United States Department of Agriculture, Forest Service
Pacific Southwest Research Station
Sierra Nevada Research Center
Response of Subalpine Conifers to 20th Century Climate Variability in the
Sierra Nevada: Meadow invasion, snowfield colonization, and changes in growth, form, and genetic
diversity--complex and threshold reactions to warming climates challenge current assumptions.
The Research:
Using tree-ring methods, ecological plot evaluation, and genetic
analysis, we are investigating multiple and independent indicators
of vegetation response in subalpine conifers to 20th century
climate change. To date we have studied annual internode growth
in krummholz (stunted) whitebark pine (Pinus albicaulis); release
of vertical branches in krummholz whitebark pine; invasion
of whitebark and lodgepole (P. contorta) pines into retreating
snowfields, and invasion of lodgepole pine into upper montane
meadows.
We plan next to investigate patterns of stand expansion over
elevational gradients, response to frost events, rate of stripbark
formation, and crown release in diverse whitebark pine zones.
We correlate these responses with regional climate parameters
to identify individual tree, stand, and biome level responses to
interannual, decadal (e.g., Pacific Decadal Oscillation), and centurylong patterns. Responses have been strongly related to climate
despite variability among sites in environmental and land-use
histories, indicating non-linear, unique, and threshold effects.
Objectives:
Evaluate temporal responses in tree growth and stand dynamics
of high-elevation pine forests during the past 200 years relative to
interannual, decadal, and century long climate change.
Assess 20th century climate influences on subalpine vegetation
relative to other natural and human-induced (livestock grazing, fire
suppression) forces.
Our Mission:
Sierra Nevada Ecosystems are
complex and our knowledge
of them is incomplete.
As a result, the long term
outcome of any given land
and resource management
strategy is uncertain. We
will provide assistance to
land managers and policy
makers by addressing this
management dilemma
through targeted research,
emphasizing an integrated,
ecoregional approach to
examine particular physical,
ecological, and socioeconomic issues, across a
range of appropriate spatial
and temporal scales specific
to each issue.
Application of Research Results:
This unit will represent the
collective research expertise
and interests of scientists
located in Fresno, Davis
and Albany as well as other
scientists within the Pacific
Southwest Research Station.
With a full spectrum of
research, from long term,
fundamental research
to short-term, tactical
applications, this Center
is intended to support
conservation, restoration,
and sustainable utilization of
the lands within the Sierra
Nevada ecoregion.
Publications:
USDA Forest Service
Pacific Southwest Research Station
Sierra Nevada Research Center
For further information contact:
Dr. Connie Millar
cmillar@fs.fed.us
Dr. Peter Stine, Program Manager
Subalpine forests are considered at high risk under current and future conditions of
warming climates. This concern derives from an assumption that warming climates
will force high-elevation vegetation ever higher where habitat diminishes in extent
and finally off the tops of mountains. Research information is needed about their
potential responses that are occurring already under changing climates of the 20th
and early 21st centuries so that effective conservation measures may be taken. Our
research indicates that subalpine forest response is far more complex than has been
widely assumed, and threshold, disequilibrium, reversible, and interacting forces
determine actual behavior. Conservation and management strategies must be built
with reliable information about what how forests are responding at present.
Location:
High central and eastern Sierra
Nevada, between Mammoth
Lakes and Bridgeport, CA.
PDFs available at: http://www.fs.fed.us/psw/programs/snrc/staff/millar
• Millar, C.I., Graumlich, L.J., King, J.C., Delany, D.L., and Westfall, R.D. 2004. Response of subalpine conifers in the Sierra Nevada, California, USA to twentieth-century warming and decadal climate variability. Arctic, Antarctic, and Alpine Research,
36(2):181-200.
• Millar, C.I., R. Neilson, D. Batchelet, R. Drapek, and J. Lenihan. In press. Climate
change at multiple scales. Chapter 3 in Salwasser, H. and M. Cloughesy (eds). Forests,
Carbon, and Climate Change. Oregon Forest Resources Institute Publication.
• Millar, C.I. and L.B. Brubaker. 2006. Climate change and paleoecology: New contexts for restoration ecology. Chapter 15 in M. Palmer, D. Falk, and J. Zedler (eds)
Restoration Science. Island Press. pp315-340.
• Westfall, RD and Millar, CI. 2004. Genetic Consequences of Forest Population Dynamics Influenced by Historic Climatic Variability in the Western USA. Forest Ecology and Management. 197: 157-168.
• Poster: Millar, CI; Westfall, RD; Delany, DL; King, JC; and Alden, HA. 2004. Climate as an Ecosystem Architect; Responses of High-Elevation Conifers to Past
Climate Variability.
• Poster: Millar, CI; Westfall, RD; Delany, DL; King, JC; and Alden, HA. 2004. HighElevation Response of Conifers to Climate Change in the Sierra Nevada and Western
Great Basin, USA: Treeline Elevation is Not the Primary Effect.
http://www.fs.fed.us/psw/programs/snrc
Albany Location:
800 Buchanan Street
Albany, CA 94710
Mailing Address:
P.O. Box 245
Berkeley, CA 94701
Phone: 510-559-6300
Fax: 510-559-6440
Davis Location:
2121 Second Street
Suite A101
Davis, CA 95616
Phone: 530-759-1700
Fax: 530-747-0241
Fresno Location:
2081 E. Sierra Avenue
Fresno, CA 93710
Phone: 559-323-3200
Fax: 559-297-3355