are in the soil. A low fire intensity, a quick passing of the flames and a dry soil will also help. An increase in available nutrients after the fire has passed may result in larger microbial communities than before the fire. The generally greater heat tolerance of bacteria relative to fungi makes it possible for soil microbial population diversity to change following a fire, depending on the severity of the fire, the depth of the microbes in the soil, and the presence of plant cover. Certain species of fungi, such as Cylindrocarpon destructans appear to be unaffected by combustion contaminants, which can inhibit re-population of burnt soil by other microorganisms, and therefore have a higher chance of surviving fire disturbance and then recolonizing and out-competing other fungal species afterwards. Fire and ecological succession Fire behavior is different in every ecosystem and the organisms in those ecosystems have adapted accordingly. One sweeping generality is that in all ecosystems, fire creates a mosaic of different habitat patches, with areas ranging from those having just been burned to those that have been untouched by fire for many years. This is a form of ecological succession in which a freshly burned site will progress through continuous and directional phases of colonization following the destruction caused by the fire. Ecologists usually characterize succession through the changes in vegetation that successively arise. After a fire, the first species to re-colonize will be those with seeds are already present in the soil, or those with seeds are able to travel into the burned area quickly. These are generally fast-growing herbaceous plants that require light and are intolerant of shading. As time passes, more slowly growing, shade-tolerant woody species will suppress some of the herbaceous plants. Conifers are often early successional species, while broad leaf trees frequently replace them in the absence of fire. Hence, many conifer forests are themselves dependent upon recurring fire. Both natural and human fires affect all ecosystems from peatlands to shrublands to forests and tropical landscapes. This impacts the way that the ecosystem is structured and functions. Though there have always been wildfires naturally, the frequency of wildfires has increased at a rapid rate in recent years. This is largely due to decreases in precipitation, increases in temperature, and increases in human ignitions. Different species of plants, animals, and microbes specialize in exploiting different stages in this process of succession, and by creating