Effects Of Wildfires On Forest Ecosystems

Ecological Restoration of Forests and Fires

One of the most predominate ecosystems is the forest community. Covering about one-fourth of the land area on Earth, forests consist mainly of trees and other woody vegetation, growing closely together. The trees can be large and densely packed, as they are in the coastal forests of the Pacific Northwest, or they can be relatively small and sparsely scattered, as they are in the dry tropical forests of sub-Saharan Africa. Forests are complex ecosystems that also include "soils and decaying organic matter, fungi and bacteria, herbs and shrubs, vines and lichens, ferns and mosses, insects and spiders, reptiles and amphibians, birds and mammals, and many other organisms" (Audesirk, 2003). All of these components constitute an intricate web with many biological interconnections. A bird may depend on the upper branches of a tree for nesting, while the tree may depend on the fungi surrounding its roots to obtain water and nutrients. A forest performs a number of vital environmental services, such as cleansing the air, moderating the climate, filtering water, cycling nutrients, providing a habitat for animals and provides humans with recreation and beautiful scenery. Resources from the forest supply raw materials, such as lumber, paper products, greenery and pharmaceuticals. Some of the developing issues today concerning forests are fires and what we as a society can do to restore the natural ecosystems within the forests around our world. Many aspects are to be considered when looking at the ecology and bioremediation of forests such as, human activities, wildlife, endangerment and environmental changes. This paper will discuss the effect wildfires have on the forest ecosystem.

Human beings cause most wildfires, directly or indirectly. In the United States lightning, the only truly natural cause is responsible for less than 10% of all such fires. In the West, lightning is the primary cause, with smoking (cigarettes, matches, and such) the second most frequent. Combined they account for 50 to 75% of all wildfires. In the "13 southern states (Virginia to Texas) the primary cause is arson; this combined with smoking and debris burning makes up 75% of all wildfires" (Perry, 1994). The other causes of wildfires are machine use and campfires. Machine use includes railroads, logging, sawmills, and other operations using equipment. Due to rapid increases in human consumption, reforestation has become important. In our past, when human population was low, people utilized the forest for gathering wild plants and game to obtain food. There was not a great deal for concern about the changes of the ecosystems of forests. Mature natural forests usually "produced wood at a rate of 14-28 ft, and this often exceeded the rate of harvesting firewood. However, with the adoption of agriculture, humans settled down and their populations increased, placing pressures on forests" (Perry, 1994). Not only did the demand for fuel wood increase, but forests were cut down to make room for agriculture. For example, in 1600 about 49% of the continental United States was covered with forests, but this had been reduced to 33% by 1900. In just 300 years, population pressures reduced forestlands by about 1 million acres. Since natural regeneration was not keeping up with the rate of harvests, the need for rapid reforestation became more apparent.

During the late 1800s, concern was expressed about future wood supplies in the United States due to floods caused by deforestation and fires. Two solutions to these problems were proposed. One resulted in the creation of national forests where wood and clean water could be produced in perpetuity, the other "promoted artificial regeneration, the establishment of trees by planting or direct seeding" (Perry, 1994). Due, in part, to a combination of improved technology in both agricultural and artificial regeneration, the United States now has about the same amount of forestland as it did 80 years ago. This is not true in many countries where human populations are increasing but artificial regeneration has been limited. Truly this shows that humans have had a great impact on the ecosystems of forests in our past.

Fire has shaped vegetative communities for a long as vegetation and lightning have existed on earth. Fire affects soil in several ways: the increase of temperature, the removal of plant matter and the soil's ability to absorb rainfall and snowmelt. If plants are killed, their roots will cease to hold the soil together increasing the danger of erosion. The increased temperatures caused by the fire can have effects on the characteristics of the soil. First of all, all organic matter in the soil will be removed. Other minerals and compounds may also be removed depending on how hot and long the fire burns. High temperatures may also kill the biotic components of the soil which can seriously affect post fire productivity. The soil exposed by the fire will become more susceptible to freezing.

Animals are affected by fire mainly through changes to their habitat. Typically, animals either die or flee the fire area. Influenced by fire intensity, severity, rate of spread, uniformity, and size, long-term faunal response to fire is determined by habitat change, which influences feeding, movement, reproduction, and availability of shelter (Ansley et al., 2000). The extent of fire's effects on animal communities generally depends on the extent of change in habitat structure. Contrary to popular belief, fire usually injures or kills a very small portion of the animal population. Smoke inhalation is a greater threat. Most animals that are killed were the weak or very small that are trapped by the fire.

Without the ability to move, flora is the hardest hit by fire. Understory fires change the canopy in two ways: by killing or top-killing a few of the most fire-susceptible trees, and by killing or top-killing a cohort of tree regeneration, also selectively according to fire resistance (Lyons et al., 2000). Understory fires also reduce understory plant biomass, sometimes in a patchy pattern. Stand-replacing fires change habitat structure dramatically. When crown fire or severe surface fire kills most of the trees in a stand, surface vegetation is consumed over much of the area, and cover for animals that use the tree canopy is reduced. Crown fires eliminate most cover immediately; severe surface fires kill the tree foliage, which falls within a few months. Stand-replacing fires alter resources for herbivores and their predators. The habitat is not "destroyed," but transformed: The fire-killed trees become food for millions of insect larvae and provide perches for raptors. Trees infected by decay before the fire provide nest sites for woodpeckers and then for secondary