The Alpine-Treeline Warming Experiment was installed in 2008-2009 on Niwot Ridge above Boulder, Colorado. It uses infrared heaters to warm soil and plant surfaces by an amount comparable to current average projections of climate warming in the year 2100. We have three basic questions we hope to answer with the project:

  1. Will subalpine trees, currently restricted from cooler, higher elevations, move into alpine habitat and replace alpine plant species as a result of climate warming?
  2. Will subalpine trees be stressed by warmer temperatures and be less successful in their existing elevational ranges as a result of climate warming?
  3. Will ecosystem properties modify the effects of climate warming on subalpine or alpine species within and beyond their current elevational ranges?

Why is this important?

Alpine and subalpine ecosystems are islands of biodiversity isolated from each other by surrounding lower elevation areas. The species in these ecosystems may be particularly vulnerable to a warming climate given their isolation and adaptations to very cold conditions and short growing seasons. In addition, the forest-alpine tundra ecotone is an important land cover transition. Shifts in the position of this transition zone will affect snow pack and water cycling, local temperatures, and ecosystem carbon and nutrient cycling. Shifts would also affect wildlife habitat and recreational opportunities.


Our study focuses on limber pine and Engelmann spruce because they are common treeline species that occur throughout the Rocky Mountains, yet they also differ in important ways. For example, limber pine thrives in direct sunlight and can be found on exposed ridges, while Engelmann spruce is shade tolerant and more typically found on moist slopes or in valleys.

Recruitment, or the ability of seeds to germinate and become established, is an important bottleneck for plants to pass through before successfully expanding into new areas. Similarly, if a species is going to survive where it currently grows, new recruits must be successful. Therefore this experiment studies the germination and first few years of growth of limber pine and Engelmann spruce.

Alpine plant species restricted to growing above current treeline may be particularly vulnerable to climate change. One quarter of our experimental plots are devoted to studying the effects of climate warming on alpine species growth, reproduction, and physiology to determine which species may be most at risk.


March 2014
Research associate sought: We seek a lead field and data research associate to maintain and modify electrical experimental infrastructure; modify heater control algorithms; maintain Campbell datalogger, multiplexer, and communications equipment in the field to ensure dataset continuity; develop, maintain and execute QA/QC algorithms for a range of environmental sensor types; train field staff; maintain records; and communicate regularly and effectively with the project PIs and other collaborators. Other responsibilities may include managing seasonal research assistants, contributing to research articles, and/or mentoring undergraduate researchers, depending on the skills and experience of the candidate. Candidates must be physically fit for outdoor fieldwork at high elevations. The position is based near Boulder, CO and is available immediately. Please direct inquiries to lkueppers@ucmerced.edu.

October 2012
Andrew Moyes' paper documenting seedling sensitivity to summer soil moisture stress and high temperature at high elevations, and Cristina Castanha's paper reporting variation in subalpine tree recruitment patterns are now available online.

July 2012
John Harte and Lara Kueppers commented on a recent publication in Nature suggesting climate change experiments miss the mark in predicting plant phenological sensitivity to temperature. We contend that because air temperature is but one climate variable plants may be sensitive to, and many of the evaluated experiments did not explicitly manipulate these other variables, deeper insight into plant sensitivity to climate change will only come from careful integration of experiments and observations of natural variation within common sites.

April 2012
Jeff Mitton and Scott Ferrenberg have been busy talking about their finding that mountain pine beetles seem to be getting a second generation in each year thanks to warming spring and summer climate. Their article was published online in The American Naturalist in March.

March 2012
UC Merced just put out this video about the project.

January 2012
We are again recruiting research assistants for the 2012 field field season. For more information, read this ad. Also, old but good news: Keith Reinhardt's paper showing consistent cross-site provenance differences in limber pine seedling morphology and physiology is out in Tree Physiology.

February 2011
We are recruiting research assistants for the 2011 field field season. For more information, read this ad. Update: We are no longer accepting applications.

August 2010
Denver Post article features our experiment. Read the article. And the Contra Costa Times reprinted it. Read the article. Keith Reinhardt and Lara Kueppers present preliminary findings at ESA meeting in Pittsburgh.

April 2010
Collaborator Carolin Frank and PI Lara Kueppers received a Graduate Research Council grant from UC Merced to sequence microbial endophyte RNA from limber pine and Engelmann spruce seedlings.

January 2010
University of Colorado-Boulder researchers began a collaborative effort with the existing research team to measure snow properties in the Alpine and Upper Sub-alpine field sites. The Boulder based crew hopes to learn what effects increased temperatures will have on snow depth, density, and water content. In addition to data from the electronic sensors, the Boulder based crew will continue to visit the field sites to compare heated plots to unheated areas nearby.

December 2009
Several members of the research team presented early results and findings from the experiment at the AGU meetings in San Francisco.

October 2009
The heat is on!

July 2009
This project was mentioned in a Nature news article about the new cluster of projects funded by DOE to study species range shifts with climate change. Read the article.