Age-class structure of old growth ponderosa pine/Douglas-fir stands and its relationship to fire history

Call Number:

URL:

Keywords:

Abstract:

Trees on nine 100-by-100-m plots in old growth ponderosa pine/Douglas-fir stands in western Montana were aged and mapped. Fire history since the early 1600s was determined for each plot from fire scar cross-sections. Six of seven sample plots on the Bitterroot and Lolo National Forests had a nearly all-aged structure among the overstory ponderosa pine; trees commonly ranged up to 500 years of age. These plots were on steep slopes, and prior to 1900 had experienced nonlethal underburns at mean intervals of 13 to 50 years. Plots on the Flathead National Forest were on gentle topography in a moist glacial valley. They had even-aged structures supporting primarily ponderosa pine and western larch. Pre-1900 fire history was characterized by patchy stand-replacing events (fire and perhaps bark beetle epidemics) at intervals of 150 to 400 or more years with intervening underburns at mean intervals of 20 to 30 years. All stands had developed an understory of Douglas-fir in recent decades. Only the two plots that experienced natural fires in this century (1919 and 1953) had a major proportion of vigorous, young ponderosa pine. Our data suggest that understory fires were influential in maintaining ponderosa pine dominance in a variety of stand age structures. We conclude that, in many stands, the effects of fire exclusion during this century preclude use of fire alone to recreate historic structures.

Notes:

ELECTRONIC FILE - Ecology

Suggested citation: Amo, Stephen F.; Scott, Joe H.; Hartwell, Michael G. 1995. Age-class structure of old growth ponderosa pine/Douglas-fir stands and its relationship to fire history. Res. Pap. INT-RP-481. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 25 p.

SWAP (2/19/2016) citation:
Arno SF, Scott JH, Hartwell MG. 1995. Age-class structure of old growth ponderosa pine/Douglas-fir stands and its relationship to fire history. Ogden (UT): US Forest Service, Intermountain Research Station. 25 p. INT-RP-481. [accessed 2015 Dec 21]. http://www.fs.fed.us/rm/pubs/rmrs_gtr292/int_rp481.pdf.