Ecological - Second Order
In 1967 and 1968, seven south- and east-facing units, averaging 4-ha each, in a western larch forest of northwest Montana were (1) clearcut and burned by prescribed fire or wildfire, (2) clearcut and unburned, or (3) uncut and burned by wildfire. More than 20 years of forest succession data from permanent transects show that fire caused a marked change in composition of all vegetation. Herb cover, mostly fireweed, dominated burned sites through the fifth year. Shrub cover (such as from willow or shiny leaf ceanothus) dominated burned sites from the 6th through the 20th years, but the herb cover changed little during this period. Trees rapidly regenerated burned sites, and height of pioneer species, such as western larch and lodgepole pine, exceeded that of shrubs about 7 years after treatment. But the percentage of conifer cover increased slowly and usually required at least 20 years to equal shrub cover. Without fire, the herb and shrub component remained relatively stable; trees were limited to the smaller, more shade-tolerant uncut conifers. Trees established slowly on unburned sites, and most were shade-tolerant subalpine fir and Engelmann spruce.