PARENT SESSION
Contributed Oral Session 24: Disturbance Ecology: Management; Response to Fire
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 516 D, Level 5, Palais des congrès de Montréal
Ponderosa pine and Douglas-fir responses to repeated fire in wilderness areas of the inland Northwest.
Sala, Anna*,1, Keeling, Eric1, DeLuca, Thomas2, 1 Division of Biological Sciences. The University of Montana, Missoula, MT, USA2 Department of Ecosystem and Conservation Science. The University of Montana, Missoula, MT, USA
ABSTRACT- Fire exclusion over 100 years in ponderosa pine systems of the inland northwest have resulted in an increase of forest density due to the incursion of Douglas-fir and other shade tolerant species. As part of larger study on the consequences of fire exclusion in natural, unlogged wilderness areas we measured wood radial growth rates of mature ponderosa pine and Douglas-fir trees in stands with different fire histories during the twentieth century. We selected four sites located in the Selway Bitterroot and Frank Church wilderness areas, each with one stand not burned since at least 1910 and one stand burned 3 or more times since 1880. Preliminary data indicate that at some sites wood radial growth rates of mature ponderosa pines during the fire-exclusion period were higher in the frequently burned stands compared to the unburned stands. However this was not the case at all sites. In contrast, Douglas-fir growth rates were similar in both frequently burned and unburned stands. These results suggest that fire-related growth responses in mature ponderosa pine may vary across complex, unmanaged landscapes, while Douglas-fir may not respond to fire. Total live fine root biomass and percent mycorrizal infection of conifer roots was similar between frequently burned and unburned stands. However, consistent with a slightly higher percent of grass cover, frequently burned stands had significantly higher proportion of angiosperm roots relative to unburned stands. We also collected foliage samples to compare nitrogen content and water use efficiency between burned and unburned stands.
Key words: ponderosa pine, Douglas-fir, Fire exclusion, wilderness