Forests: Current Research

Climatic Mediation of Treeline in the Western U.S.



At upper and lower treeline, climate variability, particularly at decadal scales, is important in structuring broad pulses of tree establishment. However, local biotic and biophysical variations act to modulate the role of regional climate in limiting/facilitating tree population growth at treelines. Bioclimatic models that incorporate both the climatic and biotic factors limiting tree establishment are likely to improve predictions of future biogeographic distributions of treeline species. Managers use bioclimatic models in decision making, but frequently these models ignore issues of climatic variability or biophysical interactions that can mitigate or amplify the climatic forcings on treelines.

This project investigates the role of climate in treeline establishment over the last century in 9 mountain ranges in the western U.S. We are sampling treeline establishment along natural gradients of climatic variability and continentality between the maritime northwest and the continental central Rocky mountains. We are also monitoring air and surface temperature and snowpack duration at treeline to better understand the site climatic conditions associated with treeline.


University of Arizona, Idaho State University

Primary Funding

US Department of Energy National Institute for Climate Change Research (NICCR)

Related Publications

For publications on climate impacts on PNW forest ecosystems, please see CIG Publications.