Genetic Variability in Pinus albicaulis at Treeline in
Relation to Patch Age, Vegetative Layering, and Climate Variability
Research Project Summary
Upper-forest-border populations of montane conifers are well known
for their sensitivity to longterm climate change. The dominant treeline
species in the Sierra Nevada, whitebark pine (Pinus albicaulis),
grows in upright form in the lower portion of its California range
and in stunted matts (krummholz) in widespread high-elevation zones
that form treeline in the Sierra Nevada. Using tree-ring methods,
ecological plot evaluation, and genetic analysis, we are studying
population dynamics of treeline krummholz (stunted) whitebark pine
in relation to historic climate. Whitebark pine differs from other
upper forest-border species in the Sierra Nevada in that elevation
of treeline does not appear to shift with changing climates, but
persists for over 1500 years. We are investigating the timing of
recruitment and the genetic composition of clones within krummholz
clusters and across the landscape as clones proceed from seedling
stage to old age. Similarly, we are assessing periodicities of layering
events and the relative contributions of layering and sexual reproduction
to whitebark pine persistence in krummholz matts. Using climate
information from the instrumental record over the last 120 years
and tree-ring reconstructed and other proxy information for climate
over longer periods, we evaluate the relative importance of vegetative
and sexual reproductive events to climate change.
In addition to the contribution of this work to vegetation and climate
science, we focus on the significance of interpretations to anticipated
global climate change and conservation. Alpine zones have been modeled
as among the most sensitive to changes predicted in the coming century,
but very little detailed ecological research has been conducted
to determine the nature of response of high elevation conifers to
specific climate variables. Unique and unexpected responses have
been suggested by our other studies (see research on 20th century
vegetation response) and are likely in these conditions as well.
The information from our research feeds into applications that depend
on predicting the nature of vegetation change at high elevations,
and will find relevance to land managers and policy makers concerned
about future landscape impacts.
To investigate genetic and ecological dynamics of whitebark pine
growth and response at treeline to longterm climate changes.
To evaluate relative roles of vegetative reproduction (layering)
and sexual reproduction (seed dispersal) to treeline persistence
during diverse climate phases.
To assess changes in, and ecological significance of, layering events,
clone number, size, and shape, and landscape coverage over time.
To determine genetic diversity, family structure, gene flow, and
geographic lineage effects within and among krummholz patches and
APPLICATION OF RESEARCH RESULTS
Eastern Sierra Nevada; Mono Basin and vicinity. Treeline sites
in the Dana Cliffs, Warren Bench, and Dunderberg-Kavanough Crest
C.I. 1) Delany,
D.D. 1) Westfall,
R.D. and 2) King, J.C.
1) USDA Forest Service, PSW Research Station
Sierra Nevada Research Center
800 Buchanan St., Albany, CA 94706 USA
2) Lone Pine Research, Bozeman, MT 59715
PUBLICATIONS AND REPORTS
PDFs available at: http://www.fs.fed.us/psw/programs/snrc/staff/millar/
- Rogers, D.L., Millar, C.I., and Westfall, R.D. 1999. Fine-scale
genetic structure of whitebark pine (Pinus albicaulis):
Associations with watershed and growth form. Evolution 53(1):
- Millar, C.I., Delany, D.L., Westfall, R.D, and King, J.C. Genetic
variability of whitebark pine (Pinus albicaulis) krummholz
in relation to patch age and vegetative layering in the eastern
Sierra Nevada. In prep.