Douglas-fir Seed Source Movement Trial

View from a weather station at a research site on Lone Rock Timber Company property near Grants Pass, OR. Photo by Beth Roskilly.

Project Description

Climate change in the 21st century is likely to dramatically alter the growing conditions for Pacific Northwest trees. How trees respond to climate stress is determined in large part by their genetic composition and diversity. To understand how climate change will affect trees and forests, we need research on how climate variation impacts tree functions, and how genetic variation mediates these impacts. This understanding will aid managers in developing strategies to make forested landscapes more resilient to climate change. For example, managers might want to understand how elevated temperature and drought stress will affect survival, growth, and performance of trees, and how these impacts vary among seed sources from different environments.

We are addressing these questions by conducting the Douglas-fir Seed-Source Movement trial (SSMT), an extensive experiment to study the effects of climate and genetics on coast Douglas-fir, a keystone tree critical to ecosystems and rural economies across the Pacific Northwest. We have collected seed from 60 seed sources across Washington, Oregon, and California, and planted trees from each seed source in nine climatically-divergent field sites. The study has created numerous opportunities to address issues of fundamental and applied significance.

Aerial image of a research site on Giustina Land & Timber property near Springfield, OR, captured with drone cameras in August 2024. Photo by Oren Nardi, UC Davis. 

Since 2008, Pacific Northwest (PNW) Research Station scientists have collected annual data on the performance of all these trees, including measurements of height and diameter growth, survival and phenology (the timing of vegetative and reproductive budburst). On-site weather stations record sub-hourly measurements of soil and air temperature, precipitation, and soil moisture. Electronic sensors and time-lapse cameras have allowed us to measure tree growth on daily to hourly scales, enabling detailed analyses of how fluctuations in the environment impact tree growth. Additional work has examined how specific traits help trees cope with environmental stresses like cold and drought, and how these traits vary genetically. Related studies have also examined gene expression across the course of a year, creating and 'atlas' of the timing of gene expression as related to season and adaptive trait variation.

The size and quality of this study has attracted researchers outside the PNW Research Station, including Oregon State University, the Evergreen State College and the University of British Columbia. These collaborations leverage investments in the Seed-Source Movement Trial to create new avenues of research that advance the station’s mission, including studies of wood traits and hydraulic functions, root growth dynamics, and leaf pathogens.

SSMT study design: Geographic distribution of 60 source populations and nine planting sites across Washington, Oregon, and northern California.