Fire Effects on Prairie Vegetation from Ecology and Conservation of the South Puget Sound Prairie Landscape

Fort Lewis is an excellent site to determine the effects of different fire regimes on prairie
vegetation. Fort Lewis has three widely divergent, documented fire return intervals in a
small area with uniform soils. These fire regimes include: a) fire suppression, b)
prescribed burning on a 3-5 year rotation and c) the annual burning of the Artillery
Impact Area ignited from exploding ordinance.

Fire suppression affects a much greater area on Fort Lewis and is more harmful to prairie
vegetation than excessive burning. Fire suppression allows Psuedotsuga and Cytisus to
invade prairies which in turn eliminate prairie vegetation. Vegetation responses one
growing season post prescribed fire were varied. Festuca idahoensis, Lupinus lepidus and
Hypochaeris radicata decreased in cover after both spring and fall burns. Species that
increased in cover included non-vascular crytopgams, Luzula campestris, Microseris
laciniatus, Rumex acetosella and Lomatium triternatum. Annual burning within the
Artillery Impact Zone has resulted in a significant alteration in the vegetation. Festuca
idahoensis is merely a minor component, while the non-native Anthoxanthum aristatum
and Hypochaeris radicata dominate. These effects are similar to many prairie fire studies
throughout the American West.

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