impact on an ecosystem, are dependent on some factors, among which are the onset and termination of rains (the weather condition at the time of burning), soil moisture, wind direction and velocity, the topography, plant species – stage of maturity and water content, and the kind, amount, dryness and the disposition of the fuel that has accumulated since the last fire.
Fire and the Savannah Vegetation
The Savannah vegetation owes its existence to a number of factors operating singly, severally or in different combinations in a particular area. These factors include climate, soil, topography and human influences. The use of fire is seen to be the most prominent and perhaps the most potent factor in the production of derived savannah.
Late burning is however, very important in the continued maintenance of the derived savannah. Fire among other factors, is known to influence the structure of plant communities. It also influences the species composition of plant communities.
A Fire Regime for Wildlife Management
Prior to the selection of a fire regime and land use, policy statement is inevitable. Fire regimes (no burning, late burning and early burning) are selected for various reasons. For wildlife management a major objective is the provision of suitable habitat for the game resource. The wildlife manager aims to provide a sufficient grass cover of nutrient value. As conservationists we are also interested in the combination of other less noticeable species, such as forest duiker, requiring different more specialised habitats.
Therefore, there is a need for the maintenance of a variety of habitat. Resource use may bring difficulties, for instance, a non-burnt 2m high grass cover is not conducive to game viewing or hunting and these considerations of land use may affect the fire policy.
Unbridled fires in vegetation are known to have a number of adverse effects on the population of wild animals. According to Egunbjobi (1979) they are:
1. Destruction of their habitat.
2. Removal of food resources – mainly for herbivores
3. Destruction of young and eggs.
4. Exposure of predators.
Fire is also said to affect their breeding potentials as well as the movements and distribution of wild animals in their habitat. However, the following, among others, are the beneficial effects prescribed burning can have on wild animals:
a. Prescribed fire can be used to attract animals to certain parts of their habitat. This helps to enhance game viewing in aconservation area.
b. Fire when managed, is also a useful tool in the prevention of wildfire in conservation areas. This is done using rotational burning in blocks of land.