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

Medieval Forests, Volcanism, and Response to Climate
Clues to ecological effects of future climate changes

Study Plan
Research Project Summary

The Research

Ancient logs on Whitewing Mountain Whitewing Mountain, 3030 m, is a broad peak extending above current treeline that lies east of the main Sierra Nevada crest and adjacent to the Inyo Craters volcanic chain. The last eruptive sequence of Glass Creek Vent occurred ~500-800 years ago and covered the flanks and summit of Whitewing Mountain with more than 4 m of tephra. Strewn on top of the tephra over the otherwise barren summit plateau are hundreds of well-preserved dead tree stems, many of which are large, straight, and exhibit evidence of rapid growth from their tree-rings. The surprising growth rate, form, and occurrence of trees in this 'ghost forest' at this elevation suggest that they grew under climates very different from the present. Regular orientation of the tree stems and absence of stump bases suggest that the trees died in the Glass Creek Vent eruption. A similar situation exists on adjacent San Joaquin Mountain. We are using these natural events to unravel the story of forest origin, the climate under which the forests grew, and the exact year of the volcanic event.


blue arrrow Identify species and determine dates of trees that grew in the ghost forest on the summit of Whitewing Mountain.

blue arrrow Accurately date the last eruption of Glass Creek vent.

blue arrrow Model the climatic conditions under which the forest grew and interpret the significance and implications for forest response to future climate change.

Methods and Results

Collecting samples on Whitewing Mountain Using dendrochronological methods, we have dated stems from the summit to a narrow span of time during the Medieval period, from 900-1340 AD. From wood anatomy, we identified at least six species of conifers grew on the summit where now there is no woody vegetation. At present, the upper elevation limit of these species is as much as 800 m below the Whitewing summit; one species (sugar pine, Pinus lambertiana) grows only on the west slope of the Sierra in this region. Scars on the wood indicate repeat fires occurred during the time the forest was growing.

Application of Research Results

Using ecological niche theory and contemporary distributions of the species, we modeled paleoclimate during the Medieval period of the ghost forest to be significantly warmer (+3.2 degrees C annual minimum temperature) and slightly drier (-24 mm annual precipitation) than present. These values resemble projections for California in the next 70-100 years under conditions of global warming, and give insight into the potential responses of forests in subalpine zones. Based on conditions at Whitewing Mountain, forest managers and conservationists may expect much larger movement of tree species in response to climate change than has been anticipated to date. Non-equilibrium changes, with species moving individualistically, rather than in equilibrium with their current ranges, may be expected. Regional extirpations, such as happened to sugar pine in the eastern Sierra following climatic change at the end of the Medieval period, should also be a potential outcome that managers evaluate as they plan climate-informed policy.


map of the Sierra Nevada Ecoregion Whitewing Mountain, 10,012' (3030 m), eastern Sierra Nevada, between Mammoth Lakes, and June Lake, CA, Mono County, and similar environmental locations nearby (San Joaquin Mountain).

Lead Scientists/Collaborators

1)Millar, C.I. 1) Delany, D.D. 1) Westfall, R.D. 2) King, J.C. and 3) Alden, H.A.

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
3) The Smithsonian Institution, Suitland, MD 20746

Publications and Reports
Last Modified: Aug 29, 2016 10:57:06 AM