PARENT SESSION
Oral Session #7: Disturbance in Forests: Fire, wind, and other.
Presiding: G. Murray
Monday, August 5. 8:00 AM to 11:30 AM. Cochise Meeting Room, TCC.
Variability and change in stand function in Yellowstone National Park: How do large, infrequent fires affect the spatial heterogeneity of forest ecosystem processes?
Kashian, Daniel*,1, Turner, Monica1, Romme, William2, 1 University of Wisconsin-Madison, Madison, Wisconsin2 Colorado State University, Ft. Collins, Colorado
ABSTRACT- Understanding the implications of landscape heterogeneity and disturbance dynamics for ecosystem processes remains a challenging task. Although ecologists have made strong advances in understanding temporal dynamics of aboveground net primary productivity (ANPP) of forests, the spatial variability of ANPP and its changes through time are poorly understood across broad spatial scales, particularly in response to large, infrequent disturbances. The 1988 Yellowstone fires resulted in a 250,000-ha mosaic of lodgepole pine (Pinus contorta var. latifolia) regeneration that varies widely in both seedling density (CV=175.9%) and in ANPP (CV=105.7%). To examine the temporal dynamics of this spatial variation in ANPP, we estimated ANPP across a chronosequence of stands ranging in age from 50 to 350 years and in density from 460 to 11,320 stems/ha using allometric equations for lodgepole pine. Stands of different initial tree density and ANPP exhibited different trajectories of ANPP as stands aged, but rates tended to converge with time since disturbance. Variation in both stand density and ANPP declined with stand age, reiterating that forest ecosystem processes are closely linked to stand structural characteristics. Notably, convergence of stand structure and ANPP of many stands occurred within 300 years, which approximates the return interval for large fires in this landscape. Thus, although large, infrequent fires serve as strong initial determinants of broad-scale heterogeneity in ANPP across the Yellowstone landscape, spatial variability is likely to diminish with time as variation in stand structure declines.
KEY WORDS: Pinus contorta var. latifolia, forest succession, stand development, ANPP