Spruce-fir forests

Fir and spruce forests are greatly affected by slight fluctuations in climate. Temperature is the primary determinate for spatial patterns of fir and spruce. The two dominant trees in this type of forest are Picea engelmannii (Engelmann spruce) and Abies lasiocarpa (subalpine fir). Although thick-barked trees, such as the Pinus resinosa, frequently survive fire, the thin bark of spruce make them more vulnerable. Trees such as the Douglas fir withstand much of the fire due to the thicker bark they have. The scale of the burn mosaic during a fire, relative to species niche requirements and mobility, can have major impacts on flora and fauna dynamics.

Forests of the Southern Appalachian Mountains had covered approximately 140 km² on peaks and ranges. Today this forest type occupies less than 70 km². Much of this forest loss is due to logging, followed by slash fires. The Waterrock Knob fire was composed of different group of plant species than are normally found in burned spruce and fir forests. The tree layer of this stand consists of fewer than expected stems and has low basal area. The shrub layer is very dense, which may reduce successful tree reproduction. The herbaceous layer growth is not typical of young, disturbed spruce and fir stands. These vegetation characteristics suggest that possibly a hot fire in conjunction with a steep rocky slope and shallow soils have been some of the reasons for the reduced development of a typical spruce and fir stand. Burned soil has been an important factor in determining earlier and present vegetation patterns and species composition.

Post fire effects of the western United States forests include an important study of the fire of Yellowstone National Park in 1988. Historically, controlled burns had been utilized to thin forests. By the 1970s, Yellowstone started a natural fire management plan to allow the process of lightning caused fires to continue influencing wild land succession. In 1988, 248 fires were started in Yellowstone National Park. As for the animals that were killed by the fires, the U.S National Park Service tallied 345 elk, 36 deer, 12 moose, 6 black bears, 9 bison and 1 grizzly bear. Fish were also killed due to heated water. Surveys indicated that less than 1% of the soils were heated enough to burn below ground plant seeds and roots. The U.S Congress launched a massive study of the long term 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.

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