ecological effects caused by the Yellowstone fires. The short term effects proved most wildlife populations showed no effects or rebounded quickly. In the years following the fire, precipitation combined with short term ash and nutrient influx led to a stunning display of wild flowers on the burned areas. Effects of fire Because plants are immobile, they must develop resistances to disturbances through natural selection. Individual plant species vary their resistance to fire injury in predictable ways. These resistances make it possible for the biodiversity to greatly increase during recolonization after a fire. Studies show that in a spruce and fir forest, eleven years after a fire, there is a greater diversity of herbs than in a community where there was no fire. The shrubs took longer to regenerate but soon there was greater diversity in the shrub population as well. Spruce and fir forests have a greater biodiversity than most other forests because of their multiple layers of canopy and dense understories. This creates a heterogeneous, diverse stand structure which leads to an assortment of fire types which usually leave patches of unburned trees. Because the soil is oxidized by the fire, seed germination is encouraged. Also, many herb species were present in burned areas but not areas that were unaffected by fire. Fir and spruce trees are wind-dispersed, so the number of regenerated trees depends on the distance from the unburned stands to the sample location. Spruce and fir regeneration The time it takes for fir and spruce to regenerate varies greatly, but it takes a number of years if no roots or snags remain. Regeneration time depends on a number of environmental factors, such as species type, wind strength, and aspect. It may be much more difficult for fir and spruce to be established on a slope, not only because of the dispersion technique, but also because erosion is greatly increased by fire, making it harder for the seeds to take root. Also, fir and spruce differ in survival techniques. Fir uses rapid growth, short lifespan, and easy establishment to come back more quickly after a fire, while spruce relies on longer lifespan and larger basal area to survive. Spruce has a much lower establishment rate, but the larger basal area increases its chances of survival and allows it to regenerate by both wind dispersion and growth from the roots remaining after a fire. The result is that