Pacific Southwest Research Station

Pacific Southwest Research Station
800 Buchanan Street
West Annex Building
Albany, CA 94710-0011

(510) 559-6300

Research Topics Ecosystem Processes

Title

Regional Climate Variability and High-Elevation Forest Response Over the Past 4000 Years

Limber pine (Pinus flexilis) chronologies and forest stand dynamics in the eastern Sierra Nevada and western Great Basin ranges.

Study Plan
Research Project Summary

The Research

Using tree-ring and ecological plot methods, we are developing longterm histories of subalpine forest demography and interpreting climate relationships of limber pine populations in the eastern Sierra Nevada and western Great Basin ranges. Limber pine is a long-lived, high-elevation tree species of the semi-arid West, whose deadwood preservation, strong tree-ring correlations with climate, and broad distribution make it an outstanding climate proxy for regions where species traditionally used for climate analysis (e.g., bristlecone pine) do not exist. Absence or minor role of fire in these sparse stands and steep, rocky sites allows for clear climate signals without confounding of successional disturbances or human land uses.

Early results indicate population extirpation and recolonization to be common over the last 3500 years, and appear to relate to century-scale drought climate variability. Decadal climate variability also is reflected in tree-ring patterns. Unique site variability related to local climate patterns is also emerging from these studies. Such variability has been overlooked in previous studies of regional paleoclimates.

With this study, we address three gaps in current paleoclimate knowledge:

1. Geographic gap: High-elevation climate history and variability in the western and central Great Basin over the past 3000 years,
2. Stand dynamics gap: Dominant changes in high-elevation pine population biology related to climate variability on century and decadal scales, and
3. Intra- and inter-regional variability gap: Site to site variability in montane climate and vegetation response.

Objectives

Develop long-term (4000+ years) climate chronologies, focusing on decadal, century, and millennial variability from living and deadwood limber pine (Pinus flexilis) at high elevations in the eastern Sierra Nevada and western Great Basin ranges.

Evaluate subalpine forest response to historic climate variability, especially catastrophic, decadal, and century-scale fluctuations.

Document intra-regional and inter-regional variability in climate and forest history across latitudinal transects from the eastern Sierra Nevada to western Great Basin.

Application of Research Results

Rapid changes in modern climate are occurring as a result of anthropogenic forces combined with natural climate changes. Together these are influencing widespread changes in forest demographics and distributions of the West, and forests at high elevation are considered especially at risk of extirpation. To understand potential responses of forests in the future to continuing climate changes, resource managers are attempting to plan strategically. Information from studies such as ours will help managers better understand on-the-ground changes at individual tree to stand to landscape scales that may unfold in the future, and thus enables them to plan effective conservation measures.

Location

High Sierra Nevada, east of the Sierran crest; between Mammoth Lakes and Bridgeport, CA; and Great Basin ranges to east, including Sweetwater Mountains, Glass Mountain Range, Wassuck Range, and the northern White Mountains. Our current study region extends from the Sierra Nevada climate/biotic biome to the Great Basin/semi-arid steppe biome along two latitudinal transects.

Lead Scientists/Collaborators

1) Millar, 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 94710 USA
ph: 510-559-6300

2) Lone Pine Research, Bozeman, MT 59715

Publications and Reports

• Millar, C.I., R.D. Westfall, and D.L. Delany. In revision. Mortality and growth suppression in high elevation limber pine (Pinus flexilis) forests in response to multi-year droughts and 20th century warming. Canadian Journal of Forest Research.
• 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.
• Poster: Millar, CI; Westfall, RD; and Delany, DL. 2006. Elevational Gradients and Differential Recruitment of Limber Pine (Pinus flexilis) and Bristlecone Pine (Pinus longaeva); White Mountains, California, USA.
• Poster: Millar, CI; Westfall, RD; and Delany, DL. 2005. Limber Pine Forest Mortality Event in Response to a Late-20th-Century Low Precipitation/High Temperature Period.
• 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. High-Elevation Response of Conifers to Climate Change in the Sierra Nevada and Western Great Basin, USA: Treeline Elevation is Not the Primary Effect.