USDA Forest Service

Pacific Southwest Research Station
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics Ecosystem Processes

Sierra Nevada Ecosystems

Genetic Variability in Pinus albicaulis at Treeline in Relation to Patch Age, Vegetative Layering, and Climate Variability

Study Plan

The Research

Krummholz whitebark pine 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.

Mount Warren with Krummholz Pine 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.


blue arrrow To investigate genetic and ecological dynamics of whitebark pine growth and response at treeline to longterm climate changes.

blue arrrow To evaluate relative roles of vegetative reproduction (layering) and sexual reproduction (seed dispersal) to treeline persistence during diverse climate phases.

blue arrrow To assess changes in, and ecological significance of, layering events, clone number, size, and shape, and landscape coverage over time.

blue arrrow To determine genetic diversity, family structure, gene flow, and geographic lineage effects within and among krummholz patches and sites.

Application of Research Results
map of the Sierra Nevada Ecoregion

Eastern Sierra Nevada; Mono Basin and vicinity. Treeline sites in the Dana Cliffs, Warren Bench, and Dunderberg-Kavanough Crest regions.

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 94706 USA
ph: 510-559-6300

2) Lone Pine Research, Bozeman, MT 59715

Publications and Reports
Last Modified: Aug 29, 2016 10:57:00 AM