Paper No. 16
Presentation Time: 12:45 PM
PALEOECOLOGICAL RECONSTRUCTION OF A MODERN SUBALPINE WHITEBARK PINE (PINUS ALBICAULIS) COMMUNITY IN GRAND TETON NATIONAL PARK, U.S.A
While climate, fire, and vegetation are strongly linked on regional and global scales, the relative roles of these three factors are not well-documented during the Holocene in high elevation mountain sites of North America. Recent anthropogenic changes in climate and fire management practices are underway, but the potential responses of subalpine vegetation to these environmental changes remain relatively unknown.
We documented in high temporal and spatial detail the paleoecology of an unnamed, high-altitude pond (known informally as Whitebark Pine Moraine Pond) located at 2805m elevation in Grand Teton National Park, U.S.A. We generated a Holocene-scale local fire history for the surrounding watershed using fossil charcoal, pollen, and macrofossil analysis from a 1.5 meter lacustrine sediment core retrieved in 2010. We also conducted a dendrochronological study of the current stand of whitebark pine trees (Pinus albicaulis) in the watershed to determine both approximate dates of establishment and responses to past climate change of this modern whitebark pine stand.
Sedimentary charcoal data indicate significant variability in both fire frequency and fire intensity during the Holocene. Fire frequency ranges from 2 to 5 fires/1000 y identified with charcoal peaks above background charcoal in the statistical program CHAR. Over 75 % of arboreal charcoal morphotypes during most of the sedimentary record indicates the importance of fire regimes that include frequent mixed-severity firesto whitebark pine ecosystems. Ages of individual whitebark pine trees average 365 years, and dendrochronology data suggest that ring widths of the current stand have been declining since the 1980’s. Statistical analyses of climate data suggest that this decrease in growth is likely the result of decreased growing season temperature ranges driven by a warming climate. Synthesis of sedimentary and dendrochronological proxies will be useful in generating conservation and restoration management plans for high-elevation conifer communities.