Thus, the time of year when it's warmest and most conducive to bacterial and fungal decomposition, moisture is limited, and rapid decomposition of litter is precluded. There is usually only a short period of the year during the spring months when soils are both moist enough and warm enough to provide decomposing organisms the proper environment for composting litter. Without fires, dead material accumulates, locking up essential nutrients necessary for plant growth. Fires release these nutrients, and enhance the production of nitrogen- fixing plants that often revegetate recently burned areas. Fires are thus analogous to river floods which each year provide a new layer of life-giving soil for plant growth.
Fires also cleanse forests.
Many tree pathogens are killed just by the smoke. In addition, insects and diseases are directly reduced by fires. Once a fire has burned through a forest, especially if it is a cool, slow burning fire, the younger trees are thinned out while leaving behind the more mature individuals. Some species like the Ponderosa pine, Douglas-fir, Western larch, Jeffery pine, and Sequoia are specifically adapted to survive fires by having a thick bark and tall limbless trunks which protect them from small, quick burns. These survivors experience increased viability due to reduced competition for nutrients, light and water.