<P> Generation of carbonates from burnt plant material following fire disturbance causes an initial increase in soil pH that can affect the rate of secondary succession, as well as what types of organisms will be able to thrive . Soil composition prior to fire disturbance also influences secondary succession, both in rate and type of dominant species growth . For example, high sand concentration was found to increase the chances of primary Pteridium over Imperata growth in Imperata grassland . The byproducts of combustion have been shown to affect secondary succession by soil microorganisms . For example, certain fungal species such as Trichoderma polysporum and Penicillium janthinellum have a significantly decreased success rate in spore germination within fire - affected areas, reducing their ability to recolonize . </P> <P> Vegetation structure is affected by fire . In some types of ecosystems this creates a process of renewal . Following a fire, early successional species disperse and establish first . This is then followed by late successional species . Species that are fire intolerant are those that are more flammable and are desolated by fire . More tolerant species are able to survive or disperse in the event of fire . The occurrence of fire leads to the establishment of deadwood and snags in forests . This creates habitat and resources for a variety of species . Fire can act as a seed dispersing stimulant . Many species require fire events to reproduce, disperse, and establish . For example, the knobcone pine ("Pinus attenuata") has closed cones that open for dispersal when exposed to heat caused by forest fires . This particular conifer grows in clusters because of this limited method of seed dispersal . A tough fire resistant outer bark and lack of low branches help the knobcone pine survive fire with minimal damage . </P>

Why is the title of model 2 secondary succession rather than primary succession