Burn Severity Effects on Quaking Aspen Regeneration

Western quaking aspen (Populus tremuloides) is a disturbance species and has been perpetuated on site for extended periods of time by fire, disease, and other types of disturbances. Where aspen initially existed, it will reoccupy and stabilize sites after burning. Initial data obtained by Forest Inventory and Analysis (RMRS’s RWU-4801) shows there has been a 50-95% decline in aspen dominated lands in the Interior West since European settlement. Most of this decline can be attributed to the efficiency of management to minimize natural occurring fires and to the loss of fine fuels by grazing animals both domestic and wildlife. This lack of burning has allowed natural succession to occur, which causes aspen to change to conifer or shrub dominated sites. The fires of 2000 & 2002 allowed us the opportunity to study the impact of fire on late successional aspen.

Aspen sampling during the summer of 2003 documented first-year response of the different burn severities found within the Battle Creek (SD), Hayman (CO), Million (CO), Missionary Ridge (CO), and Sanford (UT) fires that occurred in 2002. The Jasper fire (2000), in South Dakota, was also sampled. Observations included the type of damage to the aspen suckers from disease, insects, wildlife, and weather. In addition, it was noted if domestic or wild ungulate signs were found in or adjacent to the mil-acre sample plots.
Burn severity (relates to the amount of fuels consumed and damage done to a site by fire) had a consistent impact on initial response of aspen regeneration following the wildfires of 2002. Generally, low severity sites produced the greatest amount of regeneration, followed by moderate severity, and then highest severity. Unburned sites usually produced the fewest number of aspen; however, if the fire in high-severity sites killed the aspen roots, then fewer suckers were produced.

Sampling of the Jasper fire (2000) revealed that ungulate browsing had a profoundly negative impact on aspen regeneration following fire, especially if the sites are allowed to be grazed too soon following fire. Grazing should not be permitted until aspen stems average at least 6 feet tall (1.8 m) at the terminal bud, and the percentage of stems browsed can be kept below 30 percent.