Fire

Fire is an exothermic factor produced by the chemical process of combustion, releasing both heat and light; most fires are man-made, though some arise naturally from friction between tree surfaces. Fires are classified by where they burn: ground fire (flameless, subterranean, burning organic matter below the surface), surface fire (consuming herbs and shrubs at ground level), and crown fire (burning through the forest canopy itself). The ecological effects of fire are almost entirely destructive in the short term — it has a direct lethal effect on plants, and the burn scars it leaves behind become easy entry points for parasitic fungi and insects — while also altering light penetration, rainfall patterns, nutrient cycling, soil fertility, soil pH, and the composition of soil flora and fauna. Certain fungi that specifically colonise burnt soil, such as Pyronema confluens, are called pyrophilous fungi, and along with plants like the fern Pteris, they act as biological indicators of fire — their presence signals that an area has recently burned. A fire break is a gap in vegetation that slows or stops a fire's spread; this can occur naturally (a river, lake or canyon interrupting continuous vegetation) or be created deliberately. Trees also carry a built-in structural defence against fire called rhytidome — the outer …