The lodgepole pine historic plant association occurs in areas where cold air accumulates and frequent frosts occur (see fig. 6, page 102). The harsh environment in this association restricts establishment of shade-tolerant species in the understory, and the understory vegetation is very sparse. Because lodgepole pine is tolerant of cold air and cold soil temperatures and is resistant to frost and drought, it is the climax tree species in this association.
Lodgepole pine is very sensitive to fire. Because of its thin bark, it is easily killed by moderate- and severe-intensity fires. The frequency of fires in lodgepole pine forests varies. In the drier (xeric) areas, these fires may occur at intervals of less than 20 years (Atzet and McCrimmon, 1990). In the moister (udic) areas, these fires generally occur less frequently. Because lodgepole pine is such a prolific seed producer, regeneration after a severe-intensity fire normally is not a concern. Thick, even-aged stands usually become established after fires.
The ecological sites in areas of the lodgepole pine plant association are lodgepole pine/sedge (Pinus contorta/Carex), lodgepole pine/longstolon sedge (Pinus contorta/Carex inops), and lodgepole pine/squaw currant-antelope bitterbrush/western needlegrass (Pinus contorta/Ribes cereum cereum-Purshia tridentata/ Achnatherum occidentale ssp. occidentale).